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PowerPC LE strnlen 

http://sourceware.org/ml/libc-alpha/2013-08/msg00098.html

The existing strnlen code has a number of defects, so this patch is more
than just adding little-endian support.  The changes here are similar to
those for memchr.

	* sysdeps/powerpc/powerpc64/power7/strnlen.S (strnlen): Add
	little-endian support.  Remove unnecessary "are we done" tests.
	Handle "s" wrapping around zero and extremely large "size".
	Correct main loop count.  Handle single left-over word from main
	loop inline rather than by using small_loop.  Correct comments.
	Delete "zero" tail, use "end_max" instead.
	* sysdeps/powerpc/powerpc32/power7/strnlen.S: Likewise.
This commit is contained in:
Alan Modra 2013-08-17 18:40:48 +09:30
parent db9b4570c5
commit 33ee81de05
3 changed files with 125 additions and 102 deletions
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10
ChangeLog
View File

@ -1,3 +1,13 @@
2013-10-04 Alan Modra <amodra@gmail.com>
* sysdeps/powerpc/powerpc64/power7/strnlen.S (strnlen): Add
little-endian support. Remove unnecessary "are we done" tests.
Handle "s" wrapping around zero and extremely large "size".
Correct main loop count. Handle single left-over word from main
loop inline rather than by using small_loop. Correct comments.
Delete "zero" tail, use "end_max" instead.
* sysdeps/powerpc/powerpc32/power7/strnlen.S: Likewise.
2013-10-04 Alan Modra <amodra@gmail.com> 2013-10-04 Alan Modra <amodra@gmail.com>
* sysdeps/powerpc/powerpc64/power7/strlen.S (strlen): Add little-endian * sysdeps/powerpc/powerpc64/power7/strlen.S (strlen): Add little-endian

