-
-
- Anchor descriptors
- Compile unit descriptors
- Global variable descriptors
- Subprogram descriptors @@ -66,7 +66,7 @@ height="369"> @@ -77,10 +77,11 @@ height="369">
- Debugging information should have very little impact on the rest of the -compiler. No transformations, analyses, or code generators should need to be -modified because of debugging information. +
- Debugging information should have very little impact on the rest of the + compiler. No transformations, analyses, or code generators should need to + be modified because of debugging information. -
- LLVM optimizations should interact in well-defined and -easily described ways with the debugging information. +
- LLVM optimizations should interact in well-defined and + easily described ways with the debugging information. -
- Because LLVM is designed to support arbitrary programming languages, -LLVM-to-LLVM tools should not need to know anything about the semantics of the -source-level-language. +
- Because LLVM is designed to support arbitrary programming languages, + LLVM-to-LLVM tools should not need to know anything about the semantics of + the source-level-language. -
- Source-level languages are often widely different from one another. -LLVM should not put any restrictions of the flavor of the source-language, and -the debugging information should work with any language. - -
- With code generator support, it should be possible to use an LLVM compiler -to compile a program to native machine code and standard debugging formats. -This allows compatibility with traditional machine-code level debuggers, like -GDB or DBX. +
- Source-level languages are often widely different from one another. + LLVM should not put any restrictions of the flavor of the source-language, + and the debugging information should work with any language. +
- With code generator support, it should be possible to use an LLVM compiler + to compile a program to native machine code and standard debugging + formats. This allows compatibility with traditional machine-code level + debuggers, like GDB or DBX.
- LLVM debug information always provides information to accurately read the -source-level state of the program, regardless of which LLVM optimizations -have been run, and without any modification to the optimizations themselves. -However, some optimizations may impact the ability to modify the current state -of the program with a debugger, such as setting program variables, or calling -function that have been deleted. - -
- LLVM optimizations gracefully interact with debugging information. If they -are not aware of debug information, they are automatically disabled as necessary -in the cases that would invalidate the debug info. This retains the LLVM -features making it easy to write new transformations. - -
- As desired, LLVM optimizations can be upgraded to be aware of the LLVM -debugging information, allowing them to update the debugging information as they -perform aggressive optimizations. This means that, with effort, the LLVM -optimizers could optimize debug code just as well as non-debug code. - -
- LLVM debug information does not prevent many important optimizations from -happening (for example inlining, basic block reordering/merging/cleanup, tail -duplication, etc), further reducing the amount of the compiler that eventually -is "aware" of debugging information. - -
- LLVM debug information is automatically optimized along with the rest of the -program, using existing facilities. For example, duplicate information is -automatically merged by the linker, and unused information is automatically -removed. - +
- LLVM debug information always provides information to accurately read + the source-level state of the program, regardless of which LLVM + optimizations have been run, and without any modification to the + optimizations themselves. However, some optimizations may impact the + ability to modify the current state of the program with a debugger, such + as setting program variables, or calling functions that have been + deleted. + +
- LLVM optimizations gracefully interact with debugging information. If + they are not aware of debug information, they are automatically disabled + as necessary in the cases that would invalidate the debug info. This + retains the LLVM features, making it easy to write new + transformations. + +
- As desired, LLVM optimizations can be upgraded to be aware of the LLVM + debugging information, allowing them to update the debugging information + as they perform aggressive optimizations. This means that, with effort, + the LLVM optimizers could optimize debug code just as well as non-debug + code. + +
- LLVM debug information does not prevent many important optimizations from + happening (for example inlining, basic block reordering/merging/cleanup, + tail duplication, etc), further reducing the amount of the compiler that + eventually is "aware" of debugging information. + +
- LLVM debug information is automatically optimized along with the rest of + the program, using existing facilities. For example, duplicate + information is automatically merged by the linker, and unused information + is automatically removed.
This document is the central repository for all information pertaining to -debug information in LLVM. It describes the actual format -that the LLVM debug information takes, which is useful for those interested -in creating front-ends or dealing directly with the information. Further, this -document provides specifc examples of what debug information for C/C++.
+ debug information in LLVM. It describes the actual format + that the LLVM debug information takes, which is useful for those + interested in creating front-ends or dealing directly with the information. + Further, this document provides specific examples of what debug information + for C/C++.The idea of the LLVM debugging information is to capture how the important -pieces of the source-language's Abstract Syntax Tree map onto LLVM code. -Several design aspects have shaped the solution that appears here. The -important ones are:
+ pieces of the source-language's Abstract Syntax Tree map onto LLVM code. + Several design aspects have shaped the solution that appears here. The + important ones are:-
-
The approach used by the LLVM implementation is to use a small set of intrinsic functions to define a mapping -between LLVM program objects and the source-level objects. The description of -the source-level program is maintained in LLVM global variables in an implementation-defined format (the C/C++ front-end -currently uses working draft 7 of the Dwarf 3 standard).
+The approach used by the LLVM implementation is to use a small set + of intrinsic functions to define a + mapping between LLVM program objects and the source-level objects. The + description of the source-level program is maintained in LLVM global + variables in an implementation-defined format + (the C/C++ front-end currently uses working draft 7 of + the DWARF 3 + standard).
When a program is being debugged, a debugger interacts with the user and -turns the stored debug information into source-language specific information. -As such, a debugger must be aware of the source-language, and is thus tied to -a specific language of family of languages.
+ turns the stored debug information into source-language specific information. + As such, a debugger must be aware of the source-language, and is thus tied to + a specific language or family of languages.The role of debug information is to provide meta information normally -stripped away during the compilation process. This meta information provides an -llvm user a relationship between generated code and the original program source -code.
+ stripped away during the compilation process. This meta information provides + an LLVM user a relationship between generated code and the original program + source code.Currently, debug information is consumed by the DwarfWriter to produce dwarf -information used by the gdb debugger. Other targets could use the same -information to produce stabs or other debug forms.
+ information used by the gdb debugger. Other targets could use the same + information to produce stabs or other debug forms.It would also be reasonable to use debug information to feed profiling tools -for analysis of generated code, or, tools for reconstructing the original source -from generated code.
+ for analysis of generated code, or, tools for reconstructing the original + source from generated code.TODO - expound a bit more.
@@ -165,48 +167,65 @@ from generated code.An extremely high priority of LLVM debugging information is to make it -interact well with optimizations and analysis. In particular, the LLVM debug -information provides the following guarantees:
+ interact well with optimizations and analysis. In particular, the LLVM debug + information provides the following guarantees:-
-
-
Basically, the debug information allows you to compile a program with -"-O0 -g" and get full debug information, allowing you to arbitrarily -modify the program as it executes from a debugger. Compiling a program with -"-O3 -g" gives you full debug information that is always available and -accurate for reading (e.g., you get accurate stack traces despite tail call -elimination and inlining), but you might lose the ability to modify the program -and call functions where were optimized out of the program, or inlined away -completely.
+ "-O0 -g" and get full debug information, allowing you to arbitrarily + modify the program as it executes from a debugger. Compiling a program with + "-O3 -g" gives you full debug information that is always available + and accurate for reading (e.g., you get accurate stack traces despite tail + call elimination and inlining), but you might lose the ability to modify the + program and call functions where were optimized out of the program, or + inlined away completely. + +LLVM test suite provides a + framework to test optimizer's handling of debugging information. It can be + run like this:
+ ++% cd llvm/projects/test-suite/MultiSource/Benchmarks # or some other level +% make TEST=dbgopt ++
This will test impact of debugging information on optimization passes. If + debugging information influences optimization passes then it will be reported + as a failure. See TestingGuide for more + information on LLVM test infrastructure and how to run various tests.
LLVM debugging information has been carefully designed to make it possible -for the optimizer to optimize the program and debugging information without -necessarily having to know anything about debugging information. In particular, -the global constant merging pass automatically eliminates duplicated debugging -information (often caused by header files), the global dead code elimination -pass automatically deletes debugging information for a function if it decides to -delete the function, and the linker eliminates debug information when it merges -linkonce functions.
+ for the optimizer to optimize the program and debugging information without + necessarily having to know anything about debugging information. In + particular, the global constant merging pass automatically eliminates + duplicated debugging information (often caused by header files), the global + dead code elimination pass automatically deletes debugging information for a + function if it decides to delete the function, and the linker eliminates + debug information when it merges linkonce functions.To do this, most of the debugging information (descriptors for types, -variables, functions, source files, etc) is inserted by the language front-end -in the form of LLVM global variables. These LLVM global variables are no -different from any other global variables, except that they have a web of LLVM -intrinsic functions that point to them. If the last references to a particular -piece of debugging information are deleted (for example, by the --globaldce pass), the extraneous debug information will automatically -become dead and be removed by the optimizer.
+ variables, functions, source files, etc) is inserted by the language + front-end in the form of LLVM global variables. These LLVM global variables + are no different from any other global variables, except that they have a web + of LLVM intrinsic functions that point to them. If the last references to a + particular piece of debugging information are deleted (for example, by the + -globaldce pass), the extraneous debug information will + automatically become dead and be removed by the optimizer.Debug information is designed to be agnostic about the target debugger and -debugging information representation (e.g. DWARF/Stabs/etc). It uses a generic -machine debug information pass to decode the information that represents -variables, types, functions, namespaces, etc: this allows for arbitrary -source-language semantics and type-systems to be used, as long as there is a -module written for the target debugger to interpret the information. In -addition, debug global variables are declared in the "llvm.metadata" -section. All values declared in this section are stripped away after target -debug information is constructed and before the program object is emitted.
