1781 lines
57 KiB
HTML
1781 lines
57 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
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"http://www.w3.org/TR/html4/strict.dtd">
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<html>
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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
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<title>Source Level Debugging with LLVM</title>
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<link rel="stylesheet" href="llvm.css" type="text/css">
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</head>
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<body>
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<div class="doc_title">Source Level Debugging with LLVM</div>
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<table class="layout" style="width:100%">
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<tr class="layout">
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<td class="left">
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<ul>
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<li><a href="#introduction">Introduction</a>
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<ol>
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<li><a href="#phil">Philosophy behind LLVM debugging information</a></li>
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<li><a href="#consumers">Debug information consumers</a></li>
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<li><a href="#debugopt">Debugging optimized code</a></li>
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</ol></li>
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<li><a href="#format">Debugging information format</a>
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<ol>
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<li><a href="#debug_info_descriptors">Debug information descriptors</a>
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<ul>
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<li><a href="#format_compile_units">Compile unit descriptors</a></li>
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<li><a href="#format_files">File descriptors</a></li>
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<li><a href="#format_global_variables">Global variable descriptors</a></li>
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<li><a href="#format_subprograms">Subprogram descriptors</a></li>
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<li><a href="#format_blocks">Block descriptors</a></li>
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<li><a href="#format_basic_type">Basic type descriptors</a></li>
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<li><a href="#format_derived_type">Derived type descriptors</a></li>
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<li><a href="#format_composite_type">Composite type descriptors</a></li>
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<li><a href="#format_subrange">Subrange descriptors</a></li>
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<li><a href="#format_enumeration">Enumerator descriptors</a></li>
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<li><a href="#format_variables">Local variables</a></li>
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</ul></li>
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<li><a href="#format_common_intrinsics">Debugger intrinsic functions</a>
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<ul>
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<li><a href="#format_common_declare">llvm.dbg.declare</a></li>
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<li><a href="#format_common_value">llvm.dbg.value</a></li>
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</ul></li>
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</ol></li>
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<li><a href="#format_common_lifetime">Object lifetimes and scoping</a></li>
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<li><a href="#ccxx_frontend">C/C++ front-end specific debug information</a>
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<ol>
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<li><a href="#ccxx_compile_units">C/C++ source file information</a></li>
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<li><a href="#ccxx_global_variable">C/C++ global variable information</a></li>
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<li><a href="#ccxx_subprogram">C/C++ function information</a></li>
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<li><a href="#ccxx_basic_types">C/C++ basic types</a></li>
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<li><a href="#ccxx_derived_types">C/C++ derived types</a></li>
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<li><a href="#ccxx_composite_types">C/C++ struct/union types</a></li>
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<li><a href="#ccxx_enumeration_types">C/C++ enumeration types</a></li>
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</ol></li>
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</ul>
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</td>
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<td class="right">
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<img src="img/venusflytrap.jpg" alt="A leafy and green bug eater" width="247"
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height="369">
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</td>
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</tr></table>
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<div class="doc_author">
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<p>Written by <a href="mailto:sabre@nondot.org">Chris Lattner</a>
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and <a href="mailto:jlaskey@mac.com">Jim Laskey</a></p>
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</div>
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<!-- *********************************************************************** -->
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<div class="doc_section"><a name="introduction">Introduction</a></div>
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<!-- *********************************************************************** -->
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<div class="doc_text">
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<p>This document is the central repository for all information pertaining to
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debug information in LLVM. It describes the <a href="#format">actual format
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that the LLVM debug information</a> takes, which is useful for those
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interested in creating front-ends or dealing directly with the information.
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Further, this document provides specific examples of what debug information
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for C/C++.</p>
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</div>
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<!-- ======================================================================= -->
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<div class="doc_subsection">
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<a name="phil">Philosophy behind LLVM debugging information</a>
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</div>
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<div class="doc_text">
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<p>The idea of the LLVM debugging information is to capture how the important
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pieces of the source-language's Abstract Syntax Tree map onto LLVM code.
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Several design aspects have shaped the solution that appears here. The
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important ones are:</p>
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<ul>
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<li>Debugging information should have very little impact on the rest of the
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compiler. No transformations, analyses, or code generators should need to
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be modified because of debugging information.</li>
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<li>LLVM optimizations should interact in <a href="#debugopt">well-defined and
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easily described ways</a> with the debugging information.</li>
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<li>Because LLVM is designed to support arbitrary programming languages,
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LLVM-to-LLVM tools should not need to know anything about the semantics of
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the source-level-language.</li>
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<li>Source-level languages are often <b>widely</b> different from one another.
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LLVM should not put any restrictions of the flavor of the source-language,
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and the debugging information should work with any language.</li>
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<li>With code generator support, it should be possible to use an LLVM compiler
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to compile a program to native machine code and standard debugging
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formats. This allows compatibility with traditional machine-code level
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debuggers, like GDB or DBX.</li>
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</ul>
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<p>The approach used by the LLVM implementation is to use a small set
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of <a href="#format_common_intrinsics">intrinsic functions</a> to define a
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mapping between LLVM program objects and the source-level objects. The
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description of the source-level program is maintained in LLVM metadata
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in an <a href="#ccxx_frontend">implementation-defined format</a>
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(the C/C++ front-end currently uses working draft 7 of
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the <a href="http://www.eagercon.com/dwarf/dwarf3std.htm">DWARF 3
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standard</a>).</p>
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<p>When a program is being debugged, a debugger interacts with the user and
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turns the stored debug information into source-language specific information.
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As such, a debugger must be aware of the source-language, and is thus tied to
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a specific language or family of languages.</p>
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</div>
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<!-- ======================================================================= -->
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<div class="doc_subsection">
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<a name="consumers">Debug information consumers</a>
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</div>
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<div class="doc_text">
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<p>The role of debug information is to provide meta information normally
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stripped away during the compilation process. This meta information provides
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an LLVM user a relationship between generated code and the original program
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source code.</p>
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<p>Currently, debug information is consumed by DwarfDebug to produce dwarf
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information used by the gdb debugger. Other targets could use the same
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information to produce stabs or other debug forms.</p>
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<p>It would also be reasonable to use debug information to feed profiling tools
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for analysis of generated code, or, tools for reconstructing the original
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source from generated code.</p>
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<p>TODO - expound a bit more.</p>
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</div>
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<!-- ======================================================================= -->
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<div class="doc_subsection">
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<a name="debugopt">Debugging optimized code</a>
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</div>
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<div class="doc_text">
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<p>An extremely high priority of LLVM debugging information is to make it
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interact well with optimizations and analysis. In particular, the LLVM debug
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information provides the following guarantees:</p>
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<ul>
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<li>LLVM debug information <b>always provides information to accurately read
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the source-level state of the program</b>, regardless of which LLVM
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optimizations have been run, and without any modification to the
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optimizations themselves. However, some optimizations may impact the
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ability to modify the current state of the program with a debugger, such
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as setting program variables, or calling functions that have been
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deleted.</li>
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<li>LLVM optimizations gracefully interact with debugging information. If
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they are not aware of debug information, they are automatically disabled
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as necessary in the cases that would invalidate the debug info. This
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retains the LLVM features, making it easy to write new
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transformations.</li>
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<li>As desired, LLVM optimizations can be upgraded to be aware of the LLVM
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debugging information, allowing them to update the debugging information
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as they perform aggressive optimizations. This means that, with effort,
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the LLVM optimizers could optimize debug code just as well as non-debug
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code.</li>
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<li>LLVM debug information does not prevent many important optimizations from
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happening (for example inlining, basic block reordering/merging/cleanup,
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tail duplication, etc), further reducing the amount of the compiler that
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eventually is "aware" of debugging information.</li>
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<li>LLVM debug information is automatically optimized along with the rest of
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the program, using existing facilities. For example, duplicate
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information is automatically merged by the linker, and unused information
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is automatically removed.</li>
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</ul>
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<p>Basically, the debug information allows you to compile a program with
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"<tt>-O0 -g</tt>" and get full debug information, allowing you to arbitrarily
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modify the program as it executes from a debugger. Compiling a program with
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"<tt>-O3 -g</tt>" gives you full debug information that is always available
