CbC/CbC_llvm: docs/tutorial/LangImpl5.rst annotate

annotate docs/tutorial/LangImpl5.rst @ 65:35ab9e3560be

remove null pointer access bug which occured if the callee codesegment is accessed by pointer on LowerCallTo().

author	Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
date	Tue, 11 Feb 2014 02:09:46 +0900
parents	95c75e76d11b
children	60c9769439b8

rev	line source
0 95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	1 ==================================================
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	2 Kaleidoscope: Extending the Language: Control Flow
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	3 ==================================================
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	4
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	5 .. contents::
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	6 :local:
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	7
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	8 Chapter 5 Introduction
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	9 ======================
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	10
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	11 Welcome to Chapter 5 of the "`Implementing a language with
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	12 LLVM <index.html>`_" tutorial. Parts 1-4 described the implementation of
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	13 the simple Kaleidoscope language and included support for generating
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	14 LLVM IR, followed by optimizations and a JIT compiler. Unfortunately, as
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	15 presented, Kaleidoscope is mostly useless: it has no control flow other
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	16 than call and return. This means that you can't have conditional
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	17 branches in the code, significantly limiting its power. In this episode
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	18 of "build that compiler", we'll extend Kaleidoscope to have an
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	19 if/then/else expression plus a simple 'for' loop.
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	20
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	21 If/Then/Else
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	22 ============
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	23
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	24 Extending Kaleidoscope to support if/then/else is quite straightforward.
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	25 It basically requires adding support for this "new" concept to the
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	26 lexer, parser, AST, and LLVM code emitter. This example is nice, because
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	27 it shows how easy it is to "grow" a language over time, incrementally
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	28 extending it as new ideas are discovered.
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	29
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	30 Before we get going on "how" we add this extension, lets talk about
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	31 "what" we want. The basic idea is that we want to be able to write this
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	32 sort of thing:
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	33
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	34 ::
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	35
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	36 def fib(x)
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	37 if x < 3 then
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	38 1
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	39 else
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	40 fib(x-1)+fib(x-2);
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	41
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	42 In Kaleidoscope, every construct is an expression: there are no
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	43 statements. As such, the if/then/else expression needs to return a value
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	44 like any other. Since we're using a mostly functional form, we'll have
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	45 it evaluate its conditional, then return the 'then' or 'else' value
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	46 based on how the condition was resolved. This is very similar to the C
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	47 "?:" expression.
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	48
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	49 The semantics of the if/then/else expression is that it evaluates the
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	50 condition to a boolean equality value: 0.0 is considered to be false and
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	51 everything else is considered to be true. If the condition is true, the
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	52 first subexpression is evaluated and returned, if the condition is
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	53 false, the second subexpression is evaluated and returned. Since
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	54 Kaleidoscope allows side-effects, this behavior is important to nail
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	55 down.
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	56
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	57 Now that we know what we "want", lets break this down into its
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	58 constituent pieces.
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	59
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	60 Lexer Extensions for If/Then/Else
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	61 ---------------------------------
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	62
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	63 The lexer extensions are straightforward. First we add new enum values
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	64 for the relevant tokens:
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	65
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	66 .. code-block:: c++
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	67
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	68 // control
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	69 tok_if = -6, tok_then = -7, tok_else = -8,
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	70
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	71 Once we have that, we recognize the new keywords in the lexer. This is
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	72 pretty simple stuff:
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	73
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	74 .. code-block:: c++
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	75
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	76 ...
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	77 if (IdentifierStr == "def") return tok_def;
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	78 if (IdentifierStr == "extern") return tok_extern;
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	79 if (IdentifierStr == "if") return tok_if;
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	80 if (IdentifierStr == "then") return tok_then;
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	81 if (IdentifierStr == "else") return tok_else;
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	82 return tok_identifier;
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	83
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	84 AST Extensions for If/Then/Else
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	85 -------------------------------
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	86
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	87 To represent the new expression we add a new AST node for it:
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	88
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	89 .. code-block:: c++
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	90
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	91 /// IfExprAST - Expression class for if/then/else.
