📄 strncmp.s
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/* * .seg "data" * .asciz "@(#)strncmp.s 1.1 92/07/30" * Copyright (c) 1989 by Sun Microsystems, Inc. */#include <sun4/asm_linkage.h> .seg "text" .align 4/* * strncmp(s1, s2, n) * Compare strings (at most n bytes): s1>s2: >0 s1==s2: 0 s1<s2: <0 */ ENTRY(strncmp) save %sp, -SA(WINDOWSIZE), %sp cmp %i2, 8 bl,a cmp_bytes ! for small counts go do bytes sub %i0, %i1, %i0 ! delay slot, get diff from s1 - s2 andcc %i0, 3, %g0 ! is s1 aligned1: bz iss2 ! if so go check s2 andcc %i1, 3, %i3 ! is s2 aligned deccc %i2 ! --n >= 0 ? bneg doneq nop ! delay slot ldsb [%i0], %i4 ! else cmp one byte ldsb [%i1], %i5 inc %i0 cmp %i4, %i5 bne noteqb inc %i1 tst %i4 ! terminating zero bnz 1b andcc %i0, 3, %g0 b,a doneqiss2: set 0x7efefeff, %l6 set 0x81010100, %l7 sethi %hi(0xff000000), %l0 ! masks to test for terminating null sethi %hi(0x00ff0000), %l1 srl %l1, 8, %l2 ! generate 0x0000ff00 mask bz w4cmp ! if s2 word aligned, compare words cmp %i3, 2 ! check if s2 half aligned be w2cmp cmp %i3, 1 ! check if aligned to 1 or 3 bytes w3cmp: ldub [%i1], %i5 inc 1, %i1 be w1cmp sll %i5, 24, %i5 sub %i0, %i1, %i02: deccc 4, %i2 ! n >= 4 ? bge 3f ld [%i1], %i3 ! delay slot dec %i1 ! reset s2 inc %i0 ! reset s1 diff b cmp_bytes ! do a byte at a time if n < 4 inc 4, %i23: ld [%i0 + %i1], %i4 inc 4, %i1 srl %i3, 8, %l4 ! merge with the other half or %l4, %i5, %i5 cmp %i4, %i5 be 1f add %i4, %l6, %l3 b,a noteq1: xor %l3, %i4, %l3 and %l3, %l7, %l3 cmp %l3, %l7 be,a 2b sll %i3, 24, %i5 andcc %i4, %l0, %g0 ! check if first byte was zero b,a noteq1: bnz 1f andcc %i4, %l1, %g0 ! check if second byte was zero b,a doneq1: bnz 1f andcc %i4, %l2, %g0 ! check if third byte was zero b,a doneq1: bnz 1f andcc %i4, 0xff, %g0 ! check if last byte is zero b,a doneq1: bnz 2b sll %i3, 24, %i5 b,a doneqw1cmp: clr %l4 lduh [%i1], %l4 inc 2, %i1 sll %l4, 8, %l4 or %i5, %l4, %i5 sub %i0, %i1, %i03: deccc 4, %i2 ! n >= 4 ? bge 4f ld [%i1], %i3 ! delay slot dec 3, %i1 ! reset s2 inc 3, %i0 ! reset s1 diff b cmp_bytes ! do a byte at a time if n < 4 inc 4, %i24: ld [%i0 + %i1], %i4 inc 4, %i1 srl %i3, 24, %l4 ! merge with the other half or %l4, %i5, %i5 cmp %i4, %i5 be 1f add %i4, %l6, %l3 b,a noteq1: xor %l3, %i4, %l3 and %l3, %l7, %l3 cmp %l3, %l7 be,a 3b sll %i3, 8, %i5 andcc %i4, %l0, %g0 ! check if first byte was zero b,a noteq1: bnz 1f andcc %i4, %l1, %g0 ! check if second byte was zero b,a doneq1: bnz 1f andcc %i4, %l2, %g0 ! check if third byte was zero