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authorSrikant Patnaik2015-01-11 12:28:04 +0530
committerSrikant Patnaik2015-01-11 12:28:04 +0530
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tree8718f573808810c2a1e8cb8fb6ac469093ca2784 /ANDROID_3.4.5/arch/alpha/lib/stxcpy.S
parent9d40ac5867b9aefe0722bc1f110b965ff294d30d (diff)
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The original directory structure was scattered and unorganized. Changes are basically to make it look like kernel structure.
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-/*
- * arch/alpha/lib/stxcpy.S
- * Contributed by Richard Henderson (rth@tamu.edu)
- *
- * Copy a null-terminated string from SRC to DST.
- *
- * This is an internal routine used by strcpy, stpcpy, and strcat.
- * As such, it uses special linkage conventions to make implementation
- * of these public functions more efficient.
- *
- * On input:
- * t9 = return address
- * a0 = DST
- * a1 = SRC
- *
- * On output:
- * t12 = bitmask (with one bit set) indicating the last byte written
- * a0 = unaligned address of the last *word* written
- *
- * Furthermore, v0, a3-a5, t11, and t12 are untouched.
- */
-
-#include <asm/regdef.h>
-
- .set noat
- .set noreorder
-
- .text
-
-/* There is a problem with either gdb (as of 4.16) or gas (as of 2.7) that
- doesn't like putting the entry point for a procedure somewhere in the
- middle of the procedure descriptor. Work around this by putting the
- aligned copy in its own procedure descriptor */
-
- .ent stxcpy_aligned
- .align 3
-stxcpy_aligned:
- .frame sp, 0, t9
- .prologue 0
-
- /* On entry to this basic block:
- t0 == the first destination word for masking back in
- t1 == the first source word. */
-
- /* Create the 1st output word and detect 0's in the 1st input word. */
- lda t2, -1 # e1 : build a mask against false zero
- mskqh t2, a1, t2 # e0 : detection in the src word
- mskqh t1, a1, t3 # e0 :
- ornot t1, t2, t2 # .. e1 :
- mskql t0, a1, t0 # e0 : assemble the first output word
- cmpbge zero, t2, t8 # .. e1 : bits set iff null found
- or t0, t3, t1 # e0 :
- bne t8, $a_eos # .. e1 :
-
- /* On entry to this basic block:
- t0 == the first destination word for masking back in
- t1 == a source word not containing a null. */
-
-$a_loop:
- stq_u t1, 0(a0) # e0 :
- addq a0, 8, a0 # .. e1 :
- ldq_u t1, 0(a1) # e0 :
- addq a1, 8, a1 # .. e1 :
- cmpbge zero, t1, t8 # e0 (stall)
- beq t8, $a_loop # .. e1 (zdb)
-
- /* Take care of the final (partial) word store.
- On entry to this basic block we have:
- t1 == the source word containing the null
- t8 == the cmpbge mask that found it. */
-$a_eos:
- negq t8, t6 # e0 : find low bit set
- and t8, t6, t12 # e1 (stall)
-
- /* For the sake of the cache, don't read a destination word
- if we're not going to need it. */
- and t12, 0x80, t6 # e0 :
- bne t6, 1f # .. e1 (zdb)
-
- /* We're doing a partial word store and so need to combine
- our source and original destination words. */
- ldq_u t0, 0(a0) # e0 :
- subq t12, 1, t6 # .. e1 :
- zapnot t1, t6, t1 # e0 : clear src bytes >= null
- or t12, t6, t8 # .. e1 :
- zap t0, t8, t0 # e0 : clear dst bytes <= null
- or t0, t1, t1 # e1 :
-
-1: stq_u t1, 0(a0) # e0 :
- ret (t9) # .. e1 :
-
- .end stxcpy_aligned
-
- .align 3
- .ent __stxcpy
- .globl __stxcpy
-__stxcpy:
- .frame sp, 0, t9
- .prologue 0
-
- /* Are source and destination co-aligned? */
- xor a0, a1, t0 # e0 :
- unop # :
- and t0, 7, t0 # e0 :
- bne t0, $unaligned # .. e1 :
-
- /* We are co-aligned; take care of a partial first word. */
- ldq_u t1, 0(a1) # e0 : load first src word
- and a0, 7, t0 # .. e1 : take care not to load a word ...
