This BIG PATCH contains most of the work for the New Coercion Representation

[ghc-hetmet.git] / compiler / coreSyn / CorePrep.lhs

diff --git a/compiler/coreSyn/CorePrep.lhs b/compiler/coreSyn/CorePrep.lhs
index 42379b4..0405716 100644 (file)
--- a/compiler/coreSyn/CorePrep.lhs
+++ b/compiler/coreSyn/CorePrep.lhs
@@ -37,6 +37,7 @@ import OrdList
 import ErrUtils
 import DynFlags
 import Util
+import Pair
 import Outputable
 import MonadUtils
 import FastString
@@ -78,9 +79,9 @@ The goal of this pass is to prepare for code generation.
     weaker guarantee of no clashes which the simplifier provides.
     And that is what the code generator needs.
 
-    We don't clone TyVars. The code gen doesn't need that, 
+    We don't clone TyVars or CoVars. The code gen doesn't need that, 
     and doing so would be tiresome because then we'd need
-    to substitute in types.
+    to substitute in types and coercions.
 
 
 7.  Give each dynamic CCall occurrence a fresh unique; this is
@@ -104,19 +105,21 @@ Invariants
 Here is the syntax of the Core produced by CorePrep:
 
     Trivial expressions 
-       triv ::= lit |  var  | triv ty  |  /\a. triv  |  triv |> co
+       triv ::= lit |  var  
+              | triv ty  |  /\a. triv 
+              | truv co  |  /\c. triv  |  triv |> co
 
     Applications
-       app ::= lit  |  var  |  app triv  |  app ty  |  app |> co
+       app ::= lit  |  var  |  app triv  |  app ty  | app co | app |> co
 
     Expressions
        body ::= app  
               | let(rec) x = rhs in body     -- Boxed only
               | case body of pat -> body
-             | /\a. body
+             | /\a. body | /\c. body 
               | body |> co
 
-    Right hand sides (only place where lambdas can occur)
+    Right hand sides (only place where value lambdas can occur)
        rhs ::= /\a.rhs  |  \x.rhs  |  body
 
 We define a synonym for each of these non-terminals.  Functions
@@ -440,9 +443,10 @@ cpeRhsE :: CorePrepEnv -> CoreExpr -> UniqSM (Floats, CpeRhs)
 -- For example
 --     f (g x)   ===>   ([v = g x], f v)
 
-cpeRhsE _env expr@(Type _) = return (emptyFloats, expr)
-cpeRhsE _env expr@(Lit _)  = return (emptyFloats, expr)
-cpeRhsE env expr@(Var {})  = cpeApp env expr
+cpeRhsE _env expr@(Type {})     = return (emptyFloats, expr)
+cpeRhsE _env expr@(Coercion {}) = return (emptyFloats, expr)
+cpeRhsE _env expr@(Lit {})      = return (emptyFloats, expr)
+cpeRhsE env expr@(Var {})       = cpeApp env expr
 
 cpeRhsE env (Var f `App` _ `App` arg)
   | f `hasKey` lazyIdKey         -- Replace (lazy a) by a
@@ -528,7 +532,7 @@ rhsToBody (Cast e co)
 rhsToBody expr@(Lam {})
   | Just no_lam_result <- tryEtaReducePrep bndrs body
   = return (emptyFloats, no_lam_result)
-  | all isTyCoVar bndrs                -- Type lambdas are ok
+  | all isTyVar bndrs          -- Type lambdas are ok
   = return (emptyFloats, expr)
   | otherwise                  -- Some value lambdas
   = do { fn <- newVar (exprType expr)
@@ -579,6 +583,10 @@ cpeApp env expr
       = do { (fun',hd,fun_ty,floats,ss) <- collect_args fun depth
            ; return (App fun' arg, hd, applyTy fun_ty arg_ty, floats, ss) }
 
+    collect_args (App fun arg@(Coercion arg_co)) depth
+      = do { (fun',hd,fun_ty,floats,ss) <- collect_args fun depth
+           ; return (App fun' arg, hd, applyCo fun_ty arg_co, floats, ss) }
+
     collect_args (App fun arg) depth
       = do { (fun',hd,fun_ty,floats,ss) <- collect_args fun (depth+1)
           ; let
@@ -608,7 +616,7 @@ cpeApp env expr
                -- partial application might be seq'd
 
     collect_args (Cast fun co) depth
-      = do { let (_ty1,ty2) = coercionKind co
+      = do { let Pair _ty1 ty2 = coercionKind co
            ; (fun', hd, _, floats, ss) <- collect_args fun depth
            ; return (Cast fun' co, hd, ty2, floats, ss) }
           
@@ -751,11 +759,12 @@ cpe_ExprIsTrivial :: CoreExpr -> Bool
 -- Version that doesn't consider an scc annotation to be trivial.
 cpe_ExprIsTrivial (Var _)                  = True
 cpe_ExprIsTrivial (Type _)                 = True
+cpe_ExprIsTrivial (Coercion _)             = True
 cpe_ExprIsTrivial (Lit _)                  = True
 cpe_ExprIsTrivial (App e arg)              = isTypeArg arg && cpe_ExprIsTrivial e
 cpe_ExprIsTrivial (Note n e)               = notSccNote n  && cpe_ExprIsTrivial e
 cpe_ExprIsTrivial (Cast e _)               = cpe_ExprIsTrivial e
-cpe_ExprIsTrivial (Lam b body) | isTyCoVar b = cpe_ExprIsTrivial body
+cpe_ExprIsTrivial (Lam b body) | isTyVar b = cpe_ExprIsTrivial body
 cpe_ExprIsTrivial _                        = False
 \end{code}
 
@@ -1070,7 +1079,7 @@ cloneBndrs env bs = mapAccumLM cloneBndr env bs
 
 cloneBndr  :: CorePrepEnv -> Var -> UniqSM (CorePrepEnv, Var)
 cloneBndr env bndr
-  | isLocalId bndr
+  | isLocalId bndr, not (isCoVar bndr)
   = do bndr' <- setVarUnique bndr <$> getUniqueM
        
        -- We are going to OccAnal soon, so drop (now-useless) rules/unfoldings
@@ -1082,7 +1091,7 @@ cloneBndr env bndr
 
   | otherwise  -- Top level things, which we don't want
                -- to clone, have become GlobalIds by now
-               -- And we don't clone tyvars
+               -- And we don't clone tyvars, or coercion variables
   = return (env, bndr)