[CloneFunction][DebugInfo] Avoid cloning DILexicalBlocks of inlined subprograms

If DISubpogram was not cloned (e.g. we are cloning a function that has other
functions inlined into it, and subprograms of the inlined functions are
not supposed to be cloned), it doesn't make sense to clone its DILexicalBlocks
as well. Otherwise we'll get duplicated DILexicalBlocks that may confuse
debug info emission in AsmPrinter.

I believe it also makes no sense cloning any DILocalVariables or maybe
other local entities, if their parent subprogram was not cloned, cause
they will be dangling and will not participate in futher emission.

Reviewed By: aprantl

Differential Revision: https://reviews.llvm.org/D127102

1 files changed, 13 insertions, 2 deletions

diff --git a/llvm/lib/Transforms/Utils/CloneFunction.cpp b/llvm/lib/Transforms/Utils/CloneFunction.cpp
index 8f053cd5..e737a594 100644
--- a/llvm/lib/Transforms/Utils/CloneFunction.cpp
+++ b/llvm/lib/Transforms/Utils/CloneFunction.cpp
@@ -206,9 +206,20 @@ void llvm::CloneFunctionInto(Function *NewFunc, const Function *OldFunc,
     };
 
     // Avoid cloning types, compile units, and (other) subprograms.
-    for (DISubprogram *ISP : DIFinder->subprograms())
-      if (ISP != SPClonedWithinModule)
+    SmallPtrSet<const DISubprogram *, 16> MappedToSelfSPs;
+    for (DISubprogram *ISP : DIFinder->subprograms()) {
+      if (ISP != SPClonedWithinModule) {
         mapToSelfIfNew(ISP);
+        MappedToSelfSPs.insert(ISP);
+      }
+    }
+
+    // If a subprogram isn't going to be cloned skip its lexical blocks as well.
+    for (DIScope *S : DIFinder->scopes()) {
+      auto *LScope = dyn_cast<DILocalScope>(S);
+      if (LScope && MappedToSelfSPs.count(LScope->getSubprogram()))
+        mapToSelfIfNew(S);
+    }
 
     for (DICompileUnit *CU : DIFinder->compile_units())
       mapToSelfIfNew(CU);