[MS] Fix crash involving gnu stmt exprs and inalloca

Use a WeakTrackingVH to cope with the stmt emission logic that cleans up
unreachable blocks. This invalidates the reference to the deferred
replacement placeholder. Cope with it.

Fixes PR25102 (from 2015!)

1 files changed, 6 insertions, 6 deletions

diff --git a/clang/lib/CodeGen/CodeGenFunction.cpp b/clang/lib/CodeGen/CodeGenFunction.cpp
index 6d95adc..53bf69f 100644
--- a/clang/lib/CodeGen/CodeGenFunction.cpp
+++ b/clang/lib/CodeGen/CodeGenFunction.cpp
@@ -452,13 +452,13 @@ void CodeGenFunction::FinishFunction(SourceLocation EndLoc) {
   if (CGM.getCodeGenOpts().EmitDeclMetadata)
     EmitDeclMetadata();
 
-  for (SmallVectorImpl<std::pair<llvm::Instruction *, llvm::Value *> >::iterator
-           I = DeferredReplacements.begin(),
-           E = DeferredReplacements.end();
-       I != E; ++I) {
-    I->first->replaceAllUsesWith(I->second);
-    I->first->eraseFromParent();
+  for (const auto &R : DeferredReplacements) {
+    if (llvm::Value *Old = R.first) {
+      Old->replaceAllUsesWith(R.second);
+      cast<llvm::Instruction>(Old)->eraseFromParent();
+    }
   }
+  DeferredReplacements.clear();
 
   // Eliminate CleanupDestSlot alloca by replacing it with SSA values and
   // PHIs if the current function is a coroutine. We don't do it for all