</head>
<body>
-<div class="doc_title">Source Level Debugging with LLVM</div>
+<h1>Source Level Debugging with LLVM</h1>
<table class="layout" style="width:100%">
<tr class="layout">
<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_files">File 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_common_intrinsics">Debugger intrinsic functions</a>
<ul>
<li><a href="#format_common_declare">llvm.dbg.declare</a></li>
+ <li><a href="#format_common_value">llvm.dbg.value</a></li>
</ul></li>
</ol></li>
<li><a href="#format_common_lifetime">Object lifetimes and scoping</a></li>
<!-- *********************************************************************** -->
-<div class="doc_section"><a name="introduction">Introduction</a></div>
+<h2><a name="introduction">Introduction</a></h2>
<!-- *********************************************************************** -->
-<div class="doc_text">
+<div>
<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>
+ for C/C++ looks like.</p>
<!-- ======================================================================= -->
-<div class="doc_subsection">
+<h3>
<a name="phil">Philosophy behind LLVM debugging information</a>
-</div>
+</h3>
-<div class="doc_text">
+<div>
<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.
</div>
<!-- ======================================================================= -->
-<div class="doc_subsection">
+<h3>
<a name="consumers">Debug information consumers</a>
-</div>
+</h3>
-<div class="doc_text">
+<div>
<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
+<p>Currently, debug information is consumed by DwarfDebug to produce dwarf
information used by the gdb debugger. Other targets could use the same
information to produce stabs or other debug forms.</p>
</div>
<!-- ======================================================================= -->
-<div class="doc_subsection">
+<h3>
<a name="debugopt">Debugging optimized code</a>
-</div>
+</h3>
-<div class="doc_text">
+<div>
<p>An extremely high priority of LLVM debugging information is to make it
interact well with optimizations and analysis. In particular, the LLVM debug
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
+ <li>LLVM debug information does not prevent 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>
+ tail duplication, etc).</li>
<li>LLVM debug information is automatically optimized along with the rest of
the program, using existing facilities. For example, duplicate
</div>
+</div>
+
<!-- *********************************************************************** -->
-<div class="doc_section">
+<h2>
<a name="format">Debugging information format</a>
-</div>
+</h2>
<!-- *********************************************************************** -->
-<div class="doc_text">
+<div>
<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, te use of metadadta avoids duplicated dubgging information from
+ particular, the use of metadata avoids duplicated debugging information from
the beginning, and the global dead code elimination pass automatically
deletes debugging information for a function if it decides to delete the
function. </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>,
+ exist are <a href="#format_files">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>
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">
+<h3>
<a name="debug_info_descriptors">Debug information descriptors</a>
-</div>
+</h3>
-<div class="doc_text">
+<div>
<p>In consideration of the complexity and volume of debug information, LLVM
provides a specification for well formed debug descriptors. </p>
0x1000.)</p>
<p>The fields of debug descriptors used internally by LLVM
- are restricted to only the simple data types <tt>int</tt>, <tt>uint</tt>,
- <tt>bool</tt>, <tt>float</tt>, <tt>double</tt>, <tt>mdstring</tt> and
- <tt>mdnode</tt>. </p>
+ are restricted to only the simple data types <tt>i32</tt>, <tt>i1</tt>,
+ <tt>float</tt>, <tt>double</tt>, <tt>mdstring</tt> and <tt>mdnode</tt>. </p>
<div class="doc_code">
<pre>
!1 = metadata !{
- uint, ;; A tag
+ i32, ;; 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
+ <tt>i32</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 = 7 << 16 or 0x70000 or
- 458752.)</a></p>
+ with the current debug version (LLVMDebugVersion = 8 << 16 or
+ 0x80000 or 524288.)</a></p>
<p>The details of the various descriptors follow.</p>
-</div>
-
<!-- ======================================================================= -->
-<div class="doc_subsubsection">
+<h4>
<a name="format_compile_units">Compile unit descriptors</a>
-</div>
+</h4>
-<div class="doc_text">
+<div>
<div class="doc_code">
<pre>
i1, ;; True if this is optimized.
metadata, ;; Flags
i32 ;; Runtime version
+ metadata ;; List of enums types
+ metadata ;; List of retained types
+ metadata ;; List of subprograms
+ metadata ;; List of global variables
}
</pre>
</div>
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>
+ specific compilation unit. File descriptors are defined using this context.
+ These descriptors are collected by a named metadata
+ <tt>!llvm.dbg.cu</tt>. Compile unit descriptor keeps track of subprograms,
+ global variables and type information.