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and accurate for reading (e.g., you get accurate stack traces despite tail
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call elimination and inlining), but you might lose the ability to modify the
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program and call functions where were optimized out of the program, or
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inlined away completely.</p>
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<p><a href="TestingGuide.html#quicktestsuite">LLVM test suite</a> provides a
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framework to test optimizer's handling of debugging information. It can be
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run like this:</p>
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<div class="doc_code">
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<pre>
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% cd llvm/projects/test-suite/MultiSource/Benchmarks # or some other level
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% make TEST=dbgopt
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</pre>
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</div>
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<p>This will test impact of debugging information on optimization passes. If
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debugging information influences optimization passes then it will be reported
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as a failure. See <a href="TestingGuide.html">TestingGuide</a> for more
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information on LLVM test infrastructure and how to run various tests.</p>
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</div>
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<!-- *********************************************************************** -->
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<div class="doc_section">
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<a name="format">Debugging information format</a>
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</div>
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<!-- *********************************************************************** -->
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<div class="doc_text">
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<p>LLVM debugging information has been carefully designed to make it possible
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for the optimizer to optimize the program and debugging information without
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necessarily having to know anything about debugging information. In
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particular, the use of metadata avoids duplicated debugging information from
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the beginning, and the global dead code elimination pass automatically
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deletes debugging information for a function if it decides to delete the
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function. </p>
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<p>To do this, most of the debugging information (descriptors for types,
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variables, functions, source files, etc) is inserted by the language
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front-end in the form of LLVM metadata. </p>
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<p>Debug information is designed to be agnostic about the target debugger and
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debugging information representation (e.g. DWARF/Stabs/etc). It uses a
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generic pass to decode the information that represents variables, types,
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functions, namespaces, etc: this allows for arbitrary source-language
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semantics and type-systems to be used, as long as there is a module
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written for the target debugger to interpret the information. </p>
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<p>To provide basic functionality, the LLVM debugger does have to make some
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assumptions about the source-level language being debugged, though it keeps
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these to a minimum. The only common features that the LLVM debugger assumes
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exist are <a href="#format_files">source files</a>,
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and <a href="#format_global_variables">program objects</a>. These abstract
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objects are used by a debugger to form stack traces, show information about
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local variables, etc.</p>
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<p>This section of the documentation first describes the representation aspects
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common to any source-language. The <a href="#ccxx_frontend">next section</a>
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describes the data layout conventions used by the C and C++ front-ends.</p>
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</div>
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<!-- ======================================================================= -->
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<div class="doc_subsection">
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<a name="debug_info_descriptors">Debug information descriptors</a>
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</div>
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<div class="doc_text">
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<p>In consideration of the complexity and volume of debug information, LLVM
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provides a specification for well formed debug descriptors. </p>
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<p>Consumers of LLVM debug information expect the descriptors for program
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objects to start in a canonical format, but the descriptors can include
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additional information appended at the end that is source-language
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specific. All LLVM debugging information is versioned, allowing backwards
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compatibility in the case that the core structures need to change in some
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way. Also, all debugging information objects start with a tag to indicate
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what type of object it is. The source-language is allowed to define its own
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objects, by using unreserved tag numbers. We recommend using with tags in
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the range 0x1000 through 0x2000 (there is a defined enum DW_TAG_user_base =
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0x1000.)</p>
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<p>The fields of debug descriptors used internally by LLVM
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are restricted to only the simple data types <tt>i32</tt>, <tt>i1</tt>,
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<tt>float</tt>, <tt>double</tt>, <tt>mdstring</tt> and <tt>mdnode</tt>. </p>
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<div class="doc_code">
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<pre>
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!1 = metadata !{
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i32, ;; A tag
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...
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}
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</pre>
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</div>
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<p><a name="LLVMDebugVersion">The first field of a descriptor is always an
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<tt>i32</tt> containing a tag value identifying the content of the
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descriptor. The remaining fields are specific to the descriptor. The values
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of tags are loosely bound to the tag values of DWARF information entries.
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However, that does not restrict the use of the information supplied to DWARF
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targets. To facilitate versioning of debug information, the tag is augmented
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with the current debug version (LLVMDebugVersion = 8 << 16 or 0x80000 or
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524288.)</a></p>
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<p>The details of the various descriptors follow.</p>
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</div>
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<!-- ======================================================================= -->
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<div class="doc_subsubsection">
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<a name="format_compile_units">Compile unit descriptors</a>
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</div>
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<div class="doc_text">
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<div class="doc_code">
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<pre>
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!0 = metadata !{
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i32, ;; Tag = 17 + <a href="#LLVMDebugVersion">LLVMDebugVersion</a>
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;; (DW_TAG_compile_unit)
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i32, ;; Unused field.
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i32, ;; DWARF language identifier (ex. DW_LANG_C89)
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metadata, ;; Source file name
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metadata, ;; Source file directory (includes trailing slash)
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metadata ;; Producer (ex. "4.0.1 LLVM (LLVM research group)")
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i1, ;; True if this is a main compile unit.
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i1, ;; True if this is optimized.
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metadata, ;; Flags
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i32 ;; Runtime version
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}
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</pre>
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</div>
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<p>These descriptors contain a source language ID for the file (we use the DWARF
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3.0 ID numbers, such as <tt>DW_LANG_C89</tt>, <tt>DW_LANG_C_plus_plus</tt>,
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<tt>DW_LANG_Cobol74</tt>, etc), three strings describing the filename,
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working directory of the compiler, and an identifier string for the compiler
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that produced it.</p>
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<p>Compile unit descriptors provide the root context for objects declared in a
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specific compilation unit. File descriptors are defined using this context.</p>
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</div>
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<!-- ======================================================================= -->
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<div class="doc_subsubsection">
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<a name="format_files">File descriptors</a>
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</div>
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<div class="doc_text">
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<div class="doc_code">
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<pre>
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!0 = metadata !{
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i32, ;; Tag = 41 + <a href="#LLVMDebugVersion">LLVMDebugVersion</a>
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;; (DW_TAG_file_type)
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metadata, ;; Source file name
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metadata, ;; Source file directory (includes trailing slash)
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metadata ;; Reference to compile unit where defined
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}
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</pre>
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</div>
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<p>These descriptors contain information for a file. Global variables and top
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level functions would be defined using this context.k File descriptors also
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provide context for source line correspondence. </p>
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<p>Each input file is encoded as a separate file descriptor in LLVM debugging
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information output. Each file descriptor would be defined using a
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compile unit. </p>
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</div>
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<!-- ======================================================================= -->
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<div class="doc_subsubsection">
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<a name="format_global_variables">Global variable descriptors</a>
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</div>
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<div class="doc_text">
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<div class="doc_code">
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<pre>
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!1 = metadata !{
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i32, ;; Tag = 52 + <a href="#LLVMDebugVersion">LLVMDebugVersion</a>
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;; (DW_TAG_variable)
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i32, ;; Unused field.
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metadata, ;; Reference to context descriptor
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metadata, ;; Name
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metadata, ;; Display name (fully qualified C++ name)
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metadata, ;; MIPS linkage name (for C++)
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metadata, ;; Reference to file where defined
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i32, ;; Line number where defined
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metadata, ;; Reference to type descriptor
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i1, ;; True if the global is local to compile unit (static)
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i1, ;; True if the global is defined in the compile unit (not extern)
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{ }* ;; Reference to the global variable
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}
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</pre>
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</div>
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<p>These descriptors provide debug information about globals variables. The
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provide details such as name, type and where the variable is defined.</p>
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</div>
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<!-- ======================================================================= -->
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<div class="doc_subsubsection">
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<a name="format_subprograms">Subprogram descriptors</a>
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</div>
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<div class="doc_text">
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<div class="doc_code">
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<pre>
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!2 = metadata !{
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i32, ;; Tag = 46 + <a href="#LLVMDebugVersion">LLVMDebugVersion</a>
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;; (DW_TAG_subprogram)
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i32, ;; Unused field.
