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/X86/missing-file-line.ll b/llvm/test/DebugInfo/X86/missing-file-line.ll
index 6fbfb94c39d..19064579af3 100644
--- a/llvm/test/DebugInfo/X86/missing-file-line.ll
+++ b/llvm/test/DebugInfo/X86/missing-file-line.ll
@@ -11,7 +11,7 @@ target triple = "x86_64-unknown-linux-gnu"
 
 %struct.S = type { %struct.S* }
 
-define void @f() {
+define void @f() !dbg !4 {
   %x = alloca %struct.S, align 8
   ; CHECK: DW_TAG_typedef
   ; CHECK-NOT: DW_AT_decl_file
@@ -40,7 +40,7 @@ declare void @llvm.dbg.declare(metadata, metadata, metadata) #1
 !1 = !DIFile(filename: "file.c", directory: "/dir")
 !2 = !{}
 !3 = !{!4}
-!4 = distinct !DISubprogram(name: "f", scope: !1, file: !1, line: 7, type: !5, isLocal: false, isDefinition: true, scopeLine: 7, isOptimized: false, function: void ()* @f, variables: !2)
+!4 = distinct !DISubprogram(name: "f", scope: !1, file: !1, line: 7, type: !5, isLocal: false, isDefinition: true, scopeLine: 7, isOptimized: false, variables: !2)
 !5 = !DISubroutineType(types: !6)
 !6 = !{null}
 !7 = !{i32 2, !"Dwarf Version", i32 4}