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70 <!-- *********************************************************************** -->
72 <!-- *********************************************************************** -->
76 <p>This document is the central repository for all information pertaining to
78 that the LLVM debug information</a> takes, which is useful for those
79 interested in creating front-ends or dealing directly with the information.
80 Further, this document provides specific examples of what debug information
81 for C/C++ looks like.</p>
83 </div>
85 <!-- ======================================================================= -->
88 </div>
92 <p>The idea of the LLVM debugging information is to capture how the important
93 pieces of the source-language's Abstract Syntax Tree map onto LLVM code.
94 Several design aspects have shaped the solution that appears here. The
95 important ones are:</p>
97 <ul>
98 <li>Debugging information should have very little impact on the rest of the
99 compiler. No transformations, analyses, or code generators should need to
100 be modified because of debugging information.</li>
105 <li>Because LLVM is designed to support arbitrary programming languages,
106 LLVM-to-LLVM tools should not need to know anything about the semantics of
107 the source-level-language.</li>
110 LLVM should not put any restrictions of the flavor of the source-language,
111 and the debugging information should work with any language.</li>
113 <li>With code generator support, it should be possible to use an LLVM compiler
114 to compile a program to native machine code and standard debugging
115 formats. This allows compatibility with traditional machine-code level
116 debuggers, like GDB or DBX.</li>
117 </ul>
119 <p>The approach used by the LLVM implementation is to use a small set
121 mapping between LLVM program objects and the source-level objects. The
122 description of the source-level program is maintained in LLVM metadata
124 (the C/C++ front-end currently uses working draft 7 of
128 <p>When a program is being debugged, a debugger interacts with the user and
129 turns the stored debug information into source-language specific information.
130 As such, a debugger must be aware of the source-language, and is thus tied to
131 a specific language or family of languages.</p>
133 </div>
135 <!-- ======================================================================= -->
138 </div>
142 <p>The role of debug information is to provide meta information normally
143 stripped away during the compilation process. This meta information provides
144 an LLVM user a relationship between generated code and the original program
145 source code.</p>
147 <p>Currently, debug information is consumed by DwarfDebug to produce dwarf
148 information used by the gdb debugger. Other targets could use the same
149 information to produce stabs or other debug forms.</p>
151 <p>It would also be reasonable to use debug information to feed profiling tools
152 for analysis of generated code, or, tools for reconstructing the original
153 source from generated code.</p>
157 </div>
159 <!-- ======================================================================= -->
162 </div>
166 <p>An extremely high priority of LLVM debugging information is to make it
167 interact well with optimizations and analysis. In particular, the LLVM debug
168 information provides the following guarantees:</p>
170 <ul>
172 the source-level state of the program</b>, regardless of which LLVM
173 optimizations have been run, and without any modification to the
174 optimizations themselves. However, some optimizations may impact the
175 ability to modify the current state of the program with a debugger, such
176 as setting program variables, or calling functions that have been
177 deleted.</li>
179 <li>LLVM optimizations gracefully interact with debugging information. If
180 they are not aware of debug information, they are automatically disabled
181 as necessary in the cases that would invalidate the debug info. This
182 retains the LLVM features, making it easy to write new
183 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
187 as they perform aggressive optimizations. This means that, with effort,
188 the LLVM optimizers could optimize debug code just as well as non-debug
189 code.</li>
191 <li>LLVM debug information does not prevent many important optimizations from
192 happening (for example inlining, basic block reordering/merging/cleanup,
193 tail duplication, etc), further reducing the amount of the compiler that
196 <li>LLVM debug information is automatically optimized along with the rest of
197 the program, using existing facilities. For example, duplicate
198 information is automatically merged by the linker, and unused information
199 is automatically removed.</li>
200 </ul>
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
206 and accurate for reading (e.g., you get accurate stack traces despite tail
207 call elimination and inlining), but you might lose the ability to modify the
208 program and call functions where were optimized out of the program, or
209 inlined away completely.</p>
212 framework to test optimizer's handling of debugging information. It can be
213 run like this:</p>
216 <pre>
217 % cd llvm/projects/test-suite/MultiSource/Benchmarks # or some other level
