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[InstCombine] foldICmpUsingKnownBits - use KnownBits signed/unsigned getMin/MaxValue helpers. NFCI.

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Replace the local compute*SignedMinMaxValuesFromKnownBits methods with the equivalent KnownBits helpers to determine the min/max value ranges.
This commit is contained in:
Simon Pilgrim 2020-12-24 14:22:26 +00:00
parent 0a16296c8d
commit eb7b7b06a6
1 changed files with 8 additions and 43 deletions
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51
lib/Transforms/InstCombine/InstCombineCompares.cpp
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@ -96,45 +96,6 @@ static bool isSignTest(ICmpInst::Predicate &Pred, const APInt &C) {
return false;
}
/// Given a signed integer type and a set of known zero and one bits, compute
/// the maximum and minimum values that could have the specified known zero and
/// known one bits, returning them in Min/Max.
/// TODO: Move to method on KnownBits struct?
static void computeSignedMinMaxValuesFromKnownBits(const KnownBits &Known,
APInt &Min, APInt &Max) {
assert(Known.getBitWidth() == Min.getBitWidth() &&
Known.getBitWidth() == Max.getBitWidth() &&
"KnownZero, KnownOne and Min, Max must have equal bitwidth.");
APInt UnknownBits = ~(Known.Zero|Known.One);
// The minimum value is when all unknown bits are zeros, EXCEPT for the sign
// bit if it is unknown.
Min = Known.One;
Max = Known.One|UnknownBits;
if (UnknownBits.isNegative()) { // Sign bit is unknown
Min.setSignBit();
Max.clearSignBit();
}
}
/// Given an unsigned integer type and a set of known zero and one bits, compute
/// the maximum and minimum values that could have the specified known zero and
/// known one bits, returning them in Min/Max.
/// TODO: Move to method on KnownBits struct?
static void computeUnsignedMinMaxValuesFromKnownBits(const KnownBits &Known,
APInt &Min, APInt &Max) {
assert(Known.getBitWidth() == Min.getBitWidth() &&
Known.getBitWidth() == Max.getBitWidth() &&
"Ty, KnownZero, KnownOne and Min, Max must have equal bitwidth.");
APInt UnknownBits = ~(Known.Zero|Known.One);
// The minimum value is when the unknown bits are all zeros.
Min = Known.One;
// The maximum value is when the unknown bits are all ones.
Max = Known.One|UnknownBits;
}
/// This is called when we see this pattern:
/// cmp pred (load (gep GV, ...)), cmpcst
/// where GV is a global variable with a constant initializer. Try to simplify
@ -5050,11 +5011,15 @@ Instruction *InstCombinerImpl::foldICmpUsingKnownBits(ICmpInst &I) {
APInt Op0Min(BitWidth, 0), Op0Max(BitWidth, 0);
APInt Op1Min(BitWidth, 0), Op1Max(BitWidth, 0);
if (I.isSigned()) {
computeSignedMinMaxValuesFromKnownBits(Op0Known, Op0Min, Op0Max);
computeSignedMinMaxValuesFromKnownBits(Op1Known, Op1Min, Op1Max);
Op0Min = Op0Known.getSignedMinValue();
Op0Max = Op0Known.getSignedMaxValue();
Op1Min = Op1Known.getSignedMinValue();
Op1Max = Op1Known.getSignedMaxValue();
} else {
computeUnsignedMinMaxValuesFromKnownBits(Op0Known, Op0Min, Op0Max);
computeUnsignedMinMaxValuesFromKnownBits(Op1Known, Op1Min, Op1Max);
Op0Min = Op0Known.getMinValue();
Op0Max = Op0Known.getMaxValue();
Op1Min = Op1Known.getMinValue();
Op1Max = Op1Known.getMaxValue();
}
// If Min and Max are known to be the same, then SimplifyDemandedBits figured