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[NFC][InstCombine] dropRedundantMaskingOfLeftShiftInput(): some NFC diff shaving

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llvm-svn: 372171
This commit is contained in:
Roman Lebedev 2019-09-17 19:32:26 +00:00
parent 74ebe31eb0
commit 07cce5d638
1 changed files with 11 additions and 8 deletions
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19
lib/Transforms/InstCombine/InstCombineShifts.cpp
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@ -131,7 +131,8 @@ reassociateShiftAmtsOfTwoSameDirectionShifts(BinaryOperator *Sh0,
// c,d,e,f) (ShiftShAmt-MaskShAmt) s>= 0 (i.e. ShiftShAmt u>= MaskShAmt)
static Instruction *
dropRedundantMaskingOfLeftShiftInput(BinaryOperator *OuterShift,
const SimplifyQuery &SQ) {
const SimplifyQuery &SQ,
InstCombiner::BuilderTy &Builder) {
assert(OuterShift->getOpcode() == Instruction::BinaryOps::Shl &&
"The input must be 'shl'!");
@ -153,17 +154,19 @@ dropRedundantMaskingOfLeftShiftInput(BinaryOperator *OuterShift,
Value *X;
if (match(Masked, m_c_And(m_CombineOr(MaskA, MaskB), m_Value(X)))) {
// Can we simplify (MaskShAmt+ShiftShAmt) ?
Value *SumOfShAmts =
auto *SumOfShAmts = dyn_cast_or_null<Constant>(
SimplifyAddInst(MaskShAmt, ShiftShAmt, /*IsNSW=*/false, /*IsNUW=*/false,
SQ.getWithInstruction(OuterShift));
SQ.getWithInstruction(OuterShift)));
if (!SumOfShAmts)
return nullptr; // Did not simplify.
// Is the total shift amount *not* smaller than the bit width?
// FIXME: could also rely on ConstantRange.
unsigned BitWidth = X->getType()->getScalarSizeInBits();
Type *Ty = X->getType();
unsigned BitWidth = Ty->getScalarSizeInBits();
// In this pattern SumOfShAmts correlates with the number of low bits that
// shall remain in the root value (OuterShift). If SumOfShAmts is less than
// bitwidth, we'll need to also produce a mask to keep SumOfShAmts low bits.
if (!match(SumOfShAmts, m_SpecificInt_ICMP(ICmpInst::Predicate::ICMP_UGE,
APInt(BitWidth, BitWidth))))
return nullptr;
return nullptr; // FIXME.
// All good, we can do this fold.
} else if (match(Masked, m_c_And(m_CombineOr(MaskC, MaskD), m_Value(X))) ||
match(Masked, m_Shr(m_Shl(m_Value(X), m_Value(MaskShAmt)),
@ -751,7 +754,7 @@ Instruction *InstCombiner::visitShl(BinaryOperator &I) {
if (Instruction *V = commonShiftTransforms(I))
return V;
if (Instruction *V = dropRedundantMaskingOfLeftShiftInput(&I, SQ))
if (Instruction *V = dropRedundantMaskingOfLeftShiftInput(&I, SQ, Builder))
return V;
Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);