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Fix overflows in complex sqrt lowering. #88480

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Apr 12, 2024
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Fix overflows in complex sqrt lowering. #88480

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166 changes: 97 additions & 69 deletions mlir/lib/Conversion/ComplexToStandard/ComplexToStandard.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -27,35 +27,52 @@ using namespace mlir;

namespace {

// Returns the absolute value or its square root.
Value computeAbs(Value real, Value imag, arith::FastMathFlags fmf,
ImplicitLocOpBuilder &b, bool returnSqrt = false) {
Value one = b.create<arith::ConstantOp>(real.getType(),
b.getFloatAttr(real.getType(), 1.0));

Value absReal = b.create<math::AbsFOp>(real, fmf);
Value absImag = b.create<math::AbsFOp>(imag, fmf);

Value max = b.create<arith::MaximumFOp>(absReal, absImag, fmf);
Value min = b.create<arith::MinimumFOp>(absReal, absImag, fmf);
Value ratio = b.create<arith::DivFOp>(min, max, fmf);
Value ratioSq = b.create<arith::MulFOp>(ratio, ratio, fmf);
Value ratioSqPlusOne = b.create<arith::AddFOp>(ratioSq, one, fmf);
Value result;

if (returnSqrt) {
Value quarter = b.create<arith::ConstantOp>(
real.getType(), b.getFloatAttr(real.getType(), 0.25));
// sqrt(sqrt(a*b)) would avoid the pow, but will overflow more easily.
Value sqrt = b.create<math::SqrtOp>(max, fmf);
Value p025 = b.create<math::PowFOp>(ratioSqPlusOne, quarter, fmf);
result = b.create<arith::MulFOp>(sqrt, p025, fmf);
} else {
Value sqrt = b.create<math::SqrtOp>(ratioSqPlusOne, fmf);
result = b.create<arith::MulFOp>(max, sqrt, fmf);
}

Value isNaN =
b.create<arith::CmpFOp>(arith::CmpFPredicate::UNO, result, result, fmf);
return b.create<arith::SelectOp>(isNaN, min, result);
}

struct AbsOpConversion : public OpConversionPattern<complex::AbsOp> {
using OpConversionPattern<complex::AbsOp>::OpConversionPattern;

LogicalResult
matchAndRewrite(complex::AbsOp op, OpAdaptor adaptor,
ConversionPatternRewriter &rewriter) const override {
mlir::ImplicitLocOpBuilder b(op.getLoc(), rewriter);
ImplicitLocOpBuilder b(op.getLoc(), rewriter);

arith::FastMathFlags fmf = op.getFastMathFlagsAttr().getValue();

Type elementType = op.getType();
Value one = b.create<arith::ConstantOp>(elementType,
b.getFloatAttr(elementType, 1.0));

Value real = b.create<complex::ReOp>(adaptor.getComplex());
Value imag = b.create<complex::ImOp>(adaptor.getComplex());
Value absReal = b.create<math::AbsFOp>(real, fmf);
Value absImag = b.create<math::AbsFOp>(imag, fmf);

Value max = b.create<arith::MaximumFOp>(absReal, absImag, fmf);
Value min = b.create<arith::MinimumFOp>(absReal, absImag, fmf);
Value ratio = b.create<arith::DivFOp>(min, max, fmf);
Value ratioSq = b.create<arith::MulFOp>(ratio, ratio, fmf);
Value ratioSqPlusOne = b.create<arith::AddFOp>(ratioSq, one, fmf);
Value sqrt = b.create<math::SqrtOp>(ratioSqPlusOne, fmf);
Value result = b.create<arith::MulFOp>(max, sqrt, fmf);
Value isNaN =
b.create<arith::CmpFOp>(arith::CmpFPredicate::UNO, result, result, fmf);
rewriter.replaceOpWithNewOp<arith::SelectOp>(op, isNaN, min, result);
rewriter.replaceOp(op, computeAbs(real, imag, fmf, b));

return success();
}
Expand Down Expand Up @@ -829,60 +846,71 @@ struct SqrtOpConversion : public OpConversionPattern<complex::SqrtOp> {
LogicalResult
matchAndRewrite(complex::SqrtOp op, OpAdaptor adaptor,
ConversionPatternRewriter &rewriter) const override {
mlir::ImplicitLocOpBuilder b(op.getLoc(), rewriter);
ImplicitLocOpBuilder b(op.getLoc(), rewriter);

auto type = cast<ComplexType>(op.getType());
Type elementType = type.getElementType();
Value arg = adaptor.getComplex();
arith::FastMathFlagsAttr fmf = op.getFastMathFlagsAttr();

