Stream: git-wasmtime

Topic: wasmtime / PR #2043 Aarch64: handle csel with icmp/fcmp s...

Wasmtime GitHub notifications bot (Jul 18 2020 at 04:16):

cfallin opened PR #2043 from csel-opt to main:

Previously, we simply compared the input bool to 0, which forced the
value into a register (usually via a cmp and cset), zero-extended it,
etc. This patch performs the same pattern-matching that branches do to
directly perform the cmp and use its flag results with the csel.

On the bz2 benchmark, the runtime is affected as follows (measuring
with perf stat, using wasmtime with its cache enabled, and taking the
second run after the first compiles and populates the cache):

pre:

       1117.232000      task-clock (msec)         #    1.000 CPUs utilized
               133      context-switches          #    0.119 K/sec
                 1      cpu-migrations            #    0.001 K/sec
             5,041      page-faults               #    0.005 M/sec
     3,511,615,100      cycles                    #    3.143 GHz
     4,272,427,772      instructions              #    1.22  insn per cycle
   <not supported>      branches
        27,980,906      branch-misses

       1.117299838 seconds time elapsed

post:

       1003.738075      task-clock (msec)         #    1.000 CPUs utilized
               121      context-switches          #    0.121 K/sec
                 0      cpu-migrations            #    0.000 K/sec
             5,052      page-faults               #    0.005 M/sec
     3,224,875,393      cycles                    #    3.213 GHz
     4,000,838,686      instructions              #    1.24  insn per cycle
   <not supported>      branches
        27,928,232      branch-misses

       1.003440004 seconds time elapsed

In other words, with this change, on bz2, we see a 6.3% reduction in
executed instructions.

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Wasmtime GitHub notifications bot (Jul 18 2020 at 04:16):

cfallin requested bnjbvr for a review on PR #2043.

Wasmtime GitHub notifications bot (Jul 18 2020 at 04:16):

cfallin requested bnjbvr and julian-seward1 for a review on PR #2043.

Wasmtime GitHub notifications bot (Jul 18 2020 at 06:49):

julian-seward1 submitted PR Review.

Wasmtime GitHub notifications bot (Jul 19 2020 at 02:33):

cfallin merged PR #2043.

Last updated: Dec 23 2024 at 13:07 UTC