[OpenCL] Replace a CreatePointerCast call; NFC

[svenvh]

With opaque pointers, the only purpose of the cast here is to cast between address spaces, similar to the 4-argument case below.

[llvmbot]

@llvm/pr-subscribers-clang-codegen

@llvm/pr-subscribers-clang

Author: Sven van Haastregt (svenvh)

Changes

With opaque pointers, the only purpose of the cast here is to cast between address spaces, similar to the 4-argument case below.

---

Full diff: https://github.com/llvm/llvm-project/pull/112676.diff

1 Files Affected:

• (modified) clang/lib/CodeGen/CGBuiltin.cpp (+2-2)

diff --git a/clang/lib/CodeGen/CGBuiltin.cpp b/clang/lib/CodeGen/CGBuiltin.cpp
index f6d7db2c204c12..b2af4295fe99fe 100644
--- a/clang/lib/CodeGen/CGBuiltin.cpp
+++ b/clang/lib/CodeGen/CGBuiltin.cpp
@@ -5641,10 +5641,10 @@ RValue CodeGenFunction::EmitBuiltinExpr(const GlobalDecl GD, unsigned BuiltinID,
       llvm::Type *ArgTys[] = {Arg0->getType(), I8PTy, Int32Ty, Int32Ty};
       llvm::FunctionType *FTy = llvm::FunctionType::get(
           Int32Ty, llvm::ArrayRef<llvm::Type *>(ArgTys), false);
-      Value *BCast = Builder.CreatePointerCast(Arg1, I8PTy);
+      Value *ACast = Builder.CreateAddrSpaceCast(Arg1, I8PTy);
       return RValue::get(
           EmitRuntimeCall(CGM.CreateRuntimeFunction(FTy, Name),
-                          {Arg0, BCast, PacketSize, PacketAlign}));
+                          {Arg0, ACast, PacketSize, PacketAlign}));
     } else {
       assert(4 == E->getNumArgs() &&
              "Illegal number of parameters to pipe function");

[JOE1994]

IRBuilderBase:CreatePointerCast doesn't emit anything if the from and to targets types are same:

llvm-project/llvm/include/llvm/IR/IRBuilder.h

Lines 2197 to 2204 in 6d7712a

	Value *CreatePointerCast(Value *V, Type *DestTy,
	const Twine &Name = "") {
	if (V->getType() == DestTy)
	return V;
	if (auto *VC = dyn_cast<Constant>(V))
	return Insert(Folder.CreatePointerCast(VC, DestTy), Name);
	return Insert(CastInst::CreatePointerCast(V, DestTy), Name);
	}

while IRBuilderBase::CreateAddrSpaceCast emits addrspacecast regardless:

llvm-project/llvm/include/llvm/IR/IRBuilder.h

Lines 2159 to 2162 in 6d7712a

	Value *CreateAddrSpaceCast(Value *V, Type *DestTy,
	const Twine &Name = "") {
	return CreateCast(Instruction::AddrSpaceCast, V, DestTy, Name);
	}

LLVM LangRef says that from and to pointer types of addrspacecast needs to have different address spaces
(not sure if this is outdated info)

[JOE1994]

Oh.. CreateAddrSpaceCast calls CreateCast which also initially checks whether to and from types are identical before emitting anything.

llvm-project/llvm/include/llvm/IR/IRBuilder.h

Lines 2188 to 2195 in 6d7712a

	Value *CreateCast(Instruction::CastOps Op, Value *V, Type *DestTy,
	const Twine &Name = "") {
	if (V->getType() == DestTy)
	return V;
	if (Value *Folded = Folder.FoldCast(Op, V, DestTy))
	return Folded;
	return Insert(CastInst::Create(Op, V, DestTy), Name);
	}