- addq a1, 8, a1 # e0 :
- beq t0, stxcpy_aligned # .. e1 : ... if we wont need it
- ldq_u t0, 0(a0) # e0 :
- br stxcpy_aligned # .. e1 :
-
-
-/* The source and destination are not co-aligned. Align the destination
- and cope. We have to be very careful about not reading too much and
- causing a SEGV. */
-
- .align 3
-$u_head:
- /* We know just enough now to be able to assemble the first
- full source word. We can still find a zero at the end of it
- that prevents us from outputting the whole thing.
-
- On entry to this basic block:
- t0 == the first dest word, for masking back in, if needed else 0
- t1 == the low bits of the first source word
- t6 == bytemask that is -1 in dest word bytes */
-
- ldq_u t2, 8(a1) # e0 :
- addq a1, 8, a1 # .. e1 :
-
- extql t1, a1, t1 # e0 :
- extqh t2, a1, t4 # e0 :
- mskql t0, a0, t0 # e0 :
- or t1, t4, t1 # .. e1 :
- mskqh t1, a0, t1 # e0 :
- or t0, t1, t1 # e1 :
-
- or t1, t6, t6 # e0 :
- cmpbge zero, t6, t8 # .. e1 :
- lda t6, -1 # e0 : for masking just below
- bne t8, $u_final # .. e1 :
-
- mskql t6, a1, t6 # e0 : mask out the bits we have
- or t6, t2, t2 # e1 : already extracted before
- cmpbge zero, t2, t8 # e0 : testing eos
- bne t8, $u_late_head_exit # .. e1 (zdb)
-
- /* Finally, we've got all the stupid leading edge cases taken care
- of and we can set up to enter the main loop. */
-
- stq_u t1, 0(a0) # e0 : store first output word
- addq a0, 8, a0 # .. e1 :
- extql t2, a1, t0 # e0 : position ho-bits of lo word
- ldq_u t2, 8(a1) # .. e1 : read next high-order source word
- addq a1, 8, a1 # e0 :
- cmpbge zero, t2, t8 # .. e1 :
- nop # e0 :
- bne t8, $u_eos # .. e1 :
-
- /* Unaligned copy main loop. In order to avoid reading too much,
- the loop is structured to detect zeros in aligned source words.
- This has, unfortunately, effectively pulled half of a loop
- iteration out into the head and half into the tail, but it does
- prevent nastiness from accumulating in the very thing we want
- to run as fast as possible.
-
- On entry to this basic block:
- t0 == the shifted high-order bits from the previous source word
- t2 == the unshifted current source word
-
- We further know that t2 does not contain a null terminator. */
-
- .align 3
-$u_loop:
- extqh t2, a1, t1 # e0 : extract high bits for current word
- addq a1, 8, a1 # .. e1 :
- extql t2, a1, t3 # e0 : extract low bits for next time
- addq a0, 8, a0 # .. e1 :
- or t0, t1, t1 # e0 : current dst word now complete
- ldq_u t2, 0(a1) # .. e1 : load high word for next time
- stq_u t1, -8(a0) # e0 : save the current word
- mov t3, t0 # .. e1 :
- cmpbge zero, t2, t8 # e0 : test new word for eos
- beq t8, $u_loop # .. e1 :
-
- /* We've found a zero somewhere in the source word we just read.
- If it resides in the lower half, we have one (probably partial)
- word to write out, and if it resides in the upper half, we
- have one full and one partial word left to write out.