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	92 class IfExprAST : public ExprAST {
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	93 ExprAST Cond, Then, *Else;
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	94 public:
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	95 IfExprAST(ExprAST cond, ExprAST then, ExprAST *_else)
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	96 : Cond(cond), Then(then), Else(_else) {}
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	97 virtual Value *Codegen();
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	98 };
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	99
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	100 The AST node just has pointers to the various subexpressions.
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	101
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	102 Parser Extensions for If/Then/Else
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	103 ----------------------------------
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	104
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	105 Now that we have the relevant tokens coming from the lexer and we have
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	106 the AST node to build, our parsing logic is relatively straightforward.
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	107 First we define a new parsing function:
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	108
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	109 .. code-block:: c++
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	110
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	111 /// ifexpr ::= 'if' expression 'then' expression 'else' expression
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	112 static ExprAST *ParseIfExpr() {
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	113 getNextToken(); // eat the if.
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	114
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	115 // condition.
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	116 ExprAST *Cond = ParseExpression();
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	117 if (!Cond) return 0;
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	118
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	119 if (CurTok != tok_then)
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	120 return Error("expected then");
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	121 getNextToken(); // eat the then
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	122
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	123 ExprAST *Then = ParseExpression();
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	124 if (Then == 0) return 0;
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	125
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	126 if (CurTok != tok_else)
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	127 return Error("expected else");
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	128
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	129 getNextToken();
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	130
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	131 ExprAST *Else = ParseExpression();
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	132 if (!Else) return 0;
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	133
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	134 return new IfExprAST(Cond, Then, Else);
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	135 }
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	136
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	137 Next we hook it up as a primary expression:
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	138
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	139 .. code-block:: c++
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	140
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	141 static ExprAST *ParsePrimary() {
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	142 switch (CurTok) {
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	143 default: return Error("unknown token when expecting an expression");
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	144 case tok_identifier: return ParseIdentifierExpr();
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	145 case tok_number: return ParseNumberExpr();
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	146 case '(': return ParseParenExpr();
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	147 case tok_if: return ParseIfExpr();
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	148 }
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	149 }
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	150
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	151 LLVM IR for If/Then/Else
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	152 ------------------------
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	153
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	154 Now that we have it parsing and building the AST, the final piece is
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	155 adding LLVM code generation support. This is the most interesting part
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	156 of the if/then/else example, because this is where it starts to
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	157 introduce new concepts. All of the code above has been thoroughly
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	158 described in previous chapters.
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	159
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	160 To motivate the code we want to produce, lets take a look at a simple
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	161 example. Consider:
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	162
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	163 ::
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	164
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	165 extern foo();
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	166 extern bar();
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	167 def baz(x) if x then foo() else bar();
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	168
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	169 If you disable optimizations, the code you'll (soon) get from
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	170 Kaleidoscope looks like this:
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	171
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	172 .. code-block:: llvm
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	173
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	174 declare double @foo()
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	175
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	176 declare double @bar()
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	177
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	178 define double @baz(double %x) {
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	179 entry:
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	180 %ifcond = fcmp one double %x, 0.000000e+00
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	181 br i1 %ifcond, label %then, label %else
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	182
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	183 then: ; preds = %entry
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	184 %calltmp = call double @foo()
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	185 br label %ifcont
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	186
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	187 else: ; preds = %entry
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	188 %calltmp1 = call double @bar()
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	189 br label %ifcont
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	190
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	191 ifcont: ; preds = %else, %then
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	192 %iftmp = phi double [ %calltmp, %then ], [ %calltmp1, %else ]
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	193 ret double %iftmp
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	194 }
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	195
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	196 To visualize the control flow graph, you can use a nifty feature of the
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	197 LLVM '`opt <http://llvm.org/cmds/opt.html>`_' tool. If you put this LLVM
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	198 IR into "t.ll" and run "``llvm-as < t.ll \| opt -analyze -view-cfg``", `a
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	199 window will pop up <../ProgrammersManual.html#ViewGraph>`_ and you'll
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	200 see this graph:
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	201
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	202 .. figure:: LangImpl5-cfg.png
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	203 :align: center
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	204 :alt: Example CFG
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	205
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	206 Example CFG
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	207
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	208 Another way to get this is to call "``F->viewCFG()``" or
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	209 "``F->viewCFGOnly()``" (where F is a "``Function*``") either by
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	210 inserting actual calls into the code and recompiling or by calling these
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	211 in the debugger. LLVM has many nice features for visualizing various
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	212 graphs.