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metadata, ;; Reference to context descriptor
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metadata, ;; Name
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metadata, ;; Display name (fully qualified C++ name)
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metadata, ;; MIPS linkage name (for C++)
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metadata, ;; Reference to file where defined
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i32, ;; Line number where defined
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metadata, ;; Reference to type descriptor
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i1, ;; True if the global is local to compile unit (static)
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i1 ;; True if the global is defined in the compile unit (not extern)
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}
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</pre>
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</div>
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<p>These descriptors provide debug information about functions, methods and
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subprograms. They provide details such as name, return types and the source
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location where the subprogram is defined.</p>
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</div>
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<!-- ======================================================================= -->
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<div class="doc_subsubsection">
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<a name="format_blocks">Block descriptors</a>
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</div>
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|
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<div class="doc_text">
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<div class="doc_code">
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<pre>
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!3 = metadata !{
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i32, ;; Tag = 13 + <a href="#LLVMDebugVersion">LLVMDebugVersion</a> (DW_TAG_lexical_block)
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metadata ;; Reference to context descriptor
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}
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</pre>
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</div>
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<p>These descriptors provide debug information about nested blocks within a
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subprogram. The array of member descriptors is used to define local
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variables and deeper nested blocks.</p>
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|
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</div>
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|
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<!-- ======================================================================= -->
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<div class="doc_subsubsection">
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<a name="format_basic_type">Basic type descriptors</a>
|
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</div>
|
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|
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<div class="doc_text">
|
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|
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<div class="doc_code">
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<pre>
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!4 = metadata !{
|
|
i32, ;; Tag = 36 + <a href="#LLVMDebugVersion">LLVMDebugVersion</a>
|
|
;; (DW_TAG_base_type)
|
|
metadata, ;; Reference to context (typically a compile unit)
|
|
metadata, ;; Name (may be "" for anonymous types)
|
|
metadata, ;; Reference to file where defined (may be NULL)
|
|
i32, ;; Line number where defined (may be 0)
|
|
i64, ;; Size in bits
|
|
i64, ;; Alignment in bits
|
|
i64, ;; Offset in bits
|
|
i32, ;; Flags
|
|
i32 ;; DWARF type encoding
|
|
}
|
|
</pre>
|
|
</div>
|
|
|
|
<p>These descriptors define primitive types used in the code. Example int, bool
|
|
and float. The context provides the scope of the type, which is usually the
|
|
top level. Since basic types are not usually user defined the compile unit
|
|
and line number can be left as NULL and 0. The size, alignment and offset
|
|
are expressed in bits and can be 64 bit values. The alignment is used to
|
|
round the offset when embedded in a
|
|
<a href="#format_composite_type">composite type</a> (example to keep float
|
|
doubles on 64 bit boundaries.) The offset is the bit offset if embedded in
|
|
a <a href="#format_composite_type">composite type</a>.</p>
|
|
|
|
<p>The type encoding provides the details of the type. The values are typically
|
|
one of the following:</p>
|
|
|
|
<div class="doc_code">
|
|
<pre>
|
|
DW_ATE_address = 1
|
|
DW_ATE_boolean = 2
|
|
DW_ATE_float = 4
|
|
DW_ATE_signed = 5
|
|
DW_ATE_signed_char = 6
|
|
DW_ATE_unsigned = 7
|
|
DW_ATE_unsigned_char = 8
|
|
</pre>
|
|
</div>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<div class="doc_subsubsection">
|
|
<a name="format_derived_type">Derived type descriptors</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<div class="doc_code">
|
|
<pre>
|
|
!5 = metadata !{
|
|
i32, ;; Tag (see below)
|
|
metadata, ;; Reference to context
|
|
metadata, ;; Name (may be "" for anonymous types)
|
|
metadata, ;; Reference to file where defined (may be NULL)
|
|
i32, ;; Line number where defined (may be 0)
|
|
i32, ;; Size in bits
|
|
i32, ;; Alignment in bits
|
|
i32, ;; Offset in bits
|
|
metadata ;; Reference to type derived from
|
|
}
|
|
</pre>
|
|
</div>
|
|
|
|
<p>These descriptors are used to define types derived from other types. The
|
|
value of the tag varies depending on the meaning. The following are possible
|
|
tag values:</p>
|
|
|
|
<div class="doc_code">
|
|
<pre>
|
|
DW_TAG_formal_parameter = 5
|
|
DW_TAG_member = 13
|
|
DW_TAG_pointer_type = 15
|
|
DW_TAG_reference_type = 16
|
|
DW_TAG_typedef = 22
|
|
DW_TAG_const_type = 38
|
|
DW_TAG_volatile_type = 53
|
|
DW_TAG_restrict_type = 55
|
|
</pre>
|
|
</div>
|
|
|
|
<p><tt>DW_TAG_member</tt> is used to define a member of
|
|
a <a href="#format_composite_type">composite type</a>
|
|
or <a href="#format_subprograms">subprogram</a>. The type of the member is
|
|
the <a href="#format_derived_type">derived
|
|
type</a>. <tt>DW_TAG_formal_parameter</tt> is used to define a member which
|
|
is a formal argument of a subprogram.</p>
|
|
|
|
<p><tt>DW_TAG_typedef</tt> is used to provide a name for the derived type.</p>
|
|
|
|
<p><tt>DW_TAG_pointer_type</tt>,<tt>DW_TAG_reference_type</tt>,
|
|
<tt>DW_TAG_const_type</tt>, <tt>DW_TAG_volatile_type</tt>
|
|
and <tt>DW_TAG_restrict_type</tt> are used to qualify
|
|
the <a href="#format_derived_type">derived type</a>. </p>
|
|
|
|
<p><a href="#format_derived_type">Derived type</a> location can be determined
|
|
from the compile unit and line number. The size, alignment and offset are
|
|
expressed in bits and can be 64 bit values. The alignment is used to round
|
|
the offset when embedded in a <a href="#format_composite_type">composite
|
|
type</a> (example to keep float doubles on 64 bit boundaries.) The offset is
|
|
the bit offset if embedded in a <a href="#format_composite_type">composite
|
|
type</a>.</p>
|
|
|
|
<p>Note that the <tt>void *</tt> type is expressed as a
|
|
<tt>llvm.dbg.derivedtype.type</tt> with tag of <tt>DW_TAG_pointer_type</tt>
|
|
and <tt>NULL</tt> derived type.</p>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<div class="doc_subsubsection">
|
|
<a name="format_composite_type">Composite type descriptors</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<div class="doc_code">
|
|
<pre>
|
|
!6 = metadata !{
|
|
i32, ;; Tag (see below)
|
|
metadata, ;; Reference to context
|
|
metadata, ;; Name (may be "" for anonymous types)
|
|
metadata, ;; Reference to file where defined (may be NULL)