+
+</div>
+
+<!-- ======================================================================= -->
+<h4>
+ <a name="format_files">File descriptors</a>
+</h4>
+
+<div>
+
+<div class="doc_code">
+<pre>
+!0 = metadata !{
+ i32, ;; Tag = 41 + <a href="#LLVMDebugVersion">LLVMDebugVersion</a>
+ ;; (DW_TAG_file_type)
+ metadata, ;; Source file name
+ metadata, ;; Source file directory (includes trailing slash)
+ metadata ;; Unused
+}
+</pre>
+</div>
+
+<p>These descriptors contain information for a file. Global variables and top
+ level functions would be defined using this context.k File 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>
+<p>Each input file is encoded as a separate file descriptor in LLVM debugging
+ information output. </p>
</div>
<!-- ======================================================================= -->
-<div class="doc_subsubsection">
+<h4>
<a name="format_global_variables">Global variable descriptors</a>
-</div>
+</h4>
-<div class="doc_text">
+<div>
<div class="doc_code">
<pre>
metadata, ;; Name
metadata, ;; Display name (fully qualified C++ name)
metadata, ;; MIPS linkage name (for C++)
- metadata, ;; Reference to compile unit where defined
+ metadata, ;; Reference to file where defined
i32, ;; Line number where defined
metadata, ;; 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
+ {}* ;; 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>
+provide details such as name, type and where the variable is defined. All
+global variables are collected by named metadata <tt>!llvm.dbg.gv</tt>.</p>
</div>
<!-- ======================================================================= -->
-<div class="doc_subsubsection">
+<h4>
<a name="format_subprograms">Subprogram descriptors</a>
-</div>
+</h4>
-<div class="doc_text">
+<div>
<div class="doc_code">
<pre>
metadata, ;; Name
metadata, ;; Display name (fully qualified C++ name)
metadata, ;; MIPS linkage name (for C++)
- metadata, ;; Reference to compile unit where defined
+ metadata, ;; Reference to file where defined
i32, ;; Line number where defined
metadata, ;; 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)
+ i1, ;; True if the global is defined in the compile unit (not extern)
+ i32, ;; Virtuality, e.g. dwarf::DW_VIRTUALITY__virtual
+ i32, ;; Index into a virtual function
+ metadata, ;; indicates which base type contains the vtable pointer for the
+ ;; derived class
+ i1, ;; isArtificial
+ i1, ;; isOptimized
+ Function *,;; Pointer to LLVM function
+ metadata, ;; Lists function template parameters
+ metadata ;; Function declaration descriptor
+ metadata ;; List of function variables
}
</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>
+ location where the subprogram is defined.
+ All subprogram descriptors are collected by a named metadata
+ <tt>!llvm.dbg.sp</tt>.
+</p>
</div>
<!-- ======================================================================= -->
-<div class="doc_subsubsection">
+<h4>
<a name="format_blocks">Block descriptors</a>
+</h4>
+
+<div>
+
+<div class="doc_code">
+<pre>
+!3 = metadata !{
+ i32, ;; Tag = 11 + <a href="#LLVMDebugVersion">LLVMDebugVersion</a> (DW_TAG_lexical_block)
+ metadata,;; Reference to context descriptor
+ i32, ;; Line number
+ i32, ;; Column number
+ metadata,;; Reference to source file
+ i32 ;; Unique ID to identify blocks from a template function
+}
+</pre>
</div>
-<div class="doc_text">
+<p>This descriptor provides debug information about nested blocks within a
+ subprogram. The line number and column numbers are used to dinstinguish
+ two lexical blocks at same depth. </p>
<div class="doc_code">
<pre>
!3 = metadata !{
- i32, ;; Tag = 13 + <a href="#LLVMDebugVersion">LLVMDebugVersion</a> (DW_TAG_lexical_block)
- metadata ;; Reference to context descriptor
+ i32, ;; Tag = 11 + <a href="#LLVMDebugVersion">LLVMDebugVersion</a> (DW_TAG_lexical_block)
+ metadata ;; Reference to the scope we're annotating with a file change
+ metadata,;; Reference to the file the scope is enclosed in.
