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From: "olegendo at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug target/52628] New: SH Target: Inefficient shift by T bit result Date: Mon, 19 Mar 2012 23:42:00 -0000 [thread overview] Message-ID: <bug-52628-4@http.gcc.gnu.org/bugzilla/> (raw) http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52628 Bug #: 52628 Summary: SH Target: Inefficient shift by T bit result Classification: Unclassified Product: gcc Version: 4.8.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: target AssignedTo: unassigned@gcc.gnu.org ReportedBy: olegendo@gcc.gnu.org Target: sh*-*-* int test_01 (int a, int b, int c) { return c << (a > b ? 1 : 0); } -m4 -O2: cmp/gt r5,r4 mov r6,r0 movt r1 rts shld r1,r0 better: cmp/gt r5,r4 bf 0f add r6,r6 ! do not use shll because of T bit usage in shll 0: rts mov r6,r0 int test_02 (int a, int b, int c) { return c << (a > b ? 2 : 0); } -m4 -O2: cmp/gt r5,r4 mov r6,r0 movt r1 add r1,r1 rts shld r1,r0 better: cmp/gt r5,r4 bf 0f shll2 r6 0: rts mov r6,r0 The same goes for other shift amounts like 8 and 16. On SH4 the zero-displacement conditional branch code should be faster.
next reply other threads:[~2012-03-19 21:50 UTC|newest] Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top 2012-03-19 23:42 olegendo at gcc dot gnu.org [this message] 2014-05-10 13:49 ` [Bug target/52628] " olegendo at gcc dot gnu.org 2015-09-27 4:29 ` olegendo at gcc dot gnu.org 2023-07-22 3:06 ` pinskia at gcc dot gnu.org
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