mirror of
https://github.com/RPCS3/llvm-mirror.git
synced 2024-11-23 11:13:28 +01:00
1813 lines
73 KiB
HTML
1813 lines
73 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
|
|
"http://www.w3.org/TR/html4/strict.dtd">
|
|
<html>
|
|
<head>
|
|
<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_anchors">Anchor descriptors</a></li>
|
|
<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 specifc 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>
|
|
|
|
<pre>
|
|
%llvm.dbg.object.type = type {
|
|
uint, ;; A tag
|
|
...
|
|
}
|
|
</pre>
|
|
|
|
<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_anchors">Anchor descriptors</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<pre>
|
|
%<a href="#format_anchors">llvm.dbg.anchor.type</a> = type {
|
|
uint, ;; Tag = 0 + <a href="#LLVMDebugVersion">LLVMDebugVersion</a>
|
|
uint ;; Tag of descriptors grouped by the anchor
|
|
}
|
|
</pre>
|
|
|
|
<p>One important aspect of the LLVM debug representation is that it allows the
|
|
LLVM debugger to efficiently index all of the global objects without having the
|
|
scan the program. To do this, all of the global objects use "anchor"
|
|
descriptors with designated names. All of the global objects of a particular
|
|
type (e.g., compile units) contain a pointer to the anchor. This pointer allows
|
|
a debugger to use def-use chains to find all global objects of that type.</p>
|
|
|
|
<p>The following names are recognized as anchors by LLVM:</p>
|
|
|
|
<pre>
|
|
%<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 } ;; DW_TAG_compile_unit
|
|
%<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 } ;; DW_TAG_variable
|
|
%<a href="#format_subprograms">llvm.dbg.subprograms</a> = linkonce constant %<a href="#format_anchors">llvm.dbg.anchor.type</a> { uint 0, uint 46 } ;; DW_TAG_subprogram
|
|
</pre>
|
|
|
|
<p>Using anchors in this way (where the compile unit descriptor points to the
|
|
anchors, as opposed to having a list of compile unit descriptors) allows for the
|
|
standard dead global elimination and merging passes to automatically remove
|
|
unused debugging information. If the globals were kept track of through lists,
|
|
there would always be an object pointing to the descriptors, thus would never be
|
|
deleted.</p>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<div class="doc_subsubsection">
|
|
<a name="format_compile_units">Compile unit descriptors</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<pre>
|
|
%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a> = type {
|
|
uint, ;; 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 { }*)
|
|
uint, ;; 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)")
|
|
bool ;; True if this is a main compile unit.
|
|
}
|
|
</pre>
|
|
|
|
<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.
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<div class="doc_subsubsection">
|
|
<a name="format_global_variables">Global variable descriptors</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<pre>
|
|
%<a href="#format_global_variables">llvm.dbg.global_variable.type</a> = type {
|
|
uint, ;; 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
|
|
uint, ;; Line number where defined
|
|
{ }*, ;; Reference to type descriptor
|
|
bool, ;; True if the global is local to compile unit (static)
|
|
bool, ;; True if the global is defined in the compile unit (not extern)
|
|
{ }* ;; Reference to the global variable
|
|
}
|
|
</pre>
|
|
|
|
<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">
|
|
|
|
<pre>
|
|
%<a href="#format_subprograms">llvm.dbg.subprogram.type</a> = type {
|
|
uint, ;; 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
|
|
uint, ;; Line number where defined
|
|
{ }*, ;; Reference to type descriptor
|
|
bool, ;; True if the global is local to compile unit (static)
|
|
bool ;; True if the global is defined in the compile unit (not extern)
|
|
}
|
|
</pre>
|
|
|
|
<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">
|
|
|
|
<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>
|
|
|
|
<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">
|
|
|
|
<pre>
|
|
%<a href="#format_basic_type">llvm.dbg.basictype.type</a> = type {
|
|
uint, ;; 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)
|
|
uint, ;; Line number where defined (may be 0)
|
|
i64, ;; Size in bits
|
|
i64, ;; Alignment in bits
|
|
uint, ;; Offset in bits
|
|
uint ;; Dwarf type encoding
|
|
}
|
|
</pre>
|
|
|
|
<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>
|
|
|
|
<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 class="doc_subsubsection">
|
|
<a name="format_derived_type">Derived type descriptors</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<pre>
|
|
%<a href="#format_derived_type">llvm.dbg.derivedtype.type</a> = type {
|
|
uint, ;; Tag (see below)
|
|
{ }*, ;; Reference to context
|
|
i8*, ;; Name (may be "" for anonymous types)
|
|
{ }*, ;; Reference to compile unit where defined (may be NULL)
|
|
uint, ;; Line number where defined (may be 0)
|
|
uint, ;; Size in bits
|
|
uint, ;; Alignment in bits
|
|
uint, ;; Offset in bits
|
|
{ }* ;; Reference to type derived from
|
|
}
|
|
</pre>
|
|
|
|
<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>
|
|
|
|
<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>
|
|
|
|
<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
|
|
NULL derived type.</p>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<div class="doc_subsubsection">
|
|
<a name="format_composite_type">Composite type descriptors</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<pre>
|
|
%<a href="#format_composite_type">llvm.dbg.compositetype.type</a> = type {
|
|
uint, ;; Tag (see below)
|
|
{ }*, ;; Reference to context
|
|
i8*, ;; Name (may be "" for anonymous types)
|
|