Value zero =
b.create<arith::ConstantOp>(elementType, b.getZeroAttr(elementType));

Value real = b.create<complex::ReOp>(elementType, adaptor.getComplex());
Value imag = b.create<complex::ImOp>(elementType, adaptor.getComplex());

Value absLhs = b.create<math::AbsFOp>(real, fmf);
Value absArg = b.create<complex::AbsOp>(elementType, arg, fmf);
Value addAbs = b.create<arith::AddFOp>(absLhs, absArg, fmf);
auto elementType = type.getElementType().cast<FloatType>();
arith::FastMathFlags fmf = op.getFastMathFlagsAttr().getValue();

auto cst = [&](APFloat v) {
return b.create<arith::ConstantOp>(elementType,
b.getFloatAttr(elementType, v));
};
const auto &floatSemantics = elementType.getFloatSemantics();
Value zero = cst(APFloat::getZero(floatSemantics));
Value half = b.create<arith::ConstantOp>(elementType,
b.getFloatAttr(elementType, 0.5));
Value halfAddAbs = b.create<arith::MulFOp>(addAbs, half, fmf);
Value sqrtAddAbs = b.create<math::SqrtOp>(halfAddAbs, fmf);

Value realIsNegative =
b.create<arith::CmpFOp>(arith::CmpFPredicate::OLT, real, zero);
Value imagIsNegative =
b.create<arith::CmpFOp>(arith::CmpFPredicate::OLT, imag, zero);

Value resultReal = sqrtAddAbs;

Value imagDivTwoResultReal = b.create<arith::DivFOp>(
imag, b.create<arith::AddFOp>(resultReal, resultReal, fmf), fmf);

Value negativeResultReal = b.create<arith::NegFOp>(resultReal);

Value real = b.create<complex::ReOp>(elementType, adaptor.getComplex());
Value imag = b.create<complex::ImOp>(elementType, adaptor.getComplex());
Value absSqrt = computeAbs(real, imag, fmf, b, /*returnSqrt=*/true);
Value argArg = b.create<math::Atan2Op>(imag, real, fmf);
Value sqrtArg = b.create<arith::MulFOp>(argArg, half, fmf);
Value cos = b.create<math::CosOp>(sqrtArg, fmf);
Value sin = b.create<math::SinOp>(sqrtArg, fmf);
// sin(atan2(0, inf)) = 0, sqrt(abs(inf)) = inf, but we can't multiply
// 0 * inf.
Value sinIsZero =
b.create<arith::CmpFOp>(arith::CmpFPredicate::OEQ, sin, zero, fmf);

Value resultReal = b.create<arith::MulFOp>(absSqrt, cos, fmf);
Value resultImag = b.create<arith::SelectOp>(
realIsNegative,
b.create<arith::SelectOp>(imagIsNegative, negativeResultReal,
resultReal),
imagDivTwoResultReal);

resultReal = b.create<arith::SelectOp>(
realIsNegative,
b.create<arith::DivFOp>(
imag, b.create<arith::AddFOp>(resultImag, resultImag, fmf), fmf),
resultReal);

Value realIsZero =
b.create<arith::CmpFOp>(arith::CmpFPredicate::OEQ, real, zero);
Value imagIsZero =
b.create<arith::CmpFOp>(arith::CmpFPredicate::OEQ, imag, zero);
Value argIsZero = b.create<arith::AndIOp>(realIsZero, imagIsZero);

resultReal = b.create<arith::SelectOp>(argIsZero, zero, resultReal);
resultImag = b.create<arith::SelectOp>(argIsZero, zero, resultImag);
sinIsZero, zero, b.create<arith::MulFOp>(absSqrt, sin, fmf));
if (!arith::bitEnumContainsAll(fmf, arith::FastMathFlags::nnan |
arith::FastMathFlags::ninf)) {
Value inf = cst(APFloat::getInf(floatSemantics));
Value negInf = cst(APFloat::getInf(floatSemantics, true));
Value nan = cst(APFloat::getNaN(floatSemantics));
Value absImag = b.create<math::AbsFOp>(elementType, imag, fmf);

