[flang] Correct overflow detection in folding of real->integer conversions
INT, NINT, FLOOR, and CEILING were failing to report overflow as an
error while folding operations with constant operands.
Differential Revision: https://reviews.llvm.org/D109922
GitOrigin-RevId: 43d41b295e15fcf9487279f700038d57c8eb43d8
diff --git a/include/flang/Evaluate/real.h b/include/flang/Evaluate/real.h
index fa637ab..bf43e68 100644
--- a/include/flang/Evaluate/real.h
+++ b/include/flang/Evaluate/real.h
@@ -221,21 +221,26 @@
return result;
}
ValueWithRealFlags<Real> intPart{ToWholeNumber(mode)};
- int exponent{intPart.value.Exponent()};
- result.flags.set(
- RealFlag::Overflow, exponent >= exponentBias + result.value.bits);
result.flags |= intPart.flags;
- int shift{
- exponent - exponentBias - binaryPrecision + 1}; // positive -> left
- result.value =
- result.value.ConvertUnsigned(intPart.value.GetFraction().SHIFTR(-shift))
- .value.SHIFTL(shift);
+ int exponent{intPart.value.Exponent()};
+ // shift positive -> left shift, negative -> right shift
+ int shift{exponent - exponentBias - binaryPrecision + 1};
+ // Apply any right shift before moving to the result type
+ auto rshifted{intPart.value.GetFraction().SHIFTR(-shift)};
+ auto converted{result.value.ConvertUnsigned(rshifted)};
+ if (converted.overflow) {
+ result.flags.set(RealFlag::Overflow);
+ }
+ result.value = converted.value.SHIFTL(shift);
+ if (converted.value.CompareUnsigned(result.value.SHIFTR(shift)) !=
+ Ordering::Equal) {
+ result.flags.set(RealFlag::Overflow);
+ }
if (IsSignBitSet()) {
- auto negated{result.value.Negate()};
- result.value = negated.value;
- if (negated.overflow) {
- result.flags.set(RealFlag::Overflow);
- }
+ result.value = result.value.Negate().value;
+ }
+ if (IsSignBitSet() != result.value.IsNegative()) {
+ result.flags.set(RealFlag::Overflow);
}
if (result.flags.test(RealFlag::Overflow)) {
result.value =
