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author Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
date Sun, 31 Jan 2016 17:34:49 +0900
parents afa8332a0e37
children 1172e4bd9c6f
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1 ================================
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2 Frequently Asked Questions (FAQ)
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3 ================================
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4
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5 .. contents::
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6 :local:
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8
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9 License
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10 =======
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11
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12 Does the University of Illinois Open Source License really qualify as an "open source" license?
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13 -----------------------------------------------------------------------------------------------
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14 Yes, the license is `certified
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15 <http://www.opensource.org/licenses/UoI-NCSA.php>`_ by the Open Source
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16 Initiative (OSI).
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17
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18
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19 Can I modify LLVM source code and redistribute the modified source?
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20 -------------------------------------------------------------------
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21 Yes. The modified source distribution must retain the copyright notice and
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22 follow the three bulletted conditions listed in the `LLVM license
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23 <http://llvm.org/svn/llvm-project/llvm/trunk/LICENSE.TXT>`_.
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24
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25
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26 Can I modify the LLVM source code and redistribute binaries or other tools based on it, without redistributing the source?
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27 --------------------------------------------------------------------------------------------------------------------------
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28 Yes. This is why we distribute LLVM under a less restrictive license than GPL,
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29 as explained in the first question above.
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30
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31
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32 Source Code
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33 ===========
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34
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35 In what language is LLVM written?
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36 ---------------------------------
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37 All of the LLVM tools and libraries are written in C++ with extensive use of
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38 the STL.
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39
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40
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41 How portable is the LLVM source code?
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42 -------------------------------------
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43 The LLVM source code should be portable to most modern Unix-like operating
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44 systems. Most of the code is written in standard C++ with operating system
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45 services abstracted to a support library. The tools required to build and
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46 test LLVM have been ported to a plethora of platforms.
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47
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48 Some porting problems may exist in the following areas:
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49
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50 * The autoconf/makefile build system relies heavily on UNIX shell tools,
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51 like the Bourne Shell and sed. Porting to systems without these tools
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52 (MacOS 9, Plan 9) will require more effort.
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53
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54 What API do I use to store a value to one of the virtual registers in LLVM IR's SSA representation?
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55 ---------------------------------------------------------------------------------------------------
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56
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57 In short: you can't. It's actually kind of a silly question once you grok
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58 what's going on. Basically, in code like:
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59
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60 .. code-block:: llvm
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61
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62 %result = add i32 %foo, %bar
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63
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64 , ``%result`` is just a name given to the ``Value`` of the ``add``
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65 instruction. In other words, ``%result`` *is* the add instruction. The
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66 "assignment" doesn't explicitly "store" anything to any "virtual register";
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67 the "``=``" is more like the mathematical sense of equality.
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68
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69 Longer explanation: In order to generate a textual representation of the
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70 IR, some kind of name has to be given to each instruction so that other
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71 instructions can textually reference it. However, the isomorphic in-memory
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72 representation that you manipulate from C++ has no such restriction since
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73 instructions can simply keep pointers to any other ``Value``'s that they
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74 reference. In fact, the names of dummy numbered temporaries like ``%1`` are
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75 not explicitly represented in the in-memory representation at all (see
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76 ``Value::getName()``).
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77
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78 Build Problems
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79 ==============
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80
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81 When I run configure, it finds the wrong C compiler.
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82 ----------------------------------------------------
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83 The ``configure`` script attempts to locate first ``gcc`` and then ``cc``,
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84 unless it finds compiler paths set in ``CC`` and ``CXX`` for the C and C++
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85 compiler, respectively.
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86
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87 If ``configure`` finds the wrong compiler, either adjust your ``PATH``
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88 environment variable or set ``CC`` and ``CXX`` explicitly.
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89
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90
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91 The ``configure`` script finds the right C compiler, but it uses the LLVM tools from a previous build. What do I do?
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92 ---------------------------------------------------------------------------------------------------------------------
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93 The ``configure`` script uses the ``PATH`` to find executables, so if it's
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94 grabbing the wrong linker/assembler/etc, there are two ways to fix it:
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95
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96 #. Adjust your ``PATH`` environment variable so that the correct program
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97 appears first in the ``PATH``. This may work, but may not be convenient
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98 when you want them *first* in your path for other work.