+ debugging information representation (e.g. DWARF/Stabs/etc). It uses a + generic machine debug information pass to decode the information that + represents variables, types, functions, namespaces, etc: this allows for + arbitrary source-language semantics and type-systems to be used, as long as + there is a module written for the target debugger to interpret the + information. In addition, debug global variables are declared in + the "llvm.metadata" section. All values declared in this section + are stripped away after target debug information is constructed and before + the program object is emitted.To provide basic functionality, the LLVM debugger does have to make some -assumptions about the source-level language being debugged, though it keeps -these to a minimum. The only common features that the LLVM debugger assumes -exist are source files, and program objects. These abstract objects are -used by a debugger to form stack traces, show information about local -variables, etc.
+ assumptions about the source-level language being debugged, though it keeps + these to a minimum. The only common features that the LLVM debugger assumes + exist are source files, + and program objects. These abstract + objects are used by a debugger to form stack traces, show information about + local variables, etc.This section of the documentation first describes the representation aspects -common to any source-language. The next section -describes the data layout conventions used by the C and C++ front-ends.
+ common to any source-language. The next section + describes the data layout conventions used by the C and C++ front-ends.In consideration of the complexity and volume of debug information, LLVM -provides a specification for well formed debug global variables. The constant -value of each of these globals is one of a limited set of structures, known as -debug descriptors.
+ provides a specification for well formed debug global variables. The + constant value of each of these globals is one of a limited set of + structures, known as debug descriptors.Consumers of LLVM debug information expect the descriptors for program -objects to start in a canonical format, but the descriptors can include -additional information appended at the end that is source-language specific. All -LLVM debugging information is versioned, allowing backwards compatibility in the -case that the core structures need to change in some way. Also, all debugging -information objects start with a tag to indicate what type of object it is. The -source-language is allowed to define its own objects, by using unreserved tag -numbers. We recommend using with tags in the range 0x1000 thru 0x2000 (there is -a defined enum DW_TAG_user_base = 0x1000.)
- -The fields of debug descriptors used internally by LLVM (MachineDebugInfo) -are restricted to only the simple data types int, uint, -bool, float, double, sbyte* and { }* -. References to arbitrary values are handled using a { }* and a -cast to { }* expression; typically references to other field -descriptors, arrays of descriptors or global variables.
- + objects to start in a canonical format, but the descriptors can include + additional information appended at the end that is source-language + specific. All LLVM debugging information is versioned, allowing backwards + compatibility in the case that the core structures need to change in some + way. Also, all debugging information objects start with a tag to indicate + what type of object it is. The source-language is allowed to define its own + objects, by using unreserved tag numbers. We recommend using with tags in + the range 0x1000 thru 0x2000 (there is a defined enum DW_TAG_user_base = + 0x1000.) + +The fields of debug descriptors used internally by LLVM (MachineModuleInfo) + are restricted to only the simple data types int, uint, + bool, float, double, i8* and + { }*. References to arbitrary values are handled using a + { }* and a cast to { }* expression; typically + references to other field descriptors, arrays of descriptors or global + variables.
+ +
- %llvm.dbg.object.type = type {
- uint, ;; A tag
- ...
- }
+%llvm.dbg.object.type = type {
+ uint, ;; A tag
+ ...
+}
+The details of the various descriptors follow.
@@ -309,70 +335,47 @@ current debug version (LLVMDebugVersion = 4 << 16 or 0x40000 or 262144.)- %llvm.dbg.anchor.type = type { - uint, ;; Tag = 0 + LLVMDebugVersion - uint ;; Tag of descriptors grouped by the anchor - } -- -
One important aspect of the LLVM debug representation is that it allows the -LLVM debugger to efficiently index all of the global objects without having the -scan the program. To do this, all of the global objects use "anchor" -descriptors with designated names. All of the global objects of a particular -type (e.g., compile units) contain a pointer to the anchor. This pointer allows -a debugger to use def-use chains to find all global objects of that type.
- -The following names are recognized as anchors by LLVM:
- -- %llvm.dbg.compile_units = linkonce constant %llvm.dbg.anchor.type { uint 0, uint 17 } ;; DW_TAG_compile_unit - %llvm.dbg.global_variables = linkonce constant %llvm.dbg.anchor.type { uint 0, uint 52 } ;; DW_TAG_variable - %llvm.dbg.subprograms = linkonce constant %llvm.dbg.anchor.type { uint 0, uint 46 } ;; DW_TAG_subprogram +%llvm.dbg.compile_unit.type = type { + i32, ;; Tag = 17 + LLVMDebugVersion (DW_TAG_compile_unit) + { }*, ;; Compile unit anchor = cast = (%llvm.dbg.anchor.type* %llvm.dbg.compile_units to { }*) + i32, ;; DWARF language identifier (ex. DW_LANG_C89) + i8*, ;; Source file name + i8*, ;; Source file directory (includes trailing slash) + i8* ;; Producer (ex. "4.0.1 LLVM (LLVM research group)") + i1, ;; True if this is a main compile unit. + i1, ;; True if this is optimized. + i8*, ;; Flags + i32 ;; Runtime version +}- -
Using anchors in this way (where the compile unit descriptor points to the -anchors, as opposed to having a list of compile unit descriptors) allows for the -standard dead global elimination and merging passes to automatically remove -unused debugging information. If the globals were kept track of through lists, -there would always be an object pointing to the descriptors, thus would never be -deleted.
-These descriptors contain a source language ID for the file (we use the DWARF + 3.0 ID numbers, such as DW_LANG_C89, DW_LANG_C_plus_plus, + DW_LANG_Cobol74, etc), three strings describing the filename, + working directory of the compiler, and an identifier string for the compiler + that produced it.
-Compile unit descriptors provide the root context for objects declared in a + specific source file. Global variables and top level functions would be + defined using this context. Compile unit descriptors also provide context + for source line correspondence.
-- %llvm.dbg.compile_unit.type = type { - uint, ;; Tag = 17 + LLVMDebugVersion (DW_TAG_compile_unit) - { }*, ;; Compile unit anchor = cast = (%llvm.dbg.anchor.type* %llvm.dbg.compile_units to { }*) - uint, ;; Dwarf language identifier (ex. DW_LANG_C89) - sbyte*, ;; Source file name - sbyte*, ;; Source file directory (includes trailing slash) - sbyte* ;; Producer (ex. "4.0.1 LLVM (LLVM research group)") - } -- -
These descriptors contain a source language ID for the file (we use the Dwarf -3.0 ID numbers, such as DW_LANG_C89, DW_LANG_C_plus_plus, -DW_LANG_Cobol74, etc), three strings describing the filename, working -directory of the compiler, and an identifier string for the compiler that -produced it.
- -Compile unit descriptors provide the root context for objects declared in a -specific source file. Global variables and top level functions would be defined -using this context. Compile unit descriptors also provide context for source -line correspondence.
+Each input file is encoded as a separate compile unit in LLVM debugging + information output. However, many target specific tool chains prefer to + encode only one compile unit in an object file. In this situation, the LLVM + code generator will include debugging information entities in the compile + unit that is marked as main compile unit. The code generator accepts maximum + one main compile unit per module. If a module does not contain any main + compile unit then the code generator will emit multiple compile units in the + output object file.
- %llvm.dbg.global_variable.type = type { - uint, ;; Tag = 52 + LLVMDebugVersion (DW_TAG_variable) - { }*, ;; Global variable anchor = cast (%llvm.dbg.anchor.type* %llvm.dbg.global_variables to { }*), - { }*, ;; Reference to context descriptor - sbyte*, ;; Name - { }*, ;; Reference to compile unit where defined - uint, ;; Line number where defined - { }*, ;; Reference to type descriptor - bool, ;; True if the global is local to compile unit (static) - bool, ;; True if the global is defined in the compile unit (not extern) - { }* ;; Reference to the global variable - } +%llvm.dbg.global_variable.type = type { + i32, ;; Tag = 52 + LLVMDebugVersion (DW_TAG_variable) + { }*, ;; Global variable anchor = cast (%llvm.dbg.anchor.type* %llvm.dbg.global_variables to { }*), + { }*, ;; Reference to context descriptor + i8*, ;; Name + i8*, ;; Display name (fully qualified C++ name) + i8*, ;; MIPS linkage name (for C++) + { }*, ;; Reference to compile unit where defined + i32, ;; Line number where defined + { }*, ;; Reference to type descriptor + i1, ;; True if the global is local to compile unit (static) + i1, ;; True if the global is defined in the compile unit (not extern) + { }* ;; Reference to the global variable +}+
These descriptors provide debug information about globals variables. The provide details such as name, type and where the variable is defined.
