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
diff --git a/llvm/lib/Transforms/Utils/CloneFunction.cpp b/llvm/lib/Transforms/Utils/CloneFunction.cpp
index 86f7068..bd6cd3a 100644
--- a/llvm/lib/Transforms/Utils/CloneFunction.cpp
+++ b/llvm/lib/Transforms/Utils/CloneFunction.cpp
@@ -188,11 +188,9 @@
const DISubprogram *OldSubprogramMDNode = FindSubprogram(OldFunc, Finder);
if (!OldSubprogramMDNode) return;
- // Ensure that OldFunc appears in the map.
- // (if it's already there it must point to NewFunc anyway)
- VMap[OldFunc] = NewFunc;
auto *NewSubprogram =
cast<DISubprogram>(MapMetadata(OldSubprogramMDNode, VMap));
+ NewFunc->setSubprogram(NewSubprogram);
for (auto *CU : Finder.compile_units()) {
auto Subprograms = CU->getSubprograms();