Simon Peyton-Jones wrote:
| > GHC does some constant folding, but little by way of strength | reduction, or using shifts instead of multiplication. It's pretty easy | to add more: it's all done in a single module. Look at primOpRules in | the module PrelRules. | > | > Patches welcome! But please also supply test-suite tests that check | the correctness of the rules. | > | | So... you mean it's source-level transformation rules? (Rather than | wired into the compiler itself somewhere.)
No, constant folding is part of the compiler, I'm afraid, in the module PrelRules.
Simon
_Constant_ folding is, but in GHC.Base there are rules like (unboxed) multiplying by zero or one, or adding or subtracting zero, from an unknown other (non-constant) value. I think shifts might be doable via RULES... if you were willing to make one rule for each denominator 2, 4, 8 and so on, which rather depends on max. Int... (and that's not Integers either, I guess) Isaac