mirror of
https://github.com/RPCS3/llvm-mirror.git
synced 2024-11-25 04:02:41 +01:00
1874 lines
73 KiB
HTML
1874 lines
73 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
|
|
"http://www.w3.org/TR/html4/strict.dtd">
|
|
<html>
|
|
<head>
|
|
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
|
|
<title>Source Level Debugging with LLVM</title>
|
|
<link rel="stylesheet" href="llvm.css" type="text/css">
|
|
</head>
|
|
<body>
|
|
|
|
<div class="doc_title">Source Level Debugging with LLVM</div>
|
|
|
|
<table class="layout" style="width:100%">
|
|
<tr class="layout">
|
|
<td class="left">
|
|
<ul>
|
|
<li><a href="#introduction">Introduction</a>
|
|
<ol>
|
|
<li><a href="#phil">Philosophy behind LLVM debugging information</a></li>
|
|
<li><a href="#consumers">Debug information consumers</a></li>
|
|
<li><a href="#debugopt">Debugging optimized code</a></li>
|
|
</ol></li>
|
|
<li><a href="#format">Debugging information format</a>
|
|
<ol>
|
|
<li><a href="#debug_info_descriptors">Debug information descriptors</a>
|
|
<ul>
|
|
<li><a href="#format_compile_units">Compile unit descriptors</a></li>
|
|
<li><a href="#format_global_variables">Global variable descriptors</a></li>
|
|
<li><a href="#format_subprograms">Subprogram descriptors</a></li>
|
|
<li><a href="#format_blocks">Block descriptors</a></li>
|
|
<li><a href="#format_basic_type">Basic type descriptors</a></li>
|
|
<li><a href="#format_derived_type">Derived type descriptors</a></li>
|
|
<li><a href="#format_composite_type">Composite type descriptors</a></li>
|
|
<li><a href="#format_subrange">Subrange descriptors</a></li>
|
|
<li><a href="#format_enumeration">Enumerator descriptors</a></li>
|
|
<li><a href="#format_variables">Local variables</a></li>
|
|
</ul></li>
|
|
<li><a href="#format_common_intrinsics">Debugger intrinsic functions</a>
|
|
<ul>
|
|
<li><a href="#format_common_stoppoint">llvm.dbg.stoppoint</a></li>
|
|
<li><a href="#format_common_func_start">llvm.dbg.func.start</a></li>
|
|
<li><a href="#format_common_region_start">llvm.dbg.region.start</a></li>
|
|
<li><a href="#format_common_region_end">llvm.dbg.region.end</a></li>
|
|
<li><a href="#format_common_declare">llvm.dbg.declare</a></li>
|
|
</ul></li>
|
|
<li><a href="#format_common_stoppoints">Representing stopping points in the
|
|
source program</a></li>
|
|
</ol></li>
|
|
<li><a href="#ccxx_frontend">C/C++ front-end specific debug information</a>
|
|
<ol>
|
|
<li><a href="#ccxx_compile_units">C/C++ source file information</a></li>
|
|
<li><a href="#ccxx_global_variable">C/C++ global variable information</a></li>
|
|
<li><a href="#ccxx_subprogram">C/C++ function information</a></li>
|
|
<li><a href="#ccxx_basic_types">C/C++ basic types</a></li>
|
|
<li><a href="#ccxx_derived_types">C/C++ derived types</a></li>
|
|
<li><a href="#ccxx_composite_types">C/C++ struct/union types</a></li>
|
|
<li><a href="#ccxx_enumeration_types">C/C++ enumeration types</a></li>
|
|
</ol></li>
|
|
</ul>
|
|
</td>
|
|
<td class="right">
|
|
<img src="img/venusflytrap.jpg" alt="A leafy and green bug eater" width="247"
|
|
height="369">
|
|
</td>
|
|
</tr></table>
|
|
|
|
<div class="doc_author">
|
|
<p>Written by <a href="mailto:sabre@nondot.org">Chris Lattner</a>
|
|
and <a href="mailto:jlaskey@mac.com">Jim Laskey</a></p>
|
|
</div>
|
|
|
|
|
|
<!-- *********************************************************************** -->
|
|
<div class="doc_section"><a name="introduction">Introduction</a></div>
|
|
<!-- *********************************************************************** -->
|
|
|
|
<div class="doc_text">
|
|
|
|
<p>This document is the central repository for all information pertaining to
|
|
debug information in LLVM. It describes the <a href="#format">actual format
|
|
that the LLVM debug information</a> takes, which is useful for those
|
|
interested in creating front-ends or dealing directly with the information.
|
|
Further, this document provides specific examples of what debug information
|
|
for C/C++.</p>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<div class="doc_subsection">
|
|
<a name="phil">Philosophy behind LLVM debugging information</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<p>The idea of the LLVM debugging information is to capture how the important
|
|
pieces of the source-language's Abstract Syntax Tree map onto LLVM code.
|
|
Several design aspects have shaped the solution that appears here. The
|
|
important ones are:</p>
|
|
|
|
<ul>
|
|
<li>Debugging information should have very little impact on the rest of the
|
|
compiler. No transformations, analyses, or code generators should need to
|
|
be modified because of debugging information.</li>
|
|
|
|
<li>LLVM optimizations should interact in <a href="#debugopt">well-defined and
|
|
easily described ways</a> with the debugging information.</li>
|
|
|
|
<li>Because LLVM is designed to support arbitrary programming languages,
|
|
LLVM-to-LLVM tools should not need to know anything about the semantics of
|
|
the source-level-language.</li>
|
|
|
|
<li>Source-level languages are often <b>widely</b> different from one another.
|
|
LLVM should not put any restrictions of the flavor of the source-language,
|
|
and the debugging information should work with any language.</li>
|
|
|
|
<li>With code generator support, it should be possible to use an LLVM compiler
|
|
to compile a program to native machine code and standard debugging
|
|
formats. This allows compatibility with traditional machine-code level
|
|
debuggers, like GDB or DBX.</li>
|
|
</ul>
|
|
|
|
<p>The approach used by the LLVM implementation is to use a small set
|
|
of <a href="#format_common_intrinsics">intrinsic functions</a> to define a
|
|
mapping between LLVM program objects and the source-level objects. The
|
|
description of the source-level program is maintained in LLVM global
|
|
variables in an <a href="#ccxx_frontend">implementation-defined format</a>
|
|
(the C/C++ front-end currently uses working draft 7 of
|
|
the <a href="http://www.eagercon.com/dwarf/dwarf3std.htm">DWARF 3
|
|
standard</a>).</p>
|
|
|
|
<p>When a program is being debugged, a debugger interacts with the user and
|
|
turns the stored debug information into source-language specific information.