|
|
i32, ;; Line number where defined (may be 0)
|
|
i64, ;; Size in bits
|
|
i64, ;; Alignment in bits
|
|
i64, ;; Offset in bits
|
|
i32, ;; Flags
|
|
metadata, ;; Reference to type derived from
|
|
metadata, ;; Reference to array of member descriptors
|
|
i32 ;; Runtime languages
|
|
}
|
|
</pre>
|
|
</div>
|
|
|
|
<p>These descriptors are used to define types that are composed of 0 or more
|
|
elements. The value of the tag varies depending on the meaning. The following
|
|
are possible tag values:</p>
|
|
|
|
<div class="doc_code">
|
|
<pre>
|
|
DW_TAG_array_type = 1
|
|
DW_TAG_enumeration_type = 4
|
|
DW_TAG_structure_type = 19
|
|
DW_TAG_union_type = 23
|
|
DW_TAG_vector_type = 259
|
|
DW_TAG_subroutine_type = 21
|
|
DW_TAG_inheritance = 28
|
|
</pre>
|
|
</div>
|
|
|
|
<p>The vector flag indicates that an array type is a native packed vector.</p>
|
|
|
|
<p>The members of array types (tag = <tt>DW_TAG_array_type</tt>) or vector types
|
|
(tag = <tt>DW_TAG_vector_type</tt>) are <a href="#format_subrange">subrange
|
|
descriptors</a>, each representing the range of subscripts at that level of
|
|
indexing.</p>
|
|
|
|
<p>The members of enumeration types (tag = <tt>DW_TAG_enumeration_type</tt>) are
|
|
<a href="#format_enumeration">enumerator descriptors</a>, each representing
|
|
the definition of enumeration value for the set.</p>
|
|
|
|
<p>The members of structure (tag = <tt>DW_TAG_structure_type</tt>) or union (tag
|
|
= <tt>DW_TAG_union_type</tt>) types are any one of
|
|
the <a href="#format_basic_type">basic</a>,
|
|
<a href="#format_derived_type">derived</a>
|
|
or <a href="#format_composite_type">composite</a> type descriptors, each
|
|
representing a field member of the structure or union.</p>
|
|
|
|
<p>For C++ classes (tag = <tt>DW_TAG_structure_type</tt>), member descriptors
|
|
provide information about base classes, static members and member
|
|
functions. If a member is a <a href="#format_derived_type">derived type
|
|
descriptor</a> and has a tag of <tt>DW_TAG_inheritance</tt>, then the type
|
|
represents a base class. If the member of is
|
|
a <a href="#format_global_variables">global variable descriptor</a> then it
|
|
represents a static member. And, if the member is
|
|
a <a href="#format_subprograms">subprogram descriptor</a> then it represents
|
|
a member function. For static members and member
|
|
functions, <tt>getName()</tt> returns the members link or the C++ mangled
|
|
name. <tt>getDisplayName()</tt> the simplied version of the name.</p>
|
|
|
|
<p>The first member of subroutine (tag = <tt>DW_TAG_subroutine_type</tt>) type
|
|
elements is the return type for the subroutine. The remaining elements are
|
|
the formal arguments to the subroutine.</p>
|
|
|
|
<p><a href="#format_composite_type">Composite type</a> location can be
|
|
determined from the compile unit and line number. The size, alignment and
|
|
offset are expressed in bits and can be 64 bit values. The alignment is used
|
|
to round the offset when embedded in
|
|
a <a href="#format_composite_type">composite type</a> (as an example, to keep
|
|
float doubles on 64 bit boundaries.) The offset is the bit offset if embedded
|
|
in a <a href="#format_composite_type">composite type</a>.</p>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<div class="doc_subsubsection">
|
|
<a name="format_subrange">Subrange descriptors</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<div class="doc_code">
|
|
<pre>
|
|
%<a href="#format_subrange">llvm.dbg.subrange.type</a> = type {
|
|
i32, ;; Tag = 33 + <a href="#LLVMDebugVersion">LLVMDebugVersion</a> (DW_TAG_subrange_type)
|
|
i64, ;; Low value
|
|
i64 ;; High value
|
|
}
|
|
</pre>
|
|
</div>
|
|
|
|
<p>These descriptors are used to define ranges of array subscripts for an array
|
|
<a href="#format_composite_type">composite type</a>. The low value defines
|
|
the lower bounds typically zero for C/C++. The high value is the upper
|
|
bounds. Values are 64 bit. High - low + 1 is the size of the array. If low
|
|
== high the array will be unbounded.</p>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<div class="doc_subsubsection">
|
|
<a name="format_enumeration">Enumerator descriptors</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<div class="doc_code">
|
|
<pre>
|
|
!6 = metadata !{
|
|
i32, ;; Tag = 40 + <a href="#LLVMDebugVersion">LLVMDebugVersion</a>
|
|
;; (DW_TAG_enumerator)
|
|
metadata, ;; Name
|
|
i64 ;; Value
|
|
}
|
|
</pre>
|
|
</div>
|
|
|
|
<p>These descriptors are used to define members of an
|
|
enumeration <a href="#format_composite_type">composite type</a>, it
|
|
associates the name to the value.</p>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<div class="doc_subsubsection">
|
|
<a name="format_variables">Local variables</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<div class="doc_code">
|
|
<pre>
|
|
!7 = metadata !{
|
|
i32, ;; Tag (see below)
|
|
metadata, ;; Context
|
|
metadata, ;; Name
|
|
metadata, ;; Reference to file where defined
|
|
i32, ;; Line number where defined
|
|
metadata ;; Type descriptor
|
|
}
|
|
</pre>
|
|
</div>
|
|
|
|
<p>These descriptors are used to define variables local to a sub program. The
|
|
value of the tag depends on the usage of the variable:</p>
|
|
|
|
<div class="doc_code">
|
|
<pre>
|
|
DW_TAG_auto_variable = 256
|
|
DW_TAG_arg_variable = 257
|
|
DW_TAG_return_variable = 258
|
|
</pre>
|
|
</div>
|
|
|
|
<p>An auto variable is any variable declared in the body of the function. An
|
|
argument variable is any variable that appears as a formal argument to the
|
|
function. A return variable is used to track the result of a function and
|
|
has no source correspondent.</p>
|
|
|
|
<p>The context is either the subprogram or block where the variable is defined.
|
|
Name the source variable name. Compile unit and line indicate where the
|
|
variable was defined. Type descriptor defines the declared type of the
|
|
variable.</p>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<div class="doc_subsection">
|
|
<a name="format_common_intrinsics">Debugger intrinsic functions</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<p>LLVM uses several intrinsic functions (name prefixed with "llvm.dbg") to
|
|
provide debug information at various points in generated code.</p>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<div class="doc_subsubsection">
|
|
<a name="format_common_declare">llvm.dbg.declare</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
<pre>
|
|
void %<a href="#format_common_declare">llvm.dbg.declare</a>( { } *, metadata )
|
|
</pre>
|
|
|
|
<p>This intrinsic provides information about a local element (ex. variable.) The
|
|
first argument is the alloca for the variable, cast to a <tt>{ }*</tt>. The
|
|
second argument is
|
|
the <tt>%<a href="#format_variables">llvm.dbg.variable</a></tt> containing
|
|
the description of the variable. </p>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<div class="doc_subsubsection">
|
|
<a name="format_common_value">llvm.dbg.value</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
<pre>
|
|
void %<a href="#format_common_value">llvm.dbg.value</a>( metadata, i64, metadata )
|
|
</pre>
|
|
|
|
<p>This intrinsic provides information when a user source variable is set to a
|
|
new value. The first argument is the new value (wrapped as metadata). The
|
|
second argument is the offset in the user source variable where the new value
|
|
is written. The third argument is
|
|
the <tt>%<a href="#format_variables">llvm.dbg.variable</a></tt> containing
|
|
the description of the user source variable. </p>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<div class="doc_subsection">
|
|
<a name="format_common_lifetime">Object lifetimes and scoping</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
<p>In many languages, the local variables in functions can have their lifetimes
|
|
or scopes limited to a subset of a function. In the C family of languages,
|
|
for example, variables are only live (readable and writable) within the
|
|
source block that they are defined in. In functional languages, values are
|
|
only readable after they have been defined. Though this is a very obvious
|
|
concept, it is non-trivial to model in LLVM, because it has no notion of
|
|
