mirror of https://github.com/ARMmbed/mbed-os.git
Asm versions of netstack memcpy() and lwip_standard_chksum()
For tests such as TCPEchoServer (http://mbed.org/users/emilmont/notebook/networking-libraries-benchmark/) this change showed a 28% improvement (14Mbps to 18Mbps) when the echo test was modified to instead use 1K data buffers. I targetted these two functions based on manual profiling samples which showed that a great deal of time was being spent in these two functions when the network stack was being slammed with UDP packets.pull/51/head
Adam Green
parent
e23be8a1b3
commit
7dddd9e578
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@ -82,8 +82,21 @@ typedef uintptr_t mem_ptr_t;
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#define ALIGNED(n) __attribute__((aligned (n)))
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#endif
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/* Used with IP headers only */
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#define LWIP_CHKSUM_ALGORITHM 1
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/* Provide Thumb-2 routines for GCC to improve performance */
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#if defined(TOOLCHAIN_GCC) && defined(__thumb2__)
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#define MEMCPY(dst,src,len) thumb2_memcpy(dst,src,len)
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#define LWIP_CHKSUM thumb2_checksum
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/* Set algorithm to 0 so that unused lwip_standard_chksum function
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doesn't generate compiler warning */
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#define LWIP_CHKSUM_ALGORITHM 0
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void* thumb2_memcpy(void* pDest, const void* pSource, size_t length);
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u16_t thumb2_checksum(void* pData, int length);
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#else
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/* Used with IP headers only */
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#define LWIP_CHKSUM_ALGORITHM 1
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#endif
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#ifdef LWIP_DEBUG
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@ -0,0 +1,126 @@
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/* Copyright (C) 2013 - Adam Green (https://github.com/adamgreen)
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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#if defined(TOOLCHAIN_GCC) && defined(__thumb2__)
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/* This is a hand written Thumb-2 assembly language version of the
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algorithm 3 version of lwip_standard_chksum in lwIP's inet_chksum.c. It
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performs the checksumming 32-bits at a time and even unrolls the loop to
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perform two of these 32-bit adds per loop iteration.
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Returns:
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16-bit 1's complement summation (not inversed).
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NOTE: This function does return a uint16_t from the assembly language code
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but is marked as void so that GCC doesn't issue warning because it
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doesn't know about this low level return.
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*/
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__attribute__((naked)) void /*uint16_t*/ thumb2_checksum(const void* pData, int length)
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{
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__asm (
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".syntax unified\n"
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".thumb\n"
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// Push non-volatile registers we use on stack. Push link register too to
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// keep stack 8-byte aligned and allow single pop to restore and return.
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" push {r4, lr}\n"
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// Initialize sum, r2, to 0.
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" movs r2, #0\n"
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// Remember whether pData was at odd address in r3. This is used later to
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// know if it needs to swap the result since the summation will be done at
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// an offset of 1, rather than 0.
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" ands r3, r0, #1\n"
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// Need to 2-byte align? If not skip ahead.
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" beq 1$\n"
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// We can return if there are no bytes to sum.
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" cbz r1, 9$\n"
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// 2-byte align.
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// Place the first data byte in odd summation location since it needs to be
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// swapped later. It's ok to overwrite r2 here as it only had a value of 0
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// up until now. Advance r0 pointer and decrement r1 length as we go.
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" ldrb r2, [r0], #1\n"
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" lsls r2, r2, #8\n"
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" subs r1, r1, #1\n"
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// Need to 4-byte align? If not skip ahead.
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"1$:\n"
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" ands r4, r0, #3\n"
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" beq 2$\n"
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// Have more than 1 byte left to align? If not skip ahead to take care of
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// trailing byte.
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" cmp r1, #2\n"
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" blt 7$\n"
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// 4-byte align.
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" ldrh r4, [r0], #2\n"
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" adds r2, r2, r4\n"
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" subs r1, r1, #2\n"
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// Main summing loop which sums up data 2 words at a time.
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// Make sure that we have more than 7 bytes left to sum.
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"2$:\n"
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" cmp r1, #8\n"
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" blt 3$\n"
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// Sum next two words. Applying previous upper 16-bit carry to
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// lower 16-bits.
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" ldr r4, [r0], #4\n"
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" adds r2, r4\n"
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" adc r2, r2, #0\n"
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" ldr r4, [r0], #4\n"
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" adds r2, r4\n"
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" adc r2, r2, #0\n"
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" subs r1, r1, #8\n"
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" b 2$\n"
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// Sum up any remaining half-words.
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"3$:\n"
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// Make sure that we have more than 1 byte left to sum.
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" cmp r1, #2\n"
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" blt 7$\n"
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// Sum up next half word, continue to apply carry.
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" ldrh r4, [r0], #2\n"
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" adds r2, r4\n"
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" adc r2, r2, #0\n"
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" subs r1, r1, #2\n"
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" b 3$\n"
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// Handle trailing byte, if it exists
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"7$:\n"
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" cbz r1, 8$\n"
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" ldrb r4, [r0]\n"
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" adds r2, r4\n"
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" adc r2, r2, #0\n"
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// Fold 32-bit checksum into 16-bit checksum.
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"8$:\n"
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" ubfx r4, r2, #16, #16\n"
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" ubfx r2, r2, #0, #16\n"
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" adds r2, r4\n"
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" ubfx r4, r2, #16, #16\n"
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" ubfx r2, r2, #0, #16\n"
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" adds r2, r4\n"
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// Swap bytes if started at odd address
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" cbz r3, 9$\n"
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" rev16 r2, r2\n"
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// Return final sum.
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"9$: mov r0, r2\n"
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" pop {r4, pc}\n"
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);
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}
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#endif
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@ -0,0 +1,59 @@
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/* Copyright (C) 2013 - Adam Green (https://github.com/adamgreen)
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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#if defined(TOOLCHAIN_GCC) && defined(__thumb2__)
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#include <stdio.h>
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/* This is a hand written Thumb-2 assembly language version of the
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standard C memcpy() function that can be used by the lwIP networking
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stack to improve its performance. It copies 4 bytes at a time and
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unrolls the loop to perform 4 of these copies per loop iteration.
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*/
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__attribute__((naked)) void thumb2_memcpy(void* pDest, const void* pSource, size_t length)
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{
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__asm (
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".syntax unified\n"
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".thumb\n"
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// Copy 16 bytes at a time first.
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" lsrs r3, r2, #4\n"
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" beq.n 2$\n"
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"1$: ldr r12, [r1], #4\n"
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" str r12, [r0], #4\n"
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" ldr r12, [r1], #4\n"
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" str r12, [r0], #4\n"
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" ldr r12, [r1], #4\n"
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" str r12, [r0], #4\n"
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" ldr r12, [r1], #4\n"
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" str r12, [r0], #4\n"
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" subs r3, #1\n"
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" bne 1$\n"
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// Copy byte by byte for what is left.
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"2$:\n"
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" ands r3, r2, #0xf\n"
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" beq.n 4$\n"
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"3$: ldrb r12, [r1], #1\n"
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" strb r12, [r0], #1\n"
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" subs r3, #1\n"
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" bne 3$\n"
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// Return to caller.
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"4$: bx lr\n"
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);
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}
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#endif
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