/*
* Copyright (c) 2005-2006 Apple Computer, Inc. All rights reserved.
*
* @APPLE_OSREFERENCE_LICENSE_HEADER_START@
*
* This file contains Original Code and/or Modifications of Original Code
* as defined in and that are subject to the Apple Public Source License
* Version 2.0 (the 'License'). You may not use this file except in
* compliance with the License. The rights granted to you under the License
* may not be used to create, or enable the creation or redistribution of,
* unlawful or unlicensed copies of an Apple operating system, or to
* circumvent, violate, or enable the circumvention or violation of, any
* terms of an Apple operating system software license agreement.
*
* Please obtain a copy of the License at
* http://www.opensource.apple.com/apsl/ and read it before using this file.
*
* The Original Code and all software distributed under the License are
* distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
* EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
* INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
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*/
#include <machine/cpu_capabilities.h>
#include <machine/commpage.h>
/*
* Bzero, tuned for Pentium-M class processors with SSE2
* and 64-byte cache lines.
*
* This routine is also used for memset(p,0,n), which is a common case
* since gcc sometimes silently maps bzero() into memset(). As a result,
* we always load the original ptr into %eax before returning.
*/
#define kShort 80 // too short to bother with SSE (must be >=80)
#define kVeryLong (1024*1024)
// void bzero(void *b, size_t len)COMMPAGE_FUNCTION_START(bzero_sse2, 32, 5)
pushl %ebp // set up a frame for backtraces
movl %esp,%ebp
pushl %edi
movl 8(%ebp),%edi // get ptr
movl 12(%ebp),%edx // get length
xorl %eax,%eax // set fill data to 0
cmpl $(kShort),%edx // long enough for SSE?
jg LNotShort // yes
// Here for short operands or the end of long ones.
// %edx = length
// %edi = ptr
// %eax = zero
Lshort:
cmpl $16,%edx // long enough to word align?
jge 3f // yes
test %edx,%edx // length==0?
jz 6f
1:
movb %al,(%edi) // zero a byte
inc %edi
dec %edx
jnz 1b
jmp 6f
2:
movb %al,(%edi) // zero a byte
inc %edi
dec %edx
3:
test $3,%edi // is ptr doubleword aligned?
jnz 2b // no
movl %edx,%ecx // copy length
shrl $2,%edx // #doublewords to store
4:
movl %eax,(%edi) // zero an aligned doubleword
addl $4,%edi
dec %edx
jnz 4b
andl $3,%ecx // mask down to #bytes at end (0..3)
jz 6f // none
5:
movb %al,(%edi) // zero a byte
inc %edi
dec %ecx
jnz 5b
6:
movl 8(%ebp),%eax // get return value in case this was a call of memset()
popl %edi
popl %ebp
ret
// We will be using SSE, so align ptr.
LNotShort:
movl %edi,%ecx
negl %ecx
andl $15,%ecx // mask down to #bytes to 16-byte align
jz LDestAligned // already aligned
subl %ecx,%edx // decrement length
0: // loop storing bytes to align the ptr
movb %al,(%edi) // pack in a byte
inc %edi
dec %ecx
jnz 0b
// Destination is now 16-byte aligned. Prepare to loop over 64-byte chunks.
// %edx = length
// %edi = ptr
// %eax = zero
LDestAligned:
movl %edx,%ecx
andl $63,%edx // mask down to residual length (0..63)
andl $-64,%ecx // get #bytes we will zero in this loop
pxor %xmm0,%xmm0 // zero an SSE register
addl %ecx,%edi // increment ptr by length to move
cmpl $(kVeryLong),%ecx // long enough to justify non-temporal stores?
jae LVeryLong // yes
negl %ecx // negate length to move
jmp 1f
// Loop over 64-byte chunks, storing into cache.
.align 4,0x90 // keep inner loops 16-byte aligned
1:
movdqa %xmm0,(%edi,%ecx)
movdqa %xmm0,16(%edi,%ecx)
movdqa %xmm0,32(%edi,%ecx)
movdqa %xmm0,48(%edi,%ecx)
addl $64,%ecx
jne 1b
jmp Lshort
// Very long operands: use non-temporal stores to bypass cache.
LVeryLong:
negl %ecx // negate length to move
jmp 1f
.align 4,0x90 // keep inner loops 16-byte aligned
1:
movntdq %xmm0,(%edi,%ecx)
movntdq %xmm0,16(%edi,%ecx)
movntdq %xmm0,32(%edi,%ecx)
movntdq %xmm0,48(%edi,%ecx)
addl $64,%ecx
jne 1b
sfence // required by non-temporal stores
jmp Lshort
COMMPAGE_DESCRIPTOR(bzero_sse2,_COMM_PAGE_BZERO,kHasSSE2,kHasSSE4_2)