{ }*, ;; Reference to compile unit where defined (may be NULL)
|
|
uint, ;; Line number where defined (may be 0)
|
|
uint, ;; Size in bits
|
|
uint, ;; Alignment in bits
|
|
uint, ;; Offset in bits
|
|
{ }* ;; Reference to array of member descriptors
|
|
}
|
|
</pre>
|
|
|
|
<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>
|
|
|
|
<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 = 46
|
|
DW_TAG_inheritance = 26
|
|
</pre>
|
|
|
|
<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">
|
|
|
|
<pre>
|
|
%<a href="#format_subrange">llvm.dbg.subrange.type</a> = type {
|
|
uint, ;; Tag = 33 + <a href="#LLVMDebugVersion">LLVMDebugVersion</a> (DW_TAG_subrange_type)
|
|
uint, ;; Low value
|
|
uint ;; High value
|
|
}
|
|
</pre>
|
|
|
|
<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">
|
|
|
|
<pre>
|
|
%<a href="#format_enumeration">llvm.dbg.enumerator.type</a> = type {
|
|
uint, ;; Tag = 40 + <a href="#LLVMDebugVersion">LLVMDebugVersion</a> (DW_TAG_enumerator)
|
|
i8*, ;; Name
|
|
uint ;; Value
|
|
}
|
|
</pre>
|
|
|
|
<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">
|
|
<pre>
|
|
%<a href="#format_variables">llvm.dbg.variable.type</a> = type {
|
|
uint, ;; Tag (see below)
|
|
{ }*, ;; Context
|
|
i8*, ;; Name
|
|
{ }*, ;; Reference to compile unit where defined
|
|
uint, ;; Line number where defined
|
|
{ }* ;; Type descriptor
|
|
}
|
|
</pre>
|
|
|
|
<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>
|
|
|
|
<pre>
|
|
DW_TAG_auto_variable = 256
|
|
DW_TAG_arg_variable = 257
|
|
DW_TAG_return_variable = 258
|
|
</pre>
|
|
|
|
<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>
|
|
|
|
<pre>
|
|
1. void foo() {
|
|
2. int X = ...;
|
|
3. int Y = ...;
|
|
4. {
|
|
5. int Z = ...;
|
|
6. ...
|
|
7. }
|
|
8. ...
|
|
9. }
|
|
</pre>
|
|
|
|
<p>Compiled to LLVM, this function would be represented like this:</p>
|
|
|
|
<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>
|
|
|
|
<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 "MySource.cpp" and "MyHeader.h" located in the
|
|
directory "/Users/mine/sources", the following code:</p>
|
|
|
|
<pre>
|
|
#include "MyHeader.h"
|
|
|
|
int main(int argc, char *argv[]) {
|
|
return 0;
|
|
}
|
|
</pre>
|
|
|
|
<p>a C/C++ front-end would generate the following descriptors:</p>
|
|
|
|
<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 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>
|
|
|
|
<pre>
|
|
int MyGlobal = 100;
|
|
</pre>
|
|
|
|
<p>a C/C++ front-end would generate the following descriptors:</p>
|
|
|
|
<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 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>
|
|
|
|
<pre>
|
|
int main(int argc, char *argv[]) {
|
|
return 0;
|
|
}
|
|
</pre>
|
|
|
|
<p>a C/C++ front-end would generate the following descriptors:</p>
|
|
|
|
<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 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">
|
|
|
|
<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 class="doc_subsubsection">
|
|
<a name="ccxx_basic_char">char</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<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 class="doc_subsubsection">
|
|
<a name="ccxx_basic_unsigned_char">unsigned char</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<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 class="doc_subsubsection">
|
|
<a name="ccxx_basic_short">short</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<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 class="doc_subsubsection">
|
|
<a name="ccxx_basic_unsigned_short">unsigned short</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<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 class="doc_subsubsection">
|
|
<a name="ccxx_basic_int">int</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<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 class="doc_subsubsection">
|
|
<a name="ccxx_basic_unsigned_int">unsigned int</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<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 class="doc_subsubsection">
|
|
<a name="ccxx_basic_long_long">long long</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<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 class="doc_subsubsection">
|
|
<a name="ccxx_basic_unsigned_long_long">unsigned long long</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<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 class="doc_subsubsection">
|
|
<a name="ccxx_basic_float">float</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<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 class="doc_subsubsection">
|
|
<a name="ccxx_basic_double">double</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<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 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>
|
|
|
|
<pre>
|
|
typedef const int *IntPtr;
|
|
</pre>
|
|
|
|
<p>a C/C++ front-end would generate the following descriptors:</p>
|
|
|
|
<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 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>
|
|
|
|
<pre>
|
|
struct Color {
|
|
unsigned Red;
|
|
unsigned Green;
|
|
unsigned Blue;
|
|
};
|
|
</pre>
|
|
|
|
<p>a C/C++ front-end would generate the following descriptors:</p>
|
|
|
|
<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 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>
|
|
|
|
<pre>
|
|
enum Trees {
|
|
Spruce = 100,
|
|
Oak = 200,
|
|
Maple = 300
|
|
};
|
|
</pre>
|
|
|
|
<p>a C/C++ front-end would generate the following descriptors:</p>
|
|
|
|
<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>
|
|
|
|
<!-- *********************************************************************** -->
|
|
|
|
<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>
|