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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
parent
db9b4570c5
commit
33ee81de05
10
ChangeLog
10
ChangeLog
@ -1,3 +1,13 @@
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2013-10-04 Alan Modra <amodra@gmail.com>
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* sysdeps/powerpc/powerpc64/power7/strnlen.S (strnlen): Add
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little-endian support. Remove unnecessary "are we done" tests.
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Handle "s" wrapping around zero and extremely large "size".
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Correct main loop count. Handle single left-over word from main
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loop inline rather than by using small_loop. Correct comments.
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Delete "zero" tail, use "end_max" instead.
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* sysdeps/powerpc/powerpc32/power7/strnlen.S: Likewise.
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2013-10-04 Alan Modra <amodra@gmail.com>
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* sysdeps/powerpc/powerpc64/power7/strlen.S (strlen): Add little-endian
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@ -28,51 +28,47 @@ ENTRY (__strnlen)
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add r7,r3,r4 /* Calculate the last acceptable address. */
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cmplwi r4,16
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li r0,0 /* Word with null chars. */
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addi r7,r7,-1
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ble L(small_range)
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cmplw cr7,r3,r7 /* Is the address equal or less than r3? If
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it's equal or less, it means size is either 0
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or a negative number. */
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ble cr7,L(proceed)
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li r7,-1 /* Make r11 the biggest if r4 <= 0. */
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L(proceed):
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rlwinm r6,r3,3,27,28 /* Calculate padding. */
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lwz r12,0(r8) /* Load word from memory. */
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cmpb r10,r12,r0 /* Check for null bytes in DWORD1. */
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#ifdef __LITTLE_ENDIAN__
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srw r10,r10,r6
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slw r10,r10,r6
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#else
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slw r10,r10,r6
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srw r10,r10,r6
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#endif
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cmplwi cr7,r10,0 /* If r10 == 0, no null's have been found. */
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bne cr7,L(done)
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/* Are we done already? */
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addi r9,r8,4
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cmplw cr6,r9,r7
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bge cr6,L(end_max)
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clrrwi r7,r7,2 /* Address of last word. */
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mtcrf 0x01,r8
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/* Are we now aligned to a doubleword boundary? If so, skip to
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the main loop. Otherwise, go through the alignment code. */
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bt 29,L(loop_setup)
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/* Handle DWORD2 of pair. */
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/* Handle WORD2 of pair. */
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lwzu r12,4(r8)
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cmpb r10,r12,r0
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cmplwi cr7,r10,0
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bne cr7,L(done)
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/* Are we done already? */
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addi r9,r8,4
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cmplw cr6,r9,r7
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bge cr6,L(end_max)
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L(loop_setup):
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sub r5,r7,r9
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/* The last word we want to read in the loop below is the one
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containing the last byte of the string, ie. the word at
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(s + size - 1) & ~3, or r7. The first word read is at
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r8 + 4, we read 2 * cnt words, so the last word read will
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be at r8 + 4 + 8 * cnt - 4. Solving for cnt gives
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cnt = (r7 - r8) / 8 */
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sub r5,r7,r8
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srwi r6,r5,3 /* Number of loop iterations. */
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mtctr r6 /* Setup the counter. */
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b L(loop)
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/* Main loop to look for the null byte backwards in the string. Since
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/* Main loop to look for the null byte in the string. Since
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it's a small loop (< 8 instructions), align it to 32-bytes. */
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.p2align 5
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L(loop):
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@ -88,15 +84,18 @@ L(loop):
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cmplwi cr7,r5,0
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bne cr7,L(found)
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bdnz L(loop)
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/* We're here because the counter reached 0, and that means we
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didn't have any matches for null in the whole range. Just return
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the original size. */
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addi r9,r8,4
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cmplw cr6,r9,r7
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blt cr6,L(loop_small)
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/* We may have one more word to read. */
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cmplw cr6,r8,r7
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beq cr6,L(end_max)
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lwzu r12,4(r8)
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cmpb r10,r12,r0
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cmplwi cr6,r10,0
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bne cr6,L(done)
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L(end_max):
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sub r3,r7,r3
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mr r3,r4
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blr
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/* OK, one (or both) of the words contains a null byte. Check
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@ -121,49 +120,56 @@ L(found):
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We need to make sure the null char is *before* the end of the
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range. */
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L(done):
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cntlzw r0,r10 /* Count leading zeroes before the match. */
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srwi r0,r0,3 /* Convert leading zeroes to bytes. */
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add r9,r8,r0
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sub r6,r9,r3 /* Length until the match. */