}
</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>
+<p>This descriptor provides a wrapper around a lexical scope to handle file
+ changes in the middle of a lexical block.</p>
</div>
<!-- ======================================================================= -->
-<div class="doc_subsubsection">
+<h4>
<a name="format_basic_type">Basic type descriptors</a>
-</div>
+</h4>
-<div class="doc_text">
+<div>
<div class="doc_code">
<pre>
!4 = metadata !{
i32, ;; Tag = 36 + <a href="#LLVMDebugVersion">LLVMDebugVersion</a>
;; (DW_TAG_base_type)
- metadata, ;; Reference to context (typically a compile unit)
+ metadata, ;; Reference to context
metadata, ;; Name (may be "" for anonymous types)
- metadata, ;; Reference to compile unit where defined (may be NULL)
+ metadata, ;; Reference to file where defined (may be NULL)
i32, ;; Line number where defined (may be 0)
i64, ;; Size in bits
i64, ;; Alignment in bits
<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
+ top level. Since basic types are not usually user defined the context
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
</div>
<!-- ======================================================================= -->
-<div class="doc_subsubsection">
+<h4>
<a name="format_derived_type">Derived type descriptors</a>
-</div>
+</h4>
-<div class="doc_text">
+<div>
<div class="doc_code">
<pre>
i32, ;; Tag (see below)
metadata, ;; Reference to context
metadata, ;; Name (may be "" for anonymous types)
- metadata, ;; Reference to compile unit where defined (may be NULL)
+ metadata, ;; Reference to file where defined (may be NULL)
i32, ;; Line number where defined (may be 0)
- i32, ;; Size in bits
- i32, ;; Alignment in bits
- i32, ;; Offset in bits
- metadata ;; Reference to type derived from
+ i64, ;; Size in bits
+ i64, ;; Alignment in bits
+ i64, ;; Offset in bits
+ metadata, ;; Reference to type derived from
+ metadata, ;; (optional) Name of the Objective C property assoicated with
+ ;; Objective-C an ivar
+ metadata, ;; (optional) Name of the Objective C property getter selector.
+ metadata, ;; (optional) Name of the Objective C property setter selector.
+ i32 ;; (optional) Objective C property attributes.
}
</pre>
</div>
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
+ from the context 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>
+<p>Note that the <tt>void *</tt> type is expressed as a type derived from NULL.
+</p>
</div>
<!-- ======================================================================= -->
-<div class="doc_subsubsection">
+<h4>
<a name="format_composite_type">Composite type descriptors</a>
-</div>
+</h4>
-<div class="doc_text">
+<div>
<div class="doc_code">
<pre>
i32, ;; Tag (see below)
metadata, ;; Reference to context
metadata, ;; Name (may be "" for anonymous types)
- metadata, ;; Reference to compile unit where defined (may be NULL)
+ metadata, ;; Reference to file where defined (may be NULL)
i32, ;; Line number where defined (may be 0)
i64, ;; Size in bits
i64, ;; Alignment in bits
<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>
+ the definition of enumeration value for the set. All enumeration type
+ descriptors are collected by named metadata <tt>!llvm.dbg.enum</tt>.</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 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
+ determined from the context 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
</div>
<!-- ======================================================================= -->
-<div class="doc_subsubsection">
+<h4>
<a name="format_subrange">Subrange descriptors</a>
-</div>
+</h4>
-<div class="doc_text">
+<div>
<div class="doc_code">
<pre>
-%<a href="#format_subrange">llvm.dbg.subrange.type</a> = type {
+!42 = metadata !{
i32, ;; Tag = 33 + <a href="#LLVMDebugVersion">LLVMDebugVersion</a> (DW_TAG_subrange_type)
i64, ;; Low value
i64 ;; High value
<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>
+ > high the array bounds are not included in generated debugging information.
+</p>
</div>
<!-- ======================================================================= -->
-<div class="doc_subsubsection">
+<h4>
<a name="format_enumeration">Enumerator descriptors</a>
-</div>
+</h4>
-<div class="doc_text">
+<div>
<div class="doc_code">
<pre>
</div>
<!-- ======================================================================= -->
-<div class="doc_subsubsection">
+<h4>
<a name="format_variables">Local variables</a>
-</div>
+</h4>
-<div class="doc_text">
+<div>
<div class="doc_code">
<pre>
i32, ;; Tag (see below)
metadata, ;; Context
metadata, ;; Name
- metadata, ;; Reference to compile unit where defined
- i32, ;; Line number where defined
- metadata ;; Type descriptor
+ metadata, ;; Reference to file where defined
+ i32, ;; 24 bit - Line number where defined
+ ;; 8 bit - Argument number. 1 indicates 1st argument.
