More work on the simplifier's inlining strategies
This patch collects a small raft of related changes * Arrange that during (a) rule matching and (b) uses of exprIsConApp_maybe we "look through" unfoldings only if they are active in the phase. Doing this for (a) required a bit of extra plumbing in the rule matching code, but I think it's worth it. One wrinkle is that even if inlining is off (in the 'gentle' phase of simplification) during rule matching we want to "look through" things with inlinings. See SimplUtils.activeUnfInRule. This fixes a long-standing bug, where things that were supposed to be (say) NOINLINE, could still be poked into via exprIsConApp_maybe. * In the above cases, also check for (non-rule) loop breakers; we never look through these. This fixes a bug that could make the simplifier diverge (and did for Roman). Test = simplCore/should_compile/dfun-loop * Try harder not to choose a DFun as a loop breaker. This is just a small adjustment in the OccurAnal scoring function * In the scoring function in OccurAnal, look at the InlineRule unfolding (if there is one) not the actual RHS, beause the former is what'll be inlined. * Make the application of any function to dictionary arguments CONLIKE. Thus (f d1 d2) is CONLIKE. Encapsulated in CoreUtils.isExpandableApp Reason: see Note [Expandable overloadings] in CoreUtils * Make case expressions seem slightly smaller in CoreUnfold. This reverses an unexpected consequences of charging for alternatives. Refactorings ~~~~~~~~~~~~ * Signficantly refactor the data type for Unfolding (again). The result is much nicer. * Add type synonym BasicTypes.CompilerPhase = Int and use it Many of the files touched by this patch are simply knock-on consequences of these two refactorings.