106
sysdeps/powerpc/powerpc32/power7/strnlen.S
View File

@ -28,51 +28,47 @@ ENTRY (__strnlen)
add r7,r3,r4 /* Calculate the last acceptable address. */ add r7,r3,r4 /* Calculate the last acceptable address. */
cmplwi r4,16 cmplwi r4,16
li r0,0 /* Word with null chars. */ li r0,0 /* Word with null chars. */
addi r7,r7,-1
ble L(small_range) ble L(small_range)
cmplw cr7,r3,r7 /* Is the address equal or less than r3? If
it's equal or less, it means size is either 0
or a negative number. */
ble cr7,L(proceed)
li r7,-1 /* Make r11 the biggest if r4 <= 0. */
L(proceed):
rlwinm r6,r3,3,27,28 /* Calculate padding. */ rlwinm r6,r3,3,27,28 /* Calculate padding. */
lwz r12,0(r8) /* Load word from memory. */ lwz r12,0(r8) /* Load word from memory. */
cmpb r10,r12,r0 /* Check for null bytes in DWORD1. */ cmpb r10,r12,r0 /* Check for null bytes in DWORD1. */
#ifdef __LITTLE_ENDIAN__
srw r10,r10,r6
slw r10,r10,r6
#else
slw r10,r10,r6 slw r10,r10,r6
srw r10,r10,r6 srw r10,r10,r6
#endif
cmplwi cr7,r10,0 /* If r10 == 0, no null's have been found. */ cmplwi cr7,r10,0 /* If r10 == 0, no null's have been found. */
bne cr7,L(done) bne cr7,L(done)
/* Are we done already? */ clrrwi r7,r7,2 /* Address of last word. */
addi r9,r8,4
cmplw cr6,r9,r7
bge cr6,L(end_max)
mtcrf 0x01,r8 mtcrf 0x01,r8
/* Are we now aligned to a doubleword boundary? If so, skip to /* Are we now aligned to a doubleword boundary? If so, skip to
the main loop. Otherwise, go through the alignment code. */ the main loop. Otherwise, go through the alignment code. */
bt 29,L(loop_setup) bt 29,L(loop_setup)
/* Handle DWORD2 of pair. */ /* Handle WORD2 of pair. */
lwzu r12,4(r8) lwzu r12,4(r8)
cmpb r10,r12,r0 cmpb r10,r12,r0
cmplwi cr7,r10,0 cmplwi cr7,r10,0
bne cr7,L(done) bne cr7,L(done)
/* Are we done already? */
addi r9,r8,4
cmplw cr6,r9,r7
bge cr6,L(end_max)
L(loop_setup): L(loop_setup):
sub r5,r7,r9 /* The last word we want to read in the loop below is the one
containing the last byte of the string, ie. the word at
(s + size - 1) & ~3, or r7. The first word read is at
r8 + 4, we read 2 * cnt words, so the last word read will
be at r8 + 4 + 8 * cnt - 4. Solving for cnt gives
cnt = (r7 - r8) / 8 */
sub r5,r7,r8
srwi r6,r5,3 /* Number of loop iterations. */ srwi r6,r5,3 /* Number of loop iterations. */
mtctr r6 /* Setup the counter. */ mtctr r6 /* Setup the counter. */
b L(loop)
/* Main loop to look for the null byte backwards in the string. Since /* Main loop to look for the null byte in the string. Since
it's a small loop (< 8 instructions), align it to 32-bytes. */ it's a small loop (< 8 instructions), align it to 32-bytes. */
.p2align 5 .p2align 5
L(loop): L(loop):
@ -88,15 +84,18 @@ L(loop):
cmplwi cr7,r5,0 cmplwi cr7,r5,0
bne cr7,L(found) bne cr7,L(found)
bdnz L(loop) bdnz L(loop)
/* We're here because the counter reached 0, and that means we
didn't have any matches for null in the whole range. Just return /* We may have one more word to read. */
the original size. */ cmplw cr6,r8,r7
addi r9,r8,4 beq cr6,L(end_max)
cmplw cr6,r9,r7
blt cr6,L(loop_small) lwzu r12,4(r8)
cmpb r10,r12,r0
cmplwi cr6,r10,0
bne cr6,L(done)
L(end_max): L(end_max):
sub r3,r7,r3 mr r3,r4
blr blr
/* OK, one (or both) of the words contains a null byte. Check /* OK, one (or both) of the words contains a null byte. Check
@ -121,49 +120,56 @@ L(found):
We need to make sure the null char is *before* the end of the We need to make sure the null char is *before* the end of the
range. */ range. */
L(done): L(done):
cntlzw r0,r10 /* Count leading zeroes before the match. */ #ifdef __LITTLE_ENDIAN__
srwi r0,r0,3 /* Convert leading zeroes to bytes. */ addi r0,r10,-1
add r9,r8,r0 andc r0,r0,r10
sub r6,r9,r3 /* Length until the match. */ popcntw r0,r0
cmplw r9,r7 #else
bgt L(end_max) cntlzw r0,r10 /* Count leading zeros before the match. */
mr r3,r6 #endif
sub r3,r8,r3
srwi r0,r0,3 /* Convert leading/trailing zeros to bytes. */
add r3,r3,r0 /* Length until the match. */
cmplw r3,r4
blelr
mr r3,r4
blr blr
.align 4 /* Deals with size <= 16. */
L(zero):
li r3,0
blr
/* Deals with size <= 32. */
.align 4 .align 4
L(small_range): L(small_range):
cmplwi r4,0 cmplwi r4,0
beq L(zero) beq L(end_max)
clrrwi r7,r7,2 /* Address of last word. */
rlwinm r6,r3,3,27,28 /* Calculate padding. */ rlwinm r6,r3,3,27,28 /* Calculate padding. */
lwz r12,0(r8) /* Load word from memory. */ lwz r12,0(r8) /* Load word from memory. */
cmpb r10,r12,r0 /* Check for null bytes in WORD1. */ cmpb r10,r12,r0 /* Check for null bytes in WORD1. */
#ifdef __LITTLE_ENDIAN__
srw r10,r10,r6
slw r10,r10,r6
#else
slw r10,r10,r6 slw r10,r10,r6
srw r10,r10,r6 srw r10,r10,r6
#endif
cmplwi cr7,r10,0 cmplwi cr7,r10,0
bne cr7,L(done) bne cr7,L(done)
addi r9,r8,4 cmplw r8,r7
cmplw r9,r7 beq L(end_max)
bge L(end_max)
b L(loop_small)
.p2align 5 .p2align 5
L(loop_small): L(loop_small):
lwzu r12,4(r8) lwzu r12,4(r8)
cmpb r10,r12,r0 cmpb r10,r12,r0
addi r9,r8,4
cmplwi cr6,r10,0 cmplwi cr6,r10,0
bne cr6,L(done) bne cr6,L(done)
cmplw r9,r7 cmplw r8,r7
bge L(end_max) bne L(loop_small)
b L(loop_small) mr r3,r4
blr
END (__strnlen) END (__strnlen)
weak_alias (__strnlen, strnlen) weak_alias (__strnlen, strnlen)
libc_hidden_builtin_def (strnlen) libc_hidden_builtin_def (strnlen)

109
sysdeps/powerpc/powerpc64/power7/strnlen.S
View File

@ -28,29 +28,25 @@ ENTRY (__strnlen)
add r7,r3,r4 /* Calculate the last acceptable address. */ add r7,r3,r4 /* Calculate the last acceptable address. */
cmpldi r4,32 cmpldi r4,32
li r0,0 /* Doubleword with null chars. */ li r0,0 /* Doubleword with null chars. */
addi r7,r7,-1
/* If we have less than 33 bytes to search, skip to a faster code. */ /* If we have less than 33 bytes to search, skip to a faster code. */
ble L(small_range) ble L(small_range)
cmpld cr7,r3,r7 /* Is the address equal or less than r3? If
it's equal or less, it means size is either 0
or a negative number. */
ble cr7,L(proceed)
li r7,-1 /* Make r11 the biggest if r4 <= 0. */
L(proceed):
rlwinm r6,r3,3,26,28 /* Calculate padding. */ rlwinm r6,r3,3,26,28 /* Calculate padding. */
ld r12,0(r8) /* Load doubleword from memory. */ ld r12,0(r8) /* Load doubleword from memory. */
cmpb r10,r12,r0 /* Check for null bytes in DWORD1. */ cmpb r10,r12,r0 /* Check for null bytes in DWORD1. */
#ifdef __LITTLE_ENDIAN__
srd r10,r10,r6
sld r10,r10,r6
#else
sld r10,r10,r6 sld r10,r10,r6
srd r10,r10,r6 srd r10,r10,r6
#endif
cmpldi cr7,r10,0 /* If r10 == 0, no null's have been found. */ cmpldi cr7,r10,0 /* If r10 == 0, no null's have been found. */
bne cr7,L(done) bne cr7,L(done)
/* Are we done already? */ clrrdi r7,r7,3 /* Address of last doubleword. */
addi r9,r8,8
cmpld cr6,r9,r7
bge cr6,L(end_max)
mtcrf 0x01,r8 mtcrf 0x01,r8
/* Are we now aligned to a quadword boundary? If so, skip to /* Are we now aligned to a quadword boundary? If so, skip to
the main loop. Otherwise, go through the alignment code. */ the main loop. Otherwise, go through the alignment code. */
@ -63,17 +59,18 @@ L(proceed):
cmpldi cr7,r10,0 cmpldi cr7,r10,0
bne cr7,L(done) bne cr7,L(done)
/* Are we done already? */
addi r9,r8,8
cmpld cr6,r9,r7
bge cr6,L(end_max)
L(loop_setup): L(loop_setup):
sub r5,r7,r9 /* The last dword we want to read in the loop below is the one
containing the last byte of the string, ie. the dword at
(s + size - 1) & ~7, or r7. The first dword read is at
r8 + 8, we read 2 * cnt dwords, so the last dword read will
be at r8 + 8 + 16 * cnt - 8. Solving for cnt gives
cnt = (r7 - r8) / 16 */
sub r5,r7,r8
srdi r6,r5,4 /* Number of loop iterations. */ srdi r6,r5,4 /* Number of loop iterations. */
mtctr r6 /* Setup the counter. */ mtctr r6 /* Setup the counter. */
b L(loop)
/* Main loop to look for the null byte backwards in the string. Since /* Main loop to look for the null byte in the string. Since
it's a small loop (< 8 instructions), align it to 32-bytes. */ it's a small loop (< 8 instructions), align it to 32-bytes. */
.p2align 5 .p2align 5
L(loop): L(loop):
@ -89,15 +86,18 @@ L(loop):
cmpldi cr7,r5,0 cmpldi cr7,r5,0
bne cr7,L(found) bne cr7,L(found)
bdnz L(loop) bdnz L(loop)
/* We're here because the counter reached 0, and that means we
didn't have any matches for null in the whole range. Just return /* We may have one more dword to read. */
the original size. */ cmpld cr6,r8,r7
addi r9,r8,8 beq cr6,L(end_max)
cmpld cr6,r9,r7
blt cr6,L(loop_small) ldu r12,8(r8)
cmpb r10,r12,r0
cmpldi cr6,r10,0
bne cr6,L(done)
L(end_max): L(end_max):
sub r3,r7,r3 mr r3,r4
blr blr
/* OK, one (or both) of the doublewords contains a null byte. Check /* OK, one (or both) of the doublewords contains a null byte. Check
@ -119,52 +119,59 @@ L(found):
/* r10 has the output of the cmpb instruction, that is, it contains /* r10 has the output of the cmpb instruction, that is, it contains
0xff in the same position as the null byte in the original 0xff in the same position as the null byte in the original
doubleword from the string. Use that to calculate the length. doubleword from the string. Use that to calculate the length.
We need to make sure the null char is *before* the start of the We need to make sure the null char is *before* the end of the
range (since we're going backwards). */ range. */
L(done): L(done):
cntlzd r0,r10 /* Count leading zeroes before the match. */ #ifdef __LITTLE_ENDIAN__
srdi r0,r0,3 /* Convert leading zeroes to bytes. */ addi r0,r10,-1
add r9,r8,r0 andc r0,r0,r10
sub r6,r9,r3 /* Length until the match. */ popcntd r0,r0
cmpld r9,r7 #else
bgt L(end_max) cntlzd r0,r10 /* Count leading zeros before the match. */
mr r3,r6 #endif
blr sub r3,r8,r3
srdi r0,r0,3 /* Convert leading/trailing zeros to bytes. */
.align 4 add r3,r3,r0 /* Length until the match. */
L(zero): cmpld r3,r4
li r3,0 blelr
mr r3,r4
blr blr
/* Deals with size <= 32. */ /* Deals with size <= 32. */
.align 4 .align 4
L(small_range): L(small_range):
cmpldi r4,0 cmpldi r4,0
beq L(zero) beq L(end_max)
clrrdi r7,r7,3 /* Address of last doubleword. */
rlwinm r6,r3,3,26,28 /* Calculate padding. */ rlwinm r6,r3,3,26,28 /* Calculate padding. */
ld r12,0(r8) /* Load word from memory. */ ld r12,0(r8) /* Load doubleword from memory. */
cmpb r10,r12,r0 /* Check for null bytes in DWORD1. */ cmpb r10,r12,r0 /* Check for null bytes in DWORD1. */
#ifdef __LITTLE_ENDIAN__
srd r10,r10,r6
sld r10,r10,r6
#else
sld r10,r10,r6 sld r10,r10,r6
srd r10,r10,r6 srd r10,r10,r6
#endif
cmpldi cr7,r10,0 cmpldi cr7,r10,0
bne cr7,L(done) bne cr7,L(done)
addi r9,r8,8 cmpld r8,r7
cmpld r9,r7 beq L(end_max)
bge L(end_max)
b L(loop_small)
.p2align 5 .p2align 5
L(loop_small): L(loop_small):
ldu r12,8(r8) ldu r12,8(r8)
cmpb r10,r12,r0 cmpb r10,r12,r0
addi r9,r8,8
cmpldi cr6,r10,0 cmpldi cr6,r10,0
bne cr6,L(done) bne cr6,L(done)
cmpld r9,r7 cmpld r8,r7
bge L(end_max) bne L(loop_small)
b L(loop_small) mr r3,r4
blr
END (__strnlen) END (__strnlen)
weak_alias (__strnlen, strnlen) weak_alias (__strnlen, strnlen)
libc_hidden_builtin_def (strnlen) libc_hidden_builtin_def (strnlen)