Date: Sun, 16 Sep 2018 19:28:27 +0000 (UTC) From: Mateusz Guzik <mjg@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r338700 - head/sys/amd64/amd64 Message-ID: <201809161928.w8GJSRxn022096@repo.freebsd.org>
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Author: mjg Date: Sun Sep 16 19:28:27 2018 New Revision: 338700 URL: https://svnweb.freebsd.org/changeset/base/338700 Log: amd64: tidy up kernel memmove There is no need to use %rax for temporary values and avoiding doing so shortens the func. Handle the explicit 'check for tail' depessimisization for backwards copying. This reduces the diff against userspace. Approved by: re (kib) Modified: head/sys/amd64/amd64/support.S Modified: head/sys/amd64/amd64/support.S ============================================================================== --- head/sys/amd64/amd64/support.S Sun Sep 16 18:36:42 2018 (r338699) +++ head/sys/amd64/amd64/support.S Sun Sep 16 19:28:27 2018 (r338700) @@ -108,12 +108,12 @@ END(sse2_pagezero) */ ENTRY(memmove_std) PUSH_FRAME_POINTER - movq %rdi,%r9 + movq %rdi,%rax movq %rdx,%rcx - movq %rdi,%rax - subq %rsi,%rax - cmpq %rcx,%rax /* overlapping && src < dst? */ + movq %rdi,%r8 + subq %rsi,%r8 + cmpq %rcx,%r8 /* overlapping && src < dst? */ jb 1f shrq $3,%rcx /* copy by 64-bit words */ @@ -128,7 +128,6 @@ ENTRY(memmove_std) 2: rep movsb - movq %r9,%rax POP_FRAME_POINTER ret @@ -140,8 +139,10 @@ ENTRY(memmove_std) decq %rsi andq $7,%rcx /* any fractional bytes? */ std + jne 3f rep movsb +3: movq %rdx,%rcx /* copy remainder by 32-bit words */ shrq $3,%rcx subq $7,%rsi @@ -149,24 +150,22 @@ ENTRY(memmove_std) rep movsq cld - movq %r9,%rax POP_FRAME_POINTER ret END(memmove_std) ENTRY(memmove_erms) PUSH_FRAME_POINTER - movq %rdi,%r9 + movq %rdi,%rax movq %rdx,%rcx - movq %rdi,%rax - subq %rsi,%rax - cmpq %rcx,%rax /* overlapping && src < dst? */ + movq %rdi,%r8 + subq %rsi,%r8 + cmpq %rcx,%r8 /* overlapping && src < dst? */ jb 1f rep movsb - movq %r9,%rax POP_FRAME_POINTER ret @@ -179,7 +178,6 @@ ENTRY(memmove_erms) rep movsb cld - movq %r9,%rax POP_FRAME_POINTER ret END(memmove_erms)
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