Merge "AArch64: Add memcmp.S for Arm64."
diff --git a/runtime/arch/arm64/memcmp.S b/runtime/arch/arm64/memcmp.S
new file mode 100644
index 0000000..3d08ecd
--- /dev/null
+++ b/runtime/arch/arm64/memcmp.S
@@ -0,0 +1,155 @@
+/* Copyright (c) 2014, 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 Linaro 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
+ */
+
+#include <private/bionic_asm.h>
+
+/* Parameters and result. */
+#define src1 x0
+#define src2 x1
+#define limit x2
+#define result x0
+
+/* Internal variables. */
+#define data1 x3
+#define data1w w3
+#define data2 x4
+#define data2w w4
+#define has_nul x5
+#define diff x6
+#define endloop x7
+#define tmp1 x8
+#define tmp2 x9
+#define tmp3 x10
+#define pos x11
+#define limit_wd x12
+#define mask x13
+
+ENTRY(memcmp)
+ cbz limit, .Lret0
+ eor tmp1, src1, src2
+ tst tmp1, #7
+ b.ne .Lmisaligned8
+ ands tmp1, src1, #7
+ b.ne .Lmutual_align
+ add limit_wd, limit, #7
+ lsr limit_wd, limit_wd, #3
+ /* Start of performance-critical section -- one 64B cache line. */
+.Lloop_aligned:
+ ldr data1, [src1], #8
+ ldr data2, [src2], #8
+.Lstart_realigned:
+ subs limit_wd, limit_wd, #1
+ eor diff, data1, data2 /* Non-zero if differences found. */
+ csinv endloop, diff, xzr, ne /* Last Dword or differences. */
+ cbz endloop, .Lloop_aligned
+ /* End of performance-critical section -- one 64B cache line. */
+
+ /* Not reached the limit, must have found a diff. */
+ cbnz limit_wd, .Lnot_limit
+
+ /* Limit % 8 == 0 => all bytes significant. */
+ ands limit, limit, #7
+ b.eq .Lnot_limit
+
+ lsl limit, limit, #3 /* Bits -> bytes. */
+ mov mask, #~0
+#ifdef __AARCH64EB__
+ lsr mask, mask, limit
+#else
+ lsl mask, mask, limit
+#endif
+ bic data1, data1, mask
+ bic data2, data2, mask
+
+ orr diff, diff, mask
+.Lnot_limit:
+
+#ifndef __AARCH64EB__
+ rev diff, diff
+ rev data1, data1
+ rev data2, data2
+#endif
+ /* The MS-non-zero bit of DIFF marks either the first bit
+ that is different, or the end of the significant data.
+ Shifting left now will bring the critical information into the
+ top bits. */
+ clz pos, diff
+ lsl data1, data1, pos
+ lsl data2, data2, pos
+ /* But we need to zero-extend (char is unsigned) the value and then
+ perform a signed 32-bit subtraction. */
+ lsr data1, data1, #56
+ sub result, data1, data2, lsr #56
+ ret
+
+.Lmutual_align:
+ /* Sources are mutually aligned, but are not currently at an
+ alignment boundary. Round down the addresses and then mask off
+ the bytes that precede the start point. */
+ bic src1, src1, #7
+ bic src2, src2, #7
+ add limit, limit, tmp1 /* Adjust the limit for the extra. */
+ lsl tmp1, tmp1, #3 /* Bytes beyond alignment -> bits. */
+ ldr data1, [src1], #8
+ neg tmp1, tmp1 /* Bits to alignment -64. */
+ ldr data2, [src2], #8
+ mov tmp2, #~0
+#ifdef __AARCH64EB__
+ /* Big-endian. Early bytes are at MSB. */
+ lsl tmp2, tmp2, tmp1 /* Shift (tmp1 & 63). */
+#else
+ /* Little-endian. Early bytes are at LSB. */
+ lsr tmp2, tmp2, tmp1 /* Shift (tmp1 & 63). */
+#endif
+ add limit_wd, limit, #7
+ orr data1, data1, tmp2
+ orr data2, data2, tmp2
+ lsr limit_wd, limit_wd, #3
+ b .Lstart_realigned
+
+.Lret0:
+ mov result, #0
+ ret
+
+ .p2align 6
+.Lmisaligned8:
+ sub limit, limit, #1
+1:
+ /* Perhaps we can do better than this. */
+ ldrb data1w, [src1], #1
+ ldrb data2w, [src2], #1
+ subs limit, limit, #1
+ ccmp data1w, data2w, #0, cs /* NZCV = 0b0000. */
+ b.eq 1b
+ sub result, data1, data2
+ ret
+END(memcmp)
