/* * 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 #undef ASSEMBLER #define __APPLE_API_PRIVATE #include #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 // *************** // * 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); clrrgi r9,r3,LOG2_GPR_BYTES// align pointer by zeroing right LOG2_GPR_BYTES bits 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