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From: "ktkachov at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug tree-optimization/97984] New: [10/11 Regression] Worse code for -O3 than -O2 on aarch64 vector multiply-add Date: Wed, 25 Nov 2020 11:49:05 +0000 [thread overview] Message-ID: <bug-97984-4@http.gcc.gnu.org/bugzilla/> (raw) https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97984 Bug ID: 97984 Summary: [10/11 Regression] Worse code for -O3 than -O2 on aarch64 vector multiply-add Product: gcc Version: unknown Status: UNCONFIRMED Keywords: missed-optimization Severity: normal Priority: P3 Component: tree-optimization Assignee: unassigned at gcc dot gnu.org Reporter: ktkachov at gcc dot gnu.org Target Milestone: --- Target: aarch64 The code: void x (long * __restrict a, long * __restrict b) { a[0] *= b[0]; a[1] *= b[1]; a[0] += b[0]; a[1] += b[1]; } at -O2 generates: x: ldp x4, x3, [x0] ldp x2, x1, [x1] madd x2, x2, x4, x2 madd x1, x1, x3, x1 stp x2, x1, [x0] ret whereas at -O3 it does: x: ldp x2, x3, [x0] ldr x4, [x1] ldr q1, [x1] mul x2, x2, x4 ldr x4, [x1, 8] fmov d0, x2 ins v0.d[1], x3 mul x1, x3, x4 ins v0.d[1], x1 add v0.2d, v0.2d, v1.2d str q0, [x0] ret which is clearly inferior. GCC 9 used to generate the good code for both -O2 and -O3
next reply other threads:[~2020-11-25 11:49 UTC|newest] Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-11-25 11:49 ktkachov at gcc dot gnu.org [this message] 2020-11-25 12:59 ` [Bug tree-optimization/97984] " rguenth at gcc dot gnu.org 2021-01-14 9:47 ` [Bug target/97984] " rguenth at gcc dot gnu.org 2021-04-08 12:02 ` rguenth at gcc dot gnu.org 2021-11-22 0:49 ` pinskia at gcc dot gnu.org 2021-12-08 14:24 ` marxin at gcc dot gnu.org 2021-12-08 19:51 ` pinskia at gcc dot gnu.org 2021-12-09 10:05 ` marxin at gcc dot gnu.org 2022-06-28 10:42 ` jakub at gcc dot gnu.org 2023-07-07 10:38 ` [Bug target/97984] [11 " rguenth at gcc dot gnu.org
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