[llvm] [AMDGPU] Only set Info.memVT when not later overridden (PR #92670)

[Jessica Clarke via llvm-commits]

https://github.com/jrtc27 created https://github.com/llvm/llvm-project/pull/92670

For the amdgcn_*_buffer_load_lds intrinsics this field is later overriden, so avoid pointlessly calling MVT::getVT in that case. Importantly, this is also the only case I can find in tree where a PointerType is passed to MVT::getVT, so this will allow us to forbid doing so in future, keeping MVT::iPTR as originating solely from TableGen as was claimed next to its definition in MachineValueType.h (but lost in the autogeneration conversion).

>From 20b5ad9f94db4456953abb21b63b0fa9cf3e4e1c Mon Sep 17 00:00:00 2001
From: Jessica Clarke <jrtc27 at jrtc27.com>
Date: Sat, 18 May 2024 21:08:52 +0100
Subject: [PATCH] [AMDGPU] Only set Info.memVT when not later overridden

For the amdgcn_*_buffer_load_lds intrinsics this field is later
overriden, so avoid pointlessly calling MVT::getVT in that case.
Importantly, this is also the only case I can find in tree where a
PointerType is passed to MVT::getVT, so this will allow us to forbid
doing so in future, keeping MVT::iPTR as originating solely from
TableGen as was claimed next to its definition in MachineValueType.h
(but lost in the autogeneration conversion).
---
 llvm/lib/Target/AMDGPU/SIISelLowering.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/llvm/lib/Target/AMDGPU/SIISelLowering.cpp b/llvm/lib/Target/AMDGPU/SIISelLowering.cpp
index 89e83babcfef4..801ab4b65cbc0 100644
--- a/llvm/lib/Target/AMDGPU/SIISelLowering.cpp
+++ b/llvm/lib/Target/AMDGPU/SIISelLowering.cpp
@@ -1233,13 +1233,13 @@ bool SITargetLowering::getTgtMemIntrinsic(IntrinsicInfo &Info,
       // Atomic
       Info.opc = CI.getType()->isVoidTy() ? ISD::INTRINSIC_VOID :
                                             ISD::INTRINSIC_W_CHAIN;
-      Info.memVT = MVT::getVT(CI.getArgOperand(0)->getType());
       Info.flags |= MachineMemOperand::MOLoad |
                     MachineMemOperand::MOStore |
                     MachineMemOperand::MODereferenceable;
 
       switch (IntrID) {
       default:
+        Info.memVT = MVT::getVT(CI.getArgOperand(0)->getType());
         // XXX - Should this be volatile without known ordering?
         Info.flags |= MachineMemOperand::MOVolatile;
         break;