@@ -410,25 +417,30 @@ provide details such as name, type and where the variable is defined.- %llvm.dbg.subprogram.type = type { - uint, ;; Tag = 46 + LLVMDebugVersion (DW_TAG_subprogram) - { }*, ;; Subprogram anchor = cast (%llvm.dbg.anchor.type* %llvm.dbg.subprograms to { }*), - { }*, ;; Reference to context descriptor - sbyte*, ;; Name - { }*, ;; Reference to compile unit where defined - uint, ;; Line number where defined - { }*, ;; Reference to type descriptor - bool, ;; True if the global is local to compile unit (static) - bool ;; True if the global is defined in the compile unit (not extern) - } +%llvm.dbg.subprogram.type = type { + i32, ;; Tag = 46 + LLVMDebugVersion (DW_TAG_subprogram) + { }*, ;; Subprogram anchor = cast (%llvm.dbg.anchor.type* %llvm.dbg.subprograms to { }*), + { }*, ;; Reference to context descriptor + i8*, ;; Name + i8*, ;; Display name (fully qualified C++ name) + i8*, ;; MIPS linkage name (for C++) + { }*, ;; Reference to compile unit where defined + i32, ;; Line number where defined + { }*, ;; Reference to type descriptor + i1, ;; True if the global is local to compile unit (static) + i1 ;; True if the global is defined in the compile unit (not extern) +}+
These descriptors provide debug information about functions, methods and -subprograms. They provide details such as name, return types and the source -location where the subprogram is defined.
+ subprograms. They provide details such as name, return types and the source + location where the subprogram is defined.- %llvm.dbg.block = type { - uint, ;; Tag = 13 + LLVMDebugVersion (DW_TAG_lexical_block) - { }* ;; Reference to context descriptor - } +%llvm.dbg.block = type { + i32, ;; Tag = 13 + LLVMDebugVersion (DW_TAG_lexical_block) + { }* ;; Reference to context descriptor +}+
These descriptors provide debug information about nested blocks within a -subprogram. The array of member descriptors is used to define local variables -and deeper nested blocks.
+ subprogram. The array of member descriptors is used to define local + variables and deeper nested blocks.- %llvm.dbg.basictype.type = type { - uint, ;; Tag = 36 + LLVMDebugVersion (DW_TAG_base_type) - { }*, ;; Reference to context (typically a compile unit) - sbyte*, ;; Name (may be "" for anonymous types) - { }*, ;; Reference to compile unit where defined (may be NULL) - uint, ;; Line number where defined (may be 0) - uint, ;; Size in bits - uint, ;; Alignment in bits - uint, ;; Offset in bits - uint ;; Dwarf type encoding - } +%llvm.dbg.basictype.type = type { + i32, ;; Tag = 36 + LLVMDebugVersion (DW_TAG_base_type) + { }*, ;; Reference to context (typically a compile unit) + i8*, ;; Name (may be "" for anonymous types) + { }*, ;; Reference to compile unit where defined (may be NULL) + i32, ;; Line number where defined (may be 0) + i64, ;; Size in bits + i64, ;; Alignment in bits + i64, ;; Offset in bits + i32, ;; Flags + i32 ;; DWARF type encoding +}+
These descriptors define primitive types used in the code. Example int, bool -and float. The context provides the scope of the type, which is usually the top -level. Since basic types are not usually user defined the compile unit and line -number can be left as NULL and 0. The size, alignment and offset are expressed -in bits and can be 64 bit values. The alignment is used to round the offset -when embedded in a composite type -(example to keep float doubles on 64 bit boundaries.) The offset is the bit -offset if embedded in a composite -type.
+ and float. The context provides the scope of the type, which is usually the + top level. Since basic types are not usually user defined the compile unit + and line number can be left as NULL and 0. The size, alignment and offset + are expressed in bits and can be 64 bit values. The alignment is used to + round the offset when embedded in a + composite type (example to keep float + doubles on 64 bit boundaries.) The offset is the bit offset if embedded in + a composite type.The type encoding provides the details of the type. The values are typically -one of the following;
+ one of the following: +- DW_ATE_address = 1 - DW_ATE_boolean = 2 - DW_ATE_float = 4 - DW_ATE_signed = 5 - DW_ATE_signed_char = 6 - DW_ATE_unsigned = 7 - DW_ATE_unsigned_char = 8 +DW_ATE_address = 1 +DW_ATE_boolean = 2 +DW_ATE_float = 4 +DW_ATE_signed = 5 +DW_ATE_signed_char = 6 +DW_ATE_unsigned = 7 +DW_ATE_unsigned_char = 8+
- %llvm.dbg.derivedtype.type = type { - uint, ;; Tag (see below) - { }*, ;; Reference to context - sbyte*, ;; Name (may be "" for anonymous types) - { }*, ;; Reference to compile unit where defined (may be NULL) - uint, ;; Line number where defined (may be 0) - uint, ;; Size in bits - uint, ;; Alignment in bits - uint, ;; Offset in bits - { }* ;; Reference to type derived from - } +%llvm.dbg.derivedtype.type = type { + i32, ;; Tag (see below) + { }*, ;; Reference to context + i8*, ;; Name (may be "" for anonymous types) + { }*, ;; Reference to compile unit where defined (may be NULL) + i32, ;; Line number where defined (may be 0) + i32, ;; Size in bits + i32, ;; Alignment in bits + i32, ;; Offset in bits + { }* ;; Reference to type derived from +}+
These descriptors are used to define types derived from other types. The value of the tag varies depending on the meaning. The following are possible -tag values;
+tag values: +- DW_TAG_formal_parameter = 5 - DW_TAG_member = 13 - DW_TAG_pointer_type = 15 - DW_TAG_reference_type = 16 - DW_TAG_typedef = 22 - DW_TAG_const_type = 38 - DW_TAG_volatile_type = 53 - DW_TAG_restrict_type = 55 +DW_TAG_formal_parameter = 5 +DW_TAG_member = 13 +DW_TAG_pointer_type = 15 +DW_TAG_reference_type = 16 +DW_TAG_typedef = 22 +DW_TAG_const_type = 38 +DW_TAG_volatile_type = 53 +DW_TAG_restrict_type = 55+
DW_TAG_member is used to define a member of a composite type or subprogram. The type of the member is the derived type. DW_TAG_formal_parameter -is used to define a member which is a formal argument of a subprogram.
+DW_TAG_member is used to define a member of + a composite type + or subprogram. The type of the member is + the derived + type. DW_TAG_formal_parameter is used to define a member which + is a formal argument of a subprogram.
-DW_TAG_typedef is used to -provide a name for the derived type.
+DW_TAG_typedef is used to provide a name for the derived type.
-DW_TAG_pointer_type, -DW_TAG_reference_type, DW_TAG_const_type, -DW_TAG_volatile_type and DW_TAG_restrict_type are used to -qualify the derived type.
+DW_TAG_pointer_type,DW_TAG_reference_type, + DW_TAG_const_type, DW_TAG_volatile_type + and DW_TAG_restrict_type are used to qualify + the derived type.
Derived type location can be determined -from the compile unit and line number. The size, alignment and offset are -expressed in bits and can be 64 bit values. The alignment is used to round the -offset when embedded in a composite type -(example to keep float doubles on 64 bit boundaries.) The offset is the bit -offset if embedded in a composite -type.
+ from the compile unit and line number. The size, alignment and offset are + expressed in bits and can be 64 bit values. The alignment is used to round + the offset when embedded in a composite + type (example to keep float doubles on 64 bit boundaries.) The offset is + the bit offset if embedded in a composite + type.Note that the void * type is expressed as a -llvm.dbg.derivedtype.type with tag of DW_TAG_pointer_type and -NULL derived type.
+ llvm.dbg.derivedtype.type with tag of DW_TAG_pointer_type + and NULL derived type.- %llvm.dbg.compositetype.type = type { - uint, ;; Tag (see below) - { }*, ;; Reference to context - sbyte*, ;; Name (may be "" for anonymous types) - { }*, ;; Reference to compile unit where defined (may be NULL) - uint, ;; Line number where defined (may be 0) - uint, ;; Size in bits - uint, ;; Alignment in bits - uint, ;; Offset in bits - { }* ;; Reference to array of member descriptors - } +%llvm.dbg.compositetype.type = type { + i32, ;; Tag (see below) + { }*, ;; Reference to context + i8*, ;; Name (may be "" for anonymous types) + { }*, ;; Reference to compile unit where defined (may be NULL) + i32, ;; Line number where defined (may be 0) + i64, ;; Size in bits + i64, ;; Alignment in bits + i64, ;; Offset in bits + i32, ;; Flags + { }*, ;; Reference to type derived from + { }*, ;; Reference to array of member descriptors + i32 ;; Runtime languages +}+
These descriptors are used to define types that are composed of 0 or more elements. The value of the tag varies depending on the meaning. The following -are possible tag values;
+are possible tag values: +- DW_TAG_array_type = 1 - DW_TAG_enumeration_type = 4 - DW_TAG_structure_type = 19 - DW_TAG_union_type = 23 - DW_TAG_vector_type = 259 - DW_TAG_subroutine_type = 46 - DW_TAG_inheritance = 26 +DW_TAG_array_type = 1 +DW_TAG_enumeration_type = 4 +DW_TAG_structure_type = 19 +DW_TAG_union_type = 23 +DW_TAG_vector_type = 259 +DW_TAG_subroutine_type = 21 +DW_TAG_inheritance = 28+
The vector flag indicates that an array type is a native packed vector.
