From 8b36ac818cd58751e7327b093eda746ea4355ca5 Mon Sep 17 00:00:00 2001
From: John McCall <rjmccall@apple.com>
Date: Wed, 10 Apr 2019 17:03:09 +0000
Subject: Don't emit an unreachable return block.

Patch by Brad Moody.

llvm-svn: 358104
---
 clang/lib/CodeGen/CodeGenFunction.cpp | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

(limited to 'clang/lib/CodeGen/CodeGenFunction.cpp')

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
-- 
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