+ metadata, ;; Type descriptor
+ i32, ;; flags
+ metadata ;; (optional) Reference to inline location
}
</pre>
</div>
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
+ Name the source variable name. Context and line indicate where the
variable was defined. Type descriptor defines the declared type of the
variable.</p>
</div>
+</div>
+
<!-- ======================================================================= -->
-<div class="doc_subsection">
+<h3>
<a name="format_common_intrinsics">Debugger intrinsic functions</a>
-</div>
+</h3>
-<div class="doc_text">
+<div>
<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">
+<h4>
<a name="format_common_declare">llvm.dbg.declare</a>
-</div>
+</h4>
-<div class="doc_text">
+<div>
<pre>
- void %<a href="#format_common_declare">llvm.dbg.declare</a>( { } *, metadata )
+ void %<a href="#format_common_declare">llvm.dbg.declare</a>(metadata, metadata)
</pre>
<p>This intrinsic provides information about a local element (ex. variable.) The
- first argument is the alloca for the variable, cast to a <tt>{ }*</tt>. The
- second argument is
- the <tt>%<a href="#format_variables">llvm.dbg.variable</a></tt> containing
- the description of the variable. </p>
+ first argument is metadata holding alloca for the variable. The
+ second argument is metadata containing description of the variable. </p>
+</div>
+
+<!-- ======================================================================= -->
+<h4>
+ <a name="format_common_value">llvm.dbg.value</a>
+</h4>
+
+<div>
+<pre>
+ void %<a href="#format_common_value">llvm.dbg.value</a>(metadata, i64, metadata)
+</pre>
+
+<p>This intrinsic provides information when a user source variable is set to a
+ new value. The first argument is the new value (wrapped as metadata). The
+ second argument is the offset in the user source variable where the new value
+ is written. The third argument is metadata containing description of the
+ user source variable. </p>
+</div>
</div>
<!-- ======================================================================= -->
-<div class="doc_subsection">
+<h3>
<a name="format_common_lifetime">Object lifetimes and scoping</a>
-</div>
+</h3>
-<div class="doc_text">
+<div>
<p>In many languages, the local variables in functions can have their lifetimes
or scopes limited to a subset of a function. In the C family of languages,
for example, variables are only live (readable and writable) within the
rules.</p>
<p>In order to handle this, the LLVM debug format uses the metadata attached to
- llvm instructions to encode line nuber and scoping information. Consider the
- following C fragment, for example:</p>
+ llvm instructions to encode line number and scoping information. Consider
+ the following C fragment, for example:</p>
<div class="doc_code">
<pre>
%X = alloca i32, align 4 ; <i32*> [#uses=4]
%Y = alloca i32, align 4 ; <i32*> [#uses=4]
%Z = alloca i32, align 4 ; <i32*> [#uses=3]
- %0 = bitcast i32* %X to { }* ; <{ }*> [#uses=1]
- call void @llvm.dbg.declare({ }* %0, metadata !0), !dbg !7
+ %0 = bitcast i32* %X to {}* ; <{}*> [#uses=1]
+ call void @llvm.dbg.declare(metadata !{i32 * %X}, metadata !0), !dbg !7
store i32 21, i32* %X, !dbg !8
- %1 = bitcast i32* %Y to { }* ; <{ }*> [#uses=1]
- call void @llvm.dbg.declare({ }* %1, metadata !9), !dbg !10
+ %1 = bitcast i32* %Y to {}* ; <{}*> [#uses=1]
+ call void @llvm.dbg.declare(metadata !{i32 * %Y}, metadata !9), !dbg !10
store i32 22, i32* %Y, !dbg !11
- %2 = bitcast i32* %Z to { }* ; <{ }*> [#uses=1]
- call void @llvm.dbg.declare({ }* %2, metadata !12), !dbg !14
+ %2 = bitcast i32* %Z to {}* ; <{}*> [#uses=1]
+ call void @llvm.dbg.declare(metadata !{i32 * %Z}, metadata !12), !dbg !14
store i32 23, i32* %Z, !dbg !15
%tmp = load i32* %X, !dbg !16 ; <i32> [#uses=1]
%tmp1 = load i32* %Y, !dbg !16 ; <i32> [#uses=1]
ret void, !dbg !18
}
-declare void @llvm.dbg.declare({ }*, metadata) nounwind readnone
+declare void @llvm.dbg.declare(metadata, metadata) nounwind readnone
!0 = metadata !{i32 459008, metadata !1, metadata !"X",
metadata !3, i32 2, metadata !6}; [ DW_TAG_auto_variable ]
<div class="doc_code">
<pre>
-call void @llvm.dbg.declare({ }* %0, metadata !0), !dbg !7
+call void @llvm.dbg.declare(metadata, metadata !0), !dbg !7
</pre>
</div>
<div class="doc_code">
<pre>
-call void @llvm.dbg.declare({ }* %2, metadata !12), !dbg !14
+call void @llvm.dbg.declare(metadata, metadata !12), !dbg !14
</pre>
</div>
</pre>
</div>
-<p>Here <tt>!14</tt> indicates that <tt>Z</tt> is declaread at line number 5 and
+<p>Here <tt>!14</tt> indicates that <tt>Z</tt> is declared at line number 5 and
column number 9 inside of lexical scope <tt>!13</tt>. The lexical scope
itself resides inside of lexical scope <tt>!1</tt> described above.</p>
</div>
+</div>
+
<!-- *********************************************************************** -->
-<div class="doc_section">
+<h2>
<a name="ccxx_frontend">C/C++ front-end specific debug information</a>
-</div>
+</h2>
<!-- *********************************************************************** -->
-<div class="doc_text">
+<div>
<p>The C and C++ front-ends represent information about the program in a format
that is effectively identical
<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">
+<h3>
<a name="ccxx_compile_units">C/C++ source file information</a>
-</div>
+</h3>
-<div class="doc_text">
+<div>
<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>
<pre>
...