scoping in this sense, and does not want to be tied to a language's scoping
|
|
rules.</p>
|
|
|
|
<p>In order to handle this, the LLVM debug format uses the metadata attached to
|
|
llvm instructions to encode line number and scoping information. Consider
|
|
the following C fragment, for example:</p>
|
|
|
|
<div class="doc_code">
|
|
<pre>
|
|
1. void foo() {
|
|
2. int X = 21;
|
|
3. int Y = 22;
|
|
4. {
|
|
5. int Z = 23;
|
|
6. Z = X;
|
|
7. }
|
|
8. X = Y;
|
|
9. }
|
|
</pre>
|
|
</div>
|
|
|
|
<p>Compiled to LLVM, this function would be represented like this:</p>
|
|
|
|
<div class="doc_code">
|
|
<pre>
|
|
define void @foo() nounwind ssp {
|
|
entry:
|
|
%X = alloca i32, align 4 ; <i32*> [#uses=4]
|
|
%Y = alloca i32, align 4 ; <i32*> [#uses=4]
|
|
%Z = alloca i32, align 4 ; <i32*> [#uses=3]
|
|
%0 = bitcast i32* %X to { }* ; <{ }*> [#uses=1]
|
|
call void @llvm.dbg.declare({ }* %0, metadata !0), !dbg !7
|
|
store i32 21, i32* %X, !dbg !8
|
|
%1 = bitcast i32* %Y to { }* ; <{ }*> [#uses=1]
|
|
call void @llvm.dbg.declare({ }* %1, metadata !9), !dbg !10
|
|
store i32 22, i32* %Y, !dbg !11
|
|
%2 = bitcast i32* %Z to { }* ; <{ }*> [#uses=1]
|
|
call void @llvm.dbg.declare({ }* %2, metadata !12), !dbg !14
|
|
store i32 23, i32* %Z, !dbg !15
|
|
%tmp = load i32* %X, !dbg !16 ; <i32> [#uses=1]
|
|
%tmp1 = load i32* %Y, !dbg !16 ; <i32> [#uses=1]
|
|
%add = add nsw i32 %tmp, %tmp1, !dbg !16 ; <i32> [#uses=1]
|
|
store i32 %add, i32* %Z, !dbg !16
|
|
%tmp2 = load i32* %Y, !dbg !17 ; <i32> [#uses=1]
|
|
store i32 %tmp2, i32* %X, !dbg !17
|
|
ret void, !dbg !18
|
|
}
|
|
|
|
declare void @llvm.dbg.declare({ }*, metadata) nounwind readnone
|
|
|
|
!0 = metadata !{i32 459008, metadata !1, metadata !"X",
|
|
metadata !3, i32 2, metadata !6}; [ DW_TAG_auto_variable ]
|
|
!1 = metadata !{i32 458763, metadata !2}; [DW_TAG_lexical_block ]
|
|
!2 = metadata !{i32 458798, i32 0, metadata !3, metadata !"foo", metadata !"foo",
|
|
metadata !"foo", metadata !3, i32 1, metadata !4,
|
|
i1 false, i1 true}; [DW_TAG_subprogram ]
|
|
!3 = metadata !{i32 458769, i32 0, i32 12, metadata !"foo.c",
|
|
metadata !"/private/tmp", metadata !"clang 1.1", i1 true,
|
|
i1 false, metadata !"", i32 0}; [DW_TAG_compile_unit ]
|
|
!4 = metadata !{i32 458773, metadata !3, metadata !"", null, i32 0, i64 0, i64 0,
|
|
i64 0, i32 0, null, metadata !5, i32 0}; [DW_TAG_subroutine_type ]
|
|
!5 = metadata !{null}
|
|
!6 = metadata !{i32 458788, metadata !3, metadata !"int", metadata !3, i32 0,
|
|
i64 32, i64 32, i64 0, i32 0, i32 5}; [DW_TAG_base_type ]
|
|
!7 = metadata !{i32 2, i32 7, metadata !1, null}
|
|
!8 = metadata !{i32 2, i32 3, metadata !1, null}
|
|
!9 = metadata !{i32 459008, metadata !1, metadata !"Y", metadata !3, i32 3,
|
|
metadata !6}; [ DW_TAG_auto_variable ]
|
|
!10 = metadata !{i32 3, i32 7, metadata !1, null}
|
|
!11 = metadata !{i32 3, i32 3, metadata !1, null}
|
|
!12 = metadata !{i32 459008, metadata !13, metadata !"Z", metadata !3, i32 5,
|
|
metadata !6}; [ DW_TAG_auto_variable ]
|
|
!13 = metadata !{i32 458763, metadata !1}; [DW_TAG_lexical_block ]
|
|
!14 = metadata !{i32 5, i32 9, metadata !13, null}
|
|
!15 = metadata !{i32 5, i32 5, metadata !13, null}
|
|
!16 = metadata !{i32 6, i32 5, metadata !13, null}
|
|
!17 = metadata !{i32 8, i32 3, metadata !1, null}
|
|
!18 = metadata !{i32 9, i32 1, metadata !2, null}
|
|
</pre>
|
|
</div>
|
|
|
|
<p>This example illustrates a few important details about LLVM debugging
|
|
information. In particular, it shows how the <tt>llvm.dbg.declare</tt>
|
|
intrinsic and location information, which are attached to an instruction,
|
|
are applied together to allow a debugger to analyze the relationship between
|
|
statements, variable definitions, and the code used to implement the
|
|
function.</p>
|
|
|
|
<div class="doc_code">
|
|
<pre>
|
|
call void @llvm.dbg.declare({ }* %0, metadata !0), !dbg !7
|
|
</pre>
|
|
</div>
|
|
|
|
<p>The first intrinsic
|
|
<tt>%<a href="#format_common_declare">llvm.dbg.declare</a></tt>
|
|
encodes debugging information for the variable <tt>X</tt>. The metadata
|
|
<tt>!dbg !7</tt> attached to the intrinsic provides scope information for the
|
|
variable <tt>X</tt>.</p>
|
|
|
|
<div class="doc_code">
|
|
<pre>
|
|
!7 = metadata !{i32 2, i32 7, metadata !1, null}
|
|
!1 = metadata !{i32 458763, metadata !2}; [DW_TAG_lexical_block ]
|
|
!2 = metadata !{i32 458798, i32 0, metadata !3, metadata !"foo",
|
|
metadata !"foo", metadata !"foo", metadata !3, i32 1,
|
|
metadata !4, i1 false, i1 true}; [DW_TAG_subprogram ]
|
|
</pre>
|
|
</div>
|
|
|
|
<p>Here <tt>!7</tt> is metadata providing location information. It has four
|
|
fields: line number, column number, scope, and original scope. The original
|
|
scope represents inline location if this instruction is inlined inside a
|
|
caller, and is null otherwise. In this example, scope is encoded by
|
|
<tt>!1</tt>. <tt>!1</tt> represents a lexical block inside the scope
|
|
<tt>!2</tt>, where <tt>!2</tt> is a
|
|
<a href="#format_subprograms">subprogram descriptor</a>. This way the
|
|
location information attached to the intrinsics indicates that the
|
|
variable <tt>X</tt> is declared at line number 2 at a function level scope in
|
|
function <tt>foo</tt>.</p>
|
|
|
|
<p>Now lets take another example.</p>
|
|
|
|
<div class="doc_code">
|
|
<pre>
|
|
call void @llvm.dbg.declare({ }* %2, metadata !12), !dbg !14
|
|
</pre>
|
|
</div>
|
|
|
|
<p>The second intrinsic
|
|
<tt>%<a href="#format_common_declare">llvm.dbg.declare</a></tt>
|
|
encodes debugging information for variable <tt>Z</tt>. The metadata
|
|
<tt>!dbg !14</tt> attached to the intrinsic provides scope information for
|
|
the variable <tt>Z</tt>.</p>
|
|
|
|
<div class="doc_code">
|
|
<pre>
|
|
!13 = metadata !{i32 458763, metadata !1}; [DW_TAG_lexical_block ]
|
|
!14 = metadata !{i32 5, i32 9, metadata !13, null}
|
|
</pre>
|
|
</div>
|
|
|
|
<p>Here <tt>!14</tt> indicates that <tt>Z</tt> is declared at line number 5 and
|
|
column number 9 inside of lexical scope <tt>!13</tt>. The lexical scope
|
|
itself resides inside of lexical scope <tt>!1</tt> described above.</p>
|
|
|
|
<p>The scope information attached with each instruction provides a
|
|
straightforward way to find instructions covered by a scope.</p>
|
|
|
|
</div>
|
|
|
|
<!-- *********************************************************************** -->
|
|
<div class="doc_section">
|
|
<a name="ccxx_frontend">C/C++ front-end specific debug information</a>
|
|
</div>
|
|
<!-- *********************************************************************** -->
|
|
|
|
<div class="doc_text">
|
|
|
|
<p>The C and C++ front-ends represent information about the program in a format
|
|
that is effectively identical
|
|
to <a href="http://www.eagercon.com/dwarf/dwarf3std.htm">DWARF 3.0</a> in
|
|
terms of information content. This allows code generators to trivially
|
|
support native debuggers by generating standard dwarf information, and
|
|
contains enough information for non-dwarf targets to translate it as
|
|
needed.</p>
|
|
|
|
<p>This section describes the forms used to represent C and C++ programs. Other
|
|
languages could pattern themselves after this (which itself is tuned to
|
|
representing programs in the same way that DWARF 3 does), or they could
|
|
choose to provide completely different forms if they don't fit into the DWARF
|
|
model. As support for debugging information gets added to the various LLVM
|
|
source-language front-ends, the information used should be documented
|
|
here.</p>
|
|
|
|
<p>The following sections provide examples of various C/C++ constructs and the
|
|
debug information that would best describe those constructs.</p>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<div class="doc_subsection">
|
|
<a name="ccxx_compile_units">C/C++ source file information</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<p>Given the source files <tt>MySource.cpp</tt> and <tt>MyHeader.h</tt> located
|
|
in the directory <tt>/Users/mine/sources</tt>, the following code:</p>
|
|
|
|
<div class="doc_code">
|
|
<pre>
|
|
#include "MyHeader.h"
|
|
|
|
int main(int argc, char *argv[]) {
|
|
return 0;
|
|
}
|
|
</pre>
|
|
</div>
|
|
|
|
<p>a C/C++ front-end would generate the following descriptors:</p>
|
|
|
|
<div class="doc_code">
|
|
<pre>
|
|
...
