https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69525
--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> --- (Too much) reduced testcase, it requires the uninit use of r: typedef unsigned long long int ULong; typedef union { ULong w64[2]; } V128; typedef unsigned long HWord; void amd64g_dirtyhelper_AES (HWord opc4, V128* argD, V128 *argL) { V128 r; argD->w64[1] = r.w64[1] ^ argL->w64[1]; }