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authorLinus Torvalds <torvalds@ppc970.osdl.org>2005-04-16 15:20:36 -0700
committerLinus Torvalds <torvalds@ppc970.osdl.org>2005-04-16 15:20:36 -0700
commit1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 (patch)
tree0bba044c4ce775e45a88a51686b5d9f90697ea9d /arch/alpha/lib/ev67-strchr.S
downloadconfigs-2.6.12-rc2.tar.gz
Linux-2.6.12-rc2v2.6.12-rc2
Initial git repository build. I'm not bothering with the full history, even though we have it. We can create a separate "historical" git archive of that later if we want to, and in the meantime it's about 3.2GB when imported into git - space that would just make the early git days unnecessarily complicated, when we don't have a lot of good infrastructure for it. Let it rip!
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+/*
+ * arch/alpha/lib/ev67-strchr.S
+ * 21264 version contributed by Rick Gorton <rick.gorton@alpha-processor.com>
+ *
+ * Return the address of a given character within a null-terminated
+ * string, or null if it is not found.
+ *
+ * Much of the information about 21264 scheduling/coding comes from:
+ * Compiler Writer's Guide for the Alpha 21264
+ * abbreviated as 'CWG' in other comments here
+ * ftp.digital.com/pub/Digital/info/semiconductor/literature/dsc-library.html
+ * Scheduling notation:
+ * E - either cluster
+ * U - upper subcluster; U0 - subcluster U0; U1 - subcluster U1
+ * L - lower subcluster; L0 - subcluster L0; L1 - subcluster L1
+ * Try not to change the actual algorithm if possible for consistency.
+ */
+
+#include <asm/regdef.h>
+
+ .set noreorder
+ .set noat
+
+ .align 4
+ .globl strchr
+ .ent strchr
+strchr:
+ .frame sp, 0, ra
+ .prologue 0
+
+ ldq_u t0, 0(a0) # L : load first quadword Latency=3
+ and a1, 0xff, t3 # E : 00000000000000ch
+ insbl a1, 1, t5 # U : 000000000000ch00
+ insbl a1, 7, a2 # U : ch00000000000000
+
+ insbl t3, 6, a3 # U : 00ch000000000000
+ or t5, t3, a1 # E : 000000000000chch
+ andnot a0, 7, v0 # E : align our loop pointer
+ lda t4, -1 # E : build garbage mask
+
+ mskqh t4, a0, t4 # U : only want relevant part of first quad
+ or a2, a3, a2 # E : chch000000000000
+ inswl a1, 2, t5 # E : 00000000chch0000
+ inswl a1, 4, a3 # E : 0000chch00000000
+
+ or a1, a2, a1 # E : chch00000000chch
+ or a3, t5, t5 # E : 0000chchchch0000
+ cmpbge zero, t0, t2 # E : bits set iff byte == zero
+ cmpbge zero, t4, t4 # E : bits set iff byte is garbage
+
+ /* This quad is _very_ serialized. Lots of stalling happens */
+ or t5, a1, a1 # E : chchchchchchchch
+ xor t0, a1, t1 # E : make bytes == c zero
+ cmpbge zero, t1, t3 # E : bits set iff byte == c
+ or t2, t3, t0 # E : bits set iff char match or zero match
+
+ andnot t0, t4, t0 # E : clear garbage bits
+ cttz t0, a2 # U0 : speculative (in case we get a match)
+ nop # E :
+ bne t0, $found # U :
+
+ /*
+ * Yuk. This loop is going to stall like crazy waiting for the
+ * data to be loaded. Not much can be done about it unless it's
+ * unrolled multiple times - is that safe to do in kernel space?
+ * Or would exception handling recovery code do the trick here?
+ */
+$loop: ldq t0, 8(v0) # L : Latency=3
+ addq v0, 8, v0 # E :
+ xor t0, a1, t1 # E :
+ cmpbge zero, t0, t2 # E : bits set iff byte == 0
+
+ cmpbge zero, t1, t3 # E : bits set iff byte == c
+ or t2, t3, t0 # E :
+ cttz t3, a2 # U0 : speculative (in case we get a match)
+ beq t0, $loop # U :
+
+$found: negq t0, t1 # E : clear all but least set bit
+ and t0, t1, t0 # E :
+ and t0, t3, t1 # E : bit set iff byte was the char
+ addq v0, a2, v0 # E : Add in the bit number from above
+
+ cmoveq t1, $31, v0 # E : Two mapping slots, latency = 2
+ nop
+ nop
+ ret # L0 :
+
+ .end strchr