Libc-825.26.tar.gz

[apple/libc.git] / x86_64 / string / memset.s

/*
 * Copyright (c) 2005 Apple Computer, Inc. All rights reserved.
 *
 * @APPLE_LICENSE_HEADER_START@
 *
 * The contents of this file constitute Original Code as defined in and
 * are subject to the Apple Public Source License Version 1.1 (the
 * "License").  You may not use this file except in compliance with the
 * License.  Please obtain a copy of the License at
 * http://www.apple.com/publicsource and read it before using this file.
 *
 * This 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,
 * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT.  Please see the
 * License for the specific language governing rights and limitations
 * under the License.
 *
 * @APPLE_LICENSE_HEADER_END@
 */

#include <machine/cpu_capabilities.h>


/* This file contains the following functions:
 *
 *	void *memset(void *b, int c, size_t len);
 *	void memset_pattern4(void *b, const void *c4, size_t len);
 *	void memset_pattern8(void *b, const void *c8, size_t len);
 *	void memset_pattern16(void *b, const void *c16, size_t len);
 *
 * Calls of memset() with c==0 are routed to the bzero() routine.  Most of the
 * others go to _memset_pattern, which is entered as follows:
 *	%rdi = ptr to memory to set (aligned)
 *	%edx = length (which can be short, though we bias in favor of long operands)
 *	%xmm0 = the pattern to store
 * Return conditions:
 *	%eax, %edi, %esi, %ecx, and %edx all trashed
 *
 * NB: we avoid "stos" family of instructions (stosl, stosb), as they are very slow
 * on P4s and probably other processors.
 */

#define kShort	255			// for nonzero memset(), too short for commpage


	.text
	.globl	_memset
	.align	2
_memset:				// void *memset(void *b, int c, size_t len);
	andl	$0xFF,%esi		// (c==0) ?
	jnz		LNonzero		// not a bzero

	movq	%rdx,%rsi		// put count where bzero() expects it
	jmp		_bzero			// enter _bzero


// Handle memset of a nonzero value.

LNonzero:
	movq	%rdi,%r8		// preserve the original pointer so we can return it
	movl	%esi,%eax		// replicate byte in %esi into all four bytes
	shll	$8,%esi
	orl		%esi,%eax
	movl	%eax,%esi
	shll	$16,%esi
	orl		%esi,%eax		// now %eax has "c" in all 4 bytes
	cmpq	$(kShort),%rdx		// is operand too short for SSE?
	ja		LCallCommpage		// no

	// Nonzero memset() too short to call commpage.
	//	%eax = replicated 4-byte pattern
	//	%rdi = ptr
	//	%edx = length (<= kShort)

	cmpl	$16,%edx		// long enough to word align?
	jge	3f			// yes
	test	%edx,%edx		// length==0?
	jz	6f
1:
	movb	%al,(%rdi)		// pack in a byte
	addq	$1,%rdi
	subl	$1,%edx
	jnz	1b
	jmp	6f
2:
	movb	%al,(%rdi)		// pack in a byte
	addq	$1,%rdi
	subl	$1,%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,(%rdi)		// store aligned doubleword
	addq	$4,%rdi
	subl	$1,%edx
	jnz	4b
	andl	$3,%ecx			// any leftover bytes?
	jz	6f			// no
5:
	movb	%al,(%rdi)		// pack in a byte
	addq	$1,%rdi
	subl	$1,%ecx
	jnz	5b
6:
	movq	%r8,%rax		// get return value (ie, original ptr)
	ret

	// Nonzero memset() is long enough to call commpage.
	//	%eax = replicated 4-byte pattern
	//	%rdi = ptr
	//	%rdx = length (> kShort)

LCallCommpage:
	movd	%eax,%xmm0		// move %eax to low 4 bytes of %xmm0
	pshufd	$(0x00),%xmm0,%xmm0	// replicate across the vector
	movq	%rdi,%rcx		// copy dest ptr
	negl	%ecx
	andl	$15,%ecx		// get #bytes to align ptr
	jz	2f			// skip if already aligned
	subq	%rcx,%rdx		// decrement length
1:
	movb	%al,(%rdi)		// pack in a byte
	addq	$1,%rdi
	subl	$1,%ecx
	jnz	1b
2:					// ptr aligned, length long enough to justify
	call	Lmemset_pattern	// call commpage to do the heavy lifting
	movq	%r8,%rax		// get return value (ie, original ptr)
	ret


	// Handle memset of a 16-byte pattern.

