TTI: Check legalization cost of abs nodes (#100523)

Author: arsenm

llvm/include/llvm/CodeGen/BasicTTIImpl.h

@@ -2120,20 +2120,9 @@ class BasicTTIImplBase : public TargetTransformInfoImplCRTPBase<T> {
     case Intrinsic::vector_reduce_fminimum:
       return thisT()->getMinMaxReductionCost(getMinMaxReductionIntrinsicOp(IID),
                                              VecOpTy, ICA.getFlags(), CostKind);
-    case Intrinsic::abs: {
-      // abs(X) = select(icmp(X,0),X,sub(0,X))
-      Type *CondTy = RetTy->getWithNewBitWidth(1);
-      CmpInst::Predicate Pred = CmpInst::ICMP_SGT;
-      InstructionCost Cost = 0;
-      Cost += thisT()->getCmpSelInstrCost(BinaryOperator::ICmp, RetTy, CondTy,
-                                          Pred, CostKind);
-      Cost += thisT()->getCmpSelInstrCost(BinaryOperator::Select, RetTy, CondTy,
-                                          Pred, CostKind);
-      // TODO: Should we add an OperandValueProperties::OP_Zero property?
-      Cost += thisT()->getArithmeticInstrCost(
-         BinaryOperator::Sub, RetTy, CostKind, {TTI::OK_UniformConstantValue, TTI::OP_None});
-      return Cost;
-    }
+    case Intrinsic::abs:
+      ISD = ISD::ABS;
+      break;
     case Intrinsic::smax:
       ISD = ISD::SMAX;
       break;
@@ -2402,6 +2391,21 @@ class BasicTTIImplBase : public TargetTransformInfoImplCRTPBase<T> {
       Cost += thisT()->getArithmeticInstrCost(Instruction::Or, RetTy, CostKind);
       return Cost;
     }
+    case Intrinsic::abs: {
+      // abs(X) = select(icmp(X,0),X,sub(0,X))
+      Type *CondTy = RetTy->getWithNewBitWidth(1);
+      CmpInst::Predicate Pred = CmpInst::ICMP_SGT;
+      InstructionCost Cost = 0;
+      Cost += thisT()->getCmpSelInstrCost(BinaryOperator::ICmp, RetTy, CondTy,
+                                          Pred, CostKind);
+      Cost += thisT()->getCmpSelInstrCost(BinaryOperator::Select, RetTy, CondTy,
+                                          Pred, CostKind);
+      // TODO: Should we add an OperandValueProperties::OP_Zero property?
+      Cost += thisT()->getArithmeticInstrCost(
+          BinaryOperator::Sub, RetTy, CostKind,
+          {TTI::OK_UniformConstantValue, TTI::OP_None});
+      return Cost;
+    }
     case Intrinsic::fptosi_sat:
     case Intrinsic::fptoui_sat: {
       if (Tys.empty())

llvm/lib/Target/AMDGPU/AMDGPUTargetTransformInfo.cpp

@@ -696,6 +696,7 @@ static bool intrinsicHasPackedVectorBenefit(Intrinsic::ID ID) {
   case Intrinsic::usub_sat:
   case Intrinsic::sadd_sat:
   case Intrinsic::ssub_sat:
+  case Intrinsic::abs:
     return true;
   default:
     return false;
@@ -724,7 +725,7 @@ GCNTTIImpl::getIntrinsicInstrCost(const IntrinsicCostAttributes &ICA,
   if (SLT == MVT::f64)
     return LT.first * NElts * get64BitInstrCost(CostKind);
 
-  if ((ST->has16BitInsts() && SLT == MVT::f16) ||
+  if ((ST->has16BitInsts() && (SLT == MVT::f16 || SLT == MVT::i16)) ||
       (ST->hasPackedFP32Ops() && SLT == MVT::f32))
     NElts = (NElts + 1) / 2;
 
@@ -752,11 +753,17 @@ GCNTTIImpl::getIntrinsicInstrCost(const IntrinsicCostAttributes &ICA,
   case Intrinsic::usub_sat:
   case Intrinsic::sadd_sat:
   case Intrinsic::ssub_sat: {
+    // TODO: Full rate for i32/i16
     static const auto ValidSatTys = {MVT::v2i16, MVT::v4i16};
     if (any_of(ValidSatTys, [&LT](MVT M) { return M == LT.second; }))
       NElts = 1;
     break;
   }
+  case Intrinsic::abs:
+    // Expansion takes 2 instructions for VALU
+    if (SLT == MVT::i16 || SLT == MVT::i32)
+      InstRate = 2 * getFullRateInstrCost();
+    break;
   default:
     break;
   }