X-Git-Url: https://git.saurik.com/apple/libc.git/blobdiff_plain/9385eb3d10ebe5eb398c52040ec3dbfba9b0cdcf..fbd86d4cc20b02a10edcca92fb7ae0a143e63cc4:/ppc/string/strncat.s diff --git a/ppc/string/strncat.s b/ppc/string/strncat.s index 91b114e..04690b2 100644 --- a/ppc/string/strncat.s +++ b/ppc/string/strncat.s @@ -3,8 +3,6 @@ * * @APPLE_LICENSE_HEADER_START@ * - * Copyright (c) 1999-2003 Apple Computer, Inc. All Rights Reserved. - * * 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 @@ -26,6 +24,17 @@ #include #undef ASSEMBLER +/* 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 + +#define __APPLE_API_PRIVATE +#include +#undef __APPLE_API_PRIVATE + + // ***************** // * S T R N C A T * // ***************** @@ -50,71 +59,70 @@ // Note that "count" refers to the max number of bytes to _append_. // There is no limit to the number of bytes we will scan looking for // the end of the "dst" string. +// +// In 64-bit mode, this algorithm is doubleword parallel. .text .globl EXT(strncat) .align 5 -LEXT(strncat) - andi. r0,r3,3 // is dst aligned? - dcbtst 0,r3 // touch in dst - lis r6,hi16(0xFEFEFEFF) // start to load magic constants +LEXT(strncat) // char* strncat(char *dst, const char *src, size_t count); + 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) - dcbt 0,r4 // touch in source + srw r10,r10,r11 // create a mask of 0xFF bytes for operand in r8 ori r6,r6,lo16(0xFEFEFEFF) ori r7,r7,lo16(0x80808080) - mr r9,r3 // use r9 for dest ptr (must return r3 intact) - beq Lword0loop // dest is aligned - subfic r0,r0,4 // r0 <- #bytes to word align dest - mtctr r0 // set up byte loop - -// Loop over bytes looking for 0-byte marking end of dest, until dest is -// word aligned. -// r4 = source ptr (unaligned) -// r5 = count (unchanged so far) -// r6 = 0xFEFEFEFF -// r7 = 0x80808080 -// r9 = dest ptr (unaligned) -// ctr = byte count - -Lbyte0loop: - lbz r8,0(r9) // r8 <- next dest byte - addi r9,r9,1 - cmpwi r8,0 // test for 0 - bdnzf eq,Lbyte0loop // loop until (ctr==0) | (r8==0) - - bne Lword0loop // haven't found 0, so enter word-aligned loop - andi. r0,r4,3 // is source aligned? - subi r9,r9,1 // point to the 0-byte we just stored - beq Laligned // source is already aligned - subfic r0,r0,4 // r0 <- #bytes to word align source - b Lbyteloop // must align source +#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 looking for 0-byte marking end of dest. +// Loop over words or doublewords looking for 0-byte marking end of dest. // r4 = source ptr (unaligned) // r5 = count (unchanged so far) // r6 = 0xFEFEFEFF // r7 = 0x80808080 -// r9 = dest ptr (word aligned) +// r9 = dest ptr (aligned) .align 5 // align inner loops for speed Lword0loop: - lwz r8,0(r9) // r8 <- next dest word - addi r9,r9,4 + lgu r8,GPR_BYTES(r9) // r8 <- next dest word or doubleword +Lword0loopEnter: 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) +// r5 = count (unchanged so far) +// 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 - slwi r10,r8,7 // move 0x01 bits (false hits) into 0x80 position - andi. r0,r4,3 // is source aligned? + 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 - subi r9,r9,4 // back up r9 to the start of the word - cntlzw r10,r11 // find 0 byte (r0 = 0, 8, 16, or 24) + 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 r10 = 0, 1, 2, or 3 add r9,r9,r10 // now r9 points to the 0-byte in dest beq Laligned // skip if source already aligned - subfic r0,r0,4 // r0 <- #bytes to word align source // Copy min(r0,r5) bytes, until 0-byte. // r0 = #bytes we propose to copy (NOTE: must be >0) @@ -125,7 +133,7 @@ Lword0loop: // r9 = dest ptr (unaligned) Lbyteloop: - cmpwi r5,0 // buffer empty? (note: unsigned) + cmpgi r5,0 // buffer empty? (note: count is unsigned) beq-- L0notfound // buffer full but 0 not found lbz r8,0(r4) // r8 <- next source byte subic. r0,r0,1 // decrement count of bytes to move @@ -137,40 +145,40 @@ Lbyteloop: beqlr cr1 // byte was 0, so done bne Lbyteloop // r0!