Value absImagIsInf =
b.create<arith::CmpFOp>(arith::CmpFPredicate::OEQ, absImag, inf, fmf);
Value absImagIsNotInf =
b.create<arith::CmpFOp>(arith::CmpFPredicate::ONE, absImag, inf, fmf);
Value realIsInf =
b.create<arith::CmpFOp>(arith::CmpFPredicate::OEQ, real, inf, fmf);
Value realIsNegInf =
b.create<arith::CmpFOp>(arith::CmpFPredicate::OEQ, real, negInf, fmf);

resultReal = b.create<arith::SelectOp>(
b.create<arith::AndIOp>(realIsNegInf, absImagIsNotInf), zero,
resultReal);
resultReal = b.create<arith::SelectOp>(
b.create<arith::OrIOp>(absImagIsInf, realIsInf), inf, resultReal);

Value imagSignInf = b.create<math::CopySignOp>(inf, imag, fmf);
resultImag = b.create<arith::SelectOp>(
b.create<arith::CmpFOp>(arith::CmpFPredicate::UNO, absSqrt, absSqrt),
nan, resultImag);
resultImag = b.create<arith::SelectOp>(
b.create<arith::OrIOp>(absImagIsInf, realIsNegInf), imagSignInf,
resultImag);
}

Value resultIsZero =
b.create<arith::CmpFOp>(arith::CmpFPredicate::OEQ, absSqrt, zero, fmf);
resultReal = b.create<arith::SelectOp>(resultIsZero, zero, resultReal);
resultImag = b.create<arith::SelectOp>(resultIsZero, zero, resultImag);

rewriter.replaceOpWithNewOp<complex::CreateOp>(op, type, resultReal,
resultImag);
Expand Down Expand Up @@ -1065,27 +1093,27 @@ static Value powOpConversionImpl(mlir::ImplicitLocOpBuilder &builder,
// Case 2:
// 1^(c + d*i) = 1 + 0*i
Value lhsEqOne = builder.create<arith::AndIOp>(
builder.create<arith::CmpFOp>(arith::CmpFPredicate::OEQ, a, one),
builder.create<arith::CmpFOp>(arith::CmpFPredicate::OEQ, a, one, fmf),
bEqZero);
Value cutoff2 =
builder.create<arith::SelectOp>(lhsEqOne, complexOne, cutoff1);

// Case 3:
// inf^(c + 0*i) = inf + 0*i, c > 0
Value lhsEqInf = builder.create<arith::AndIOp>(
builder.create<arith::CmpFOp>(arith::CmpFPredicate::OEQ, a, inf),
builder.create<arith::CmpFOp>(arith::CmpFPredicate::OEQ, a, inf, fmf),
bEqZero);
Value rhsGt0 = builder.create<arith::AndIOp>(
dEqZero,
builder.create<arith::CmpFOp>(arith::CmpFPredicate::OGT, c, zero));
builder.create<arith::CmpFOp>(arith::CmpFPredicate::OGT, c, zero, fmf));
Value cutoff3 = builder.create<arith::SelectOp>(
builder.create<arith::AndIOp>(lhsEqInf, rhsGt0), complexInf, cutoff2);

// Case 4:
// inf^(c + 0*i) = 0 + 0*i, c < 0
Value rhsLt0 = builder.create<arith::AndIOp>(
dEqZero,
builder.create<arith::CmpFOp>(arith::CmpFPredicate::OLT, c, zero));
builder.create<arith::CmpFOp>(arith::CmpFPredicate::OLT, c, zero, fmf));
Value cutoff4 = builder.create<arith::SelectOp>(
builder.create<arith::AndIOp>(lhsEqInf, rhsLt0), complexZero, cutoff3);

Expand Down
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