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Diffstat (limited to 'MdePkg/Library/BaseMemoryLibOptDxe/Arm/ScanMem.asm')
| -rw-r--r-- | MdePkg/Library/BaseMemoryLibOptDxe/Arm/ScanMem.asm | 147 |
1 files changed, 147 insertions, 0 deletions
diff --git a/MdePkg/Library/BaseMemoryLibOptDxe/Arm/ScanMem.asm b/MdePkg/Library/BaseMemoryLibOptDxe/Arm/ScanMem.asm new file mode 100644 index 0000000000000..bb489f14cf7ee --- /dev/null +++ b/MdePkg/Library/BaseMemoryLibOptDxe/Arm/ScanMem.asm @@ -0,0 +1,147 @@ +; Copyright (c) 2010-2011, Linaro Limited +; All rights reserved. +; +; Redistribution and use in source and binary forms, with or without +; modification, are permitted provided that the following conditions +; are met: +; +; * Redistributions of source code must retain the above copyright +; notice, this list of conditions and the following disclaimer. +; +; * Redistributions in binary form must reproduce the above copyright +; notice, this list of conditions and the following disclaimer in the +; documentation and/or other materials provided with the distribution. +; +; * Neither the name of Linaro Limited nor the names of its +; contributors may be used to endorse or promote products derived +; from this software without specific prior written permission. +; +; THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS +; "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT +; LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR +; A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT +; HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, +; SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT +; LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, +; DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY +; THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT +; (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE +; OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. +; + +; +; Written by Dave Gilbert <david.gilbert@linaro.org> +; +; This memchr routine is optimised on a Cortex-A9 and should work on +; all ARMv7 processors. It has a fast past for short sizes, and has +; an optimised path for large data sets; the worst case is finding the +; match early in a large data set. +; + + +; 2011-02-07 david.gilbert@linaro.org +; Extracted from local git a5b438d861 +; 2011-07-14 david.gilbert@linaro.org +; Import endianness fix from local git ea786f1b +; 2011-12-07 david.gilbert@linaro.org +; Removed unneeded cbz from align loop + +; this lets us check a flag in a 00/ff byte easily in either endianness +#define CHARTSTMASK(c) 1<<(c*8) + + EXPORT InternalMemScanMem8 + AREA ScanMem, CODE, READONLY + THUMB + +InternalMemScanMem8 + ; r0 = start of memory to scan + ; r1 = length + ; r2 = character to look for + ; returns r0 = pointer to character or NULL if not found + uxtb r2, r2 ; Don't think we can trust the caller to actually pass a char + + cmp r1, #16 ; If it's short don't bother with anything clever + blt L20 + + tst r0, #7 ; If it's already aligned skip the next bit + beq L10 + + ; Work up to an aligned point +L5 + ldrb r3, [r0],#1 + subs r1, r1, #1 + cmp r3, r2 + beq L50 ; If it matches exit found + tst r0, #7 + bne L5 ; If not aligned yet then do next byte + +L10 + ; At this point, we are aligned, we know we have at least 8 bytes to work with + push {r4-r7} + orr r2, r2, r2, lsl #8 ; expand the match word across to all bytes + orr r2, r2, r2, lsl #16 + bic r4, r1, #7 ; Number of double words to work with + mvns r7, #0 ; all F's + movs r3, #0 + +L15 + ldmia r0!, {r5,r6} + subs r4, r4, #8 + eor r5, r5, r2 ; Get it so that r5,r6 have 00's where the bytes match the target + eor r6, r6, r2 + uadd8 r5, r5, r7 ; Parallel add 0xff - sets the GE bits for anything that wasn't 0 + sel r5, r3, r7 ; bytes are 00 for none-00 bytes, or ff for 00 bytes - NOTE INVERSION + uadd8 r6, r6, r7 ; Parallel add 0xff - sets the GE bits for anything that wasn't 0 + sel r6, r5, r7 ; chained....bytes are 00 for none-00 bytes, or ff for 00 bytes - NOTE INVERSION + cbnz r6, L60 + bne L15 ; (Flags from the subs above) If not run out of bytes then go around again + + pop {r4-r7} + and r2, r2, #0xff ; Get r2 back to a single character from the expansion above + and r1, r1, #7 ; Leave the count remaining as the number after the double words have been done + +L20 + cbz r1, L40 ; 0 length or hit the end already then not found + +L21 ; Post aligned section, or just a short call + ldrb r3, [r0], #1 + subs r1, r1, #1 + eor r3, r3, r2 ; r3 = 0 if match - doesn't break flags from sub + cbz r3, L50 + bne L21 ; on r1 flags + +L40 + movs r0, #0 ; not found + bx lr + +L50 + subs r0, r0, #1 ; found + bx lr + +L60 ; We're here because the fast path found a hit - now we have to track down exactly which word it was + ; r0 points to the start of the double word after the one that was tested + ; r5 has the 00/ff pattern for the first word, r6 has the chained value + cmp r5, #0 + itte eq + moveq r5, r6 ; the end is in the 2nd word + subeq r0, r0, #3 ; Points to 2nd byte of 2nd word + subne r0, r0, #7 ; or 2nd byte of 1st word + + ; r0 currently points to the 3rd byte of the word containing the hit + tst r5, #CHARTSTMASK(0) ; 1st character + bne L61 + adds r0, r0, #1 + tst r5, #CHARTSTMASK(1) ; 2nd character + ittt eq + addeq r0, r0 ,#1 + tsteq r5, #(3 << 15) ; 2nd & 3rd character + ; If not the 3rd must be the last one + addeq r0, r0, #1 + +L61 + pop {r4-r7} + subs r0, r0, #1 + bx lr + + END + |