[PATCH] D26890: SHA1: unroll loop in hashBlock.

[Rui Ueyama via llvm-commits]

ruiu created this revision.
ruiu added reviewers: mehdi_amini, joerg.
ruiu added a subscriber: llvm-commits.

This code is taken from public domain.
https://github.com/jsonn/src/blob/trunk/common/lib/libc/hash/sha1/sha1.c

I wrote a sha1 command and run it on my Xeon E5-2680 v2 2.80GHz machine.
Here is a result. The new hash function is 37% faster than before.

Performance counter stats for './llvm-sha1-old /ssd/build/bin/lld' (10 runs):

      6640.503687 task-clock (msec)         #    1.001 CPUs utilized            ( +-  0.03% )
               54 context-switches          #    0.008 K/sec                    ( +-  5.03% )
                5 cpu-migrations            #    0.001 K/sec                    ( +- 31.73% )
          183,803 page-faults               #    0.028 M/sec                    ( +-  0.00% )
   18,527,954,113 cycles                    #    2.790 GHz                      ( +-  0.03% )
    4,993,237,485 stalled-cycles-frontend   #   26.95% frontend cycles idle     ( +-  0.11% )
  <not supported> stalled-cycles-backend
   50,217,149,423 instructions              #    2.71  insns per cycle
                                            #    0.10  stalled cycles per insn  ( +-  0.00% )
    6,094,322,337 branches                  #  917.750 M/sec                    ( +-  0.00% )
       11,778,239 branch-misses             #    0.19% of all branches          ( +-  0.01% )
  
      6.634017401 seconds time elapsed                                          ( +-  0.03% )

Performance counter stats for './llvm-sha1-new /ssd/build/bin/lld' (10 runs):

      4167.062720 task-clock (msec)         #    1.001 CPUs utilized            ( +-  0.02% )
               52 context-switches          #    0.012 K/sec                    ( +- 16.45% )
                7 cpu-migrations            #    0.002 K/sec                    ( +- 32.20% )
          183,804 page-faults               #    0.044 M/sec                    ( +-  0.00% )
   11,626,611,958 cycles                    #    2.790 GHz                      ( +-  0.02% )
    4,491,897,976 stalled-cycles-frontend   #   38.63% frontend cycles idle     ( +-  0.05% )
  <not supported> stalled-cycles-backend
   24,320,180,617 instructions              #    2.09  insns per cycle
                                            #    0.18  stalled cycles per insn  ( +-  0.00% )
    1,574,674,576 branches                  #  377.886 M/sec                    ( +-  0.00% )
       11,769,693 branch-misses             #    0.75% of all branches          ( +-  0.00% )
  
      4.163251552 seconds time elapsed                                          ( +-  0.02% )


https://reviews.llvm.org/D26890

Files:
  include/llvm/Support/SHA1.h
  lib/Support/SHA1.cpp

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