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cmplw r9,r7
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bgt L(end_max)
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mr r3,r6
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#ifdef __LITTLE_ENDIAN__
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addi r0,r10,-1
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andc r0,r0,r10
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popcntw r0,r0
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#else
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cntlzw r0,r10 /* Count leading zeros before the match. */
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#endif
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sub r3,r8,r3
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srwi r0,r0,3 /* Convert leading/trailing zeros to bytes. */
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add r3,r3,r0 /* Length until the match. */
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cmplw r3,r4
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blelr
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mr r3,r4
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blr
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.align 4
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L(zero):
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li r3,0
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blr
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/* Deals with size <= 32. */
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/* Deals with size <= 16. */
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.align 4
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L(small_range):
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cmplwi r4,0
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beq L(zero)
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beq L(end_max)
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clrrwi r7,r7,2 /* Address of last word. */
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rlwinm r6,r3,3,27,28 /* Calculate padding. */
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lwz r12,0(r8) /* Load word from memory. */
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cmpb r10,r12,r0 /* Check for null bytes in WORD1. */
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#ifdef __LITTLE_ENDIAN__
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srw r10,r10,r6
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slw r10,r10,r6
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#else
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slw r10,r10,r6
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srw r10,r10,r6
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#endif
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cmplwi cr7,r10,0
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bne cr7,L(done)
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addi r9,r8,4
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cmplw r9,r7
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bge L(end_max)
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b L(loop_small)
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cmplw r8,r7
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beq L(end_max)
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.p2align 5
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L(loop_small):
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lwzu r12,4(r8)
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cmpb r10,r12,r0
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addi r9,r8,4
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cmplwi cr6,r10,0
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bne cr6,L(done)
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cmplw r9,r7
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bge L(end_max)
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b L(loop_small)
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cmplw r8,r7
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bne L(loop_small)
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mr r3,r4
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blr
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END (__strnlen)
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weak_alias (__strnlen, strnlen)
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libc_hidden_builtin_def (strnlen)
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@ -24,33 +24,29 @@
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ENTRY (__strnlen)
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CALL_MCOUNT 2
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dcbt 0,r3
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clrrdi r8,r3,3
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clrrdi r8,r3,3
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add r7,r3,r4 /* Calculate the last acceptable address. */
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cmpldi r4,32
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li r0,0 /* Doubleword with null chars. */
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addi r7,r7,-1
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/* If we have less than 33 bytes to search, skip to a faster code. */
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ble L(small_range)
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cmpld cr7,r3,r7 /* Is the address equal or less than r3? If
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it's equal or less, it means size is either 0
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or a negative number. */
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ble cr7,L(proceed)
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li r7,-1 /* Make r11 the biggest if r4 <= 0. */
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L(proceed):
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rlwinm r6,r3,3,26,28 /* Calculate padding. */
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ld r12,0(r8) /* Load doubleword from memory. */
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cmpb r10,r12,r0 /* Check for null bytes in DWORD1. */
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#ifdef __LITTLE_ENDIAN__
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srd r10,r10,r6
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sld r10,r10,r6
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#else
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sld r10,r10,r6
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srd r10,r10,r6
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#endif
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cmpldi cr7,r10,0 /* If r10 == 0, no null's have been found. */
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bne cr7,L(done)
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/* Are we done already? */
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addi r9,r8,8
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cmpld cr6,r9,r7
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bge cr6,L(end_max)
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clrrdi r7,r7,3 /* Address of last doubleword. */
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mtcrf 0x01,r8
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/* Are we now aligned to a quadword boundary? If so, skip to
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the main loop. Otherwise, go through the alignment code. */
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@ -63,17 +59,18 @@ L(proceed):
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cmpldi cr7,r10,0
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bne cr7,L(done)
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/* Are we done already? */
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addi r9,r8,8
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cmpld cr6,r9,r7
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bge cr6,L(end_max)
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L(loop_setup):
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sub r5,r7,r9
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/* The last dword we want to read in the loop below is the one
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containing the last byte of the string, ie. the dword at
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(s + size - 1) & ~7, or r7. The first dword read is at