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99
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100 #. Run ``configure`` with an alternative ``PATH`` that is correct. In a
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101 Bourne compatible shell, the syntax would be:
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102
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103 .. code-block:: console
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104
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105 % PATH=[the path without the bad program] $LLVM_SRC_DIR/configure ...
0
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106
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107 This is still somewhat inconvenient, but it allows ``configure`` to do its
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108 work without having to adjust your ``PATH`` permanently.
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109
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110
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111 When creating a dynamic library, I get a strange GLIBC error.
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112 -------------------------------------------------------------
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113 Under some operating systems (i.e. Linux), libtool does not work correctly if
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114 GCC was compiled with the ``--disable-shared option``. To work around this,
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115 install your own version of GCC that has shared libraries enabled by default.
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116
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117
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118 I've updated my source tree from Subversion, and now my build is trying to use a file/directory that doesn't exist.
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119 -------------------------------------------------------------------------------------------------------------------
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120 You need to re-run configure in your object directory. When new Makefiles
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121 are added to the source tree, they have to be copied over to the object tree
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122 in order to be used by the build.
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123
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124
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125 I've modified a Makefile in my source tree, but my build tree keeps using the old version. What do I do?
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126 ---------------------------------------------------------------------------------------------------------
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127 If the Makefile already exists in your object tree, you can just run the
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128 following command in the top level directory of your object tree:
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129
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130 .. code-block:: console
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131
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132 % ./config.status <relative path to Makefile>;
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133
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134 If the Makefile is new, you will have to modify the configure script to copy
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135 it over.
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136
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137
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138 I've upgraded to a new version of LLVM, and I get strange build errors.
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139 -----------------------------------------------------------------------
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140 Sometimes, changes to the LLVM source code alters how the build system works.
95c75e76d11b LLVM 3.4
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141 Changes in ``libtool``, ``autoconf``, or header file dependencies are
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142 especially prone to this sort of problem.
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143
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144 The best thing to try is to remove the old files and re-build. In most cases,
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145 this takes care of the problem. To do this, just type ``make clean`` and then
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146 ``make`` in the directory that fails to build.
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147
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148
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149 I've built LLVM and am testing it, but the tests freeze.
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150 --------------------------------------------------------
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151 This is most likely occurring because you built a profile or release
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152 (optimized) build of LLVM and have not specified the same information on the
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153 ``gmake`` command line.
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154
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155 For example, if you built LLVM with the command:
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156
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157 .. code-block:: console
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158
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159 % gmake ENABLE_PROFILING=1
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160
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161 ...then you must run the tests with the following commands:
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162
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163 .. code-block:: console
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164
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165 % cd llvm/test
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166 % gmake ENABLE_PROFILING=1
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167
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168 Why do test results differ when I perform different types of builds?
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169 --------------------------------------------------------------------
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170 The LLVM test suite is dependent upon several features of the LLVM tools and
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171 libraries.
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172
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173 First, the debugging assertions in code are not enabled in optimized or
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174 profiling builds. Hence, tests that used to fail may pass.
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175
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176 Second, some tests may rely upon debugging options or behavior that is only
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177 available in the debug build. These tests will fail in an optimized or
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178 profile build.
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179
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180
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181 Compiling LLVM with GCC 3.3.2 fails, what should I do?
95c75e76d11b LLVM 3.4
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182 ------------------------------------------------------
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183 This is `a bug in GCC <http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13392>`_,
95c75e76d11b LLVM 3.4
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184 and affects projects other than LLVM. Try upgrading or downgrading your GCC.
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185
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186
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187 After Subversion update, rebuilding gives the error "No rule to make target".
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188 -----------------------------------------------------------------------------
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189 If the error is of the form:
95c75e76d11b LLVM 3.4
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190
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191 .. code-block:: console
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192
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193 gmake[2]: *** No rule to make target `/path/to/somefile',
95c75e76d11b LLVM 3.4
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parents:
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194 needed by `/path/to/another/file.d'.
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
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195 Stop.