218 % make TEST=dbgopt
219 </pre>
220 </div>
222 <p>This will test impact of debugging information on optimization passes. If
223 debugging information influences optimization passes then it will be reported
225 information on LLVM test infrastructure and how to run various tests.</p>
227 </div>
229 <!-- *********************************************************************** -->
232 </div>
233 <!-- *********************************************************************** -->
237 <p>LLVM debugging information has been carefully designed to make it possible
238 for the optimizer to optimize the program and debugging information without
239 necessarily having to know anything about debugging information. In
240 particular, the use of metadata avoids duplicated debugging information from
241 the beginning, and the global dead code elimination pass automatically
242 deletes debugging information for a function if it decides to delete the
243 function. </p>
245 <p>To do this, most of the debugging information (descriptors for types,
246 variables, functions, source files, etc) is inserted by the language
247 front-end in the form of LLVM metadata. </p>
249 <p>Debug information is designed to be agnostic about the target debugger and
250 debugging information representation (e.g. DWARF/Stabs/etc). It uses a
251 generic pass to decode the information that represents variables, types,
252 functions, namespaces, etc: this allows for arbitrary source-language
253 semantics and type-systems to be used, as long as there is a module
254 written for the target debugger to interpret the information. </p>
256 <p>To provide basic functionality, the LLVM debugger does have to make some
257 assumptions about the source-level language being debugged, though it keeps
258 these to a minimum. The only common features that the LLVM debugger assumes
261 objects are used by a debugger to form stack traces, show information about
262 local variables, etc.</p>
264 <p>This section of the documentation first describes the representation aspects
266 describes the data layout conventions used by the C and C++ front-ends.</p>
268 </div>
270 <!-- ======================================================================= -->
273 </div>
277 <p>In consideration of the complexity and volume of debug information, LLVM
278 provides a specification for well formed debug descriptors. </p>
280 <p>Consumers of LLVM debug information expect the descriptors for program
281 objects to start in a canonical format, but the descriptors can include
282 additional information appended at the end that is source-language
283 specific. All LLVM debugging information is versioned, allowing backwards
284 compatibility in the case that the core structures need to change in some
285 way. Also, all debugging information objects start with a tag to indicate
286 what type of object it is. The source-language is allowed to define its own
287 objects, by using unreserved tag numbers. We recommend using with tags in
291 <p>The fields of debug descriptors used internally by LLVM
296 <pre>
297 !1 = metadata !{
298 i32, ;; A tag
299 ...
300 }
301 </pre>
302 </div>
306 descriptor. The remaining fields are specific to the descriptor. The values
307 of tags are loosely bound to the tag values of DWARF information entries.
308 However, that does not restrict the use of the information supplied to DWARF
309 targets. To facilitate versioning of debug information, the tag is augmented
315 </div>
317 <!-- ======================================================================= -->
320 </div>
325 <pre>
326 !0 = metadata !{
328 ;; (DW_TAG_compile_unit)
329 i32, ;; Unused field.
330 i32, ;; DWARF language identifier (ex. DW_LANG_C89)
331 metadata, ;; Source file name
332 metadata, ;; Source file directory (includes trailing slash)
333 metadata ;; Producer (ex. "4.0.1 LLVM (LLVM research group)")
334 i1, ;; True if this is a main compile unit.
335 i1, ;; True if this is optimized.
336 metadata, ;; Flags
337 i32 ;; Runtime version
338 }
339 </pre>
340 </div>
342 <p>These descriptors contain a source language ID for the file (we use the DWARF
345 working directory of the compiler, and an identifier string for the compiler
346 that produced it.</p>
348 <p>Compile unit descriptors provide the root context for objects declared in a
349 specific compilation unit. File descriptors are defined using this context.</p>
351 </div>
353 <!-- ======================================================================= -->
356 </div>
361 <pre>
362 !0 = metadata !{
364 ;; (DW_TAG_file_type)
365 metadata, ;; Source file name
366 metadata, ;; Source file directory (includes trailing slash)
367 metadata ;; Reference to compile unit where defined
368 }
369 </pre>
370 </div>
372 <p>These descriptors contain information for a file. Global variables and top
373 level functions would be defined using this context.k File descriptors also
374 provide context for source line correspondence. </p>
376 <p>Each input file is encoded as a separate file descriptor in LLVM debugging
377 information output. Each file descriptor would be defined using a
378 compile unit. </p>
380 </div>
382 <!-- ======================================================================= -->
385 </div>
390 <pre>
391 !1 = metadata !{
393 ;; (DW_TAG_variable)
394 i32, ;; Unused field.
