/* $NetBSD: strcpy.S,v 1.5 2001/12/04 17:56:33 wiz Exp $ */ /* * Written by Randy Hyde, 1993 * Public domain. */ #include #if defined(LIBC_SCCS) RCSID("$NetBSD: strcpy.S,v 1.5 2001/12/04 17:56:33 wiz Exp $") #endif /* * char * * strcpy (char *d, const char *s) * copy string s to d. */ KENTRY(strcpy, 8) enter [r3,r4,r5],0 movd B_ARG1,r1 movd B_ARG0,r2 /* * We need to double word align the src (R1). When we read * by double words we can read potentially up to 3 bytes * past the null terminating byte. We can avoid spurious page * faults by double word aligning the source. It also runs * faster. IWD */ movqd 3,r3 andd r1,r3 0: casew 1f(pc)[r3:w] 1: .word 5f-0b .word 2f-0b .word 3f-0b .word 4f-0b .align 2,0xa2 2: movb 0(r1),0(r2) ; cmpqb 0,0(r1) ; beq 9f movb 1(r1),1(r2) ; cmpqb 0,1(r1) ; beq 9f movb 2(r1),2(r2) ; cmpqb 0,2(r1) ; beq 9f addqd 3,r1 addqd 3,r2 br 5f .align 2,0xa2 3: movb 0(r1),0(r2) ; cmpqb 0,0(r1) ; beq 9f movb 1(r1),1(r2) ; cmpqb 0,1(r1) ; beq 9f addqd 2,r1 addqd 2,r2 br 5f .align 2,0xa2 4: movb 0(r1),0(r2) ; cmpqb 0,0(r1) ; beq 9f addqd 1,r1 addqd 1,r2 /* * Okay, when we get down here R1 points at a double word * aligned source block of bytes, R2 points at the destination * block of bytes (typically, though not always double word * aligned). * This guy processes four bytes at a time and checks for the * zero terminating byte amongst the bytes in the double word. * This algorithm is due to Dave Rand. * * Sneaky test for zero amongst four bytes: * * xxyyzztt * -01010101 * --------- * aabbccdd * bic xxyyzztt * --------- * eeffgghh ee=0x80 if xx=0, ff=0x80 if yy=0, etc. * * This whole result will be zero if there * was no zero byte, it will be non-zero if * there is a zero byte present. */ 5: movd 0x01010101,r3 /* Magic number to use */ movd 0x80808080,r4 /* Another magic number. */ movd 0(r1),r5 /* Get 1st double word. */ movd r5,r0 /* Save for storage later. */ subd r3,r0 /* Gets borrow if byte = 0. */ bicd r5,r0 /* Clear original bits. */ andd r4,r0 /* See if borrow occurred. */ cmpqd 0,r0 bne 1f /* See if this DWORD contained a 0. */ .align 2,0xa2 0: movd 4(r1),r0 /* Get next 4 bytes to process */ movd r5,0(r2) /* Save away prev four bytes. */ addd 4,r1 /* addd is faster than addqd here */ addd 4,r2 movd r0,r5 /* Save for storage if no zeros. */ subd r3,r0 bicd r5,r0 andd r4,r0 cmpqd 0,r0 beq 0b /* * At this point, R1 points at a double word which * contains a zero byte. Copy the characters up to * (and including) the zero byte and quit. */ 1: movb 0(r1),0(r2) ; cmpqb 0,0(r1) ; beq 9f movb 1(r1),1(r2) ; cmpqb 0,1(r1) ; beq 9f movb 2(r1),2(r2) ; cmpqb 0,2(r1) ; beq 9f movb 3(r1),3(r2) /* This one must be a zero byte */ 9: movd B_ARG0,r0 exit [r3,r4,r5] ret ARGS