|
|
As such, a debugger must be aware of the source-language, and is thus tied to
|
|
a specific language or family of languages.</p>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<div class="doc_subsection">
|
|
<a name="consumers">Debug information consumers</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<p>The role of debug information is to provide meta information normally
|
|
stripped away during the compilation process. This meta information provides
|
|
an LLVM user a relationship between generated code and the original program
|
|
source code.</p>
|
|
|
|
<p>Currently, debug information is consumed by the DwarfWriter to produce dwarf
|
|
information used by the gdb debugger. Other targets could use the same
|
|
information to produce stabs or other debug forms.</p>
|
|
|
|
<p>It would also be reasonable to use debug information to feed profiling tools
|
|
for analysis of generated code, or, tools for reconstructing the original
|
|
source from generated code.</p>
|
|
|
|
<p>TODO - expound a bit more.</p>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<div class="doc_subsection">
|
|
<a name="debugopt">Debugging optimized code</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<p>An extremely high priority of LLVM debugging information is to make it
|
|
interact well with optimizations and analysis. In particular, the LLVM debug
|
|
information provides the following guarantees:</p>
|
|
|
|
<ul>
|
|
<li>LLVM debug information <b>always provides information to accurately read
|
|
the source-level state of the program</b>, regardless of which LLVM
|
|
optimizations have been run, and without any modification to the
|
|
optimizations themselves. However, some optimizations may impact the
|
|
ability to modify the current state of the program with a debugger, such
|
|
as setting program variables, or calling functions that have been
|
|
deleted.</li>
|
|
|
|
<li>LLVM optimizations gracefully interact with debugging information. If
|
|
they are not aware of debug information, they are automatically disabled
|
|
as necessary in the cases that would invalidate the debug info. This
|
|
retains the LLVM features, making it easy to write new
|
|
transformations.</li>
|
|
|
|
<li>As desired, LLVM optimizations can be upgraded to be aware of the LLVM
|
|
debugging information, allowing them to update the debugging information
|
|
as they perform aggressive optimizations. This means that, with effort,
|
|
the LLVM optimizers could optimize debug code just as well as non-debug
|
|
code.</li>
|
|
|
|
<li>LLVM debug information does not prevent many important optimizations from
|
|
happening (for example inlining, basic block reordering/merging/cleanup,
|
|
tail duplication, etc), further reducing the amount of the compiler that
|
|
eventually is "aware" of debugging information.</li>
|
|
|
|
<li>LLVM debug information is automatically optimized along with the rest of
|
|
the program, using existing facilities. For example, duplicate
|
|
information is automatically merged by the linker, and unused information
|
|
is automatically removed.</li>
|
|
</ul>
|
|
|
|
<p>Basically, the debug information allows you to compile a program with
|
|
"<tt>-O0 -g</tt>" and get full debug information, allowing you to arbitrarily
|
|
modify the program as it executes from a debugger. Compiling a program with
|
|
"<tt>-O3 -g</tt>" gives you full debug information that is always available
|
|
and accurate for reading (e.g., you get accurate stack traces despite tail
|
|
call elimination and inlining), but you might lose the ability to modify the
|
|
program and call functions where were optimized out of the program, or
|
|
inlined away completely.</p>
|
|
|
|
<p><a href="TestingGuide.html#quicktestsuite">LLVM test suite</a> provides a
|
|
framework to test optimizer's handling of debugging information. It can be
|
|
run like this:</p>
|
|
|
|
<div class="doc_code">
|
|
<pre>
|
|
% cd llvm/projects/test-suite/MultiSource/Benchmarks # or some other level
|
|
% make TEST=dbgopt
|
|
</pre>
|
|
</div>
|
|
|
|
<p>This will test impact of debugging information on optimization passes. If
|
|
debugging information influences optimization passes then it will be reported
|
|
as a failure. See <a href="TestingGuide.html">TestingGuide</a> for more
|
|
information on LLVM test infrastructure and how to run various tests.</p>
|
|
|
|
</div>
|
|
|
|
<!-- *********************************************************************** -->
|
|
<div class="doc_section">
|
|
<a name="format">Debugging information format</a>
|
|
</div>
|
|
<!-- *********************************************************************** -->
|
|
|
|
<div class="doc_text">
|
|
|
|
<p>LLVM debugging information has been carefully designed to make it possible
|
|
for the optimizer to optimize the program and debugging information without
|
|
necessarily having to know anything about debugging information. In
|
|
particular, the global constant merging pass automatically eliminates
|
|
duplicated debugging information (often caused by header files), the global
|
|
dead code elimination pass automatically deletes debugging information for a
|
|
function if it decides to delete the function, and the linker eliminates
|
|
debug information when it merges <tt>linkonce</tt> functions.</p>
|
|
|
|
<p>To do this, most of the debugging information (descriptors for types,
|
|
variables, functions, source files, etc) is inserted by the language
|
|
front-end in the form of LLVM global variables. These LLVM global variables
|
|
are no different from any other global variables, except that they have a web
|
|
of LLVM intrinsic functions that point to them. If the last references to a
|
|
particular piece of debugging information are deleted (for example, by the
|
|
<tt>-globaldce</tt> pass), the extraneous debug information will
|
|
automatically become dead and be removed by the optimizer.</p>
|
|
|
|
<p>Debug information is designed to be agnostic about the target debugger and
|
|
debugging information representation (e.g. DWARF/Stabs/etc). It uses a
|
|
generic machine debug information pass to decode the information that
|
|
represents variables, types, functions, namespaces, etc: this allows for
|
|
arbitrary source-language semantics and type-systems to be used, as long as
|
|
there is a module written for the target debugger to interpret the
|
|
information. In addition, debug global variables are declared in
|
|
the <tt>"llvm.metadata"</tt> section. All values declared in this section
|
|
are stripped away after target debug information is constructed and before
|
|
the program object is emitted.</p>
|
|
|
|
<p>To provide basic functionality, the LLVM debugger does have to make some
|
|
assumptions about the source-level language being debugged, though it keeps
|
|
these to a minimum. The only common features that the LLVM debugger assumes
|
|
exist are <a href="#format_compile_units">source files</a>,
|
|
and <a href="#format_global_variables">program objects</a>. These abstract
|
|
objects are used by a debugger to form stack traces, show information about
|
|
local variables, etc.</p>
|
|
|
|
<p>This section of the documentation first describes the representation aspects
|
|
common to any source-language. The <a href="#ccxx_frontend">next section</a>
|
|
describes the data layout conventions used by the C and C++ front-ends.</p>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<div class="doc_subsection">
|
|
<a name="debug_info_descriptors">Debug information descriptors</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<p>In consideration of the complexity and volume of debug information, LLVM
|
|
provides a specification for well formed debug global variables. The
|
|
constant value of each of these globals is one of a limited set of
|
|
structures, known as debug descriptors.</p>
|
|
|
|
<p>Consumers of LLVM debug information expect the descriptors for program
|
|
objects to start in a canonical format, but the descriptors can include
|
|
additional information appended at the end that is source-language
|
|
specific. All LLVM debugging information is versioned, allowing backwards
|
|
compatibility in the case that the core structures need to change in some
|
|
way. Also, all debugging information objects start with a tag to indicate
|
|
what type of object it is. The source-language is allowed to define its own
|
|
objects, by using unreserved tag numbers. We recommend using with tags in
|
|
the range 0x1000 thru 0x2000 (there is a defined enum DW_TAG_user_base =
|
|
0x1000.)</p>
|
|
|
|
<p>The fields of debug descriptors used internally by LLVM (MachineModuleInfo)
|
|
are restricted to only the simple data types <tt>int</tt>, <tt>uint</tt>,
|
|
<tt>bool</tt>, <tt>float</tt>, <tt>double</tt>, <tt>i8*</tt> and
|
|
<tt>{ }*</tt>. References to arbitrary values are handled using a
|
|
<tt>{ }*</tt> and a cast to <tt>{ }*</tt> expression; typically
|
|
references to other field descriptors, arrays of descriptors or global
|
|
variables.</p>
|
|
|
|
<div class="doc_code">
|
|
<pre>
|
|
%llvm.dbg.object.type = type {
|
|
uint, ;; A tag
|
|
...
|
|
}
|
|
</pre>
|
|
</div>
|
|
|
|
<p><a name="LLVMDebugVersion">The first field of a descriptor is always an
|
|
<tt>uint</tt> containing a tag value identifying the content of the
|
|
descriptor. The remaining fields are specific to the descriptor. The values
|
|
of tags are loosely bound to the tag values of DWARF information entries.