The members of array types (tag = DW_TAG_array_type) or vector types -(tag = DW_TAG_vector_type) are subrange -descriptors, each representing the range of subscripts at that level of -indexing.
+ (tag = DW_TAG_vector_type) are subrange + descriptors, each representing the range of subscripts at that level of + indexing.The members of enumeration types (tag = DW_TAG_enumeration_type) are -enumerator descriptors, each representing the -definition of enumeration value -for the set.
+ enumerator descriptors, each representing + the definition of enumeration value for the set.The members of structure (tag = DW_TAG_structure_type) or union (tag -= DW_TAG_union_type) types are any one of the basic, derived -or composite type descriptors, each -representing a field member of the structure or union.
+ = DW_TAG_union_type) types are any one of + the basic, + derived + or composite type descriptors, each + representing a field member of the structure or union.For C++ classes (tag = DW_TAG_structure_type), member descriptors -provide information about base classes, static members and member functions. If -a member is a derived type descriptor and has -a tag of DW_TAG_inheritance, then the type represents a base class. If -the member of is a global variable -descriptor then it represents a static member. And, if the member is a subprogram descriptor then it represents a member -function. For static members and member functions, getName() returns -the members link or the C++ mangled name. getDisplayName() the -simplied version of the name.
- -The first member of subroutine (tag = DW_TAG_subroutine_type) -type elements is the return type for the subroutine. The remaining -elements are the formal arguments to the subroutine.
+ provide information about base classes, static members and member + functions. If a member is a derived type + descriptor and has a tag of DW_TAG_inheritance, then the type + represents a base class. If the member of is + a global variable descriptor then it + represents a static member. And, if the member is + a subprogram descriptor then it represents + a member function. For static members and member + functions, getName() returns the members link or the C++ mangled + name. getDisplayName() the simplied version of the name. + +The first member of subroutine (tag = DW_TAG_subroutine_type) type + elements is the return type for the subroutine. The remaining elements are + the formal arguments to the subroutine.
Composite type location can be -determined from the compile unit and line number. The size, alignment and -offset are expressed in bits and can be 64 bit values. The alignment is used to -round the offset when embedded in a composite -type (as an example, to keep float doubles on 64 bit boundaries.) The offset -is the bit offset if embedded in a composite -type.
+ determined from the compile unit and line number. The size, alignment and + offset are expressed in bits and can be 64 bit values. The alignment is used + to round the offset when embedded in + a composite type (as an example, to keep + float doubles on 64 bit boundaries.) The offset is the bit offset if embedded + in a composite type.- %llvm.dbg.subrange.type = type { - uint, ;; Tag = 33 + LLVMDebugVersion (DW_TAG_subrange_type) - uint, ;; Low value - uint ;; High value - } +%llvm.dbg.subrange.type = type { + i32, ;; Tag = 33 + LLVMDebugVersion (DW_TAG_subrange_type) + i64, ;; Low value + i64 ;; High value +}+
These descriptors are used to define ranges of array subscripts for an array -composite type. The low value defines the -lower bounds typically zero for C/C++. The high value is the upper bounds. -Values are 64 bit. High - low + 1 is the size of the array. If -low == high the array will be unbounded.
+ composite type. The low value defines + the lower bounds typically zero for C/C++. The high value is the upper + bounds. Values are 64 bit. High - low + 1 is the size of the array. If low + == high the array will be unbounded.- %llvm.dbg.enumerator.type = type { - uint, ;; Tag = 40 + LLVMDebugVersion (DW_TAG_enumerator) - sbyte*, ;; Name - uint ;; Value - } +%llvm.dbg.enumerator.type = type { + i32, ;; Tag = 40 + LLVMDebugVersion (DW_TAG_enumerator) + i8*, ;; Name + i64 ;; Value +}+
These descriptors are used to define members of an enumeration composite type, it associates the name to the -value.
+These descriptors are used to define members of an + enumeration composite type, it + associates the name to the value.
- %llvm.dbg.variable.type = type { - uint, ;; Tag (see below) - { }*, ;; Context - sbyte*, ;; Name - { }*, ;; Reference to compile unit where defined - uint, ;; Line number where defined - { }* ;; Type descriptor - } +%llvm.dbg.variable.type = type { + i32, ;; Tag (see below) + { }*, ;; Context + i8*, ;; Name + { }*, ;; Reference to compile unit where defined + i32, ;; Line number where defined + { }* ;; Type descriptor +}+
These descriptors are used to define variables local to a sub program. The -value of the tag depends on the usage of the variable;
+ value of the tag depends on the usage of the variable: +- DW_TAG_auto_variable = 256 - DW_TAG_arg_variable = 257 - DW_TAG_return_variable = 258 +DW_TAG_auto_variable = 256 +DW_TAG_arg_variable = 257 +DW_TAG_return_variable = 258+
An auto variable is any variable declared in the body of the function. An -argument variable is any variable that appears as a formal argument to the -function. A return variable is used to track the result of a function and has -no source correspondent.
+ argument variable is any variable that appears as a formal argument to the + function. A return variable is used to track the result of a function and + has no source correspondent.The context is either the subprogram or block where the variable is defined. -Name the source variable name. Compile unit and line indicate where the -variable was defined. Type descriptor defines the declared type of the -variable.
+ Name the source variable name. Compile unit and line indicate where the + variable was defined. Type descriptor defines the declared type of the + variable.LLVM uses several intrinsic functions (name prefixed with "llvm.dbg") to -provide debug information at various points in generated code.
+ provide debug information at various points in generated code.This intrinsic is used to provide correspondence between the source file and -the generated code. The first argument is the line number (base 1), second -argument si the column number (0 if unknown) and the third argument the source -%llvm.dbg.compile_unit* cast to a -{ }*. Code following a call to this intrinsic will have been defined -in close proximity of the line, column and file. This information holds until -the next call to %lvm.dbg.stoppoint.
+ the generated code. The first argument is the line number (base 1), second + argument is the column number (0 if unknown) and the third argument the + source %llvm.dbg.compile_unit* + cast to a { }*. Code following a call to this intrinsic will + have been defined in close proximity of the line, column and file. This + information holds until the next call + to %lvm.dbg.stoppoint.This intrinsic is used to link the debug information in %llvm.dbg.subprogram to the function. It also -defines the beginning of the function's declarative region (scope.) The -intrinsic should be called early in the function after the all the alloca -instructions. It should be paired off with a closing %llvm.dbg.region.end. The function's -single argument is the %llvm.dbg.subprogram.type.
+This intrinsic is used to link the debug information + in %llvm.dbg.subprogram to the + function. It defines the beginning of the function's declarative region + (scope). It also implies a call to + %llvm.dbg.stoppoint which + defines a source line "stop point". The intrinsic should be called early in + the function after the all the alloca instructions. It should be paired off + with a closing + %llvm.dbg.region.end. + The function's single argument is + the %llvm.dbg.subprogram.type.
This intrinsic is used to define the beginning of a declarative scope (ex. -block) for local language elements. It should be paired off with a closing -%llvm.dbg.region.end. The -function's single argument is the %llvm.dbg.block which is starting.
+ block) for local language elements. It should be paired off with a closing + %llvm.dbg.region.end. The + function's single argument is + the %llvm.dbg.block which is + starting.This intrinsic is used to define the end of a declarative scope (ex. block) -for local language elements. It should be paired off with an opening %llvm.dbg.region.start or %llvm.dbg.func.start. The function's -single argument is either the %llvm.dbg.block or the %llvm.dbg.subprogram.type which is -ending.
+ for local language elements. It should be paired off with an + opening %llvm.dbg.region.start + or %llvm.dbg.func.start. + The function's single argument is either + the %llvm.dbg.block or + the %llvm.dbg.subprogram.type + which is ending. @@ -824,10 +868,10 @@ ending.This intrinsic provides information about a local element (ex. variable.) The -first argument is the alloca for the variable, cast to a { }*. The -second argument is the %llvm.dbg.variable containing the description -of the variable, also cast to a { }*.
+ first argument is the alloca for the variable, cast to a { }*. The + second argument is + the %llvm.dbg.variable containing + the description of the variable, also cast to a { }*. @@ -841,30 +885,30 @@ of the variable, also cast to a { }*.LLVM debugger "stop points" are a key part of the debugging representation -that allows the LLVM to maintain simple semantics for debugging optimized code. The basic idea is that the -front-end inserts calls to the %llvm.dbg.stoppoint intrinsic -function at every point in the program where a debugger should be able to -inspect the program (these correspond to places a debugger stops when you -"step" through it). The front-end can choose to place these as -fine-grained as it would like (for example, before every subexpression -evaluated), but it is recommended to only put them after every source statement -that includes executable code.
+ that allows the LLVM to maintain simple semantics + for debugging optimized code. The basic idea is that + the front-end inserts calls to + the %llvm.dbg.stoppoint + intrinsic function at every point in the program where a debugger should be + able to inspect the program (these correspond to places a debugger stops when + you "step" through it). The front-end can choose to place these as + fine-grained as it would like (for example, before every subexpression + evaluated), but it is recommended to only put them after every source + statement that includes executable code.Using calls to this intrinsic function to demark legal points for the -debugger to inspect the program automatically disables any optimizations that -could potentially confuse debugging information. To non-debug-information-aware -transformations, these calls simply look like calls to an external function, -which they must assume to do anything (including reading or writing to any part -of reachable memory). On the other hand, it does not impact many optimizations, -such as code motion of non-trapping instructions, nor does it impact -optimization of subexpressions, code duplication transformations, or basic-block -reordering transformations.
