diff options
Diffstat (limited to 'sysdeps/powerpc/powerpc32/power7/memchr.S')
| -rw-r--r-- | sysdeps/powerpc/powerpc32/power7/memchr.S | 78 |
1 files changed, 58 insertions, 20 deletions
diff --git a/sysdeps/powerpc/powerpc32/power7/memchr.S b/sysdeps/powerpc/powerpc32/power7/memchr.S index 85cc2999ae..ca2bc49579 100644 --- a/sysdeps/powerpc/powerpc32/power7/memchr.S +++ b/sysdeps/powerpc/powerpc32/power7/memchr.S @@ -1,5 +1,5 @@ /* Optimized memchr implementation for PowerPC32/POWER7 using cmpb insn. - Copyright (C) 2010 Free Software Foundation, Inc. + Copyright (C) 2010-2012 Free Software Foundation, Inc. Contributed by Luis Machado <luisgpm@br.ibm.com>. This file is part of the GNU C Library. @@ -33,19 +33,23 @@ ENTRY (BP_SYM (__memchr)) cmplwi r5,16 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. */ + cmplw cr7,r3,r7 /* Compare the starting address (r3) with the + ending address (r7). If (r3 >= r7), the size + passed in is zero or negative. */ ble cr7,L(proceed) - li r7,-1 /* Make r11 the biggest if r4 <= 0. */ + li r7,-1 /* Artificially set our ending address (r7) + such that we will exit early. */ L(proceed): rlwinm r6,r3,3,27,28 /* Calculate padding. */ + cmpli cr6,r6,0 /* cr6 == Do we have padding? */ lwz r12,0(r8) /* Load word from memory. */ cmpb r10,r12,r4 /* Check for BYTE's in WORD1. */ + beq cr6,L(proceed_no_padding) slw r10,r10,r6 srw r10,r10,r6 - cmplwi cr7,r10,0 /* If r10 == 0, no BYTE's have been found. */ +L(proceed_no_padding): + cmplwi cr7,r10,0 /* If r10 == 0, no BYTEs have been found. */ bne cr7,L(done) /* Are we done already? */ @@ -73,7 +77,7 @@ L(proceed): L(loop_setup): sub r5,r7,r9 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 BYTE backwards in the string. Since it's a small loop (< 8 instructions), align it to 32-bytes. */ @@ -82,7 +86,6 @@ L(loop): /* Load two words, compare and merge in a single register for speed. This is an attempt to speed up the byte-checking process for bigger strings. */ - lwz r12,4(r8) lwzu r11,8(r8) cmpb r10,r12,r4 @@ -91,11 +94,11 @@ L(loop): cmplwi cr7,r5,0 bne cr7,L(found) bdnz L(loop) + /* We're here because the counter reached 0, and that means we - didn't have any matches for BYTE in the whole range. Just - return the original range. */ - addi r9,r8,4 - cmplw cr6,r9,r7 + didn't have any matches for BYTE in the whole range. */ + subi r11,r7,4 + cmplw cr6,r8,r11 blt cr6,L(loop_small) b L(null) @@ -118,8 +121,7 @@ L(found): /* r10 has the output of the cmpb instruction, that is, it contains 0xff in the same position as BYTE in the original word from the string. Use that to calculate the pointer. - We need to make sure BYTE is *before* the end of the - range. */ + We need to make sure BYTE is *before* the end of the range. */ L(done): cntlzw r0,r10 /* Count leading zeroes before the match. */ srwi r0,r0,3 /* Convert leading zeroes to bytes. */ @@ -137,13 +139,15 @@ L(null): .align 4 L(small_range): cmplwi r5,0 - beq L(null) - rlwinm r6,r3,3,27,28 /* Calculate padding. */ + beq L(null) /* This branch is for the cmplwi r5,0 above */ lwz r12,0(r8) /* Load word from memory. */ + cmplwi cr6,r6,0 /* cr6 == Do we have padding? */ cmpb r10,r12,r4 /* Check for BYTE in DWORD1. */ + beq cr6,L(small_no_padding) slw r10,r10,r6 srw r10,r10,r6 +L(small_no_padding): cmplwi cr7,r10,0 bne cr7,L(done) @@ -151,18 +155,52 @@ L(small_range): addi r9,r8,4 cmplw r9,r7 bge L(null) - b L(loop_small) - .p2align 5 -L(loop_small): +L(loop_small): /* loop_small has been unrolled. */ lwzu r12,4(r8) cmpb r10,r12,r4 addi r9,r8,4 cmplwi cr6,r10,0 + cmplw r9,r7 bne cr6,L(done) + bge L(null) + + lwzu r12,4(r8) + cmpb r10,r12,r4 + addi r9,r8,4 + cmplwi cr6,r10,0 cmplw r9,r7 + bne cr6,L(done) bge L(null) - b L(loop_small) + + lwzu r12,4(r8) + cmpb r10,r12,r4 + addi r9,r8,4 + cmplwi cr6,r10,0 + cmplw r9,r7 + bne cr6,L(done) + bge L(null) + + lwzu r12,4(r8) + cmpb r10,r12,r4 + addi r9,r8,4 + cmplwi cr6,r10,0 + cmplw r9,r7 + bne cr6,L(done) + bge L(null) + + /* For most cases we will never get here. Under some combinations of + padding + length there is a leftover word that still needs to be + checked. */ + lwzu r12,4(r8) + cmpb r10,r12,r4 + addi r9,r8,4 + cmplwi cr6,r10,0 + bne cr6,L(done) + + /* save a branch and exit directly */ + li r3,0 + blr END (BP_SYM (__memchr)) weak_alias (BP_SYM (__memchr), BP_SYM(memchr)) |