|
|
However, that does not restrict the use of the information supplied to DWARF
|
|
targets. To facilitate versioning of debug information, the tag is augmented
|
|
with the current debug version (LLVMDebugVersion = 4 << 16 or 0x40000 or
|
|
262144.)</a></p>
|
|
|
|
<p>The details of the various descriptors follow.</p>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<div class="doc_subsubsection">
|
|
<a name="format_compile_units">Compile unit descriptors</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<div class="doc_code">
|
|
<pre>
|
|
%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a> = type {
|
|
i32, ;; Tag = 17 + <a href="#LLVMDebugVersion">LLVMDebugVersion</a> (DW_TAG_compile_unit)
|
|
{ }*, ;; Compile unit anchor = cast = (%<a href="#format_anchors">llvm.dbg.anchor.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_units</a> to { }*)
|
|
i32, ;; DWARF language identifier (ex. DW_LANG_C89)
|
|
i8*, ;; Source file name
|
|
i8*, ;; Source file directory (includes trailing slash)
|
|
i8* ;; Producer (ex. "4.0.1 LLVM (LLVM research group)")
|
|
i1, ;; True if this is a main compile unit.
|
|
i1, ;; True if this is optimized.
|
|
i8*, ;; Flags
|
|
i32 ;; Runtime version
|
|
}
|
|
</pre>
|
|
</div>
|
|
|
|
<p>These descriptors contain a source language ID for the file (we use the DWARF
|
|
3.0 ID numbers, such as <tt>DW_LANG_C89</tt>, <tt>DW_LANG_C_plus_plus</tt>,
|
|
<tt>DW_LANG_Cobol74</tt>, etc), three strings describing the filename,
|
|
working directory of the compiler, and an identifier string for the compiler
|
|
that produced it.</p>
|
|
|
|
<p>Compile unit descriptors provide the root context for objects declared in a
|
|
specific source file. Global variables and top level functions would be
|
|
defined using this context. Compile unit descriptors also provide context
|
|
for source line correspondence.</p>
|
|
|
|
<p>Each input file is encoded as a separate compile unit in LLVM debugging
|
|
information output. However, many target specific tool chains prefer to
|
|
encode only one compile unit in an object file. In this situation, the LLVM
|
|
code generator will include debugging information entities in the compile
|
|
unit that is marked as main compile unit. The code generator accepts maximum
|
|
one main compile unit per module. If a module does not contain any main
|
|
compile unit then the code generator will emit multiple compile units in the
|
|
output object file.</p>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<div class="doc_subsubsection">
|
|
<a name="format_global_variables">Global variable descriptors</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<div class="doc_code">
|
|
<pre>
|
|
%<a href="#format_global_variables">llvm.dbg.global_variable.type</a> = type {
|
|
i32, ;; Tag = 52 + <a href="#LLVMDebugVersion">LLVMDebugVersion</a> (DW_TAG_variable)
|
|
{ }*, ;; Global variable anchor = cast (%<a href="#format_anchors">llvm.dbg.anchor.type</a>* %<a href="#format_global_variables">llvm.dbg.global_variables</a> to { }*),
|
|
{ }*, ;; Reference to context descriptor
|
|
i8*, ;; Name
|
|
i8*, ;; Display name (fully qualified C++ name)
|
|
i8*, ;; MIPS linkage name (for C++)
|
|
{ }*, ;; Reference to compile unit where defined
|
|
i32, ;; Line number where defined
|
|
{ }*, ;; Reference to type descriptor
|
|
i1, ;; True if the global is local to compile unit (static)
|
|
i1, ;; True if the global is defined in the compile unit (not extern)
|
|
{ }* ;; Reference to the global variable
|
|
}
|
|
</pre>
|
|
</div>
|
|
|
|
<p>These descriptors provide debug information about globals variables. The
|
|
provide details such as name, type and where the variable is defined.</p>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<div class="doc_subsubsection">
|
|
<a name="format_subprograms">Subprogram descriptors</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<div class="doc_code">
|
|
<pre>
|
|
%<a href="#format_subprograms">llvm.dbg.subprogram.type</a> = type {
|
|
i32, ;; Tag = 46 + <a href="#LLVMDebugVersion">LLVMDebugVersion</a> (DW_TAG_subprogram)
|
|
{ }*, ;; Subprogram anchor = cast (%<a href="#format_anchors">llvm.dbg.anchor.type</a>* %<a href="#format_subprograms">llvm.dbg.subprograms</a> to { }*),
|
|
{ }*, ;; Reference to context descriptor
|
|
i8*, ;; Name
|
|
i8*, ;; Display name (fully qualified C++ name)
|
|
i8*, ;; MIPS linkage name (for C++)
|
|
{ }*, ;; Reference to compile unit where defined
|
|
i32, ;; Line number where defined
|
|
{ }*, ;; Reference to type descriptor
|
|
i1, ;; True if the global is local to compile unit (static)
|
|
i1 ;; True if the global is defined in the compile unit (not extern)
|
|
}
|
|
</pre>
|
|
</div>
|
|
|
|
<p>These descriptors provide debug information about functions, methods and
|
|
subprograms. They provide details such as name, return types and the source
|
|
location where the subprogram is defined.</p>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<div class="doc_subsubsection">
|
|
<a name="format_blocks">Block descriptors</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<div class="doc_code">
|
|
<pre>
|
|
%<a href="#format_blocks">llvm.dbg.block</a> = type {
|
|
i32, ;; Tag = 13 + <a href="#LLVMDebugVersion">LLVMDebugVersion</a> (DW_TAG_lexical_block)
|
|
{ }* ;; Reference to context descriptor
|
|
}
|
|
</pre>
|
|
</div>
|
|
|
|
<p>These descriptors provide debug information about nested blocks within a
|
|
subprogram. The array of member descriptors is used to define local
|
|
variables and deeper nested blocks.</p>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<div class="doc_subsubsection">
|
|
<a name="format_basic_type">Basic type descriptors</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<div class="doc_code">
|
|
<pre>
|
|
%<a href="#format_basic_type">llvm.dbg.basictype.type</a> = type {
|
|
i32, ;; Tag = 36 + <a href="#LLVMDebugVersion">LLVMDebugVersion</a> (DW_TAG_base_type)
|
|
{ }*, ;; Reference to context (typically a compile unit)
|
|
i8*, ;; Name (may be "" for anonymous types)
|
|
{ }*, ;; Reference to compile unit 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>
|
|
%<a href="#format_derived_type">llvm.dbg.derivedtype.type</a> = type {
|
|
i32, ;; Tag (see below)
|
|
{ }*, ;; Reference to context
|
|
i8*, ;; Name (may be "" for anonymous types)
|
|
{ }*, ;; Reference to compile unit 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
|
|
{ }* ;; 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>
|
|
%<a href="#format_composite_type">llvm.dbg.compositetype.type</a> = type {
|
|
i32, ;; Tag (see below)
|
|
{ }*, ;; Reference to context
|
|
i8*, ;; Name (may be "" for anonymous types)
|
|
{ }*, ;; Reference to compile unit 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
|
|
{ }*, ;; Reference to type derived from
|
|
{ }*, ;; 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>
|
|
%<a href="#format_enumeration">llvm.dbg.enumerator.type</a> = type {
|
|
i32, ;; Tag = 40 + <a href="#LLVMDebugVersion">LLVMDebugVersion</a> (DW_TAG_enumerator)
|
|
i8*, ;; 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>
|
|
%<a href="#format_variables">llvm.dbg.variable.type</a> = type {
|
|
i32, ;; Tag (see below)
|
|
{ }*, ;; Context
|
|
i8*, ;; Name
|
|
{ }*, ;; Reference to compile unit where defined
|
|
i32, ;; Line number where defined
|
|
{ }* ;; 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_stoppoint">llvm.dbg.stoppoint</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
<pre>
|
|
void %<a href="#format_common_stoppoint">llvm.dbg.stoppoint</a>( uint, uint, { }* )
|
|
</pre>
|
|
|
|
<p>This intrinsic is used to provide correspondence between the source file and
|
|
the generated code. The first argument is the line number (base 1), second
|
|
argument is the column number (0 if unknown) and the third argument the
|
|
source <tt>%<a href="#format_compile_units">llvm.dbg.compile_unit</a>*</tt>
|
|
cast to a <tt>{ }*</tt>. Code following a call to this intrinsic will
|
|
have been defined in close proximity of the line, column and file. This
|
|
information holds until the next call
|
|
to <tt>%<a href="#format_common_stoppoint">lvm.dbg.stoppoint</a></tt>.</p>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<div class="doc_subsubsection">
|
|
<a name="format_common_func_start">llvm.dbg.func.start</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
<pre>
|
|
void %<a href="#format_common_func_start">llvm.dbg.func.start</a>( { }* )
|
|
</pre>
|
|
|
|
<p>This intrinsic is used to link the debug information
|
|
in <tt>%<a href="#format_subprograms">llvm.dbg.subprogram</a></tt> to the
|
|
function. It defines the beginning of the function's declarative region
|
|
(scope). It also implies a call to
|
|
%<tt><a href="#format_common_stoppoint">llvm.dbg.stoppoint</a></tt> which
|
|
defines a source line "stop point". The intrinsic should be called early in
|
|
the function after the all the alloca instructions. It should be paired off
|
|
with a closing
|
|
<tt>%<a href="#format_common_region_end">llvm.dbg.region.end</a></tt>.