+ debugger to inspect the program automatically disables any optimizations that + could potentially confuse debugging information. To + non-debug-information-aware transformations, these calls simply look like + calls to an external function, which they must assume to do anything + (including reading or writing to any part of reachable memory). On the other + hand, it does not impact many optimizations, such as code motion of + non-trapping instructions, nor does it impact optimization of subexpressions, + code duplication transformations, or basic-block reordering + transformations.In many languages, the local variables in functions can have their lifetime -or scope limited to a subset of a function. In the C family of languages, for -example, variables are only live (readable and writable) within the source block -that they are defined in. In functional languages, values are only readable -after they have been defined. Though this is a very obvious concept, it is also -non-trivial to model in LLVM, because it has no notion of scoping in this sense, -and does not want to be tied to a language's scoping rules.
+ or scope limited to a subset of a function. In the C family of languages, + for example, variables are only live (readable and writable) within the + source block that they are defined in. In functional languages, values are + only readable after they have been defined. Though this is a very obvious + concept, it is also non-trivial to model in LLVM, because it has no notion of + scoping in this sense, and does not want to be tied to a language's scoping + rules.In order to handle this, the LLVM debug format uses the notion of "regions" -of a function, delineated by calls to intrinsic functions. These intrinsic -functions define new regions of the program and indicate when the region -lifetime expires. Consider the following C fragment, for example:
+ of a function, delineated by calls to intrinsic functions. These intrinsic + functions define new regions of the program and indicate when the region + lifetime expires. Consider the following C fragment, for example: +
1. void foo() {
2. int X = ...;
@@ -895,9 +941,11 @@ lifetime expires. Consider the following C fragment, for example:
8. ...
9. }
+Compiled to LLVM, this function would be represented like this:
+
void %foo() {
entry:
@@ -907,93 +955,93 @@ entry:
...
- call void %llvm.dbg.func.start( %llvm.dbg.subprogram.type* %llvm.dbg.subprogram )
+ call void @llvm.dbg.func.start( %llvm.dbg.subprogram.type* @llvm.dbg.subprogram )
- call void %llvm.dbg.stoppoint( uint 2, uint 2, %llvm.dbg.compile_unit* %llvm.dbg.compile_unit )
+ call void @llvm.dbg.stoppoint( uint 2, uint 2, %llvm.dbg.compile_unit* @llvm.dbg.compile_unit )
- call void %llvm.dbg.declare({}* %X, ...)
- call void %llvm.dbg.declare({}* %Y, ...)
+ call void @llvm.dbg.declare({}* %X, ...)
+ call void @llvm.dbg.declare({}* %Y, ...)
;; Evaluate expression on line 2, assigning to X.
- call void %llvm.dbg.stoppoint( uint 3, uint 2, %llvm.dbg.compile_unit* %llvm.dbg.compile_unit )
+ call void @llvm.dbg.stoppoint( uint 3, uint 2, %llvm.dbg.compile_unit* @llvm.dbg.compile_unit )
;; Evaluate expression on line 3, assigning to Y.
- call void %llvm.region.start()
- call void %llvm.dbg.stoppoint( uint 5, uint 4, %llvm.dbg.compile_unit* %llvm.dbg.compile_unit )
- call void %llvm.dbg.declare({}* %X, ...)
+ call void @llvm.region.start()
+ call void @llvm.dbg.stoppoint( uint 5, uint 4, %llvm.dbg.compile_unit* @llvm.dbg.compile_unit )
+ call void @llvm.dbg.declare({}* %X, ...)
;; Evaluate expression on line 5, assigning to Z.
- call void %llvm.dbg.stoppoint( uint 7, uint 2, %llvm.dbg.compile_unit* %llvm.dbg.compile_unit )
- call void %llvm.region.end()
+ call void @llvm.dbg.stoppoint( uint 7, uint 2, %llvm.dbg.compile_unit* @llvm.dbg.compile_unit )
+ call void @llvm.region.end()
- call void %llvm.dbg.stoppoint( uint 9, uint 2, %llvm.dbg.compile_unit* %llvm.dbg.compile_unit )
+ call void @llvm.dbg.stoppoint( uint 9, uint 2, %llvm.dbg.compile_unit* @llvm.dbg.compile_unit )
- call void %llvm.region.end()
+ call void @llvm.region.end()
ret void
}
+This example illustrates a few important details about the LLVM debugging -information. In particular, it shows how the various intrinsics are applied -together to allow a debugger to analyze the relationship between statements, -variable definitions, and the code used to implement the function.
- -The first intrinsic %llvm.dbg.func.start provides -a link with the subprogram descriptor -containing the details of this function. This call also defines the beginning -of the function region, bounded by the %llvm.region.end at the end of -the function. This region is used to bracket the lifetime of variables declared -within. For a function, this outer region defines a new stack frame whose -lifetime ends when the region is ended.
+ information. In particular, it shows how the various intrinsics are applied + together to allow a debugger to analyze the relationship between statements, + variable definitions, and the code used to implement the function. + +The first + intrinsic %llvm.dbg.func.start + provides a link with the subprogram + descriptor containing the details of this function. This call also + defines the beginning of the function region, bounded by + the %llvm.region.end at the + end of the function. This region is used to bracket the lifetime of + variables declared within. For a function, this outer region defines a new + stack frame whose lifetime ends when the region is ended.
It is possible to define inner regions for short term variables by using the -%llvm.region.start and %llvm.region.end to bound a -region. The inner region in this example would be for the block containing the -declaration of Z.
+ %llvm.region.start + and %llvm.region.end to + bound a region. The inner region in this example would be for the block + containing the declaration of Z.Using regions to represent the boundaries of source-level functions allow -LLVM interprocedural optimizations to arbitrarily modify LLVM functions without -having to worry about breaking mapping information between the LLVM code and the -and source-level program. In particular, the inliner requires no modification -to support inlining with debugging information: there is no explicit correlation -drawn between LLVM functions and their source-level counterparts (note however, -that if the inliner inlines all instances of a non-strong-linkage function into -its caller that it will not be possible for the user to manually invoke the -inlined function from a debugger).
- -Once the function has been defined, the stopping point corresponding to -line #2 (column #2) of the function is encountered. At this point in the -function, no local variables are live. As lines 2 and 3 of the example -are executed, their variable definitions are introduced into the program using -%llvm.dbg.declare, without the -need to specify a new region. These variables do not require new regions to be -introduced because they go out of scope at the same point in the program: line -9.
+ LLVM interprocedural optimizations to arbitrarily modify LLVM functions + without having to worry about breaking mapping information between the LLVM + code and the and source-level program. In particular, the inliner requires + no modification to support inlining with debugging information: there is no + explicit correlation drawn between LLVM functions and their source-level + counterparts (note however, that if the inliner inlines all instances of a + non-strong-linkage function into its caller that it will not be possible for + the user to manually invoke the inlined function from a debugger). + +Once the function has been defined, + the stopping point + corresponding to line #2 (column #2) of the function is encountered. At this + point in the function, no local variables are live. As lines 2 and 3 + of the example are executed, their variable definitions are introduced into + the program using + %llvm.dbg.declare, without the + need to specify a new region. These variables do not require new regions to + be introduced because they go out of scope at the same point in the program: + line 9.
In contrast, the Z variable goes out of scope at a different time, -on line 7. For this reason, it is defined within the inner region, which kills -the availability of Z before the code for line 8 is executed. In this -way, regions can support arbitrary source-language scoping rules, as long as -they can only be nested (ie, one scope cannot partially overlap with a part of -another scope).
+ on line 7. For this reason, it is defined within the inner region, which + kills the availability of Z before the code for line 8 is executed. + In this way, regions can support arbitrary source-language scoping rules, as + long as they can only be nested (ie, one scope cannot partially overlap with + a part of another scope).It is worth noting that this scoping mechanism is used to control scoping of -all declarations, not just variable declarations. For example, the scope of a -C++ using declaration is controlled with this couldchange how name lookup is -performed.
+ all declarations, not just variable declarations. For example, the scope of + a C++ using declaration is controlled with this and could change how name + lookup is performed.The C and C++ front-ends represent information about the program in a format -that is effectively identical to Dwarf 3.0 in terms of -information content. This allows code generators to trivially support native -debuggers by generating standard dwarf information, and contains enough -information for non-dwarf targets to translate it as needed.
+ that is effectively identical + to DWARF 3.0 in + terms of information content. This allows code generators to trivially + support native debuggers by generating standard dwarf information, and + contains enough information for non-dwarf targets to translate it as + needed.This section describes the forms used to represent C and C++ programs. Other -languages could pattern themselves after this (which itself is tuned to -representing programs in the same way that Dwarf 3 does), or they could choose -to provide completely different forms if they don't fit into the Dwarf model. -As support for debugging information gets added to the various LLVM -source-language front-ends, the information used should be documented here.
