/*
* Copyright (c) 2002 Apple Computer, Inc. All rights reserved.
*
* @APPLE_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. 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,
* FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
* Please see the License for the specific language governing rights and
* limitations under the License.
*
* @APPLE_LICENSE_HEADER_END@
*/
#define ASSEMBLER
#include <mach/ppc/asm.h>
#undef ASSEMBLER
#define __APPLE_API_PRIVATE
#include <machine/cpu_capabilities.h>
#undef __APPLE_API_PRIVATE
/* We use mode-independent "g" opcodes such as "srgi". These expand
* into word operations when targeting __ppc__, and into doubleword
* operations when targeting __ppc64__.
*/
#include <architecture/ppc/mode_independent_asm.h>
// ***************
// * S T R C A T *
// ***************
//
// char* strcat(const char *dst, const char *src)// We optimize the move by doing it word parallel. This introduces
// a complication: if we blindly did word load/stores until finding
// a 0, we might get a spurious page fault by touching bytes past it.
// To avoid this, we never do a load that crosses a page boundary,
// and never store a byte we don't have to.
//
// The test for 0s relies on the following inobvious but very efficient
// word-parallel test:
// x = dataWord + 0xFEFEFEFF
// y = ~dataWord & 0x80808080
// if (x & y) == 0 then no zero found
// The test maps any non-zero byte to zero, and any zero byte to 0x80,
// with one exception: 0x01 bytes preceeding the first zero are also
// mapped to 0x80.
//
// In 64-bit mode, this algorithm is doubleword parallel.
.text
.globl EXT(strcat)
.align 5
LEXT(strcat) // char* strcat(const char *s, const char *append) li r10,-1 // get 0xFFs
lg r8,0(r9) // get word or doubleword with 1st operand byte
rlwinm r11,r3,3,(GPR_BYTES-1)*8 // get starting bit position of operand
#if defined(__ppc__)
lis r6,hi16(0xFEFEFEFF) // start to generate 32-bit magic constants
lis r7,hi16(0x80808080)
srw r10,r10,r11 // create a mask of 0xFF bytes for operand in r8
ori r6,r6,lo16(0xFEFEFEFF)
ori r7,r7,lo16(0x80808080)
#else
ld r6,_COMM_PAGE_MAGIC_FE(0) // get 0xFEFEFEFE FEFEFEFF from commpage
ld r7,_COMM_PAGE_MAGIC_80(0) // get 0x80808080 80808080 from commpage
srd r10,r10,r11 // create a mask of 0xFF bytes for operand in r8
#endif
orc r8,r8,r10 // make sure bytes preceeding operand are nonzero
b Lword0loopEnter
// Loop over words or doublewords looking for 0-byte marking end of dest.
// r4 = source ptr (unaligned)
// r6 = 0xFEFEFEFF
// r7 = 0x80808080
// r9 = dest ptr (aligned)
.align 5 // align inner loops for speed
Lword0loop:
lgu r8,GPR_BYTES(r9) // r8 <- next dest word or doubleword
Lword0loopEnter: // initial entry
add r10,r8,r6 // r10 <- word + 0xFEFEFEFF
andc r12,r7,r8 // r12 <- ~word & 0x80808080
and. r11,r10,r12 // r11 <- nonzero iff word has a 0-byte
beq Lword0loop // loop until 0 found
// Now we know one of the bytes in r8 is zero, we just have to figure out which one.
// We have mapped 0 bytes to 0x80, and nonzero bytes to 0x00, with one exception:
// 0x01 bytes preceeding the first zero are also mapped to 0x80. So we have to mask
// out the 0x80s caused by 0x01s before searching for the 0x80 byte. Once the 0 is
// found, we can start appending source. We align the source, which allows us to
// avoid worrying about spurious page faults.
// r4 = source ptr (unaligned)
// r6 = 0xFEFEFEFF
// r7 = 0x80808080
// r8 = word or doubleword with a 0-byte
// r9 = ptr to the word or doubleword in r8 (aligned)
// r11 = mapped word or doubleword
slgi r10,r8,7 // move 0x01 bits (false hits) into 0x80 position
andi. r0,r4,GPR_BYTES-1 // is source aligned?
andc r11,r11,r10 // mask out false hits
cntlzg r10,r11 // find 0 byte (r0 = 0, 8, 16, or 24)
subfic r0,r0,GPR_BYTES // get #bytes to align r4
srwi r10,r10,3 // now r0 = 0, 1, 2, or 3
add r9,r9,r10 // now r9 points to the 0-byte in dest
beq LwordloopEnter // skip if source is already aligned
mtctr r0 // set up loop
// Loop over bytes.
// r4 = source ptr (unaligned)
// r6 = 0xFEFEFEFF
// r7 = 0x80808080
// r9 = dest ptr (unaligned)
// ctr = byte count
Lbyteloop:
lbz r8,0(r4) // r8 <- next source byte
addi r4,r4,1
cmpwi r8,0 // 0 ?
stb r8,0(r9) // pack into dest
addi r9,r9,1
bdnzf eq,Lbyteloop // loop until (ctr==0) | (r8==0)
bne LwordloopEnter // 0-byte not found, so enter word loop
blr // 0-byte found, done
// Word loop: move a word or doubleword at a time until 0-byte found.
// r4 = source ptr (aligned)
// r6 = 0xFEFEFEFF
// r7 = 0x80808080
// r9 = dest ptr (unaligned)
.align 5 // align inner loop, which is 8 words ling
Lwordloop:
stg r8,0(r9) // pack word or doubleword into destination
addi r9,r9,GPR_BYTES
LwordloopEnter:
lg r8,0(r4) // r8 <- next 4 or 8 source bytes
addi r4,r4,GPR_BYTES
add r10,r8,r6 // r10 <- word + 0xFEFEFEFF
andc r12,r7,r8 // r12 <- ~word & 0x80808080
and. r0,r10,r12 // r0 <- nonzero iff word has a 0-byte
beq Lwordloop // loop if no 0-byte
// Found a 0-byte. Store last word up to and including the 0, a byte at a time.
// r8 = last word or doubleword, known to have a 0-byte
// r9 = dest ptr
Lstorelastbytes:
srgi. r0,r8,GPR_BYTES*8-8 // shift leftmost byte into bottom so we can "stb"
slgi r8,r8,8 // move on to next
stb r0,0(r9) // pack into dest
addi r9,r9,1
bne Lstorelastbytes // loop until 0 stored
blr