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5 <title>Source Level Debugging with LLVM</title>
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10 <div class="doc_title">Source Level Debugging with LLVM</div>
12 <table class="layout" style="width:100%">
16 <li><a href="#introduction">Introduction</a>
18 <li><a href="#phil">Philosophy behind LLVM debugging information</a></li>
19 <li><a href="#consumers">Debug information consumers</a></li>
20 <li><a href="#debugopt">Debugging optimized code</a></li>
22 <li><a href="#format">Debugging information format</a>
24 <li><a href="#debug_info_descriptors">Debug information descriptors</a>
26 <li><a href="#format_anchors">Anchor descriptors</a></li>
27 <li><a href="#format_compile_units">Compile unit descriptors</a></li>
28 <li><a href="#format_global_variables">Global variable descriptors</a></li>
29 <li><a href="#format_subprograms">Subprogram descriptors</a></li>
30 <li><a href="#format_blocks">Block descriptors</a></li>
31 <li><a href="#format_basic_type">Basic type descriptors</a></li>
32 <li><a href="#format_derived_type">Derived type descriptors</a></li>
33 <li><a href="#format_composite_type">Composite type descriptors</a></li>
34 <li><a href="#format_subrange">Subrange descriptors</a></li>
35 <li><a href="#format_enumeration">Enumerator descriptors</a></li>
36 <li><a href="#format_variables">Local variables</a></li>
38 <li><a href="#format_common_intrinsics">Debugger intrinsic functions</a>
40 <li><a href="#format_common_stoppoint">llvm.dbg.stoppoint</a></li>
41 <li><a href="#format_common_func_start">llvm.dbg.func.start</a></li>
42 <li><a href="#format_common_region_start">llvm.dbg.region.start</a></li>
43 <li><a href="#format_common_region_end">llvm.dbg.region.end</a></li>
44 <li><a href="#format_common_declare">llvm.dbg.declare</a></li>
46 <li><a href="#format_common_stoppoints">Representing stopping points in the
47 source program</a></li>
49 <li><a href="#ccxx_frontend">C/C++ front-end specific debug information</a>
51 <li><a href="#ccxx_compile_units">C/C++ source file information</a></li>
52 <li><a href="#ccxx_global_variable">C/C++ global variable information</a></li>
53 <li><a href="#ccxx_subprogram">C/C++ function information</a></li>
54 <li><a href="#ccxx_basic_types">C/C++ basic types</a></li>
55 <li><a href="#ccxx_derived_types">C/C++ derived types</a></li>
56 <li><a href="#ccxx_composite_types">C/C++ struct/union types</a></li>
57 <li><a href="#ccxx_enumeration_types">C/C++ enumeration types</a></li>
62 <img src="img/venusflytrap.jpg" alt="A leafy and green bug eater" width="247"
67 <div class="doc_author">
68 <p>Written by <a href="mailto:sabre@nondot.org">Chris Lattner</a>
69 and <a href="mailto:jlaskey@apple.com">Jim Laskey</a></p>
73 <!-- *********************************************************************** -->
74 <div class="doc_section"><a name="introduction">Introduction</a></div>
75 <!-- *********************************************************************** -->
77 <div class="doc_text">
79 <p>This document is the central repository for all information pertaining to
80 debug information in LLVM. It describes the <a href="#format">actual format
81 that the LLVM debug information</a> takes, which is useful for those interested
82 in creating front-ends or dealing directly with the information. Further, this
83 document provides specifc examples of what debug information for C/C++.</p>
87 <!-- ======================================================================= -->
88 <div class="doc_subsection">
89 <a name="phil">Philosophy behind LLVM debugging information</a>
92 <div class="doc_text">
94 <p>The idea of the LLVM debugging information is to capture how the important
95 pieces of the source-language's Abstract Syntax Tree map onto LLVM code.
96 Several design aspects have shaped the solution that appears here. The
97 important ones are:</p>
100 <li>Debugging information should have very little impact on the rest of the
101 compiler. No transformations, analyses, or code generators should need to be
102 modified because of debugging information.</li>
104 <li>LLVM optimizations should interact in <a href="#debugopt">well-defined and
105 easily described ways</a> with the debugging information.</li>
107 <li>Because LLVM is designed to support arbitrary programming languages,
108 LLVM-to-LLVM tools should not need to know anything about the semantics of the
109 source-level-language.</li>
111 <li>Source-level languages are often <b>widely</b> different from one another.
112 LLVM should not put any restrictions of the flavor of the source-language, and
113 the debugging information should work with any language.</li>
115 <li>With code generator support, it should be possible to use an LLVM compiler
116 to compile a program to native machine code and standard debugging formats.
117 This allows compatibility with traditional machine-code level debuggers, like
122 <p>The approach used by the LLVM implementation is to use a small set of <a
123 href="#format_common_intrinsics">intrinsic functions</a> to define a mapping
124 between LLVM program objects and the source-level objects. The description of
125 the source-level program is maintained in LLVM global variables in an <a
126 href="#ccxx_frontend">implementation-defined format</a> (the C/C++ front-end
127 currently uses working draft 7 of the <a
128 href="http://www.eagercon.com/dwarf/dwarf3std.htm">Dwarf 3 standard</a>).</p>
130 <p>When a program is being debugged, a debugger interacts with the user and
131 turns the stored debug information into source-language specific information.
132 As such, a debugger must be aware of the source-language, and is thus tied to
133 a specific language of family of languages.</p>
137 <!-- ======================================================================= -->
138 <div class="doc_subsection">
139 <a name="consumers">Debug information consumers</a>
142 <div class="doc_text">
143 <p>The role of debug information is to provide meta information normally
144 stripped away during the compilation process. This meta information provides an
145 llvm user a relationship between generated code and the original program source
148 <p>Currently, debug information is consumed by the DwarfWriter to produce dwarf
149 information used by the gdb debugger. Other targets could use the same
150 information to produce stabs or other debug forms.</p>
152 <p>It would also be reasonable to use debug information to feed profiling tools
153 for analysis of generated code, or, tools for reconstructing the original source
154 from generated code.</p>
156 <p>TODO - expound a bit more.</p>
160 <!-- ======================================================================= -->
161 <div class="doc_subsection">
162 <a name="debugopt">Debugging optimized code</a>
165 <div class="doc_text">
167 <p>An extremely high priority of LLVM debugging information is to make it
168 interact well with optimizations and analysis. In particular, the LLVM debug
169 information provides the following guarantees:</p>
173 <li>LLVM debug information <b>always provides information to accurately read the
174 source-level state of the program</b>, regardless of which LLVM optimizations
175 have been run, and without any modification to the optimizations themselves.
