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comparison docs/MarkedUpDisassembly.rst @ 0:95c75e76d11b LLVM3.4

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LLVM 3.4
author Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
date Thu, 12 Dec 2013 13:56:28 +0900
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children 1172e4bd9c6f
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1 =======================================
2 LLVM's Optional Rich Disassembly Output
3 =======================================
4
5 .. contents::
6 :local:
7
8 Introduction
9 ============
10
11 LLVM's default disassembly output is raw text. To allow consumers more ability
12 to introspect the instructions' textual representation or to reformat for a more
13 user friendly display there is an optional rich disassembly output.
14
15 This optional output is sufficient to reference into individual portions of the
16 instruction text. This is intended for clients like disassemblers, list file
17 generators, and pretty-printers, which need more than the raw instructions and
18 the ability to print them.
19
20 To provide this functionality the assembly text is marked up with annotations.
21 The markup is simple enough in syntax to be robust even in the case of version
22 mismatches between consumers and producers. That is, the syntax generally does
23 not carry semantics beyond "this text has an annotation," so consumers can
24 simply ignore annotations they do not understand or do not care about.
25
26 After calling ``LLVMCreateDisasm()`` to create a disassembler context the
27 optional output is enable with this call:
28
29 .. code-block:: c
30
31 LLVMSetDisasmOptions(DC, LLVMDisassembler_Option_UseMarkup);
32
33 Then subsequent calls to ``LLVMDisasmInstruction()`` will return output strings
34 with the marked up annotations.
35
36 Instruction Annotations
37 =======================
38
39 .. _contextual markups:
40
41 Contextual markups
42 ------------------
43
44 Annoated assembly display will supply contextual markup to help clients more
45 efficiently implement things like pretty printers. Most markup will be target
46 independent, so clients can effectively provide good display without any target
47 specific knowledge.
48
49 Annotated assembly goes through the normal instruction printer, but optionally
50 includes contextual tags on portions of the instruction string. An annotation
51 is any '<' '>' delimited section of text(1).
52
53 .. code-block:: bat
54
55 annotation: '<' tag-name tag-modifier-list ':' annotated-text '>'
56 tag-name: identifier
57 tag-modifier-list: comma delimited identifier list
58
59 The tag-name is an identifier which gives the type of the annotation. For the
60 first pass, this will be very simple, with memory references, registers, and
61 immediates having the tag names "mem", "reg", and "imm", respectively.
62
63 The tag-modifier-list is typically additional target-specific context, such as
64 register class.
65
66 Clients should accept and ignore any tag-names or tag-modifiers they do not
67 understand, allowing the annotations to grow in richness without breaking older
68 clients.
69
70 For example, a possible annotation of an ARM load of a stack-relative location
71 might be annotated as:
72
73 .. code-block:: nasm
74
75 ldr <reg gpr:r0>, <mem regoffset:[<reg gpr:sp>, <imm:#4>]>
76
77
78 1: For assembly dialects in which '<' and/or '>' are legal tokens, a literal token is escaped by following immediately with a repeat of the character. For example, a literal '<' character is output as '<<' in an annotated assembly string.
79
80 C API Details
81 -------------
82
83 The intended consumers of this information use the C API, therefore the new C
84 API function for the disassembler will be added to provide an option to produce
85 disassembled instructions with annotations, ``LLVMSetDisasmOptions()`` and the
86 ``LLVMDisassembler_Option_UseMarkup`` option (see above).