395 metadata, ;; Reference to context descriptor
396 metadata, ;; Name
397 metadata, ;; Display name (fully qualified C++ name)
398 metadata, ;; MIPS linkage name (for C++)
399 metadata, ;; Reference to file where defined
400 i32, ;; Line number where defined
401 metadata, ;; Reference to type descriptor
402 i1, ;; True if the global is local to compile unit (static)
403 i1, ;; True if the global is defined in the compile unit (not extern)
404 {}* ;; Reference to the global variable
405 }
406 </pre>
407 </div>
409 <p>These descriptors provide debug information about globals variables. The
410 provide details such as name, type and where the variable is defined. All
413 </div>
415 <!-- ======================================================================= -->
418 </div>
423 <pre>
424 !2 = metadata !{
426 ;; (DW_TAG_subprogram)
427 i32, ;; Unused field.
428 metadata, ;; Reference to context descriptor
429 metadata, ;; Name
430 metadata, ;; Display name (fully qualified C++ name)
431 metadata, ;; MIPS linkage name (for C++)
432 metadata, ;; Reference to file where defined
433 i32, ;; Line number where defined
434 metadata, ;; Reference to type descriptor
435 i1, ;; True if the global is local to compile unit (static)
436 i1 ;; True if the global is defined in the compile unit (not extern)
437 i32 ;; Virtuality, e.g. dwarf::DW_VIRTUALITY__virtual
438 i32 ;; Index into a virtual function
439 metadata, ;; indicates which base type contains the vtable pointer for the
440 ;; derived class
441 i1 ;; isArtificial
442 i1 ;; isOptimized
443 Function *;; Pointer to LLVM function
444 metadata ;; Lists function template parameters
445 }
446 </pre>
447 </div>
449 <p>These descriptors provide debug information about functions, methods and
450 subprograms. They provide details such as name, return types and the source
451 location where the subprogram is defined.
452 All subprogram descriptors are collected by a named metadata
454 </p>
456 </div>
458 <!-- ======================================================================= -->
461 </div>
466 <pre>
467 !3 = metadata !{
469 metadata,;; Reference to context descriptor
470 i32, ;; Line number
471 i32, ;; Column number
472 metadata,;; Reference to source file
473 i32 ;; Unique ID to identify blocks from a template function
474 }
475 </pre>
476 </div>
478 <p>These descriptors provide debug information about nested blocks within a
479 subprogram. The line number and column numbers are used to dinstinguish
480 two lexical blocks at same depth. </p>
482 </div>
484 <!-- ======================================================================= -->
487 </div>
492 <pre>
493 !4 = metadata !{
495 ;; (DW_TAG_base_type)
496 metadata, ;; Reference to context (typically a compile unit)
497 metadata, ;; Name (may be "" for anonymous types)
498 metadata, ;; Reference to file where defined (may be NULL)
499 i32, ;; Line number where defined (may be 0)
500 i64, ;; Size in bits
501 i64, ;; Alignment in bits
502 i64, ;; Offset in bits
503 i32, ;; Flags
504 i32 ;; DWARF type encoding
505 }
506 </pre>
507 </div>
509 <p>These descriptors define primitive types used in the code. Example int, bool
510 and float. The context provides the scope of the type, which is usually the
511 top level. Since basic types are not usually user defined the compile unit
512 and line number can be left as NULL and 0. The size, alignment and offset
513 are expressed in bits and can be 64 bit values. The alignment is used to
514 round the offset when embedded in a
516 doubles on 64 bit boundaries.) The offset is the bit offset if embedded in
519 <p>The type encoding provides the details of the type. The values are typically
520 one of the following:</p>
523 <pre>
524 DW_ATE_address = 1
525 DW_ATE_boolean = 2
526 DW_ATE_float = 4
527 DW_ATE_signed = 5
528 DW_ATE_signed_char = 6
529 DW_ATE_unsigned = 7
530 DW_ATE_unsigned_char = 8
531 </pre>
532 </div>
534 </div>
536 <!-- ======================================================================= -->
539 </div>
544 <pre>
545 !5 = metadata !{
546 i32, ;; Tag (see below)
547 metadata, ;; Reference to context
548 metadata, ;; Name (may be "" for anonymous types)
549 metadata, ;; Reference to file where defined (may be NULL)
550 i32, ;; Line number where defined (may be 0)
551 i64, ;; Size in bits
552 i64, ;; Alignment in bits
553 i64, ;; Offset in bits