|
|
The function's single argument is
|
|
the <tt>%<a href="#format_subprograms">llvm.dbg.subprogram.type</a></tt>.</p>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<div class="doc_subsubsection">
|
|
<a name="format_common_region_start">llvm.dbg.region.start</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
<pre>
|
|
void %<a href="#format_common_region_start">llvm.dbg.region.start</a>( { }* )
|
|
</pre>
|
|
|
|
<p>This intrinsic is used to define the beginning of a declarative scope (ex.
|
|
block) for local language elements. It should be paired off with a closing
|
|
<tt>%<a href="#format_common_region_end">llvm.dbg.region.end</a></tt>. The
|
|
function's single argument is
|
|
the <tt>%<a href="#format_blocks">llvm.dbg.block</a></tt> which is
|
|
starting.</p>
|
|
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<div class="doc_subsubsection">
|
|
<a name="format_common_region_end">llvm.dbg.region.end</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
<pre>
|
|
void %<a href="#format_common_region_end">llvm.dbg.region.end</a>( { }* )
|
|
</pre>
|
|
|
|
<p>This intrinsic is used to define the end of a declarative scope (ex. block)
|
|
for local language elements. It should be paired off with an
|
|
opening <tt>%<a href="#format_common_region_start">llvm.dbg.region.start</a></tt>
|
|
or <tt>%<a href="#format_common_func_start">llvm.dbg.func.start</a></tt>.
|
|
The function's single argument is either
|
|
the <tt>%<a href="#format_blocks">llvm.dbg.block</a></tt> or
|
|
the <tt>%<a href="#format_subprograms">llvm.dbg.subprogram.type</a></tt>
|
|
which is ending.</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>( { } *, { }* )
|
|
</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, also cast to a <tt>{ }*</tt>.</p>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<div class="doc_subsection">
|
|
<a name="format_common_stoppoints">
|
|
Representing stopping points in the source program
|
|
</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<p>LLVM debugger "stop points" are a key part of the debugging representation
|
|
that allows the LLVM to maintain simple semantics
|
|
for <a href="#debugopt">debugging optimized code</a>. The basic idea is that
|
|
the front-end inserts calls to
|
|
the <a href="#format_common_stoppoint">%<tt>llvm.dbg.stoppoint</tt></a>
|
|
intrinsic function at every point in the program where a debugger should be
|
|
able to inspect the program (these correspond to places a debugger stops when
|
|
you "<tt>step</tt>" through it). The front-end can choose to place these as
|
|
fine-grained as it would like (for example, before every subexpression
|
|
evaluated), but it is recommended to only put them after every source
|
|
statement that includes executable code.</p>
|
|
|
|
<p>Using calls to this intrinsic function to demark legal points for the
|
|
debugger to inspect the program automatically disables any optimizations that
|
|
could potentially confuse debugging information. To
|
|
non-debug-information-aware transformations, these calls simply look like
|
|
calls to an external function, which they must assume to do anything
|
|
(including reading or writing to any part of reachable memory). On the other
|
|
hand, it does not impact many optimizations, such as code motion of
|
|
non-trapping instructions, nor does it impact optimization of subexpressions,
|
|
code duplication transformations, or basic-block reordering
|
|
transformations.</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 lifetime
|
|
or scope 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 also 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 notion of "regions"
|
|
of a function, delineated by calls to intrinsic functions. These intrinsic
|
|
functions define new regions of the program and indicate when the region
|
|
lifetime expires. Consider the following C fragment, for example:</p>
|
|
|
|
<div class="doc_code">
|
|
<pre>
|
|
1. void foo() {
|
|
2. int X = ...;
|
|
3. int Y = ...;
|
|
4. {
|
|
5. int Z = ...;
|
|
6. ...
|
|
7. }
|
|
8. ...
|
|
9. }
|
|
</pre>
|
|
</div>
|
|
|
|
<p>Compiled to LLVM, this function would be represented like this:</p>
|
|
|
|
<div class="doc_code">
|
|
<pre>
|
|
void %foo() {
|
|
entry:
|
|
%X = alloca int
|
|
%Y = alloca int
|
|
%Z = alloca int
|
|
|
|
...
|
|
|
|
call void @<a href="#format_common_func_start">llvm.dbg.func.start</a>( %<a href="#format_subprograms">llvm.dbg.subprogram.type</a>* @llvm.dbg.subprogram )
|
|
|
|
call void @<a href="#format_common_stoppoint">llvm.dbg.stoppoint</a>( uint 2, uint 2, %<a href="#format_compile_units">llvm.dbg.compile_unit</a>* @llvm.dbg.compile_unit )
|
|
|
|
call void @<a href="#format_common_declare">llvm.dbg.declare</a>({}* %X, ...)
|
|
call void @<a href="#format_common_declare">llvm.dbg.declare</a>({}* %Y, ...)
|
|
|
|
<i>;; Evaluate expression on line 2, assigning to X.</i>
|
|
|
|
call void @<a href="#format_common_stoppoint">llvm.dbg.stoppoint</a>( uint 3, uint 2, %<a href="#format_compile_units">llvm.dbg.compile_unit</a>* @llvm.dbg.compile_unit )
|
|
|
|
<i>;; Evaluate expression on line 3, assigning to Y.</i>
|
|
|
|
call void @<a href="#format_common_stoppoint">llvm.region.start</a>()
|
|
call void @<a href="#format_common_stoppoint">llvm.dbg.stoppoint</a>( uint 5, uint 4, %<a href="#format_compile_units">llvm.dbg.compile_unit</a>* @llvm.dbg.compile_unit )
|
|
call void @<a href="#format_common_declare">llvm.dbg.declare</a>({}* %X, ...)