;;
-;; Define the compile unit for the source file "/Users/mine/sources/MySource.cpp".
+;; Define the compile unit for the main source file "/Users/mine/sources/MySource.cpp".
;;
-!3 = metadata !{
- i32 458769, ;; Tag
+!2 = metadata !{
+ i32 524305, ;; Tag
i32 0, ;; Unused
i32 4, ;; Language Id
metadata !"MySource.cpp",
i32 0} ;; Runtime version
;;
-;; Define the compile unit for the header file "/Users/mine/sources/MyHeader.h".
+;; Define the file for the file "/Users/mine/sources/MySource.cpp".
;;
!1 = metadata !{
- i32 458769, ;; Tag
- i32 0, ;; Unused
- i32 4, ;; Language Id
- metadata !"MyHeader.h",
+ i32 524329, ;; Tag
+ metadata !"MySource.cpp",
metadata !"/Users/mine/sources",
- metadata !"4.2.1 (Based on Apple Inc. build 5649) (LLVM build 00)",
- i1 false, ;; Main Compile Unit
- i1 false, ;; Optimized compile unit
- metadata !"", ;; Compiler flags
- i32 0} ;; Runtime version
+ metadata !2 ;; Compile unit
+}
+
+;;
+;; Define the file for the file "/Users/mine/sources/Myheader.h"
+;;
+!3 = metadata !{
+ i32 524329, ;; Tag
+ metadata !"Myheader.h"
+ metadata !"/Users/mine/sources",
+ metadata !2 ;; Compile unit
+}
...
</pre>
</div>
+<p>llvm::Instruction provides easy access to metadata attached with an
+instruction. One can extract line number information encoded in LLVM IR
+using <tt>Instruction::getMetadata()</tt> and
+<tt>DILocation::getLineNumber()</tt>.
+<pre>
+ if (MDNode *N = I->getMetadata("dbg")) { // Here I is an LLVM instruction
+ DILocation Loc(N); // DILocation is in DebugInfo.h
+ unsigned Line = Loc.getLineNumber();
+ StringRef File = Loc.getFilename();
+ StringRef Dir = Loc.getDirectory();
+ }
+</pre>
</div>
<!-- ======================================================================= -->
-<div class="doc_subsection">
+<h3>
<a name="ccxx_global_variable">C/C++ global variable information</a>
-</div>
+</h3>
-<div class="doc_text">
+<div>
<p>Given an integer global variable declared as follows:</p>
;; variable anchor and the global variable itself.
;;
!0 = metadata !{
- i32 458804, ;; Tag
+ i32 524340, ;; Tag
i32 0, ;; Unused
metadata !1, ;; Context
metadata !"MyGlobal", ;; Name
metadata !"MyGlobal", ;; Display Name
metadata !"MyGlobal", ;; Linkage Name
- metadata !1, ;; Compile Unit
+ metadata !3, ;; Compile Unit
i32 1, ;; Line Number
- metadata !2, ;; Type
+ metadata !4, ;; Type
i1 false, ;; Is a local variable
i1 true, ;; Is this a definition
i32* @MyGlobal ;; The global variable
;; Define the basic type of 32 bit signed integer. Note that since int is an
;; intrinsic type the source file is NULL and line 0.
