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Comment by twtw | Hacker News Reader

Has anyone reproduced these results?

FWIW, I can't.

  $ cd wordsandbuttons/exp/python_to_llvm/exp_c
  $ make
  $ /usr/bin/time -f "%U\n" ./exp_volatile_a_b
  0.13

  $ cd wordsandbuttons/exp/python_to_llvm/exp_embed_on_call
  $ make
  $ /usr/bin/time -f "%U\n" ./benchmark
  0.16

Intel(R) Core(TM) i7-7800X CPU @ 3.50GHz, gcc (Ubuntu 7.3.0-27ubuntu1~18.04), clang version 6.0.0-1ubuntu2, LLVM version 6.0.0

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Some more interesting points:

- Switching to -O3 for gcc (instead of author's default -O2), the C version (exp_volatile_a_b) gets ~30% faster, bringing it down to ~50% of the python-generated llvm - it appears to still be doing the full computation at runtime.

- Switching to -O3 for llc doesn't make any difference for the python-generated llvm version.

- With gcc 4.8 -O2 (instead of 7.3 -O2), I get ~0.06s - it looks like gcc 4.8 decides to inline everything, and gcc 7.3 doesn't.

It makes sense: gcc's -O3 is closer to LLVM/clang's -O2 in terms of big picture optimizations they enable such as vectorization and loop unrolling.

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