diff options
Diffstat (limited to 'Core/MdePkg/Library/BaseMemoryLibOptDxe/Arm/ScanMem.S')
| -rw-r--r-- | Core/MdePkg/Library/BaseMemoryLibOptDxe/Arm/ScanMem.S | 148 |
1 files changed, 148 insertions, 0 deletions
diff --git a/Core/MdePkg/Library/BaseMemoryLibOptDxe/Arm/ScanMem.S b/Core/MdePkg/Library/BaseMemoryLibOptDxe/Arm/ScanMem.S new file mode 100644 index 0000000000..5dcf153a61 --- /dev/null +++ b/Core/MdePkg/Library/BaseMemoryLibOptDxe/Arm/ScanMem.S @@ -0,0 +1,148 @@ +// 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)
+
+ .text
+ .thumb
+ .syntax unified
+
+ .type ASM_PFX(InternalMemScanMem8), %function
+ASM_GLOBAL ASM_PFX(InternalMemScanMem8)
+ASM_PFX(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 20f
+
+ tst r0, #7 // If it's already aligned skip the next bit
+ beq 10f
+
+ // Work up to an aligned point
+5:
+ ldrb r3, [r0],#1
+ subs r1, r1, #1
+ cmp r3, r2
+ beq 50f // If it matches exit found
+ tst r0, #7
+ bne 5b // If not aligned yet then do next byte
+
+10:
+ // 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
+
+15:
+ 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, 60f
+ bne 15b // (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
+
+20:
+ cbz r1, 40f // 0 length or hit the end already then not found
+
+21: // 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, 50f
+ bne 21b // on r1 flags
+
+40:
+ movs r0, #0 // not found
+ bx lr
+
+50:
+ subs r0, r0, #1 // found
+ bx lr
+
+60: // 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
+ subs r0, r0, #3
+ cmp r5, #0
+ it eq
+ moveq.n r5, r6 // the end is in the 2nd word
+ it ne
+ subne.n r0, r0, #4 // 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 61f
+ adds r0, r0, #1
+ tst r5, #CHARTSTMASK(1) // 2nd character
+ bne 61f
+ adds r0, r0 ,#1
+ tst r5, #(3 << 15) // 2nd & 3rd character
+ // If not the 3rd must be the last one
+ it eq
+ addeq.n r0, r0, #1
+
+61:
+ pop {r4-r7}
+ subs r0, r0, #1
+ bx lr
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