diff options
Diffstat (limited to 'sysdeps/powerpc/powerpc64/power8/strcmp.S')
| -rw-r--r-- | sysdeps/powerpc/powerpc64/power8/strcmp.S | 257 |
1 files changed, 257 insertions, 0 deletions
diff --git a/sysdeps/powerpc/powerpc64/power8/strcmp.S b/sysdeps/powerpc/powerpc64/power8/strcmp.S new file mode 100644 index 0000000000..223d891c2e --- /dev/null +++ b/sysdeps/powerpc/powerpc64/power8/strcmp.S @@ -0,0 +1,257 @@ +/* Optimized strcmp implementation for PowerPC64/POWER8. + Copyright (C) 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 + <http://www.gnu.org/licenses/>. */ + +#include <sysdep.h> + +/* Implements the function + + size_t [r3] strcmp (const char *s1 [r3], const char *s2 [r4]) + + The implementation uses unaligned doubleword access to avoid specialized + code paths depending of data alignment. Although recent powerpc64 uses + 64K as default, the page cross handling assumes minimum page size of + 4k. */ + +EALIGN (strcmp, 4, 0) + li r0,0 + + /* Check if [s1]+32 or [s2]+32 will cross a 4K page boundary using + the code: + + (((size_t) s1) % PAGE_SIZE > (PAGE_SIZE - ITER_SIZE)) + + with PAGE_SIZE being 4096 and ITER_SIZE begin 32. */ + + rldicl r7,r3,0,52 + rldicl r9,r4,0,52 + cmpldi cr7,r7,4096-32 + bgt cr7,L(pagecross_check) + cmpldi cr5,r9,4096-32 + bgt cr5,L(pagecross_check) + + /* For short string up to 32 bytes, load both s1 and s2 using + unaligned dwords and compare. */ + ld r8,0(r3) + ld r10,0(r4) + cmpb r12,r8,r0 + cmpb r11,r8,r10 + orc. r9,r12,r11 + bne cr0,L(different_nocmpb) + + ld r8,8(r3) + ld r10,8(r4) + cmpb r12,r8,r0 + cmpb r11,r8,r10 + orc. r9,r12,r11 + bne cr0,L(different_nocmpb) + + ld r8,16(r3) + ld r10,16(r4) + cmpb r12,r8,r0 + cmpb r11,r8,r10 + orc. r9,r12,r11 + bne cr0,L(different_nocmpb) + + ld r8,24(r3) + ld r10,24(r4) + cmpb r12,r8,r0 + cmpb r11,r8,r10 + orc. r9,r12,r11 + bne cr0,L(different_nocmpb) + + addi r7,r3,32 + addi r4,r4,32 + +L(align_8b): + /* Now it has checked for first 32 bytes, align source1 to doubleword + and adjust source2 address. */ + rldicl r9,r7,0,61 /* source1 alignment to doubleword */ + subf r4,r9,r4 /* Adjust source2 address based on source1 + alignment. */ + rldicr r7,r7,0,60 /* Align source1 to doubleword. */ + + /* At this point, source1 alignment is 0 and source2 alignment is + between 0 and 7. Check is source2 alignment is 0, meaning both + sources have the same alignment. */ + andi. r9,r4,0x7 + bne cr0,L(loop_diff_align) + + /* If both source1 and source2 are doubleword aligned, there is no + need for page boundary cross checks. */ + + ld r8,0(r7) + ld r10,0(r4) + cmpb r12,r8,r0 + cmpb r11,r8,r10 + orc. r9,r12,r11 + bne cr0,L(different_nocmpb) + + .align 4 +L(loop_equal_align): + ld r8,8(r7) + ld r10,8(r4) + cmpb r12,r8,r0 + cmpb r11,r8,r10 + orc. r9,r12,r11 + bne cr0,L(different_nocmpb) + + ld r8,16(r7) + ld r10,16(r4) + cmpb r12,r8,r0 + cmpb r11,r8,r10 + orc. r9,r12,r11 + bne cr0,L(different_nocmpb) + + ldu