arm64/lib/strcmp.S

1 /* SPDX-License-Identifier: GPL-2.0-only */
9  * http://bazaar.launchpad.net/~linaro-toolchain-dev/cortex-strings/trunk/
20  *	x0 - const string 1 pointer
21  *    x1 - const string 2 pointer
23  * x0 - an integer less than, equal to, or greater than zero
60 	* NUL detection works on the principle that (X - 1) & (~X) & 0x80
61 	* (=> (X - 1) & ~(X | 0x7f)) is non-zero iff a byte is zero, and
70 	eor	diff, data1, data2	/* Non-zero if differences found.  */
71 	bic	has_nul, tmp1, tmp2	/* Non-zero if NUL terminator.  */
84 	lsl	tmp1, tmp1, #3		/* Bytes beyond alignment -> bits.  */
86 	neg	tmp1, tmp1		/* Bits to alignment -64.  */
89 	/* Big-endian.  Early bytes are at MSB.  */
91 	/* Little-endian.  Early bytes are at LSB.  */
132 	/*load 8 bytes from aligned str1 and non-aligned str2..*/
139 	eor	diff, data1, data2 /* Non-zero if differences found.  */
161 	eor	diff, data1, data2  /* Non-zero if differences found.  */
171 	eor	diff, data1, data2  /* Non-zero if differences found.  */
177 	* reversed the byte-order as big-endian,then CLZ can find the most
178 	* significant zero bits.
185 	* For big-endian we cannot use the trick with the syndrome value
186 	* as carry-propagation can corrupt the upper bits if the trailing
198 	/*Re-compute the NUL-byte detection, using a byte-reversed value. */
208 	* The MS-non-zero bit of the syndrome marks either the first bit
209 	* that is different, or the top bit of the first zero byte.
216 	* But we need to zero-extend (char is unsigned) the value and then
217 	* perform a signed 32-bit subtraction.