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[X86] Return UNDEF from LowerScalarImmediateShift when the shift amount is out of range.

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I think we only turn out of range shiftss to undef when
all elements are out of range or the shift amount is a splat out
of range. I'm not sure which, I didn't check.

During lowering we can split a shift where some elements
are out of range into multiple shifts. This can create a
new shift with a splat shift amount that is out of range.

This patch returns undef for this case.

Fixes PR42615.

Differential Revision: https://reviews.llvm.org/D64699

llvm-svn: 366096
This commit is contained in:
Craig Topper 2019-07-15 17:56:57 +00:00
parent 8f74f32e3e
commit c34f81ed6b
1 changed files with 5 additions and 2 deletions
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7
lib/Target/X86/X86ISelLowering.cpp
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@ -25033,8 +25033,11 @@ static SDValue LowerScalarImmediateShift(SDValue Op, SelectionDAG &DAG,
APInt APIntShiftAmt;
if (!isConstantSplat(Amt, APIntShiftAmt))
return SDValue();
assert(APIntShiftAmt.ult(VT.getScalarSizeInBits()) &&
"Out of range shift amount");
// If the shift amount is out of range, return undef.
if (APIntShiftAmt.uge(VT.getScalarSizeInBits()))
return DAG.getUNDEF(VT);
uint64_t ShiftAmt = APIntShiftAmt.getZExtValue();
if (SupportedVectorShiftWithImm(VT, Subtarget, Op.getOpcode()))