|
|
;;
|
|
;; Define the compile unit for the main source file "/Users/mine/sources/MySource.cpp".
|
|
;;
|
|
!2 = metadata !{
|
|
i32 524305, ;; Tag
|
|
i32 0, ;; Unused
|
|
i32 4, ;; Language Id
|
|
metadata !"MySource.cpp",
|
|
metadata !"/Users/mine/sources",
|
|
metadata !"4.2.1 (Based on Apple Inc. build 5649) (LLVM build 00)",
|
|
i1 true, ;; Main Compile Unit
|
|
i1 false, ;; Optimized compile unit
|
|
metadata !"", ;; Compiler flags
|
|
i32 0} ;; Runtime version
|
|
|
|
;;
|
|
;; Define the file for the file "/Users/mine/sources/MySource.cpp".
|
|
;;
|
|
!1 = metadata !{
|
|
i32 524329, ;; Tag
|
|
metadata !"MySource.cpp",
|
|
metadata !"/Users/mine/sources",
|
|
metadata !3 ;; Compile unit
|
|
}
|
|
|
|
;;
|
|
;; Define the file for the file "/Users/mine/sources/Myheader.h"
|
|
;;
|
|
!3 = metadata !{
|
|
i32 524329, ;; Tag
|
|
metadata !"Myheader.h"
|
|
metadata !"/Users/mine/sources",
|
|
metadata !3 ;; Compile unit
|
|
}
|
|
|
|
...
|
|
</pre>
|
|
</div>
|
|
|
|
<p>llvm::Instruction provides easy access to metadata attached with an
|
|
instruction. One can extract line number information encoded in LLVM IR
|
|
using <tt>Instruction::getMetadata()</tt> and
|
|
<tt>DILocation::getLineNumber()</tt>.
|
|
<pre>
|
|
if (MDNode *N = I->getMetadata("dbg")) { // Here I is an LLVM instruction
|
|
DILocation Loc(N); // DILocation is in DebugInfo.h
|
|
unsigned Line = Loc.getLineNumber();
|
|
StringRef File = Loc.getFilename();
|
|
StringRef Dir = Loc.getDirectory();
|
|
}
|
|
</pre>
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<div class="doc_subsection">
|
|
<a name="ccxx_global_variable">C/C++ global variable information</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<p>Given an integer global variable declared as follows:</p>
|
|
|
|
<div class="doc_code">
|
|
<pre>
|
|
int MyGlobal = 100;
|
|
</pre>
|
|
</div>
|
|
|
|
<p>a C/C++ front-end would generate the following descriptors:</p>
|
|
|
|
<div class="doc_code">
|
|
<pre>
|
|
;;
|
|
;; Define the global itself.
|
|
;;
|
|
%MyGlobal = global int 100
|
|
...
|
|
;;
|
|
;; List of debug info of globals
|
|
;;
|
|
!llvm.dbg.gv = !{!0}
|
|
|
|
;;
|
|
;; Define the global variable descriptor. Note the reference to the global
|
|
;; variable anchor and the global variable itself.
|
|
;;
|
|
!0 = metadata !{
|
|
i32 524340, ;; Tag
|
|
i32 0, ;; Unused
|
|
metadata !1, ;; Context
|
|
metadata !"MyGlobal", ;; Name
|
|
metadata !"MyGlobal", ;; Display Name
|
|
metadata !"MyGlobal", ;; Linkage Name
|
|
metadata !3, ;; Compile Unit
|
|
i32 1, ;; Line Number
|
|
metadata !4, ;; Type
|
|
i1 false, ;; Is a local variable
|
|
i1 true, ;; Is this a definition
|
|
i32* @MyGlobal ;; The global variable
|
|
}
|
|
|
|
;;
|
|
;; Define the basic type of 32 bit signed integer. Note that since int is an
|
|
;; intrinsic type the source file is NULL and line 0.
|
|
;;
|
|
!4 = metadata !{
|
|
i32 524324, ;; Tag
|
|
metadata !1, ;; Context
|
|
metadata !"int", ;; Name
|
|
metadata !1, ;; File
|
|
i32 0, ;; Line number
|
|
i64 32, ;; Size in Bits
|
|
i64 32, ;; Align in Bits
|
|
i64 0, ;; Offset in Bits
|
|
i32 0, ;; Flags
|
|
i32 5 ;; Encoding
|
|
}
|
|
|
|
</pre>
|
|
</div>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<div class="doc_subsection">
|
|
<a name="ccxx_subprogram">C/C++ function information</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<p>Given a function declared as follows:</p>
|
|
|
|
<div class="doc_code">
|
|
<pre>
|
|
int main(int argc, char *argv[]) {
|
|
return 0;
|
|
}
|
|
</pre>
|
|
</div>
|
|
|
|
<p>a C/C++ front-end would generate the following descriptors:</p>
|
|
|
|
<div class="doc_code">
|
|
<pre>
|
|
;;
|
|
;; Define the anchor for subprograms. Note that the second field of the
|
|
;; anchor is 46, which is the same as the tag for subprograms
|
|
;; (46 = DW_TAG_subprogram.)
|
|
;;
|
|
!6 = metadata !{
|
|
i32 524334, ;; Tag
|
|
i32 0, ;; Unused
|
|
metadata !1, ;; Context
|
|
metadata !"main", ;; Name
|
|
metadata !"main", ;; Display name
|
|
metadata !"main", ;; Linkage name
|
|
metadata !1, ;; File
|
|
i32 1, ;; Line number
|
|
metadata !4, ;; Type
|
|
i1 false, ;; Is local
|
|
i1 true ;; Is definition
|
|
}
|
|
;;
|
|
;; Define the subprogram itself.
|
|
;;
|
|
define i32 @main(i32 %argc, i8** %argv) {
|
|
...
