[PR27284] Reverse the ownership between DICompileUnit and DISubprogram.
Currently each Function points to a DISubprogram and DISubprogram has a
scope field. For member functions the scope is a DICompositeType. DIScopes
point to the DICompileUnit to facilitate type uniquing.
Distinct DISubprograms (with isDefinition: true) are not part of the type
hierarchy and cannot be uniqued. This change removes the subprograms
list from DICompileUnit and instead adds a pointer to the owning compile
unit to distinct DISubprograms. This would make it easy for ThinLTO to
strip unneeded DISubprograms and their transitively referenced debug info.
Motivation
----------
Materializing DISubprograms is currently the most expensive operation when
doing a ThinLTO build of clang.
We want the DISubprogram to be stored in a separate Bitcode block (or the
same block as the function body) so we can avoid having to expensively
deserialize all DISubprograms together with the global metadata. If a
function has been inlined into another subprogram we need to store a
reference the block containing the inlined subprogram.
Attached to https://llvm.org/bugs/show_bug.cgi?id=27284 is a python script
that updates LLVM IR testcases to the new format.
http://reviews.llvm.org/D19034
<rdar://problem/25256815>
llvm-svn: 266446
diff --git a/llvm/lib/Transforms/Utils/CloneFunction.cpp b/llvm/lib/Transforms/Utils/CloneFunction.cpp
index cf39ae9..41d340b 100644
--- a/llvm/lib/Transforms/Utils/CloneFunction.cpp
+++ b/llvm/lib/Transforms/Utils/CloneFunction.cpp
@@ -172,52 +172,17 @@
TypeMapper, Materializer);
}
-// Find the MDNode which corresponds to the subprogram data that described F.
-static DISubprogram *FindSubprogram(const Function *F,
- DebugInfoFinder &Finder) {
- for (DISubprogram *Subprogram : Finder.subprograms()) {
- if (Subprogram->describes(F))
- return Subprogram;
- }
- return nullptr;
-}
-
-// Add an operand to an existing MDNode. The new operand will be added at the
-// back of the operand list.
-static void AddOperand(DICompileUnit *CU, DISubprogramArray SPs,
- Metadata *NewSP) {
- SmallVector<Metadata *, 16> NewSPs;
- NewSPs.reserve(SPs.size() + 1);
- for (auto *SP : SPs)
- NewSPs.push_back(SP);
- NewSPs.push_back(NewSP);
- CU->replaceSubprograms(MDTuple::get(CU->getContext(), NewSPs));
-}
-
// Clone the module-level debug info associated with OldFunc. The cloned data
// will point to NewFunc instead.
static void CloneDebugInfoMetadata(Function *NewFunc, const Function *OldFunc,
ValueToValueMapTy &VMap) {
- DebugInfoFinder Finder;
- Finder.processModule(*OldFunc->getParent());
-
- const DISubprogram *OldSubprogramMDNode = FindSubprogram(OldFunc, Finder);
- if (!OldSubprogramMDNode) return;
-
- auto *NewSubprogram =
- cast<DISubprogram>(MapMetadata(OldSubprogramMDNode, VMap));
- NewFunc->setSubprogram(NewSubprogram);
-
- for (auto *CU : Finder.compile_units()) {
- auto Subprograms = CU->getSubprograms();
- // If the compile unit's function list contains the old function, it should
- // also contain the new one.
- for (auto *SP : Subprograms) {
- if (SP == OldSubprogramMDNode) {
- AddOperand(CU, Subprograms, NewSubprogram);
- break;
- }
- }
+ if (const DISubprogram *OldSP = OldFunc->getSubprogram()) {
+ auto *NewSP = cast<DISubprogram>(MapMetadata(OldSP, VMap));
+ // FIXME: There ought to be a better way to do this: ValueMapper
+ // will clone the distinct DICompileUnit. Use the original one
+ // instead.
+ NewSP->replaceUnit(OldSP->getUnit());
+ NewFunc->setSubprogram(NewSP);
}
}