Compiler optimizations questions for ghc 6.10...

[Tyson Whitehead]

On February 19, 2009 18:20:33 Krasimir Angelov wrote:
> Oh. I looked at the primops.txt.pp for something suspicious but I
> didn't checked the actual implementation of quot. I thought that quot
> calls quotInt# directly. When I use quotInt in the code I can get the
> real idiv assembly instruction. Still the code generated by GHC is
> strange it doesn't throw any exception actually. It just evaluates the
> same expression but with the constant maxBound.
>
> On Thu, Feb 19, 2009 at 11:19 PM, Max Bolingbroke
> >    a `quot` b
> >
> >     | b == 0                     = divZeroError
> >     | a == minBound && b == (-1) = overflowError
> >     | otherwise                  =  a `quotInt` b

I checked the quot one like you said.  Kind of strange all right.

It looks like it is performing the a == minBound check (where a = maxBound-x) 
despite the b == (-1) check (where b = 10) being optimized away.

Cheers!  -Tyson
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