|
|
}
|
|
</pre>
|
|
</div>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<div class="doc_subsection">
|
|
<a name="ccxx_basic_types">C/C++ basic types</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<p>The following are the basic type descriptors for C/C++ core types:</p>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<div class="doc_subsubsection">
|
|
<a name="ccxx_basic_type_bool">bool</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<div class="doc_code">
|
|
<pre>
|
|
!2 = metadata !{
|
|
i32 524324, ;; Tag
|
|
metadata !1, ;; Context
|
|
metadata !"bool", ;; Name
|
|
metadata !1, ;; File
|
|
i32 0, ;; Line number
|
|
i64 8, ;; Size in Bits
|
|
i64 8, ;; Align in Bits
|
|
i64 0, ;; Offset in Bits
|
|
i32 0, ;; Flags
|
|
i32 2 ;; Encoding
|
|
}
|
|
</pre>
|
|
</div>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<div class="doc_subsubsection">
|
|
<a name="ccxx_basic_char">char</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<div class="doc_code">
|
|
<pre>
|
|
!2 = metadata !{
|
|
i32 524324, ;; Tag
|
|
metadata !1, ;; Context
|
|
metadata !"char", ;; Name
|
|
metadata !1, ;; File
|
|
i32 0, ;; Line number
|
|
i64 8, ;; Size in Bits
|
|
i64 8, ;; Align in Bits
|
|
i64 0, ;; Offset in Bits
|
|
i32 0, ;; Flags
|
|
i32 6 ;; Encoding
|
|
}
|
|
</pre>
|
|
</div>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<div class="doc_subsubsection">
|
|
<a name="ccxx_basic_unsigned_char">unsigned char</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<div class="doc_code">
|
|
<pre>
|
|
!2 = metadata !{
|
|
i32 524324, ;; Tag
|
|
metadata !1, ;; Context
|
|
metadata !"unsigned char",
|
|
metadata !1, ;; File
|
|
i32 0, ;; Line number
|
|
i64 8, ;; Size in Bits
|
|
i64 8, ;; Align in Bits
|
|
i64 0, ;; Offset in Bits
|
|
i32 0, ;; Flags
|
|
i32 8 ;; Encoding
|
|
}
|
|
</pre>
|
|
</div>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<div class="doc_subsubsection">
|
|
<a name="ccxx_basic_short">short</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<div class="doc_code">
|
|
<pre>
|
|
!2 = metadata !{
|
|
i32 524324, ;; Tag
|
|
metadata !1, ;; Context
|
|
metadata !"short int",
|
|
metadata !1, ;; File
|
|
i32 0, ;; Line number
|
|
i64 16, ;; Size in Bits
|
|
i64 16, ;; Align in Bits
|
|
i64 0, ;; Offset in Bits
|
|
i32 0, ;; Flags
|
|
i32 5 ;; Encoding
|
|
}
|
|
</pre>
|
|
</div>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<div class="doc_subsubsection">
|
|
<a name="ccxx_basic_unsigned_short">unsigned short</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<div class="doc_code">
|
|
<pre>
|
|
!2 = metadata !{
|
|
i32 524324, ;; Tag
|
|
metadata !1, ;; Context
|
|
metadata !"short unsigned int",
|
|
metadata !1, ;; File
|
|
i32 0, ;; Line number
|
|
i64 16, ;; Size in Bits
|
|
i64 16, ;; Align in Bits
|
|
i64 0, ;; Offset in Bits
|
|
i32 0, ;; Flags
|
|
i32 7 ;; Encoding
|
|
}
|
|
</pre>
|
|
</div>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<div class="doc_subsubsection">
|
|
<a name="ccxx_basic_int">int</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<div class="doc_code">
|
|
<pre>
|
|
!2 = metadata !{
|
|
i32 524324, ;; Tag
|
|
metadata !1, ;; Context
|
|
metadata !"int", ;; Name
|
|
metadata !1, ;; File
|
|
i32 0, ;; Line number
|
|
i64 32, ;; Size in Bits
|
|
i64 32, ;; Align in Bits
|
|
i64 0, ;; Offset in Bits
|
|
i32 0, ;; Flags
|
|
i32 5 ;; Encoding
|
|
}
|
|
</pre></div>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<div class="doc_subsubsection">
|
|
<a name="ccxx_basic_unsigned_int">unsigned int</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<div class="doc_code">
|
|
<pre>
|
|
!2 = metadata !{
|
|
i32 524324, ;; Tag
|
|
metadata !1, ;; Context
|
|
metadata !"unsigned int",
|
|
metadata !1, ;; File
|
|
i32 0, ;; Line number
|
|
i64 32, ;; Size in Bits
|
|
i64 32, ;; Align in Bits
|
|
i64 0, ;; Offset in Bits
|
|
i32 0, ;; Flags
|
|
i32 7 ;; Encoding
|
|
}
|
|
</pre>
|
|
</div>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<div class="doc_subsubsection">
|
|
<a name="ccxx_basic_long_long">long long</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<div class="doc_code">
|
|
<pre>
|
|
!2 = metadata !{
|
|
i32 524324, ;; Tag
|
|
metadata !1, ;; Context
|
|
metadata !"long long int",
|
|
metadata !1, ;; File
|
|
i32 0, ;; Line number
|
|
i64 64, ;; Size in Bits
|
|
i64 64, ;; Align in Bits
|
|
i64 0, ;; Offset in Bits
|
|
i32 0, ;; Flags
|
|
i32 5 ;; Encoding
|
|
}
|
|
</pre>
|
|
</div>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<div class="doc_subsubsection">
|
|
<a name="ccxx_basic_unsigned_long_long">unsigned long long</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<div class="doc_code">
|
|
<pre>
|
|
!2 = metadata !{
|
|
i32 524324, ;; Tag
|
|
metadata !1, ;; Context
|
|
metadata !"long long unsigned int",
|
|
metadata !1, ;; File
|
|
i32 0, ;; Line number
|
|
i64 64, ;; Size in Bits
|
|
i64 64, ;; Align in Bits
|
|
i64 0, ;; Offset in Bits
|
|
i32 0, ;; Flags
|
|
i32 7 ;; Encoding
|
|
}
|
|
</pre>
|
|
</div>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<div class="doc_subsubsection">
|
|
<a name="ccxx_basic_float">float</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<div class="doc_code">
|
|
<pre>
|
|
!2 = metadata !{
|
|
i32 524324, ;; Tag
|
|
metadata !1, ;; Context
|
|
metadata !"float",
|
|
metadata !1, ;; File
|
|
i32 0, ;; Line number
|
|
i64 32, ;; Size in Bits
|
|
i64 32, ;; Align in Bits
|
|
i64 0, ;; Offset in Bits
|
|
i32 0, ;; Flags
|
|
i32 4 ;; Encoding
|
|
}
|
|
</pre>
|
|
</div>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<div class="doc_subsubsection">
|
|
<a name="ccxx_basic_double">double</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<div class="doc_code">
|
|
<pre>
|
|
!2 = metadata !{
|
|
i32 524324, ;; Tag
|
|
metadata !1, ;; Context
|
|
metadata !"double",;; Name
|
|
metadata !1, ;; File
|
|
i32 0, ;; Line number
|
|
i64 64, ;; Size in Bits
|
|
i64 64, ;; Align in Bits
|
|
i64 0, ;; Offset in Bits
|
|
i32 0, ;; Flags
|
|
i32 4 ;; Encoding
|
|
}
|
|
</pre>
|
|
</div>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<div class="doc_subsection">
|
|
<a name="ccxx_derived_types">C/C++ derived types</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<p>Given the following as an example of C/C++ derived type:</p>
|
|
|
|
<div class="doc_code">
|
|
<pre>
|
|
typedef const int *IntPtr;
|
|
</pre>
|
|
</div>
|
|
|
|
<p>a C/C++ front-end would generate the following descriptors:</p>
|
|
|
|
<div class="doc_code">
|
|
<pre>
|
|
;;
|
|
;; Define the typedef "IntPtr".
|
|
;;
|
|
!2 = metadata !{
|
|
i32 524310, ;; Tag
|
|
metadata !1, ;; Context
|
|
metadata !"IntPtr", ;; Name
|
|
metadata !3, ;; File
|
|
i32 0, ;; Line number
|
|
i64 0, ;; Size in bits
|
|
i64 0, ;; Align in bits
|
|
i64 0, ;; Offset in bits
|
|
i32 0, ;; Flags
|
|
metadata !4 ;; Derived From type
|
|
}
|
|
|
|
;;
|
|
;; Define the pointer type.
