substUnfolding subst unf@(CoreUnfolding { uf_tmpl = tmpl, uf_guidance = guide@(InlineRule {}) })
-- Retain an InlineRule!
= seqExpr new_tmpl `seq`
- new_mb_wkr `seq`
- unf { uf_tmpl = new_tmpl, uf_guidance = guide { ug_ir_info = new_mb_wkr } }
+ new_info `seq`
+ unf { uf_tmpl = new_tmpl, uf_guidance = guide { ir_info = new_info } }
where
- new_tmpl = substExpr subst tmpl
- new_mb_wkr = substInlineRuleGuidance subst (ug_ir_info guide)
+ new_tmpl = substExpr subst tmpl
+ new_info = substInlineRuleInfo subst (ir_info guide)
substUnfolding _ (CoreUnfolding {}) = NoUnfolding -- Discard
-- Always zap a CoreUnfolding, to save substitution work
-substUnfolding _ unf = unf -- Otherwise no substitution to do
+substUnfolding _ unf = unf -- NoUnfolding, OtherCon
-------------------
-substInlineRuleGuidance :: Subst -> InlineRuleInfo -> InlineRuleInfo
-substInlineRuleGuidance subst (InlWrapper wkr)
- = case lookupIdSubst subst wkr of
- Var w1 -> InlWrapper w1
- other -> WARN( not (exprIsTrivial other), text "CoreSubst.substWorker:" <+> ppr wkr )
- InlUnSat -- Worker has got substituted away altogether
- -- (This can happen if it's trivial, via
- -- postInlineUnconditionally, hence only warning)
-substInlineRuleGuidance _ info = info
+substInlineRuleInfo :: Subst -> InlineRuleInfo -> InlineRuleInfo
+substInlineRuleInfo (Subst in_scope ids _) (InlWrapper wkr)
+ | Just (Var w1) <- lookupVarEnv ids wkr = InlWrapper w1
+ | Just w1 <- lookupInScope in_scope wkr = InlWrapper w1
+ | otherwise = WARN( True, text "Interesting! CoreSubst.substWorker:" <+> ppr wkr )
+ InlVanilla -- Note [Worker inlining]
+substInlineRuleInfo _ info = info
------------------
substIdOcc :: Subst -> Id -> Id
| otherwise = Type.tyVarsOfType (lookupTvSubst subst fv)
\end{code}
+Note [Worker inlining]
+~~~~~~~~~~~~~~~~~~~~~~
+A worker can get sustituted away entirely.
+ - it might be trivial
+ - it might simply be very small
+We do not treat an InlWrapper as an 'occurrence' in the occurence
+analyser, so it's possible that the worker is not even in scope any more.
+
+In all all these cases we simply drop the special case, returning to
+InlVanilla. The WARN is just so I can see if it happens a lot.
+
+
%************************************************************************
%* *
The Very Simple Optimiser