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From: "pinskia at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug target/106818] riscv produces bad low_sum while doing expansion of strict aligned stores/load Date: Fri, 21 Oct 2022 16:31:05 +0000 [thread overview] Message-ID: <bug-106818-4-yruOtyF3WO@http.gcc.gnu.org/bugzilla/> (raw) In-Reply-To: <bug-106818-4@http.gcc.gnu.org/bugzilla/> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106818 Andrew Pinski <pinskia at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Last reconfirmed| |2022-10-21 Status|UNCONFIRMED |NEW Summary|code is genereated |riscv produces bad low_sum |differently with or without |while doing expansion of |'extern' |strict aligned stores/load Component|middle-end |target Ever confirmed|0 |1 Keywords|missed-optimization |wrong-code --- Comment #11 from Andrew Pinski <pinskia at gcc dot gnu.org> --- So on aarch64 with -O3 -mstrict-align we produce: adrp x1, array add x0, x1, :lo12:array mov w2, 10 strb w2, [x1, #:lo12:array] strb wzr, [x0, 1] strb wzr, [x0, 2] strb wzr, [x0, 3] PowerPC has a similar output as aarch64 here too. Which means this is a target issue where low_sum is being combined with the add when it should not be. Confirmed for riscv. It happens at expand time: (insn 15 14 16 (set (mem/c:QI (lo_sum:DI (reg:DI 72) (symbol_ref:DI ("array") [flags 0xc4] <var_decl 0x7f347a4c51b0 array>)) [1 MEM[(struct sss_t *)&array].i+0 S1 A8]) (reg:QI 78)) "/app/example.cpp":10:10 -1 (nil)) (insn 16 15 17 (set (reg:DI 80) (zero_extend:DI (mem/c:QI (lo_sum:DI (reg:DI 72) (const:DI (plus:DI (symbol_ref:DI ("array") [flags 0xc4] <var_decl 0x7f347a4c51b0 array>) (const_int 1 [0x1])))) [1 MEM[(struct sss_t *)&array].i+1 S1 A8]))) "/app/example.cpp":10:10 -1 (nil)) Note the alignment is causing the difference in doing the expansion or one store but then the wrong code is due to the backend expansion of the address incorrectly. ARM64 (and powerpc) expansion produces: (insn 18 17 19 (set (reg:QI 101) (mem/c:QI (plus:DI (reg/f:DI 92) (const_int 1 [0x1])) [1 MEM[(struct sss_t *)&array].i+1 S1 A8])) "/app/example.cpp":10:10 -1 (nil)) Notice the 92 rather than the low_sum part.
next prev parent reply other threads:[~2022-10-21 16:31 UTC|newest] Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top 2022-09-02 19:26 [Bug c/106818] New: code is genereated differently with or without 'extern' pangbw at gmail dot com 2022-09-02 19:28 ` [Bug c/106818] " pangbw at gmail dot com 2022-09-02 19:37 ` pinskia at gcc dot gnu.org 2022-09-02 19:38 ` [Bug middle-end/106818] " pinskia at gcc dot gnu.org 2022-09-02 20:03 ` palmer at gcc dot gnu.org 2022-09-02 22:29 ` pangbw at gmail dot com 2022-09-02 22:33 ` pangbw at gmail dot com 2022-09-02 22:37 ` pinskia at gcc dot gnu.org 2022-09-02 23:59 ` palmer at gcc dot gnu.org 2022-09-05 10:15 ` rguenth at gcc dot gnu.org 2022-10-21 16:22 ` pinskia at gcc dot gnu.org 2022-10-21 16:31 ` pinskia at gcc dot gnu.org [this message] 2022-10-21 16:33 ` [Bug target/106818] riscv produces bad low_sum while doing expansion of strict aligned stores/load pinskia at gcc dot gnu.org 2023-11-29 18:45 ` pinskia at gcc dot gnu.org
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