Add src/sve/strnlen.S

Change-Id: If73e6079e07228a9f31fe30ed97e1511f03c26a9

2 files changed, 96 insertions, 1 deletions

diff --git a/Makefile.am b/Makefile.am
index 75b3527..ede49db 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -294,7 +294,7 @@ libcortex_strings_la_SOURCES = \
 	src/sve/strcpy.S \
 	src/sve/strlen.S \
 	src/sve/strncmp.S \
-	src/aarch64/strnlen.S
+	src/sve/strnlen.S
 else
 libcortex_strings_la_SOURCES = \
 	src/aarch64/memchr.S \
diff --git a/src/sve/strnlen.S b/src/sve/strnlen.S
new file mode 100644
index 0000000..459facc
--- /dev/null
+++ b/src/sve/strnlen.S
@@ -0,0 +1,95 @@
+/*
+ * strnlen - calculate the length of a string with limit.
+ *
+ * Copyright (c) 2018, Linaro Limited
+ * All rights Reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *     * Redistributions of source code must retain the above copyright
+ *       notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above copyright
+ *       notice, this list of conditions and the following disclaimer in the
+ *       documentation and/or other materials provided with the distribution.
+ *     * Neither the name of the company nor the names of its contributors
+ *       may be used to endorse or promote products derived from this
+ *       software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+/* Assumptions:
+ *
+ * ARMv8-a, AArch64
+ * SVE Available.
+ */
+
+	.arch	armv8-a+sve
+	.text
+
+	.globl	strnlen
+	.type	strnlen, %function
+	.p2align 4
+strnlen:
+	setffr				/* initialize FFR */
+	mov	x2, 0			/* initialize len */
+	b	1f
+
+	.p2align 4
+	/* We have off + vl <= max, and so may read the whole vector.  */
+0:	ldff1b	z0.b, p0/z, [x0, x2]
+	rdffrs	p1.b, p0/z
+	b.nlast	2f
+
+	/* First fault did not fail: the whole vector is valid.
+	   Avoid depending on the contents of FFR beyond the branch.  */
+	cmpeq	p2.b, p0/z, z0.b, 0
+	b.any	8f
+	incb	x2
+
+1:	whilelo	p0.b, x2, x1
+	b.last	0b
+
+	/* We have off + vl < max.  Test for off == max before proceeding.  */
+	b.none	9f
+
+	ldff1b	z0.b, p0/z, [x0, x2]
+	rdffrs	p1.b, p0/z
+	b.nlast	2f
+
+	/* First fault did not fail: the vector up to max is valid.
+	   Avoid depending on the contents of FFR beyond the branch.
+	   Compare for end-of-string, but there are no more bytes.  */
+	cmpeq	p2.b, p0/z, z0.b, 0
+
+	/* Found end-of-string or zero.  */
+8:	brkb	p2.b, p0/z, p2.b
+	mov	x0, x2
+	incp	x0, p2.b
+	ret
+
+	/* First fault failed: only some of the vector is valid.
+	   Perform the comparison only on the valid bytes.  */
+2:	cmpeq	p2.b, p1/z, z0.b, 0
+	b.any	8b
+
+	/* No inequality or zero found.  Re-init FFR, incr and loop.  */
+	setffr
+	incp	x2, p1.b
+	b	1b
+
+	/* End of count.  Return max.  */
+9:	mov	x0, x2
+	ret
+
+	.size	strnlen, . - strnlen