https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106885
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Ever confirmed|0 |1
Last reconfirmed| |2022-09-08
Status|UNCONFIRMED |NEW
--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
We have ugly TYPE_OVERFLOW_SANITIZED checks in folding but it would be much
better if the sanitizing would happen before any folding is invoked ...
#0 fold_unary_loc (loc=258791, code=NEGATE_EXPR,
type=<integer_type 0x7ffff65365e8 int>, op0=<minus_expr 0x7ffff668f848>)
at /home/rguenther/src/trunk/gcc/fold-const.cc:9275
#1 0x0000000000f5d084 in fold (expr=<negate_expr 0x7ffff669f320>)
at /home/rguenther/src/trunk/gcc/fold-const.cc:13421
#2 0x0000000000beca8c in c_fully_fold_internal (
expr=<negate_expr 0x7ffff669f320>, in_init=false,
maybe_const_operands=0x7fffffffd5ab, maybe_const_itself=0x7fffffffd5aa,
for_int_const=false, lval=false)
at /home/rguenther/src/trunk/gcc/c/c-fold.cc:494
#3 0x0000000000beab7e in c_fully_fold (expr=<negate_expr 0x7ffff669f320>,
in_init=false, maybe_const=0x7fffffffd5ab, lval=false)
at /home/rguenther/src/trunk/gcc/c/c-fold.cc:125
#4 0x0000000000b7a840 in c_finish_return (loc=258791,
retval=<negate_expr 0x7ffff669f320>, origtype=<tree 0x0>)
at /home/rguenther/src/trunk/gcc/c/c-typeck.cc:10927
and match.pd exempts itself:
/* -(A - B) -> B - A. */
(simplify
(negate (minus @0 @1))
(if ((ANY_INTEGRAL_TYPE_P (type) && !TYPE_OVERFLOW_SANITIZED (type))
|| (FLOAT_TYPE_P (type)
&& !HONOR_SIGN_DEPENDENT_ROUNDING (type)
&& !HONOR_SIGNED_ZEROS (type)))
(minus @1 @0)))
but fold_negate_expr_1 does not:
638 case MINUS_EXPR:
639 /* - (A - B) -> B - A */
640 if (!HONOR_SIGN_DEPENDENT_ROUNDING (type)
641 && !HONOR_SIGNED_ZEROS (type))
642 return fold_build2_loc (loc, MINUS_EXPR, type,
643 TREE_OPERAND (t, 1), TREE_OPERAND (t,
0));
644 break;
