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move combineRepeatedFPDivisors logic into a helper function; NFCI

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@243293 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Sanjay Patel 2015-07-27 17:58:49 +00:00
parent 6c304ebd8a
commit 5834764c65
1 changed files with 57 additions and 42 deletions
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99
lib/CodeGen/SelectionDAG/DAGCombiner.cpp
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@ -338,6 +338,7 @@ namespace {
unsigned HiOp);
SDValue CombineConsecutiveLoads(SDNode *N, EVT VT);
SDValue CombineExtLoad(SDNode *N);
SDValue combineRepeatedFPDivisors(SDNode *N);
SDValue ConstantFoldBITCASTofBUILD_VECTOR(SDNode *, EVT);
SDValue BuildSDIV(SDNode *N);
SDValue BuildSDIVPow2(SDNode *N);
@ -8235,6 +8236,60 @@ SDValue DAGCombiner::visitFMA(SDNode *N) {
return SDValue();
}
// Combine multiple FDIVs with the same divisor into multiple FMULs by the
// reciprocal.
// E.g., (a / D; b / D;) -> (recip = 1.0 / D; a * recip; b * recip)
// Notice that this is not always beneficial. One reason is different target
// may have different costs for FDIV and FMUL, so sometimes the cost of two
// FDIVs may be lower than the cost of one FDIV and two FMULs. Another reason
// is the critical path is increased from "one FDIV" to "one FDIV + one FMUL".
SDValue DAGCombiner::combineRepeatedFPDivisors(SDNode *N) {
if (!DAG.getTarget().Options.UnsafeFPMath)
return SDValue();
SDValue N0 = N->getOperand(0);
ConstantFPSDNode *N0CFP = dyn_cast<ConstantFPSDNode>(N0);
// Skip if current node is a reciprocal.
if (N0CFP && N0CFP->isExactlyValue(1.0))
return SDValue();
SDValue N1 = N->getOperand(1);
SmallVector<SDNode *, 4> Users;
// Find all FDIV users of the same divisor.
for (auto *U : N1->uses()) {
if (U->getOpcode() == ISD::FDIV && U->getOperand(1) == N1)
Users.push_back(U);
}
if (!TLI.combineRepeatedFPDivisors(Users.size()))
return SDValue();
EVT VT = N->getValueType(0);
SDLoc DL(N);
SDValue FPOne = DAG.getConstantFP(1.0, DL, VT);
// FIXME: This optimization requires some level of fast-math, so the
// created reciprocal node should at least have the 'allowReciprocal'
// fast-math-flag set.
SDValue Reciprocal = DAG.getNode(ISD::FDIV, DL, VT, FPOne, N1);
// Dividend / Divisor -> Dividend * Reciprocal
for (auto *U : Users) {
SDValue Dividend = U->getOperand(0);
if (Dividend != FPOne) {
SDValue NewNode = DAG.getNode(ISD::FMUL, SDLoc(U), VT, Dividend,
Reciprocal);
CombineTo(U, NewNode);
} else if (U != Reciprocal.getNode()) {
// In the absence of fast-math-flags, this user node is always the
// same node as Reciprocal, but with FMF they may be different nodes.
CombineTo(U, Reciprocal);
}
}
return SDValue(N, 0); // N was replaced.
}
SDValue DAGCombiner::visitFDIV(SDNode *N) {
SDValue N0 = N->getOperand(0);
SDValue N1 = N->getOperand(1);
@ -8335,48 +8390,8 @@ SDValue DAGCombiner::visitFDIV(SDNode *N) {
}
}
// Combine multiple FDIVs with the same divisor into multiple FMULs by the
// reciprocal.
// E.g., (a / D; b / D;) -> (recip = 1.0 / D; a * recip; b * recip)
// Notice that this is not always beneficial. One reason is different target
// may have different costs for FDIV and FMUL, so sometimes the cost of two
// FDIVs may be lower than the cost of one FDIV and two FMULs. Another reason
// is the critical path is increased from "one FDIV" to "one FDIV + one FMUL".
if (Options.UnsafeFPMath) {
// Skip if current node is a reciprocal.
if (N0CFP && N0CFP->isExactlyValue(1.0))
return SDValue();
SmallVector<SDNode *, 4> Users;
// Find all FDIV users of the same divisor.
for (auto *U : N1->uses()) {
if (U->getOpcode() == ISD::FDIV && U->getOperand(1) == N1)
Users.push_back(U);
}
if (TLI.combineRepeatedFPDivisors(Users.size())) {
SDValue FPOne = DAG.getConstantFP(1.0, DL, VT);
// FIXME: This optimization requires some level of fast-math, so the
// created reciprocal node should at least have the 'allowReciprocal'
// fast-math-flag set.
SDValue Reciprocal = DAG.getNode(ISD::FDIV, DL, VT, FPOne, N1);
// Dividend / Divisor -> Dividend * Reciprocal
for (auto *U : Users) {
SDValue Dividend = U->getOperand(0);
if (Dividend != FPOne) {
SDValue NewNode = DAG.getNode(ISD::FMUL, SDLoc(U), VT, Dividend,
Reciprocal);
CombineTo(U, NewNode);
} else if (U != Reciprocal.getNode()) {
// In the absence of fast-math-flags, this user node is always the
// same node as Reciprocal, but with FMF they may be different nodes.
CombineTo(U, Reciprocal);
}
}
return SDValue(N, 0); // N was replaced.
}
}
if (SDValue CombineRepeatedDivisors = combineRepeatedFPDivisors(N))
return CombineRepeatedDivisors;
return SDValue();
}