memset.s

来自「Glibc 2.3.2源代码(解压后有100多M)」· S 代码 · 共 297 行

/* Optimized memset implementation for PowerPC64.
   Copyright (C) 1997, 1999, 2000, 2002 Free Software Foundation, Inc.
   This file is part of the GNU C Library.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 of the License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with the GNU C Library; if not, write to the Free
   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
   02111-1307 USA.  */

#include <sysdep.h>
#include <bp-sym.h>
#include <bp-asm.h>

/* Define a global static that can hold the cache line size.  The 
   assumption is that startup code will access the "aux vector" to
   to obtain the value set by the kernel and store it into this 
   variable.  */
	.globl __cache_line_size
	.section	".data"
	.align 2
	.type	__cache_line_size,@object
	.size	__cache_line_size,4
__cache_line_size:
	.long	0
	.section	".toc","aw"
.LC0:
	.tc __cache_line_size[TC],__cache_line_size
	.section	".text"
	.align 2

/* __ptr_t [r3] memset (__ptr_t s [r3], int c [r4], size_t n [r5]));
   Returns 's'.

   The memset is done in three sizes: byte (8 bits), word (32 bits),
   cache line (256 bits). There is a special case for setting cache lines
   to 0, to take advantage of the dcbz instruction.  */

EALIGN (BP_SYM (memset), 5, 0)

#define rTMP	r0
#define rRTN	r3	/* Initial value of 1st argument.  */
#if __BOUNDED_POINTERS__
# define rMEMP0	r4	/* Original value of 1st arg.  */
# define rCHR	r5	/* Char to set in each byte.  */
# define rLEN	r6	/* Length of region to set.  */
# define rMEMP	r10	/* Address at which we are storing.  */
#else
# define rMEMP0	r3	/* Original value of 1st arg.  */
# define rCHR	r4	/* Char to set in each byte.  */
# define rLEN	r5	/* Length of region to set.  */
# define rMEMP	r6	/* Address at which we are storing.  */
#endif
#define rALIGN	r7	/* Number of bytes we are setting now (when aligning). */
#define rMEMP2	r8

#define rNEG64	r8	/* Constant -64 for clearing with dcbz.  */
#define rCLS	r8	/* Cache line size obtained from static.  */
#define rCLM	r9	/* Cache line size mask to check for cache alignment.  */

___memset:
#if __BOUNDED_POINTERS__
	cmpldi	cr1, rRTN, 0
	CHECK_BOUNDS_BOTH_WIDE (rMEMP0, rTMP, rTMP2, rLEN)
	beq	cr1, L(b0)
	STORE_RETURN_VALUE (rMEMP0)
	STORE_RETURN_BOUNDS (rTMP, rTMP2)
L(b0):
#endif
/* Take care of case for size <= 4.  */
	cmpldi	cr1, rLEN, 8
	andi.	rALIGN, rMEMP0, 7
	mr	rMEMP, rMEMP0
	ble-	cr1, L(small)
	
/* Align to doubleword boundary.  */
	cmpldi	cr5, rLEN, 31
	rlwimi	rCHR, rCHR, 8, 16, 23 /* Replicate byte to halfword.  */
	beq+	L(aligned2)
	mtcrf	0x01, rMEMP0
	subfic	rALIGN, rALIGN, 8
	cror	28,30,31		/* Detect odd word aligned.  */
	add	rMEMP, rMEMP, rALIGN
	sub	rLEN, rLEN, rALIGN
	rlwimi	rCHR, rCHR, 16, 0, 15 /* Replicate halfword to word.  */
	bt	29, L(g4)
/* Process the even word of doubleword.  */
	bf+	31, L(g2)
	stb	rCHR, 0(rMEMP0)
	bt	30, L(g4x)
L(g2):
	sth	rCHR, -6(rMEMP)
L(g4x):
	stw	rCHR, -4(rMEMP)
	b	L(aligned)
/* Process the odd word of doubleword.  */
L(g4):
	bf	28, L(g4x) /* If false, word aligned on odd word.  */
	bf+	31, L(g0)
	stb	rCHR, 0(rMEMP0)
	bt	30, L(aligned)
L(g0):	
	sth	rCHR, -2(rMEMP)	
	
/* Handle the case of size < 31.  */
L(aligned2):
	rlwimi	rCHR, rCHR, 16, 0, 15 /* Replicate halfword to word.  */
L(aligned):
	mtcrf	0x01, rLEN
	ble	cr5, L(medium)
/* Align to 32-byte boundary.  */
	andi.	rALIGN, rMEMP, 0x18
	subfic	rALIGN, rALIGN, 0x20
	insrdi	rCHR,rCHR,32,0 /* Replicate word to double word. */
	beq	L(caligned)
	mtcrf	0x01, rALIGN
	add	rMEMP, rMEMP, rALIGN
	sub	rLEN, rLEN, rALIGN
	cmplwi	cr1, rALIGN, 0x10
	mr	rMEMP2, rMEMP
	bf	28, L(a1)
	stdu	rCHR, -8(rMEMP2)
L(a1):	blt	cr1, L(a2)
	std	rCHR, -8(rMEMP2)
	stdu	rCHR, -16(rMEMP2)
L(a2):

/* Now aligned to a 32 byte boundary.  */
L(caligned):
	cmpldi	cr1, rCHR, 0
	clrrdi.	rALIGN, rLEN, 5
	mtcrf	0x01, rLEN	
	beq	cr1, L(zloopstart) /* Special case for clearing memory using dcbz.  */
L(nondcbz):	
	srdi	rTMP, rALIGN, 5
	mtctr	rTMP
	beq	L(medium)	/* We may not actually get to do a full line.  */
	clrldi.	rLEN, rLEN, 59
	add	rMEMP, rMEMP, rALIGN
	li	rNEG64, -0x40
	bdz	L(cloopdone)

