-- http://hackage.haskell.org/trac/ghc/wiki/Commentary/CodingStyle#Warnings
-- for details
+-- | Functions for collecting together and applying rewrite rules to a module.
+-- The 'CoreRule' datatype itself is declared elsewhere.
module Rules (
- RuleBase, emptyRuleBase, mkRuleBase, extendRuleBaseList,
- unionRuleBase, pprRuleBase, ruleCheckProgram,
+ -- * RuleBase
+ RuleBase,
+
+ -- ** Constructing
+ emptyRuleBase, mkRuleBase, extendRuleBaseList,
+ unionRuleBase, pprRuleBase,
+
+ -- ** Checking rule applications
+ ruleCheckProgram,
+ -- ** Manipulating 'SpecInfo' rules
mkSpecInfo, extendSpecInfo, addSpecInfo,
- rulesOfBinds, addIdSpecialisations,
+ addIdSpecialisations,
- matchN,
-
+ -- * Misc. CoreRule helpers
+ rulesOfBinds,
+
lookupRule, mkLocalRule, roughTopNames
) where
\begin{code}
mkLocalRule :: RuleName -> Activation
-> Name -> [CoreBndr] -> [CoreExpr] -> CoreExpr -> CoreRule
--- Used to make CoreRule for an Id defined in this module
+-- ^ Used to make 'CoreRule' for an 'Id' defined in the module being
+-- compiled. See also 'CoreSyn.CoreRule'
mkLocalRule name act fn bndrs args rhs
= Rule { ru_name = name, ru_fn = fn, ru_act = act,
ru_bndrs = bndrs, ru_args = args,
--------------
roughTopNames :: [CoreExpr] -> [Maybe Name]
+-- ^ Find the \"top\" free names of several expressions.
+-- Such names are either:
+--
+-- 1. The function finally being applied to in an application chain
+-- (if that name is a GlobalId: see "Var#globalvslocal"), or
+--
+-- 2. The 'TyCon' if the expression is a 'Type'
+--
+-- This is used for the fast-match-check for rules;
+-- if the top names don't match, the rest can't
roughTopNames args = map roughTopName args
roughTopName :: CoreExpr -> Maybe Name
--- Find the "top" free name of an expression
--- a) the function in an App chain (if a GlobalId)
--- b) the TyCon in a type
--- This is used for the fast-match-check for rules;
--- if the top names don't match, the rest can't
roughTopName (Type ty) = case tcSplitTyConApp_maybe ty of
Just (tc,_) -> Just (getName tc)
Nothing -> Nothing
roughTopName other = Nothing
ruleCantMatch :: [Maybe Name] -> [Maybe Name] -> Bool
--- (ruleCantMatch tpl actual) returns True only if 'actual'
--- definitely can't match 'tpl' by instantiating 'tpl'.
+-- ^ @ruleCantMatch tpl actual@ returns True only if @actual@
+-- definitely can't match @tpl@ by instantiating @tpl@.
-- It's only a one-way match; unlike instance matching we
--- don't consider unification
+-- don't consider unification.
--
-- Notice that [_$_]
--- ruleCantMatch [Nothing] [Just n2] = False
+-- @ruleCantMatch [Nothing] [Just n2] = False@
-- Reason: a template variable can be instantiated by a constant
-- Also:
--- ruleCantMatch [Just n1] [Nothing] = False
--- Reason: a local variable 'v' in the actuals might [_$_]
+-- @ruleCantMatch [Just n1] [Nothing] = False@
+-- Reason: a local variable @v@ in the actuals might [_$_]
ruleCantMatch (Just n1 : ts) (Just n2 : as) = n1 /= n2 || ruleCantMatch ts as
ruleCantMatch (t : ts) (a : as) = ruleCantMatch ts as
%************************************************************************
\begin{code}
+-- | Make a 'SpecInfo' containing a number of 'CoreRule's, suitable
+-- for putting into an 'IdInfo'
mkSpecInfo :: [CoreRule] -> SpecInfo
mkSpecInfo rules = SpecInfo rules (rulesFreeVars rules)
= setIdSpecialisation id $
extendSpecInfo (idSpecialisation id) rules
+-- | Gather all the rules for locally bound identifiers from the supplied bindings
rulesOfBinds :: [CoreBind] -> [CoreRule]
rulesOfBinds binds = concatMap (concatMap idCoreRules . bindersOf) binds
\end{code}
%************************************************************************
\begin{code}
+-- | Gathers a collection of 'CoreRule's. Maps (the name of) an 'Id' to its rules
type RuleBase = NameEnv [CoreRule]
- -- Maps (the name of) an Id to its rules
-- The rules are are unordered;
-- we sort out any overlaps on lookup
to lookupRule are the result of a lazy substitution
\begin{code}
-lookupRule :: (Activation -> Bool) -> InScopeSet
- -> RuleBase -- Imported rules
- -> Id -> [CoreExpr] -> Maybe (CoreRule, CoreExpr)
+-- | The main rule matching function. Attempts to apply all the active
+-- rules in a given 'RuleBase' to this instance of an application
+-- in a given context, returning the rule applied and the resulting
+-- expression if successful.