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	213
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	214 Getting back to the generated code, it is fairly simple: the entry block
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	215 evaluates the conditional expression ("x" in our case here) and compares
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	216 the result to 0.0 with the "``fcmp one``" instruction ('one' is "Ordered
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	217 and Not Equal"). Based on the result of this expression, the code jumps
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	218 to either the "then" or "else" blocks, which contain the expressions for
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	219 the true/false cases.
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	220
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	221 Once the then/else blocks are finished executing, they both branch back
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	222 to the 'ifcont' block to execute the code that happens after the
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	223 if/then/else. In this case the only thing left to do is to return to the
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	224 caller of the function. The question then becomes: how does the code
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	225 know which expression to return?
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	226
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	227 The answer to this question involves an important SSA operation: the
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	228 `Phi
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	229 operation <http://en.wikipedia.org/wiki/Static_single_assignment_form>`_.
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	230 If you're not familiar with SSA, `the wikipedia
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	231 article <http://en.wikipedia.org/wiki/Static_single_assignment_form>`_
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	232 is a good introduction and there are various other introductions to it
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	233 available on your favorite search engine. The short version is that
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	234 "execution" of the Phi operation requires "remembering" which block
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	235 control came from. The Phi operation takes on the value corresponding to
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	236 the input control block. In this case, if control comes in from the
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	237 "then" block, it gets the value of "calltmp". If control comes from the
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	238 "else" block, it gets the value of "calltmp1".
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	239
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	240 At this point, you are probably starting to think "Oh no! This means my
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	241 simple and elegant front-end will have to start generating SSA form in
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	242 order to use LLVM!". Fortunately, this is not the case, and we strongly
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	243 advise not implementing an SSA construction algorithm in your
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	244 front-end unless there is an amazingly good reason to do so. In
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	245 practice, there are two sorts of values that float around in code
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	246 written for your average imperative programming language that might need
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	247 Phi nodes:
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	248
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	249 #. Code that involves user variables: ``x = 1; x = x + 1;``
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	250 #. Values that are implicit in the structure of your AST, such as the
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	251 Phi node in this case.
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	252
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	253 In `Chapter 7 <LangImpl7.html>`_ of this tutorial ("mutable variables"),
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	254 we'll talk about #1 in depth. For now, just believe me that you don't
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	255 need SSA construction to handle this case. For #2, you have the choice
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	256 of using the techniques that we will describe for #1, or you can insert
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	257 Phi nodes directly, if convenient. In this case, it is really really
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	258 easy to generate the Phi node, so we choose to do it directly.
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	259
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	260 Okay, enough of the motivation and overview, lets generate code!
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	261
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	262 Code Generation for If/Then/Else
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	263 --------------------------------
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	264
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	265 In order to generate code for this, we implement the ``Codegen`` method
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	266 for ``IfExprAST``:
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	267
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	268 .. code-block:: c++
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	269
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	270 Value *IfExprAST::Codegen() {
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	271 Value *CondV = Cond->Codegen();
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	272 if (CondV == 0) return 0;
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	273
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	274 // Convert condition to a bool by comparing equal to 0.0.
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	275 CondV = Builder.CreateFCmpONE(CondV,
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	276 ConstantFP::get(getGlobalContext(), APFloat(0.0)),
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	277 "ifcond");
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	278
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	279 This code is straightforward and similar to what we saw before. We emit
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	280 the expression for the condition, then compare that value to zero to get
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	281 a truth value as a 1-bit (bool) value.
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	282
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	283 .. code-block:: c++
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	284
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	285 Function *TheFunction = Builder.GetInsertBlock()->getParent();
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	286
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	287 // Create blocks for the then and else cases. Insert the 'then' block at the
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	288 // end of the function.
