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[Analysis] simplify propagation of FMF in recurrences; NFC 

This is a mess, but this is hopefully no-functional-change.
The 'Prev' descriptor is only used for min/max recurrences
or when starting a match from a phi, so it should not be a
factor when propagating FMF for fmul/fadd.

The API is confusing (and should be reduced in subsequent steps)
because the "UnsafeAlgebraInst" appears to actually be a placeholder
for a recurrence that does NOT have FMF, but we still want to
treat it as reassociative.
This commit is contained in:
Sanjay Patel 2021-03-03 16:53:49 -05:00
parent 295ea050ad
commit b3f0c2653b
1 changed files with 5 additions and 8 deletions
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13
llvm/lib/Analysis/IVDescriptors.cpp
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@ -565,10 +565,6 @@ RecurrenceDescriptor::isConditionalRdxPattern(RecurKind Kind, Instruction *I) {
RecurrenceDescriptor::InstDesc
RecurrenceDescriptor::isRecurrenceInstr(Instruction *I, RecurKind Kind,
InstDesc &Prev, FastMathFlags FMF) {
Instruction *UAI = Prev.getUnsafeAlgebraInst();
if (!UAI && isa<FPMathOperator>(I) && !I->hasAllowReassoc())
UAI = I; // Found an unsafe (unvectorizable) algebra instruction.
switch (I->getOpcode()) {
default:
return InstDesc(false, I);
@ -587,10 +583,12 @@ RecurrenceDescriptor::isRecurrenceInstr(Instruction *I, RecurKind Kind,
return InstDesc(Kind == RecurKind::Xor, I);
case Instruction::FDiv:
case Instruction::FMul:
return InstDesc(Kind == RecurKind::FMul, I, UAI);
return InstDesc(Kind == RecurKind::FMul, I,
I->hasAllowReassoc() ? nullptr : I);
case Instruction::FSub:
case Instruction::FAdd:
return InstDesc(Kind == RecurKind::FAdd, I, UAI);
return InstDesc(Kind == RecurKind::FAdd, I,
I->hasAllowReassoc() ? nullptr : I);
case Instruction::Select:
if (Kind == RecurKind::FAdd || Kind == RecurKind::FMul)
return isConditionalRdxPattern(Kind, I);
@ -598,8 +596,7 @@ RecurrenceDescriptor::isRecurrenceInstr(Instruction *I, RecurKind Kind,
case Instruction::FCmp:
case Instruction::ICmp:
if (isIntMinMaxRecurrenceKind(Kind) ||
(FMF.noNaNs() && FMF.noSignedZeros() &&
isFPMinMaxRecurrenceKind(Kind)))
(FMF.noNaNs() && FMF.noSignedZeros() && isFPMinMaxRecurrenceKind(Kind)))
return isMinMaxSelectCmpPattern(I, Prev);
return InstDesc(false, I);
}