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Diffstat (limited to 'MdePkg/Library/BaseMemoryLibOptDxe/Arm/CompareMem.S')
| -rw-r--r-- | MdePkg/Library/BaseMemoryLibOptDxe/Arm/CompareMem.S | 138 |
1 files changed, 138 insertions, 0 deletions
diff --git a/MdePkg/Library/BaseMemoryLibOptDxe/Arm/CompareMem.S b/MdePkg/Library/BaseMemoryLibOptDxe/Arm/CompareMem.S new file mode 100644 index 000000000000..763f54a8b802 --- /dev/null +++ b/MdePkg/Library/BaseMemoryLibOptDxe/Arm/CompareMem.S @@ -0,0 +1,138 @@ +// +// Copyright (c) 2013 - 2016, 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 the Linaro 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. +// + +// Parameters and result. +#define src1 r0 +#define src2 r1 +#define limit r2 +#define result r0 + +// Internal variables. +#define data1 r3 +#define data2 r4 +#define limit_wd r5 +#define diff r6 +#define tmp1 r7 +#define tmp2 r12 +#define pos r8 +#define mask r14 + + .text + .thumb + .syntax unified + .align 5 +ASM_GLOBAL ASM_PFX(InternalMemCompareMem) +ASM_PFX(InternalMemCompareMem): + push {r4-r8, lr} + eor tmp1, src1, src2 + tst tmp1, #3 + bne .Lmisaligned4 + ands tmp1, src1, #3 + bne .Lmutual_align + add limit_wd, limit, #3 + nop.w + lsr limit_wd, limit_wd, #2 + + // Start of performance-critical section -- one 32B cache line. +.Lloop_aligned: + ldr data1, [src1], #4 + ldr data2, [src2], #4 +.Lstart_realigned: + subs limit_wd, limit_wd, #1 + eor diff, data1, data2 // Non-zero if differences found. + cbnz diff, 0f + bne .Lloop_aligned + // End of performance-critical section -- one 32B cache line. + + // Not reached the limit, must have found a diff. +0: cbnz limit_wd, .Lnot_limit + + // Limit % 4 == 0 => all bytes significant. + ands limit, limit, #3 + beq .Lnot_limit + + lsl limit, limit, #3 // Bits -> bytes. + mov mask, #~0 + lsl mask, mask, limit + bic data1, data1, mask + bic data2, data2, mask + + orr diff, diff, mask + +.Lnot_limit: + rev diff, diff + rev data1, data1 + rev data2, data2 + + // The MS-non-zero bit of DIFF marks either the first bit + // that is different, or the end of the significant data. + // Shifting left now will bring the critical information into the + // top bits. + clz pos, diff + lsl data1, data1, pos + lsl data2, data2, pos + + // But we need to zero-extend (char is unsigned) the value and then + // perform a signed 32-bit subtraction. + lsr data1, data1, #28 + sub result, data1, data2, lsr #28 + pop {r4-r8, pc} + +.Lmutual_align: + // Sources are mutually aligned, but are not currently at an + // alignment boundary. Round down the addresses and then mask off + // the bytes that precede the start point. + bic src1, src1, #3 + bic src2, src2, #3 + add limit, limit, tmp1 // Adjust the limit for the extra. + lsl tmp1, tmp1, #3 // Bytes beyond alignment -> bits. + ldr data1, [src1], #4 + rsb tmp1, tmp1, #32 // Bits to alignment -32. + ldr data2, [src2], #4 + mov tmp2, #~0 + + // Little-endian. Early bytes are at LSB. + lsr tmp2, tmp2, tmp1 // Shift (tmp1 & 31). + add limit_wd, limit, #3 + orr data1, data1, tmp2 + orr data2, data2, tmp2 + lsr limit_wd, limit_wd, #2 + b .Lstart_realigned + +.Lmisaligned4: + sub limit, limit, #1 +1: + // Perhaps we can do better than this. + ldrb data1, [src1], #1 + ldrb data2, [src2], #1 + subs limit, limit, #1 + it cs + cmpcs.n data1, data2 + beq 1b + sub result, data1, data2 + pop {r4-r8, pc} |