|
|
|
|
<i>;; Evaluate expression on line 5, assigning to Z.</i>
|
|
|
|
call void @<a href="#format_common_stoppoint">llvm.dbg.stoppoint</a>( uint 7, uint 2, %<a href="#format_compile_units">llvm.dbg.compile_unit</a>* @llvm.dbg.compile_unit )
|
|
call void @<a href="#format_common_region_end">llvm.region.end</a>()
|
|
|
|
call void @<a href="#format_common_stoppoint">llvm.dbg.stoppoint</a>( uint 9, uint 2, %<a href="#format_compile_units">llvm.dbg.compile_unit</a>* @llvm.dbg.compile_unit )
|
|
|
|
call void @<a href="#format_common_region_end">llvm.region.end</a>()
|
|
|
|
ret void
|
|
}
|
|
</pre>
|
|
</div>
|
|
|
|
<p>This example illustrates a few important details about the LLVM debugging
|
|
information. In particular, it shows how the various intrinsics are applied
|
|
together to allow a debugger to analyze the relationship between statements,
|
|
variable definitions, and the code used to implement the function.</p>
|
|
|
|
<p>The first
|
|
intrinsic <tt>%<a href="#format_common_func_start">llvm.dbg.func.start</a></tt>
|
|
provides a link with the <a href="#format_subprograms">subprogram
|
|
descriptor</a> containing the details of this function. This call also
|
|
defines the beginning of the function region, bounded by
|
|
the <tt>%<a href="#format_common_region_end">llvm.region.end</a></tt> at the
|
|
end of the function. This region is used to bracket the lifetime of
|
|
variables declared within. For a function, this outer region defines a new
|
|
stack frame whose lifetime ends when the region is ended.</p>
|
|
|
|
<p>It is possible to define inner regions for short term variables by using the
|
|
%<a href="#format_common_stoppoint"><tt>llvm.region.start</tt></a>
|
|
and <a href="#format_common_region_end"><tt>%llvm.region.end</tt></a> to
|
|
bound a region. The inner region in this example would be for the block
|
|
containing the declaration of Z.</p>
|
|
|
|
<p>Using regions to represent the boundaries of source-level functions allow
|
|
LLVM interprocedural optimizations to arbitrarily modify LLVM functions
|
|
without having to worry about breaking mapping information between the LLVM
|
|
code and the and source-level program. In particular, the inliner requires
|
|
no modification to support inlining with debugging information: there is no
|
|
explicit correlation drawn between LLVM functions and their source-level
|
|
counterparts (note however, that if the inliner inlines all instances of a
|
|
non-strong-linkage function into its caller that it will not be possible for
|
|
the user to manually invoke the inlined function from a debugger).</p>
|
|
|
|
<p>Once the function has been defined,
|
|
the <a href="#format_common_stoppoint"><tt>stopping point</tt></a>
|
|
corresponding to line #2 (column #2) of the function is encountered. At this
|
|
point in the function, <b>no</b> local variables are live. As lines 2 and 3
|
|
of the example are executed, their variable definitions are introduced into
|
|
the program using
|
|
%<a href="#format_common_declare"><tt>llvm.dbg.declare</tt></a>, without the
|
|
need to specify a new region. These variables do not require new regions to
|
|
be introduced because they go out of scope at the same point in the program:
|
|
line 9.</p>
|
|
|
|
<p>In contrast, the <tt>Z</tt> variable goes out of scope at a different time,
|
|
on line 7. For this reason, it is defined within the inner region, which
|
|
kills the availability of <tt>Z</tt> before the code for line 8 is executed.
|
|
In this way, regions can support arbitrary source-language scoping rules, as
|
|
long as they can only be nested (ie, one scope cannot partially overlap with
|
|
a part of another scope).</p>
|
|
|
|
<p>It is worth noting that this scoping mechanism is used to control scoping of
|
|
all declarations, not just variable declarations. For example, the scope of
|
|
a C++ using declaration is controlled with this and could change how name
|
|
lookup is performed.</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 types used. In this case we need one for compile unit anchors and one
|
|
;; for compile units.
|
|
;;
|
|
%<a href="#format_anchors">llvm.dbg.anchor.type</a> = type { uint, uint }
|
|
%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a> = type { uint, { }*, uint, uint, i8*, i8*, i8* }
|
|
...
|
|
;;
|
|
;; Define the anchor for compile units. Note that the second field of the
|
|
;; anchor is 17, which is the same as the tag for compile units
|
|
;; (17 = DW_TAG_compile_unit.)
|
|
;;
|
|
%<a href="#format_compile_units">llvm.dbg.compile_units</a> = linkonce constant %<a href="#format_anchors">llvm.dbg.anchor.type</a> { uint 0, uint 17 }, section "llvm.metadata"
|
|
|
|
;;
|
|
;; Define the compile unit for the source file "/Users/mine/sources/MySource.cpp".
|
|
;;
|
|
%<a href="#format_compile_units">llvm.dbg.compile_unit1</a> = internal constant %<a href="#format_compile_units">llvm.dbg.compile_unit.type</a> {
|
|
uint add(uint 17, uint 262144),
|
|
{ }* cast (%<a href="#format_anchors">llvm.dbg.anchor.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_units</a> to { }*),
|
|
uint 1,
|
|
uint 1,
|
|
i8* getelementptr ([13 x i8]* %str1, i32 0, i32 0),
|
|
i8* getelementptr ([21 x i8]* %str2, i32 0, i32 0),
|
|
i8* getelementptr ([33 x i8]* %str3, i32 0, i32 0) }, section "llvm.metadata"
|
|
|
|
;;
|
|
;; Define the compile unit for the header file "/Users/mine/sources/MyHeader.h".
|
|
;;
|
|
%<a href="#format_compile_units">llvm.dbg.compile_unit2</a> = internal constant %<a href="#format_compile_units">llvm.dbg.compile_unit.type</a> {
|
|
uint add(uint 17, uint 262144),
|
|
{ }* cast (%<a href="#format_anchors">llvm.dbg.anchor.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_units</a> to { }*),
|
|
uint 1,
|
|
uint 1,
|
|
i8* getelementptr ([11 x i8]* %str4, int 0, int 0),
|
|
i8* getelementptr ([21 x i8]* %str2, int 0, int 0),
|
|
i8* getelementptr ([33 x i8]* %str3, int 0, int 0) }, section "llvm.metadata"
|
|
|
|
;;
|
|
;; Define each of the strings used in the compile units.
|
|
;;
|
|
%str1 = internal constant [13 x i8] c"MySource.cpp\00", section "llvm.metadata";
|
|
%str2 = internal constant [21 x i8] c"/Users/mine/sources/\00", section "llvm.metadata";
|
|
%str3 = internal constant [33 x i8] c"4.0.1 LLVM (LLVM research group)\00", section "llvm.metadata";
|
|
%str4 = internal constant [11 x i8] c"MyHeader.h\00", section "llvm.metadata";
|
|
...
|
|
</pre>
|
|
</div>
|
|
|
|
</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 types used. One for global variable anchors, one for the global
|
|
;; variable descriptor, one for the global's basic type and one for the global's
|
|
;; compile unit.
|
|
;;
|
|
%<a href="#format_anchors">llvm.dbg.anchor.type</a> = type { uint, uint }
|
|
%<a href="#format_global_variables">llvm.dbg.global_variable.type</a> = type { uint, { }*, { }*, i8*, { }*, uint, { }*, bool, bool, { }*, uint }
|
|
%<a href="#format_basic_type">llvm.dbg.basictype.type</a> = type { uint, { }*, i8*, { }*, int, uint, uint, uint, uint }
|
|
%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a> = ...
|
|
...
|
|
;;
|
|
;; Define the global itself.
|
|
;;
|
|
%MyGlobal = global int 100
|
|
...
|
|
;;
|
|
;; Define the anchor for global variables. Note that the second field of the
|
|
;; anchor is 52, which is the same as the tag for global variables
|
|
;; (52 = DW_TAG_variable.)
|
|
;;
|
|
%<a href="#format_global_variables">llvm.dbg.global_variables</a> = linkonce constant %<a href="#format_anchors">llvm.dbg.anchor.type</a> { uint 0, uint 52 }, section "llvm.metadata"
|
|
|
|
;;
|
|
;; Define the global variable descriptor. Note the reference to the global
|
|
;; variable anchor and the global variable itself.
