[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>

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@266446 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 2 insertions, 2 deletions

diff --git a/test/CodeGen/ARM/2010-06-25-Thumb2ITInvalidIterator.ll b/test/CodeGen/ARM/2010-06-25-Thumb2ITInvalidIterator.ll
index 2bea37c5486..5ae1b6626f1 100644
--- a/test/CodeGen/ARM/2010-06-25-Thumb2ITInvalidIterator.ll
+++ b/test/CodeGen/ARM/2010-06-25-Thumb2ITInvalidIterator.ll
@@ -47,9 +47,9 @@ declare void @llvm.dbg.value(metadata, i64, metadata, metadata) nounwind readnon
 !llvm.dbg.cu = !{!3}
 
 !0 = !DILocalVariable(name: "buf", line: 4, arg: 1, scope: !1, file: !2, type: !6)
-!1 = distinct !DISubprogram(name: "x0", linkageName: "x0", line: 5, isLocal: false, isDefinition: true, virtualIndex: 6, isOptimized: false, file: !26, scope: null, type: !4)
+!1 = distinct !DISubprogram(name: "x0", linkageName: "x0", line: 5, isLocal: false, isDefinition: true, virtualIndex: 6, isOptimized: false, unit: !3, file: !26, scope: null, type: !4)
 !2 = !DIFile(filename: "t.c", directory: "/private/tmp")
-!3 = distinct !DICompileUnit(language: DW_LANG_C99, producer: "clang 2.0", isOptimized: true, file: !26, subprograms: !{!0, !8, !10, !12}, globals: !{!14})
+!3 = distinct !DICompileUnit(language: DW_LANG_C99, producer: "clang 2.0", isOptimized: true, file: !26, globals: !{!14})
 !4 = !DISubroutineType(types: !5)
 !5 = !{null}
 !6 = !DIDerivedType(tag: DW_TAG_pointer_type, size: 32, align: 32, file: !26, scope: !2, baseType: !7)