[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, 3 insertions, 4 deletions

diff --git a/llvm/test/DebugInfo/X86/dbg-value-inlined-parameter.ll b/llvm/test/DebugInfo/X86/dbg-value-inlined-parameter.ll
index eb6d68b2678..f647d60ff74 100644
--- a/llvm/test/DebugInfo/X86/dbg-value-inlined-parameter.ll
+++ b/llvm/test/DebugInfo/X86/dbg-value-inlined-parameter.ll
@@ -74,13 +74,13 @@ declare void @llvm.dbg.value(metadata, i64, metadata, metadata) nounwind readnon
 !llvm.dbg.cu = !{!2}
 !llvm.module.flags = !{!43}
 
-!0 = distinct !DISubprogram(name: "foo", line: 8, isLocal: false, isDefinition: true, virtualIndex: 6, flags: DIFlagPrototyped, isOptimized: true, scopeLine: 8, file: !1, scope: !1, type: !3, variables: !41)
+!0 = distinct !DISubprogram(name: "foo", line: 8, isLocal: false, isDefinition: true, virtualIndex: 6, flags: DIFlagPrototyped, isOptimized: true, unit: !2, scopeLine: 8, file: !1, scope: !1, type: !3, variables: !41)
 !1 = !DIFile(filename: "nm2.c", directory: "/private/tmp")
-!2 = distinct !DICompileUnit(language: DW_LANG_C99, producer: "clang version 2.9 (trunk 125693)", isOptimized: true, emissionKind: FullDebug, file: !42, enums: !{}, retainedTypes: !{}, subprograms: !39, globals: !40, imports:  !44)
+!2 = distinct !DICompileUnit(language: DW_LANG_C99, producer: "clang version 2.9 (trunk 125693)", isOptimized: true, emissionKind: FullDebug, file: !42, enums: !{}, retainedTypes: !{}, globals: !40, imports:  !44)
 !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: "foobar", line: 15, isLocal: false, isDefinition: true, virtualIndex: 6, isOptimized: true, file: !1, scope: !1, type: !7)
+!6 = distinct !DISubprogram(name: "foobar", line: 15, isLocal: false, isDefinition: true, virtualIndex: 6, isOptimized: true, unit: !2, file: !1, scope: !1, type: !7)
 !7 = !DISubroutineType(types: !8)
 !8 = !{null}
 !9 = !DILocalVariable(name: "sp", line: 7, arg: 1, scope: !0, file: !1, type: !10)
@@ -109,7 +109,6 @@ declare void @llvm.dbg.value(metadata, i64, metadata, metadata) nounwind readnon
 !36 = !DILocation(line: 9, column: 3, scope: !23, inlinedAt: !32)
 !37 = !DILocation(line: 10, column: 3, scope: !23, inlinedAt: !32)
 !38 = !DILocation(line: 17, column: 1, scope: !33)
-!39 = !{!0, !6}
 !40 = !{!19}
 !41 = !{!9, !18}
 !42 = !DIFile(filename: "nm2.c", directory: "/private/tmp")