public inbox for gcc-bugs@sourceware.org help / color / mirror / Atom feed
* [Bug rtl-optimization/100377] New: needless stack adjustment when passing struct in register @ 2021-05-01 19:20 luc.vanoostenryck at gmail dot com 2021-05-01 20:59 ` [Bug rtl-optimization/100377] " pinskia at gcc dot gnu.org ` (3 more replies) 0 siblings, 4 replies; 5+ messages in thread From: luc.vanoostenryck at gmail dot com @ 2021-05-01 19:20 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100377 Bug ID: 100377 Summary: needless stack adjustment when passing struct in register Product: gcc Version: 12.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: rtl-optimization Assignee: unassigned at gcc dot gnu.org Reporter: luc.vanoostenryck at gmail dot com Target Milestone: --- Created attachment 50726 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=50726&action=edit testcases When compiling with optimization for example -O2), the following code: struct sb { signed char a; char b; short y[3]; }; struct ub { unsigned char a; char b; short y[3]; }; int fsb(struct sb s) { return s.a; } int fub(struct ub s) { return s.a; } produces the following assembly code on arm64: fsb: sub sp, sp, #16 sxtb w0, w0 add sp, sp, 16 ret fub: sub sp, sp, #16 and w0, w0, 255 add sp, sp, 16 ret the following on mips64: fsb: daddiu $sp,$sp,-16 dsll $2,$4,56 dsra $2,$2,56 j $31 daddiu $sp,$sp,16 fub: daddiu $sp,$sp,-16 andi $2,$4,0xff j $31 daddiu $sp,$sp,16 the following on riscv64: fsb: addi sp,sp,-16 slli a0,a0,24 srai a0,a0,24 addi sp,sp,16 jr ra fub: addi sp,sp,-16 andi a0,a0,0xff addi sp,sp,16 jr ra OTOH, things seems OK on ppc64: fsb: extsb 3,3 blr fub: rlwinm 3,3,0,0xff blr and x86_64: fsb: movsx eax, dil ret fub: movzx eax, dil ret Similar problems happen on 32-bit platforms too. For example on arm32, the following code: struct ub32 { unsigned char a; char b; short y[1]; }; int fub32(struct ub32 s) { return s.a; } produces: fub32: sub sp, sp, #8 uxtb r0, r0 add sp, sp, #8 bx lr All these seem to happen on all versions. See https://gcc.godbolt.org/z/x9zc1EnYn Note: similar PRs exist but reported for x86_64 only ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug rtl-optimization/100377] needless stack adjustment when passing struct in register 2021-05-01 19:20 [Bug rtl-optimization/100377] New: needless stack adjustment when passing struct in register luc.vanoostenryck at gmail dot com @ 2021-05-01 20:59 ` pinskia at gcc dot gnu.org 2021-05-01 21:00 ` pinskia at gcc dot gnu.org ` (2 subsequent siblings) 3 siblings, 0 replies; 5+ messages in thread From: pinskia at gcc dot gnu.org @ 2021-05-01 20:59 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100377 Andrew Pinski <pinskia at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Depends on| |94173, 90216 Severity|normal |enhancement --- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> --- (In reply to Luc Van Oostenryck from comment #0) > > Note: similar PRs exist but reported for x86_64 only Not true. PR 94173, PR 90216. I thought there was one which I filed which is much older than those but I can't find it. Referenced Bugs: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90216 [Bug 90216] Stack Pointer decrementing even when not loading extra data to stack. https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94173 [Bug 94173] [RISCV] Superfluous stackpointer manipulation ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug rtl-optimization/100377] needless stack adjustment when passing struct in register 2021-05-01 19:20 [Bug rtl-optimization/100377] New: needless stack adjustment when passing struct in register luc.vanoostenryck at gmail dot com 2021-05-01 20:59 ` [Bug rtl-optimization/100377] " pinskia at gcc dot gnu.org @ 2021-05-01 21:00 ` pinskia at gcc dot gnu.org 2021-05-02 14:05 ` luc.vanoostenryck at gmail dot com 2021-05-03 8:02 ` rguenth at gcc dot gnu.org 3 siblings, 0 replies; 5+ messages in thread From: pinskia at gcc dot gnu.org @ 2021-05-01 21:00 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100377 --- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> --- OTOH, things seems OK on ppc64: and x86_64: Because both of those have redzones in their stack ABI. ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug rtl-optimization/100377] needless stack adjustment when passing struct in register 2021-05-01 19:20 [Bug rtl-optimization/100377] New: needless stack adjustment when passing struct in register luc.vanoostenryck at gmail dot com 2021-05-01 20:59 ` [Bug rtl-optimization/100377] " pinskia at gcc dot gnu.org 2021-05-01 21:00 ` pinskia at gcc dot gnu.org @ 2021-05-02 14:05 ` luc.vanoostenryck at gmail dot com 2021-05-03 8:02 ` rguenth at gcc dot gnu.org 3 siblings, 0 replies; 5+ messages in thread From: luc.vanoostenryck at gmail dot com @ 2021-05-02 14:05 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100377 --- Comment #3 from Luc Van Oostenryck <luc.vanoostenryck at gmail dot com> --- > I thought there was one which I filed which is much older than those but I > can't find it. Probably also related to PR36409 and PR49157 ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug rtl-optimization/100377] needless stack adjustment when passing struct in register 2021-05-01 19:20 [Bug rtl-optimization/100377] New: needless stack adjustment when passing struct in register luc.vanoostenryck at gmail dot com ` (2 preceding siblings ...) 2021-05-02 14:05 ` luc.vanoostenryck at gmail dot com @ 2021-05-03 8:02 ` rguenth at gcc dot gnu.org 3 siblings, 0 replies; 5+ messages in thread From: rguenth at gcc dot gnu.org @ 2021-05-03 8:02 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100377 Richard Biener <rguenth at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Keywords| |missed-optimization --- Comment #4 from Richard Biener <rguenth at gcc dot gnu.org> --- I think there are indeed plenty of dups. ^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2021-05-03 8:02 UTC | newest] Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2021-05-01 19:20 [Bug rtl-optimization/100377] New: needless stack adjustment when passing struct in register luc.vanoostenryck at gmail dot com 2021-05-01 20:59 ` [Bug rtl-optimization/100377] " pinskia at gcc dot gnu.org 2021-05-01 21:00 ` pinskia at gcc dot gnu.org 2021-05-02 14:05 ` luc.vanoostenryck at gmail dot com 2021-05-03 8:02 ` rguenth at gcc dot gnu.org
This is a public inbox, see mirroring instructions for how to clone and mirror all data and code used for this inbox; as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).