glibc/sysdeps/powerpc/memset.s

 # Optimized memset implementation for PowerPC.
 # Copyright (C) 1997 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 Library General Public License as
 # published by the Free Software Foundation; either version 2 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
 # Library General Public License for more details.
 #
 # You should have received a copy of the GNU Library General Public
 # License along with the GNU C Library; see the file COPYING.LIB.  If not,
 # write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 # Boston, MA 02111-1307, USA.

	.section ".text"
	.align 5
	nop
	
	.globl memset
	.type memset,@function
memset:	
 # __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.
 # r6:	current address we are storing at
 # r7:	number of bytes we are setting now (when aligning)

 # take care of case for size <= 4
	cmplwi %cr1,%r5,4	
	andi.  %r7,%r3,3
	mr     %r6,%r3
	ble-   %cr1,small
 # align to word boundary
	cmplwi %cr5,%r5,31
	rlwimi %r4,%r4,8,16,23
	beq+   aligned			# 8th instruction from .align
	mtcrf  0x01,%r3
	subfic %r7,%r7,4
	add    %r6,%r6,%r7
	sub    %r5,%r5,%r7
	bf+    31,0f
	stb    %r4,0(%r3)
	bt     30,aligned
0:	sth    %r4,-2(%r6)		#  16th instruction from .align
 # take care of case for size < 31
aligned:
	mtcrf  0x01,%r5
	rlwimi %r4,%r4,16,0,15
	ble    %cr5,medium
 # align to cache line boundary...
	andi.  %r7,%r6,0x1C
	subfic %r7,%r7,0x20
	beq    caligned
	mtcrf  0x01,%r7
	add    %r6,%r6,%r7
	sub    %r5,%r5,%r7
	cmplwi %cr1,%r7,0x10
	mr     %r8,%r6
	bf     28,1f
	stw    %r4,-4(%r8)
	stwu   %r4,-8(%r8)
1:	blt    %cr1,2f
	stw    %r4,-4(%r8)	# 32nd instruction from .align
	stw    %r4,-8(%r8)
	stw    %r4,-12(%r8)
	stwu   %r4,-16(%r8)
2:	bf     29,caligned
	stw    %r4,-4(%r8)
 # now aligned to a cache line.
caligned:
	cmplwi %cr1,%r4,0
	clrrwi. %r7,%r5,5
	mtcrf  0x01,%r5		# 40th instruction from .align
	beq    %cr1,zloopstart	# special case for clearing memory using dcbz
	srwi   %r0,%r7,5
	mtctr  %r0
	beq    medium		# we may not actually get to do a full line
	clrlwi. %r5,%r5,27
	add    %r6,%r6,%r7
0:	li     %r8,-0x40
	bdz    cloopdone	# 48th instruction from .align
	
cloop:	dcbz   %r8,%r6
	stw    %r4,-4(%r6)
	stw    %r4,-8(%r6)
	stw    %r4,-12(%r6)
	stw    %r4,-16(%r6)
	nop			# let 601 fetch last 4 instructions of loop
	stw    %r4,-20(%r6)
	stw    %r4,-24(%r6)	# 56th instruction from .align
	nop			# let 601 fetch first 8 instructions of loop
	stw    %r4,-28(%r6)
	stwu   %r4,-32(%r6)
	bdnz   cloop
cloopdone:
	stw    %r4,-4(%r6)
	stw    %r4,-8(%r6)
	stw    %r4,-12(%r6)
	stw    %r4,-16(%r6)	# 64th instruction from .align
	stw    %r4,-20(%r6)
	cmplwi %cr1,%r5,16
	stw    %r4,-24(%r6)
	stw    %r4,-28(%r6)
	stwu   %r4,-32(%r6)
	beqlr
	add    %r6,%r6,%r7
	b      medium_tail2	# 72nd instruction from .align

	.align 5
	nop
# clear lines of memory in 128-byte chunks.
zloopstart:
	clrlwi %r5,%r5,27
	mtcrf  0x02,%r7
	srwi.  %r0,%r7,7
	mtctr  %r0
	li     %r7,0x20
	li     %r8,-0x40
	cmplwi %cr1,%r5,16	# 8
	bf     26,0f	
	dcbz   0,%r6
	addi   %r6,%r6,0x20
0:	li     %r9,-0x20
	bf     25,1f
	dcbz   0,%r6
	dcbz   %r7,%r6
	addi   %r6,%r6,0x40	# 16
1:	cmplwi %cr5,%r5,0
	beq    medium
zloop:	
	dcbz   0,%r6
	dcbz   %r7,%r6
	addi   %r6,%r6,0x80
	dcbz   %r8,%r6
	dcbz   %r9,%r6
	bdnz   zloop
	beqlr  %cr5
	b      medium_tail2
	
	.align 5	
small:
 # Memset of 4 bytes or less.
	cmplwi %cr5,%r5,1
	cmplwi %cr1,%r5,3
	bltlr  %cr5
	stb    %r4,0(%r6)
	beqlr  %cr5
	nop
	stb    %r4,1(%r6)
	bltlr  %cr1
	stb    %r4,2(%r6)
	beqlr  %cr1
	nop
	stb    %r4,3(%r6)
	blr

# memset of 0-31 bytes
	.align 5
medium:
	cmplwi %cr1,%r5,16
medium_tail2:
	add    %r6,%r6,%r5
medium_tail:
	bt-    31,medium_31t
	bt-    30,medium_30t
medium_30f:
	bt-    29,medium_29t
medium_29f:
	bge-   %cr1,medium_27t
	bflr-  28
	stw    %r4,-4(%r6)	# 8th instruction from .align
	stw    %r4,-8(%r6)
	blr

medium_31t:	
	stbu   %r4,-1(%r6)
	bf-    30,medium_30f
medium_30t:
	sthu   %r4,-2(%r6)
	bf-    29,medium_29f
medium_29t:
	stwu   %r4,-4(%r6)
	blt-   %cr1,medium_27f	# 16th instruction from .align
medium_27t:
	stw    %r4,-4(%r6)
	stw    %r4,-8(%r6)
	stw    %r4,-12(%r6)
	stwu   %r4,-16(%r6)
medium_27f:
	bflr-  28
medium_28t:
	stw    %r4,-4(%r6)
	stw    %r4,-8(%r6)
	blr