|
|
;;
|
|
!4 = metadata !{
|
|
i32 524303, ;; Tag
|
|
metadata !1, ;; Context
|
|
metadata !"", ;; Name
|
|
metadata !1, ;; File
|
|
i32 0, ;; Line number
|
|
i64 64, ;; Size in bits
|
|
i64 64, ;; Align in bits
|
|
i64 0, ;; Offset in bits
|
|
i32 0, ;; Flags
|
|
metadata !5 ;; Derived From type
|
|
}
|
|
;;
|
|
;; Define the const type.
|
|
;;
|
|
!5 = metadata !{
|
|
i32 524326, ;; Tag
|
|
metadata !1, ;; Context
|
|
metadata !"", ;; Name
|
|
metadata !1, ;; File
|
|
i32 0, ;; Line number
|
|
i64 32, ;; Size in bits
|
|
i64 32, ;; Align in bits
|
|
i64 0, ;; Offset in bits
|
|
i32 0, ;; Flags
|
|
metadata !6 ;; Derived From type
|
|
}
|
|
;;
|
|
;; Define the int type.
|
|
;;
|
|
!6 = metadata !{
|
|
i32 524324, ;; Tag
|
|
metadata !1, ;; Context
|
|
metadata !"int", ;; Name
|
|
metadata !1, ;; File
|
|
i32 0, ;; Line number
|
|
i64 32, ;; Size in bits
|
|
i64 32, ;; Align in bits
|
|
i64 0, ;; Offset in bits
|
|
i32 0, ;; Flags
|
|
5 ;; Encoding
|
|
}
|
|
</pre>
|
|
</div>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<div class="doc_subsection">
|
|
<a name="ccxx_composite_types">C/C++ struct/union types</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<p>Given the following as an example of C/C++ struct type:</p>
|
|
|
|
<div class="doc_code">
|
|
<pre>
|
|
struct Color {
|
|
unsigned Red;
|
|
unsigned Green;
|
|
unsigned Blue;
|
|
};
|
|
</pre>
|
|
</div>
|
|
|
|
<p>a C/C++ front-end would generate the following descriptors:</p>
|
|
|
|
<div class="doc_code">
|
|
<pre>
|
|
;;
|
|
;; Define basic type for unsigned int.
|
|
;;
|
|
!5 = metadata !{
|
|
i32 524324, ;; Tag
|
|
metadata !1, ;; Context
|
|
metadata !"unsigned int",
|
|
metadata !1, ;; File
|
|
i32 0, ;; Line number
|
|
i64 32, ;; Size in Bits
|
|
i64 32, ;; Align in Bits
|
|
i64 0, ;; Offset in Bits
|
|
i32 0, ;; Flags
|
|
i32 7 ;; Encoding
|
|
}
|
|
;;
|
|
;; Define composite type for struct Color.
|
|
;;
|
|
!2 = metadata !{
|
|
i32 524307, ;; Tag
|
|
metadata !1, ;; Context
|
|
metadata !"Color", ;; Name
|
|
metadata !1, ;; Compile unit
|
|
i32 1, ;; Line number
|
|
i64 96, ;; Size in bits
|
|
i64 32, ;; Align in bits
|
|
i64 0, ;; Offset in bits
|
|
i32 0, ;; Flags
|
|
null, ;; Derived From
|
|
metadata !3, ;; Elements
|
|
i32 0 ;; Runtime Language
|
|
}
|
|
|
|
;;
|
|
;; Define the Red field.
|
|
;;
|
|
!4 = metadata !{
|
|
i32 524301, ;; Tag
|
|
metadata !1, ;; Context
|
|
metadata !"Red", ;; Name
|
|
metadata !1, ;; File
|
|
i32 2, ;; Line number
|
|
i64 32, ;; Size in bits
|
|
i64 32, ;; Align in bits
|
|
i64 0, ;; Offset in bits
|
|
i32 0, ;; Flags
|
|
metadata !5 ;; Derived From type
|
|
}
|
|
|
|
;;
|
|
;; Define the Green field.
|
|
;;
|
|
!6 = metadata !{
|
|
i32 524301, ;; Tag
|
|
metadata !1, ;; Context
|
|
metadata !"Green", ;; Name
|
|
metadata !1, ;; File
|
|
i32 3, ;; Line number
|
|
i64 32, ;; Size in bits
|
|
i64 32, ;; Align in bits
|
|
i64 32, ;; Offset in bits
|
|
i32 0, ;; Flags
|
|
metadata !5 ;; Derived From type
|
|
}
|
|
|
|
;;
|
|
;; Define the Blue field.
|
|
;;
|
|
!7 = metadata !{
|
|
i32 524301, ;; Tag
|
|
metadata !1, ;; Context
|
|
metadata !"Blue", ;; Name
|
|
metadata !1, ;; File
|
|
i32 4, ;; Line number
|
|
i64 32, ;; Size in bits
|
|
i64 32, ;; Align in bits
|
|
i64 64, ;; Offset in bits
|
|
i32 0, ;; Flags
|
|
metadata !5 ;; Derived From type
|
|
}
|
|
|
|
;;
|
|
;; Define the array of fields used by the composite type Color.
|
|
;;
|
|
!3 = metadata !{metadata !4, metadata !6, metadata !7}
|
|
</pre>
|
|
</div>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<div class="doc_subsection">
|
|
<a name="ccxx_enumeration_types">C/C++ enumeration types</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<p>Given the following as an example of C/C++ enumeration type:</p>
|
|
|
|
<div class="doc_code">
|
|
<pre>
|
|
enum Trees {
|
|
Spruce = 100,
|
|
Oak = 200,
|
|
Maple = 300
|
|
};
|
|
</pre>
|
|
</div>
|
|
|
|
<p>a C/C++ front-end would generate the following descriptors:</p>
|
|
|
|
<div class="doc_code">
|
|
<pre>
|
|
;;
|
|
;; Define composite type for enum Trees
|
|
;;
|
|
!2 = metadata !{
|
|
i32 524292, ;; Tag
|
|
metadata !1, ;; Context
|
|
metadata !"Trees", ;; Name
|
|
metadata !1, ;; File
|
|
i32 1, ;; Line number
|
|
i64 32, ;; Size in bits
|
|
i64 32, ;; Align in bits
|
|
i64 0, ;; Offset in bits
|
|
i32 0, ;; Flags
|
|
null, ;; Derived From type
|
|
metadata !3, ;; Elements
|
|
i32 0 ;; Runtime language
|
|
}
|
|
|
|
;;
|
|
;; Define the array of enumerators used by composite type Trees.
|
|
;;
|
|
!3 = metadata !{metadata !4, metadata !5, metadata !6}
|
|
|
|
;;
|
|
;; Define Spruce enumerator.
|
|
;;
|
|
!4 = metadata !{i32 524328, metadata !"Spruce", i64 100}
|
|
|
|
;;
|
|
;; Define Oak enumerator.
|
|
;;
|
|
!5 = metadata !{i32 524328, metadata !"Oak", i64 200}
|
|
|
|
;;
|
|
;; Define Maple enumerator.
|
|
;;
|
|
!6 = metadata !{i32 524328, metadata !"Maple", i64 300}
|
|
|
|
</pre>
|
|
</div>
|
|
|
|
</div>
|
|
|
|
<!-- *********************************************************************** -->
|
|
|
|
<hr>
|
|
<address>
|
|
<a href="http://jigsaw.w3.org/css-validator/check/referer"><img
|
|
src="http://jigsaw.w3.org/css-validator/images/vcss-blue" alt="Valid CSS"></a>
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src="http://www.w3.org/Icons/valid-html401-blue" alt="Valid HTML 4.01"></a>
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|
|
|
<a href="mailto:sabre@nondot.org">Chris Lattner</a><br>
|
|
<a href="http://llvm.org">LLVM Compiler Infrastructure</a><br>
|
|
Last modified: $Date: 2010-04-05 06:11:11 +0200 (Mon, 05 Apr 2010) $
|
|
</address>
|
|
|
|
</body>
|
|
</html>
|