95c75e76d11b LLVM 3.4
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196
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197 This may occur anytime files are moved within the Subversion repository or
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198 removed entirely. In this case, the best solution is to erase all ``.d``
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199 files, which list dependencies for source files, and rebuild:
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200
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201 .. code-block:: console
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202
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203 % cd $LLVM_OBJ_DIR
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204 % rm -f `find . -name \*\.d`
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205 % gmake
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206
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207 In other cases, it may be necessary to run ``make clean`` before rebuilding.
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208
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209
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210 Source Languages
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211 ================
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212
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213 What source languages are supported?
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214 ------------------------------------
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215 LLVM currently has full support for C and C++ source languages. These are
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parents:
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216 available through both `Clang <http://clang.llvm.org/>`_ and `DragonEgg
95c75e76d11b LLVM 3.4
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parents:
diff changeset
217 <http://dragonegg.llvm.org/>`_.
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218
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219 The PyPy developers are working on integrating LLVM into the PyPy backend so
95c75e76d11b LLVM 3.4
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parents:
diff changeset
220 that PyPy language can translate to LLVM.
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parents:
diff changeset
221
95c75e76d11b LLVM 3.4
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diff changeset
222
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parents:
diff changeset
223 I'd like to write a self-hosting LLVM compiler. How should I interface with the LLVM middle-end optimizers and back-end code generators?
95c75e76d11b LLVM 3.4
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224 ----------------------------------------------------------------------------------------------------------------------------------------
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225 Your compiler front-end will communicate with LLVM by creating a module in the
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parents:
diff changeset
226 LLVM intermediate representation (IR) format. Assuming you want to write your
95c75e76d11b LLVM 3.4
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parents:
diff changeset
227 language's compiler in the language itself (rather than C++), there are 3
95c75e76d11b LLVM 3.4
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parents:
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228 major ways to tackle generating LLVM IR from a front-end:
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229
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230 1. **Call into the LLVM libraries code using your language's FFI (foreign
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
231 function interface).**
95c75e76d11b LLVM 3.4
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parents:
diff changeset
232
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233 * *for:* best tracks changes to the LLVM IR, .ll syntax, and .bc format
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parents:
diff changeset
234
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235 * *for:* enables running LLVM optimization passes without a emit/parse
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
236 overhead
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
237
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parents:
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238 * *for:* adapts well to a JIT context
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parents:
diff changeset
239
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
240 * *against:* lots of ugly glue code to write
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Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
241
95c75e76d11b LLVM 3.4
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parents:
diff changeset
242 2. **Emit LLVM assembly from your compiler's native language.**
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parents:
diff changeset
243
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
244 * *for:* very straightforward to get started
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
245
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
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246 * *against:* the .ll parser is slower than the bitcode reader when
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
247 interfacing to the middle end
95c75e76d11b LLVM 3.4
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parents:
diff changeset
248
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
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249 * *against:* it may be harder to track changes to the IR
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
250
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
251 3. **Emit LLVM bitcode from your compiler's native language.**
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parents:
diff changeset
252
95c75e76d11b LLVM 3.4
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parents:
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253 * *for:* can use the more-efficient bitcode reader when interfacing to the
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Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
254 middle end
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
255
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
256 * *against:* you'll have to re-engineer the LLVM IR object model and bitcode
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
257 writer in your language
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
258
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
259 * *against:* it may be harder to track changes to the IR
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
260
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Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
261 If you go with the first option, the C bindings in include/llvm-c should help
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
262 a lot, since most languages have strong support for interfacing with C. The
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
263 most common hurdle with calling C from managed code is interfacing with the
95c75e76d11b LLVM 3.4
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parents:
diff changeset
264 garbage collector. The C interface was designed to require very little memory
95c75e76d11b LLVM 3.4
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diff changeset
265 management, and so is straightforward in this regard.
95c75e76d11b LLVM 3.4
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266
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
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diff changeset
267 What support is there for a higher level source language constructs for building a compiler?
95c75e76d11b LLVM 3.4
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parents:
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268 --------------------------------------------------------------------------------------------
95c75e76d11b LLVM 3.4
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269 Currently, there isn't much. LLVM supports an intermediate representation
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
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270 which is useful for code representation but will not support the high level
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
271 (abstract syntax tree) representation needed by most compilers. There are no
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
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diff changeset
272 facilities for lexical nor semantic analysis.
