#13160: Simplify CoreFV.FVAnn -------------------------------------+------------------------------------- Reporter: simonpj | Owner: bgamari Type: task | Status: new Priority: high | Milestone: 8.2.1 Component: Compiler | Version: 8.0.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Phab:D3170 Wiki Page: | -------------------------------------+------------------------------------- Changes (by bgamari): * owner: goldfire => bgamari * differential: => Phab:D3170 Comment: I tried to knock this one off while waiting for a build a few days ago, but it's not clear that the patch is quite correct and certainly lacks documentation. I'll need to come back to this. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13160#comment:2 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

#13160: Simplify CoreFV.FVAnn -------------------------------------+------------------------------------- Reporter: simonpj | Owner: bgamari Type: task | Status: new Priority: high | Milestone: 8.4.1 Component: Compiler | Version: 8.0.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Phab:D3170 Wiki Page: | -------------------------------------+------------------------------------- Description changed by mpickering: Old description:

When introducing type-in-type, Richard elaborated the free varaible finder so that it finds three things at once (in `CoreFV`): {{{ data FVAnn = FVAnn { fva_fvs :: DVarSet -- free in expression , fva_ty_fvs :: DVarSet -- free only in expression's type , fva_ty :: Type -- expression's type } }}} I think `fva_ty` is needed only to support `fva_ty_fvs`. And `fva_ty_fvs` seems to be used only to support the calls to `freeVarsOfType` in `FloatIn`. And those calls in turn are only to suppor `used_in_ty` in `FloatIn.sepBindsByDropPoint`.

In conversation yesterday, Richard and I agreed that all this is unnecessary. Coercion bindings simply do not float inwards, so we do not need to take these precautions. (We should add a Note to explain why they don't float, and what problem might arise if they did.)

To confirm this I set `used_in_ty` to `False` and compiled from scratch; everything is fine.

So I propose that we

* get rid of the `ty_fvs` argument to `sepBindsByDropPoint` * simplfy `FVAnn` to just gather free variables (ie one field only)

Result: it's all simpler.

Richard will do this when he gets a moment. But I really hope for 8.2

New description: When introducing type-in-type, Richard elaborated the free variable finder so that it finds three things at once (in `CoreFV`): {{{ data FVAnn = FVAnn { fva_fvs :: DVarSet -- free in expression , fva_ty_fvs :: DVarSet -- free only in expression's type , fva_ty :: Type -- expression's type } }}} I think `fva_ty` is needed only to support `fva_ty_fvs`. And `fva_ty_fvs` seems to be used only to support the calls to `freeVarsOfType` in `FloatIn`. And those calls in turn are only to suppor `used_in_ty` in `FloatIn.sepBindsByDropPoint`. In conversation yesterday, Richard and I agreed that all this is unnecessary. Coercion bindings simply do not float inwards, so we do not need to take these precautions. (We should add a Note to explain why they don't float, and what problem might arise if they did.) To confirm this I set `used_in_ty` to `False` and compiled from scratch; everything is fine. So I propose that we * get rid of the `ty_fvs` argument to `sepBindsByDropPoint` * simplfy `FVAnn` to just gather free variables (ie one field only) Result: it's all simpler. Richard will do this when he gets a moment. But I really hope for 8.2 -- -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13160#comment:4 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

#13160: Simplify CoreFV.FVAnn -------------------------------------+------------------------------------- Reporter: simonpj | Owner: bgamari Type: task | Status: closed Priority: high | Milestone: 8.4.1 Component: Compiler | Version: 8.0.1 Resolution: fixed | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Phab:D3170 Wiki Page: | -------------------------------------+------------------------------------- Changes (by simonpj): * status: new => closed * resolution: => fixed -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13160#comment:6 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler