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/* |
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* Copyright (c) 2014 Travis Geiselbrecht |
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* |
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* Permission is hereby granted, free of charge, to any person obtaining |
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* a copy of this software and associated documentation files |
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* (the "Software"), to deal in the Software without restriction, |
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* including without limitation the rights to use, copy, modify, merge, |
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* publish, distribute, sublicense, and/or sell copies of the Software, |
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* and to permit persons to whom the Software is furnished to do so, |
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* subject to the following conditions: |
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* |
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* The above copyright notice and this permission notice shall be |
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* included in all copies or substantial portions of the Software. |
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* |
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, |
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* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF |
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* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. |
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* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY |
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* CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, |
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* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE |
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* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. |
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*/ |
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//#include <asm.h> |
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//#include <arch/arm/cores.h> |
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#if defined (__ARM_ARCH_7M__) || defined (__ARM_ARCH_7EM__) |
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.global memset |
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.text |
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.syntax unified |
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.thumb |
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.align 2 |
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/* void *memset(void *s, int c, size_t n); */ |
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.type memset, %function |
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.thumb_func |
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memset: |
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//FUNCTION(memset) |
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// save the original pointer |
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push { r0, lr } |
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// check for zero length |
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cbz r2, .L_done |
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// short memsets aren't worth optimizing and make sure we have |
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// enough headroom to try to do dwordwise move optimization |
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cmp r2, #16 |
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blt .L_bytewise |
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// see how many bytes we need to move to align to dword boundaries |
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and r3, r0, #7 |
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cbz r3, .L_prepare_dwordwise |
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rsb r3, #8 |
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subs r2, r3 |
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.L_bytewise_align: |
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// bytewise to align memset |
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subs r3, r3, #1 |
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strb r1, [r0], #1 |
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bgt .L_bytewise_align |
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.L_prepare_dwordwise: |
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// fill a pair of 32 bit registers with the 8 bit value |
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uxtb r1, r1 |
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orr r1, r1, r1, lsl #8 |
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orr r1, r1, r1, lsl #16 |
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mov r12, r1 |
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// load the number of dwords left |
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lsrs r3, r2, #3 |
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.L_dwordwise: |
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// dwordwise memset |
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subs r3, r3, #1 |
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strd r1, r12, [r0], #8 |
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bgt .L_dwordwise |
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// remaining bytes |
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ands r2, #7 |
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beq .L_done |
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.L_bytewise: |
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// bytewise memset |
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subs r2, r2, #1 |
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strb r1, [r0], #1 |
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bgt .L_bytewise |
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.L_done: |
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// restore the base pointer as return value |
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pop { r0, pc } |
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#endif |