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-segmented-stacks.ll b/llvm/test/CodeGen/ARM/debug-segmented-stacks.ll
index 7428e54250e..bd0abedc413 100644
--- a/llvm/test/CodeGen/ARM/debug-segmented-stacks.ll
+++ b/llvm/test/CodeGen/ARM/debug-segmented-stacks.ll
@@ -5,7 +5,7 @@
 !llvm.module.flags = !{!9, !10}
 !llvm.ident = !{!11}
 
-define void @test_basic() #0 {
+define void @test_basic() #0 !dbg !4 {
         %mem = alloca i32, i32 10
         call void @dummy_use (i32* %mem, i32 10)
 	ret void
@@ -43,7 +43,7 @@ define void @test_basic() #0 {
 !1 = !DIFile(filename: "var.c", directory: "/tmp")
 !2 = !{}
 !3 = !{!4}
-!4 = distinct !DISubprogram(name: "test_basic", line: 5, isLocal: false, isDefinition: true, virtualIndex: 6, flags: DIFlagPrototyped, isOptimized: false, scopeLine: 5, file: !1, scope: !5, type: !6, function: void ()* @test_basic, variables: !2)
+!4 = distinct !DISubprogram(name: "test_basic", line: 5, isLocal: false, isDefinition: true, virtualIndex: 6, flags: DIFlagPrototyped, isOptimized: false, scopeLine: 5, file: !1, scope: !5, type: !6, variables: !2)
 !5 = !DIFile(filename: "var.c", directory: "/tmp")
 !6 = !DISubroutineType(types: !7)
 !7 = !{!8, !8}