Don't emit an unreachable return block.

Patch by Brad Moody.

llvm-svn: 358104

2 files changed, 15 insertions, 9 deletions

diff --git a/clang/lib/CodeGen/CGCall.cpp b/clang/lib/CodeGen/CGCall.cpp
index aa52e1e7c51..93421903a09 100644
--- a/clang/lib/CodeGen/CGCall.cpp
+++ b/clang/lib/CodeGen/CGCall.cpp
@@ -2873,15 +2873,6 @@ void CodeGenFunction::EmitFunctionEpilog(const CGFunctionInfo &FI,
         RV = SI->getValueOperand();
         SI->eraseFromParent();
 
-        // If that was the only use of the return value, nuke it as well now.
-        auto returnValueInst = ReturnValue.getPointer();
-        if (returnValueInst->use_empty()) {
-          if (auto alloca = dyn_cast<llvm::AllocaInst>(returnValueInst)) {
-            alloca->eraseFromParent();
-            ReturnValue = Address::invalid();
-          }
-        }
-
       // Otherwise, we have to do a simple load.
       } else {
         RV = Builder.CreateLoad(ReturnValue);
diff --git a/clang/lib/CodeGen/CodeGenFunction.cpp b/clang/lib/CodeGen/CodeGenFunction.cpp
index 5b2d043a0a4..7a8d79ba3b5 100644
--- a/clang/lib/CodeGen/CodeGenFunction.cpp
+++ b/clang/lib/CodeGen/CodeGenFunction.cpp
@@ -255,6 +255,7 @@ llvm::DebugLoc CodeGenFunction::EmitReturnBlock() {
     if (CurBB->empty() || ReturnBlock.getBlock()->use_empty()) {
       ReturnBlock.getBlock()->replaceAllUsesWith(CurBB);
       delete ReturnBlock.getBlock();
+      ReturnBlock = JumpDest();
     } else
       EmitBlock(ReturnBlock.getBlock());
     return llvm::DebugLoc();
@@ -274,6 +275,7 @@ llvm::DebugLoc CodeGenFunction::EmitReturnBlock() {
       Builder.SetInsertPoint(BI->getParent());
       BI->eraseFromParent();
       delete ReturnBlock.getBlock();
+      ReturnBlock = JumpDest();
       return Loc;
     }
   }
@@ -448,6 +450,19 @@ void CodeGenFunction::FinishFunction(SourceLocation EndLoc) {
   // 5. Width of vector aguments and return types for functions called by this
   //    function.
   CurFn->addFnAttr("min-legal-vector-width", llvm::utostr(LargestVectorWidth));
+
+  // If we generated an unreachable return block, delete it now.
+  if (ReturnBlock.isValid() && ReturnBlock.getBlock()->use_empty()) {
+    Builder.ClearInsertionPoint();
+    ReturnBlock.getBlock()->eraseFromParent();
+  }
+  if (ReturnValue.isValid()) {
+    auto *RetAlloca = dyn_cast<llvm::AllocaInst>(ReturnValue.getPointer());
+    if (RetAlloca && RetAlloca->use_empty()) {
+      RetAlloca->eraseFromParent();
+      ReturnValue = Address::invalid();
+    }
+  }
 }
 
 /// ShouldInstrumentFunction - Return true if the current function should be