|
|
;;
|
|
%<a href="#format_global_variables">llvm.dbg.global_variable</a> = internal constant %<a href="#format_global_variables">llvm.dbg.global_variable.type</a> {
|
|
uint add(uint 52, uint 262144),
|
|
{ }* cast (%<a href="#format_anchors">llvm.dbg.anchor.type</a>* %<a href="#format_global_variables">llvm.dbg.global_variables</a> to { }*),
|
|
{ }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to { }*),
|
|
i8* getelementptr ([9 x i8]* %str1, int 0, int 0),
|
|
i8* getelementptr ([1 x i8]* %str2, int 0, int 0),
|
|
{ }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to { }*),
|
|
uint 1,
|
|
{ }* cast (%<a href="#format_basic_type">llvm.dbg.basictype.type</a>* %<a href="#format_basic_type">llvm.dbg.basictype</a> to { }*),
|
|
bool false,
|
|
bool true,
|
|
{ }* cast (int* %MyGlobal to { }*) }, section "llvm.metadata"
|
|
|
|
;;
|
|
;; 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.
|
|
;;
|
|
%<a href="#format_basic_type">llvm.dbg.basictype</a> = internal constant %<a href="#format_basic_type">llvm.dbg.basictype.type</a> {
|
|
uint add(uint 36, uint 262144),
|
|
{ }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to { }*),
|
|
i8* getelementptr ([4 x i8]* %str3, int 0, int 0),
|
|
{ }* null,
|
|
int 0,
|
|
uint 32,
|
|
uint 32,
|
|
uint 0,
|
|
uint 5 }, section "llvm.metadata"
|
|
|
|
;;
|
|
;; Define the names of the global variable and basic type.
|
|
;;
|
|
%str1 = internal constant [9 x i8] c"MyGlobal\00", section "llvm.metadata"
|
|
%str2 = internal constant [1 x i8] c"\00", section "llvm.metadata"
|
|
%str3 = internal constant [4 x i8] c"int\00", section "llvm.metadata"
|
|
</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 types used. One for subprogram anchors, one for the subprogram
|
|
;; descriptor, one for the global's basic type and one for the subprogram's
|
|
;; compile unit.
|
|
;;
|
|
%<a href="#format_subprograms">llvm.dbg.subprogram.type</a> = type { uint, { }*, { }*, i8*, { }*, bool, bool }
|
|
%<a href="#format_anchors">llvm.dbg.anchor.type</a> = type { uint, uint }
|
|
%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a> = ...
|
|
|
|
;;
|
|
;; 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.)
|
|
;;
|
|
%<a href="#format_subprograms">llvm.dbg.subprograms</a> = linkonce constant %<a href="#format_anchors">llvm.dbg.anchor.type</a> { uint 0, uint 46 }, section "llvm.metadata"
|
|
|
|
;;
|
|
;; Define the descriptor for the subprogram. TODO - more details.
|
|
;;
|
|
%<a href="#format_subprograms">llvm.dbg.subprogram</a> = internal constant %<a href="#format_subprograms">llvm.dbg.subprogram.type</a> {
|
|
uint add(uint 46, uint 262144),
|
|
{ }* cast (%<a href="#format_anchors">llvm.dbg.anchor.type</a>* %<a href="#format_subprograms">llvm.dbg.subprograms</a> to { }*),
|
|
{ }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to { }*),
|
|
i8* getelementptr ([5 x i8]* %str1, int 0, int 0),
|
|
i8* getelementptr ([1 x i8]* %str2, int 0, int 0),
|
|
{ }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to { }*),
|
|
uint 1,
|
|
{ }* null,
|
|
bool false,
|
|
bool true }, section "llvm.metadata"
|
|
|
|
;;
|
|
;; Define the name of the subprogram.
|
|
;;
|
|
%str1 = internal constant [5 x i8] c"main\00", section "llvm.metadata"
|
|
%str2 = internal constant [1 x i8] c"\00", section "llvm.metadata"
|
|
|
|
;;
|
|
;; Define the subprogram itself.
|
|
;;
|
|
int %main(int %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>
|
|
%<a href="#format_basic_type">llvm.dbg.basictype</a> = internal constant %<a href="#format_basic_type">llvm.dbg.basictype.type</a> {
|
|
uint add(uint 36, uint 262144),
|
|
{ }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to { }*),
|
|
i8* getelementptr ([5 x i8]* %str1, int 0, int 0),
|
|
{ }* null,
|
|
int 0,
|
|
uint 32,
|
|
uint 32,
|
|
uint 0,
|
|
uint 2 }, section "llvm.metadata"
|
|
%str1 = internal constant [5 x i8] c"bool\00", section "llvm.metadata"
|
|
</pre>
|
|
</div>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<div class="doc_subsubsection">
|
|
<a name="ccxx_basic_char">char</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<div class="doc_code">
|
|
<pre>
|
|
%<a href="#format_basic_type">llvm.dbg.basictype</a> = internal constant %<a href="#format_basic_type">llvm.dbg.basictype.type</a> {
|
|
uint add(uint 36, uint 262144),
|
|
{ }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to { }*),
|
|
i8* getelementptr ([5 x i8]* %str1, int 0, int 0),
|
|
{ }* null,
|
|
int 0,
|
|
uint 8,
|
|
uint 8,
|
|
uint 0,
|
|
uint 6 }, section "llvm.metadata"
|
|
%str1 = internal constant [5 x i8] c"char\00", section "llvm.metadata"
|
|
</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>
|
|
%<a href="#format_basic_type">llvm.dbg.basictype</a> = internal constant %<a href="#format_basic_type">llvm.dbg.basictype.type</a> {
|
|
uint add(uint 36, uint 262144),
|
|
{ }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to { }*),
|
|
i8* getelementptr ([14 x i8]* %str1, int 0, int 0),
|
|
{ }* null,
|
|
int 0,
|
|
uint 8,
|
|
uint 8,
|
|
uint 0,
|
|
uint 8 }, section "llvm.metadata"
|
|
%str1 = internal constant [14 x i8] c"unsigned char\00", section "llvm.metadata"
|
|
</pre>
|
|
</div>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<div class="doc_subsubsection">
|
|
<a name="ccxx_basic_short">short</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<div class="doc_code">
|
|
<pre>
|
|
%<a href="#format_basic_type">llvm.dbg.basictype</a> = internal constant %<a href="#format_basic_type">llvm.dbg.basictype.type</a> {
|
|
uint add(uint 36, uint 262144),
|
|
{ }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to { }*),
|
|
i8* getelementptr ([10 x i8]* %str1, int 0, int 0),
|
|
{ }* null,
|
|
int 0,
|
|
uint 16,
|
|
uint 16,
|
|
uint 0,
|
|
uint 5 }, section "llvm.metadata"
|
|
%str1 = internal constant [10 x i8] c"short int\00", section "llvm.metadata"
|
|
</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>
|
|
%<a href="#format_basic_type">llvm.dbg.basictype</a> = internal constant %<a href="#format_basic_type">llvm.dbg.basictype.type</a> {
|
|
uint add(uint 36, uint 262144),
|
|
{ }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to { }*),
|
|
i8* getelementptr ([19 x i8]* %str1, int 0, int 0),
|
|
{ }* null,
|
|
int 0,
|
|
uint 16,
|
|
uint 16,
|
|
uint 0,
|
|
uint 7 }, section "llvm.metadata"
|
|
%str1 = internal constant [19 x i8] c"short unsigned int\00", section "llvm.metadata"
|
|
</pre>
|
|
</div>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<div class="doc_subsubsection">
|
|
