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-rw-r--r--arch/alpha/lib/strrchr.S87
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+/*
+ * arch/alpha/lib/strrchr.S
+ * Contributed by Richard Henderson (rth@tamu.edu)
+ *
+ * Return the address of the last occurrence of a given character
+ * within a null-terminated string, or null if it is not found.
+ */
+
+#include <asm/regdef.h>
+
+ .set noreorder
+ .set noat
+
+ .align 3
+ .ent strrchr
+ .globl strrchr
+strrchr:
+ .frame sp, 0, ra
+ .prologue 0
+
+ zapnot a1, 1, a1 # e0 : zero extend our test character
+ mov zero, t6 # .. e1 : t6 is last match aligned addr
+ sll a1, 8, t5 # e0 : replicate our test character
+ mov zero, t8 # .. e1 : t8 is last match byte compare mask
+ or t5, a1, a1 # e0 :
+ ldq_u t0, 0(a0) # .. e1 : load first quadword
+ sll a1, 16, t5 # e0 :
+ andnot a0, 7, v0 # .. e1 : align source addr
+ or t5, a1, a1 # e0 :
+ lda t4, -1 # .. e1 : build garbage mask
+ sll a1, 32, t5 # e0 :
+ cmpbge zero, t0, t1 # .. e1 : bits set iff byte == zero
+ mskqh t4, a0, t4 # e0 :
+ or t5, a1, a1 # .. e1 : character replication complete
+ xor t0, a1, t2 # e0 : make bytes == c zero
+ cmpbge zero, t4, t4 # .. e1 : bits set iff byte is garbage
+ cmpbge zero, t2, t3 # e0 : bits set iff byte == c
+ andnot t1, t4, t1 # .. e1 : clear garbage from null test
+ andnot t3, t4, t3 # e0 : clear garbage from char test
+ bne t1, $eos # .. e1 : did we already hit the terminator?
+
+ /* Character search main loop */
+$loop:
+ ldq t0, 8(v0) # e0 : load next quadword
+ cmovne t3, v0, t6 # .. e1 : save previous comparisons match
+ cmovne t3, t3, t8 # e0 :
+ addq v0, 8, v0 # .. e1 :
+ xor t0, a1, t2 # e0 :
+ cmpbge zero, t0, t1 # .. e1 : bits set iff byte == zero
+ cmpbge zero, t2, t3 # e0 : bits set iff byte == c
+ beq t1, $loop # .. e1 : if we havnt seen a null, loop
+
+ /* Mask out character matches after terminator */
+$eos:
+ negq t1, t4 # e0 : isolate first null byte match
+ and t1, t4, t4 # e1 :
+ subq t4, 1, t5 # e0 : build a mask of the bytes upto...
+ or t4, t5, t4 # e1 : ... and including the null
+
+ and t3, t4, t3 # e0 : mask out char matches after null
+ cmovne t3, t3, t8 # .. e1 : save it, if match found
+ cmovne t3, v0, t6 # e0 :
+
+ /* Locate the address of the last matched character */
+
+ /* Retain the early exit for the ev4 -- the ev5 mispredict penalty
+ is 5 cycles -- the same as just falling through. */
+ beq t8, $retnull # .. e1 :
+
+ and t8, 0xf0, t2 # e0 : binary search for the high bit set
+ cmovne t2, t2, t8 # .. e1 (zdb)
+ cmovne t2, 4, t2 # e0 :
+ and t8, 0xcc, t1 # .. e1 :
+ cmovne t1, t1, t8 # e0 :
+ cmovne t1, 2, t1 # .. e1 :
+ and t8, 0xaa, t0 # e0 :
+ cmovne t0, 1, t0 # .. e1 (zdb)
+ addq t2, t1, t1 # e0 :
+ addq t6, t0, v0 # .. e1 : add our aligned base ptr to the mix
+ addq v0, t1, v0 # e0 :
+ ret # .. e1 :
+
+$retnull:
+ mov zero, v0 # e0 :
+ ret # .. e1 :
+
+ .end strrchr