;;
-!2 = metadata !{
- i32 458788, ;; Tag
+!4 = metadata !{
+ i32 524324, ;; Tag
metadata !1, ;; Context
metadata !"int", ;; Name
- metadata !1, ;; Compile Unit
+ metadata !1, ;; File
i32 0, ;; Line number
i64 32, ;; Size in Bits
i64 32, ;; Align in Bits
</div>
<!-- ======================================================================= -->
-<div class="doc_subsection">
+<h3>
<a name="ccxx_subprogram">C/C++ function information</a>
-</div>
+</h3>
-<div class="doc_text">
+<div>
<p>Given a function declared as follows:</p>
;; anchor is 46, which is the same as the tag for subprograms
;; (46 = DW_TAG_subprogram.)
;;
-!0 = metadata !{
- i32 458798, ;; Tag
+!6 = metadata !{
+ i32 524334, ;; Tag
i32 0, ;; Unused
metadata !1, ;; Context
metadata !"main", ;; Name
metadata !"main", ;; Display name
metadata !"main", ;; Linkage name
- metadata !1, ;; Compile unit
+ metadata !1, ;; File
i32 1, ;; Line number
- metadata !2, ;; Type
+ metadata !4, ;; Type
i1 false, ;; Is local
- i1 true ;; Is definition
+ i1 true, ;; Is definition
+ i32 0, ;; Virtuality attribute, e.g. pure virtual function
+ i32 0, ;; Index into virtual table for C++ methods
+ i32 0, ;; Type that holds virtual table.
+ i32 0, ;; Flags
+ i1 false, ;; True if this function is optimized
+ Function *, ;; Pointer to llvm::Function
+ null ;; Function template parameters
}
;;
;; Define the subprogram itself.
</div>
<!-- ======================================================================= -->
-<div class="doc_subsection">
+<h3>
<a name="ccxx_basic_types">C/C++ basic types</a>
-</div>
+</h3>
-<div class="doc_text">
+<div>
<p>The following are the basic type descriptors for C/C++ core types:</p>
-</div>
-
<!-- ======================================================================= -->
-<div class="doc_subsubsection">
+<h4>
<a name="ccxx_basic_type_bool">bool</a>
-</div>
+</h4>
-<div class="doc_text">
+<div>
<div class="doc_code">
<pre>
!2 = metadata !{
- i32 458788, ;; Tag
+ i32 524324, ;; Tag
metadata !1, ;; Context
metadata !"bool", ;; Name
- metadata !1, ;; Compile Unit
+ metadata !1, ;; File
i32 0, ;; Line number
i64 8, ;; Size in Bits
i64 8, ;; Align in Bits
</div>
<!-- ======================================================================= -->
-<div class="doc_subsubsection">
+<h4>
<a name="ccxx_basic_char">char</a>
-</div>
+</h4>
-<div class="doc_text">
+<div>
<div class="doc_code">
<pre>
!2 = metadata !{
- i32 458788, ;; Tag
+ i32 524324, ;; Tag
metadata !1, ;; Context
metadata !"char", ;; Name
- metadata !1, ;; Compile Unit
+ metadata !1, ;; File
i32 0, ;; Line number
i64 8, ;; Size in Bits
i64 8, ;; Align in Bits
</div>
<!-- ======================================================================= -->
-<div class="doc_subsubsection">
+<h4>
<a name="ccxx_basic_unsigned_char">unsigned char</a>
-</div>
+</h4>
-<div class="doc_text">
+<div>
<div class="doc_code">
<pre>
!2 = metadata !{
- i32 458788, ;; Tag
+ i32 524324, ;; Tag
metadata !1, ;; Context
metadata !"unsigned char",
- metadata !1, ;; Compile Unit
+ metadata !1, ;; File
i32 0, ;; Line number
i64 8, ;; Size in Bits
i64 8, ;; Align in Bits
</div>
<!-- ======================================================================= -->
-<div class="doc_subsubsection">
+<h4>
<a name="ccxx_basic_short">short</a>
-</div>
+</h4>
-<div class="doc_text">
+<div>
<div class="doc_code">
<pre>
!2 = metadata !{
- i32 458788, ;; Tag
+ i32 524324, ;; Tag
metadata !1, ;; Context
metadata !"short int",
- metadata !1, ;; Compile Unit
+ metadata !1, ;; File
i32 0, ;; Line number
i64 16, ;; Size in Bits
i64 16, ;; Align in Bits
</div>
<!-- ======================================================================= -->
-<div class="doc_subsubsection">
+<h4>
<a name="ccxx_basic_unsigned_short">unsigned short</a>
-</div>
+</h4>