b,a doneq1: bnz 1f andcc %i4, 0xff, %g0 ! check if last byte is zero b,a doneq1: bnz 3b sll %i3, 8, %i5 b,a doneq w2cmp: lduh [%i1], %i5 ! read a halfword to align s2 inc 2, %i1 sll %i5, 16, %i5 sub %i0, %i1, %i04: deccc 4, %i2 ! n >= 4 ? bge 5f ld [%i1], %i3 ! delay slot dec 2, %i1 ! reset s2 inc 2, %i0 ! reset s1 diff b cmp_bytes ! do a byte at a time if n < 4 inc 4, %i2 ! delay slot5: ld [%i1 + %i0], %i4 ! read a word from s2 inc 4, %i1 srl %i3, 16, %l4 ! merge with the other half or %l4, %i5, %i5 cmp %i4, %i5 be 1f add %i4, %l6, %l3 b,a noteq1: xor %l3, %i4, %l3 ! are any bytes 0? and %l3, %l7, %l3 cmp %l3, %l7 be,a 4b sll %i3, 16, %i5 andcc %i4, %l0, %g0 ! check if first byte was zero b,a noteq1: bnz 1f andcc %i4, %l1, %g0 ! check if second byte was zero b,a doneq1: bnz 1f andcc %i4, %l2, %g0 ! check if third byte was zero b,a doneq1: bnz 1f andcc %i4, 0xff, %g0 ! check if last byte is zero b,a doneq1: bnz 4b sll %i3, 16, %i5 b,a doneqw4cmp: sub %i0, %i1, %i0 ld [%i1], %i5 ! read a word from s15: deccc 4, %i2 ! n >= 4 ? bneg,a cmp_bytes ! do a byte at a time if n < 4 inc 4, %i2 ld [%i1 + %i0], %i4 ! read a word from s2 cmp %i4, %i5 inc 4, %i1 be 1f add %i4, %l6, %l3 b,a noteq1: xor %l3, %i4, %l3 and %l3, %l7, %l3 cmp %l3, %l7 be,a 5b ld [%i1], %i5 andcc %i4, %l0, %g0 ! check if first byte was zero b,a noteq ! if word is equal and any bytes are zero, strings are equal1: bnz 1f andcc %i4, %l1, %g0 ! check if second byte was zero b,a doneq1: bnz 1f andcc %i4, %l2, %g0 ! check if third byte was zero b,a doneq1: bnz 1f andcc %i4, 0xff, %g0 ! check if last byte is zero b,a doneq1: bnz,a 5b ld [%i1], %i5doneq: ret restore %g0, %g0, %o0 ! equal return zeronoteq: sra %i4, 24, %l4 sra %i5, 24, %l5 subcc %l4, %l5, %i0 bne 6f andcc %l4, 0xff, %g0 bz doneq sll %i4, 8, %l4 sll %i5, 8, %l5 sra %l4, 24, %l4 sra %l5, 24, %l5 subcc %l4, %l5, %i0 bne 6f andcc %l4, 0xff, %g0 bz doneq sll %i4, 16, %l4 sll %i5, 16, %l5 sra %l4, 24, %l4 sra %l5, 24, %l5 subcc %l4, %l5, %i0 bne 6f andcc %l4, 0xff, %g0 bz doneq nopnoteqb: sll %i4, 24, %l4 sll %i5, 24, %l5 sra %l4, 24, %l4 sra %l5, 24, %l5 subcc %l4, %l5, %i06: ret restore %i0, %g0, %o0 ! Do a byte by byte comparison, disregarding alignmentscmp_bytes: deccc %i2 ! --n >= 0 ?1: bneg doneq nop ! delay slot ldsb [%i1 + %i0], %i4 ! read a word from s1 ldsb [%i1], %i5 ! read a word from s2 inc %i1 cmp %i4, %i5 bne noteqb tst %i4 ! terminating zero bnz 1b deccc %i2 ! --n >= 0 b,a doneq ⌨️ 快捷键说明
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