On Fri, Nov 17, 2023 at 12:36:01PM -0600, Gustavo A. R. Silva wrote: > Hi all, > > I'm trying to fix the following -Wstringop-overflow warnings, and I'd like > to get your feedback on this, please: > > In function 'do_byte_reverse', > inlined from 'do_vec_store' at > /home/gus/linux/arch/powerpc/lib/sstep.c:722:3, > inlined from 'emulate_loadstore' at > /home/gus/linux/arch/powerpc/lib/sstep.c:3510:9: > arch/powerpc/lib/sstep.c:287:23: error: writing 8 bytes into a region of size > 0 [-Werror=stringop-overflow=] > 287 | up[3] = tmp; > | ~~~~~~^~~~~ > arch/powerpc/lib/sstep.c: In function 'emulate_loadstore': > arch/powerpc/lib/sstep.c:708:11: note: at offset [24, 39] into destination > object 'u' of size 16 > 708 | } u; > | ^ > In function 'do_byte_reverse', > inlined from 'do_vec_store' at > /home/gus/linux/arch/powerpc/lib/sstep.c:722:3, > inlined from 'emulate_loadstore' at > /home/gus/linux/arch/powerpc/lib/sstep.c:3510:9: > arch/powerpc/lib/sstep.c:289:23: error: writing 8 bytes into a region of size > 0 [-Werror=stringop-overflow=] > 289 | up[2] = byterev_8(up[1]); > | ~~~~~~^~~~~~~~~~~~~~~~~~ > arch/powerpc/lib/sstep.c: In function 'emulate_loadstore': > arch/powerpc/lib/sstep.c:708:11: note: at offset 16 into destination object > 'u' of size 16 > 708 | } u; > | ^ > In function 'do_byte_reverse', > inlined from 'do_vec_load' at > /home/gus/linux/arch/powerpc/lib/sstep.c:691:3, > inlined from 'emulate_loadstore' at > /home/gus/linux/arch/powerpc/lib/sstep.c:3439:9: > arch/powerpc/lib/sstep.c:287:23: error: writing 8 bytes into a region of size > 0 [-Werror=stringop-overflow=] > 287 | up[3] = tmp; > | ~~~~~~^~~~~ > arch/powerpc/lib/sstep.c: In function 'emulate_loadstore': > arch/powerpc/lib/sstep.c:681:11: note: at offset [24, 39] into destination > object 'u' of size 16 > 681 | } u = {}; > | ^ > arch/powerpc/lib/sstep.c:681:11: note: at offset [24, 39] into destination > object 'u' of size 16 > arch/powerpc/lib/sstep.c:681:11: note: at offset [24, 39] into destination > object 'u' of size 16 > > The origing of the issue seems to be the following calls to function > `do_vec_store()`, when > `size > 16`, or more precisely when `size == 32` > > arch/powerpc/lib/sstep.c: > 3436 case LOAD_VMX: > 3437 if (!(regs->msr & MSR_PR) && !(regs->msr & MSR_VEC)) > 3438 return 0; > 3439 err = do_vec_load(op->reg, ea, size, regs, cross_endian); > 3440 break; > ... > 3507 case STORE_VMX: > 3508 if (!(regs->msr & MSR_PR) && !(regs->msr & MSR_VEC)) > 3509 return 0; > 3510 err = do_vec_store(op->reg, ea, size, regs, > cross_endian); > 3511 break;
LOAD_VMX and STORE_VMX are set in analyse_instr() and size does not exceed 16. So, the warning looks incorrect to me. - Naveen