[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, 2 insertions, 3 deletions

diff --git a/llvm/test/DebugInfo/X86/debug-info-static-member.ll b/llvm/test/DebugInfo/X86/debug-info-static-member.ll
index 4edaa0b148c..cbe51177c0f 100644
--- a/llvm/test/DebugInfo/X86/debug-info-static-member.ll
+++ b/llvm/test/DebugInfo/X86/debug-info-static-member.ll
@@ -59,10 +59,9 @@ declare void @llvm.dbg.declare(metadata, metadata, metadata) nounwind readnone
 !llvm.dbg.cu = !{!0}
 !llvm.module.flags = !{!34}
 
-!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, producer: "clang version 3.3 (trunk 171914)", isOptimized: false, emissionKind: FullDebug, file: !33, enums: !1, retainedTypes: !1, subprograms: !3, globals: !10, imports:  !1)
+!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, producer: "clang version 3.3 (trunk 171914)", isOptimized: false, emissionKind: FullDebug, file: !33, enums: !1, retainedTypes: !1, globals: !10, imports:  !1)
 !1 = !{}
-!3 = !{!5}
-!5 = distinct !DISubprogram(name: "main", line: 18, isLocal: false, isDefinition: true, virtualIndex: 6, flags: DIFlagPrototyped, isOptimized: false, scopeLine: 23, file: !33, scope: !6, type: !7, variables: !1)
+!5 = distinct !DISubprogram(name: "main", line: 18, isLocal: false, isDefinition: true, virtualIndex: 6, flags: DIFlagPrototyped, isOptimized: false, unit: !0, scopeLine: 23, file: !33, scope: !6, type: !7, variables: !1)
 !6 = !DIFile(filename: "/usr/local/google/home/blaikie/Development/llvm/src/tools/clang/test/CodeGenCXX/debug-info-static-member.cpp", directory: "/home/blaikie/local/Development/llvm/build/clang/x86-64/Debug/llvm")
 !7 = !DISubroutineType(types: !8)
 !8 = !{!9}