+lookupRule :: (Activation -> Bool) -- ^ Activation test
+ -> InScopeSet -- ^ Variables that are in scope at this point
+ -> RuleBase -- ^ Imported rules
+ -> Id -- ^ Function 'Id' to lookup a rule by
+ -> [CoreExpr] -- ^ Arguments to function
+ -> Maybe (CoreRule, CoreExpr)
-- See Note [Extra argsin rule matching]
lookupRule is_active in_scope rule_base fn args
= matchRules is_active in_scope fn args (getRules rule_base fn)
\end{code}
\begin{code}
-matchN :: InScopeSet
- -> [Var] -- Template tyvars
- -> [CoreExpr] -- Template
- -> [CoreExpr] -- Target; can have more elts than template
- -> Maybe ([CoreBind], -- Bindings to wrap around the entire result
- [CoreExpr]) -- What is substituted for each template var
+-- For a given match template and context, find bindings to wrap around
+-- the entire result and what should be substituted for each template variable.
+-- Fail if there are two few actual arguments from the target to match the template
+matchN :: InScopeSet -- ^ In-scope variables
+ -> [Var] -- ^ Match template type variables
+ -> [CoreExpr] -- ^ Match template
+ -> [CoreExpr] -- ^ Target; can have more elements than the template
+ -> Maybe ([CoreBind],
+ [CoreExpr])
matchN in_scope tmpl_vars tmpl_es target_es
= do { (tv_subst, id_subst, binds)
Data.Maybe.Nothing -> lvl_smf;
Data.Maybe.Just n_acT [Just S(L)] ->
case n_acT of wild1_ams [Just A] { GHC.Base.I# y_amr [Just L] ->
- $wfoo_smW (GHC.Prim.-# ds_Xmb y_amr) wild_Xf
+ \$wfoo_smW (GHC.Prim.-# ds_Xmb y_amr) wild_Xf
}};
and correctly generates the rule
RULES: "SC:$wfoo1" [0] __forall {y_amr [Just L] :: GHC.Prim.Int#
sc_snn :: GHC.Prim.Int#}
- $wfoo_smW sc_snn (Data.Maybe.Just @ GHC.Base.Int (GHC.Base.I# y_amr))
- = $s$wfoo_sno y_amr sc_snn ;]
+ \$wfoo_smW sc_snn (Data.Maybe.Just @ GHC.Base.Int (GHC.Base.I# y_amr))
+ = \$s\$wfoo_sno y_amr sc_snn ;]
BUT we must ensure that this rule matches in the original function!
-Note that the call to $wfoo is
- $wfoo_smW (GHC.Prim.-# ds_Xmb y_amr) wild_Xf
+Note that the call to \$wfoo is
+ \$wfoo_smW (GHC.Prim.-# ds_Xmb y_amr) wild_Xf
During matching we expand wild_Xf to (Just n_acT). But then we must also
expand n_acT to (I# y_amr). And we can only do that if we look up n_acT
This pass runs over the tree (without changing it) and reports such.
\begin{code}
-ruleCheckProgram :: CompilerPhase -> String -> RuleBase -> [CoreBind] -> SDoc
--- Report partial matches for rules beginning
--- with the specified string
+-- | Report partial matches for rules beginning with the specified
+-- string for the purposes of error reporting
+ruleCheckProgram :: CompilerPhase -- ^ Phase to check in
+ -> String -- ^ Rule pattern
+ -> RuleBase -- ^ Database of rules
+ -> [CoreBind] -- ^ Bindings to check in
+ -> SDoc -- ^ Resulting check message
ruleCheckProgram phase rule_pat rule_base binds
| isEmptyBag results
= text "Rule check results: no rule application sites"
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