176 However, some optimizations may impact the ability to modify the current state
177 of the program with a debugger, such as setting program variables, or calling
178 function that have been deleted.</li>
180 <li>LLVM optimizations gracefully interact with debugging information. If they
181 are not aware of debug information, they are automatically disabled as necessary
182 in the cases that would invalidate the debug info. This retains the LLVM
183 features making it easy to write new transformations.</li>
185 <li>As desired, LLVM optimizations can be upgraded to be aware of the LLVM
186 debugging information, allowing them to update the debugging information as they
187 perform aggressive optimizations. This means that, with effort, the LLVM
188 optimizers could optimize debug code just as well as non-debug code.</li>
190 <li>LLVM debug information does not prevent many important optimizations from
191 happening (for example inlining, basic block reordering/merging/cleanup, tail
192 duplication, etc), further reducing the amount of the compiler that eventually
193 is "aware" of debugging information.</li>
195 <li>LLVM debug information is automatically optimized along with the rest of the
196 program, using existing facilities. For example, duplicate information is
197 automatically merged by the linker, and unused information is automatically
202 <p>Basically, the debug information allows you to compile a program with
203 "<tt>-O0 -g</tt>" and get full debug information, allowing you to arbitrarily
204 modify the program as it executes from a debugger. Compiling a program with
205 "<tt>-O3 -g</tt>" gives you full debug information that is always available and
206 accurate for reading (e.g., you get accurate stack traces despite tail call
207 elimination and inlining), but you might lose the ability to modify the program
208 and call functions where were optimized out of the program, or inlined away
213 <!-- *********************************************************************** -->
214 <div class="doc_section">
215 <a name="format">Debugging information format</a>
217 <!-- *********************************************************************** -->
219 <div class="doc_text">
221 <p>LLVM debugging information has been carefully designed to make it possible
222 for the optimizer to optimize the program and debugging information without
223 necessarily having to know anything about debugging information. In particular,
224 the global constant merging pass automatically eliminates duplicated debugging
225 information (often caused by header files), the global dead code elimination
226 pass automatically deletes debugging information for a function if it decides to
227 delete the function, and the linker eliminates debug information when it merges
228 <tt>linkonce</tt> functions.</p>
230 <p>To do this, most of the debugging information (descriptors for types,
231 variables, functions, source files, etc) is inserted by the language front-end
232 in the form of LLVM global variables. These LLVM global variables are no
233 different from any other global variables, except that they have a web of LLVM
234 intrinsic functions that point to them. If the last references to a particular
235 piece of debugging information are deleted (for example, by the
236 <tt>-globaldce</tt> pass), the extraneous debug information will automatically
237 become dead and be removed by the optimizer.</p>
239 <p>Debug information is designed to be agnostic about the target debugger and
240 debugging information representation (e.g. DWARF/Stabs/etc). It uses a generic
241 machine debug information pass to decode the information that represents
242 variables, types, functions, namespaces, etc: this allows for arbitrary
243 source-language semantics and type-systems to be used, as long as there is a
244 module written for the target debugger to interpret the information. In
245 addition, debug global variables are declared in the <tt>"llvm.metadata"</tt>
246 section. All values declared in this section are stripped away after target
247 debug information is constructed and before the program object is emitted.</p>
249 <p>To provide basic functionality, the LLVM debugger does have to make some
250 assumptions about the source-level language being debugged, though it keeps
251 these to a minimum. The only common features that the LLVM debugger assumes
252 exist are <a href="#format_compile_units">source files</a>, and <a
253 href="#format_global_variables">program objects</a>. These abstract objects are
254 used by a debugger to form stack traces, show information about local
257 <p>This section of the documentation first describes the representation aspects
258 common to any source-language. The <a href="#ccxx_frontend">next section</a>
259 describes the data layout conventions used by the C and C++ front-ends.</p>
263 <!-- ======================================================================= -->
264 <div class="doc_subsection">
265 <a name="debug_info_descriptors">Debug information descriptors</a>
268 <div class="doc_text">
269 <p>In consideration of the complexity and volume of debug information, LLVM
270 provides a specification for well formed debug global variables. The constant
271 value of each of these globals is one of a limited set of structures, known as
272 debug descriptors.</p>
274 <p>Consumers of LLVM debug information expect the descriptors for program
275 objects to start in a canonical format, but the descriptors can include
276 additional information appended at the end that is source-language specific. All
277 LLVM debugging information is versioned, allowing backwards compatibility in the
278 case that the core structures need to change in some way. Also, all debugging
279 information objects start with a tag to indicate what type of object it is. The
280 source-language is allowed to define its own objects, by using unreserved tag
281 numbers. We recommend using with tags in the range 0x1000 thru 0x2000 (there is
282 a defined enum DW_TAG_user_base = 0x1000.)</p>
284 <p>The fields of debug descriptors used internally by LLVM (MachineDebugInfo)
285 are restricted to only the simple data types <tt>int</tt>, <tt>uint</tt>,
286 <tt>bool</tt>, <tt>float</tt>, <tt>double</tt>, <tt>sbyte*</tt> and <tt> { }*
287 </tt>. References to arbitrary values are handled using a <tt> { }* </tt> and a
288 cast to <tt> { }* </tt> expression; typically references to other field
289 descriptors, arrays of descriptors or global variables.</p>
292 %llvm.dbg.object.type = type {
298 <p><a name="LLVMDebugVersion">The first field of a descriptor is always an
299 <tt>uint</tt> containing a tag value identifying the content of the descriptor.
300 The remaining fields are specific to the descriptor. The values of tags are
301 loosely bound to the tag values of Dwarf information entries. However, that
302 does not restrict the use of the information supplied to Dwarf targets. To
303 facilitate versioning of debug information, the tag is augmented with the
304 current debug version (LLVMDebugVersion = 4 << 16 or 0x40000 or 262144.)</a></p>
306 <p>The details of the various descriptors follow.</p>
310 <!-- ======================================================================= -->
311 <div class="doc_subsubsection">
312 <a name="format_anchors">Anchor descriptors</a>
315 <div class="doc_text">
318 %<a href="#format_anchors">llvm.dbg.anchor.type</a> = type {
319 uint, ;; Tag = 0 + <a href="#LLVMDebugVersion">LLVMDebugVersion</a>
320 uint ;; Tag of descriptors grouped by the anchor
324 <p>One important aspect of the LLVM debug representation is that it allows the
325 LLVM debugger to efficiently index all of the global objects without having the
326 scan the program. To do this, all of the global objects use "anchor"
327 descriptors with designated names. All of the global objects of a particular
328 type (e.g., compile units) contain a pointer to the anchor. This pointer allows
329 a debugger to use def-use chains to find all global objects of that type.</p>
331 <p>The following names are recognized as anchors by LLVM:</p>
334 %<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
335 %<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
336 %<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
339 <p>Using anchors in this way (where the compile unit descriptor points to the
340 anchors, as opposed to having a list of compile unit descriptors) allows for the
341 standard dead global elimination and merging passes to automatically remove
342 unused debugging information. If the globals were kept track of through lists,
343 there would always be an object pointing to the descriptors, thus would never be
348 <!-- ======================================================================= -->
349 <div class="doc_subsubsection">
350 <a name="format_compile_units">Compile unit descriptors</a>
353 <div class="doc_text">
356 %<a href="#format_compile_units">llvm.dbg.compile_unit.type</a> = type {
357 uint, ;; Tag = 17 + <a href="#LLVMDebugVersion">LLVMDebugVersion</a> (DW_TAG_compile_unit)
358 { }*, ;; Compile unit anchor = cast = (%<a href="#format_anchors">llvm.dbg.anchor.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_units</a> to { }*)
359 uint, ;; Dwarf language identifier (ex. DW_LANG_C89)
360 sbyte*, ;; Source file name
361 sbyte*, ;; Source file directory (includes trailing slash)
362 sbyte* ;; Producer (ex. "4.0.1 LLVM (LLVM research group)")
366 <p>These descriptors contain a source language ID for the file (we use the Dwarf
367 3.0 ID numbers, such as <tt>DW_LANG_C89</tt>, <tt>DW_LANG_C_plus_plus</tt>,
368 <tt>DW_LANG_Cobol74</tt>, etc), three strings describing the filename, working
369 directory of the compiler, and an identifier string for the compiler that
372 <p> Compile unit descriptors provide the root context for objects declared in a
373 specific source file. Global variables and top level functions would be defined
374 using this context. Compile unit descriptors also provide context for source
375 line correspondence.</p>
379 <!-- ======================================================================= -->
380 <div class="doc_subsubsection">
381 <a name="format_global_variables">Global variable descriptors</a>
384 <div class="doc_text">
387 %<a href="#format_global_variables">llvm.dbg.global_variable.type</a> = type {
388 uint, ;; Tag = 52 + <a href="#LLVMDebugVersion">LLVMDebugVersion</a> (DW_TAG_variable)
