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f4a3549250
This patch adds two versions of memcpy optimized for architectures where unaligned accesses are either illegal or extremely slow. It is currently enabled for RISCV 64 and RISCV 32 but it could be used for ARM 32 architectures as well. Here is the before / after output of `libc.benchmarks.memory_functions.opt_host --benchmark_filter=BM_Memcpy` on a quad core Linux starfive RISCV 64 board running at 1.5GHz. Before: ``` Run on (4 X 1500 MHz CPU s) CPU Caches: L1 Instruction 32 KiB (x4) L1 Data 32 KiB (x4) L2 Unified 2048 KiB (x1) ------------------------------------------------------------------------ Benchmark Time CPU Iterations UserCounters... ------------------------------------------------------------------------ BM_Memcpy/0/0 474 ns 474 ns 1483776 bytes_per_cycle=0.243492/s bytes_per_second=348.318M/s items_per_second=2.11097M/s __llvm_libc::memcpy,memcpy Google A BM_Memcpy/1/0 210 ns 209 ns 3649536 bytes_per_cycle=0.233819/s bytes_per_second=334.481M/s items_per_second=4.77519M/s __llvm_libc::memcpy,memcpy Google B BM_Memcpy/2/0 1814 ns 1814 ns 396288 bytes_per_cycle=0.247899/s bytes_per_second=354.622M/s items_per_second=551.402k/s __llvm_libc::memcpy,memcpy Google D BM_Memcpy/3/0 89.3 ns 89.2 ns 7459840 bytes_per_cycle=0.217415/s bytes_per_second=311.014M/s items_per_second=11.2071M/s __llvm_libc::memcpy,memcpy Google L BM_Memcpy/4/0 134 ns 134 ns 3815424 bytes_per_cycle=0.226584/s bytes_per_second=324.131M/s items_per_second=7.44567M/s __llvm_libc::memcpy,memcpy Google M BM_Memcpy/5/0 52.8 ns 52.6 ns 11001856 bytes_per_cycle=0.194893/s bytes_per_second=278.797M/s items_per_second=19.0284M/s __llvm_libc::memcpy,memcpy Google Q BM_Memcpy/6/0 180 ns 180 ns 4101120 bytes_per_cycle=0.231884/s bytes_per_second=331.713M/s items_per_second=5.55957M/s __llvm_libc::memcpy,memcpy Google S BM_Memcpy/7/0 195 ns 195 ns 3906560 bytes_per_cycle=0.232951/s bytes_per_second=333.239M/s items_per_second=5.1217M/s __llvm_libc::memcpy,memcpy Google U BM_Memcpy/8/0 152 ns 152 ns 4789248 bytes_per_cycle=0.227507/s bytes_per_second=325.452M/s items_per_second=6.58187M/s __llvm_libc::memcpy,memcpy Google W BM_Memcpy/9/0 6036 ns 6033 ns 118784 bytes_per_cycle=0.249158/s bytes_per_second=356.423M/s items_per_second=165.75k/s __llvm_libc::memcpy,uniform 384 to 4096 ``` After: ``` BM_Memcpy/0/0 126 ns 126 ns 5770240 bytes_per_cycle=1.04707/s bytes_per_second=1.46273G/s items_per_second=7.9385M/s __llvm_libc::memcpy,memcpy Google A BM_Memcpy/1/0 75.1 ns 75.0 ns 10204160 bytes_per_cycle=0.691143/s bytes_per_second=988.687M/s items_per_second=13.3289M/s __llvm_libc::memcpy,memcpy Google B BM_Memcpy/2/0 333 ns 333 ns 2174976 bytes_per_cycle=1.39297/s bytes_per_second=1.94596G/s items_per_second=3.00002M/s __llvm_libc::memcpy,memcpy Google D BM_Memcpy/3/0 49.6 ns 49.5 ns 16092160 bytes_per_cycle=0.710161/s bytes_per_second=1015.89M/s items_per_second=20.1844M/s __llvm_libc::memcpy,memcpy Google L BM_Memcpy/4/0 57.7 ns 57.7 ns 11213824 bytes_per_cycle=0.561557/s bytes_per_second=803.314M/s items_per_second=17.3228M/s __llvm_libc::memcpy,memcpy Google M BM_Memcpy/5/0 48.0 ns 47.9 