diff options
| -rw-r--r-- | newlib/libc/machine/aarch64/strcmp.S | 51 |
1 files changed, 40 insertions, 11 deletions
diff --git a/newlib/libc/machine/aarch64/strcmp.S b/newlib/libc/machine/aarch64/strcmp.S index 85baca920..e2bef2d49 100644 --- a/newlib/libc/machine/aarch64/strcmp.S +++ b/newlib/libc/machine/aarch64/strcmp.S @@ -1,4 +1,4 @@ -/* Copyright (c) 2012-2013, Linaro Limited +/* Copyright (c) 2012-2018, Linaro Limited All rights reserved. Redistribution and use in source and binary forms, with or without @@ -41,6 +41,8 @@ \f: .endm +#define L(label) .L ## label + #define REP8_01 0x0101010101010101 #define REP8_7f 0x7f7f7f7f7f7f7f7f #define REP8_80 0x8080808080808080 @@ -69,24 +71,25 @@ def_fn strcmp p2align=6 eor tmp1, src1, src2 mov zeroones, #REP8_01 tst tmp1, #7 - b.ne .Lmisaligned8 + b.ne L(misaligned8) ands tmp1, src1, #7 - b.ne .Lmutual_align + b.ne L(mutual_align) /* NUL detection works on the principle that (X - 1) & (~X) & 0x80 (=> (X - 1) & ~(X | 0x7f)) is non-zero iff a byte is zero, and can be done in parallel across the entire word. */ -.Lloop_aligned: +L(loop_aligned): ldr data1, [src1], #8 ldr data2, [src2], #8 -.Lstart_realigned: +L(start_realigned): sub tmp1, data1, zeroones orr tmp2, data1, #REP8_7f eor diff, data1, data2 /* Non-zero if differences found. */ bic has_nul, tmp1, tmp2 /* Non-zero if NUL terminator. */ orr syndrome, diff, has_nul - cbz syndrome, .Lloop_aligned + cbz syndrome, L(loop_aligned) /* End of performance-critical section -- one 64B cache line. */ +L(end): #ifndef __AARCH64EB__ rev syndrome, syndrome rev data1, data1 @@ -137,7 +140,7 @@ def_fn strcmp p2align=6 ret #endif -.Lmutual_align: +L(mutual_align): /* Sources are mutually aligned, but are not currently at an alignment boundary. Round down the addresses and then mask off the bytes that preceed the start point. */ @@ -157,15 +160,41 @@ def_fn strcmp p2align=6 #endif orr data1, data1, tmp2 orr data2, data2, tmp2 - b .Lstart_realigned + b L(start_realigned) -.Lmisaligned8: - /* We can do better than this. */ +L(misaligned8): + /* Align SRC1 to 8 bytes and then compare 8 bytes at a time, always + checking to make sure that we don't access beyond page boundary in + SRC2. */ + tst src1, #7 + b.eq L(loop_misaligned) +L(do_misaligned): ldrb data1w, [src1], #1 ldrb data2w, [src2], #1 cmp data1w, #1 ccmp data1w, data2w, #0, cs /* NZCV = 0b0000. */ - b.eq .Lmisaligned8 + b.ne L(done) + tst src1, #7 + b.ne L(do_misaligned) + +L(loop_misaligned): + /* Test if we are within the last dword of the end of a 4K page. If + yes then jump back to the misaligned loop to copy a byte at a time. */ + and tmp1, src2, #0xff8 + eor tmp1, tmp1, #0xff8 + cbz tmp1, L(do_misaligned) + 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. */ + bic has_nul, tmp1, tmp2 /* Non-zero if NUL terminator. */ + orr syndrome, diff, has_nul + cbz syndrome, L(loop_misaligned) + b L(end) + +L(done): sub result, data1, data2 ret .size strcmp, .-strcmp |