https://gcc.gnu.org/bugzilla/show_bug.cgi?id=121127
--- Comment #4 from GCC Commits <cvs-commit at gcc dot gnu.org> --- The releases/gcc-15 branch has been updated by Jakub Jelinek <ja...@gcc.gnu.org>: https://gcc.gnu.org/g:332e891a8a42a9ba971174c8282864fbc1976b7f commit r15-10205-g332e891a8a42a9ba971174c8282864fbc1976b7f Author: Jakub Jelinek <ja...@redhat.com> Date: Wed Aug 6 11:28:37 2025 +0200 bitint: Fix up handling of uninitialized mul/div/float cast operands [PR121127] handle_operand_addr (used for the cases where we use libgcc APIs, so multiplication, division, modulo, casts of _BitInt to float/dfp) when it sees default definition of an SSA_NAME which is not PARM_DECL (i.e. uninitialized one) just allocates single uninitialized limb, there is no need to waste more memory on it, it can just tell libgcc that it has 64-bit precision, not say 1024 bit etc. Unfortunately, doing this runs into some asserts when we have a narrowing cast of the uninitialized SSA_NAME (but still large/huge _BitInt). The following patch fixes that by using a magic value in *prec_stored for the uninitialized cases (0) and just don't do any *prec tweaks for narrowing casts from that. precs still needs to be maintained as before, that one is used for big endian adjustment. 2025-08-06 Jakub Jelinek <ja...@redhat.com> PR tree-optimization/121127 * gimple-lower-bitint.cc (bitint_large_huge::handle_operand_addr): For uninitialized SSA_NAME, set *prec_stored to 0 rather than *prec. Handle that case in narrowing casts. If prec_stored is non-NULL, set *prec_stored to prec_stored_val. * gcc.dg/bitint-125.c: New test. (cherry picked from commit d175a6b119b8ab177ab9d9fb81dcac1794d18ad6)
