How to determine that 2.0 == (float) 2 in a front-end.

[Toon Moene]

Robert Dewar wrote:

> I wrote:
 
>> Obviously, because X**Y, with Y real, is implemented by computing
>> EXP(Y*LOG(X)) one doesn't want to change 2.0 to 2 lightly (i.e.,
>> without the assurance of -funsafe-math_optimizations).
> 
> Gosh I hope not! computing x**y that way is horribly inaccurate even with
> perfect log and exp functions.

No, that was a brain-fart - thanks for alerting me to it.  g77 generates
a call to the `pow' function in the C library, thereby shifting the
blame.

I initially thought I had seen this in libf2c, but
gcc/libf2c/libF77/Version.c doesn't mention a switch from exp(y*log(x))
to pow(x,y) in its "ChangeLog", so it must have been there from 1980
onwards.

Sorry, I don't know where I got the idea from ...

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