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[ValueTracking] reduce code duplication; NFC

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The start value can't be null for something to be a non-zero
recurrence, so hoist that common check out of the switch.

Subsequent checks may be incomplete or over-specified as noted in:
D100408
This commit is contained in:
Sanjay Patel 2021-04-14 08:30:42 -04:00
parent 9c1bc49f11
commit b568083407
1 changed files with 7 additions and 9 deletions
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16
lib/Analysis/ValueTracking.cpp
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@ -2213,33 +2213,31 @@ static bool rangeMetadataExcludesValue(const MDNode* Ranges, const APInt& Value)
return true;
}
/// Try to detect a recurrence that monotonically increases from a non-zero
/// starting value. These are common as induction variables.
static bool isNonZeroRecurrence(const PHINode *PN) {
// Try and detect a recurrence that monotonically increases from a
// starting value, as these are common as induction variables.
BinaryOperator *BO = nullptr;
Value *Start = nullptr, *Step = nullptr;
const APInt *StartC, *StepC;
if (!matchSimpleRecurrence(PN, BO, Start, Step) ||
!match(Start, m_APInt(StartC)))
!match(Start, m_APInt(StartC)) || StartC->isNullValue())
return false;
switch (BO->getOpcode()) {
case Instruction::Add:
return match(Step, m_APInt(StepC)) &&
((BO->hasNoUnsignedWrap() && !StartC->isNullValue() &&
!StepC->isNullValue()) ||
((BO->hasNoUnsignedWrap() && !StepC->isNullValue()) ||
(BO->hasNoSignedWrap() && StartC->isStrictlyPositive() &&
StepC->isNonNegative()));
case Instruction::Mul:
return !StartC->isNullValue() && match(Step, m_APInt(StepC)) &&
return match(Step, m_APInt(StepC)) &&
((BO->hasNoUnsignedWrap() && !StepC->isNullValue()) ||
(BO->hasNoSignedWrap() && StepC->isStrictlyPositive()));
case Instruction::Shl:
return !StartC->isNullValue() &&
(BO->hasNoUnsignedWrap() || BO->hasNoSignedWrap());
return BO->hasNoUnsignedWrap() || BO->hasNoSignedWrap();
case Instruction::AShr:
case Instruction::LShr:
return !StartC->isNullValue() && BO->isExact();
return BO->isExact();
default:
return false;
}