[PR27284] Reverse the ownership between DICompileUnit and DISubprogram.

Currently each Function points to a DISubprogram and DISubprogram has a
scope field. For member functions the scope is a DICompositeType. DIScopes
point to the DICompileUnit to facilitate type uniquing.

Distinct DISubprograms (with isDefinition: true) are not part of the type
hierarchy and cannot be uniqued. This change removes the subprograms
list from DICompileUnit and instead adds a pointer to the owning compile
unit to distinct DISubprograms. This would make it easy for ThinLTO to
strip unneeded DISubprograms and their transitively referenced debug info.

Motivation
----------

Materializing DISubprograms is currently the most expensive operation when
doing a ThinLTO build of clang.

We want the DISubprogram to be stored in a separate Bitcode block (or the
same block as the function body) so we can avoid having to expensively
deserialize all DISubprograms together with the global metadata. If a
function has been inlined into another subprogram we need to store a
reference the block containing the inlined subprogram.

Attached to https://llvm.org/bugs/show_bug.cgi?id=27284 is a python script
that updates LLVM IR testcases to the new format.

http://reviews.llvm.org/D19034
<rdar://problem/25256815>

llvm-svn: 266446

1 files changed, 6 insertions, 7 deletions

diff --git a/llvm/test/DebugInfo/X86/reference-argument.ll b/llvm/test/DebugInfo/X86/reference-argument.ll
index 75e9fcba826..52e9290eacc 100644
--- a/llvm/test/DebugInfo/X86/reference-argument.ll
+++ b/llvm/test/DebugInfo/X86/reference-argument.ll
@@ -44,11 +44,10 @@ declare void @_ZN4SValD2Ev(%class.SVal* %this)
 !llvm.dbg.cu = !{!0}
 !llvm.module.flags = !{!47, !68}
 
-!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, producer: "clang version 3.4 ", isOptimized: false, emissionKind: FullDebug, file: !1, enums: !2, retainedTypes: !2, subprograms: !3, globals: !2, imports: !2)
+!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, producer: "clang version 3.4 ", isOptimized: false, emissionKind: FullDebug, file: !1, enums: !2, retainedTypes: !2, globals: !2, imports: !2)
 !1 = !DIFile(filename: "aggregate-indirect-arg.cpp", directory: "")
 !2 = !{}
-!3 = !{!4, !29, !33, !34, !35}
-!4 = distinct !DISubprogram(name: "bar", linkageName: "_Z3barR4SVal", line: 19, isLocal: false, isDefinition: true, virtualIndex: 6, flags: DIFlagPrototyped, isOptimized: false, scopeLine: 19, file: !1, scope: !5, type: !6, variables: !2)
+!4 = distinct !DISubprogram(name: "bar", linkageName: "_Z3barR4SVal", line: 19, isLocal: false, isDefinition: true, virtualIndex: 6, flags: DIFlagPrototyped, isOptimized: false, unit: !0, scopeLine: 19, file: !1, scope: !5, type: !6, variables: !2)
 !5 = !DIFile(filename: "aggregate-indirect-arg.cpp", directory: "")
 !6 = !DISubroutineType(types: !7)
 !7 = !{null, !8}
@@ -70,13 +69,13 @@ declare void @_ZN4SValD2Ev(%class.SVal* %this)
 !25 = !{null, !19, !26}
 !26 = !DIDerivedType(tag: DW_TAG_reference_type, baseType: !27)
 !27 = !DIDerivedType(tag: DW_TAG_const_type, baseType: !9)
-!29 = distinct !DISubprogram(name: "main", line: 25, isLocal: false, isDefinition: true, virtualIndex: 6, flags: DIFlagPrototyped, isOptimized: false, scopeLine: 25, file: !1, scope: !5, type: !30, variables: !2)
+!29 = distinct !DISubprogram(name: "main", line: 25, isLocal: false, isDefinition: true, virtualIndex: 6, flags: DIFlagPrototyped, isOptimized: false, unit: !0, scopeLine: 25, file: !1, scope: !5, type: !30, variables: !2)
 !30 = !DISubroutineType(types: !31)
 !31 = !{!32}
 !32 = !DIBasicType(tag: DW_TAG_base_type, name: "int", size: 32, align: 32, encoding: DW_ATE_signed)
-!33 = distinct !DISubprogram(name: "~SVal", linkageName: "_ZN4SValD1Ev", line: 14, isLocal: false, isDefinition: true, virtualIndex: 6, flags: DIFlagPrototyped, isOptimized: false, scopeLine: 14, file: !1, scope: null, type: !17, declaration: !16, variables: !2)
-!34 = distinct !DISubprogram(name: "~SVal", linkageName: "_ZN4SValD2Ev", line: 14, isLocal: false, isDefinition: true, virtualIndex: 6, flags: DIFlagPrototyped, isOptimized: false, scopeLine: 14, file: !1, scope: null, type: !17, declaration: !16, variables: !2)
-!35 = distinct !DISubprogram(name: "foo", linkageName: "_ZN1A3fooE4SVal", line: 22, isLocal: false, isDefinition: true, virtualIndex: 6, flags: DIFlagPrototyped, isOptimized: false, scopeLine: 22, file: !1, scope: null, type: !36, declaration: !41, variables: !2)
+!33 = distinct !DISubprogram(name: "~SVal", linkageName: "_ZN4SValD1Ev", line: 14, isLocal: false, isDefinition: true, virtualIndex: 6, flags: DIFlagPrototyped, isOptimized: false, unit: !0, scopeLine: 14, file: !1, scope: null, type: !17, declaration: !16, variables: !2)
+!34 = distinct !DISubprogram(name: "~SVal", linkageName: "_ZN4SValD2Ev", line: 14, isLocal: false, isDefinition: true, virtualIndex: 6, flags: DIFlagPrototyped, isOptimized: false, unit: !0, scopeLine: 14, file: !1, scope: null, type: !17, declaration: !16, variables: !2)
+!35 = distinct !DISubprogram(name: "foo", linkageName: "_ZN1A3fooE4SVal", line: 22, isLocal: false, isDefinition: true, virtualIndex: 6, flags: DIFlagPrototyped, isOptimized: false, unit: !0, scopeLine: 22, file: !1, scope: null, type: !36, declaration: !41, variables: !2)
 !36 = !DISubroutineType(types: !37)
 !37 = !{null, !38, !9}
 !38 = !DIDerivedType(tag: DW_TAG_pointer_type, size: 64, align: 64, flags: DIFlagArtificial | DIFlagObjectPointer, baseType: !39)