-<div class="doc_text">
+<div>
<div class="doc_code">
<pre>
!2 = metadata !{
- i32 458788, ;; Tag
+ i32 524324, ;; Tag
metadata !1, ;; Context
metadata !"short unsigned int",
- metadata !1, ;; Compile Unit
+ metadata !1, ;; File
i32 0, ;; Line number
i64 16, ;; Size in Bits
i64 16, ;; Align in Bits
</div>
<!-- ======================================================================= -->
-<div class="doc_subsubsection">
+<h4>
<a name="ccxx_basic_int">int</a>
-</div>
+</h4>
-<div class="doc_text">
+<div>
<div class="doc_code">
<pre>
!2 = metadata !{
- i32 458788, ;; Tag
+ i32 524324, ;; Tag
metadata !1, ;; Context
metadata !"int", ;; Name
- metadata !1, ;; Compile Unit
+ metadata !1, ;; File
i32 0, ;; Line number
i64 32, ;; Size in Bits
i64 32, ;; Align in Bits
</div>
<!-- ======================================================================= -->
-<div class="doc_subsubsection">
+<h4>
<a name="ccxx_basic_unsigned_int">unsigned int</a>
-</div>
+</h4>
-<div class="doc_text">
+<div>
<div class="doc_code">
<pre>
!2 = metadata !{
- i32 458788, ;; Tag
+ i32 524324, ;; Tag
metadata !1, ;; Context
metadata !"unsigned int",
- metadata !1, ;; Compile Unit
+ metadata !1, ;; File
i32 0, ;; Line number
i64 32, ;; Size in Bits
i64 32, ;; Align in Bits
</div>
<!-- ======================================================================= -->
-<div class="doc_subsubsection">
+<h4>
<a name="ccxx_basic_long_long">long long</a>
-</div>
+</h4>
-<div class="doc_text">
+<div>
<div class="doc_code">
<pre>
!2 = metadata !{
- i32 458788, ;; Tag
+ i32 524324, ;; Tag
metadata !1, ;; Context
metadata !"long long int",
- metadata !1, ;; Compile Unit
+ metadata !1, ;; File
i32 0, ;; Line number
i64 64, ;; Size in Bits
i64 64, ;; Align in Bits
</div>
<!-- ======================================================================= -->
-<div class="doc_subsubsection">
+<h4>
<a name="ccxx_basic_unsigned_long_long">unsigned long long</a>
-</div>
+</h4>
-<div class="doc_text">
+<div>
<div class="doc_code">
<pre>
!2 = metadata !{
- i32 458788, ;; Tag
+ i32 524324, ;; Tag
metadata !1, ;; Context
metadata !"long long unsigned int",
- metadata !1, ;; Compile Unit
+ metadata !1, ;; File
i32 0, ;; Line number
i64 64, ;; Size in Bits
i64 64, ;; Align in Bits
</div>
<!-- ======================================================================= -->
-<div class="doc_subsubsection">
+<h4>
<a name="ccxx_basic_float">float</a>
-</div>
+</h4>
-<div class="doc_text">
+<div>
<div class="doc_code">
<pre>
!2 = metadata !{
- i32 458788, ;; Tag
+ i32 524324, ;; Tag
metadata !1, ;; Context
metadata !"float",
- metadata !1, ;; Compile Unit
+ metadata !1, ;; File
i32 0, ;; Line number
i64 32, ;; Size in Bits
i64 32, ;; Align in Bits
</div>
<!-- ======================================================================= -->
-<div class="doc_subsubsection">
+<h4>
<a name="ccxx_basic_double">double</a>
-</div>
+</h4>
-<div class="doc_text">
+<div>
<div class="doc_code">
<pre>
!2 = metadata !{
- i32 458788, ;; Tag
+ i32 524324, ;; Tag
metadata !1, ;; Context
metadata !"double",;; Name
- metadata !1, ;; Compile Unit
+ metadata !1, ;; File
i32 0, ;; Line number
i64 64, ;; Size in Bits
i64 64, ;; Align in Bits
</div>
+</div>
+
<!-- ======================================================================= -->
-<div class="doc_subsection">
+<h3>
<a name="ccxx_derived_types">C/C++ derived types</a>
-</div>
+</h3>
-<div class="doc_text">
+<div>
<p>Given the following as an example of C/C++ derived type:</p>
;; Define the typedef "IntPtr".
;;
!2 = metadata !{
- i32 458774, ;; Tag
+ i32 524310, ;; Tag
metadata !1, ;; Context
metadata !"IntPtr", ;; Name
- metadata !3, ;; Compile unit
+ metadata !3, ;; File
i32 0, ;; Line number
i64 0, ;; Size in bits
i64 0, ;; Align in bits
;; Define the pointer type.
