[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/inline-member-function.ll b/llvm/test/DebugInfo/X86/inline-member-function.ll
index e1e519bcfca..e92bf0caeef 100644
--- a/llvm/test/DebugInfo/X86/inline-member-function.ll
+++ b/llvm/test/DebugInfo/X86/inline-member-function.ll
@@ -65,7 +65,7 @@ attributes #1 = { nounwind readnone }
 !llvm.module.flags = !{!20, !21}
 !llvm.ident = !{!22}
 
-!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, producer: "clang version 3.5.0 ", isOptimized: false, emissionKind: FullDebug, file: !1, enums: !2, retainedTypes: !3, subprograms: !12, globals: !18, imports: !2)
+!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, producer: "clang version 3.5.0 ", isOptimized: false, emissionKind: FullDebug, file: !1, enums: !2, retainedTypes: !3, globals: !18, imports: !2)
 !1 = !DIFile(filename: "inline.cpp", directory: "/tmp/dbginfo")
 !2 = !{}
 !3 = !{!4}
@@ -76,12 +76,11 @@ attributes #1 = { nounwind readnone }
 !8 = !{!9, !10, !9}
 !9 = !DIBasicType(tag: DW_TAG_base_type, name: "int", size: 32, align: 32, encoding: DW_ATE_signed)
 !10 = !DIDerivedType(tag: DW_TAG_pointer_type, size: 64, align: 64, flags: DIFlagArtificial | DIFlagObjectPointer, baseType: !"_ZTS3foo")
-!12 = !{!13, !17}
-!13 = distinct !DISubprogram(name: "main", line: 7, isLocal: false, isDefinition: true, virtualIndex: 6, flags: DIFlagPrototyped, isOptimized: false, scopeLine: 7, file: !1, scope: !14, type: !15, variables: !2)
+!13 = distinct !DISubprogram(name: "main", line: 7, isLocal: false, isDefinition: true, virtualIndex: 6, flags: DIFlagPrototyped, isOptimized: false, unit: !0, scopeLine: 7, file: !1, scope: !14, type: !15, variables: !2)
 !14 = !DIFile(filename: "inline.cpp", directory: "/tmp/dbginfo")
 !15 = !DISubroutineType(types: !16)
 !16 = !{!9}
-!17 = distinct !DISubprogram(name: "func", linkageName: "_ZN3foo4funcEi", line: 2, isLocal: false, isDefinition: true, virtualIndex: 6, flags: DIFlagPrototyped, isOptimized: false, scopeLine: 2, file: !1, scope: !"_ZTS3foo", type: !7, declaration: !6, variables: !2)
+!17 = distinct !DISubprogram(name: "func", linkageName: "_ZN3foo4funcEi", line: 2, isLocal: false, isDefinition: true, virtualIndex: 6, flags: DIFlagPrototyped, isOptimized: false, unit: !0, scopeLine: 2, file: !1, scope: !"_ZTS3foo", type: !7, declaration: !6, variables: !2)
 !18 = !{!19}
 !19 = !DIGlobalVariable(name: "i", line: 5, isLocal: false, isDefinition: true, scope: null, file: !14, type: !9, variable: i32* @i)
 !20 = !{i32 2, !"Dwarf Version", i32 4}