389 { }*, ;; Global variable anchor = cast (%<a href="#format_anchors">llvm.dbg.anchor.type</a>* %<a href="#format_global_variables">llvm.dbg.global_variables</a> to { }*),
390 { }*, ;; Reference to context descriptor
392 sbyte*, ;; Display name (unmangled name if Name is the C++ mangled name)
393 { }*, ;; Reference to compile unit where defined
394 uint, ;; Line number where defined
395 { }*, ;; Reference to type descriptor
396 bool, ;; True if the global is local to compile unit (static)
397 bool, ;; True if the global is defined in the compile unit (not extern)
398 { }* ;; Reference to the global variable
402 <p>These descriptors provide debug information about globals variables. The
403 provide details such as name, type and where the variable is defined.</p>
407 <!-- ======================================================================= -->
408 <div class="doc_subsubsection">
409 <a name="format_subprograms">Subprogram descriptors</a>
412 <div class="doc_text">
415 %<a href="#format_subprograms">llvm.dbg.subprogram.type</a> = type {
416 uint, ;; Tag = 46 + <a href="#LLVMDebugVersion">LLVMDebugVersion</a> (DW_TAG_subprogram)
417 { }*, ;; Subprogram anchor = cast (%<a href="#format_anchors">llvm.dbg.anchor.type</a>* %<a href="#format_subprograms">llvm.dbg.subprograms</a> to { }*),
418 { }*, ;; Reference to context descriptor
420 sbyte*, ;; Display name (unmangled name if Name is the C++ mangled name)
421 { }*, ;; Reference to compile unit where defined
422 uint, ;; Line number where defined
423 { }*, ;; Reference to type descriptor
424 bool, ;; True if the global is local to compile unit (static)
425 bool ;; True if the global is defined in the compile unit (not extern)
429 <p>These descriptors provide debug information about functions, methods and
430 subprograms. They provide details such as name, return types and the source
431 location where the subprogram is defined.</p>
434 <!-- ======================================================================= -->
435 <div class="doc_subsubsection">
436 <a name="format_blocks">Block descriptors</a>
439 <div class="doc_text">
442 %<a href="#format_blocks">llvm.dbg.block</a> = type {
443 uint, ;; Tag = 13 + <a href="#LLVMDebugVersion">LLVMDebugVersion</a> (DW_TAG_lexical_block)
444 { }* ;; Reference to context descriptor
448 <p>These descriptors provide debug information about nested blocks within a
449 subprogram. The array of member descriptors is used to define local variables
450 and deeper nested blocks.</p>
454 <!-- ======================================================================= -->
455 <div class="doc_subsubsection">
456 <a name="format_basic_type">Basic type descriptors</a>
459 <div class="doc_text">
462 %<a href="#format_basic_type">llvm.dbg.basictype.type</a> = type {
463 uint, ;; Tag = 36 + <a href="#LLVMDebugVersion">LLVMDebugVersion</a> (DW_TAG_base_type)
464 { }*, ;; Reference to context (typically a compile unit)
465 sbyte*, ;; Name (may be "" for anonymous types)
466 { }*, ;; Reference to compile unit where defined (may be NULL)
467 uint, ;; Line number where defined (may be 0)
468 uint, ;; Size in bits
469 uint, ;; Alignment in bits
470 uint, ;; Offset in bits
471 uint ;; Dwarf type encoding
475 <p>These descriptors define primitive types used in the code. Example int, bool
476 and float. The context provides the scope of the type, which is usually the top
477 level. Since basic types are not usually user defined the compile unit and line
478 number can be left as NULL and 0. The size, alignment and offset are expressed
479 in bits and can be 64 bit values. The alignment is used to round the offset
480 when embedded in a <a href="#format_composite_type">composite type</a>
481 (example to keep float doubles on 64 bit boundaries.) The offset is the bit
482 offset if embedded in a <a href="#format_composite_type">composite
485 <p>The type encoding provides the details of the type. The values are typically
486 one of the following;</p>
493 DW_ATE_signed_char = 6
495 DW_ATE_unsigned_char = 8
500 <!-- ======================================================================= -->
501 <div class="doc_subsubsection">
502 <a name="format_derived_type">Derived type descriptors</a>
505 <div class="doc_text">
508 %<a href="#format_derived_type">llvm.dbg.derivedtype.type</a> = type {
509 uint, ;; Tag (see below)
510 { }*, ;; Reference to context
511 sbyte*, ;; Name (may be "" for anonymous types)
512 { }*, ;; Reference to compile unit where defined (may be NULL)
513 uint, ;; Line number where defined (may be 0)
514 uint, ;; Size in bits
515 uint, ;; Alignment in bits
516 uint, ;; Offset in bits
517 { }* ;; Reference to type derived from
521 <p>These descriptors are used to define types derived from other types. The
522 value of the tag varies depending on the meaning. The following are possible
526 DW_TAG_formal_parameter = 5
528 DW_TAG_pointer_type = 15
529 DW_TAG_reference_type = 16
531 DW_TAG_const_type = 38
532 DW_TAG_volatile_type = 53
533 DW_TAG_restrict_type = 55
536 <p> <tt>DW_TAG_member</tt> is used to define a member of a <a
537 href="#format_composite_type">composite type</a> or <a
538 href="#format_subprograms">subprogram</a>. The type of the member is the <a
539 href="#format_derived_type">derived type</a>. <tt>DW_TAG_formal_parameter</tt>
540 is used to define a member which is a formal argument of a subprogram.</p>
542 <p><tt>DW_TAG_typedef</tt> is used to
543 provide a name for the derived type.</p>
545 <p><tt>DW_TAG_pointer_type</tt>,
546 <tt>DW_TAG_reference_type</tt>, <tt>DW_TAG_const_type</tt>,
547 <tt>DW_TAG_volatile_type</tt> and <tt>DW_TAG_restrict_type</tt> are used to
548 qualify the <a href="#format_derived_type">derived type</a>. </p>
550 <p><a href="#format_derived_type">Derived type</a> location can be determined
551 from the compile unit and line number. The size, alignment and offset are
552 expressed in bits and can be 64 bit values. The alignment is used to round the
553 offset when embedded in a <a href="#format_composite_type">composite type</a>
554 (example to keep float doubles on 64 bit boundaries.) The offset is the bit
555 offset if embedded in a <a href="#format_composite_type">composite
558 <p>Note that the <tt>void *</tt> type is expressed as a
559 <tt>llvm.dbg.derivedtype.type</tt> with tag of <tt>DW_TAG_pointer_type</tt> and
560 NULL derived type.</p>
564 <!-- ======================================================================= -->
565 <div class="doc_subsubsection">
566 <a name="format_composite_type">Composite type descriptors</a>
569 <div class="doc_text">
572 %<a href="#format_composite_type">llvm.dbg.compositetype.type</a> = type {
573 uint, ;; Tag (see below)
574 { }*, ;; Reference to context
575 sbyte*, ;; Name (may be "" for anonymous types)
576 { }*, ;; Reference to compile unit where defined (may be NULL)
577 uint, ;; Line number where defined (may be 0)
578 uint, ;; Size in bits
579 uint, ;; Alignment in bits
580 uint, ;; Offset in bits
581 { }* ;; Reference to array of member descriptors
585 <p>These descriptors are used to define types that are composed of 0 or more
586 elements. The value of the tag varies depending on the meaning. The following
587 are possible tag values;</p>
590 DW_TAG_array_type = 1
591 DW_TAG_enumeration_type = 4
592 DW_TAG_structure_type = 19
593 DW_TAG_union_type = 23
594 DW_TAG_vector_type = 259
595 DW_TAG_subroutine_type = 46
596 DW_TAG_inheritance = 26
599 <p>The vector flag indicates that an array type is a native packed vector.</p>
601 <p>The members of array types (tag = <tt>DW_TAG_array_type</tt>) or vector types
602 (tag = <tt>DW_TAG_vector_type</tt>) are <a href="#format_subrange">subrange
603 descriptors</a>, each representing the range of subscripts at that level of
606 <p>The members of enumeration types (tag = <tt>DW_TAG_enumeration_type</tt>) are
607 <a href="#format_enumeration">enumerator descriptors</a>, each representing the
608 definition of enumeration value
611 <p>The members of structure (tag = <tt>DW_TAG_structure_type</tt>) or union (tag
612 = <tt>DW_TAG_union_type</tt>) types are any one of the <a
613 href="#format_basic_type">basic</a>, <a href="#format_derived_type">derived</a>
614 or <a href="#format_composite_type">composite</a> type descriptors, each
615 representing a field member of the structure or union.</p>
617 <p>For C++ classes (tag = <tt>DW_TAG_structure_type</tt>), member descriptors
618 provide information about base classes, static members and member functions. If
619 a member is a <a href="#format_derived_type">derived type descriptor</a> and has
620 a tag of <tt>DW_TAG_inheritance</tt>, then the type represents a base class. If
621 the member of is a <a href="#format_global_variables">global variable
622 descriptor</a> then it represents a static member. And, if the member is a <a
623 href="#format_subprograms">subprogram descriptor</a> then it represents a member
624 function. For static members and member functions, <tt>getName()</tt> returns
625 the members link or the C++ mangled name. <tt>getDisplayName()</tt> the
626 simplied version of the name.</p>
628 <p>The first member of subroutine (tag = <tt>DW_TAG_subroutine_type</tt>)
629 type elements is the return type for the subroutine. The remaining
630 elements are the formal arguments to the subroutine.</p>
632 <p><a href="#format_composite_type">Composite type</a> location can be
633 determined from the compile unit and line number. The size, alignment and
634 offset are expressed in bits and can be 64 bit values. The alignment is used to
635 round the offset when embedded in a <a href="#format_composite_type">composite
636 type</a> (as an example, to keep float doubles on 64 bit boundaries.) The offset
637 is the bit offset if embedded in a <a href="#format_composite_type">composite
642 <!-- ======================================================================= -->
643 <div class="doc_subsubsection">
644 <a name="format_subrange">Subrange descriptors</a>
647 <div class="doc_text">
650 %<a href="#format_subrange">llvm.dbg.subrange.type</a> = type {
651 uint, ;; Tag = 33 + <a href="#LLVMDebugVersion">LLVMDebugVersion</a> (DW_TAG_subrange_type)
657 <p>These descriptors are used to define ranges of array subscripts for an array
658 <a href="#format_composite_type">composite type</a>. The low value defines the
659 lower bounds typically zero for C/C++. The high value is the upper bounds.