+ languages could pattern themselves after this (which itself is tuned to + representing programs in the same way that DWARF 3 does), or they could + choose to provide completely different forms if they don't fit into the DWARF + model. As support for debugging information gets added to the various LLVM + source-language front-ends, the information used should be documented + here.The following sections provide examples of various C/C++ constructs and the -debug information that would best describe those constructs.
+ debug information that would best describe those constructs.Given the source files "MySource.cpp" and "MyHeader.h" located in the -directory "/Users/mine/sources", the following code;
+Given the source files MySource.cpp and MyHeader.h located + in the directory /Users/mine/sources, the following code:
+
#include "MyHeader.h"
@@ -1038,9 +1089,11 @@ int main(int argc, char *argv[]) {
return 0;
}
+a C/C++ front-end would generate the following descriptors;
+a C/C++ front-end would generate the following descriptors:
+
...
;;
@@ -1048,7 +1101,7 @@ int main(int argc, char *argv[]) {
;; for compile units.
;;
%llvm.dbg.anchor.type = type { uint, uint }
-%llvm.dbg.compile_unit.type = type { uint, { }*, uint, uint, sbyte*, sbyte*, sbyte* }
+%llvm.dbg.compile_unit.type = type { uint, { }*, uint, uint, i8*, i8*, i8* }
...
;;
;; Define the anchor for compile units. Note that the second field of the
@@ -1065,9 +1118,9 @@ int main(int argc, char *argv[]) {
{ }* cast (%llvm.dbg.anchor.type* %llvm.dbg.compile_units to { }*),
uint 1,
uint 1,
- sbyte* getelementptr ([13 x sbyte]* %str1, int 0, int 0),
- sbyte* getelementptr ([21 x sbyte]* %str2, int 0, int 0),
- sbyte* getelementptr ([33 x sbyte]* %str3, int 0, int 0) }, section "llvm.metadata"
+ i8* getelementptr ([13 x i8]* %str1, i32 0, i32 0),
+ i8* getelementptr ([21 x i8]* %str2, i32 0, i32 0),
+ i8* getelementptr ([33 x i8]* %str3, i32 0, i32 0) }, section "llvm.metadata"
;;
;; Define the compile unit for the header file "/Users/mine/sources/MyHeader.h".
@@ -1077,19 +1130,20 @@ int main(int argc, char *argv[]) {
{ }* cast (%llvm.dbg.anchor.type* %llvm.dbg.compile_units to { }*),
uint 1,
uint 1,
- sbyte* getelementptr ([11 x sbyte]* %str4, int 0, int 0),
- sbyte* getelementptr ([21 x sbyte]* %str2, int 0, int 0),
- sbyte* getelementptr ([33 x sbyte]* %str3, int 0, int 0) }, section "llvm.metadata"
+ i8* getelementptr ([11 x i8]* %str4, int 0, int 0),
+ i8* getelementptr ([21 x i8]* %str2, int 0, int 0),
+ i8* getelementptr ([33 x i8]* %str3, int 0, int 0) }, section "llvm.metadata"
;;
;; Define each of the strings used in the compile units.
;;
-%str1 = internal constant [13 x sbyte] c"MySource.cpp\00", section "llvm.metadata";
-%str2 = internal constant [21 x sbyte] c"/Users/mine/sources/\00", section "llvm.metadata";
-%str3 = internal constant [33 x sbyte] c"4.0.1 LLVM (LLVM research group)\00", section "llvm.metadata";
-%str4 = internal constant [11 x sbyte] c"MyHeader.h\00", section "llvm.metadata";
+%str1 = internal constant [13 x i8] c"MySource.cpp\00", section "llvm.metadata";
+%str2 = internal constant [21 x i8] c"/Users/mine/sources/\00", section "llvm.metadata";
+%str3 = internal constant [33 x i8] c"4.0.1 LLVM (LLVM research group)\00", section "llvm.metadata";
+%str4 = internal constant [11 x i8] c"MyHeader.h\00", section "llvm.metadata";
...
+Given an integer global variable declared as follows;
+Given an integer global variable declared as follows:
+int MyGlobal = 100;+
a C/C++ front-end would generate the following descriptors;
+a C/C++ front-end would generate the following descriptors:
+;; ;; Define types used. One for global variable anchors, one for the global @@ -1115,8 +1172,8 @@ int MyGlobal = 100; ;; compile unit. ;; %llvm.dbg.anchor.type = type { uint, uint } -%llvm.dbg.global_variable.type = type { uint, { }*, { }*, sbyte*, { }*, uint, { }*, bool, bool, { }*, uint } -%llvm.dbg.basictype.type = type { uint, { }*, sbyte*, { }*, int, uint, uint, uint, uint } +%llvm.dbg.global_variable.type = type { uint, { }*, { }*, i8*, { }*, uint, { }*, bool, bool, { }*, uint } +%llvm.dbg.basictype.type = type { uint, { }*, i8*, { }*, int, uint, uint, uint, uint } %llvm.dbg.compile_unit.type = ... ... ;; @@ -1139,7 +1196,8 @@ int MyGlobal = 100; uint add(uint 52, uint 262144), { }* cast (%llvm.dbg.anchor.type* %llvm.dbg.global_variables to { }*), { }* cast (%llvm.dbg.compile_unit.type* %llvm.dbg.compile_unit to { }*), - sbyte* getelementptr ([9 x sbyte]* %str1, int 0, int 0), + i8* getelementptr ([9 x i8]* %str1, int 0, int 0), + i8* getelementptr ([1 x i8]* %str2, int 0, int 0), { }* cast (%llvm.dbg.compile_unit.type* %llvm.dbg.compile_unit to { }*), uint 1, { }* cast (%llvm.dbg.basictype.type* %llvm.dbg.basictype to { }*), @@ -1154,7 +1212,7 @@ int MyGlobal = 100; %llvm.dbg.basictype = internal constant %llvm.dbg.basictype.type { uint add(uint 36, uint 262144), { }* cast (%llvm.dbg.compile_unit.type* %llvm.dbg.compile_unit to { }*), - sbyte* getelementptr ([4 x sbyte]* %str2, int 0, int 0), + i8* getelementptr ([4 x i8]* %str3, int 0, int 0), { }* null, int 0, uint 32, @@ -1165,9 +1223,11 @@ int MyGlobal = 100; ;; ;; Define the names of the global variable and basic type. ;; -%str1 = internal constant [9 x sbyte] c"MyGlobal\00", section "llvm.metadata" -%str2 = internal constant [4 x sbyte] c"int\00", section "llvm.metadata" +%str1 = internal constant [9 x i8] c"MyGlobal\00", section "llvm.metadata" +%str2 = internal constant [1 x i8] c"\00", section "llvm.metadata" +%str3 = internal constant [4 x i8] c"int\00", section "llvm.metadata"+
Given a function declared as follows;
+Given a function declared as follows:
+
int main(int argc, char *argv[]) {
return 0;
}
+a C/C++ front-end would generate the following descriptors;
+a C/C++ front-end would generate the following descriptors:
+;; ;; Define types used. One for subprogram anchors, one for the subprogram ;; descriptor, one for the global's basic type and one for the subprogram's ;; compile unit. ;; -%llvm.dbg.subprogram.type = type { uint, { }*, { }*, sbyte*, { }*, bool, bool } +%llvm.dbg.subprogram.type = type { uint, { }*, { }*, i8*, { }*, bool, bool } %llvm.dbg.anchor.type = type { uint, uint } %llvm.dbg.compile_unit.type = ... @@ -1212,7 +1275,8 @@ int main(int argc, char *argv[]) { uint add(uint 46, uint 262144), { }* cast (%llvm.dbg.anchor.type* %llvm.dbg.subprograms to { }*), { }* cast (%llvm.dbg.compile_unit.type* %llvm.dbg.compile_unit to { }*), - sbyte* getelementptr ([5 x sbyte]* %str1, int 0, int 0), + i8* getelementptr ([5 x i8]* %str1, int 0, int 0), + i8* getelementptr ([1 x i8]* %str2, int 0, int 0), { }* cast (%llvm.dbg.compile_unit.type* %llvm.dbg.compile_unit to { }*), uint 1, { }* null, @@ -1222,15 +1286,17 @@ int main(int argc, char *argv[]) { ;; ;; Define the name of the subprogram. ;; -%str1 = internal constant [5 x sbyte] c"main\00", section "llvm.metadata" +%str1 = internal constant [5 x i8] c"main\00", section "llvm.metadata" +%str2 = internal constant [1 x i8] c"\00", section "llvm.metadata" ;; ;; Define the subprogram itself. ;; -int %main(int %argc, sbyte** %argv) { +int %main(int %argc, i8** %argv) { ... }+
The following are the basic type descriptors for C/C++ core types;
+The following are the basic type descriptors for C/C++ core types:
%llvm.dbg.basictype = internal constant %llvm.dbg.basictype.type { uint add(uint 36, uint 262144), { }* cast (%llvm.dbg.compile_unit.type* %llvm.dbg.compile_unit to { }*), - sbyte* getelementptr ([5 x sbyte]* %str1, int 0, int 0), + i8* getelementptr ([5 x i8]* %str1, int 0, int 0), { }* null, int 0, uint 32, uint 32, uint 0, uint 2 }, section "llvm.metadata" -%str1 = internal constant [5 x sbyte] c"bool\00", section "llvm.metadata" +%str1 = internal constant [5 x i8] c"bool\00", section "llvm.metadata"+
