[clang] [CIR][AMDGPU] Use nsw add and ordered compare in logb lowering (PR #228004)

[Arseniy Obolenskiy via cfe-commits]

https://github.com/aobolensk created https://github.com/llvm/llvm-project/pull/228004

Align with classic codegen, which emits add nsw and fcmp one

>From 33d26b692626fe810786ff1d76d19c272a7c3cc0 Mon Sep 17 00:00:00 2001
From: Arseniy Obolenskiy <arseniy.obolenskiy at amd.com>
Date: Thu, 1 Oct 2026 11:11:14 +0200
Subject: [PATCH] [CIR][AMDGPU] Use nsw add and ordered compare in logb
 lowering

Align with classic codegen, which emits add nsw and fcmp one
---
 clang/lib/CIR/CodeGen/CIRGenBuiltinAMDGPU.cpp             | 4 ++--
 clang/test/CIR/CodeGenHIP/builtins-amdgcn-logb-scalbn.hip | 4 ++++
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/clang/lib/CIR/CodeGen/CIRGenBuiltinAMDGPU.cpp b/clang/lib/CIR/CodeGen/CIRGenBuiltinAMDGPU.cpp
index b2aac0d376fa1..e0fc28f278d1b 100644
--- a/clang/lib/CIR/CodeGen/CIRGenBuiltinAMDGPU.cpp
+++ b/clang/lib/CIR/CodeGen/CIRGenBuiltinAMDGPU.cpp
@@ -89,7 +89,7 @@ static mlir::Value emitLogbBuiltin(CIRGenFunction &cgf, const CallExpr *e,
 
   mlir::Value negativeOne =
       builder.getConstant(loc, cir::IntAttr::get(int32Ty, -1));
-  mlir::Value expMinus1 = builder.createAdd(loc, exp, negativeOne);
+  mlir::Value expMinus1 = builder.createNSWAdd(loc, exp, negativeOne);
 
   mlir::Value siToFp = cir::CastOp::create(
       builder, loc, srcTy, cir::CastKind::int_to_float, expMinus1);
@@ -100,7 +100,7 @@ static mlir::Value emitLogbBuiltin(CIRGenFunction &cgf, const CallExpr *e,
   mlir::Value inf = builder.getConstant(loc, cir::FPAttr::get(srcTy, infVal));
 
   mlir::Value fabsNegInf =
-      builder.createCompare(loc, cir::CmpOpKind::ne, fabs, inf);
+      builder.createCompare(loc, cir::CmpOpKind::one, fabs, inf);
 
   mlir::Value sel = builder.createSelect(loc, fabsNegInf, siToFp, fabs);
 
diff --git a/clang/test/CIR/CodeGenHIP/builtins-amdgcn-logb-scalbn.hip b/clang/test/CIR/CodeGenHIP/builtins-amdgcn-logb-scalbn.hip
index b4d28a8bb7487..d5f31ff5cf019 100644
--- a/clang/test/CIR/CodeGenHIP/builtins-amdgcn-logb-scalbn.hip
+++ b/clang/test/CIR/CodeGenHIP/builtins-amdgcn-logb-scalbn.hip
@@ -17,6 +17,8 @@
 // CIR: cir.call_llvm_intrinsic "frexp" {{.*}} : (!cir.float) -> {{.*}}
 // LLVM: define{{.*}} float @_Z11test_logbfff(
 // LLVM: call { float, i32 } @llvm.frexp.f32.i32(float {{.*}})
+// LLVM: add nsw i32 %{{.*}}, -1
+// LLVM: fcmp{{.*}} one float %{{.*}}, +inf
 __device__ float test_logbff(float a) {
   return __builtin_logbf(a);
 }
@@ -25,6 +27,8 @@ __device__ float test_logbff(float a) {
 // CIR: cir.call_llvm_intrinsic "frexp" {{.*}} : (!cir.double) -> {{.*}}
 // LLVM: define{{.*}} double @_Z11test_logbddd(
 // LLVM: call { double, i32 } @llvm.frexp.f64.i32(double {{.*}})
+// LLVM: add nsw i32 %{{.*}}, -1
+// LLVM: fcmp{{.*}} one double %{{.*}}, +inf
 __device__ double test_logbdd(double a) {
   return __builtin_logb(a);
 }