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[X86] Remove dead code for turning vector shifts by large amounts into a zero vector.

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Pretty sure these are handled by a target independent DAG combine that turns them into undef these days.

llvm-svn: 321056
This commit is contained in:
Craig Topper 2017-12-19 05:21:50 +00:00
parent 20683fd338
commit 14f0f17b4b
1 changed files with 0 additions and 36 deletions
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36
lib/Target/X86/X86ISelLowering.cpp
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@ -32622,37 +32622,6 @@ static SDValue combineShiftRightLogical(SDNode *N, SelectionDAG &DAG) {
return SDValue();
}
/// \brief Returns a vector of 0s if the node in input is a vector logical
/// shift by a constant amount which is known to be bigger than or equal
/// to the vector element size in bits.
static SDValue performShiftToAllZeros(SDNode *N, SelectionDAG &DAG,
const X86Subtarget &Subtarget) {
EVT VT = N->getValueType(0);
if (VT != MVT::v2i64 && VT != MVT::v4i32 && VT != MVT::v8i16 &&
(!Subtarget.hasInt256() ||
(VT != MVT::v4i64 && VT != MVT::v8i32 && VT != MVT::v16i16)))
return SDValue();
SDValue Amt = N->getOperand(1);
SDLoc DL(N);
if (auto *AmtBV = dyn_cast<BuildVectorSDNode>(Amt))
if (auto *AmtSplat = AmtBV->getConstantSplatNode()) {
const APInt &ShiftAmt = AmtSplat->getAPIntValue();
unsigned MaxAmount =
VT.getSimpleVT().getScalarSizeInBits();
// SSE2/AVX2 logical shifts always return a vector of 0s
// if the shift amount is bigger than or equal to
// the element size. The constant shift amount will be
// encoded as a 8-bit immediate.
if (ShiftAmt.trunc(8).uge(MaxAmount))
return getZeroVector(VT.getSimpleVT(), Subtarget, DAG, DL);
}
return SDValue();
}
static SDValue combineShift(SDNode* N, SelectionDAG &DAG,
TargetLowering::DAGCombinerInfo &DCI,
const X86Subtarget &Subtarget) {
@ -32668,11 +32637,6 @@ static SDValue combineShift(SDNode* N, SelectionDAG &DAG,
if (SDValue V = combineShiftRightLogical(N, DAG))
return V;
// Try to fold this logical shift into a zero vector.
if (N->getOpcode() != ISD::SRA)
if (SDValue V = performShiftToAllZeros(N, DAG, Subtarget))
return V;
return SDValue();
}