[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, 4 deletions

diff --git a/llvm/test/Transforms/SampleProfile/inline-coverage.ll b/llvm/test/Transforms/SampleProfile/inline-coverage.ll
index 3d7d8c806ae..f10373e5a3c 100644
--- a/llvm/test/Transforms/SampleProfile/inline-coverage.ll
+++ b/llvm/test/Transforms/SampleProfile/inline-coverage.ll
@@ -90,16 +90,15 @@ for.end:                                          ; preds = %for.cond
 !llvm.module.flags = !{!13, !14}
 !llvm.ident = !{!15}
 
-!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: !1, producer: "clang version 3.8.0 (trunk 251738) (llvm/trunk 251737)", isOptimized: false, runtimeVersion: 0, emissionKind: NoDebug, enums: !2, subprograms: !3)
+!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: !1, producer: "clang version 3.8.0 (trunk 251738) (llvm/trunk 251737)", isOptimized: false, runtimeVersion: 0, emissionKind: NoDebug, enums: !2)
 !1 = !DIFile(filename: "coverage.cc", directory: ".")
 !2 = !{}
-!3 = !{!4, !9}
-!4 = distinct !DISubprogram(name: "foo", linkageName: "_Z3fool", scope: !1, file: !1, line: 3, type: !5, isLocal: false, isDefinition: true, scopeLine: 3, flags: DIFlagPrototyped, isOptimized: false, variables: !2)
+!4 = distinct !DISubprogram(name: "foo", linkageName: "_Z3fool", scope: !1, file: !1, line: 3, type: !5, isLocal: false, isDefinition: true, scopeLine: 3, flags: DIFlagPrototyped, isOptimized: false, unit: !0, variables: !2)
 !5 = !DISubroutineType(types: !6)
 !6 = !{!7, !8}
 !7 = !DIBasicType(name: "long long int", size: 64, align: 64, encoding: DW_ATE_signed)
 !8 = !DIBasicType(name: "long int", size: 64, align: 64, encoding: DW_ATE_signed)
-!9 = distinct !DISubprogram(name: "main", scope: !1, file: !1, line: 7, type: !10, isLocal: false, isDefinition: true, scopeLine: 7, flags: DIFlagPrototyped, isOptimized: false, variables: !2)
+!9 = distinct !DISubprogram(name: "main", scope: !1, file: !1, line: 7, type: !10, isLocal: false, isDefinition: true, scopeLine: 7, flags: DIFlagPrototyped, isOptimized: false, unit: !0, variables: !2)
 !10 = !DISubroutineType(types: !11)
 !11 = !{!12}
 !12 = !DIBasicType(name: "int", size: 32, align: 32, encoding: DW_ATE_signed)