[MLton] Re: MLton codegen combines divison on arm

[Wesley W. Terpstra]

On Mon, Oct 25, 2010 at 10:52 PM, Wesley W. Terpstra <wesley at terpstra.ca> wrote:
> There must be a toggle
> somewhere in MLton that is letting it think that it is safe to
> optimize away the division, but I can't for the life of me find it.

I think I've found the problem! It will take two days before I know
for sure, though.

The problem isn't a flag, but that my mlton compiler was built before
I wrote the fix. It decides that 1.0/10.0 is safe to optimize if when
it does the calculation with TO_NEGINF and TO_POSINF the result comes
out the same. Since fesetround was broken, the compiler always got the
same result (even though it shouldn't). Thus, it decided it was safe
to optimize 1.0/10.0 away. Presumably a complete two-stage rebuild of
the compiler will incorporate the fix into the compiler and then when
it compiles the regression, it will pass.