[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

2 files changed, 5 insertions, 7 deletions

diff --git a/test/Transforms/ObjCARC/basic.ll b/test/Transforms/ObjCARC/basic.ll
index 61f027c6790..c10c3b1381b 100644
--- a/test/Transforms/ObjCARC/basic.ll
+++ b/test/Transforms/ObjCARC/basic.ll
@@ -3041,12 +3041,11 @@ define void @test67(i8* %x) {
 
 !0 = !{}
 !1 = !{i32 1, !"Debug Info Version", i32 3}
-!2 = distinct !DISubprogram()
+!2 = distinct !DISubprogram(unit: !3)
 !3 = distinct !DICompileUnit(language: DW_LANG_C99, producer: "clang",
                              file: !4,
                              isOptimized: true, flags: "-O2",
-                             splitDebugFilename: "abc.debug", emissionKind: 2,
-                             subprograms: !{!2})
+                             splitDebugFilename: "abc.debug", emissionKind: 2)
 !4 = !DIFile(filename: "path/to/file", directory: "/path/to/dir")
 !5 = !{i32 2, !"Debug Info Version", i32 3}
 
diff --git a/test/Transforms/ObjCARC/ensure-that-exception-unwind-path-is-visited.ll b/test/Transforms/ObjCARC/ensure-that-exception-unwind-path-is-visited.ll
index 5971a2fa006..c856706d3f0 100644
--- a/test/Transforms/ObjCARC/ensure-that-exception-unwind-path-is-visited.ll
+++ b/test/Transforms/ObjCARC/ensure-that-exception-unwind-path-is-visited.ll
@@ -113,10 +113,9 @@ declare void @llvm.dbg.value(metadata, i64, metadata, metadata) nounwind readnon
 !llvm.dbg.cu = !{!0}
 !llvm.module.flags = !{!33, !34, !35, !36, !61}
 
-!0 = distinct !DICompileUnit(language: DW_LANG_ObjC, producer: "clang version 3.3 ", isOptimized: true, runtimeVersion: 2, emissionKind: FullDebug, file: !60, enums: !1, retainedTypes: !1, subprograms: !3, globals: !1)
+!0 = distinct !DICompileUnit(language: DW_LANG_ObjC, producer: "clang version 3.3 ", isOptimized: true, runtimeVersion: 2, emissionKind: FullDebug, file: !60, enums: !1, retainedTypes: !1, globals: !1)
 !1 = !{}
-!3 = !{!5, !27}
-!5 = distinct !DISubprogram(name: "main", line: 9, isLocal: false, isDefinition: true, virtualIndex: 6, isOptimized: true, scopeLine: 10, file: !60, scope: !6, type: !7, variables: !11)
+!5 = distinct !DISubprogram(name: "main", line: 9, isLocal: false, isDefinition: true, virtualIndex: 6, isOptimized: true, unit: !0, scopeLine: 10, file: !60, scope: !6, type: !7, variables: !11)
 !6 = !DIFile(filename: "test.m", directory: "/Volumes/Files/gottesmmcab/Radar/12906997")
 !7 = !DISubroutineType(types: !8)
 !8 = !{!9}
@@ -137,7 +136,7 @@ declare void @llvm.dbg.value(metadata, i64, metadata, metadata) nounwind readnon
 !24 = !DIBasicType(tag: DW_TAG_base_type, name: "signed char", size: 8, align: 8, encoding: DW_ATE_signed_char)
 !25 = !DILocalVariable(name: "obj2", line: 15, scope: !26, file: !6, type: !14)
 !26 = distinct !DILexicalBlock(line: 14, column: 0, file: !60, scope: !22)
-!27 = distinct !DISubprogram(name: "ThrowFunc", line: 4, isLocal: true, isDefinition: true, virtualIndex: 6, flags: DIFlagPrototyped, isOptimized: true, scopeLine: 5, file: !60, scope: !6, type: !28, variables: !31)
+!27 = distinct !DISubprogram(name: "ThrowFunc", line: 4, isLocal: true, isDefinition: true, virtualIndex: 6, flags: DIFlagPrototyped, isOptimized: true, unit: !0, scopeLine: 5, file: !60, scope: !6, type: !28, variables: !31)
 !28 = !DISubroutineType(types: !29)
 !29 = !{null, !14}
 !31 = !{!32}