554 metadata ;; Reference to type derived from
555 }
556 </pre>
557 </div>
559 <p>These descriptors are used to define types derived from other types. The
560 value of the tag varies depending on the meaning. The following are possible
561 tag values:</p>
564 <pre>
565 DW_TAG_formal_parameter = 5
566 DW_TAG_member = 13
567 DW_TAG_pointer_type = 15
568 DW_TAG_reference_type = 16
569 DW_TAG_typedef = 22
570 DW_TAG_const_type = 38
571 DW_TAG_volatile_type = 53
572 DW_TAG_restrict_type = 55
573 </pre>
574 </div>
581 is a formal argument of a subprogram.</p>
591 from the compile unit and line number. The size, alignment and offset are
592 expressed in bits and can be 64 bit values. The alignment is used to round
599 </p>
601 </div>
603 <!-- ======================================================================= -->
606 </div>
611 <pre>
612 !6 = metadata !{
613 i32, ;; Tag (see below)
614 metadata, ;; Reference to context
615 metadata, ;; Name (may be "" for anonymous types)
616 metadata, ;; Reference to file where defined (may be NULL)
617 i32, ;; Line number where defined (may be 0)
618 i64, ;; Size in bits
619 i64, ;; Alignment in bits
620 i64, ;; Offset in bits
621 i32, ;; Flags
622 metadata, ;; Reference to type derived from
623 metadata, ;; Reference to array of member descriptors
624 i32 ;; Runtime languages
625 }
626 </pre>
627 </div>
630 elements. The value of the tag varies depending on the meaning. The following
631 are possible tag values:</p>
634 <pre>
635 DW_TAG_array_type = 1
636 DW_TAG_enumeration_type = 4
637 DW_TAG_structure_type = 19
638 DW_TAG_union_type = 23
639 DW_TAG_vector_type = 259
640 DW_TAG_subroutine_type = 21
641 DW_TAG_inheritance = 28
642 </pre>
643 </div>
649 descriptors</a>, each representing the range of subscripts at that level of
650 indexing.</p>
654 the definition of enumeration value for the set. All enumeration type
662 representing a field member of the structure or union.</p>
665 provide information about base classes, static members and member
668 represents a base class. If the member of is
670 represents a static member. And, if the member is
672 a member function. For static members and member
677 elements is the return type for the subroutine. The remaining elements are
678 the formal arguments to the subroutine.</p>
681 determined from the compile unit and line number. The size, alignment and
682 offset are expressed in bits and can be 64 bit values. The alignment is used
683 to round the offset when embedded in
685 float doubles on 64 bit boundaries.) The offset is the bit offset if embedded
688 </div>
690 <!-- ======================================================================= -->
693 </div>
698 <pre>
699 !42 = metadata !{
701 i64, ;; Low value
702 i64 ;; High value
703 }
704 </pre>
705 </div>
707 <p>These descriptors are used to define ranges of array subscripts for an array
709 the lower bounds typically zero for C/C++. The high value is the upper
711 > high the array bounds are not included in generated debugging information.
712 </p>
714 </div>
716 <!-- ======================================================================= -->
719 </div>
724 <pre>
725 !6 = metadata !{
727 ;; (DW_TAG_enumerator)
728 metadata, ;; Name
729 i64 ;; Value
730 }
731 </pre>
732 </div>
734 <p>These descriptors are used to define members of an
736 associates the name to the value.</p>
738 </div>
740 <!-- ======================================================================= -->
743 </div>
748 <pre>
749 !7 = metadata !{
750 i32, ;; Tag (see below)
751 metadata, ;; Context
752 metadata, ;; Name
753 metadata, ;; Reference to file where defined
754 i32, ;; 24 bit - Line number where defined
756 metadata ;; Type descriptor
757 }
758 </pre>
759 </div>
761 <p>These descriptors are used to define variables local to a sub program. The
762 value of the tag depends on the usage of the variable:</p>
765 <pre>
766 DW_TAG_auto_variable = 256
767 DW_TAG_arg_variable = 257
768 DW_TAG_return_variable = 258
769 </pre>
770 </div>
772 <p>An auto variable is any variable declared in the body of the function. An
773 argument variable is any variable that appears as a formal argument to the
774 function. A return variable is used to track the result of a function and
775 has no source correspondent.</p>
777 <p>The context is either the subprogram or block where the variable is defined.
