Skip to content
This repository has been archived by the owner on Feb 5, 2019. It is now read-only.

Commit

Permalink
Add support for DW_AT_main_subprogram
Browse files Browse the repository at this point in the history
I'd like the Rust compiler to emit DW_AT_main_subprogram in its DWARF
output, so that debuggers can find the user-provided main entry point.
See rust-lang/rust#32620

This patch adds support for DW_AT_main_subprogram to LLVM to support
this effort.

A variant of this patch was accepted by upstream LLVM; there,
DebugInfoFlags.def already has a flag with value 1<<20, which is why
this patch uses 1<<21 -- this will avoid the need to change the Rust
compiler when a new LLVM is imported.
  • Loading branch information
tromey committed Nov 29, 2016
1 parent f76056b commit 2967489
Show file tree
Hide file tree
Showing 4 changed files with 40 additions and 0 deletions.
1 change: 1 addition & 0 deletions include/llvm/IR/DebugInfoFlags.def
Original file line number Diff line number Diff line change
Expand Up @@ -38,5 +38,6 @@ HANDLE_DI_FLAG((2 << 16), MultipleInheritance)
HANDLE_DI_FLAG((3 << 16), VirtualInheritance)
HANDLE_DI_FLAG((1 << 18), IntroducedVirtual)
HANDLE_DI_FLAG((1 << 19), BitField)
HANDLE_DI_FLAG((1 << 21), MainSubprogram)

#undef HANDLE_DI_FLAG
1 change: 1 addition & 0 deletions include/llvm/IR/DebugInfoMetadata.h
Original file line number Diff line number Diff line change
Expand Up @@ -1402,6 +1402,7 @@ class DISubprogram : public DILocalScope {
}
bool isExplicit() const { return getFlags() & FlagExplicit; }
bool isPrototyped() const { return getFlags() & FlagPrototyped; }
bool isMainSubprogram() const { return getFlags() & FlagMainSubprogram; }

/// \brief Check if this is reference-qualified.
///
Expand Down
3 changes: 3 additions & 0 deletions lib/CodeGen/AsmPrinter/DwarfUnit.cpp
Original file line number Diff line number Diff line change
Expand Up @@ -1260,6 +1260,9 @@ void DwarfUnit::applySubprogramAttributes(const DISubprogram *SP, DIE &SPDie,

if (SP->isExplicit())
addFlag(SPDie, dwarf::DW_AT_explicit);

if (SP->isMainSubprogram())
addFlag(SPDie, dwarf::DW_AT_main_subprogram);
}

void DwarfUnit::constructSubrangeDIE(DIE &Buffer, const DISubrange *SR,
Expand Down
35 changes: 35 additions & 0 deletions test/DebugInfo/Generic/mainsubprogram.ll
Original file line number Diff line number Diff line change
@@ -0,0 +1,35 @@
; REQUIRES: object-emission

; RUN: %llc_dwarf -O0 -filetype=obj < %s > %t
; RUN: llvm-dwarfdump -debug-dump=info %t | FileCheck %s

; Make sure we're emitting DW_AT_main_subprogram.
; CHECK: DW_TAG_subprogram
; CHECK-NOT: {{DW_TAG|NULL}}
; CHECK: DW_AT_name {{.*}} "main"
; CHECK-NOT: {{DW_TAG|NULL}}
; CHECK: DW_AT_main_subprogram [DW_FORM_flag_present] (true)

define i32 @main() #0 !dbg !4 {
entry:
%retval = alloca i32, align 4
store i32 0, i32* %retval
ret i32 0, !dbg !10
}

attributes #0 = { nounwind uwtable "less-precise-fpmad"="false" "no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-leaf" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "unsafe-fp-math"="false" "use-soft-float"="false" }

!llvm.dbg.cu = !{!0}
!llvm.module.flags = !{!9, !11}

!0 = distinct !DICompileUnit(language: DW_LANG_C99, producer: "clang version 3.4 (trunk 185475)", isOptimized: false, emissionKind: FullDebug, file: !1, enums: !2, retainedTypes: !2, globals: !2, imports: !2)
!1 = !DIFile(filename: "CodeGen/dwarf-version.c", directory: "test")
!2 = !{}
!4 = distinct !DISubprogram(name: "main", line: 6, isLocal: false, isDefinition: true, virtualIndex: 6, flags: DIFlagPrototyped | DIFlagMainSubprogram, isOptimized: false, unit: !0, scopeLine: 6, file: !1, scope: !5, type: !6, variables: !2)
!5 = !DIFile(filename: "CodeGen/dwarf-version.c", directory: "test")
!6 = !DISubroutineType(types: !7)
!7 = !{!8}
!8 = !DIBasicType(tag: DW_TAG_base_type, name: "int", size: 32, align: 32, encoding: DW_ATE_signed)
!9 = !{i32 2, !"Dwarf Version", i32 4}
!10 = !DILocation(line: 7, scope: !4)
!11 = !{i32 1, !"Debug Info Version", i32 3}

0 comments on commit 2967489

Please sign in to comment.