Skip to content

[flang][runtime] Don't round hexadecimal floating-point input #76586

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
merged 1 commit into from
Jan 2, 2024
Merged

[flang][runtime] Don't round hexadecimal floating-point input #76586

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
6 changes: 6 additions & 0 deletions flang/docs/Extensions.md
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -645,6 +645,12 @@ end
only in function references, but not an explicit `INTRINSIC` statement,
its name is not brought into other scopes by a `USE` statement.

* Should hexadecimal floating-point input editing apply any rounding?
F'2023 subclause 13.7.2.3.8 only discusses rounding in the context of
decimal-to-binary conversion; it would seem to not apply, and so
we don't round. This seems to be how the Intel Fortran compilers
behave.

## De Facto Standard Features

* `EXTENDS_TYPE_OF()` returns `.TRUE.` if both of its arguments have the
Expand Down
38 changes: 3 additions & 35 deletions flang/runtime/edit-input.cpp
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -624,31 +624,6 @@ decimal::ConversionToBinaryResult<binaryPrecision> ConvertHexadecimal(
fraction <<= 1;
--expo;
}
// Rounding
bool increase{false};
switch (rounding) {
case decimal::RoundNearest: // RN & RP
increase = roundingBit && (guardBit | ((int)fraction & 1));
break;
case decimal::RoundUp: // RU
increase = !isNegative && (roundingBit | guardBit);
break;
case decimal::RoundDown: // RD
increase = isNegative && (roundingBit | guardBit);
break;
case decimal::RoundToZero: // RZ
break;
case decimal::RoundCompatible: // RC
increase = roundingBit != 0;
break;
}
if (increase) {
++fraction;
if (fraction >> binaryPrecision) {
fraction >>= 1;
++expo;
}
}
}
// Package & return result
constexpr RawType significandMask{(one << RealType::significandBits) - 1};
Expand All @@ -659,16 +634,9 @@ decimal::ConversionToBinaryResult<binaryPrecision> ConvertHexadecimal(
expo = 0; // subnormal
flags |= decimal::Underflow;
} else if (expo >= RealType::maxExponent) {
if (rounding == decimal::RoundToZero ||
(rounding == decimal::RoundDown && !isNegative) ||
(rounding == decimal::RoundUp && isNegative)) {
expo = RealType::maxExponent - 1; // +/-HUGE()
fraction = significandMask;
} else {
expo = RealType::maxExponent; // +/-Inf
fraction = 0;
flags |= decimal::Overflow;
}
expo = RealType::maxExponent; // +/-Inf
fraction = 0;
flags |= decimal::Overflow;
} else {
fraction &= significandMask; // remove explicit normalization unless x87
}
Expand Down