DI: Reverse direction of subprogram -> function edge.

Previously, subprograms contained a metadata reference to the function they
described. Because most clients need to get or set a subprogram for a given
function rather than the other way around, this created unneeded inefficiency.

For example, many passes needed to call the function llvm::makeSubprogramMap()
to build a mapping from functions to subprograms, and the IR linker needed to
fix up function references in a way that caused quadratic complexity in the IR
linking phase of LTO.

This change reverses the direction of the edge by storing the subprogram as
function-level metadata and removing DISubprogram's function field.

Since this is an IR change, a bitcode upgrade has been provided.

Fixes PR23367. An upgrade script for textual IR for out-of-tree clients is
attached to the PR.

Differential Revision: http://reviews.llvm.org/D14265

llvm-svn: 252219

1 files changed, 2 insertions, 2 deletions

diff --git a/llvm/test/CodeGen/ARM/debug-info-sreg2.ll b/llvm/test/CodeGen/ARM/debug-info-sreg2.ll
index 9d086d7fba5..eadf1b48156 100644
--- a/llvm/test/CodeGen/ARM/debug-info-sreg2.ll
+++ b/llvm/test/CodeGen/ARM/debug-info-sreg2.ll
@@ -12,7 +12,7 @@ target triple = "thumbv7-apple-macosx10.6.7"
 ; CHECK-NEXT:           Ending address offset:
 ; CHECK-NEXT:            Location description: 90 {{.. .. .. .. $}}
 
-define void @_Z3foov() optsize ssp {
+define void @_Z3foov() optsize ssp !dbg !1 {
 entry:
   %call = tail call float @_Z3barv() optsize, !dbg !11
   tail call void @llvm.dbg.value(metadata float %call, i64 0, metadata !5, metadata !DIExpression()), !dbg !11
@@ -44,7 +44,7 @@ declare void @llvm.dbg.value(metadata, i64, metadata, metadata) nounwind readnon
 !llvm.module.flags = !{!20}
 
 !0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, producer: "clang version 3.0 (trunk 130845)", isOptimized: true, emissionKind: 1, file: !18, enums: !19, retainedTypes: !19, subprograms: !16, imports:  null)
-!1 = distinct !DISubprogram(name: "foo", linkageName: "_Z3foov", line: 5, isLocal: false, isDefinition: true, virtualIndex: 6, flags: DIFlagPrototyped, isOptimized: true, scopeLine: 5, file: !18, scope: !2, type: !3, function: void ()* @_Z3foov, variables: !17)
+!1 = distinct !DISubprogram(name: "foo", linkageName: "_Z3foov", line: 5, isLocal: false, isDefinition: true, virtualIndex: 6, flags: DIFlagPrototyped, isOptimized: true, scopeLine: 5, file: !18, scope: !2, type: !3, variables: !17)
 !2 = !DIFile(filename: "k.cc", directory: "/private/tmp")
 !3 = !DISubroutineType(types: !4)
 !4 = !{null}