95c75e76d11b LLVM 3.4
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273
95c75e76d11b LLVM 3.4
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274
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
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275 I don't understand the ``GetElementPtr`` instruction. Help!
95c75e76d11b LLVM 3.4
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parents:
diff changeset
276 -----------------------------------------------------------
95c75e76d11b LLVM 3.4
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diff changeset
277 See `The Often Misunderstood GEP Instruction <GetElementPtr.html>`_.
95c75e76d11b LLVM 3.4
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parents:
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278
95c75e76d11b LLVM 3.4
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279
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
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280 Using the C and C++ Front Ends
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
281 ==============================
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
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282
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
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283 Can I compile C or C++ code to platform-independent LLVM bitcode?
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
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284 -----------------------------------------------------------------
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
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285 No. C and C++ are inherently platform-dependent languages. The most obvious
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
286 example of this is the preprocessor. A very common way that C code is made
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
287 portable is by using the preprocessor to include platform-specific code. In
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
288 practice, information about other platforms is lost after preprocessing, so
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
289 the result is inherently dependent on the platform that the preprocessing was
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
290 targeting.
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
291
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
292 Another example is ``sizeof``. It's common for ``sizeof(long)`` to vary
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
293 between platforms. In most C front-ends, ``sizeof`` is expanded to a
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
294 constant immediately, thus hard-wiring a platform-specific detail.
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
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295
95c75e76d11b LLVM 3.4
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parents:
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296 Also, since many platforms define their ABIs in terms of C, and since LLVM is
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
297 lower-level than C, front-ends currently must emit platform-specific IR in
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
298 order to have the result conform to the platform ABI.
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
299
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
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300
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
301 Questions about code generated by the demo page
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
302 ===============================================
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
303
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
304 What is this ``llvm.global_ctors`` and ``_GLOBAL__I_a...`` stuff that happens when I ``#include <iostream>``?
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
305 -------------------------------------------------------------------------------------------------------------
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
306 If you ``#include`` the ``<iostream>`` header into a C++ translation unit,
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
307 the file will probably use the ``std::cin``/``std::cout``/... global objects.
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
308 However, C++ does not guarantee an order of initialization between static
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
309 objects in different translation units, so if a static ctor/dtor in your .cpp
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
310 file used ``std::cout``, for example, the object would not necessarily be
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
311 automatically initialized before your use.
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
312
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
313 To make ``std::cout`` and friends work correctly in these scenarios, the STL
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
314 that we use declares a static object that gets created in every translation
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
315 unit that includes ``<iostream>``. This object has a static constructor
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
316 and destructor that initializes and destroys the global iostream objects
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
317 before they could possibly be used in the file. The code that you see in the
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
318 ``.ll`` file corresponds to the constructor and destructor registration code.
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
319
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
320 If you would like to make it easier to *understand* the LLVM code generated
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
321 by the compiler in the demo page, consider using ``printf()`` instead of
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
322 ``iostream``\s to print values.
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
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
325 Where did all of my code go??
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
326 -----------------------------
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
327 If you are using the LLVM demo page, you may often wonder what happened to
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
328 all of the code that you typed in. Remember that the demo script is running
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
329 the code through the LLVM optimizers, so if your code doesn't actually do
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
330 anything useful, it might all be deleted.
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
331
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
332 To prevent this, make sure that the code is actually needed. For example, if
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
333 you are computing some expression, return the value from the function instead
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
334 of leaving it in a local variable. If you really want to constrain the
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
335 optimizer, you can read from and assign to ``volatile`` global variables.
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
336
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
337
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
338 What is this "``undef``" thing that shows up in my code?
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
339 --------------------------------------------------------
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
340 ``undef`` is the LLVM way of representing a value that is not defined. You
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
341 can get these if you do not initialize a variable before you use it. For
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
342 example, the C function:
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 .. code-block:: c
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
345
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
346 int X() { int i; return i; }
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
347
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
348 Is compiled to "``ret i32 undef``" because "``i``" never has a value specified
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
349 for it.
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
350
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
351
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
352 Why does instcombine + simplifycfg turn a call to a function with a mismatched calling convention into "unreachable"? Why not make the verifier reject it?