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	289 BasicBlock *ThenBB = BasicBlock::Create(getGlobalContext(), "then", TheFunction);
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	290 BasicBlock *ElseBB = BasicBlock::Create(getGlobalContext(), "else");
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	291 BasicBlock *MergeBB = BasicBlock::Create(getGlobalContext(), "ifcont");
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	292
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	293 Builder.CreateCondBr(CondV, ThenBB, ElseBB);
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	294
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	295 This code creates the basic blocks that are related to the if/then/else
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	296 statement, and correspond directly to the blocks in the example above.
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	297 The first line gets the current Function object that is being built. It
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	298 gets this by asking the builder for the current BasicBlock, and asking
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	299 that block for its "parent" (the function it is currently embedded
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	300 into).
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	301
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	302 Once it has that, it creates three blocks. Note that it passes
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	303 "TheFunction" into the constructor for the "then" block. This causes the
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	304 constructor to automatically insert the new block into the end of the
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	305 specified function. The other two blocks are created, but aren't yet
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	306 inserted into the function.
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	307
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	308 Once the blocks are created, we can emit the conditional branch that
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	309 chooses between them. Note that creating new blocks does not implicitly
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	310 affect the IRBuilder, so it is still inserting into the block that the
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	311 condition went into. Also note that it is creating a branch to the
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	312 "then" block and the "else" block, even though the "else" block isn't
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	313 inserted into the function yet. This is all ok: it is the standard way
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	314 that LLVM supports forward references.
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	315
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	316 .. code-block:: c++
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	317
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	318 // Emit then value.
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	319 Builder.SetInsertPoint(ThenBB);
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	320
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	321 Value *ThenV = Then->Codegen();
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	322 if (ThenV == 0) return 0;
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	323
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	324 Builder.CreateBr(MergeBB);
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	325 // Codegen of 'Then' can change the current block, update ThenBB for the PHI.
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	326 ThenBB = Builder.GetInsertBlock();
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	327
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	328 After the conditional branch is inserted, we move the builder to start
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	329 inserting into the "then" block. Strictly speaking, this call moves the
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	330 insertion point to be at the end of the specified block. However, since
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	331 the "then" block is empty, it also starts out by inserting at the
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	332 beginning of the block. :)
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	333
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	334 Once the insertion point is set, we recursively codegen the "then"
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	335 expression from the AST. To finish off the "then" block, we create an
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	336 unconditional branch to the merge block. One interesting (and very
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	337 important) aspect of the LLVM IR is that it `requires all basic blocks
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	338 to be "terminated" <../LangRef.html#functionstructure>`_ with a `control
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	339 flow instruction <../LangRef.html#terminators>`_ such as return or
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	340 branch. This means that all control flow, including fall throughs must
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	341 be made explicit in the LLVM IR. If you violate this rule, the verifier
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	342 will emit an error.
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	343
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	344 The final line here is quite subtle, but is very important. The basic
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	345 issue is that when we create the Phi node in the merge block, we need to
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	346 set up the block/value pairs that indicate how the Phi will work.
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	347 Importantly, the Phi node expects to have an entry for each predecessor
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	348 of the block in the CFG. Why then, are we getting the current block when
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	349 we just set it to ThenBB 5 lines above? The problem is that the "Then"
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	350 expression may actually itself change the block that the Builder is
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	351 emitting into if, for example, it contains a nested "if/then/else"
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	352 expression. Because calling Codegen recursively could arbitrarily change
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	353 the notion of the current block, we are required to get an up-to-date
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	354 value for code that will set up the Phi node.
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	355
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	356 .. code-block:: c++
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	357
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	358 // Emit else block.
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	359 TheFunction->getBasicBlockList().push_back(ElseBB);
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	360 Builder.SetInsertPoint(ElseBB);
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	361
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	362 Value *ElseV = Else->Codegen();
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	363 if (ElseV == 0) return 0;
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	364
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	365 Builder.CreateBr(MergeBB);
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	366 // Codegen of 'Else' can change the current block, update ElseBB for the PHI.