L(c3):	dcbtst	rNEG64, rMEMP
	std	rCHR, -8(rMEMP)
	std	rCHR, -16(rMEMP)
	std	rCHR, -24(rMEMP)
	stdu	rCHR, -32(rMEMP)
	bdnz	L(c3)
L(cloopdone):
	std	rCHR, -8(rMEMP)
	std	rCHR, -16(rMEMP)
	cmpldi	cr1, rLEN, 16
	std	rCHR, -24(rMEMP)
	stdu	rCHR, -32(rMEMP)
	beqlr
	add	rMEMP, rMEMP, rALIGN
	b	L(medium_tail2)

	.align 5
/* Clear lines of memory in 128-byte chunks.  */
L(zloopstart):
/* If the remaining length is less the 32 bytes, don't bother getting 
	 the cache line size.  */
	beq	L(medium)
	ld	rCLS,.LC0@toc(r2)
	lwz	rCLS,0(rCLS)	
/* If the cache line size was not set just goto to L(nondcbz) which is 
	 safe for any cache line size.  */	
	cmpldi	cr1,rCLS,0
	beq		cr1,L(nondcbz)
	
	
/* Now we know the cache line size, and it is not 32-bytes, but
	 we may not yet be aligned to the cache line. May have a partial 
	 line to fill, so touch it 1st.  */	
	dcbt	0,rMEMP	
	addi	rCLM,rCLS,-1
L(getCacheAligned):
	cmpldi	cr1,rLEN,32
	and.	rTMP,rCLM,rMEMP
	blt		cr1,L(handletail32)
	beq		L(cacheAligned)
	addi	rMEMP,rMEMP,32
	addi	rLEN,rLEN,-32
	std		rCHR,-32(rMEMP)
	std		rCHR,-24(rMEMP)
	std		rCHR,-16(rMEMP)
	std		rCHR,-8(rMEMP)
	b		L(getCacheAligned)
	
/* Now we are aligned to the cache line and can use dcbz.  */	
L(cacheAligned):
	cmpld	cr1,rLEN,rCLS
	blt		cr1,L(handletail32)
	dcbz	0,rMEMP
	subf	rLEN,rCLS,rLEN
	add		rMEMP,rMEMP,rCLS
	b		L(cacheAligned)

/* We are here because the cache line size was set and was not 32-bytes
   and the remainder (rLEN) is less than the actual cache line size.
   So set up the preconditions for L(nondcbz) and go there.  */			
L(handletail32):
	clrrwi.	rALIGN, rLEN, 5
	b		L(nondcbz)

	.align 5
L(small):
/* Memset of 8 bytes or less.  */
	cmpldi	cr6, rLEN, 4
	cmpldi	cr5, rLEN, 1
	ble	cr6,L(le4)
	subi	rLEN, rLEN, 4
	stb	rCHR,0(rMEMP)
	stb	rCHR,1(rMEMP)
	stb	rCHR,2(rMEMP)
	stb	rCHR,3(rMEMP)
	addi	rMEMP,rMEMP, 4
	cmpldi	cr5, rLEN, 1
L(le4):
	cmpldi	cr1, rLEN, 3
	bltlr	cr5
	stb	rCHR, 0(rMEMP)
	beqlr	cr5
	stb	rCHR, 1(rMEMP)
	bltlr	cr1
	stb	rCHR, 2(rMEMP)
	beqlr	cr1
	stb	rCHR, 3(rMEMP)
	blr

/* Memset of 0-31 bytes.  */
	.align 5
L(medium):
	insrdi	rCHR,rCHR,32,0 /* Replicate word to double word.  */
	cmpldi	cr1, rLEN, 16
L(medium_tail2):
	add	rMEMP, rMEMP, rLEN
L(medium_tail):
	bt-	31, L(medium_31t)
	bt-	30, L(medium_30t)
L(medium_30f):
	bt-	29, L(medium_29t)
L(medium_29f):
	bge-	cr1, L(medium_27t)
	bflr-	28
	std	rCHR, -8(rMEMP)
	blr

L(medium_31t):
	stbu	rCHR, -1(rMEMP)
	bf-	30, L(medium_30f)
L(medium_30t):
	sthu	rCHR, -2(rMEMP)
	bf-	29, L(medium_29f)
L(medium_29t):
	stwu	rCHR, -4(rMEMP)
	blt-	cr1, L(medium_27f) 
L(medium_27t):
	std	rCHR, -8(rMEMP)
	stdu	rCHR, -16(rMEMP)
L(medium_27f):
	bflr-	28
L(medium_28t):
	std	rCHR, -8(rMEMP)
	blr
END_GEN_TB (BP_SYM (memset),TB_TOCLESS)

/* Copied from bzero.S to prevent the linker from inserting a stub 
   between bzero and memset.  */
ENTRY (BP_SYM (__bzero))
#if __BOUNDED_POINTERS__
	mr	r6,r4
	li	r5,0
	mr	r4,r3
	/* Tell memset that we don't want a return value.  */
	li	r3,0
	b	___memset
#else
	mr	r5,r4
	li	r4,0
	b	___memset
#endif
END_GEN_TB (BP_SYM (__bzero),TB_TOCLESS)

weak_alias (BP_SYM (__bzero), BP_SYM (bzero))