/* * Copyright (c) 2002 Apple Computer, Inc. All rights reserved. * * @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 * 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 // we need the defs for cr7_eq etc #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 // *************** *********** // * M E M C M P * and * B C M P * // *************** *********** // // int memcmp(const char *s1, const char *s2, size_t len); // int bcmp(const char *s1, const char *s2, size_t len); // // Bcmp returns (+,0,-), whereas memcmp returns the true difference // between the first differing bytes, but we treat them identically. // // We optimize the compare by doing it word parallel. This introduces // a complication: if we blindly did word loads from both sides until // finding a difference, we might get a spurious page fault by // reading bytes past the difference. To avoid this, we never do a "lwz" // that crosses a page boundary. // // In 64-bit mode, this routine is doubleword parallel. .text .globl EXT(memcmp) .globl EXT(bcmp) .align 5 LEXT(memcmp) // int memcmp(const char *s1,const char *s2,size_t len); LEXT(bcmp) // int bcmp(const char *s1,const char *s2,size_t len); cmplgi cr1,r5,2*GPR_BYTES // is buffer too short to bother with parallel compares? andi. r0,r3,GPR_BYTES-1 // is LHS aligned? blt cr1,Lshort // short buffer, so just compare byte-by-byte beq Laligned // skip if aligned subfic r0,r0,GPR_BYTES // r0 <- #bytes to align LHS mtctr r0 // set up for byte loop b Lbyteloop // Handle short buffer or end-of-buffer. // r3 = LHS ptr (unaligned) // r4 = RHS ptr (unaligned) // r5 = length remaining in buffer (0..2*GPR_BYTES-1) Lshort: cmpgi r5,0 // null buffer? mtctr r5 // assume not null, and set up for loop bne Lshortloop // buffer not null li r3,0 // say "equal" blr .align 5 Lshortloop: lbz r7,0(r3) // next LHS byte addi r3,r3,1 lbz r8,0(r4) // next RHS byte addi r4,r4,1 cmpw r7,r8 // compare the bytes bdnzt eq,Lshortloop // loop if more to go and bytes are equal sub r3,r7,r8 // generate return value blr // We're at a RHS page boundary. Compare GPR_BYTES bytes in order to cross the // page but still keep the LHS ptr aligned. Lcrosspage: cmplgi r5,2*GPR_BYTES // enough bytes left to use parallel compares? li r0,GPR_BYTES // get #bytes to cross RHS page blt Lshort // buffer is about to end mtctr r0 b Lbyteloop // Compare byte-by-byte. // r3 = LHS ptr (unaligned) // r4 = RHS ptr (unaligned) // r5 = length remaining in buffer (must be >0) // ctr = bytes to compare .align 5 Lbyteloop: lbz r7,0(r3) // next LHS byte addi r3,r3,1 lbz r8,0(r4) // next RHS byte addi r4,r4,1 subi r5,r5,1 // decrement bytes remaining in buffer cmpw r7,r8 // compare the bytes bdnzt eq,Lbyteloop // loop if more to go and bytes are equal bne Ldifferent // done if we found differing bytes // LHS is now aligned. Loop over words/doublewords until end of RHS page or buffer. // When we get to the end of the page, we compare 4/8 bytes, so that we keep // the LHS aligned. // r3 = LHS ptr (aligned) // r4 = RHS ptr (unaligned) // r5 = length remaining in buffer (>= GPR_BYTES bytes) Laligned: rlwinm r9,r4,0,0xFFF // get RHS offset in page subfic r0,r9,4096 // get #bytes left in RHS page subfc r7,r0,r5 // *** subfe r8,r5,r5 // * r9 <- min(r0,r5), and r7,r7,r8 // * using algorithm in Compiler Writer's Guide add r9,r0,r7 // *** srgi. r8,r9,LOG2_GPR_BYTES// get #words/doublewords we can compare clrrgi r9,r9,LOG2_GPR_BYTES// get #bytes we will compare word-parallel beq-- Lcrosspage // we're at a RHS page boundary mtctr r8 // set up loop count sub r5,r5,r9 // decrement length remaining b Lwordloop // Compare a word or doubleword at a time, until one of two conditions: // - a difference is found // - end of count (ie, end of buffer or RHS page, whichever is first) // At this point, registers are as follows: // r3 = LHS ptr (aligned) // r4 = RHS ptr (unaligned) // r5 = length remaining in buffer (may be 0) // ctr = count of word/doublewords until end of buffer or RHS page .align 5 // align inner loop Lwordloop: lg r7,0(r3) // r7 <- next aligned LHS word or doubleword addi r3,r3,GPR_BYTES lg r8,0(r4) // r8 <- next unaligned RHS word or doubleword addi r4,r4,GPR_BYTES xor. r11,r7,r8 // compare them bdnzt eq,Lwordloop // loop if ctr!=0 and cr0_eq beq Lcrosspage // skip if buffer or page end reached wo difference // Found differing bytes. cntlzg r0,r11 // find 1st difference (r0 = 0..31 or 63) rlwinm r9,r0,0,0x38 // byte align bit offset (r9 = 0,8,16, or 24 etc) addi r0,r9,8 // now, r0 = 8, 16, 24, or 32 etc #if defined(__ppc__) rlwnm r7,r7,r0,24,31 // right justify differing bytes and mask off rest rlwnm r8,r8,r0,24,31 #else rldcl r7,r7,r0,56 // right justify differing bytes and mask off rest rldcl r8,r8,r0,56 #endif Ldifferent: // bytes in r7 and r8 differ sub r3,r7,r8 // compute return value blr