660 Values are 64 bit. High - low + 1 is the size of the array. If
661 low == high the array will be unbounded.</p>
665 <!-- ======================================================================= -->
666 <div class="doc_subsubsection">
667 <a name="format_enumeration">Enumerator descriptors</a>
670 <div class="doc_text">
673 %<a href="#format_enumeration">llvm.dbg.enumerator.type</a> = type {
674 uint, ;; Tag = 40 + <a href="#LLVMDebugVersion">LLVMDebugVersion</a> (DW_TAG_enumerator)
680 <p>These descriptors are used to define members of an enumeration <a
681 href="#format_composite_type">composite type</a>, it associates the name to the
686 <!-- ======================================================================= -->
687 <div class="doc_subsubsection">
688 <a name="format_variables">Local variables</a>
691 <div class="doc_text">
693 %<a href="#format_variables">llvm.dbg.variable.type</a> = type {
694 uint, ;; Tag (see below)
697 { }*, ;; Reference to compile unit where defined
698 uint, ;; Line number where defined
699 { }* ;; Type descriptor
703 <p>These descriptors are used to define variables local to a sub program. The
704 value of the tag depends on the usage of the variable;</p>
707 DW_TAG_auto_variable = 256
708 DW_TAG_arg_variable = 257
709 DW_TAG_return_variable = 258
712 <p>An auto variable is any variable declared in the body of the function. An
713 argument variable is any variable that appears as a formal argument to the
714 function. A return variable is used to track the result of a function and has
715 no source correspondent.</p>
717 <p>The context is either the subprogram or block where the variable is defined.
718 Name the source variable name. Compile unit and line indicate where the
719 variable was defined. Type descriptor defines the declared type of the
724 <!-- ======================================================================= -->
725 <div class="doc_subsection">
726 <a name="format_common_intrinsics">Debugger intrinsic functions</a>
729 <div class="doc_text">
731 <p>LLVM uses several intrinsic functions (name prefixed with "llvm.dbg") to
732 provide debug information at various points in generated code.</p>
736 <!-- ======================================================================= -->
737 <div class="doc_subsubsection">
738 <a name="format_common_stoppoint">llvm.dbg.stoppoint</a>
741 <div class="doc_text">
743 void %<a href="#format_common_stoppoint">llvm.dbg.stoppoint</a>( uint, uint, { }* )
746 <p>This intrinsic is used to provide correspondence between the source file and
747 the generated code. The first argument is the line number (base 1), second
748 argument si the column number (0 if unknown) and the third argument the source
749 <tt>%<a href="#format_compile_units">llvm.dbg.compile_unit</a>*</tt> cast to a
750 <tt>{ }*</tt>. Code following a call to this intrinsic will have been defined
751 in close proximity of the line, column and file. This information holds until
752 the next call to <tt>%<a
753 href="#format_common_stoppoint">lvm.dbg.stoppoint</a></tt>.</p>
757 <!-- ======================================================================= -->
758 <div class="doc_subsubsection">
759 <a name="format_common_func_start">llvm.dbg.func.start</a>
762 <div class="doc_text">
764 void %<a href="#format_common_func_start">llvm.dbg.func.start</a>( { }* )
767 <p>This intrinsic is used to link the debug information in <tt>%<a
768 href="#format_subprograms">llvm.dbg.subprogram</a></tt> to the function. It also
769 defines the beginning of the function's declarative region (scope.) The
770 intrinsic should be called early in the function after the all the alloca
771 instructions. It should be paired off with a closing <tt>%<a
772 href="#format_common_region_end">llvm.dbg.region.end</a></tt>. The function's
773 single argument is the <tt>%<a
774 href="#format_subprograms">llvm.dbg.subprogram.type</a></tt>.</p>
778 <!-- ======================================================================= -->
779 <div class="doc_subsubsection">
780 <a name="format_common_region_start">llvm.dbg.region.start</a>
783 <div class="doc_text">
785 void %<a href="#format_common_region_start">llvm.dbg.region.start</a>( { }* )
788 <p>This intrinsic is used to define the beginning of a declarative scope (ex.
789 block) for local language elements. It should be paired off with a closing
790 <tt>%<a href="#format_common_region_end">llvm.dbg.region.end</a></tt>. The
791 function's single argument is the <tt>%<a
792 href="#format_blocks">llvm.dbg.block</a></tt> which is starting.</p>
797 <!-- ======================================================================= -->
798 <div class="doc_subsubsection">
799 <a name="format_common_region_end">llvm.dbg.region.end</a>
802 <div class="doc_text">
804 void %<a href="#format_common_region_end">llvm.dbg.region.end</a>( { }* )
807 <p>This intrinsic is used to define the end of a declarative scope (ex. block)
808 for local language elements. It should be paired off with an opening <tt>%<a
809 href="#format_common_region_start">llvm.dbg.region.start</a></tt> or <tt>%<a
810 href="#format_common_func_start">llvm.dbg.func.start</a></tt>. The function's
811 single argument is either the <tt>%<a
812 href="#format_blocks">llvm.dbg.block</a></tt> or the <tt>%<a
813 href="#format_subprograms">llvm.dbg.subprogram.type</a></tt> which is
818 <!-- ======================================================================= -->
819 <div class="doc_subsubsection">
820 <a name="format_common_declare">llvm.dbg.declare</a>
823 <div class="doc_text">
825 void %<a href="#format_common_declare">llvm.dbg.declare</a>( { } *, { }* )
828 <p>This intrinsic provides information about a local element (ex. variable.) The
829 first argument is the alloca for the variable, cast to a <tt>{ }*</tt>. The
830 second argument is the <tt>%<a
831 href="#format_variables">llvm.dbg.variable</a></tt> containing the description
832 of the variable, also cast to a <tt>{ }*</tt>.</p>
836 <!-- ======================================================================= -->
837 <div class="doc_subsection">
838 <a name="format_common_stoppoints">
839 Representing stopping points in the source program
843 <div class="doc_text">
845 <p>LLVM debugger "stop points" are a key part of the debugging representation
846 that allows the LLVM to maintain simple semantics for <a
847 href="#debugopt">debugging optimized code</a>. The basic idea is that the
848 front-end inserts calls to the <a
849 href="#format_common_stoppoint">%<tt>llvm.dbg.stoppoint</tt></a> intrinsic
850 function at every point in the program where a debugger should be able to
851 inspect the program (these correspond to places a debugger stops when you
852 "<tt>step</tt>" through it). The front-end can choose to place these as
853 fine-grained as it would like (for example, before every subexpression
854 evaluated), but it is recommended to only put them after every source statement
855 that includes executable code.</p>
857 <p>Using calls to this intrinsic function to demark legal points for the
858 debugger to inspect the program automatically disables any optimizations that
859 could potentially confuse debugging information. To non-debug-information-aware
860 transformations, these calls simply look like calls to an external function,
861 which they must assume to do anything (including reading or writing to any part
862 of reachable memory). On the other hand, it does not impact many optimizations,
863 such as code motion of non-trapping instructions, nor does it impact
864 optimization of subexpressions, code duplication transformations, or basic-block
865 reordering transformations.</p>
870 <!-- ======================================================================= -->
871 <div class="doc_subsection">
872 <a name="format_common_lifetime">Object lifetimes and scoping</a>
875 <div class="doc_text">
876 <p>In many languages, the local variables in functions can have their lifetime
877 or scope limited to a subset of a function. In the C family of languages, for
878 example, variables are only live (readable and writable) within the source block
879 that they are defined in. In functional languages, values are only readable
880 after they have been defined. Though this is a very obvious concept, it is also
881 non-trivial to model in LLVM, because it has no notion of scoping in this sense,
882 and does not want to be tied to a language's scoping rules.</p>
884 <p>In order to handle this, the LLVM debug format uses the notion of "regions"
885 of a function, delineated by calls to intrinsic functions. These intrinsic
886 functions define new regions of the program and indicate when the region
887 lifetime expires. Consider the following C fragment, for example:</p>
901 <p>Compiled to LLVM, this function would be represented like this:</p>
912 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 )
914 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 )
916 call void %<a href="#format_common_declare">llvm.dbg.declare</a>({}* %X, ...)
