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From: "miro.kropacek at gmail dot com" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug c/113779] New: Very inefficient m68k code generated for simple copy loop Date: Mon, 05 Feb 2024 21:07:56 +0000 [thread overview] Message-ID: <bug-113779-4@http.gcc.gnu.org/bugzilla/> (raw) https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113779 Bug ID: 113779 Summary: Very inefficient m68k code generated for simple copy loop Product: gcc Version: 13.2.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c Assignee: unassigned at gcc dot gnu.org Reporter: miro.kropacek at gmail dot com Target Milestone: --- Even as simple loop as this: void f(const long* src, long* dst, int count) { for (int i = 0; i < count; i++) { *dst++ = *src++; *dst++ = *src++; *dst++ = *src++; *dst++ = *src++; *dst++ = *src++; *dst++ = *src++; *dst++ = *src++; *dst++ = *src++; *dst++ = *src++; *dst++ = *src++; *dst++ = *src++; *dst++ = *src++; *dst++ = *src++; *dst++ = *src++; *dst++ = *src++; *dst++ = *src++; } } is compiled to: #NO_APP .file "test.c" .text .align 2 .globl f .type f, @function f: move.l 4(%sp),%a0 move.l 8(%sp),%a1 move.l 12(%sp),%d1 jle .L1 clr.l %d0 .L3: move.l (%a0),(%a1) move.l 4(%a0),4(%a1) move.l 8(%a0),8(%a1) move.l 12(%a0),12(%a1) move.l 16(%a0),16(%a1) move.l 20(%a0),20(%a1) move.l 24(%a0),24(%a1) move.l 28(%a0),28(%a1) move.l 32(%a0),32(%a1) move.l 36(%a0),36(%a1) move.l 40(%a0),40(%a1) move.l 44(%a0),44(%a1) move.l 48(%a0),48(%a1) move.l 52(%a0),52(%a1) move.l 56(%a0),56(%a1) add.w #64,%a0 add.w #64,%a1 move.l -4(%a0),-4(%a1) addq.l #1,%d0 cmp.l %d1,%d0 jne .L3 .L1: rts .size f, .-f .ident "GCC: (GNU) 13.2.0" This has been like this for ages: gcc 4.6.4, gcc 7.2.0 and lately gcc 13.2.0 ... the last gcc where it was reported to transform into move.l (a0)+,(a1)+ was gcc 2.95 and gcc 3.x. So what's the catch here? Why gcc hates move.l (ax)+,(ay)+ so much? Tested on m68k-elf-gcc -O2 -fomit-frame-pointer -m68020-60.
next reply other threads:[~2024-02-05 21:07 UTC|newest] Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top 2024-02-05 21:07 miro.kropacek at gmail dot com [this message] 2024-02-05 21:20 ` [Bug target/113779] " pinskia at gcc dot gnu.org 2024-02-06 7:58 ` rguenth at gcc dot gnu.org 2024-02-06 8:16 ` miro.kropacek at gmail dot com 2024-02-06 12:47 ` mikpelinux at gmail dot com 2024-02-06 12:58 ` miro.kropacek at gmail dot com 2024-02-06 13:14 ` rguenth at gcc dot gnu.org 2024-02-17 0:39 ` hp at gcc dot gnu.org
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