	.globl	_memset_pattern16
	.align	2, 0x90
_memset_pattern16:			// void memset_pattern16(void *b, const void *c16, size_t len);
	movdqu	(%rsi),%xmm0		// load the pattern
	jmp	LAlignPtr


	// Handle memset of an 8-byte pattern.

	.globl	_memset_pattern8
	.align	2, 0x90
_memset_pattern8:			// void memset_pattern8(void *b, const void *c8, size_t len);
	movq	(%rsi),%xmm0		// load pattern into low 8 bytes
	punpcklqdq %xmm0,%xmm0		// replicate into all 16
	jmp	LAlignPtr

	// Handle memset of a 4-byte pattern.

	.globl	_memset_pattern4
	.align	2, 0x90
_memset_pattern4:			// void memset_pattern4(void *b, const void *c4, size_t len);
	movd	(%rsi),%xmm0		// load pattern into low 4 bytes
	pshufd	$(0x00),%xmm0,%xmm0	// replicate the 4 bytes across the vector


	// Align ptr if necessary.  We must rotate the pattern right for each byte we
	// store while aligning the ptr.  Since there is no rotate instruction in SSE3,
	// we have to synthesize the rotates.
	//	%rdi = ptr
	//	%rdx = length
	//	%xmm0 = pattern

LAlignPtr:				// NB: can drop down to here!
	cmpq	$100,%rdx		// long enough to bother aligning ptr?
	movq	%rdi,%rcx		// copy ptr
	jb	LReady			// not long enough
	negl	%ecx
	andl	$15,%ecx		// get #bytes to align ptr
	jz	LReady			// already aligned
	subq	%rcx,%rdx		// adjust length

	test	$1,%cl			// 1-byte store required?
	movd	%xmm0,%eax		// get 4 low bytes in %eax
	jz	2f			// no
	movdqa	%xmm0,%xmm1		// copy pattern so we can shift in both directions
	movb	%al,(%rdi)		// pack in the low-order byte
	psrldq	$1,%xmm0		// shift pattern right 1 byte
	addq	$1,%rdi
	pslldq	$15,%xmm1		// shift pattern left 15 bytes
	shrl	$8,%eax			// in case 2-byte store is required
	por	%xmm1,%xmm0		// complete right rotate of pattern by 1 byte
2:
	test	$2,%cl			// 2-byte store required?
	jz	4f			// no
	psrldq	$2,%xmm0		// shift pattern down 2 bytes
	movw	%ax,(%rdi)		// pack in next two bytes
	pinsrw	$7,%eax,%xmm0		// insert low word of %eax into high word of %xmm0
	addq	$2,%rdi			// adjust ptr
4:
	test	$4,%cl			// 4-byte store required?
	jz	8f			// no
	movd	%xmm0,(%rdi)		// store low 4 bytes of %xmm0
	pshufd	$(0x39),%xmm0,%xmm0	// rotate %xmm0 right 4 bytes (mask == 00 11 10 01)
	addq	$4,%rdi			// adjust ptr
8:
	test	$8,%cl			// 8-byte store required?
	jz	LReady			// no
	movq	%xmm0,(%rdi)		// store low 8 bytes of %xmm0
	pshufd	$(0x4e),%xmm0,%xmm0	// rotate %xmm0 right 8 bytes (mask == 01 00 11 10)
	addq	$8,%rdi			// adjust ptr

	// Ptr is aligned if practical, we're ready to call commpage to do the heavy lifting.

LReady:
	call	Lmemset_pattern	// call commpage to do the heavy lifting
	ret


#define	kLShort		63
#define	kVeryLong	(1024*1024)

Lmemset_pattern:
	cmpq    $(kLShort),%rdx		// long enough to bother aligning?
	ja	LNotShort		// yes
	jmp	LShort			// no

	// Here for short operands or the end of long ones.
	//      %rdx = length (<= kLShort)
	//      %rdi = ptr (may not be not aligned)
	//      %xmm0 = pattern

