diff options
Diffstat (limited to 'sysdeps/aarch64/strncmp.S')
| -rw-r--r-- | sysdeps/aarch64/strncmp.S | 95 |
1 files changed, 80 insertions, 15 deletions
diff --git a/sysdeps/aarch64/strncmp.S b/sysdeps/aarch64/strncmp.S index 3e4d88a5d7..33c07befd8 100644 --- a/sysdeps/aarch64/strncmp.S +++ b/sysdeps/aarch64/strncmp.S @@ -49,6 +49,7 @@ #define limit_wd x13 #define mask x14 #define endloop x15 +#define count mask ENTRY_ALIGN_AND_PAD (strncmp, 6, 7) DELOUSE (0) @@ -58,9 +59,9 @@ ENTRY_ALIGN_AND_PAD (strncmp, 6, 7) eor tmp1, src1, src2 mov zeroones, #REP8_01 tst tmp1, #7 + and count, src1, #7 b.ne L(misaligned8) - ands tmp1, src1, #7 - b.ne L(mutual_align) + cbnz count, L(mutual_align) /* Calculate the number of full and partial words -1. */ sub limit_wd, limit, #1 /* limit != 0, so no underflow. */ lsr limit_wd, limit_wd, #3 /* Convert to Dwords. */ @@ -165,43 +166,107 @@ L(mutual_align): bic src1, src1, #7 bic src2, src2, #7 ldr data1, [src1], #8 - neg tmp3, tmp1, lsl #3 /* 64 - bits(bytes beyond align). */ + neg tmp3, count, lsl #3 /* 64 - bits(bytes beyond align). */ ldr data2, [src2], #8 mov tmp2, #~0 sub limit_wd, limit, #1 /* limit != 0, so no underflow. */ #ifdef __AARCH64EB__ /* Big-endian. Early bytes are at MSB. */ - lsl tmp2, tmp2, tmp3 /* Shift (tmp1 & 63). */ + lsl tmp2, tmp2, tmp3 /* Shift (count & 63). */ #else /* Little-endian. Early bytes are at LSB. */ - lsr tmp2, tmp2, tmp3 /* Shift (tmp1 & 63). */ + lsr tmp2, tmp2, tmp3 /* Shift (count & 63). */ #endif and tmp3, limit_wd, #7 lsr limit_wd, limit_wd, #3 /* Adjust the limit. Only low 3 bits used, so overflow irrelevant. */ - add limit, limit, tmp1 - add tmp3, tmp3, tmp1 + add limit, limit, count + add tmp3, tmp3, count orr data1, data1, tmp2 orr data2, data2, tmp2 add limit_wd, limit_wd, tmp3, lsr #3 b L(start_realigned) -L(ret0): - mov result, #0 - RET - .p2align 6 + /* Don't bother with dwords for up to 16 bytes. */ L(misaligned8): - sub limit, limit, #1 -1: + cmp limit, #16 + b.hs L(try_misaligned_words) + +L(byte_loop): /* Perhaps we can do better than this. */ ldrb data1w, [src1], #1 ldrb data2w, [src2], #1 subs limit, limit, #1 - ccmp data1w, #1, #0, cs /* NZCV = 0b0000. */ + ccmp data1w, #1, #0, hi /* NZCV = 0b0000. */ ccmp data1w, data2w, #0, cs /* NZCV = 0b0000. */ - b.eq 1b + b.eq L(byte_loop) +L(done): sub result, data1, data2 RET + + /* Align the SRC1 to a dword by doing a bytewise compare and then do + the dword loop. */ +L(try_misaligned_words): + mov limit_wd, limit, lsr #3 + cbz count, L(do_misaligned) + + neg count, count + and count, count, #7 + sub limit, limit, count + mov limit_wd, limit, lsr #3 + +L(page_end_loop): + ldrb data1w, [src1], #1 + ldrb data2w, [src2], #1 + cmp data1w, #1 + ccmp data1w, data2w, #0, cs /* NZCV = 0b0000. */ + b.ne L(done) + subs count, count, #1 + b.hi L(page_end_loop) + +L(do_misaligned): + /* Prepare ourselves for the next page crossing. Unlike the aligned + loop, we fetch 1 less dword because we risk crossing bounds on + SRC2. */ + mov count, #8 + subs limit_wd, limit_wd, #1 + b.lo L(done_loop) +L(loop_misaligned): + and tmp2, src2, #0xff8 + eor tmp2, tmp2, #0xff8 + cbz tmp2, L(page_end_loop) + + ldr data1, [src1], #8 + ldr data2, [src2], #8 + sub tmp1, data1, zeroones + orr tmp2, data1, #REP8_7f + eor diff, data1, data2 /* Non-zero if differences found. */ + bics has_nul, tmp1, tmp2 /* Non-zero if NUL terminator. */ + ccmp diff, #0, #0, eq + b.ne L(not_limit) + subs limit_wd, limit_wd, #1 + b.pl L(loop_misaligned) + +L(done_loop): + /* We found a difference or a NULL before the limit was reached. */ + and limit, limit, #7 + cbz limit, L(not_limit) + /* Read the last word. */ + sub src1, src1, 8 + sub src2, src2, 8 + ldr data1, [src1, limit] + ldr data2, [src2, limit] + sub tmp1, data1, zeroones + orr tmp2, data1, #REP8_7f + eor diff, data1, data2 /* Non-zero if differences found. */ + bics has_nul, tmp1, tmp2 /* Non-zero if NUL terminator. */ + ccmp diff, #0, #0, eq + b.ne L(not_limit) + +L(ret0): + mov result, #0 + RET + END (strncmp) libc_hidden_builtin_def (strncmp) |