<a name="ccxx_basic_int">int</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<div class="doc_code">
|
|
<pre>
|
|
%<a href="#format_basic_type">llvm.dbg.basictype</a> = internal constant %<a href="#format_basic_type">llvm.dbg.basictype.type</a> {
|
|
uint add(uint 36, uint 262144),
|
|
{ }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to { }*),
|
|
i8* getelementptr ([4 x i8]* %str1, int 0, int 0),
|
|
{ }* null,
|
|
int 0,
|
|
uint 32,
|
|
uint 32,
|
|
uint 0,
|
|
uint 5 }, section "llvm.metadata"
|
|
%str1 = internal constant [4 x i8] c"int\00", section "llvm.metadata"
|
|
</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>
|
|
%<a href="#format_basic_type">llvm.dbg.basictype</a> = internal constant %<a href="#format_basic_type">llvm.dbg.basictype.type</a> {
|
|
uint add(uint 36, uint 262144),
|
|
{ }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to { }*),
|
|
i8* getelementptr ([13 x i8]* %str1, int 0, int 0),
|
|
{ }* null,
|
|
int 0,
|
|
uint 32,
|
|
uint 32,
|
|
uint 0,
|
|
uint 7 }, section "llvm.metadata"
|
|
%str1 = internal constant [13 x i8] c"unsigned int\00", section "llvm.metadata"
|
|
</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>
|
|
%<a href="#format_basic_type">llvm.dbg.basictype</a> = internal constant %<a href="#format_basic_type">llvm.dbg.basictype.type</a> {
|
|
uint add(uint 36, uint 262144),
|
|
{ }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to { }*),
|
|
i8* getelementptr ([14 x i8]* %str1, int 0, int 0),
|
|
{ }* null,
|
|
int 0,
|
|
uint 64,
|
|
uint 64,
|
|
uint 0,
|
|
uint 5 }, section "llvm.metadata"
|
|
%str1 = internal constant [14 x i8] c"long long int\00", section "llvm.metadata"
|
|
</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>
|
|
%<a href="#format_basic_type">llvm.dbg.basictype</a> = internal constant %<a href="#format_basic_type">llvm.dbg.basictype.type</a> {
|
|
uint add(uint 36, uint 262144),
|
|
{ }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to { }*),
|
|
i8* getelementptr ([23 x i8]* %str1, int 0, int 0),
|
|
{ }* null,
|
|
int 0,
|
|
uint 64,
|
|
uint 64,
|
|
uint 0,
|
|
uint 7 }, section "llvm.metadata"
|
|
%str1 = internal constant [23 x 8] c"long long unsigned int\00", section "llvm.metadata"
|
|
</pre>
|
|
</div>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<div class="doc_subsubsection">
|
|
<a name="ccxx_basic_float">float</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<div class="doc_code">
|
|
<pre>
|
|
%<a href="#format_basic_type">llvm.dbg.basictype</a> = internal constant %<a href="#format_basic_type">llvm.dbg.basictype.type</a> {
|
|
uint add(uint 36, uint 262144),
|
|
{ }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to { }*),
|
|
i8* getelementptr ([6 x i8]* %str1, int 0, int 0),
|
|
{ }* null,
|
|
int 0,
|
|
uint 32,
|
|
uint 32,
|
|
uint 0,
|
|
uint 4 }, section "llvm.metadata"
|
|
%str1 = internal constant [6 x i8] c"float\00", section "llvm.metadata"
|
|
</pre>
|
|
</div>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<div class="doc_subsubsection">
|
|
<a name="ccxx_basic_double">double</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<div class="doc_code">
|
|
<pre>
|
|
%<a href="#format_basic_type">llvm.dbg.basictype</a> = internal constant %<a href="#format_basic_type">llvm.dbg.basictype.type</a> {
|
|
uint add(uint 36, uint 262144),
|
|
{ }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to { }*),
|
|
8* getelementptr ([7 x 8]* %str1, int 0, int 0),
|
|
{ }* null,
|
|
int 0,
|
|
uint 64,
|
|
uint 64,
|
|
uint 0,
|
|
uint 4 }, section "llvm.metadata"
|
|
%str1 = internal constant [7 x 8] c"double\00", section "llvm.metadata"
|
|
</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".
|
|
;;
|
|
%<a href="#format_derived_type">llvm.dbg.derivedtype1</a> = internal constant %<a href="#format_derived_type">llvm.dbg.derivedtype.type</a> {
|
|
uint add(uint 22, uint 262144),
|
|
{ }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to { }*),
|
|
i8* getelementptr ([7 x 8]* %str1, int 0, int 0),
|
|
{ }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to { }*),
|
|
int 1,
|
|
uint 0,
|
|
uint 0,
|
|
uint 0,
|
|
{ }* cast (%<a href="#format_derived_type">llvm.dbg.derivedtype.type</a>* %<a href="#format_derived_type">llvm.dbg.derivedtype2</a> to { }*) }, section "llvm.metadata"
|
|
%str1 = internal constant [7 x 8] c"IntPtr\00", section "llvm.metadata"
|
|
|
|
;;
|
|
;; Define the pointer type.
|
|
;;
|
|
%<a href="#format_derived_type">llvm.dbg.derivedtype2</a> = internal constant %<a href="#format_derived_type">llvm.dbg.derivedtype.type</a> {
|
|
uint add(uint 15, uint 262144),
|
|
{ }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to { }*),
|
|
i8* null,
|
|
{ }* null,
|
|
int 0,
|
|
uint 32,
|
|
uint 32,
|
|
uint 0,
|
|
{ }* cast (%<a href="#format_derived_type">llvm.dbg.derivedtype.type</a>* %<a href="#format_derived_type">llvm.dbg.derivedtype3</a> to { }*) }, section "llvm.metadata"
|
|
|
|
;;
|
|
;; Define the const type.
|
|
;;
|
|
%<a href="#format_derived_type">llvm.dbg.derivedtype3</a> = internal constant %<a href="#format_derived_type">llvm.dbg.derivedtype.type</a> {
|
|
uint add(uint 38, uint 262144),
|
|
{ }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to { }*),
|
|
i8* null,
|
|
{ }* null,
|
|
int 0,
|
|
uint 0,
|
|
uint 0,
|
|
uint 0,
|
|
{ }* cast (%<a href="#format_basic_type">llvm.dbg.basictype.type</a>* %<a href="#format_basic_type">llvm.dbg.basictype1</a> to { }*) }, section "llvm.metadata"
|
|
|
|
;;
|
|
;; Define the int type.
|
|
;;
|
|
%<a href="#format_basic_type">llvm.dbg.basictype1</a> = internal constant %<a href="#format_basic_type">llvm.dbg.basictype.type</a> {
|
|
uint add(uint 36, uint 262144),
|
|
{ }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to { }*),
|
|
8* getelementptr ([4 x 8]* %str2, int 0, int 0),
|
|
{ }* null,
|
|
int 0,
|
|
uint 32,
|
|
uint 32,
|
|
uint 0,
|
|
uint 5 }, section "llvm.metadata"
|
|
%str2 = internal constant [4 x 8] c"int\00", section "llvm.metadata"
|
|
</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.
|
|
;;
|
|
%<a href="#format_basic_type">llvm.dbg.basictype</a> = internal constant %<a href="#format_basic_type">llvm.dbg.basictype.type</a> {
|
|
uint add(uint 36, uint 262144),
|
|
{ }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to { }*),
|
|
i8* getelementptr ([13 x i8]* %str1, int 0, int 0),
|
|
{ }* null,
|
|
int 0,
|
|
uint 32,
|
|
uint 32,
|
|
uint 0,
|
|
uint 7 }, section "llvm.metadata"
|
|
%str1 = internal constant [13 x i8] c"unsigned int\00", section "llvm.metadata"
|
|
|
|
;;
|
|
;; Define composite type for struct Color.