LUnalignedStore16:
	movdqu	%xmm0,(%rdi)		// stuff in another 16 bytes
	subl	$16,%edx
	addq	$16,%rdi
LShort:	
	cmpl	$16,%edx		// room for another vector?
	jge	LUnalignedStore16	// yes
LLessThan16:				// here at end of copy with < 16 bytes remaining
	test	$8,%dl			// 8-byte store required?
	jz	2f			// no
	movq	%xmm0,(%rdi)		// pack in 8 low bytes
	psrldq	$8,%xmm0		// then shift vector down 8 bytes
	addq	$8,%rdi
2:
	test	$4,%dl			// 4-byte store required?
	jz	3f			// no
	movd	%xmm0,(%rdi)		// pack in 4 low bytes
	psrldq	$4,%xmm0		// then shift vector down 4 bytes
	addq	$4,%rdi
3:
	andl	$3,%edx			// more to go?
	jz	5f			// no
	movd	%xmm0,%eax		// move remainders out into %eax
4:					// loop on up to three bytes
	movb	%al,(%rdi)		// pack in next byte
	shrl	$8,%eax			// shift next byte into position
	incq	%rdi
	dec	%edx
	jnz	4b
5:	ret

// Long enough to justify aligning ptr.  Note that we have to rotate the
// pattern to account for any alignment.  We do this by doing two unaligned
// stores, and then an aligned load from the middle of the two stores.
// This will stall on store forwarding alignment mismatch, and the unaligned
// stores can be pretty slow too, but the alternatives aren't any better.
// Fortunately, in most cases our caller has already aligned the ptr.
//      %rdx = length (> kLShort)
//      %rdi = ptr (may not be aligned)
//      %xmm0 = pattern

LNotShort:
	movl    %edi,%ecx		// copy low bits of dest ptr
	negl    %ecx
	andl    $15,%ecx                // mask down to #bytes to 16-byte align
	jz	LAligned		// skip if already aligned
	movdqu	%xmm0,(%rdi)		// store 16 unaligned bytes
	movdqu	%xmm0,16(%rdi)		// and 16 more, to be sure we have an aligned chunk
	addq	%rcx,%rdi		// now point to the aligned chunk
	subq	%rcx,%rdx		// adjust remaining count
	movdqa	(%rdi),%xmm0		// get the rotated pattern (probably stalling)
	addq	$16,%rdi		// skip past the aligned chunk
	subq	$16,%rdx

// Set up for 64-byte loops.
//      %rdx = length remaining
//      %rdi = ptr (aligned)
//      %xmm0 = rotated pattern

LAligned:
	movq	%rdx,%rcx		// copy length remaining
	andl    $63,%edx                // mask down to residual length (0..63)
	andq    $-64,%rcx               // %ecx <- #bytes we will zero in by-64 loop
	jz	LNoMoreChunks		// no 64-byte chunks
	addq    %rcx,%rdi               // increment ptr by length to move
	cmpq	$(kVeryLong),%rcx	// long enough to justify non-temporal stores?
	jge	LVeryLong		// yes
	negq    %rcx			// 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,(%rdi,%rcx)
	movdqa  %xmm0,16(%rdi,%rcx)
	movdqa  %xmm0,32(%rdi,%rcx)
	movdqa  %xmm0,48(%rdi,%rcx)
	addq    $64,%rcx
	jne     1b

	jmp	LNoMoreChunks

// Very long operands: use non-temporal stores to bypass cache.

LVeryLong:
	negq    %rcx			// negate length to move
	jmp	1f

	.align	4,0x90			// keep inner loops 16-byte aligned
1:
	movntdq %xmm0,(%rdi,%rcx)
	movntdq %xmm0,16(%rdi,%rcx)
	movntdq %xmm0,32(%rdi,%rcx)
	movntdq %xmm0,48(%rdi,%rcx)
	addq    $64,%rcx
	jne     1b

	sfence                          // required by non-temporal stores
	jmp	LNoMoreChunks

// Handle leftovers: loop by 16.
//      %edx = length remaining (<64)
//      %edi = ptr (aligned)
//      %xmm0 = rotated pattern

LLoopBy16:
	movdqa	%xmm0,(%rdi)		// pack in 16 more bytes
	subl	$16,%edx		// decrement count
	addq	$16,%rdi		// increment ptr
LNoMoreChunks:
	cmpl	$16,%edx		// more to go?
	jge	LLoopBy16		// yes
	jmp	LLessThan16		// handle up to 15 remaining bytes