Cygwin: x86_64: import memchr.S from NetBSD

Signed-off-by: Corinna Vinschen <corinna@vinschen.de>

diff --git a/winsup/cygwin/Makefile.am b/winsup/cygwin/Makefile.am
index 167be8149a3c5757fa4ad2d93e2374cd8a745fbe..f63e8959141b758426134b76c9c28e1856c08465 100644 (file)
--- a/winsup/cygwin/Makefile.am
+++ b/winsup/cygwin/Makefile.am
@@ -52,8 +52,9 @@ TEST_LIB_NAME=libcygwin0.a
 # These objects are included directly into the import library
 if TARGET_X86_64
 TARGET_FILES= \
-       x86_64/memcpy.s \
-       x86_64/memset.s
+       x86_64/memchr.S \
+       x86_64/memcpy.S \
+       x86_64/memset.S
 endif
 
 LIB_FILES= \

diff --git a/winsup/cygwin/x86_64/memchr.S b/winsup/cygwin/x86_64/memchr.S
new file mode 100644 (file)
index 0000000..34fd5fe
--- /dev/null
+++ b/winsup/cygwin/x86_64/memchr.S
@@ -0,0 +1,109 @@
+/*     $NetBSD: memchr.S,v 1.6 2014/03/22 19:16:34 jakllsch Exp $      */
+
+/*-
+ * Copyright (c) 2009 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * This code is derived from software contributed to The NetBSD Foundation
+ * by David Laight.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <machine/asm.h>
+
+#if defined(LIBC_SCCS)
+       RCSID("$NetBSD: memchr.S,v 1.6 2014/03/22 19:16:34 jakllsch Exp $")
+#endif
+
+/*
+ * The instruction sequences used try to avoid data dependencies
+ * between adjacent instructions (to allow parallel execution).
+ * The 'imul' for %r9 could be put into the delay following the
+ * memory read (ie inside the loop) at no obvious cost - except
+ * that the loop is currently exactly 32 bytes - 2 fetch blocks!.
+ *
+ * I don't think aligning any of the other branch targets is useful.
+ */
+
+ENTRY3(memchr)
+       movabsq $0x0101010101010101,%r8
+       lea     (%rdi,%rdx),%r10        /* limit of buffer to scan */
+       movzbq  %sil,%rsi       /* mask high bits! */
+
+       /* 'directpath' imuls can execute 3 at a time ... (amd) */
+       imul    %r8,%rsi        /* search byte replicated in word */
+       imul    $0x80,%r8,%r9   /* 0x8080808080808080 */
+       test    $7,%dil
+       jnz     20f             /* jump if misaligned */
+       jmp     1f              /* jump to avoid 4 nops (13 bytes) in gap */
+
+       _ALIGN_TEXT             /* entire loop now in 32 aligned bytes */
+1:
+       cmpq    %r10,%rdi       /* end of buffer ? */
+       jae     30f             /* jump if so */
+
+       movq    (%rdi),%rax     /* value to check */
+       addq    $8,%rdi
+       xorq    %rsi,%rax       /* now looking for zeros */
+2:
+       mov     %rax,%rcx
+       subq    %r8,%rax        /* x - 0x01 */
+       not     %rcx
+       andq    %r9,%rax        /* (x - 0x01) & 0x80 */
+       andq    %rcx,%rax       /* ((x - 0x01) & 0x80) & ~x */
+       je      1b              /* jump if not found */
+
+/* Found byte in word, get its address */
+       bsf     %rax,%rax
+       shr     $3,%eax
+       lea     -8(%rax,%rdi),%rax
+       cmpq    %r10,%rax       /* need to check not beyond buffer */
+       jae     30f
+       rep
+       ret                     /* amd - no ret after jmp */
+
+/* Input misaligned, read aligned and make low bytes invalid */
+20:
+       mov     %dil,%cl        /* misalignment amount 1..7 (+high bits )*/
+       and     $~7,%dil        /* %rdi now start of word */
+       test    %rdx,%rdx       /* zero length, don't read */
+       jz      30f
+
+       neg     %cl             /* 7..1 (+high bits) */
+       mov     (%rdi),%rax     /* word containing first byte */
+       addq    $8,%rdi
+       and     $7,%cl          /* 7..1 */
+
+       mov     %r8,%r11        /* any value with bits in each byte */
+       shl     $3,%cl          /* 56..8 */
+       xorq    %rsi,%rax       /* now looking for zeros */
+
+       /* Set low bytes non-zero */
+       shr     %cl,%r11        /* non-zero in unwanted bytes */
+       or      %r11,%rax       /* low bytes now set */
+       jmp     2b
+
+/* Not found */
+30:    xorq    %rax,%rax
+       ret
+END(memchr)