|
|
;;
|
|
%<a href="#format_composite_type">llvm.dbg.compositetype</a> = internal constant %<a href="#format_composite_type">llvm.dbg.compositetype.type</a> {
|
|
uint add(uint 19, uint 262144),
|
|
{ }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to { }*),
|
|
i8* getelementptr ([6 x i8]* %str2, int 0, int 0),
|
|
{ }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to { }*),
|
|
int 1,
|
|
uint 96,
|
|
uint 32,
|
|
uint 0,
|
|
{ }* null,
|
|
{ }* cast ([3 x { }*]* %llvm.dbg.array to { }*) }, section "llvm.metadata"
|
|
%str2 = internal constant [6 x i8] c"Color\00", section "llvm.metadata"
|
|
|
|
;;
|
|
;; Define the Red field.
|
|
;;
|
|
%<a href="#format_derived_type">llvm.dbg.derivedtype1</a> = internal constant %<a href="#format_derived_type">llvm.dbg.derivedtype.type</a> {
|
|
uint add(uint 13, uint 262144),
|
|
{ }* null,
|
|
i8* getelementptr ([4 x i8]* %str3, int 0, int 0),
|
|
{ }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to { }*),
|
|
int 2,
|
|
uint 32,
|
|
uint 32,
|
|
uint 0,
|
|
{ }* cast (%<a href="#format_basic_type">llvm.dbg.basictype.type</a>* %<a href="#format_basic_type">llvm.dbg.basictype</a> to { }*) }, section "llvm.metadata"
|
|
%str3 = internal constant [4 x i8] c"Red\00", section "llvm.metadata"
|
|
|
|
;;
|
|
;; Define the Green field.
|
|
;;
|
|
%<a href="#format_derived_type">llvm.dbg.derivedtype2</a> = internal constant %<a href="#format_derived_type">llvm.dbg.derivedtype.type</a> {
|
|
uint add(uint 13, uint 262144),
|
|
{ }* null,
|
|
i8* getelementptr ([6 x i8]* %str4, int 0, int 0),
|
|
{ }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to { }*),
|
|
int 3,
|
|
uint 32,
|
|
uint 32,
|
|
uint 32,
|
|
{ }* cast (%<a href="#format_basic_type">llvm.dbg.basictype.type</a>* %<a href="#format_basic_type">llvm.dbg.basictype</a> to { }*) }, section "llvm.metadata"
|
|
%str4 = internal constant [6 x i8] c"Green\00", section "llvm.metadata"
|
|
|
|
;;
|
|
;; Define the Blue field.
|
|
;;
|
|
%<a href="#format_derived_type">llvm.dbg.derivedtype3</a> = internal constant %<a href="#format_derived_type">llvm.dbg.derivedtype.type</a> {
|
|
uint add(uint 13, uint 262144),
|
|
{ }* null,
|
|
i8* getelementptr ([5 x i8]* %str5, int 0, int 0),
|
|
{ }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to { }*),
|
|
int 4,
|
|
uint 32,
|
|
uint 32,
|
|
uint 64,
|
|
{ }* cast (%<a href="#format_basic_type">llvm.dbg.basictype.type</a>* %<a href="#format_basic_type">llvm.dbg.basictype</a> to { }*) }, section "llvm.metadata"
|
|
%str5 = internal constant [5 x 8] c"Blue\00", section "llvm.metadata"
|
|
|
|
;;
|
|
;; Define the array of fields used by the composite type Color.
|
|
;;
|
|
%llvm.dbg.array = internal constant [3 x { }*] [
|
|
{ }* cast (%<a href="#format_derived_type">llvm.dbg.derivedtype.type</a>* %<a href="#format_derived_type">llvm.dbg.derivedtype1</a> to { }*),
|
|
{ }* cast (%<a href="#format_derived_type">llvm.dbg.derivedtype.type</a>* %<a href="#format_derived_type">llvm.dbg.derivedtype2</a> to { }*),
|
|
{ }* cast (%<a href="#format_derived_type">llvm.dbg.derivedtype.type</a>* %<a href="#format_derived_type">llvm.dbg.derivedtype3</a> to { }*) ], section "llvm.metadata"
|
|
</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
|
|
;;
|
|
%<a href="#format_composite_type">llvm.dbg.compositetype</a> = internal constant %<a href="#format_composite_type">llvm.dbg.compositetype.type</a> {
|
|
uint add(uint 4, uint 262144),
|
|
{ }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to { }*),
|
|
i8* getelementptr ([6 x i8]* %str1, int 0, int 0),
|
|
{ }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to { }*),
|
|
int 1,
|
|
uint 32,
|
|
uint 32,
|
|
uint 0,
|
|
{ }* null,
|
|
{ }* cast ([3 x { }*]* %llvm.dbg.array to { }*) }, section "llvm.metadata"
|
|
%str1 = internal constant [6 x i8] c"Trees\00", section "llvm.metadata"
|
|
|
|
;;
|
|
;; Define Spruce enumerator.
|
|
;;
|
|
%<a href="#format_enumeration">llvm.dbg.enumerator1</a> = internal constant %<a href="#format_enumeration">llvm.dbg.enumerator.type</a> {
|
|
uint add(uint 40, uint 262144),
|
|
i8* getelementptr ([7 x i8]* %str2, int 0, int 0),
|
|
int 100 }, section "llvm.metadata"
|
|
%str2 = internal constant [7 x i8] c"Spruce\00", section "llvm.metadata"
|
|
|
|
;;
|
|
;; Define Oak enumerator.
|
|
;;
|
|
%<a href="#format_enumeration">llvm.dbg.enumerator2</a> = internal constant %<a href="#format_enumeration">llvm.dbg.enumerator.type</a> {
|
|
uint add(uint 40, uint 262144),
|
|
i8* getelementptr ([4 x i8]* %str3, int 0, int 0),
|
|
int 200 }, section "llvm.metadata"
|
|
%str3 = internal constant [4 x i8] c"Oak\00", section "llvm.metadata"
|
|
|
|
;;
|
|
;; Define Maple enumerator.
|
|
;;
|
|
%<a href="#format_enumeration">llvm.dbg.enumerator3</a> = internal constant %<a href="#format_enumeration">llvm.dbg.enumerator.type</a> {
|
|
uint add(uint 40, uint 262144),
|
|
i8* getelementptr ([6 x i8]* %str4, int 0, int 0),
|
|
int 300 }, section "llvm.metadata"
|
|
%str4 = internal constant [6 x i8] c"Maple\00", section "llvm.metadata"
|
|
|
|
;;
|
|
;; Define the array of enumerators used by composite type Trees.
|
|
;;
|
|
%llvm.dbg.array = internal constant [3 x { }*] [
|
|
{ }* cast (%<a href="#format_enumeration">llvm.dbg.enumerator.type</a>* %<a href="#format_enumeration">llvm.dbg.enumerator1</a> to { }*),
|
|
{ }* cast (%<a href="#format_enumeration">llvm.dbg.enumerator.type</a>* %<a href="#format_enumeration">llvm.dbg.enumerator2</a> to { }*),
|
|
{ }* cast (%<a href="#format_enumeration">llvm.dbg.enumerator.type</a>* %<a href="#format_enumeration">llvm.dbg.enumerator3</a> to { }*) ], section "llvm.metadata"
|
|
</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>
|
|
<a href="http://validator.w3.org/check/referer"><img
|
|
src="http://www.w3.org/Icons/valid-html401-blue" alt="Valid HTML 4.01"></a>
|
|
|
|
<a href="mailto:sabre@nondot.org">Chris Lattner</a><br>
|
|
<a href="http://llvm.org">LLVM Compiler Infrastructure</a><br>
|
|
Last modified: $Date$
|
|
</address>
|
|
|
|
</body>
|
|
</html>
|