Mark Dickinson <dicki...@gmail.com> added the comment:
> Hi Marc, the changes to the pythoncore.vcproj Visual-Studio file define > the
> HAVE_VC_FUNC_FOR_X87 symbol.
Okay, makes sense. I was distracted by the spurious reordering of in the diff
for pythoncore.vcproj.
Just to be clear, the intent of the patch is that the FPU state is *always*
switched on Windows prior to calling the dtoa.c functions; is that right?
Things to think about:
- can we avoid *writing* to the x87 / SSE control word if no change is
necessary (as is currently done with the gcc code)? We want to avoid
unnecessary FPU pipeline flushes.
- we need to make sure that the patch works on 64-bit. There's a bit of text
at:
http://msdn.microsoft.com/en-us/library/c9676k6h.aspx
that suggests that in x64 mode, setting the precision is an error.
- what happens if the x87 and SSE2 control words have different precisions?
Does the patch restore both those precisions correctly?
- in the patch, isn't new387controlword unused?
I'm not sure that this part of the patch can go into the maintenance branches
(2.7, 3.2); if this is a new feature (and I think it is, but I'm willing to be
persuaded otherwise), it can only target 3.3.
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<http://bugs.python.org/issue13889>
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