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[DAGCombiner] Split SDIV/UDIV optimization expansions from the rest of the combines. NFCI. 

As suggested by @efriedma on D48975, this patch separates the BuildDiv/Pow2 style optimizations from the rest of the visitSDIV/visitUDIV to make it easier to reuse the combines and will allow us to avoid some rather nasty node recursive combining in visitREM.

llvm-svn: 336656
This commit is contained in:
Simon Pilgrim 2018-07-10 11:38:00 +00:00
parent 006bffe25a
commit ce5c19b623
1 changed files with 44 additions and 15 deletions
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59
llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
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@ -298,7 +298,9 @@ namespace {
SDValue visitMUL(SDNode *N);
SDValue useDivRem(SDNode *N);
SDValue visitSDIV(SDNode *N);
SDValue visitSDIVLike(SDValue N0, SDValue N1, SDNode *N);
SDValue visitUDIV(SDNode *N);
SDValue visitUDIVLike(SDValue N0, SDValue N1, SDNode *N);
SDValue visitREM(SDNode *N);
SDValue visitMULHU(SDNode *N);
SDValue visitMULHS(SDNode *N);
@ -3010,7 +3012,6 @@ SDValue DAGCombiner::visitSDIV(SDNode *N) {
SDValue N1 = N->getOperand(1);
EVT VT = N->getValueType(0);
EVT CCVT = getSetCCResultType(VT);
unsigned BitWidth = VT.getScalarSizeInBits();
// fold vector ops
if (VT.isVector())
@ -3047,6 +3048,28 @@ SDValue DAGCombiner::visitSDIV(SDNode *N) {
if (DAG.SignBitIsZero(N1) && DAG.SignBitIsZero(N0))
return DAG.getNode(ISD::UDIV, DL, N1.getValueType(), N0, N1);
if (SDValue V = visitSDIVLike(N0, N1, N))
return V;
// sdiv, srem -> sdivrem
// If the divisor is constant, then return DIVREM only if isIntDivCheap() is
// true. Otherwise, we break the simplification logic in visitREM().
AttributeList Attr = DAG.getMachineFunction().getFunction().getAttributes();
if (!N1C || TLI.isIntDivCheap(N->getValueType(0), Attr))
if (SDValue DivRem = useDivRem(N))
return DivRem;
return SDValue();
}
SDValue DAGCombiner::visitSDIVLike(SDValue N0, SDValue N1, SDNode *N) {
SDLoc DL(N);
EVT VT = N->getValueType(0);
EVT CCVT = getSetCCResultType(VT);
unsigned BitWidth = VT.getScalarSizeInBits();
ConstantSDNode *N1C = isConstOrConstSplat(N1);
// Helper for determining whether a value is a power-2 constant scalar or a
// vector of such elements.
auto IsPowerOfTwo = [](ConstantSDNode *C) {
@ -3119,13 +3142,6 @@ SDValue DAGCombiner::visitSDIV(SDNode *N) {
if (SDValue Op = BuildSDIV(N))
return Op;
// sdiv, srem -> sdivrem
// If the divisor is constant, then return DIVREM only if isIntDivCheap() is
// true. Otherwise, we break the simplification logic in visitREM().
if (!N1C || TLI.isIntDivCheap(N->getValueType(0), Attr))
if (SDValue DivRem = useDivRem(N))
return DivRem;
return SDValue();
}
@ -3155,6 +3171,26 @@ SDValue DAGCombiner::visitUDIV(SDNode *N) {
if (SDValue NewSel = foldBinOpIntoSelect(N))
return NewSel;
if (SDValue V = visitUDIVLike(N0, N1, N))
return V;
// sdiv, srem -> sdivrem
// If the divisor is constant, then return DIVREM only if isIntDivCheap() is
// true. Otherwise, we break the simplification logic in visitREM().
AttributeList Attr = DAG.getMachineFunction().getFunction().getAttributes();
if (!N1C || TLI.isIntDivCheap(N->getValueType(0), Attr))
if (SDValue DivRem = useDivRem(N))
return DivRem;
return SDValue();
}
SDValue DAGCombiner::visitUDIVLike(SDValue N0, SDValue N1, SDNode *N) {
SDLoc DL(N);
EVT VT = N->getValueType(0);
ConstantSDNode *N1C = isConstOrConstSplat(N1);
// fold (udiv x, (1 << c)) -> x >>u c
if (isConstantOrConstantVector(N1, /*NoOpaques*/ true) &&
DAG.isKnownToBeAPowerOfTwo(N1)) {
@ -3190,13 +3226,6 @@ SDValue DAGCombiner::visitUDIV(SDNode *N) {
if (SDValue Op = BuildUDIV(N))
return Op;
// sdiv, srem -> sdivrem
// If the divisor is constant, then return DIVREM only if isIntDivCheap() is
// true. Otherwise, we break the simplification logic in visitREM().
if (!N1C || TLI.isIntDivCheap(N->getValueType(0), Attr))
if (SDValue DivRem = useDivRem(N))
return DivRem;
return SDValue();
}