Mail Archives: djgpp/1996/12/30/19:55:45
>Hi!
Hi :)
>I have some troubles using the optimizing features in the
>compiler
>1) When the compiler optimizes a tight inner loop, that
>uses only integer math
>it inserts a bunch of floating point instructions (fxch)
>that doesn't seem to do
Check to make sure _everything_ is integer math, and that you aren't
accidentally typecasting to a float/double (ie using trig functions, etc)
>anything at all (I can remove them and my code works fine
>without). As these
>instructions are inside the tight loop they eat up about
>50% of the time spent here..
If it's really unnecessary floating math, I'm surprised it doesn't eat up
more...
>2) When using the trigonomic functions cos/sin in 3D
>graphics it seems that whenever
>I use the -O# compiler option the functions are treated
>differently than without
>the -O# option. Result is that the 3D space is skew'ed.
>Am I assuming something
>about the trigonomic function (ie. angles can be outside
>[0 : 2*PI]) that does not
>hold when optimizing?
I believe the 387 (and 487 and 587) require trig functions to be within
2pi. However, I can't test this for sure, since I'm FPUless.
>Kind regards, Henning Semler
Good luck,
...Chambers
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