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[ConstantRange] Rewrite shl to avoid repeated calls to getUnsignedMax and avoid creating the min APInt until we're sure we need it. Use inplace shift operations. 

llvm-svn: 302510
This commit is contained in:
Craig Topper 2017-05-09 07:04:04 +00:00
parent 79b7666f02
commit ef02803bed
1 changed files with 11 additions and 7 deletions
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18
llvm/lib/IR/ConstantRange.cpp
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@ -892,16 +892,20 @@ ConstantRange::shl(const ConstantRange &Other) const {
if (isEmptySet() || Other.isEmptySet())
return ConstantRange(getBitWidth(), /*isFullSet=*/false);
APInt min = getUnsignedMin().shl(Other.getUnsignedMin());
APInt max = getUnsignedMax().shl(Other.getUnsignedMax());
APInt max = getUnsignedMax();
APInt Other_umax = Other.getUnsignedMax();
// there's no overflow!
APInt Zeros(getBitWidth(), getUnsignedMax().countLeadingZeros());
if (Zeros.ugt(Other.getUnsignedMax()))
return ConstantRange(std::move(min), std::move(max) + 1);
// there's overflow!
if (Other_umax.uge(max.countLeadingZeros()))
return ConstantRange(getBitWidth(), /*isFullSet=*/true);
// FIXME: implement the other tricky cases
return ConstantRange(getBitWidth(), /*isFullSet=*/true);
APInt min = getUnsignedMin();
min <<= Other.getUnsignedMin();
max <<= Other_umax;
return ConstantRange(std::move(min), std::move(max) + 1);
}
ConstantRange