917 call void %<a href="#format_common_declare">llvm.dbg.declare</a>({}* %Y, ...)
919 <i>;; Evaluate expression on line 2, assigning to X.</i>
921 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 )
923 <i>;; Evaluate expression on line 3, assigning to Y.</i>
925 call void %<a href="#format_common_stoppoint">llvm.region.start</a>()
926 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 )
927 call void %<a href="#format_common_declare">llvm.dbg.declare</a>({}* %X, ...)
929 <i>;; Evaluate expression on line 5, assigning to Z.</i>
931 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 )
932 call void %<a href="#format_common_region_end">llvm.region.end</a>()
934 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 )
936 call void %<a href="#format_common_region_end">llvm.region.end</a>()
942 <p>This example illustrates a few important details about the LLVM debugging
943 information. In particular, it shows how the various intrinsics are applied
944 together to allow a debugger to analyze the relationship between statements,
945 variable definitions, and the code used to implement the function.</p>
947 <p>The first intrinsic <tt>%<a
948 href="#format_common_func_start">llvm.dbg.func.start</a></tt> provides
949 a link with the <a href="#format_subprograms">subprogram descriptor</a>
950 containing the details of this function. This call also defines the beginning
951 of the function region, bounded by the <tt>%<a
952 href="#format_common_region_end">llvm.region.end</a></tt> at the end of
953 the function. This region is used to bracket the lifetime of variables declared
954 within. For a function, this outer region defines a new stack frame whose
955 lifetime ends when the region is ended.</p>
957 <p>It is possible to define inner regions for short term variables by using the
958 %<a href="#format_common_stoppoint"><tt>llvm.region.start</tt></a> and <a
959 href="#format_common_region_end"><tt>%llvm.region.end</tt></a> to bound a
960 region. The inner region in this example would be for the block containing the
961 declaration of Z.</p>
963 <p>Using regions to represent the boundaries of source-level functions allow
964 LLVM interprocedural optimizations to arbitrarily modify LLVM functions without
965 having to worry about breaking mapping information between the LLVM code and the
966 and source-level program. In particular, the inliner requires no modification
967 to support inlining with debugging information: there is no explicit correlation
968 drawn between LLVM functions and their source-level counterparts (note however,
969 that if the inliner inlines all instances of a non-strong-linkage function into
970 its caller that it will not be possible for the user to manually invoke the
971 inlined function from a debugger).</p>
973 <p>Once the function has been defined, the <a
974 href="#format_common_stoppoint"><tt>stopping point</tt></a> corresponding to
975 line #2 (column #2) of the function is encountered. At this point in the
976 function, <b>no</b> local variables are live. As lines 2 and 3 of the example
977 are executed, their variable definitions are introduced into the program using
978 %<a href="#format_common_declare"><tt>llvm.dbg.declare</tt></a>, without the
979 need to specify a new region. These variables do not require new regions to be
980 introduced because they go out of scope at the same point in the program: line
983 <p>In contrast, the <tt>Z</tt> variable goes out of scope at a different time,
984 on line 7. For this reason, it is defined within the inner region, which kills
985 the availability of <tt>Z</tt> before the code for line 8 is executed. In this
986 way, regions can support arbitrary source-language scoping rules, as long as
987 they can only be nested (ie, one scope cannot partially overlap with a part of
990 <p>It is worth noting that this scoping mechanism is used to control scoping of
991 all declarations, not just variable declarations. For example, the scope of a
992 C++ using declaration is controlled with this couldchange how name lookup is
999 <!-- *********************************************************************** -->
1000 <div class="doc_section">
1001 <a name="ccxx_frontend">C/C++ front-end specific debug information</a>
1003 <!-- *********************************************************************** -->
1005 <div class="doc_text">
1007 <p>The C and C++ front-ends represent information about the program in a format
1008 that is effectively identical to <a
1009 href="http://www.eagercon.com/dwarf/dwarf3std.htm">Dwarf 3.0</a> in terms of
1010 information content. This allows code generators to trivially support native
1011 debuggers by generating standard dwarf information, and contains enough
1012 information for non-dwarf targets to translate it as needed.</p>
1014 <p>This section describes the forms used to represent C and C++ programs. Other
1015 languages could pattern themselves after this (which itself is tuned to
1016 representing programs in the same way that Dwarf 3 does), or they could choose
1017 to provide completely different forms if they don't fit into the Dwarf model.
1018 As support for debugging information gets added to the various LLVM
1019 source-language front-ends, the information used should be documented here.</p>
1021 <p>The following sections provide examples of various C/C++ constructs and the
1022 debug information that would best describe those constructs.</p>
1026 <!-- ======================================================================= -->
1027 <div class="doc_subsection">
1028 <a name="ccxx_compile_units">C/C++ source file information</a>
1031 <div class="doc_text">
1033 <p>Given the source files "MySource.cpp" and "MyHeader.h" located in the
1034 directory "/Users/mine/sources", the following code;</p>
1037 #include "MyHeader.h"
1039 int main(int argc, char *argv[]) {
1044 <p>a C/C++ front-end would generate the following descriptors;</p>
1049 ;; Define types used. In this case we need one for compile unit anchors and one
1050 ;; for compile units.
1052 %<a href="#format_anchors">llvm.dbg.anchor.type</a> = type { uint, uint }
1053 %<a href="#format_compile_units">llvm.dbg.compile_unit.type</a> = type { uint, { }*, uint, uint, sbyte*, sbyte*, sbyte* }
1056 ;; Define the anchor for compile units. Note that the second field of the
1057 ;; anchor is 17, which is the same as the tag for compile units
1058 ;; (17 = DW_TAG_compile_unit.)
1060 %<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"
1063 ;; Define the compile unit for the source file "/Users/mine/sources/MySource.cpp".
1065 %<a href="#format_compile_units">llvm.dbg.compile_unit1</a> = internal constant %<a href="#format_compile_units">llvm.dbg.compile_unit.type</a> {
1066 uint add(uint 17, uint 262144),
1067 { }* cast (%<a href="#format_anchors">llvm.dbg.anchor.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_units</a> to { }*),
1070 sbyte* getelementptr ([13 x sbyte]* %str1, int 0, int 0),
1071 sbyte* getelementptr ([21 x sbyte]* %str2, int 0, int 0),
1072 sbyte* getelementptr ([33 x sbyte]* %str3, int 0, int 0) }, section "llvm.metadata"
1075 ;; Define the compile unit for the header file "/Users/mine/sources/MyHeader.h".
