diff options
| -rw-r--r-- | ghc/compiler/simplCore/SimplCore.lhs | 39 |
1 files changed, 27 insertions, 12 deletions
diff --git a/ghc/compiler/simplCore/SimplCore.lhs b/ghc/compiler/simplCore/SimplCore.lhs index af45946dfe..d03671e89a 100644 --- a/ghc/compiler/simplCore/SimplCore.lhs +++ b/ghc/compiler/simplCore/SimplCore.lhs @@ -24,7 +24,7 @@ import Rules ( RuleBase, emptyRuleBase, ruleBaseFVs, ruleBaseIds, import Module ( moduleEnvElts ) import CoreUnfold import PprCore ( pprCoreBindings, pprIdCoreRule, pprCoreExpr ) -import OccurAnal ( occurAnalyseBinds ) +import OccurAnal ( occurAnalyseBinds, occurAnalyseGlobalExpr ) import CoreUtils ( etaReduce, coreBindsSize ) import Simplify ( simplTopBinds, simplExpr ) import SimplUtils ( simplBinders ) @@ -99,6 +99,8 @@ simplifyExpr :: DynFlags -- includes spec of what core-to-core passes to do -> HomeSymbolTable -> CoreExpr -> IO CoreExpr +-- simplifyExpr is called by the driver to simplify an +-- expression typed in at the interactive prompt simplifyExpr dflags pcs hst expr = do { ; showPass dflags "Simplify" @@ -106,9 +108,9 @@ simplifyExpr dflags pcs hst expr ; us <- mkSplitUniqSupply 's' ; let (expr', _counts) = initSmpl dflags sw_chkr us emptyVarSet black_list_all - (simplExpr expr) + (simplExprGently expr) - ; dumpIfSet_dyn dflags Opt_D_dump_simpl "Simplfied expression" + ; dumpIfSet_dyn dflags Opt_D_dump_simpl "Simplified expression" (pprCoreExpr expr') ; return expr' @@ -284,20 +286,33 @@ simplRule rule@(id, BuiltinRule _) = returnSmpl rule simplRule rule@(id, Rule name bndrs args rhs) = simplBinders bndrs $ \ bndrs' -> - mapSmpl simpl_arg args `thenSmpl` \ args' -> - simplExpr rhs `thenSmpl` \ rhs' -> + mapSmpl simplExprGently args `thenSmpl` \ args' -> + simplExprGently rhs `thenSmpl` \ rhs' -> returnSmpl (id, Rule name bndrs' args' rhs') -simpl_arg e --- I've seen rules in which a LHS like +-- It's important that simplExprGently does eta reduction. +-- For example, in a rule like: -- augment g (build h) --- turns into +-- we do not want to get -- augment (\a. g a) (build h) --- So it's a help to eta-reduce the args as we simplify them. --- Otherwise we don't match when given an argument like +-- otherwise we don't match when given an argument like -- (\a. h a a) - = simplExpr e `thenSmpl` \ e' -> - returnSmpl (etaReduce e') +-- +-- The simplifier does indeed do eta reduction (it's in +-- Simplify.completeLam) but only if -O is on. +\end{code} + +\begin{code} +simplExprGently :: CoreExpr -> SimplM CoreExpr +-- Simplifies an expression +-- does occurrence analysis, then simplification +-- and repeats (twice currently) because one pass +-- alone leaves tons of crud. +-- Used (a) for user expressions typed in at the interactive prompt +-- (b) the LHS and RHS of a RULE +simplExprGently expr + = simplExpr (occurAnalyseGlobalExpr expr) `thenSmpl` \ expr1 -> + simplExpr (occurAnalyseGlobalExpr expr1) \end{code} |