[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, 3 insertions, 4 deletions

diff --git a/test/CodeGen/NVPTX/debug-file-loc.ll b/test/CodeGen/NVPTX/debug-file-loc.ll
index ccea7228109..008e9ce5458 100644
--- a/test/CodeGen/NVPTX/debug-file-loc.ll
+++ b/test/CodeGen/NVPTX/debug-file-loc.ll
@@ -30,14 +30,13 @@ bb:
 !llvm.dbg.cu = !{!0}
 !llvm.module.flags = !{!8, !9}
 
-!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: !1, producer: "", isOptimized: false, runtimeVersion: 0, emissionKind: LineTablesOnly, enums: !2, subprograms: !3)
+!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: !1, producer: "", isOptimized: false, runtimeVersion: 0, emissionKind: LineTablesOnly, enums: !2)
 !1 = !DIFile(filename: "bar.cu", directory: "/source/dir")
 !2 = !{}
-!3 = !{!4, !7}
-!4 = distinct !DISubprogram(name: "foo", scope: !5, file: !5, line: 1, type: !6, isLocal: false, isDefinition: true, scopeLine: 1, flags: DIFlagPrototyped, isOptimized: false, variables: !2)
+!4 = distinct !DISubprogram(name: "foo", scope: !5, file: !5, line: 1, type: !6, isLocal: false, isDefinition: true, scopeLine: 1, flags: DIFlagPrototyped, isOptimized: false, unit: !0, variables: !2)
 !5 = !DIFile(filename: "foo.h", directory: "/source/dir")
 !6 = !DISubroutineType(types: !2)
-!7 = distinct !DISubprogram(name: "bar", scope: !1, file: !1, line: 2, type: !6, isLocal: false, isDefinition: true, scopeLine: 2, flags: DIFlagPrototyped, isOptimized: false, variables: !2)
+!7 = distinct !DISubprogram(name: "bar", scope: !1, file: !1, line: 2, type: !6, isLocal: false, isDefinition: true, scopeLine: 2, flags: DIFlagPrototyped, isOptimized: false, unit: !0, variables: !2)
 !8 = !{i32 2, !"Dwarf Version", i32 4}
 !9 = !{i32 2, !"Debug Info Version", i32 3}
 !10 = !DILocation(line: 1, column: 31, scope: !4)