-
- On entry to this basic block:
- t0 == the shifted high-order bits from the previous source word
- t2 == the unshifted current source word. */
-$u_eos:
- extqh t2, a1, t1 # e0 :
- or t0, t1, t1 # e1 : first (partial) source word complete
-
- cmpbge zero, t1, t8 # e0 : is the null in this first bit?
- bne t8, $u_final # .. e1 (zdb)
-
-$u_late_head_exit:
- stq_u t1, 0(a0) # e0 : the null was in the high-order bits
- addq a0, 8, a0 # .. e1 :
- extql t2, a1, t1 # e0 :
- cmpbge zero, t1, t8 # .. e1 :
-
- /* Take care of a final (probably partial) result word.
- On entry to this basic block:
- t1 == assembled source word
- t8 == cmpbge mask that found the null. */
-$u_final:
- negq t8, t6 # e0 : isolate low bit set
- and t6, t8, t12 # e1 :
-
- and t12, 0x80, t6 # e0 : avoid dest word load if we can
- bne t6, 1f # .. e1 (zdb)
-
- ldq_u t0, 0(a0) # e0 :
- subq t12, 1, t6 # .. e1 :
- or t6, t12, t8 # e0 :
- zapnot t1, t6, t1 # .. e1 : kill source bytes >= null
- zap t0, t8, t0 # e0 : kill dest bytes <= null
- or t0, t1, t1 # e1 :
-
-1: stq_u t1, 0(a0) # e0 :
- ret (t9) # .. e1 :
-
- /* Unaligned copy entry point. */
- .align 3
-$unaligned:
-
- ldq_u t1, 0(a1) # e0 : load first source word
-
- and a0, 7, t4 # .. e1 : find dest misalignment
- and a1, 7, t5 # e0 : find src misalignment
-
- /* Conditionally load the first destination word and a bytemask
- with 0xff indicating that the destination byte is sacrosanct. */
-
- mov zero, t0 # .. e1 :
- mov zero, t6 # e0 :
- beq t4, 1f # .. e1 :
- ldq_u t0, 0(a0) # e0 :
- lda t6, -1 # .. e1 :
- mskql t6, a0, t6 # e0 :
-1:
- subq a1, t4, a1 # .. e1 : sub dest misalignment from src addr
-
- /* If source misalignment is larger than dest misalignment, we need
- extra startup checks to avoid SEGV. */
-
- cmplt t4, t5, t12 # e0 :
- beq t12, $u_head # .. e1 (zdb)
-
- lda t2, -1 # e1 : mask out leading garbage in source
- mskqh t2, t5, t2 # e0 :
- nop # e0 :
- ornot t1, t2, t3 # .. e1 :
- cmpbge zero, t3, t8 # e0 : is there a zero?
- beq t8, $u_head # .. e1 (zdb)
-
- /* At this point we've found a zero in the first partial word of
- the source. We need to isolate the valid source data and mask
- it into the original destination data. (Incidentally, we know
- that we'll need at least one byte of that original dest word.) */
-
- ldq_u t0, 0(a0) # e0 :
-
- negq t8, t6 # .. e1 : build bitmask of bytes <= zero
- and t6, t8, t12 # e0 :
- and a1, 7, t5 # .. e1 :
- subq t12, 1, t6 # e0 :
- or t6, t12, t8 # e1 :
- srl t12, t5, t12 # e0 : adjust final null return value
-
- zapnot t2, t8, t2 # .. e1 : prepare source word; mirror changes
- and t1, t2, t1 # e1 : to source validity mask
- extql t2, a1, t2 # .. e0 :
- extql t1, a1, t1 # e0 :
-
- andnot t0, t2, t0 # .. e1 : zero place for source to reside
- or t0, t1, t1 # e1 : and put it there
- stq_u t1, 0(a0) # .. e0 :
- ret (t9) # e1 :
-
- .end __stxcpy