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
353 ----------------------------------------------------------------------------------------------------------------------------------------------------------
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
354 This is a common problem run into by authors of front-ends that are using
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
355 custom calling conventions: you need to make sure to set the right calling
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
356 convention on both the function and on each call to the function. For
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
357 example, this code:
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
358
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
359 .. code-block:: llvm
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
360
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
361 define fastcc void @foo() {
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
362 ret void
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
363 }
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
364 define void @bar() {
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
365 call void @foo()
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
366 ret void
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
367 }
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 Is optimized to:
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
370
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
371 .. code-block:: llvm
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
372
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
373 define fastcc void @foo() {
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
374 ret void
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 define void @bar() {
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
377 unreachable
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
378 }
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
379
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
380 ... with "``opt -instcombine -simplifycfg``". This often bites people because
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
381 "all their code disappears". Setting the calling convention on the caller and
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
382 callee is required for indirect calls to work, so people often ask why not
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
383 make the verifier reject this sort of thing.
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
384
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
385 The answer is that this code has undefined behavior, but it is not illegal.
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
386 If we made it illegal, then every transformation that could potentially create
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
387 this would have to ensure that it doesn't, and there is valid code that can
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
388 create this sort of construct (in dead code). The sorts of things that can
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
389 cause this to happen are fairly contrived, but we still need to accept them.
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
390 Here's an example:
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
391
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
392 .. code-block:: llvm
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
393
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
394 define fastcc void @foo() {
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
395 ret void
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
396 }
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
397 define internal void @bar(void()* %FP, i1 %cond) {
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
398 br i1 %cond, label %T, label %F
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
399 T:
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
400 call void %FP()
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
401 ret void
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
402 F:
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
403 call fastcc void %FP()
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
404 ret void
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 define void @test() {
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
407 %X = or i1 false, false
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
408 call void @bar(void()* @foo, i1 %X)
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
409 ret void
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
410 }
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
411
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
412 In this example, "test" always passes ``@foo``/``false`` into ``bar``, which
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
413 ensures that it is dynamically called with the right calling conv (thus, the
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
414 code is perfectly well defined). If you run this through the inliner, you
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
415 get this (the explicit "or" is there so that the inliner doesn't dead code
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
416 eliminate a bunch of stuff):
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
417
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
418 .. code-block:: llvm
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 define fastcc void @foo() {
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
421 ret void
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 define void @test() {
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
424 %X = or i1 false, false
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
425 br i1 %X, label %T.i, label %F.i
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
426 T.i:
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
427 call void @foo()
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
428 br label %bar.exit
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
429 F.i:
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
430 call fastcc void @foo()
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
431 br label %bar.exit
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
432 bar.exit:
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
433 ret void
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
434 }
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 Here you can see that the inlining pass made an undefined call to ``@foo``
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
437 with the wrong calling convention. We really don't want to make the inliner
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
438 have to know about this sort of thing, so it needs to be valid code. In this
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
439 case, dead code elimination can trivially remove the undefined code. However,
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
440 if ``%X`` was an input argument to ``@test``, the inliner would produce this:
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
441
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
442 .. code-block:: llvm
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
443
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
444 define fastcc void @foo() {
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
445 ret void
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
446 }
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
447
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
448 define void @test(i1 %X) {
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
449 br i1 %X, label %T.i, label %F.i
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
450 T.i:
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
451 call void @foo()
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
452 br label %bar.exit
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
453 F.i:
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
454 call fastcc void @foo()
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
455 br label %bar.exit
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
456 bar.exit:
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
457 ret void
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
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
460 The interesting thing about this is that ``%X`` *must* be false for the
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
461 code to be well-defined, but no amount of dead code elimination will be able
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
462 to delete the broken call as unreachable. However, since
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
463 ``instcombine``/``simplifycfg`` turns the undefined call into unreachable, we
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
464 end up with a branch on a condition that goes to unreachable: a branch to
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
465 unreachable can never happen, so "``-inline -instcombine -simplifycfg``" is
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
466 able to produce:
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
467
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
468 .. code-block:: llvm
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
469
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
470 define fastcc void @foo() {
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
471 ret void
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
472 }
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
473 define void @test(i1 %X) {
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
474 F.i:
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
475 call fastcc void @foo()
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
476 ret void
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
477 }