%llvm.dbg.basictype = internal constant %llvm.dbg.basictype.type { uint add(uint 36, uint 262144), { }* cast (%llvm.dbg.compile_unit.type* %llvm.dbg.compile_unit to { }*), - sbyte* getelementptr ([5 x sbyte]* %str1, int 0, int 0), + i8* getelementptr ([5 x i8]* %str1, int 0, int 0), { }* null, int 0, uint 8, uint 8, uint 0, uint 6 }, section "llvm.metadata" -%str1 = internal constant [5 x sbyte] c"char\00", section "llvm.metadata" +%str1 = internal constant [5 x i8] c"char\00", section "llvm.metadata"+
%llvm.dbg.basictype = internal constant %llvm.dbg.basictype.type { uint add(uint 36, uint 262144), { }* cast (%llvm.dbg.compile_unit.type* %llvm.dbg.compile_unit to { }*), - sbyte* getelementptr ([14 x sbyte]* %str1, int 0, int 0), + i8* getelementptr ([14 x i8]* %str1, int 0, int 0), { }* null, int 0, uint 8, uint 8, uint 0, uint 8 }, section "llvm.metadata" -%str1 = internal constant [14 x sbyte] c"unsigned char\00", section "llvm.metadata" +%str1 = internal constant [14 x i8] c"unsigned char\00", section "llvm.metadata"+
%llvm.dbg.basictype = internal constant %llvm.dbg.basictype.type { uint add(uint 36, uint 262144), { }* cast (%llvm.dbg.compile_unit.type* %llvm.dbg.compile_unit to { }*), - sbyte* getelementptr ([10 x sbyte]* %str1, int 0, int 0), + i8* getelementptr ([10 x i8]* %str1, int 0, int 0), { }* null, int 0, uint 16, uint 16, uint 0, uint 5 }, section "llvm.metadata" -%str1 = internal constant [10 x sbyte] c"short int\00", section "llvm.metadata" +%str1 = internal constant [10 x i8] c"short int\00", section "llvm.metadata"+
%llvm.dbg.basictype = internal constant %llvm.dbg.basictype.type { uint add(uint 36, uint 262144), { }* cast (%llvm.dbg.compile_unit.type* %llvm.dbg.compile_unit to { }*), - sbyte* getelementptr ([19 x sbyte]* %str1, int 0, int 0), + i8* getelementptr ([19 x i8]* %str1, int 0, int 0), { }* null, int 0, uint 16, uint 16, uint 0, uint 7 }, section "llvm.metadata" -%str1 = internal constant [19 x sbyte] c"short unsigned int\00", section "llvm.metadata" +%str1 = internal constant [19 x i8] c"short unsigned int\00", section "llvm.metadata"+
%llvm.dbg.basictype = internal constant %llvm.dbg.basictype.type { uint add(uint 36, uint 262144), { }* cast (%llvm.dbg.compile_unit.type* %llvm.dbg.compile_unit to { }*), - sbyte* getelementptr ([4 x sbyte]* %str1, int 0, int 0), + i8* getelementptr ([4 x i8]* %str1, int 0, int 0), { }* null, int 0, uint 32, uint 32, uint 0, uint 5 }, section "llvm.metadata" -%str1 = internal constant [4 x sbyte] c"int\00", section "llvm.metadata" -+%str1 = internal constant [4 x i8] c"int\00", section "llvm.metadata" +
%llvm.dbg.basictype = internal constant %llvm.dbg.basictype.type { uint add(uint 36, uint 262144), { }* cast (%llvm.dbg.compile_unit.type* %llvm.dbg.compile_unit to { }*), - sbyte* getelementptr ([13 x sbyte]* %str1, int 0, int 0), + i8* getelementptr ([13 x i8]* %str1, int 0, int 0), { }* null, int 0, uint 32, uint 32, uint 0, uint 7 }, section "llvm.metadata" -%str1 = internal constant [13 x sbyte] c"unsigned int\00", section "llvm.metadata" +%str1 = internal constant [13 x i8] c"unsigned int\00", section "llvm.metadata"+
%llvm.dbg.basictype = internal constant %llvm.dbg.basictype.type { uint add(uint 36, uint 262144), { }* cast (%llvm.dbg.compile_unit.type* %llvm.dbg.compile_unit to { }*), - sbyte* getelementptr ([14 x sbyte]* %str1, int 0, int 0), + i8* getelementptr ([14 x i8]* %str1, int 0, int 0), { }* null, int 0, uint 64, uint 64, uint 0, uint 5 }, section "llvm.metadata" -%str1 = internal constant [14 x sbyte] c"long long int\00", section "llvm.metadata" +%str1 = internal constant [14 x i8] c"long long int\00", section "llvm.metadata"+
%llvm.dbg.basictype = internal constant %llvm.dbg.basictype.type { uint add(uint 36, uint 262144), { }* cast (%llvm.dbg.compile_unit.type* %llvm.dbg.compile_unit to { }*), - sbyte* getelementptr ([23 x sbyte]* %str1, int 0, int 0), + i8* getelementptr ([23 x i8]* %str1, int 0, int 0), { }* null, int 0, uint 64, uint 64, uint 0, uint 7 }, section "llvm.metadata" -%str1 = internal constant [23 x sbyte] c"long long unsigned int\00", section "llvm.metadata" +%str1 = internal constant [23 x 8] c"long long unsigned int\00", section "llvm.metadata"+
%llvm.dbg.basictype = internal constant %llvm.dbg.basictype.type { uint add(uint 36, uint 262144), { }* cast (%llvm.dbg.compile_unit.type* %llvm.dbg.compile_unit to { }*), - sbyte* getelementptr ([6 x sbyte]* %str1, int 0, int 0), + i8* getelementptr ([6 x i8]* %str1, int 0, int 0), { }* null, int 0, uint 32, uint 32, uint 0, uint 4 }, section "llvm.metadata" -%str1 = internal constant [6 x sbyte] c"float\00", section "llvm.metadata" +%str1 = internal constant [6 x i8] c"float\00", section "llvm.metadata"+
%llvm.dbg.basictype = internal constant %llvm.dbg.basictype.type { uint add(uint 36, uint 262144), { }* cast (%llvm.dbg.compile_unit.type* %llvm.dbg.compile_unit to { }*), - sbyte* getelementptr ([7 x sbyte]* %str1, int 0, int 0), + 8* getelementptr ([7 x 8]* %str1, int 0, int 0), { }* null, int 0, uint 64, uint 64, uint 0, uint 4 }, section "llvm.metadata" -%str1 = internal constant [7 x sbyte] c"double\00", section "llvm.metadata" +%str1 = internal constant [7 x 8] c"double\00", section "llvm.metadata"+
Given the following as an example of C/C++ derived type;
+Given the following as an example of C/C++ derived type:
+typedef const int *IntPtr;+
a C/C++ front-end would generate the following descriptors;
+a C/C++ front-end would generate the following descriptors:
+;; ;; Define the typedef "IntPtr". @@ -1520,14 +1610,14 @@ typedef const int *IntPtr; %llvm.dbg.derivedtype1 = internal constant %llvm.dbg.derivedtype.type { uint add(uint 22, uint 262144), { }* cast (%llvm.dbg.compile_unit.type* %llvm.dbg.compile_unit to { }*), - sbyte* getelementptr ([7 x sbyte]* %str1, int 0, int 0), + i8* getelementptr ([7 x 8]* %str1, int 0, int 0), { }* cast (%llvm.dbg.compile_unit.type* %llvm.dbg.compile_unit to { }*), int 1, uint 0, uint 0, uint 0, { }* cast (%llvm.dbg.derivedtype.type* %llvm.dbg.derivedtype2 to { }*) }, section "llvm.metadata" -%str1 = internal constant [7 x sbyte] c"IntPtr\00", section "llvm.metadata" +%str1 = internal constant [7 x 8] c"IntPtr\00", section "llvm.metadata" ;; ;; Define the pointer type. @@ -1535,7 +1625,7 @@ typedef const int *IntPtr; %llvm.dbg.derivedtype2 = internal constant %llvm.dbg.derivedtype.type { uint add(uint 15, uint 262144), { }* cast (%llvm.dbg.compile_unit.type* %llvm.dbg.compile_unit to { }*), - sbyte* null, + i8* null, { }* null, int 0, uint 32, @@ -1549,7 +1639,7 @@ typedef const int *IntPtr; %llvm.dbg.derivedtype3 = internal constant %llvm.dbg.derivedtype.type { uint add(uint 38, uint 262144), { }* cast (%llvm.dbg.compile_unit.type* %llvm.dbg.compile_unit to { }*), - sbyte* null, + i8* null, { }* null, int 0, uint 0, @@ -1563,15 +1653,16 @@ typedef const int *IntPtr; %llvm.dbg.basictype1 = internal constant %llvm.dbg.basictype.type { uint add(uint 36, uint 262144), { }* cast (%llvm.dbg.compile_unit.type* %llvm.dbg.compile_unit to { }*), - sbyte* getelementptr ([4 x sbyte]* %str2, int 0, int 0), + 8* getelementptr ([4 x 8]* %str2, int 0, int 0), { }* null, int 0, uint 32, uint 32, uint 0, uint 5 }, section "llvm.metadata" -%str2 = internal constant [4 x sbyte] c"int\00", section "llvm.metadata" +%str2 = internal constant [4 x 8] c"int\00", section "llvm.metadata"+
Given the following as an example of C/C++ struct type;
+Given the following as an example of C/C++ struct type:
+
struct Color {
unsigned Red;
@@ -1591,9 +1683,11 @@ struct Color {
unsigned Blue;
};
+a C/C++ front-end would generate the following descriptors;
+a C/C++ front-end would generate the following descriptors:
+
;;
;; Define basic type for unsigned int.