;;
!4 = metadata !{
- i32 458767, ;; Tag
+ i32 524303, ;; Tag
metadata !1, ;; Context
metadata !"", ;; Name
- metadata !1, ;; Compile unit
+ metadata !1, ;; File
i32 0, ;; Line number
i64 64, ;; Size in bits
i64 64, ;; Align in bits
;; Define the const type.
;;
!5 = metadata !{
- i32 458790, ;; Tag
+ i32 524326, ;; Tag
metadata !1, ;; Context
metadata !"", ;; Name
- metadata !1, ;; Compile unit
+ metadata !1, ;; File
i32 0, ;; Line number
i64 32, ;; Size in bits
i64 32, ;; Align in bits
;; Define the int type.
;;
!6 = metadata !{
- i32 458788, ;; Tag
+ i32 524324, ;; Tag
metadata !1, ;; Context
metadata !"int", ;; Name
- metadata !1, ;; Compile unit
+ metadata !1, ;; File
i32 0, ;; Line number
i64 32, ;; Size in bits
i64 32, ;; Align in bits
</div>
<!-- ======================================================================= -->
-<div class="doc_subsection">
+<h3>
<a name="ccxx_composite_types">C/C++ struct/union types</a>
-</div>
+</h3>
-<div class="doc_text">
+<div>
<p>Given the following as an example of C/C++ struct type:</p>
;; Define basic type for unsigned int.
;;
!5 = metadata !{
- i32 458788, ;; Tag
+ i32 524324, ;; Tag
metadata !1, ;; Context
metadata !"unsigned int",
- metadata !1, ;; Compile Unit
+ metadata !1, ;; File
i32 0, ;; Line number
i64 32, ;; Size in Bits
i64 32, ;; Align in Bits
;; Define composite type for struct Color.
;;
!2 = metadata !{
- i32 458771, ;; Tag
+ i32 524307, ;; Tag
metadata !1, ;; Context
metadata !"Color", ;; Name
metadata !1, ;; Compile unit
;; Define the Red field.
;;
!4 = metadata !{
- i32 458765, ;; Tag
+ i32 524301, ;; Tag
metadata !1, ;; Context
metadata !"Red", ;; Name
- metadata !1, ;; Compile Unit
+ metadata !1, ;; File
i32 2, ;; Line number
i64 32, ;; Size in bits
i64 32, ;; Align in bits
;; Define the Green field.
;;
!6 = metadata !{
- i32 458765, ;; Tag
+ i32 524301, ;; Tag
metadata !1, ;; Context
metadata !"Green", ;; Name
- metadata !1, ;; Compile Unit
+ metadata !1, ;; File
i32 3, ;; Line number
i64 32, ;; Size in bits
i64 32, ;; Align in bits
;; Define the Blue field.
;;
!7 = metadata !{
- i32 458765, ;; Tag
+ i32 524301, ;; Tag
metadata !1, ;; Context
metadata !"Blue", ;; Name
- metadata !1, ;; Compile Unit
+ metadata !1, ;; File
i32 4, ;; Line number
i64 32, ;; Size in bits
i64 32, ;; Align in bits
</div>
<!-- ======================================================================= -->
-<div class="doc_subsection">
+<h3>
<a name="ccxx_enumeration_types">C/C++ enumeration types</a>
-</div>
+</h3>
-<div class="doc_text">
+<div>
<p>Given the following as an example of C/C++ enumeration type:</p>
;; Define composite type for enum Trees
;;
!2 = metadata !{
- i32 458756, ;; Tag
+ i32 524292, ;; Tag
metadata !1, ;; Context
metadata !"Trees", ;; Name
- metadata !1, ;; Compile unit
+ metadata !1, ;; File
i32 1, ;; Line number
i64 32, ;; Size in bits
i64 32, ;; Align in bits
;;
;; Define Spruce enumerator.
;;
-!4 = metadata !{i32 458792, metadata !"Spruce", i64 100}
+!4 = metadata !{i32 524328, metadata !"Spruce", i64 100}
;;
;; Define Oak enumerator.
;;
-!5 = metadata !{i32 458792, metadata !"Oak", i64 200}
+!5 = metadata !{i32 524328, metadata !"Oak", i64 200}
;;
;; Define Maple enumerator.
;;
-!6 = metadata !{i32 458792, metadata !"Maple", i64 300}
+!6 = metadata !{i32 524328, metadata !"Maple", i64 300}
</pre>
</div>
</div>
+</div>
+
<!-- *********************************************************************** -->
<hr>
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>
+ <a href="http://llvm.org/">LLVM Compiler Infrastructure</a><br>
Last modified: $Date$
</address>
projects / oota-llvm.git / blobdiff