r8,24(r7) + ldu r10,24(r4) + cmpb r12,r8,r0 + cmpb r11,r8,r10 + orc. r9,r12,r11 + bne cr0,L(different_nocmpb) + + b L(loop_equal_align) + + /* A zero byte was found in r8 (s1 dword), r9 contains the cmpb + result and r10 the dword from s2. To code isolate the byte + up to end (including the '\0'), masking with 0xFF the remaining + ones: + + #if __LITTLE_ENDIAN__ + (__builtin_ffsl (x) - 1) = counting trailing zero bits + r9 = (__builtin_ffsl (r9) - 1) + 8; + r9 = -1UL << r9 + #else + r9 = __builtin_clzl (r9) + 8; + r9 = -1UL >> r9 + #endif + r8 = r8 | r9 + r10 = r10 | r9 */ + +#ifdef __LITTLE_ENDIAN__ + nor r9,r9,r9 +L(different_nocmpb): + neg r3,r9 + and r9,r9,r3 + cntlzd r9,r9 + subfic r9,r9,63 +#else + not r9,r9 +L(different_nocmpb): + cntlzd r9,r9 + subfic r9,r9,56 +#endif + srd r3,r8,r9 + srd r10,r10,r9 + rldicl r10,r10,0,56 + rldicl r3,r3,0,56 + subf r3,r10,r3 + extsw r3,r3 + blr + + .align 4 +L(pagecross_check): + subfic r9,r9,4096 + subfic r7,r7,4096 + cmpld cr7,r7,r9 + bge cr7,L(pagecross) + mr r7,r9 + + /* If unaligned 16 bytes reads across a 4K page boundary, it uses + a simple byte a byte comparison until the page alignment for s1 + is reached. */ +L(pagecross): + add r7,r3,r7 + subf r9,r3,r7 + mtctr r9 + + .align 4 +L(pagecross_loop): + /* Loads a byte from s1 and s2, compare if *s1 is equal to *s2 + and if *s1 is '\0'. */ + lbz r9,0(r3) + lbz r10,0(r4) + addi r3,r3,1 + addi r4,r4,1 + cmplw cr7,r9,r10 + cmpdi cr5,r9,r0 + bne cr7,L(pagecross_ne) + beq cr5,L(pagecross_nullfound) + bdnz L(pagecross_loop) + b L(align_8b) + + .align 4 + /* The unaligned read of source2 will cross a 4K page boundary, + and the different byte or NULL maybe be in the remaining page + bytes. Since it can not use the unaligned load, the algorithm + reads and compares 8 bytes to keep source1 doubleword aligned. */ +L(check_source2_byte): + li r9,8 + mtctr r9 + + .align 4 +L(check_source2_byte_loop): + lbz r9,0(r7) + lbz r10,0(r4) + addi r7,r7,1 + addi r4,r4,1 + cmplw cr7,r9,10 + cmpdi r5,r9,0 + bne cr7,L(pagecross_ne) + beq cr5,L(pagecross_nullfound) + bdnz L(check_source2_byte_loop) + + /* If source2 is unaligned to doubleword, the code needs to check + on each interation if the unaligned doubleword access will cross + a 4k page boundary. */ + .align 5 +L(loop_unaligned): + ld r8,0(r7) + ld r10,0(r4) + cmpb r12,r8,r0 + cmpb r11,r8,r10 + orc. r9,r12,r11 + bne cr0,L(different_nocmpb) + addi r7,r7,8 + addi r4,r4,8 + +L(loop_diff_align): + /* Check if [src2]+8 cross a 4k page boundary: + + srcin2 % PAGE_SIZE > (PAGE_SIZE - 8) + + with PAGE_SIZE being 4096. */ + rldicl r9,r4,0,52 + cmpldi cr7,r9,4088 + ble cr7,L(loop_unaligned) + b L(check_source2_byte) + + .align 4 +L(pagecross_ne): + extsw r3,r9 + mr r9,r10 +L(pagecross_retdiff): + subf r9,r9,r3 + extsw r3,r9 + blr + + .align 4 +L(pagecross_nullfound): + li r3,0 + b L(pagecross_retdiff) +END (strcmp) +libc_hidden_builtin_def (strcmp) |