1077 %<a href="#format_compile_units">llvm.dbg.compile_unit2</a> = internal constant %<a href="#format_compile_units">llvm.dbg.compile_unit.type</a> {
1078 uint add(uint 17, uint 262144),
1079 { }* cast (%<a href="#format_anchors">llvm.dbg.anchor.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_units</a> to { }*),
1082 sbyte* getelementptr ([11 x sbyte]* %str4, int 0, int 0),
1083 sbyte* getelementptr ([21 x sbyte]* %str2, int 0, int 0),
1084 sbyte* getelementptr ([33 x sbyte]* %str3, int 0, int 0) }, section "llvm.metadata"
1087 ;; Define each of the strings used in the compile units.
1089 %str1 = internal constant [13 x sbyte] c"MySource.cpp\00", section "llvm.metadata";
1090 %str2 = internal constant [21 x sbyte] c"/Users/mine/sources/\00", section "llvm.metadata";
1091 %str3 = internal constant [33 x sbyte] c"4.0.1 LLVM (LLVM research group)\00", section "llvm.metadata";
1092 %str4 = internal constant [11 x sbyte] c"MyHeader.h\00", section "llvm.metadata";
1098 <!-- ======================================================================= -->
1099 <div class="doc_subsection">
1100 <a name="ccxx_global_variable">C/C++ global variable information</a>
1103 <div class="doc_text">
1105 <p>Given an integer global variable declared as follows;</p>
1111 <p>a C/C++ front-end would generate the following descriptors;</p>
1115 ;; Define types used. One for global variable anchors, one for the global
1116 ;; variable descriptor, one for the global's basic type and one for the global's
1119 %<a href="#format_anchors">llvm.dbg.anchor.type</a> = type { uint, uint }
1120 %<a href="#format_global_variables">llvm.dbg.global_variable.type</a> = type { uint, { }*, { }*, sbyte*, { }*, uint, { }*, bool, bool, { }*, uint }
1121 %<a href="#format_basic_type">llvm.dbg.basictype.type</a> = type { uint, { }*, sbyte*, { }*, int, uint, uint, uint, uint }
1122 %<a href="#format_compile_units">llvm.dbg.compile_unit.type</a> = ...
1125 ;; Define the global itself.
1127 %MyGlobal = global int 100
1130 ;; Define the anchor for global variables. Note that the second field of the
1131 ;; anchor is 52, which is the same as the tag for global variables
1132 ;; (52 = DW_TAG_variable.)
1134 %<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"
1137 ;; Define the global variable descriptor. Note the reference to the global
1138 ;; variable anchor and the global variable itself.
1140 %<a href="#format_global_variables">llvm.dbg.global_variable</a> = internal constant %<a href="#format_global_variables">llvm.dbg.global_variable.type</a> {
1141 uint add(uint 52, uint 262144),
1142 { }* cast (%<a href="#format_anchors">llvm.dbg.anchor.type</a>* %<a href="#format_global_variables">llvm.dbg.global_variables</a> to { }*),
1143 { }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to { }*),
1144 sbyte* getelementptr ([9 x sbyte]* %str1, int 0, int 0),
1145 sbyte* getelementptr ([1 x sbyte]* %str2, int 0, int 0),
1146 { }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to { }*),
1148 { }* cast (%<a href="#format_basic_type">llvm.dbg.basictype.type</a>* %<a href="#format_basic_type">llvm.dbg.basictype</a> to { }*),
1151 { }* cast (int* %MyGlobal to { }*) }, section "llvm.metadata"
1154 ;; Define the basic type of 32 bit signed integer. Note that since int is an
1155 ;; intrinsic type the source file is NULL and line 0.
1157 %<a href="#format_basic_type">llvm.dbg.basictype</a> = internal constant %<a href="#format_basic_type">llvm.dbg.basictype.type</a> {
1158 uint add(uint 36, uint 262144),
1159 { }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to { }*),
1160 sbyte* getelementptr ([4 x sbyte]* %str3, int 0, int 0),
1166 uint 5 }, section "llvm.metadata"
1169 ;; Define the names of the global variable and basic type.
1171 %str1 = internal constant [9 x sbyte] c"MyGlobal\00", section "llvm.metadata"
1172 %str2 = internal constant [1 x sbyte] c"\00", section "llvm.metadata"
1173 %str3 = internal constant [4 x sbyte] c"int\00", section "llvm.metadata"
1178 <!-- ======================================================================= -->
1179 <div class="doc_subsection">
1180 <a name="ccxx_subprogram">C/C++ function information</a>
1183 <div class="doc_text">
1185 <p>Given a function declared as follows;</p>
1188 int main(int argc, char *argv[]) {
1193 <p>a C/C++ front-end would generate the following descriptors;</p>
1197 ;; Define types used. One for subprogram anchors, one for the subprogram
1198 ;; descriptor, one for the global's basic type and one for the subprogram's
1201 %<a href="#format_subprograms">llvm.dbg.subprogram.type</a> = type { uint, { }*, { }*, sbyte*, { }*, bool, bool }
1202 %<a href="#format_anchors">llvm.dbg.anchor.type</a> = type { uint, uint }
1203 %<a href="#format_compile_units">llvm.dbg.compile_unit.type</a> = ...
1206 ;; Define the anchor for subprograms. Note that the second field of the
1207 ;; anchor is 46, which is the same as the tag for subprograms
1208 ;; (46 = DW_TAG_subprogram.)
1210 %<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"
1213 ;; Define the descriptor for the subprogram. TODO - more details.
1215 %<a href="#format_subprograms">llvm.dbg.subprogram</a> = internal constant %<a href="#format_subprograms">llvm.dbg.subprogram.type</a> {
1216 uint add(uint 46, uint 262144),
1217 { }* cast (%<a href="#format_anchors">llvm.dbg.anchor.type</a>* %<a href="#format_subprograms">llvm.dbg.subprograms</a> to { }*),
1218 { }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to { }*),
1219 sbyte* getelementptr ([5 x sbyte]* %str1, int 0, int 0),
1220 sbyte* getelementptr ([1 x sbyte]* %str2, int 0, int 0),
1221 { }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to { }*),
1225 bool true }, section "llvm.metadata"
1228 ;; Define the name of the subprogram.
1230 %str1 = internal constant [5 x sbyte] c"main\00", section "llvm.metadata"
1231 %str2 = internal constant [1 x sbyte] c"\00", section "llvm.metadata"
1234 ;; Define the subprogram itself.
