On Fri, Oct 14, 2022 at 05:08:51PM +0200, Aldy Hernandez wrote:
> [Jakub, while we're on the subject of signed zeros and copysign, does
> this look OK to you?]
>
> copysign(MAGNITUDE, SIGN) is implemented as the absolute of MAGNITUDE,
> with SIGN applied. If the sign of "SIGN" cannot be determined, we
> return a range of [-MAGNITUDE, +MAGNITUDE].
>
> gcc/ChangeLog:
>
> * gimple-range-op.cc (class cfn_copysign): New.
> (gimple_range_op_handler::maybe_builtin_call): Add
> CFN_BUILT_IN_COPYSIGN*.
> ---
> gcc/gimple-range-op.cc | 39 +++++++++++++++++++++++++++++++++++++++
> 1 file changed, 39 insertions(+)
>
> diff --git a/gcc/gimple-range-op.cc b/gcc/gimple-range-op.cc
> index 527893f66af..8137308f32e 100644
> --- a/gcc/gimple-range-op.cc
> +++ b/gcc/gimple-range-op.cc
> @@ -342,6 +342,38 @@ public:
> }
> } op_cfn_signbit;
>
> +// Implement range operator for CFN_BUILT_IN_COPYSIGN
> +class cfn_copysign : public range_operator_float
> +{
> +public:
> + using range_operator_float::fold_range;
> + virtual bool fold_range (frange &r, tree type, const frange &lh,
> + const frange &rh, relation_kind) const override
> + {
> + frange neg;
> + range_op_handler abs_op (ABS_EXPR, type);
> + range_op_handler neg_op (NEGATE_EXPR, type);
> + if (!abs_op || !abs_op.fold_range (r, type, lh, frange (type)))
> + return false;
> + if (!neg_op || !neg_op.fold_range (neg, type, r, frange (type)))
> + return false;
> +
> + bool signbit;
> + if (rh.signbit_p (signbit))
> + {
> + // If the sign is negative, flip the result from ABS,
> + // otherwise leave things positive.
> + if (signbit)
> + r = neg;
> + }
> + else
> + // If the sign is unknown, keep the positive and negative
> + // alternatives.
> + r.union_ (neg);
> + return true;
> + }
> +} op_cfn_copysign;
> +
> // Implement range operator for CFN_BUILT_IN_TOUPPER and
> CFN_BUILT_IN_TOLOWER.
> class cfn_toupper_tolower : public range_operator
> {
> @@ -762,6 +794,13 @@ gimple_range_op_handler::maybe_builtin_call ()
> m_valid = true;
> break;
>
> + CASE_FLT_FN (CFN_BUILT_IN_COPYSIGN):
CASE_CFN_COPYSIGN_ALL:
instead.
Otherwise LGTM.
> + m_op1 = gimple_call_arg (call, 0);
> + m_op2 = gimple_call_arg (call, 1);
> + m_float = &op_cfn_copysign;
> + m_valid = true;
> + break;
> +
> case CFN_BUILT_IN_TOUPPER:
> case CFN_BUILT_IN_TOLOWER:
> // Only proceed If the argument is compatible with the LHS.
> --
> 2.37.3
Jakub