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r8 + 8, we read 2 * cnt dwords, so the last dword read will
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be at r8 + 8 + 16 * cnt - 8. Solving for cnt gives
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cnt = (r7 - r8) / 16 */
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sub r5,r7,r8
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srdi r6,r5,4 /* Number of loop iterations. */
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mtctr r6 /* Setup the counter. */
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b L(loop)
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/* Main loop to look for the null byte backwards in the string. Since
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/* Main loop to look for the null byte in the string. Since
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it's a small loop (< 8 instructions), align it to 32-bytes. */
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.p2align 5
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L(loop):
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@ -89,15 +86,18 @@ L(loop):
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cmpldi cr7,r5,0
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bne cr7,L(found)
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bdnz L(loop)
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/* We're here because the counter reached 0, and that means we
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didn't have any matches for null in the whole range. Just return
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the original size. */
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addi r9,r8,8
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cmpld cr6,r9,r7
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blt cr6,L(loop_small)
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/* We may have one more dword to read. */
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cmpld cr6,r8,r7
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beq cr6,L(end_max)
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ldu r12,8(r8)
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cmpb r10,r12,r0
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cmpldi cr6,r10,0
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bne cr6,L(done)
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L(end_max):
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sub r3,r7,r3
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mr r3,r4
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blr
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/* OK, one (or both) of the doublewords contains a null byte. Check
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@ -119,52 +119,59 @@ L(found):
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/* r10 has the output of the cmpb instruction, that is, it contains
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0xff in the same position as the null byte in the original
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doubleword from the string. Use that to calculate the length.
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We need to make sure the null char is *before* the start of the
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range (since we're going backwards). */
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We need to make sure the null char is *before* the end of the
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range. */
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L(done):
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cntlzd r0,r10 /* Count leading zeroes before the match. */
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srdi r0,r0,3 /* Convert leading zeroes to bytes. */
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add r9,r8,r0
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sub r6,r9,r3 /* Length until the match. */
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cmpld r9,r7
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bgt L(end_max)
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mr r3,r6
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blr
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.align 4
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L(zero):
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li r3,0
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#ifdef __LITTLE_ENDIAN__
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addi r0,r10,-1
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andc r0,r0,r10
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popcntd r0,r0
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#else
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cntlzd r0,r10 /* Count leading zeros before the match. */
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#endif
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sub r3,r8,r3
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srdi r0,r0,3 /* Convert leading/trailing zeros to bytes. */
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add r3,r3,r0 /* Length until the match. */
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cmpld r3,r4
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blelr
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mr r3,r4
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blr
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/* Deals with size <= 32. */
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.align 4
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L(small_range):
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cmpldi r4,0
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beq L(zero)
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beq L(end_max)
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clrrdi r7,r7,3 /* Address of last doubleword. */
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rlwinm r6,r3,3,26,28 /* Calculate padding. */
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ld r12,0(r8) /* Load word from memory. */
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ld r12,0(r8) /* Load doubleword from memory. */
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cmpb r10,r12,r0 /* Check for null bytes in DWORD1. */
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#ifdef __LITTLE_ENDIAN__
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srd r10,r10,r6
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sld r10,r10,r6
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#else
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sld r10,r10,r6
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srd r10,r10,r6
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#endif
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cmpldi cr7,r10,0
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bne cr7,L(done)
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addi r9,r8,8
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cmpld r9,r7
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bge L(end_max)
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b L(loop_small)
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cmpld r8,r7
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beq L(end_max)
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.p2align 5
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L(loop_small):
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ldu r12,8(r8)
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cmpb r10,r12,r0
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addi r9,r8,8
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cmpldi cr6,r10,0
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bne cr6,L(done)
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cmpld r9,r7
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bge L(end_max)
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b L(loop_small)
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cmpld r8,r7
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bne L(loop_small)
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mr r3,r4
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blr
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END (__strnlen)
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weak_alias (__strnlen, strnlen)
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libc_hidden_builtin_def (strnlen)
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