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	367 ElseBB = Builder.GetInsertBlock();
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	368
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	369 Code generation for the 'else' block is basically identical to codegen
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	370 for the 'then' block. The only significant difference is the first line,
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	371 which adds the 'else' block to the function. Recall previously that the
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	372 'else' block was created, but not added to the function. Now that the
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	373 'then' and 'else' blocks are emitted, we can finish up with the merge
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	374 code:
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	375
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	376 .. code-block:: c++
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	377
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	378 // Emit merge block.
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	379 TheFunction->getBasicBlockList().push_back(MergeBB);
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	380 Builder.SetInsertPoint(MergeBB);
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	381 PHINode *PN = Builder.CreatePHI(Type::getDoubleTy(getGlobalContext()), 2,
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	382 "iftmp");
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	383
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	384 PN->addIncoming(ThenV, ThenBB);
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	385 PN->addIncoming(ElseV, ElseBB);
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	386 return PN;
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	387 }
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	388
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	389 The first two lines here are now familiar: the first adds the "merge"
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	390 block to the Function object (it was previously floating, like the else
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	391 block above). The second block changes the insertion point so that newly
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	392 created code will go into the "merge" block. Once that is done, we need
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	393 to create the PHI node and set up the block/value pairs for the PHI.
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	394
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	395 Finally, the CodeGen function returns the phi node as the value computed
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	396 by the if/then/else expression. In our example above, this returned
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	397 value will feed into the code for the top-level function, which will
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	398 create the return instruction.
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	399
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	400 Overall, we now have the ability to execute conditional code in
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	401 Kaleidoscope. With this extension, Kaleidoscope is a fairly complete
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	402 language that can calculate a wide variety of numeric functions. Next up
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	403 we'll add another useful expression that is familiar from non-functional
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	404 languages...
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	405
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	406 'for' Loop Expression
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	407 =====================
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	408
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	409 Now that we know how to add basic control flow constructs to the
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	410 language, we have the tools to add more powerful things. Lets add
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	411 something more aggressive, a 'for' expression:
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	412
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	413 ::
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	414
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	415 extern putchard(char)
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	416 def printstar(n)
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	417 for i = 1, i < n, 1.0 in
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	418 putchard(42); # ascii 42 = '*'
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	419
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	420 # print 100 '*' characters
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	421 printstar(100);
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	422
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	423 This expression defines a new variable ("i" in this case) which iterates
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	424 from a starting value, while the condition ("i < n" in this case) is
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	425 true, incrementing by an optional step value ("1.0" in this case). If
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	426 the step value is omitted, it defaults to 1.0. While the loop is true,
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	427 it executes its body expression. Because we don't have anything better
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	428 to return, we'll just define the loop as always returning 0.0. In the
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	429 future when we have mutable variables, it will get more useful.
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	430
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	431 As before, lets talk about the changes that we need to Kaleidoscope to
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	432 support this.
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	433
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	434 Lexer Extensions for the 'for' Loop
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	435 -----------------------------------
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	436
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	437 The lexer extensions are the same sort of thing as for if/then/else:
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	438
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	439 .. code-block:: c++
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	440
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	441 ... in enum Token ...
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	442 // control
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	443 tok_if = -6, tok_then = -7, tok_else = -8,
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	444 tok_for = -9, tok_in = -10
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	445
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	446 ... in gettok ...
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	447 if (IdentifierStr == "def") return tok_def;
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	448 if (IdentifierStr == "extern") return tok_extern;
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	449 if (IdentifierStr == "if") return tok_if;
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	450 if (IdentifierStr == "then") return tok_then;
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	451 if (IdentifierStr == "else") return tok_else;
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	452 if (IdentifierStr == "for") return tok_for;
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	453 if (IdentifierStr == "in") return tok_in;
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	454 return tok_identifier;
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	455
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	456 AST Extensions for the 'for' Loop
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	457 ---------------------------------
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	458
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	459 The AST node is just as simple. It basically boils down to capturing the
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	460 variable name and the constituent expressions in the node.
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	461
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	462 .. code-block:: c++
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	463
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	464 /// ForExprAST - Expression class for for/in.
