ARC: String library
Hand optimised asm code for ARC700 pipeline.
Originally written/optimized by Joern Rennecke
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
Cc: Joern Rennecke <joern.rennecke@embecosm.com>
diff --git a/arch/arc/lib/strcmp.S b/arch/arc/lib/strcmp.S
new file mode 100644
index 0000000..5dc802b
--- /dev/null
+++ b/arch/arc/lib/strcmp.S
@@ -0,0 +1,96 @@
+/*
+ * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+/* This is optimized primarily for the ARC700.
+ It would be possible to speed up the loops by one cycle / word
+ respective one cycle / byte by forcing double source 1 alignment, unrolling
+ by a factor of two, and speculatively loading the second word / byte of
+ source 1; however, that would increase the overhead for loop setup / finish,
+ and strcmp might often terminate early. */
+
+#include <asm/linkage.h>
+
+ARC_ENTRY strcmp
+ or r2,r0,r1
+ bmsk_s r2,r2,1
+ brne r2,0,.Lcharloop
+ mov_s r12,0x01010101
+ ror r5,r12
+.Lwordloop:
+ ld.ab r2,[r0,4]
+ ld.ab r3,[r1,4]
+ nop_s
+ sub r4,r2,r12
+ bic r4,r4,r2
+ and r4,r4,r5
+ brne r4,0,.Lfound0
+ breq r2,r3,.Lwordloop
+#ifdef __LITTLE_ENDIAN__
+ xor r0,r2,r3 ; mask for difference
+ sub_s r1,r0,1
+ bic_s r0,r0,r1 ; mask for least significant difference bit
+ sub r1,r5,r0
+ xor r0,r5,r1 ; mask for least significant difference byte
+ and_s r2,r2,r0
+ and_s r3,r3,r0
+#endif /* LITTLE ENDIAN */
+ cmp_s r2,r3
+ mov_s r0,1
+ j_s.d [blink]
+ bset.lo r0,r0,31
+
+ .balign 4
+#ifdef __LITTLE_ENDIAN__
+.Lfound0:
+ xor r0,r2,r3 ; mask for difference
+ or r0,r0,r4 ; or in zero indicator
+ sub_s r1,r0,1
+ bic_s r0,r0,r1 ; mask for least significant difference bit
+ sub r1,r5,r0
+ xor r0,r5,r1 ; mask for least significant difference byte
+ and_s r2,r2,r0
+ and_s r3,r3,r0
+ sub.f r0,r2,r3
+ mov.hi r0,1
+ j_s.d [blink]
+ bset.lo r0,r0,31
+#else /* BIG ENDIAN */
+ /* The zero-detection above can mis-detect 0x01 bytes as zeroes
+ because of carry-propagateion from a lower significant zero byte.
+ We can compensate for this by checking that bit0 is zero.
+ This compensation is not necessary in the step where we
+ get a low estimate for r2, because in any affected bytes
+ we already have 0x00 or 0x01, which will remain unchanged
+ when bit 7 is cleared. */
+ .balign 4
+.Lfound0:
+ lsr r0,r4,8
+ lsr_s r1,r2
+ bic_s r2,r2,r0 ; get low estimate for r2 and get ...
+ bic_s r0,r0,r1 ; <this is the adjusted mask for zeros>
+ or_s r3,r3,r0 ; ... high estimate r3 so that r2 > r3 will ...
+ cmp_s r3,r2 ; ... be independent of trailing garbage
+ or_s r2,r2,r0 ; likewise for r3 > r2
+ bic_s r3,r3,r0
+ rlc r0,0 ; r0 := r2 > r3 ? 1 : 0
+ cmp_s r2,r3
+ j_s.d [blink]
+ bset.lo r0,r0,31
+#endif /* ENDIAN */
+
+ .balign 4
+.Lcharloop:
+ ldb.ab r2,[r0,1]
+ ldb.ab r3,[r1,1]
+ nop_s
+ breq r2,0,.Lcmpend
+ breq r2,r3,.Lcharloop
+.Lcmpend:
+ j_s.d [blink]
+ sub r0,r2,r3
+ARC_EXIT strcmp