https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113614
--- Comment #3 from GCC Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Jakub Jelinek <ja...@gcc.gnu.org>: https://gcc.gnu.org/g:a12b0e9360e88fceb0414bfb34c8c1ad87c5ac90 commit r14-8468-ga12b0e9360e88fceb0414bfb34c8c1ad87c5ac90 Author: Jakub Jelinek <ja...@redhat.com> Date: Sat Jan 27 13:06:55 2024 +0100 lower-bitint: Avoid sign-extending cast to unsigned types feeding div/mod/float [PR113614] The following testcase is miscompiled, because some narrower value is sign-extended to wider unsigned _BitInt used as division operand. handle_operand_addr for that case returns the narrower value and precision -prec_of_narrower_value. That works fine for multiplication (at least, normal multiplication, but we don't merge casts with .MUL_OVERFLOW or the ubsan multiplication right now), because the result is the same whether we treat the arguments as signed or unsigned. But is completely wrong for division/modulo or conversions to floating-point, if we pass negative prec for an input operand of a libgcc handler, those treat it like a negative number, not an unsigned one sign-extended from something smaller (and it doesn't know to what precision it has been extended). So, the following patch fixes it by making sure we don't merge such sign-extensions to unsigned _BitInt type with division, modulo or conversions to floating point. 2024-01-27 Jakub Jelinek <ja...@redhat.com> PR tree-optimization/113614 * gimple-lower-bitint.cc (gimple_lower_bitint): Don't merge widening casts from signed to unsigned types with TRUNC_DIV_EXPR, TRUNC_MOD_EXPR or FLOAT_EXPR uses. * gcc.dg/torture/bitint-54.c: New test.