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	465 class ForExprAST : public ExprAST {
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	466 std::string VarName;
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	467 ExprAST Start, End, Step, Body;
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	468 public:
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	469 ForExprAST(const std::string &varname, ExprAST start, ExprAST end,
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	470 ExprAST step, ExprAST body)
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	471 : VarName(varname), Start(start), End(end), Step(step), Body(body) {}
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	472 virtual Value *Codegen();
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	473 };
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	474
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	475 Parser Extensions for the 'for' Loop
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	476 ------------------------------------
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	477
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	478 The parser code is also fairly standard. The only interesting thing here
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	479 is handling of the optional step value. The parser code handles it by
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	480 checking to see if the second comma is present. If not, it sets the step
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	481 value to null in the AST node:
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	482
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	483 .. code-block:: c++
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	484
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	485 /// forexpr ::= 'for' identifier '=' expr ',' expr (',' expr)? 'in' expression
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	486 static ExprAST *ParseForExpr() {
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	487 getNextToken(); // eat the for.
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	488
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	489 if (CurTok != tok_identifier)
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	490 return Error("expected identifier after for");
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	491
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	492 std::string IdName = IdentifierStr;
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	493 getNextToken(); // eat identifier.
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	494
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	495 if (CurTok != '=')
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	496 return Error("expected '=' after for");
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	497 getNextToken(); // eat '='.
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	498
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	499
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	500 ExprAST *Start = ParseExpression();
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	501 if (Start == 0) return 0;
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	502 if (CurTok != ',')
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	503 return Error("expected ',' after for start value");
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	504 getNextToken();
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	505
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	506 ExprAST *End = ParseExpression();
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	507 if (End == 0) return 0;
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	508
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	509 // The step value is optional.
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	510 ExprAST *Step = 0;
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	511 if (CurTok == ',') {
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	512 getNextToken();
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	513 Step = ParseExpression();
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	514 if (Step == 0) return 0;
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	515 }
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	516
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	517 if (CurTok != tok_in)
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	518 return Error("expected 'in' after for");
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	519 getNextToken(); // eat 'in'.
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	520
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	521 ExprAST *Body = ParseExpression();
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	522 if (Body == 0) return 0;
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	523
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	524 return new ForExprAST(IdName, Start, End, Step, Body);
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	525 }
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	526
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	527 LLVM IR for the 'for' Loop
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	528 --------------------------
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	529
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	530 Now we get to the good part: the LLVM IR we want to generate for this
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	531 thing. With the simple example above, we get this LLVM IR (note that
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	532 this dump is generated with optimizations disabled for clarity):
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	533
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	534 .. code-block:: llvm
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	535
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	536 declare double @putchard(double)
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	537
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	538 define double @printstar(double %n) {
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	539 entry:
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	540 ; initial value = 1.0 (inlined into phi)
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	541 br label %loop
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	542
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	543 loop: ; preds = %loop, %entry
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	544 %i = phi double [ 1.000000e+00, %entry ], [ %nextvar, %loop ]
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	545 ; body
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	546 %calltmp = call double @putchard(double 4.200000e+01)
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	547 ; increment
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	548 %nextvar = fadd double %i, 1.000000e+00
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	549
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	550 ; termination test
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	551 %cmptmp = fcmp ult double %i, %n
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	552 %booltmp = uitofp i1 %cmptmp to double
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	553 %loopcond = fcmp one double %booltmp, 0.000000e+00
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	554 br i1 %loopcond, label %loop, label %afterloop
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	555
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	556 afterloop: ; preds = %loop
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	557 ; loop always returns 0.0
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	558 ret double 0.000000e+00
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	559 }
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	560
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	561 This loop contains all the same constructs we saw before: a phi node,
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	562 several expressions, and some basic blocks. Lets see how this fits
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	563 together.
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	564
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	565 Code Generation for the 'for' Loop
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	566 ----------------------------------
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	567
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	568 The first part of Codegen is very simple: we just output the start
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	569 expression for the loop value:
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	570
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	571 .. code-block:: c++
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	572
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	573 Value *ForExprAST::Codegen() {
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	574 // Emit the start code first, without 'variable' in scope.
