memset.s

glibc 2.9,最新版的C语言库函数

/* Optimized memset implementation for PowerPC64.
   Copyright (C) 1997,99, 2000,02,03, 2006 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., 51 Franklin Street, Fifth Floor, Boston MA
   02110-1301 USA.  */

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

/* __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 (1024 bits). There is a special case for setting cache lines
   to 0, to take advantage of the dcbz instruction.  */

	.machine power4
EALIGN (BP_SYM (memset), 5, 0)
	CALL_MCOUNT

#define rTMP	r0
#define rRTN	r3	/* Initial value of 1st argument.  */
#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.  */
#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 (known to be 128).  */
#define rCLM	r9	/* Cache line size mask to check for cache alignment.  */
L(_memset):
/* Take care of case for size <= 4.  */
	cmplwi	cr1, rLEN, 4
	andi.	rALIGN, rMEMP0, 3
	mr	rMEMP, rMEMP0
	ble-	cr1, L(small)

/* Align to word boundary.  */
	cmplwi	cr5, rLEN, 31
	rlwimi	rCHR, rCHR, 8, 16, 23 /* Replicate byte to halfword.  */
	beq+	L(aligned)
	mtcrf	0x01, rMEMP0
	subfic	rALIGN, rALIGN, 4
	add	rMEMP, rMEMP, rALIGN
	sub	rLEN, rLEN, rALIGN
	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(aligned):
	mtcrf	0x01, rLEN
	rlwimi	rCHR, rCHR, 16, 0, 15 /* Replicate halfword to word.  */
	ble	cr5, L(medium)
/* Align to 32-byte boundary.  */
	andi.	rALIGN, rMEMP, 0x1C
	subfic	rALIGN, rALIGN, 0x20
	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)
        stw     rCHR, -4(rMEMP2)
	stwu	rCHR, -8(rMEMP2)
L(a1):	blt	cr1, L(a2)
        stw     rCHR, -4(rMEMP2)
	stw	rCHR, -8(rMEMP2)
	stw	rCHR, -12(rMEMP2)
	stwu	rCHR, -16(rMEMP2)
L(a2):  bf      29, L(caligned)
        stw     rCHR, -4(rMEMP2)

/* Now aligned to a 32 byte boundary.  */
L(caligned):
	cmplwi	cr1, rCHR, 0
	clrrwi.	rALIGN, rLEN, 5
	mtcrf	0x01, rLEN
	beq	cr1, L(zloopstart) /* Special case for clearing memory using dcbz.  */
L(nondcbz):
	srwi	rTMP, rALIGN, 5
	mtctr	rTMP
	beq	L(medium)	/* We may not actually get to do a full line.  */
	clrlwi.	rLEN, rLEN, 27
	add	rMEMP, rMEMP, rALIGN
	li	rNEG64, -0x40
	bdz	L(cloopdone)

        .align 4
L(c3): 	dcbtst	rNEG64, rMEMP
        stw     rCHR, -4(rMEMP)
	stw	rCHR, -8(rMEMP)
        stw     rCHR, -12(rMEMP)
	stw	rCHR, -16(rMEMP)
        stw     rCHR, -20(rMEMP)
	stw	rCHR, -24(rMEMP)
        stw     rCHR, -28(rMEMP)
	stwu	rCHR, -32(rMEMP)
	bdnz	L(c3)
L(cloopdone):
        stw     rCHR, -4(rMEMP)
	stw	rCHR, -8(rMEMP)
        stw     rCHR, -12(rMEMP)
	stw	rCHR, -16(rMEMP)
	cmplwi	cr1, rLEN, 16
        stw     rCHR, -20(rMEMP)
	stw	rCHR, -24(rMEMP)
        stw     rCHR, -28(rMEMP)
	stwu	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)
	li      rCLS,128  /* cache line size is 128 */
	dcbt	0,rMEMP
L(getCacheAligned):
	cmplwi	cr1,rLEN,32
	andi.	rTMP,rMEMP,127
	blt	cr1,L(handletail32)
	beq	L(cacheAligned)
	addi	rMEMP,rMEMP,32
	addi	rLEN,rLEN,-32
	stw	rCHR,-32(rMEMP)
        stw     rCHR,-28(rMEMP)
	stw	rCHR,-24(rMEMP)
	stw     rCHR,-20(rMEMP)
	stw	rCHR,-16(rMEMP)
        stw     rCHR,-12(rMEMP)
	stw	rCHR,-8(rMEMP)
        stw     rCHR,-4(rMEMP)
	b	L(getCacheAligned)

/* Now we are aligned to the cache line and can use dcbz.  */
        .align 4
L(cacheAligned):
	cmplw	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 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 4 bytes or less.  */
	cmplwi	cr5, rLEN, 1
	cmplwi	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):
	cmplwi	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
        stw     rCHR, -4(rMEMP)
	stw	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):
        stw     rCHR, -4(rMEMP)
	stw	rCHR, -8(rMEMP)
        stw     rCHR, -12(rMEMP)
	stwu	rCHR, -16(rMEMP)
L(medium_27f):
	bflr-	28
L(medium_28t):
        stw     rCHR, -4(rMEMP)
	stw	rCHR, -8(rMEMP)
	blr
END (BP_SYM (memset))
libc_hidden_builtin_def (memset)