[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, 3 deletions

diff --git a/llvm/test/Transforms/SampleProfile/inline-combine.ll b/llvm/test/Transforms/SampleProfile/inline-combine.ll
index 8ea074c90d3..48c1fce93f9 100644
--- a/llvm/test/Transforms/SampleProfile/inline-combine.ll
+++ b/llvm/test/Transforms/SampleProfile/inline-combine.ll
@@ -37,10 +37,10 @@ define void @bar(%"class.llvm::SmallVectorImpl"* %this) comdat align 2 !dbg !8 {
 !0 = !{i32 2, !"Dwarf Version", i32 4}
 !1 = !{i32 1, !"Debug Info Version", i32 3}
 !2 = !{!"clang version 3.5 "}
-!3 = distinct !DISubprogram(name: "foo", scope: !4, file: !4, line: 3, type: !5, isLocal: false, isDefinition: true, scopeLine: 3, virtualIndex: 6, flags: DIFlagPrototyped, isOptimized: false, variables: !6)
+!3 = distinct !DISubprogram(name: "foo", scope: !4, file: !4, line: 3, type: !5, isLocal: false, isDefinition: true, scopeLine: 3, virtualIndex: 6, flags: DIFlagPrototyped, isOptimized: false, unit: !9, variables: !6)
 !4 = !DIFile(filename: "test.cc", directory: ".")
 !5 = !DISubroutineType(types: !6)
 !6 = !{}
 !7 = !DILocation(line: 4, scope: !3)
-!8 = distinct !DISubprogram(name: "bar", scope: !4, file: !4, line: 7, type: !5, isLocal: false, isDefinition: true, scopeLine: 7, virtualIndex: 6, flags: DIFlagPrototyped, isOptimized: false, variables: !6)
-!9 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, producer: "clang version 3.5 ", isOptimized: false, emissionKind: FullDebug, file: !4, subprograms: !{!3, !8})
+!8 = distinct !DISubprogram(name: "bar", scope: !4, file: !4, line: 7, type: !5, isLocal: false, isDefinition: true, scopeLine: 7, virtualIndex: 6, flags: DIFlagPrototyped, isOptimized: false, unit: !9, variables: !6)
+!9 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, producer: "clang version 3.5 ", isOptimized: false, emissionKind: FullDebug, file: !4)