1236 int %main(int %argc, sbyte** %argv) {
1243 <!-- ======================================================================= -->
1244 <div class="doc_subsection">
1245 <a name="ccxx_basic_types">C/C++ basic types</a>
1248 <div class="doc_text">
1250 <p>The following are the basic type descriptors for C/C++ core types;</p>
1254 <!-- ======================================================================= -->
1255 <div class="doc_subsubsection">
1256 <a name="ccxx_basic_type_bool">bool</a>
1259 <div class="doc_text">
1262 %<a href="#format_basic_type">llvm.dbg.basictype</a> = internal constant %<a href="#format_basic_type">llvm.dbg.basictype.type</a> {
1263 uint add(uint 36, uint 262144),
1264 { }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to { }*),
1265 sbyte* getelementptr ([5 x sbyte]* %str1, int 0, int 0),
1271 uint 2 }, section "llvm.metadata"
1272 %str1 = internal constant [5 x sbyte] c"bool\00", section "llvm.metadata"
1277 <!-- ======================================================================= -->
1278 <div class="doc_subsubsection">
1279 <a name="ccxx_basic_char">char</a>
1282 <div class="doc_text">
1285 %<a href="#format_basic_type">llvm.dbg.basictype</a> = internal constant %<a href="#format_basic_type">llvm.dbg.basictype.type</a> {
1286 uint add(uint 36, uint 262144),
1287 { }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to { }*),
1288 sbyte* getelementptr ([5 x sbyte]* %str1, int 0, int 0),
1294 uint 6 }, section "llvm.metadata"
1295 %str1 = internal constant [5 x sbyte] c"char\00", section "llvm.metadata"
1300 <!-- ======================================================================= -->
1301 <div class="doc_subsubsection">
1302 <a name="ccxx_basic_unsigned_char">unsigned char</a>
1305 <div class="doc_text">
1308 %<a href="#format_basic_type">llvm.dbg.basictype</a> = internal constant %<a href="#format_basic_type">llvm.dbg.basictype.type</a> {
1309 uint add(uint 36, uint 262144),
1310 { }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to { }*),
1311 sbyte* getelementptr ([14 x sbyte]* %str1, int 0, int 0),
1317 uint 8 }, section "llvm.metadata"
1318 %str1 = internal constant [14 x sbyte] c"unsigned char\00", section "llvm.metadata"
1323 <!-- ======================================================================= -->
1324 <div class="doc_subsubsection">
1325 <a name="ccxx_basic_short">short</a>
1328 <div class="doc_text">
1331 %<a href="#format_basic_type">llvm.dbg.basictype</a> = internal constant %<a href="#format_basic_type">llvm.dbg.basictype.type</a> {
1332 uint add(uint 36, uint 262144),
1333 { }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to { }*),
1334 sbyte* getelementptr ([10 x sbyte]* %str1, int 0, int 0),
1340 uint 5 }, section "llvm.metadata"
1341 %str1 = internal constant [10 x sbyte] c"short int\00", section "llvm.metadata"
1346 <!-- ======================================================================= -->
1347 <div class="doc_subsubsection">
1348 <a name="ccxx_basic_unsigned_short">unsigned short</a>
1351 <div class="doc_text">
1354 %<a href="#format_basic_type">llvm.dbg.basictype</a> = internal constant %<a href="#format_basic_type">llvm.dbg.basictype.type</a> {
1355 uint add(uint 36, uint 262144),
1356 { }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to { }*),
1357 sbyte* getelementptr ([19 x sbyte]* %str1, int 0, int 0),
1363 uint 7 }, section "llvm.metadata"
1364 %str1 = internal constant [19 x sbyte] c"short unsigned int\00", section "llvm.metadata"
1369 <!-- ======================================================================= -->
1370 <div class="doc_subsubsection">
1371 <a name="ccxx_basic_int">int</a>
1374 <div class="doc_text">
1377 %<a href="#format_basic_type">llvm.dbg.basictype</a> = internal constant %<a href="#format_basic_type">llvm.dbg.basictype.type</a> {
1378 uint add(uint 36, uint 262144),
1379 { }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to { }*),
1380 sbyte* getelementptr ([4 x sbyte]* %str1, int 0, int 0),
1386 uint 5 }, section "llvm.metadata"
1387 %str1 = internal constant [4 x sbyte] c"int\00", section "llvm.metadata"
1392 <!-- ======================================================================= -->
1393 <div class="doc_subsubsection">
1394 <a name="ccxx_basic_unsigned_int">unsigned int</a>
1397 <div class="doc_text">
1400 %<a href="#format_basic_type">llvm.dbg.basictype</a> = internal constant %<a href="#format_basic_type">llvm.dbg.basictype.type</a> {
1401 uint add(uint 36, uint 262144),
1402 { }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to { }*),
1403 sbyte* getelementptr ([13 x sbyte]* %str1, int 0, int 0),
1409 uint 7 }, section "llvm.metadata"
1410 %str1 = internal constant [13 x sbyte] c"unsigned int\00", section "llvm.metadata"
1415 <!-- ======================================================================= -->
1416 <div class="doc_subsubsection">
1417 <a name="ccxx_basic_long_long">long long</a>
1420 <div class="doc_text">
1423 %<a href="#format_basic_type">llvm.dbg.basictype</a> = internal constant %<a href="#format_basic_type">llvm.dbg.basictype.type</a> {
1424 uint add(uint 36, uint 262144),
1425 { }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to { }*),
1426 sbyte* getelementptr ([14 x sbyte]* %str1, int 0, int 0),
1432 uint 5 }, section "llvm.metadata"
1433 %str1 = internal constant [14 x sbyte] c"long long int\00", section "llvm.metadata"
1438 <!-- ======================================================================= -->
1439 <div class="doc_subsubsection">
1440 <a name="ccxx_basic_unsigned_long_long">unsigned long long</a>
1443 <div class="doc_text">
1446 %<a href="#format_basic_type">llvm.dbg.basictype</a> = internal constant %<a href="#format_basic_type">llvm.dbg.basictype.type</a> {
1447 uint add(uint 36, uint 262144),
1448 { }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to { }*),
1449 sbyte* getelementptr ([23 x sbyte]* %str1, int 0, int 0),
1455 uint 7 }, section "llvm.metadata"
1456 %str1 = internal constant [23 x sbyte] c"long long unsigned int\00", section "llvm.metadata"
1461 <!-- ======================================================================= -->
1462 <div class="doc_subsubsection">
1463 <a name="ccxx_basic_float">float</a>
1466 <div class="doc_text">
1469 %<a href="#format_basic_type">llvm.dbg.basictype</a> = internal constant %<a href="#format_basic_type">llvm.dbg.basictype.type</a> {
1470 uint add(uint 36, uint 262144),
1471 { }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to { }*),
1472 sbyte* getelementptr ([6 x sbyte]* %str1, int 0, int 0),
1478 uint 4 }, section "llvm.metadata"
1479 %str1 = internal constant [6 x sbyte] c"float\00", section "llvm.metadata"
1484 <!-- ======================================================================= -->
1485 <div class="doc_subsubsection">
1486 <a name="ccxx_basic_double">double</a>
1489 <div class="doc_text">
1492 %<a href="#format_basic_type">llvm.dbg.basictype</a> = internal constant %<a href="#format_basic_type">llvm.dbg.basictype.type</a> {
1493 uint add(uint 36, uint 262144),
1494 { }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to { }*),
1495 sbyte* getelementptr ([7 x sbyte]* %str1, int 0, int 0),
1501 uint 4 }, section "llvm.metadata"
1502 %str1 = internal constant [7 x sbyte] c"double\00", section "llvm.metadata"
1507 <!-- ======================================================================= -->
1508 <div class="doc_subsection">
1509 <a name="ccxx_derived_types">C/C++ derived types</a>
1512 <div class="doc_text">
1514 <p>Given the following as an example of C/C++ derived type;</p>
1517 typedef const int *IntPtr;
1520 <p>a C/C++ front-end would generate the following descriptors;</p>
1524 ;; Define the typedef "IntPtr".
1526 %<a href="#format_derived_type">llvm.dbg.derivedtype1</a> = internal constant %<a href="#format_derived_type">llvm.dbg.derivedtype.type</a> {
1527 uint add(uint 22, uint 262144),
1528 { }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to { }*),
1529 sbyte* getelementptr ([7 x sbyte]* %str1, int 0, int 0),
1530 { }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to { }*),
1535 { }* cast (%<a href="#format_derived_type">llvm.dbg.derivedtype.type</a>* %<a href="#format_derived_type">llvm.dbg.derivedtype2</a> to { }*) }, section "llvm.metadata"
1536 %str1 = internal constant [7 x sbyte] c"IntPtr\00", section "llvm.metadata"
1539 ;; Define the pointer type.
1541 %<a href="#format_derived_type">llvm.dbg.derivedtype2</a> = internal constant %<a href="#format_derived_type">llvm.dbg.derivedtype.type</a> {
1542 uint add(uint 15, uint 262144),
1543 { }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to { }*),
1550 { }* cast (%<a href="#format_derived_type">llvm.dbg.derivedtype.type</a>* %<a href="#format_derived_type">llvm.dbg.derivedtype3</a> to { }*) }, section "llvm.metadata"
1553 ;; Define the const type.
1555 %<a href="#format_derived_type">llvm.dbg.derivedtype3</a> = internal constant %<a href="#format_derived_type">llvm.dbg.derivedtype.type</a> {
1556 uint add(uint 38, uint 262144),
1557 { }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to { }*),
1564 { }* cast (%<a href="#format_basic_type">llvm.dbg.basictype.type</a>* %<a href="#format_basic_type">llvm.dbg.basictype1</a> to { }*) }, section "llvm.metadata"
1567 ;; Define the int type.
