/* Optimized strcmp implementation for Power7 using 'cmpb' instruction Copyright (C) 2014-2015 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 Lesser General Public License as published by the Free Software Foundation; either version 2.1 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 Lesser General Public License for more details. You should have received a copy of the GNU Lesser General Public License along with the GNU C Library; if not, see . */ /* The optimization is achieved here through cmpb instruction. 8byte aligned strings are processed with double word comparision and unaligned strings are handled effectively with loop unrolling technique */ #include /* int [r3] strcmp (const char *s1 [r3], const char *s2 [r4]) */ EALIGN (strcmp, 4, 0) CALL_MCOUNT 2 or r9, r3, r4 rldicl. r10, r9, 0, 61 /* are s1 and s2 8 byte aligned..? */ bne cr0, L(process_unaligned_bytes) /* process input parameters on double word aligned boundary */ ld r9, 0(r4) /* load s2 at offset=0 */ li r10, 0 /* load mask=0 */ cmpb r10, r9, r10 /* compare bytes at s2 with mask */ cmpdi cr7, r10, 0 /* is NULL found ..? is end of string HIT */ bne cr7, L(process_unaligned_bytes) /* process byte by byte */ ld r10, 0(r3) /* load s1 at offset=0 */ li r8, 0 /* load mask=0 */ cmpb r8, r10, r8 /* compare bytes at s1 with mask */ cmpdi cr7, r8, 0 /* is NULL found ..? is end of string HIT */ bne cr7, L(process_unaligned_bytes) /* process byte by byte */ /*s1 and s2 does not contain NULL now , so compare all 8 bytes in a GO */ cmpb r9, r10, r9 /* compare s1 and s2 */ cmpdi cr7, r9, -1 /* compare result with 0xFFFFFFFFFFFFFFFF */ bne cr7, L(process_unaligned_bytes) /* s1,s2 mismatch found */ addi r5, r3, 8 /* save next offset of s2 */ addi r11, r4, 8 /* save next offset of s1 */ ld r8, 8(r4) /* load s2 at offset=8 */ li r9, 0 /* load mask=0 */ cmpb r9, r8, r9 /* compare bytes at s2 with mask */ cmpdi cr7, r9, 0 /* NULL found ..? */ bne cr7, L(processBytes)/* update input and process bytes one by one */ mr r9, r4 /* save s2 */ li r10, 0 /* load mask=0 */ ld r7, 8(r3) /* load s1 at offset=8 */ cmpb r6, r7, r10 /* compare bytes at s1 with mask */ cmpdi cr7, r6, 0 /* is NULL found */ bne cr7, L(processBytes)/* mismatch, so process one by one */ L(unrollDword): cmpb r8, r7, r8 /* compare s1 and s2 */ cmpdi cr7, r8, -1 /* compare result with 0xFFFFFFFFFFFFFFFF */ bne cr7, L(processBytes)/* mismatch with s1 and s2 */ addi r5, r3, 16 /* save offset=16 of s1 */ addi r4, r9, 16 /* save offset=16 of s2 */ ld r8, 16(r9) /* load s2 at offset=16 */ cmpb r7, r8, r10 /* compare bytes at s2 with mask */ cmpdi cr7, r7, 0 /* NULL found ..? */ bne cr7, L(update2processBytes) ld r7, 16(r3) /* load s1 at offset=16 */ cmpb r6, r7, r10 /* check s1 for end of string */ cmpdi cr7, r6, 0 /* end of s1 ?,then handle byte by byte */ bne 7,L(update2processBytes) cmpb r8, r7, r8 /* compare s1 and s2 double words */ cmpdi cr7, r8, -1 /* compare results with 0xFFFFFFFFFFFFFFFF */ bne cr7,L(update2processBytes) addi r5, r3, 24 /* update s1 to offset=24 */ addi r4, r9, 24 /* update s2 to offset=24 */ ld r8, 24(r9) /* load s2 */ cmpb r7, r8, r10 /* compare s2 for NULL */ cmpdi cr7, r7, 0 /* verify if s2 is ending now */ bne cr7,L(update2processBytes) ld r7, 24(r3) /* load s1 at offset=24 */ cmpb r6, r7, r10 /* verify for NULL */ cmpdi cr7, r6, 0 /* is NULL found */ bne cr7, L(update2processBytes) cmpb r8, r7, r8 /* compare s1 and s2 */ cmpdi cr7, r8, -1 /* are s1 and s2 same ..? */ bne cr7, L(update2processBytes) addi r7, r9, 32 /* update s2 to next double word */ addi r3, r3, 32 /* update s1 to next double word */ ld r8, 32(r9) /* load s2 */ mr r4, r7 /* save s2 */ cmpb r6, r8, r10 /* compare s2 with NULL */ cmpdi cr7, r6, 0 /* end of s2 ..? */ bne cr7, L(process_unaligned_bytes) ld r6, 0(r3) /* load and compare s1 for NULL */ cmpb r5, r6, r10 cmpdi cr7, r5, 0 bne cr7, L(process_unaligned_bytes) cmpb r8, r6, r8 /* compare s1 and s2 */ cmpdi cr7, r8, -1 bne cr7, L(process_unaligned_bytes) addi r5, r3, 8 /* increment s1 and d2 here */ addi r11, r9, 40 ld r8, 40(r9) /* process s2 now */ cmpb r9, r8, r10 cmpdi cr7, r9, 0 bne cr7, L(processBytes) mr r9, r7 ld r7, 8(r3) /* process s1 now */ cmpb r6, r7, r10 cmpdi cr7, r6, 0 beq cr7, L(unrollDword) /* unroll to compare s1 and s2 */ L(processBytes): mr r4, r11 /* update input params */ mr r3, r5 .p2align 4 L(process_unaligned_bytes): lbz r9, 0(r3) /* load byte from s1 */ lbz r10, 0(r4) /* load byte from s2 */ cmpdi cr7, r9, 0 /* compare *s1 with NULL */ beq cr7, L(diffOfNULL) /* if *s1 is NULL , return *s1 - *s2 */ cmplw cr7, r9, r10 /* compare *s1 and *s2 */ bne cr7, L(ComputeDiff) /* branch to compute difference and return */ lbz r9, 1(r3) /* load next byte from s1 */ lbz r10, 1(r4) /* load next byte from s2 */ cmpdi cr7, r9, 0 /* compare *s1 with NULL */ beq cr7, L(diffOfNULL) /* if *s1 is NULL , return *s1 - *s2 */ cmplw cr7, r9, r10 /* compare *s1 and *s2 */ bne cr7, L(ComputeDiff) /* branch to compute difference and return */ lbz r9, 2(r3) /* unroll 3rd byte here */ lbz r10, 2(r4) cmpdi cr7, r9, 0 beq cr7, L(diffOfNULL) cmplw cr7, r9, r10 bne 7, L(ComputeDiff) lbz r9, 3(r3) /* unroll 4th byte now */ lbz r10, 3(r4) addi r3, r3, 4 /* increment s1 by unroll factor */ cmpdi cr7, r9, 0 cmplw cr6, 9, r10 beq cr7, L(diffOfNULL) addi r4, r4, 4 /* increment s2 by unroll factor */ beq cr6, L(process_unaligned_bytes) /* unroll byte processing */ .p2align 4 L(ComputeDiff): extsw r9, r9 subf r10, r10, r9 /* compute s1 - s2 */ extsw r3, r10 blr /* return */ .p2align 4 L(diffOfNULL): li r9, 0 subf r10, r10, r9 /* compute s1 - s2 */ extsw r3, r10 /* sign extend result */ blr /* return */ .p2align 4 L(update2processBytes): mr r3, r5 /* update and proceed */ b L(process_unaligned_bytes) END (strcmp) libc_hidden_builtin_def (strcmp)