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* sysdeps/alpha/strncmp.S: Don't read too much data when pointers 

are co-aligned, and count is aligned with the end of the word.
This commit is contained in:
Richard Henderson 2005-11-27 06:05:33 +00:00
parent 971a928ce0
commit a6b36472ee
1 changed files with 28 additions and 5 deletions
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33
sysdeps/alpha/strncmp.S
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@ -61,8 +61,10 @@ $aligned:
ornot t0, t3, t0 # .. e1 :
cmpbge zero, t1, t7 # e0 : bits set iff null found
beq a2, $eoc # .. e1 : check end of count
subq a2, 1, a2 # e0 :
unop # e0 :
bne t7, $eos # .. e1 :
unop # e0 :
beq t10, $ant_loop # .. e1 :
/* Aligned compare main loop.
On entry to this basic block:
@ -74,13 +76,30 @@ $a_loop:
bne t2, $wordcmp # .. e1 (zdb)
ldq_u t1, 8(a1) # e0 :
ldq_u t0, 8(a0) # .. e1 :
subq a2, 1, a2 # e0 :
addq a1, 8, a1 # .. e1 :
addq a0, 8, a0 # e0 :
beq a2, $eoc # .. e1 :
cmpbge zero, t1, t7 # e0 :
beq t7, $a_loop # .. e1 :
unop # e0 :
br $eos # .. e1 :
/* Alternate aligned compare loop, for when there's no trailing
bytes on the count. We have to avoid reading too much data. */
$ant_loop:
xor t0, t1, t2 # e0 :
bne t2, $wordcmp # .. e1 (zdb)
subq a2, 1, a2 # e0 :
beq a2, $zerolength # .. e1 :
ldq_u t1, 8(a1) # e0 :
ldq_u t0, 8(a0) # .. e1 :
addq a1, 8, a1 # e0 :
addq a0, 8, a0 # .. e1 :
cmpbge zero, t1, t7 # e0 :
beq a2, $eoc # .. e1 :
subq a2, 1, a2 # e0 :
beq t7, $a_loop # .. e1 :
br $eos # e1 :
beq t7, $ant_loop # .. e1 :
unop # e0 :
br $eos # .. e1 :
/* The two strings are not co-aligned. Align s1 and cope. */
$unaligned:
@ -184,6 +203,8 @@ $u_final:
$eoc:
mskql t0, t10, t0
mskql t1, t10, t1
unop
cmpbge zero, t1, t7
/* We've found a zero somewhere in a word we just read.
On entry to this basic block:
@ -203,6 +224,7 @@ $eos:
/* Here we have two differing co-aligned words in t0 & t1.
Bytewise compare them and return (t0 > t1 ? 1 : -1). */
.align 3
$wordcmp:
cmpbge t0, t1, t2 # e0 : comparison yields bit mask of ge
cmpbge t1, t0, t3 # .. e1 :
@ -216,6 +238,7 @@ $wordcmp:
$done:
ret # e1 :
.align 3
$zerolength:
clr v0
ret