[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, 1 insertions, 1 deletions

diff --git a/llvm/test/DebugInfo/PowerPC/tls-fission.ll b/llvm/test/DebugInfo/PowerPC/tls-fission.ll
index b32c2990a70..fff78d4a16f 100644
--- a/llvm/test/DebugInfo/PowerPC/tls-fission.ll
+++ b/llvm/test/DebugInfo/PowerPC/tls-fission.ll
@@ -22,7 +22,7 @@
 !llvm.dbg.cu = !{!0}
 !llvm.module.flags = !{!7, !8}
 
-!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, producer: "clang version 3.4 ", isOptimized: false, splitDebugFilename: "tls.dwo", emissionKind: FullDebug, file: !1, enums: !2, retainedTypes: !2, subprograms: !2, globals: !3, imports: !2)
+!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, producer: "clang version 3.4 ", isOptimized: false, splitDebugFilename: "tls.dwo", emissionKind: FullDebug, file: !1, enums: !2, retainedTypes: !2, globals: !3, imports: !2)
 !1 = !DIFile(filename: "tls.cpp", directory: "/tmp")
 !2 = !{}
 !3 = !{!4}