[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>

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@266446 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 4 insertions, 5 deletions

diff --git a/test/CodeGen/ARM/debug-info-s16-reg.ll b/test/CodeGen/ARM/debug-info-s16-reg.ll
index 64944ac0d49..2987b9a2105 100644
--- a/test/CodeGen/ARM/debug-info-s16-reg.ll
+++ b/test/CodeGen/ARM/debug-info-s16-reg.ll
@@ -65,14 +65,14 @@ declare void @llvm.dbg.value(metadata, i64, metadata, metadata) nounwind readnon
 !llvm.dbg.cu = !{!2}
 !llvm.module.flags = !{!53}
 
-!0 = distinct !DISubprogram(name: "inlineprinter", line: 5, isLocal: false, isDefinition: true, virtualIndex: 6, flags: DIFlagPrototyped, isOptimized: true, scopeLine: 5, file: !51, scope: !1, type: !3, variables: !48)
+!0 = distinct !DISubprogram(name: "inlineprinter", line: 5, isLocal: false, isDefinition: true, virtualIndex: 6, flags: DIFlagPrototyped, isOptimized: true, unit: !2, scopeLine: 5, file: !51, scope: !1, type: !3, variables: !48)
 !1 = !DIFile(filename: "a.c", directory: "/private/tmp")
-!2 = distinct !DICompileUnit(language: DW_LANG_C99, producer: "clang version 3.0 (trunk 129915)", isOptimized: true, emissionKind: FullDebug, file: !51, enums: !52, retainedTypes: !52, subprograms: !47, imports:  null)
+!2 = distinct !DICompileUnit(language: DW_LANG_C99, producer: "clang version 3.0 (trunk 129915)", isOptimized: true, emissionKind: FullDebug, file: !51, enums: !52, retainedTypes: !52, imports:  null)
 !3 = !DISubroutineType(types: !4)
 !4 = !{!5}
 !5 = !DIBasicType(tag: DW_TAG_base_type, name: "int", size: 32, align: 32, encoding: DW_ATE_signed)
-!6 = distinct !DISubprogram(name: "printer", line: 12, isLocal: false, isDefinition: true, virtualIndex: 6, flags: DIFlagPrototyped, isOptimized: true, scopeLine: 12, file: !51, scope: !1, type: !3, variables: !49)
-!7 = distinct !DISubprogram(name: "main", line: 18, isLocal: false, isDefinition: true, virtualIndex: 6, flags: DIFlagPrototyped, isOptimized: true, scopeLine: 18, file: !51, scope: !1, type: !3, variables: !50)
+!6 = distinct !DISubprogram(name: "printer", line: 12, isLocal: false, isDefinition: true, virtualIndex: 6, flags: DIFlagPrototyped, isOptimized: true, unit: !2, scopeLine: 12, file: !51, scope: !1, type: !3, variables: !49)
+!7 = distinct !DISubprogram(name: "main", line: 18, isLocal: false, isDefinition: true, virtualIndex: 6, flags: DIFlagPrototyped, isOptimized: true, unit: !2, scopeLine: 18, file: !51, scope: !1, type: !3, variables: !50)
 !8 = !DILocalVariable(name: "ptr", line: 4, arg: 1, scope: !0, file: !1, type: !9)
 !9 = !DIDerivedType(tag: DW_TAG_pointer_type, size: 32, align: 32, scope: !2, baseType: null)
 !10 = !DILocalVariable(name: "val", line: 4, arg: 2, scope: !0, file: !1, type: !11)
@@ -117,7 +117,6 @@ declare void @llvm.dbg.value(metadata, i64, metadata, metadata) nounwind readnon
 !44 = !DILocation(line: 6, column: 3, scope: !28, inlinedAt: !40)
 !45 = !DILocation(line: 22, column: 3, scope: !23)
 !46 = !DILocation(line: 23, column: 1, scope: !23)
-!47 = !{!0, !6, !7}
 !48 = !{!8, !10, !12}
 !49 = !{!14, !15, !16}
 !50 = !{!17, !18, !22}