TTI: Use 0 for cost of fabs if free

[arsenm]

Summary

Ideally this would also happen for fneg, but that
isn't a distinct operation in the IR.

[arsenm]

ping

[hfinkel]

LGTM.

[arsenm]

r264368

include/llvm/CodeGen/BasicTTIImpl.h

case Intrinsic::masked_load:
       return static_cast<T *>(this)
           ->getMaskedMemoryOpCost(Instruction::Load, RetTy, 0, 0);
     }
 
     const TargetLoweringBase *TLI = getTLI();
     std::pair<unsigned, MVT> LT = TLI->getTypeLegalizationCost(DL, RetTy);
 
     if (TLI->isOperationLegalOrPromote(ISD, LT.second)) {
+      if (IID == Intrinsic::fabs &&
+          TLI->isFAbsFree(LT.second)) {
+        return 0;
+      }
+
       // The operation is legal. Assume it costs 1.
       // If the type is split to multiple registers, assume that there is some
       // overhead to this.
       // TODO: Once we have extract/insert subvector cost we need to use them.
       if (LT.first > 1)
         return LT.first * 2;
       return LT.first * 1;
     }

test/Analysis/CostModel/AMDGPU/fabs.ll

+; RUN: opt -cost-model -analyze -mtriple=amdgcn-unknown-amdhsa < %s | FileCheck %s
+
+; CHECK: 'fabs_f32'
+; CHECK: estimated cost of 0 for {{.*}} call float @llvm.fabs.f32
+define void @fabs_f32(float addrspace(1)* %out, float addrspace(1)* %vaddr) #0 {
+  %vec = load float, float addrspace(1)* %vaddr
+  %fabs = call float @llvm.fabs.f32(float %vec) #1
+  store float %fabs, float addrspace(1)* %out
+  ret void
+}
+
+; CHECK: 'fabs_v2f32'
+; CHECK: estimated cost of 2 for {{.*}} call <2 x float> @llvm.fabs.v2f32
+define void @fabs_v2f32(<2 x float> addrspace(1)* %out, <2 x float> addrspace(1)* %vaddr) #0 {
+  %vec = load <2 x float>, <2 x float> addrspace(1)* %vaddr
+  %fabs = call <2 x float> @llvm.fabs.v2f32(<2 x float> %vec) #1
+  store <2 x float> %fabs, <2 x float> addrspace(1)* %out
+  ret void
+}
+
+; CHECK: 'fabs_v3f32'
+; CHECK: estimated cost of 3 for {{.*}} call <3 x float> @llvm.fabs.v3f32
+define void @fabs_v3f32(<3 x float> addrspace(1)* %out, <3 x float> addrspace(1)* %vaddr) #0 {
+  %vec = load <3 x float>, <3 x float> addrspace(1)* %vaddr
+  %fabs = call <3 x float> @llvm.fabs.v3f32(<3 x float> %vec) #1
+  store <3 x float> %fabs, <3 x float> addrspace(1)* %out
+  ret void
+}
+
+; CHECK: 'fabs_f64'
+; CHECK: estimated cost of 0 for {{.*}} call double @llvm.fabs.f64
+define void @fabs_f64(double addrspace(1)* %out, double addrspace(1)* %vaddr) #0 {
+  %vec = load double, double addrspace(1)* %vaddr
+  %fabs = call double @llvm.fabs.f64(double %vec) #1
+  store double %fabs, double addrspace(1)* %out
+  ret void
+}
+
+; CHECK: 'fabs_v2f64'
+; CHECK: estimated cost of 2 for {{.*}} call <2 x double> @llvm.fabs.v2f64
+define void @fabs_v2f64(<2 x double> addrspace(1)* %out, <2 x double> addrspace(1)* %vaddr) #0 {
+  %vec = load <2 x double>, <2 x double> addrspace(1)* %vaddr
+  %fabs = call <2 x double> @llvm.fabs.v2f64(<2 x double> %vec) #1
+  store <2 x double> %fabs, <2 x double> addrspace(1)* %out
+  ret void
+}
+
+; CHECK: 'fabs_v3f64'
+; CHECK: estimated cost of 3 for {{.*}} call <3 x double> @llvm.fabs.v3f64
+define void @fabs_v3f64(<3 x double> addrspace(1)* %out, <3 x double> addrspace(1)* %vaddr) #0 {
+  %vec = load <3 x double>, <3 x double> addrspace(1)* %vaddr
+  %fabs = call <3 x double> @llvm.fabs.v3f64(<3 x double> %vec) #1
+  store <3 x double> %fabs, <3 x double> addrspace(1)* %out
+  ret void
+}
+
+; CHECK: 'fabs_f16'
+; CHECK: estimated cost of 0 for {{.*}} call half @llvm.fabs.f16
+define void @fabs_f16(half addrspace(1)* %out, half addrspace(1)* %vaddr) #0 {
+  %vec = load half, half addrspace(1)* %vaddr
+  %fabs = call half @llvm.fabs.f16(half %vec) #1
+  store half %fabs, half addrspace(1)* %out
+  ret void
+}
+
+; CHECK: 'fabs_v2f16'
+; CHECK: estimated cost of 0 for {{.*}} call <2 x half> @llvm.fabs.v2f16
+define void @fabs_v2f16(<2 x half> addrspace(1)* %out, <2 x half> addrspace(1)* %vaddr) #0 {
+  %vec = load <2 x half>, <2 x half> addrspace(1)* %vaddr
+  %fabs = call <2 x half> @llvm.fabs.v2f16(<2 x half> %vec) #1
+  store <2 x half> %fabs, <2 x half> addrspace(1)* %out
+  ret void
+}
+
+; CHECK: 'fabs_v3f16'
+; CHECK: estimated cost of 0 for {{.*}} call <3 x half> @llvm.fabs.v3f16
+define void @fabs_v3f16(<3 x half> addrspace(1)* %out, <3 x half> addrspace(1)* %vaddr) #0 {
+  %vec = load <3 x half>, <3 x half> addrspace(1)* %vaddr
+  %fabs = call <3 x half> @llvm.fabs.v3f16(<3 x half> %vec) #1
+  store <3 x half> %fabs, <3 x half> addrspace(1)* %out
+  ret void
+}
+
+declare float @llvm.fabs.f32(float) #1
+declare <2 x float> @llvm.fabs.v2f32(<2 x float>) #1
+declare <3 x float> @llvm.fabs.v3f32(<3 x float>) #1
+
+declare double @llvm.fabs.f64(double) #1
+declare <2 x double> @llvm.fabs.v2f64(<2 x double>) #1
+declare <3 x double> @llvm.fabs.v3f64(<3 x double>) #1
+
+declare half @llvm.fabs.f16(half) #1
+declare <2 x half> @llvm.fabs.v2f16(<2 x half>) #1
+declare <3 x half> @llvm.fabs.v3f16(<3 x half>) #1
+
+attributes #0 = { nounwind }
+attributes #1 = { nounwind readnone }