TTI: Estimate @llvm.fmuladd cost as fmul + fadd when FMA's aren't legal on the target.

llvm-svn: 208115

1 files changed, 7 insertions, 1 deletions

diff --git a/llvm/lib/CodeGen/BasicTargetTransformInfo.cpp b/llvm/lib/CodeGen/BasicTargetTransformInfo.cpp
index 6ad1f28bb25..4b895092d3b 100644
--- a/llvm/lib/CodeGen/BasicTargetTransformInfo.cpp
+++ b/llvm/lib/CodeGen/BasicTargetTransformInfo.cpp
@@ -487,7 +487,7 @@ unsigned BasicTTI::getIntrinsicInstrCost(Intrinsic::ID IID, Type *RetTy,
   case Intrinsic::round:   ISD = ISD::FROUND; break;
   case Intrinsic::pow:     ISD = ISD::FPOW;   break;
   case Intrinsic::fma:     ISD = ISD::FMA;    break;
-  case Intrinsic::fmuladd: ISD = ISD::FMA;    break; // FIXME: mul + add?
+  case Intrinsic::fmuladd: ISD = ISD::FMA;    break;
   case Intrinsic::lifetime_start:
   case Intrinsic::lifetime_end:
     return 0;
@@ -512,6 +512,12 @@ unsigned BasicTTI::getIntrinsicInstrCost(Intrinsic::ID IID, Type *RetTy,
     return LT.first * 2;
   }
 
+  // If we can't lower fmuladd into an FMA estimate the cost as a floating
+  // point mul followed by an add.
+  if (IID == Intrinsic::fmuladd)
+    return TopTTI->getArithmeticInstrCost(BinaryOperator::FMul, RetTy) +
+           TopTTI->getArithmeticInstrCost(BinaryOperator::FAdd, RetTy);
+
   // Else, assume that we need to scalarize this intrinsic. For math builtins
   // this will emit a costly libcall, adding call overhead and spills. Make it
   // very expensive.