[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/Transforms/CodeGenPrepare/X86/catchpad-phi-cast.ll b/llvm/test/Transforms/CodeGenPrepare/X86/catchpad-phi-cast.ll
index 25cbbaca606..66bfc99d137 100644
--- a/llvm/test/Transforms/CodeGenPrepare/X86/catchpad-phi-cast.ll
+++ b/llvm/test/Transforms/CodeGenPrepare/X86/catchpad-phi-cast.ll
@@ -101,10 +101,9 @@ catch:
 !llvm.module.flags = !{!7, !8, !9}
 !llvm.ident = !{!10}
 
-!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "clang version 3.8.0 (trunk 254906) (llvm/trunk 254917)", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: null, subprograms: !3)
+!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "clang version 3.8.0 (trunk 254906) (llvm/trunk 254917)", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: null)
 !1 = !DIFile(filename: "t.c", directory: "D:\5Csrc\5Cllvm\5Cbuild")
-!3 = !{!4}
-!4 = distinct !DISubprogram(name: "test_dbg_value", scope: !1, file: !1, line: 1, type: !5, isLocal: false, isDefinition: true, scopeLine: 1, isOptimized: false, variables: null)
+!4 = distinct !DISubprogram(name: "test_dbg_value", scope: !1, file: !1, line: 1, type: !5, isLocal: false, isDefinition: true, scopeLine: 1, isOptimized: false, unit: !0, variables: null)
 !5 = !DISubroutineType(types: !6)
 !6 = !{null}
 !7 = !{i32 2, !"Dwarf Version", i32 4}