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/DebugInfo/ARM/header.ll b/llvm/test/DebugInfo/ARM/header.ll
index 67accd0fa53..bb1f141c84d 100644
--- a/llvm/test/DebugInfo/ARM/header.ll
+++ b/llvm/test/DebugInfo/ARM/header.ll
@@ -12,7 +12,7 @@
 
 ; CHECK:  .section        __DWARF,__debug_str,regular,debug
 
-define void @f() {
+define void @f() !dbg !4 {
   ret void, !dbg !9
 }
 !llvm.dbg.cu = !{!0}
@@ -22,7 +22,7 @@ define void @f() {
 !1 = !DIFile(filename: "/foo/test.c", directory: "/foo")
 !2 = !{}
 !3 = !{!4}
-!4 = distinct !DISubprogram(name: "f", scope: !1, file: !1, line: 1, type: !5, isLocal: false, isDefinition: true, scopeLine: 1, flags: DIFlagPrototyped, isOptimized: true, function: void ()* @f, variables: !2)
+!4 = distinct !DISubprogram(name: "f", scope: !1, file: !1, line: 1, type: !5, isLocal: false, isDefinition: true, scopeLine: 1, flags: DIFlagPrototyped, isOptimized: true, variables: !2)
 !5 = !DISubroutineType(types: !6)
 !6 = !{null}
 !7 = !{i32 2, !"Dwarf Version", i32 4}