Make GV removal more robust add opt dxil-op-lower test

Author: Greg Roth

llvm/lib/Target/DirectX/DXILOpLowering.cpp

@@ -209,12 +209,13 @@ class OpLowerer {
   void removeResourceGlobals(CallInst *CI) {
     for (User *User : make_early_inc_range(CI->users())) {
       if(StoreInst *Store = dyn_cast<StoreInst>(User)) {
-	if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Store->getOperand(1))) {
-	  Store->eraseFromParent();
-	  assert(GV->use_empty() && "Buffer global still has users");
-	  GV->removeDeadConstantUsers();
-	  GV->eraseFromParent();
-	}
+	Value *V = Store->getOperand(1);
+	Store->eraseFromParent();
+	if (GlobalVariable *GV = dyn_cast<GlobalVariable>(V))
+	  if(GV->use_empty()) {
+	    GV->removeDeadConstantUsers();
+	    GV->eraseFromParent();
+	  }
       }
     }
   }

llvm/test/CodeGen/DirectX/ResourceGlobalElimination.ll

@@ -1,6 +1,7 @@
 ; RUN: opt -S -passes='early-cse<memssa>' %s -o %t
 ; RUN: FileCheck --check-prefixes=CSE,CHECK %s < %t
 ; finish compiling to verify that dxil-op-lower removes the globals entirely
+; RUN: opt -S -dxil-op-lower %t -o - | FileCheck --check-prefixes=LLC,CHECK %s
 ; RUN: llc -mtriple=dxil-pc-shadermodel6.0-compute  --filetype=asm -o - %t | FileCheck --check-prefixes=LLC,CHECK %s
 ; RUN: llc -mtriple=dxil-pc-shadermodel6.6-compute  --filetype=asm -o - %t | FileCheck --check-prefixes=LLC,CHECK %s