https://gcc.gnu.org/bugzilla/show_bug.cgi?id=126939
--- Comment #3 from GCC Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Jakub Jelinek <[email protected]>: https://gcc.gnu.org/g:471ee3f3c98f9afffd61443b995c67f76e0e4b99 commit r17-3457-g471ee3f3c98f9afffd61443b995c67f76e0e4b99 Author: Manjunath Matti <[email protected]> Date: Thu Aug 20 08:51:55 2026 +0200 bitintlower: Fix memmove source operand in finish_arith_overflow [PR126939] finish_arith_overflow builds a memmove call to shift the result of a double-width multiplication down inside the destination object, on big-endian targets where the computed value occupies more limbs than the destination. The destination argument correctly takes the address of OBJ, but SRC is a MEM_REF, that is a value of array type, and it is passed directly as memmove's second argument, which is a pointer. Wrap it in build_fold_addr_expr so that the address is passed instead. Since build_fold_addr_expr of a MEM_REF folds back to the pointer, no dereference is materialised. The affected code is guarded by bitint_big_endian, and is only reached for widths whose value needs more limbs than the destination object, that is huge _BitInt operands of __builtin_{add,sub,mul}_overflow, so it needs a big-endian target with _BitInt support to be exercised at all. It is being hit now that _BitInt is being enabled for powerpc (PR117584). Existing coverage is sufficient: on powerpc64 big-endian this fixes gcc.dg/torture/bitint-93.c and bitint-94.c at -O0 and -O2, and gcc.dg/torture/bitint-32.c through bitint-37.c at -O0. No new test is added. 2026-08-20 Manjunath Matti <[email protected]> PR middle-end/126939 * gimple-lower-bitint.cc (bitint_large_huge::finish_arith_overflow): Take the address of the memmove source operand.
