DAGCombiner: Allow the DAGCombiner to combine multiple FDIVs with the same divisor info FMULs by the reciprocal.

E.g., ( a / D; b / D ) -> ( recip = 1.0 / D; a * recip; b * recip)

A hook is added to allow the target to control whether it needs to do such combine.

Reviewed in http://reviews.llvm.org/D6334

llvm-svn: 222510

2 files changed, 7 insertions, 0 deletions

diff --git a/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp b/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
index 7c94d831cba..70cf7599a39 100644
--- a/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
+++ b/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
@@ -8732,6 +8732,12 @@ bool AArch64TargetLowering::useLoadStackGuardNode() const {
   return true;
 }
 
+bool AArch64TargetLowering::combineRepeatedFPDivisors(unsigned NumUsers) const {
+  // Combine multiple FDIVs with the same divisor into multiple FMULs by the
+  // reciprocal if there are three or more FDIVs.
+  return NumUsers > 2;
+}
+
 TargetLoweringBase::LegalizeTypeAction
 AArch64TargetLowering::getPreferredVectorAction(EVT VT) const {
   MVT SVT = VT.getSimpleVT();
diff --git a/llvm/lib/Target/AArch64/AArch64ISelLowering.h b/llvm/lib/Target/AArch64/AArch64ISelLowering.h
index 2f5708dd897..c76f6a865dc 100644
--- a/llvm/lib/Target/AArch64/AArch64ISelLowering.h
+++ b/llvm/lib/Target/AArch64/AArch64ISelLowering.h
@@ -440,6 +440,7 @@ private:
 
   SDValue BuildSDIVPow2(SDNode *N, const APInt &Divisor, SelectionDAG &DAG,
                         std::vector<SDNode *> *Created) const override;
+  bool combineRepeatedFPDivisors(unsigned NumUsers) const override;
 
   ConstraintType
   getConstraintType(const std::string &Constraint) const override;