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	575 Value *StartVal = Start->Codegen();
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	576 if (StartVal == 0) return 0;
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	577
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	578 With this out of the way, the next step is to set up the LLVM basic
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	579 block for the start of the loop body. In the case above, the whole loop
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	580 body is one block, but remember that the body code itself could consist
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	581 of multiple blocks (e.g. if it contains an if/then/else or a for/in
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	582 expression).
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	583
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	584 .. code-block:: c++
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	585
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	586 // Make the new basic block for the loop header, inserting after current
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	587 // block.
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	588 Function *TheFunction = Builder.GetInsertBlock()->getParent();
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	589 BasicBlock *PreheaderBB = Builder.GetInsertBlock();
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	590 BasicBlock *LoopBB = BasicBlock::Create(getGlobalContext(), "loop", TheFunction);
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	591
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	592 // Insert an explicit fall through from the current block to the LoopBB.
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	593 Builder.CreateBr(LoopBB);
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	594
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	595 This code is similar to what we saw for if/then/else. Because we will
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	596 need it to create the Phi node, we remember the block that falls through
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	597 into the loop. Once we have that, we create the actual block that starts
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	598 the loop and create an unconditional branch for the fall-through between
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	599 the two blocks.
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	600
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	601 .. code-block:: c++
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	602
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	603 // Start insertion in LoopBB.
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	604 Builder.SetInsertPoint(LoopBB);
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	605
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	606 // Start the PHI node with an entry for Start.
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	607 PHINode *Variable = Builder.CreatePHI(Type::getDoubleTy(getGlobalContext()), 2, VarName.c_str());
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	608 Variable->addIncoming(StartVal, PreheaderBB);
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	609
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	610 Now that the "preheader" for the loop is set up, we switch to emitting
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	611 code for the loop body. To begin with, we move the insertion point and
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	612 create the PHI node for the loop induction variable. Since we already
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	613 know the incoming value for the starting value, we add it to the Phi
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	614 node. Note that the Phi will eventually get a second value for the
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	615 backedge, but we can't set it up yet (because it doesn't exist!).
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	616
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	617 .. code-block:: c++
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	618
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	619 // Within the loop, the variable is defined equal to the PHI node. If it
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	620 // shadows an existing variable, we have to restore it, so save it now.
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	621 Value *OldVal = NamedValues[VarName];
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	622 NamedValues[VarName] = Variable;
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	623
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	624 // Emit the body of the loop. This, like any other expr, can change the
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	625 // current BB. Note that we ignore the value computed by the body, but don't
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	626 // allow an error.
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	627 if (Body->Codegen() == 0)
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	628 return 0;
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	629
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	630 Now the code starts to get more interesting. Our 'for' loop introduces a
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	631 new variable to the symbol table. This means that our symbol table can
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	632 now contain either function arguments or loop variables. To handle this,
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	633 before we codegen the body of the loop, we add the loop variable as the
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	634 current value for its name. Note that it is possible that there is a
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	635 variable of the same name in the outer scope. It would be easy to make
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	636 this an error (emit an error and return null if there is already an
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	637 entry for VarName) but we choose to allow shadowing of variables. In
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	638 order to handle this correctly, we remember the Value that we are
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	639 potentially shadowing in ``OldVal`` (which will be null if there is no
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	640 shadowed variable).
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	641
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	642 Once the loop variable is set into the symbol table, the code
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	643 recursively codegen's the body. This allows the body to use the loop
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	644 variable: any references to it will naturally find it in the symbol
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	645 table.
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	646
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	647 .. code-block:: c++
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	648
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	649 // Emit the step value.
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	650 Value *StepVal;
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	651 if (Step) {
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	652 StepVal = Step->Codegen();
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	653 if (StepVal == 0) return 0;
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	654 } else {
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	655 // If not specified, use 1.0.
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	656 StepVal = ConstantFP::get(getGlobalContext(), APFloat(1.0));
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	657 }
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	658
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	659 Value *NextVar = Builder.CreateFAdd(Variable, StepVal, "nextvar");
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	660
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	661 Now that the body is emitted, we compute the next value of the iteration
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	662 variable by adding the step value, or 1.0 if it isn't present.
