Author: mjg Date: Thu Sep 27 15:27:53 2018 New Revision: 338968 URL: https://svnweb.freebsd.org/changeset/base/338968
Log: amd64: mostly depessimize copystr - remove a forward branch in the common case - replace xchg + lodsb/stosb loop with simple movs A simple test on Intel(R) Core(TM) i7-4600U CPU @ 2.10GH copying /foo/bar/baz in a loop goes from 295715863 ops/s to 465807408. Further changes are pending. Reviewed by: kib Approved by: re (gjb) Differential Revision: https://reviews.freebsd.org/D17281 Modified: head/sys/amd64/amd64/support.S Modified: head/sys/amd64/amd64/support.S ============================================================================== --- head/sys/amd64/amd64/support.S Thu Sep 27 15:24:16 2018 (r338967) +++ head/sys/amd64/amd64/support.S Thu Sep 27 15:27:53 2018 (r338968) @@ -1122,34 +1122,33 @@ ENTRY(copystr) PUSH_FRAME_POINTER movq %rdx,%r8 /* %r8 = maxlen */ - xchgq %rdi,%rsi - incq %rdx + incq %rdx 1: decq %rdx jz 4f - lodsb - stosb - orb %al,%al + movb (%rdi),%al + movb %al,(%rsi) + incq %rsi + incq %rdi + testb %al,%al jnz 1b /* Success -- 0 byte reached */ decq %rdx xorl %eax,%eax - jmp 6f -4: - /* rdx is zero -- return ENAMETOOLONG */ - movq $ENAMETOOLONG,%rax - -6: - +2: testq %rcx,%rcx - jz 7f + jz 3f /* set *lencopied and return %rax */ subq %rdx,%r8 movq %r8,(%rcx) -7: +3: POP_FRAME_POINTER ret +4: + /* rdx is zero -- return ENAMETOOLONG */ + movl $ENAMETOOLONG,%eax + jmp 2b END(copystr) /* _______________________________________________ [email protected] mailing list https://lists.freebsd.org/mailman/listinfo/svn-src-all To unsubscribe, send any mail to "[email protected]"