778 Name the source variable name. Compile unit and line indicate where the
779 variable was defined. Type descriptor defines the declared type of the
780 variable.</p>
782 </div>
784 <!-- ======================================================================= -->
787 </div>
792 provide debug information at various points in generated code.</p>
794 </div>
796 <!-- ======================================================================= -->
799 </div>
802 <pre>
804 </pre>
806 <p>This intrinsic provides information about a local element (ex. variable.) The
807 first argument is metadata holding alloca for the variable. The
808 second argument is metadata containing description of the variable. </p>
809 </div>
811 <!-- ======================================================================= -->
814 </div>
817 <pre>
819 </pre>
821 <p>This intrinsic provides information when a user source variable is set to a
822 new value. The first argument is the new value (wrapped as metadata). The
823 second argument is the offset in the user source variable where the new value
824 is written. The third argument is metadata containing description of the
825 user source variable. </p>
826 </div>
828 <!-- ======================================================================= -->
831 </div>
834 <p>In many languages, the local variables in functions can have their lifetimes
835 or scopes limited to a subset of a function. In the C family of languages,
836 for example, variables are only live (readable and writable) within the
837 source block that they are defined in. In functional languages, values are
838 only readable after they have been defined. Though this is a very obvious
839 concept, it is non-trivial to model in LLVM, because it has no notion of
840 scoping in this sense, and does not want to be tied to a language's scoping
841 rules.</p>
843 <p>In order to handle this, the LLVM debug format uses the metadata attached to
844 llvm instructions to encode line number and scoping information. Consider
845 the following C fragment, for example:</p>
848 <pre>
849 1. void foo() {
852 4. {
854 6. Z = X;
855 7. }
856 8. X = Y;
857 9. }
858 </pre>
859 </div>
864 <pre>
865 define void @foo() nounwind ssp {
866 entry:
882 store i32 %add, i32* %Z, !dbg !16
884 store i32 %tmp2, i32* %X, !dbg !17
885 ret void, !dbg !18
886 }
888 declare void @llvm.dbg.declare(metadata, metadata) nounwind readnone
895 i1 false, i1 true}; [DW_TAG_subprogram ]
901 !5 = metadata !{null}
907 metadata !6}; [ DW_TAG_auto_variable ]
911 metadata !6}; [ DW_TAG_auto_variable ]
918 </pre>
919 </div>
921 <p>This example illustrates a few important details about LLVM debugging
923 intrinsic and location information, which are attached to an instruction,
924 are applied together to allow a debugger to analyze the relationship between
925 statements, variable definitions, and the code used to implement the
926 function.</p>
929 <pre>
931 </pre>
932 </div>
934 <p>The first intrinsic
941 <pre>
946 metadata !4, i1 false, i1 true}; [DW_TAG_subprogram ]
947 </pre>
948 </div>
951 fields: line number, column number, scope, and original scope. The original
952 scope represents inline location if this instruction is inlined inside a
953 caller, and is null otherwise. In this example, scope is encoded by
957 location information attached to the intrinsics indicates that the
964 <pre>
966 </pre>
967 </div>
969 <p>The second intrinsic
976 <pre>
979 </pre>
980 </div>
986 <p>The scope information attached with each instruction provides a
987 straightforward way to find instructions covered by a scope.</p>
989 </div>
991 <!-- *********************************************************************** -->
994 </div>
995 <!-- *********************************************************************** -->
999 <p>The C and C++ front-ends represent information about the program in a format
1000 that is effectively identical
1002 terms of information content. This allows code generators to trivially
1003 support native debuggers by generating standard dwarf information, and
1004 contains enough information for non-dwarf targets to translate it as
1005 needed.</p>
1007 <p>This section describes the forms used to represent C and C++ programs. Other
1008 languages could pattern themselves after this (which itself is tuned to
1009 representing programs in the same way that DWARF 3 does), or they could
1010 choose to provide completely different forms if they don't fit into the DWARF
1011 model. As support for debugging information gets added to the various LLVM
1012 source-language front-ends, the information used should be documented
1013 here.</p>
1015 <p>The following sections provide examples of various C/C++ constructs and the
1016 debug information that would best describe those constructs.</p>
1018 </div>
1020 <!-- ======================================================================= -->
1023 </div>
1031 <pre>
1032 #include "MyHeader.h"
1034 int main(int argc, char *argv[]) {
1035 return 0;
1036 }
1037 </pre>
1038 </div>
1043 <pre>
1044 ...
