[pypy-dev] PyPy Assembler SQRT Patch

[Joe]

Attached an updated patch.  It actually generates the assembly now to
use SQRTSD.  It provides about the same performance as the previous
patch.  Because of that, I feel as though the performance gain can be
attributed to the change in error checking.

It might be worth splitting out the other math functions and slimming
down the error checking.  Right now in the new_unary_math_function it
generates a math function that does 3 C library calls 2 errno calls
and the math function itself.  The patch takes this down to the
minimal number of checks necessary for math.sqrt, making only an
isfinite() call in addition to the sqrt() call best case.  Previously
it'd call "_error_reset(); c_func(); rposix.get_errno()" and then at
least 1 call to isnan() and a call to either isnan() or isinf().

Does this seem like something worth looking into for the other math
functions?  It wouldn't be as hard as getting the whole assembly
instruction working, and seems like it provides the majority of the
performance gain.

Joe

On Tue, May 3, 2011 at 12:28 PM, Armin Rigo <arigo at tunes.org> wrote:
> Hi Alex,
>
> On Tue, May 3, 2011 at 6:23 PM, Alex Gaynor <alex.gaynor at gmail.com> wrote:
>> Another thing is it would be useful to test that the SQRTSD is generated, I
>> don't know a good way to do that though.
>
> In the test, you can hack genop_math_sqrt() in-place to set a flag,
> and test that the flag is set...
>
> And another place it should also be tested is in test_pypy_c_new.py
> (pypy.module.pypyjit.test_pypy_c), i.e. you should write a test that
> checks that in a full translated pypy-c, the code corresponding to the
> Python source "math.sqrt(x)" indeed ends up being a CALL(sqrt_wrapper)
> and not a CALL(ll_math_sqrt).
>
>
> A bientôt,
>
> Armin.
> _______________________________________________
> pypy-dev at codespeak.net
> http://codespeak.net/mailman/listinfo/pypy-dev
>
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