ns 16437248 bytes_per_cycle=0.346708/s bytes_per_second=495.97M/s items_per_second=20.8571M/s __llvm_libc::memcpy,memcpy Google Q BM_Memcpy/6/0 67.5 ns 67.5 ns 10616832 bytes_per_cycle=0.614173/s bytes_per_second=878.582M/s items_per_second=14.8142M/s __llvm_libc::memcpy,memcpy Google S BM_Memcpy/7/0 84.7 ns 84.6 ns 10480640 bytes_per_cycle=0.819077/s bytes_per_second=1.14424G/s items_per_second=11.8174M/s __llvm_libc::memcpy,memcpy Google U BM_Memcpy/8/0 61.7 ns 61.6 ns 11191296 bytes_per_cycle=0.550078/s bytes_per_second=786.893M/s items_per_second=16.2279M/s __llvm_libc::memcpy,memcpy Google W BM_Memcpy/9/0 981 ns 981 ns 703488 bytes_per_cycle=1.52333/s bytes_per_second=2.12807G/s items_per_second=1019.81k/s __llvm_libc::memcpy,uniform 384 to 4096 ``` It is not as good as glibc for now so there's room for improvement. I suspect a path pumping 16 bytes at once given the doubled numbers for large copies. ``` BM_Memcpy/0/1 146 ns 82.5 ns 8576000 bytes_per_cycle=1.35236/s bytes_per_second=1.88922G/s items_per_second=12.1169M/s glibc memcpy,memcpy Google A BM_Memcpy/1/1 112 ns 63.7 ns 10634240 bytes_per_cycle=0.628018/s bytes_per_second=898.387M/s items_per_second=15.702M/s glibc memcpy,memcpy Google B BM_Memcpy/2/1 315 ns 180 ns 4079616 bytes_per_cycle=2.65229/s bytes_per_second=3.7052G/s items_per_second=5.54764M/s glibc memcpy,memcpy Google D BM_Memcpy/3/1 85.3 ns 43.1 ns 15854592 bytes_per_cycle=0.774164/s bytes_per_second=1107.45M/s items_per_second=23.2249M/s glibc memcpy,memcpy Google L BM_Memcpy/4/1 105 ns 54.3 ns 13427712 bytes_per_cycle=0.7793/s bytes_per_second=1114.8M/s items_per_second=18.4109M/s glibc memcpy,memcpy Google M BM_Memcpy/5/1 77.1 ns 43.2 ns 16476160 bytes_per_cycle=0.279808/s bytes_per_second=400.269M/s items_per_second=23.1428M/s glibc memcpy,memcpy Google Q BM_Memcpy/6/1 112 ns 62.7 ns 11236352 bytes_per_cycle=0.676078/s bytes_per_second=967.137M/s items_per_second=15.9387M/s glibc memcpy,memcpy Google S BM_Memcpy/7/1 131 ns 65.5 ns 11751424 bytes_per_cycle=0.965616/s bytes_per_second=1.34895G/s items_per_second=15.2762M/s glibc memcpy,memcpy Google U BM_Memcpy/8/1 104 ns 55.0 ns 12314624 bytes_per_cycle=0.583336/s bytes_per_second=834.468M/s items_per_second=18.1937M/s glibc memcpy,memcpy Google W BM_Memcpy/9/1 932 ns 466 ns 1480704 bytes_per_cycle=3.17342/s bytes_per_second=4.43321G/s items_per_second=2.14679M/s glibc memcpy,uniform 384 to 4096 ``` Reviewed By: sivachandra Differential Revision: https://reviews.llvm.org/D150202 |
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| .. | ||
| AOR_v20.02 | ||
| benchmarks | ||
| cmake/modules | ||
| config | ||
| docs | ||
| examples | ||
| fuzzing | ||
| include | ||
| lib | ||
| spec | ||
| src | ||
| startup | ||
| test | ||
| utils | ||
| .clang-tidy | ||
| .gitignore | ||
| CMakeLists.txt | ||
| common_libc_tuners.cmake | ||
| LICENSE.TXT | ||
| README.txt | ||
LLVM libc ========= This directory and its subdirectories contain source code for llvm-libc, a retargetable implementation of the C standard library. LLVM is open source software. You may freely distribute it under the terms of the license agreement found in LICENSE.txt.