1569 %<a href="#format_basic_type">llvm.dbg.basictype1</a> = internal constant %<a href="#format_basic_type">llvm.dbg.basictype.type</a> {
1570 uint add(uint 36, uint 262144),
1571 { }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to { }*),
1572 sbyte* getelementptr ([4 x sbyte]* %str2, int 0, int 0),
1578 uint 5 }, section "llvm.metadata"
1579 %str2 = internal constant [4 x sbyte] c"int\00", section "llvm.metadata"
1584 <!-- ======================================================================= -->
1585 <div class="doc_subsection">
1586 <a name="ccxx_composite_types">C/C++ struct/union types</a>
1589 <div class="doc_text">
1591 <p>Given the following as an example of C/C++ struct type;</p>
1601 <p>a C/C++ front-end would generate the following descriptors;</p>
1605 ;; Define basic type for unsigned int.
1607 %<a href="#format_basic_type">llvm.dbg.basictype</a> = internal constant %<a href="#format_basic_type">llvm.dbg.basictype.type</a> {
1608 uint add(uint 36, uint 262144),
1609 { }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to { }*),
1610 sbyte* getelementptr ([13 x sbyte]* %str1, int 0, int 0),
1616 uint 7 }, section "llvm.metadata"
1617 %str1 = internal constant [13 x sbyte] c"unsigned int\00", section "llvm.metadata"
1620 ;; Define composite type for struct Color.
1622 %<a href="#format_composite_type">llvm.dbg.compositetype</a> = internal constant %<a href="#format_composite_type">llvm.dbg.compositetype.type</a> {
1623 uint add(uint 19, uint 262144),
1624 { }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to { }*),
1625 sbyte* getelementptr ([6 x sbyte]* %str2, int 0, int 0),
1626 { }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to { }*),
1632 { }* cast ([3 x { }*]* %llvm.dbg.array to { }*) }, section "llvm.metadata"
1633 %str2 = internal constant [6 x sbyte] c"Color\00", section "llvm.metadata"
1636 ;; Define the Red field.
1638 %<a href="#format_derived_type">llvm.dbg.derivedtype1</a> = internal constant %<a href="#format_derived_type">llvm.dbg.derivedtype.type</a> {
1639 uint add(uint 13, uint 262144),
1641 sbyte* getelementptr ([4 x sbyte]* %str3, int 0, int 0),
1642 { }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to { }*),
1647 { }* cast (%<a href="#format_basic_type">llvm.dbg.basictype.type</a>* %<a href="#format_basic_type">llvm.dbg.basictype</a> to { }*) }, section "llvm.metadata"
1648 %str3 = internal constant [4 x sbyte] c"Red\00", section "llvm.metadata"
1651 ;; Define the Green field.
1653 %<a href="#format_derived_type">llvm.dbg.derivedtype2</a> = internal constant %<a href="#format_derived_type">llvm.dbg.derivedtype.type</a> {
1654 uint add(uint 13, uint 262144),
1656 sbyte* getelementptr ([6 x sbyte]* %str4, int 0, int 0),
1657 { }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to { }*),
1662 { }* cast (%<a href="#format_basic_type">llvm.dbg.basictype.type</a>* %<a href="#format_basic_type">llvm.dbg.basictype</a> to { }*) }, section "llvm.metadata"
1663 %str4 = internal constant [6 x sbyte] c"Green\00", section "llvm.metadata"
1666 ;; Define the Blue field.
1668 %<a href="#format_derived_type">llvm.dbg.derivedtype3</a> = internal constant %<a href="#format_derived_type">llvm.dbg.derivedtype.type</a> {
1669 uint add(uint 13, uint 262144),
1671 sbyte* getelementptr ([5 x sbyte]* %str5, int 0, int 0),
1672 { }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to { }*),
1677 { }* cast (%<a href="#format_basic_type">llvm.dbg.basictype.type</a>* %<a href="#format_basic_type">llvm.dbg.basictype</a> to { }*) }, section "llvm.metadata"
1678 %str5 = internal constant [5 x sbyte] c"Blue\00", section "llvm.metadata"
1681 ;; Define the array of fields used by the composite type Color.
1683 %llvm.dbg.array = internal constant [3 x { }*] [
1684 { }* cast (%<a href="#format_derived_type">llvm.dbg.derivedtype.type</a>* %<a href="#format_derived_type">llvm.dbg.derivedtype1</a> to { }*),
1685 { }* cast (%<a href="#format_derived_type">llvm.dbg.derivedtype.type</a>* %<a href="#format_derived_type">llvm.dbg.derivedtype2</a> to { }*),
1686 { }* cast (%<a href="#format_derived_type">llvm.dbg.derivedtype.type</a>* %<a href="#format_derived_type">llvm.dbg.derivedtype3</a> to { }*) ], section "llvm.metadata"
1691 <!-- ======================================================================= -->
1692 <div class="doc_subsection">
1693 <a name="ccxx_enumeration_types">C/C++ enumeration types</a>
1696 <div class="doc_text">
1698 <p>Given the following as an example of C/C++ enumeration type;</p>
1708 <p>a C/C++ front-end would generate the following descriptors;</p>
1712 ;; Define composite type for enum Trees
1714 %<a href="#format_composite_type">llvm.dbg.compositetype</a> = internal constant %<a href="#format_composite_type">llvm.dbg.compositetype.type</a> {
1715 uint add(uint 4, uint 262144),
1716 { }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to { }*),
1717 sbyte* getelementptr ([6 x sbyte]* %str1, int 0, int 0),
1718 { }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to { }*),
1724 { }* cast ([3 x { }*]* %llvm.dbg.array to { }*) }, section "llvm.metadata"
1725 %str1 = internal constant [6 x sbyte] c"Trees\00", section "llvm.metadata"
1728 ;; Define Spruce enumerator.
1730 %<a href="#format_enumeration">llvm.dbg.enumerator1</a> = internal constant %<a href="#format_enumeration">llvm.dbg.enumerator.type</a> {
1731 uint add(uint 40, uint 262144),
1732 sbyte* getelementptr ([7 x sbyte]* %str2, int 0, int 0),
1733 int 100 }, section "llvm.metadata"
1734 %str2 = internal constant [7 x sbyte] c"Spruce\00", section "llvm.metadata"
1737 ;; Define Oak enumerator.
1739 %<a href="#format_enumeration">llvm.dbg.enumerator2</a> = internal constant %<a href="#format_enumeration">llvm.dbg.enumerator.type</a> {
1740 uint add(uint 40, uint 262144),
1741 sbyte* getelementptr ([4 x sbyte]* %str3, int 0, int 0),
1742 int 200 }, section "llvm.metadata"
1743 %str3 = internal constant [4 x sbyte] c"Oak\00", section "llvm.metadata"
1746 ;; Define Maple enumerator.
1748 %<a href="#format_enumeration">llvm.dbg.enumerator3</a> = internal constant %<a href="#format_enumeration">llvm.dbg.enumerator.type</a> {
1749 uint add(uint 40, uint 262144),
1750 sbyte* getelementptr ([6 x sbyte]* %str4, int 0, int 0),
1751 int 300 }, section "llvm.metadata"
1752 %str4 = internal constant [6 x sbyte] c"Maple\00", section "llvm.metadata"
1755 ;; Define the array of enumerators used by composite type Trees.
1757 %llvm.dbg.array = internal constant [3 x { }*] [
1758 { }* cast (%<a href="#format_enumeration">llvm.dbg.enumerator.type</a>* %<a href="#format_enumeration">llvm.dbg.enumerator1</a> to { }*),
1759 { }* cast (%<a href="#format_enumeration">llvm.dbg.enumerator.type</a>* %<a href="#format_enumeration">llvm.dbg.enumerator2</a> to { }*),
1760 { }* cast (%<a href="#format_enumeration">llvm.dbg.enumerator.type</a>* %<a href="#format_enumeration">llvm.dbg.enumerator3</a> to { }*) ], section "llvm.metadata"
1765 <!-- *********************************************************************** -->
1769 <a href="http://jigsaw.w3.org/css-validator/check/referer"><img
1770 src="http://jigsaw.w3.org/css-validator/images/vcss" alt="Valid CSS!"></a>
1771 <a href="http://validator.w3.org/check/referer"><img
1772 src="http://www.w3.org/Icons/valid-html401" alt="Valid HTML 4.01!"></a>
1774 <a href="mailto:sabre@nondot.org">Chris Lattner</a><br>
1775 <a href="http://llvm.org">LLVM Compiler Infrastructure</a><br>
1776 Last modified: $Date$