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	663 '``NextVar``' will be the value of the loop variable on the next
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	664 iteration of the loop.
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	665
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	666 .. code-block:: c++
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	667
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	668 // Compute the end condition.
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	669 Value *EndCond = End->Codegen();
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	670 if (EndCond == 0) return EndCond;
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	671
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	672 // Convert condition to a bool by comparing equal to 0.0.
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	673 EndCond = Builder.CreateFCmpONE(EndCond,
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	674 ConstantFP::get(getGlobalContext(), APFloat(0.0)),
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	675 "loopcond");
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	676
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	677 Finally, we evaluate the exit value of the loop, to determine whether
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	678 the loop should exit. This mirrors the condition evaluation for the
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	679 if/then/else statement.
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	680
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	681 .. code-block:: c++
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	682
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	683 // Create the "after loop" block and insert it.
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	684 BasicBlock *LoopEndBB = Builder.GetInsertBlock();
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	685 BasicBlock *AfterBB = BasicBlock::Create(getGlobalContext(), "afterloop", TheFunction);
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	686
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	687 // Insert the conditional branch into the end of LoopEndBB.
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	688 Builder.CreateCondBr(EndCond, LoopBB, AfterBB);
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	689
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	690 // Any new code will be inserted in AfterBB.
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	691 Builder.SetInsertPoint(AfterBB);
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	692
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	693 With the code for the body of the loop complete, we just need to finish
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	694 up the control flow for it. This code remembers the end block (for the
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	695 phi node), then creates the block for the loop exit ("afterloop"). Based
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	696 on the value of the exit condition, it creates a conditional branch that
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	697 chooses between executing the loop again and exiting the loop. Any
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	698 future code is emitted in the "afterloop" block, so it sets the
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	699 insertion position to it.
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	700
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	701 .. code-block:: c++
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	702
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	703 // Add a new entry to the PHI node for the backedge.
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	704 Variable->addIncoming(NextVar, LoopEndBB);
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	705
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	706 // Restore the unshadowed variable.
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	707 if (OldVal)
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	708 NamedValues[VarName] = OldVal;
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	709 else
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	710 NamedValues.erase(VarName);
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	711
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	712 // for expr always returns 0.0.
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	713 return Constant::getNullValue(Type::getDoubleTy(getGlobalContext()));
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	714 }
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	715
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	716 The final code handles various cleanups: now that we have the "NextVar"
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	717 value, we can add the incoming value to the loop PHI node. After that,
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	718 we remove the loop variable from the symbol table, so that it isn't in
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	719 scope after the for loop. Finally, code generation of the for loop
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	720 always returns 0.0, so that is what we return from
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	721 ``ForExprAST::Codegen``.
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	722
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	723 With this, we conclude the "adding control flow to Kaleidoscope" chapter
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	724 of the tutorial. In this chapter we added two control flow constructs,
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	725 and used them to motivate a couple of aspects of the LLVM IR that are
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	726 important for front-end implementors to know. In the next chapter of our
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	727 saga, we will get a bit crazier and add `user-defined
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	728 operators <LangImpl6.html>`_ to our poor innocent language.
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	729
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	730 Full Code Listing
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	731 =================
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	732
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	733 Here is the complete code listing for our running example, enhanced with
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	734 the if/then/else and for expressions.. To build this example, use:
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	735
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	736 .. code-block:: bash
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	737
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	738 # Compile
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	739 clang++ -g toy.cpp `llvm-config --cppflags --ldflags --libs core jit native` -O3 -o toy
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	740 # Run
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	741 ./toy
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	742
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	743 Here is the code:
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	744
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	745 .. literalinclude:: ../../examples/Kaleidoscope/Chapter5/toy.cpp
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	746 :language: c++
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	747
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	748 `Next: Extending the language: user-defined operators <LangImpl6.html>`_
95c75e76d11b LLVM 3.4 Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	749

Mercurial > hg > CbC > CbC_llvm

annotate docs/tutorial/LangImpl5.rst @ 65:35ab9e3560be