[llvm] AMDGPU: Replace unused update.dpp inputs with poison instead of undef (PR #131287)

[Matt Arsenault via llvm-commits]

https://github.com/arsenm updated https://github.com/llvm/llvm-project/pull/131287

>From cbc0b7081b6d92735cd2d2812f3d40382b066101 Mon Sep 17 00:00:00 2001
From: Matt Arsenault <Matthew.Arsenault at amd.com>
Date: Fri, 14 Mar 2025 14:10:30 +0700
Subject: [PATCH] AMDGPU: Replace unused update.dpp inputs with poison instead
 of undef

---
 llvm/lib/Target/AMDGPU/AMDGPUInstCombineIntrinsic.cpp        | 4 ++--
 llvm/test/Transforms/InstCombine/AMDGPU/amdgcn-intrinsics.ll | 4 ++--
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/llvm/lib/Target/AMDGPU/AMDGPUInstCombineIntrinsic.cpp b/llvm/lib/Target/AMDGPU/AMDGPUInstCombineIntrinsic.cpp
index be1274e181ce2..26c48c19ebfd8 100644
--- a/llvm/lib/Target/AMDGPU/AMDGPUInstCombineIntrinsic.cpp
+++ b/llvm/lib/Target/AMDGPU/AMDGPUInstCombineIntrinsic.cpp
@@ -1103,11 +1103,11 @@ GCNTTIImpl::instCombineIntrinsic(InstCombiner &IC, IntrinsicInst &II) const {
     auto *RM = cast<ConstantInt>(II.getArgOperand(3));
     auto *BM = cast<ConstantInt>(II.getArgOperand(4));
     if (BC->isZeroValue() || RM->getZExtValue() != 0xF ||
-        BM->getZExtValue() != 0xF || isa<UndefValue>(Old))
+        BM->getZExtValue() != 0xF || isa<PoisonValue>(Old))
       break;
 
     // If bound_ctrl = 1, row mask = bank mask = 0xf we can omit old value.
-    return IC.replaceOperand(II, 0, UndefValue::get(Old->getType()));
+    return IC.replaceOperand(II, 0, PoisonValue::get(Old->getType()));
   }
   case Intrinsic::amdgcn_permlane16:
   case Intrinsic::amdgcn_permlane16_var:
diff --git a/llvm/test/Transforms/InstCombine/AMDGPU/amdgcn-intrinsics.ll b/llvm/test/Transforms/InstCombine/AMDGPU/amdgcn-intrinsics.ll
index 9a42fa723dc48..3e30b2a5b0911 100644
--- a/llvm/test/Transforms/InstCombine/AMDGPU/amdgcn-intrinsics.ll
+++ b/llvm/test/Transforms/InstCombine/AMDGPU/amdgcn-intrinsics.ll
@@ -3232,7 +3232,7 @@ define amdgpu_kernel void @update_dpp_no_combine(ptr addrspace(1) %out, i32 %in1
 
 define amdgpu_kernel void @update_dpp_drop_old(ptr addrspace(1) %out, i32 %in1, i32 %in2) {
 ; CHECK-LABEL: @update_dpp_drop_old(
-; CHECK-NEXT:    [[TMP0:%.*]] = call i32 @llvm.amdgcn.update.dpp.i32(i32 undef, i32 [[IN2:%.*]], i32 3, i32 15, i32 15, i1 true)
+; CHECK-NEXT:    [[TMP0:%.*]] = call i32 @llvm.amdgcn.update.dpp.i32(i32 poison, i32 [[IN2:%.*]], i32 3, i32 15, i32 15, i1 true)
 ; CHECK-NEXT:    store i32 [[TMP0]], ptr addrspace(1) [[OUT:%.*]], align 4
 ; CHECK-NEXT:    ret void
 ;
@@ -3243,7 +3243,7 @@ define amdgpu_kernel void @update_dpp_drop_old(ptr addrspace(1) %out, i32 %in1,
 
 define amdgpu_kernel void @update_dpp_undef_old(ptr addrspace(1) %out, i32 %in1) {
 ; CHECK-LABEL: @update_dpp_undef_old(
-; CHECK-NEXT:    [[TMP0:%.*]] = call i32 @llvm.amdgcn.update.dpp.i32(i32 undef, i32 [[IN1:%.*]], i32 4, i32 15, i32 15, i1 true)
+; CHECK-NEXT:    [[TMP0:%.*]] = call i32 @llvm.amdgcn.update.dpp.i32(i32 poison, i32 [[IN1:%.*]], i32 4, i32 15, i32 15, i1 true)
 ; CHECK-NEXT:    store i32 [[TMP0]], ptr addrspace(1) [[OUT:%.*]], align 4
 ; CHECK-NEXT:    ret void
 ;