@@ -1601,14 +1695,14 @@ struct Color {
%llvm.dbg.basictype = internal constant %llvm.dbg.basictype.type {
uint add(uint 36, uint 262144),
{ }* cast (%llvm.dbg.compile_unit.type* %llvm.dbg.compile_unit to { }*),
- sbyte* getelementptr ([13 x sbyte]* %str1, int 0, int 0),
+ i8* getelementptr ([13 x i8]* %str1, int 0, int 0),
{ }* null,
int 0,
uint 32,
uint 32,
uint 0,
uint 7 }, section "llvm.metadata"
-%str1 = internal constant [13 x sbyte] c"unsigned int\00", section "llvm.metadata"
+%str1 = internal constant [13 x i8] c"unsigned int\00", section "llvm.metadata"
;;
;; Define composite type for struct Color.
@@ -1616,7 +1710,7 @@ struct Color {
%llvm.dbg.compositetype = internal constant %llvm.dbg.compositetype.type {
uint add(uint 19, uint 262144),
{ }* cast (%llvm.dbg.compile_unit.type* %llvm.dbg.compile_unit to { }*),
- sbyte* getelementptr ([6 x sbyte]* %str2, int 0, int 0),
+ i8* getelementptr ([6 x i8]* %str2, int 0, int 0),
{ }* cast (%llvm.dbg.compile_unit.type* %llvm.dbg.compile_unit to { }*),
int 1,
uint 96,
@@ -1624,7 +1718,7 @@ struct Color {
uint 0,
{ }* null,
{ }* cast ([3 x { }*]* %llvm.dbg.array to { }*) }, section "llvm.metadata"
-%str2 = internal constant [6 x sbyte] c"Color\00", section "llvm.metadata"
+%str2 = internal constant [6 x i8] c"Color\00", section "llvm.metadata"
;;
;; Define the Red field.
@@ -1632,14 +1726,14 @@ struct Color {
%llvm.dbg.derivedtype1 = internal constant %llvm.dbg.derivedtype.type {
uint add(uint 13, uint 262144),
{ }* null,
- sbyte* getelementptr ([4 x sbyte]* %str3, int 0, int 0),
+ i8* getelementptr ([4 x i8]* %str3, int 0, int 0),
{ }* cast (%llvm.dbg.compile_unit.type* %llvm.dbg.compile_unit to { }*),
int 2,
uint 32,
uint 32,
uint 0,
{ }* cast (%llvm.dbg.basictype.type* %llvm.dbg.basictype to { }*) }, section "llvm.metadata"
-%str3 = internal constant [4 x sbyte] c"Red\00", section "llvm.metadata"
+%str3 = internal constant [4 x i8] c"Red\00", section "llvm.metadata"
;;
;; Define the Green field.
@@ -1647,14 +1741,14 @@ struct Color {
%llvm.dbg.derivedtype2 = internal constant %llvm.dbg.derivedtype.type {
uint add(uint 13, uint 262144),
{ }* null,
- sbyte* getelementptr ([6 x sbyte]* %str4, int 0, int 0),
+ i8* getelementptr ([6 x i8]* %str4, int 0, int 0),
{ }* cast (%llvm.dbg.compile_unit.type* %llvm.dbg.compile_unit to { }*),
int 3,
uint 32,
uint 32,
uint 32,
{ }* cast (%llvm.dbg.basictype.type* %llvm.dbg.basictype to { }*) }, section "llvm.metadata"
-%str4 = internal constant [6 x sbyte] c"Green\00", section "llvm.metadata"
+%str4 = internal constant [6 x i8] c"Green\00", section "llvm.metadata"
;;
;; Define the Blue field.
@@ -1662,14 +1756,14 @@ struct Color {
%llvm.dbg.derivedtype3 = internal constant %llvm.dbg.derivedtype.type {
uint add(uint 13, uint 262144),
{ }* null,
- sbyte* getelementptr ([5 x sbyte]* %str5, int 0, int 0),
+ i8* getelementptr ([5 x i8]* %str5, int 0, int 0),
{ }* cast (%llvm.dbg.compile_unit.type* %llvm.dbg.compile_unit to { }*),
int 4,
uint 32,
uint 32,
uint 64,
{ }* cast (%llvm.dbg.basictype.type* %llvm.dbg.basictype to { }*) }, section "llvm.metadata"
-%str5 = internal constant [5 x sbyte] c"Blue\00", section "llvm.metadata"
+%str5 = internal constant [5 x 8] c"Blue\00", section "llvm.metadata"
;;
;; Define the array of fields used by the composite type Color.
@@ -1679,6 +1773,7 @@ struct Color {
{ }* cast (%llvm.dbg.derivedtype.type* %llvm.dbg.derivedtype2 to { }*),
{ }* cast (%llvm.dbg.derivedtype.type* %llvm.dbg.derivedtype3 to { }*) ], section "llvm.metadata"
+Given the following as an example of C/C++ enumeration type;
+Given the following as an example of C/C++ enumeration type:
+
enum Trees {
Spruce = 100,
@@ -1698,9 +1794,11 @@ enum Trees {
Maple = 300
};
+a C/C++ front-end would generate the following descriptors;
+a C/C++ front-end would generate the following descriptors:
+
;;
;; Define composite type for enum Trees
@@ -1708,7 +1806,7 @@ enum Trees {
%llvm.dbg.compositetype = internal constant %llvm.dbg.compositetype.type {
uint add(uint 4, uint 262144),
{ }* cast (%llvm.dbg.compile_unit.type* %llvm.dbg.compile_unit to { }*),
- sbyte* getelementptr ([6 x sbyte]* %str1, int 0, int 0),
+ i8* getelementptr ([6 x i8]* %str1, int 0, int 0),
{ }* cast (%llvm.dbg.compile_unit.type* %llvm.dbg.compile_unit to { }*),
int 1,
uint 32,
@@ -1716,34 +1814,34 @@ enum Trees {
uint 0,
{ }* null,
{ }* cast ([3 x { }*]* %llvm.dbg.array to { }*) }, section "llvm.metadata"
-%str1 = internal constant [6 x sbyte] c"Trees\00", section "llvm.metadata"
+%str1 = internal constant [6 x i8] c"Trees\00", section "llvm.metadata"
;;
;; Define Spruce enumerator.
;;
%llvm.dbg.enumerator1 = internal constant %llvm.dbg.enumerator.type {
uint add(uint 40, uint 262144),
- sbyte* getelementptr ([7 x sbyte]* %str2, int 0, int 0),
+ i8* getelementptr ([7 x i8]* %str2, int 0, int 0),
int 100 }, section "llvm.metadata"
-%str2 = internal constant [7 x sbyte] c"Spruce\00", section "llvm.metadata"
+%str2 = internal constant [7 x i8] c"Spruce\00", section "llvm.metadata"
;;
;; Define Oak enumerator.
;;
%llvm.dbg.enumerator2 = internal constant %llvm.dbg.enumerator.type {
uint add(uint 40, uint 262144),
- sbyte* getelementptr ([4 x sbyte]* %str3, int 0, int 0),
+ i8* getelementptr ([4 x i8]* %str3, int 0, int 0),
int 200 }, section "llvm.metadata"
-%str3 = internal constant [4 x sbyte] c"Oak\00", section "llvm.metadata"
+%str3 = internal constant [4 x i8] c"Oak\00", section "llvm.metadata"
;;
;; Define Maple enumerator.
;;
%llvm.dbg.enumerator3 = internal constant %llvm.dbg.enumerator.type {
uint add(uint 40, uint 262144),
- sbyte* getelementptr ([6 x sbyte]* %str4, int 0, int 0),
+ i8* getelementptr ([6 x i8]* %str4, int 0, int 0),
int 300 }, section "llvm.metadata"
-%str4 = internal constant [6 x sbyte] c"Maple\00", section "llvm.metadata"
+%str4 = internal constant [6 x i8] c"Maple\00", section "llvm.metadata"
;;
;; Define the array of enumerators used by composite type Trees.
@@ -1753,6 +1851,7 @@ enum Trees {
{ }* cast (%llvm.dbg.enumerator.type* %llvm.dbg.enumerator2 to { }*),
{ }* cast (%llvm.dbg.enumerator.type* %llvm.dbg.enumerator3 to { }*) ], section "llvm.metadata"
+
+ src="http://jigsaw.w3.org/css-validator/images/vcss-blue" alt="Valid CSS">
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