1045 ;;
1046 ;; Define the compile unit for the main source file "/Users/mine/sources/MySource.cpp".
1047 ;;
1048 !2 = metadata !{
1049 i32 524305, ;; Tag
1050 i32 0, ;; Unused
1051 i32 4, ;; Language Id
1052 metadata !"MySource.cpp",
1053 metadata !"/Users/mine/sources",
1054 metadata !"4.2.1 (Based on Apple Inc. build 5649) (LLVM build 00)",
1055 i1 true, ;; Main Compile Unit
1056 i1 false, ;; Optimized compile unit
1057 metadata !"", ;; Compiler flags
1058 i32 0} ;; Runtime version
1060 ;;
1061 ;; Define the file for the file "/Users/mine/sources/MySource.cpp".
1062 ;;
1063 !1 = metadata !{
1064 i32 524329, ;; Tag
1065 metadata !"MySource.cpp",
1066 metadata !"/Users/mine/sources",
1067 metadata !2 ;; Compile unit
1068 }
1070 ;;
1071 ;; Define the file for the file "/Users/mine/sources/Myheader.h"
1072 ;;
1073 !3 = metadata !{
1074 i32 524329, ;; Tag
1075 metadata !"Myheader.h"
1076 metadata !"/Users/mine/sources",
1077 metadata !2 ;; Compile unit
1078 }
1080 ...
1081 </pre>
1082 </div>
1084 <p>llvm::Instruction provides easy access to metadata attached with an
1085 instruction. One can extract line number information encoded in LLVM IR
1088 <pre>
1090 DILocation Loc(N); // DILocation is in DebugInfo.h
1091 unsigned Line = Loc.getLineNumber();
1092 StringRef File = Loc.getFilename();
1093 StringRef Dir = Loc.getDirectory();
1094 }
1095 </pre>
1096 </div>
1098 <!-- ======================================================================= -->
1101 </div>
1108 <pre>
1109 int MyGlobal = 100;
1110 </pre>
1111 </div>
1116 <pre>
1117 ;;
1118 ;; Define the global itself.
1119 ;;
1120 %MyGlobal = global int 100
1121 ...
1122 ;;
1123 ;; List of debug info of globals
1124 ;;
1125 !llvm.dbg.gv = !{!0}
1127 ;;
1128 ;; Define the global variable descriptor. Note the reference to the global
1129 ;; variable anchor and the global variable itself.
1130 ;;
1131 !0 = metadata !{
1132 i32 524340, ;; Tag
1133 i32 0, ;; Unused
1134 metadata !1, ;; Context
1135 metadata !"MyGlobal", ;; Name
1136 metadata !"MyGlobal", ;; Display Name
1137 metadata !"MyGlobal", ;; Linkage Name
1138 metadata !3, ;; Compile Unit
1139 i32 1, ;; Line Number
1140 metadata !4, ;; Type
1141 i1 false, ;; Is a local variable
1142 i1 true, ;; Is this a definition
1143 i32* @MyGlobal ;; The global variable
1144 }
1146 ;;
1147 ;; Define the basic type of 32 bit signed integer. Note that since int is an
1148 ;; intrinsic type the source file is NULL and line 0.
1149 ;;
1150 !4 = metadata !{
1151 i32 524324, ;; Tag
1152 metadata !1, ;; Context
1153 metadata !"int", ;; Name
1154 metadata !1, ;; File
1155 i32 0, ;; Line number
1156 i64 32, ;; Size in Bits
1157 i64 32, ;; Align in Bits
1158 i64 0, ;; Offset in Bits
1159 i32 0, ;; Flags
1160 i32 5 ;; Encoding
1161 }
1163 </pre>
1164 </div>
1166 </div>
1168 <!-- ======================================================================= -->
1171 </div>
1178 <pre>
1179 int main(int argc, char *argv[]) {
1180 return 0;
1181 }
1182 </pre>
1183 </div>
1188 <pre>
1189 ;;
1190 ;; Define the anchor for subprograms. Note that the second field of the
1191 ;; anchor is 46, which is the same as the tag for subprograms
1192 ;; (46 = DW_TAG_subprogram.)