=0, source not yet aligned -// Source is word aligned. Loop over words until 0-byte found or end -// of buffer. -// r4 = source ptr (word aligned) +// Source is aligned. Loop over words or doublewords until 0-byte found +// or end of buffer. +// r4 = source ptr (aligned) // r5 = length remaining in buffer // r6 = 0xFEFEFEFF // r7 = 0x80808080 // r9 = dest ptr (unaligned) Laligned: - srwi. r8,r5,2 // get #words in buffer + srgi. r8,r5,LOG2_GPR_BYTES// get #words or doublewords in buffer addi r0,r5,1 // if no words, copy rest of buffer beq-- Lbyteloop // fewer than 4 bytes in buffer mtctr r8 // set up word loop count - rlwinm r5,r5,0,0x3 // mask buffer length down to leftover bytes + rlwinm r5,r5,0,GPR_BYTES-1 // mask buffer length down to leftover bytes b LwordloopEnter -// Inner loop: move a word at a time, until one of two conditions: +// Inner loop: move a word or doubleword at a time, until one of two conditions: // - a zero byte is found // - end of buffer // At this point, registers are as follows: -// r4 = source ptr (word aligned) -// r5 = bytes leftover in buffer (0..3) +// r4 = source ptr (aligned) +// r5 = bytes leftover in buffer (0..GPR_BYTES-1) // r6 = 0xFEFEFEFF // r7 = 0x80808080 // r9 = dest ptr (unaligned) -// ctr = whole words left in buffer +// ctr = whole words or doublewords left in buffer .align 5 // align inner loop, which is 8 words long Lwordloop: - stw r8,0(r9) // pack word into destination - addi r9,r9,4 + stg r8,0(r9) // pack word or doubleword into destination + addi r9,r9,GPR_BYTES LwordloopEnter: - lwz r8,0(r4) // r8 <- next 4 source bytes - addi r4,r4,4 + lg r8,0(r4) // r8 <- next GPR_BYTES source bytes + addi r4,r4,GPR_BYTES 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 @@ -179,12 +187,12 @@ LwordloopEnter: beq-- LcheckLeftovers // skip if 0-byte not found // Found a 0-byte. Store last word up to and including the 0, a byte at a time. -// r8 = last word, known to have a 0-byte +// r8 = last word or doubleword, known to have a 0-byte // r9 = dest ptr Lstorelastbytes: - srwi. r0,r8,24 // right justify next byte and test for 0 - slwi r8,r8,8 // shift next byte into position + srgi. r0,r8,GPR_BYTES*8-8 // right justify next byte and test for 0 + slgi r8,r8,8 // shift next byte into position stb r0,0(r9) // pack into dest addi r9,r9,1 bne Lstorelastbytes // loop until 0 stored @@ -192,17 +200,17 @@ Lstorelastbytes: blr // 0-byte not found while appending words to source. There might be up to -// 3 "leftover" bytes to append, hopefully the 0-byte is in there. +// GPR_BYTES-1 "leftover" bytes to append, hopefully the 0-byte is in there. // r4 = source ptr (past word in r8) -// r5 = bytes leftover in buffer (0..3) +// r5 = bytes leftover in buffer (0..GPR_BYTES-1) // r6 = 0xFEFEFEFF // r7 = 0x80808080 -// r8 = last word of source, with no 0-byte +// r8 = last word or doubleword of source, with no 0-byte // r9 = dest ptr (unaligned) LcheckLeftovers: - stw r8,0(r9) // store last whole word of source - addi r9,r9,4 + stg r8,0(r9) // store last whole word or doubleword of source + addi r9,r9,GPR_BYTES addi r0,r5,1 // let r5 (not r0) terminate byte loop b Lbyteloop // append last few bytes