1193 ;;
1194 !6 = metadata !{
1195 i32 524334, ;; Tag
1196 i32 0, ;; Unused
1197 metadata !1, ;; Context
1198 metadata !"main", ;; Name
1199 metadata !"main", ;; Display name
1200 metadata !"main", ;; Linkage name
1201 metadata !1, ;; File
1202 i32 1, ;; Line number
1203 metadata !4, ;; Type
1204 i1 false, ;; Is local
1205 i1 true, ;; Is definition
1206 i32 0, ;; Virtuality attribute, e.g. pure virtual function
1207 i32 0, ;; Index into virtual table for C++ methods
1208 i32 0, ;; Type that holds virtual table.
1209 i32 0, ;; Flags
1210 i1 false, ;; True if this function is optimized
1211 Function *, ;; Pointer to llvm::Function
1212 null ;; Function template parameters
1213 }
1214 ;;
1215 ;; Define the subprogram itself.
1216 ;;
1217 define i32 @main(i32 %argc, i8** %argv) {
1218 ...
1219 }
1220 </pre>
1221 </div>
1223 </div>
1225 <!-- ======================================================================= -->
1228 </div>
1234 </div>
1236 <!-- ======================================================================= -->
1239 </div>
1244 <pre>
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1258 </div>
1260 </div>
1262 <!-- ======================================================================= -->
1265 </div>
1270 <pre>
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1284 </div>
1286 </div>
1288 <!-- ======================================================================= -->
1291 </div>
1296 <pre>
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1310 </div>
1312 </div>
1314 <!-- ======================================================================= -->
1317 </div>
1322 <pre>
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1336 </div>
1338 </div>
1340 <!-- ======================================================================= -->
1343 </div>
1348 <pre>
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1362 </div>
1364 </div>
1366 <!-- ======================================================================= -->
1369 </div>
1374 <pre>
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1389 </div>
1391 <!-- ======================================================================= -->
1394 </div>
1399 <pre>
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1413 </div>
1415 </div>
1417 <!-- ======================================================================= -->
1420 </div>
1425 <pre>
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1439 </div>
1441 </div>
1443 <!-- ======================================================================= -->
1446 </div>
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1465 </div>
1467 </div>
1469 <!-- ======================================================================= -->
1472 </div>
1477 <pre>
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1491 </div>
1493 </div>
1495 <!-- ======================================================================= -->
1498 </div>
1503 <pre>
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1517 </div>
1519 </div>
1521 <!-- ======================================================================= -->
1524 </div>
1531 <pre>
1532 typedef const int *IntPtr;
1533 </pre>
1534 </div>
1539 <pre>
1540 ;;
1541 ;; Define the typedef "IntPtr".
1542 ;;
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1557 ;; Define the pointer type.
1558 ;;
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1573 ;;
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1588 ;;
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1601 </pre>
1602 </div>
1604 </div>
1606 <!-- ======================================================================= -->
1609 </div>
1616 <pre>
1617 struct Color {
1618 unsigned Red;
1619 unsigned Green;
1620 unsigned Blue;
1621 };
1622 </pre>
1623 </div>
1628 <pre>
1629 ;;
1630 ;; Define basic type for unsigned int.
1631 ;;
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1644 ;;
1645 ;; Define composite type for struct Color.
1646 ;;
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1662 ;;
1663 ;; Define the Red field.
1664 ;;
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1678 ;;
1679 ;; Define the Green field.
1680 ;;
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1694 ;;
1695 ;; Define the Blue field.
1696 ;;
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1710 ;;
1711 ;; Define the array of fields used by the composite type Color.
1712 ;;
1714 </pre>
1715 </div>
1717 </div>
1719 <!-- ======================================================================= -->
1722 </div>
1729 <pre>
1730 enum Trees {
1731 Spruce = 100,
1732 Oak = 200,
1733 Maple = 300
1734 };
1735 </pre>
1736 </div>
1741 <pre>
1742 ;;
1743 ;; Define composite type for enum Trees
1744 ;;
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1760 ;;
1761 ;; Define the array of enumerators used by composite type Trees.
1762 ;;
1765 ;;
1766 ;; Define Spruce enumerator.
1767 ;;
1770 ;;
1771 ;; Define Oak enumerator.
1772 ;;
1775 ;;
1776 ;; Define Maple enumerator.
1777 ;;
1780 </pre>
1781 </div>
1783 </div>
1785 <!-- *********************************************************************** -->
1787 <hr>
1788 <address>
1796 Last modified: $Date$
1797 </address>
1799 </body>
1800 </html>