+ replace_eid (G.LGraph eid off blocks) = G.LGraph (lookup eid) off blocks
+ middle m@(MidComment _) = m
+ middle (MidAssign r e) = MidAssign r (exp e)
+ middle (MidStore addr e) = MidStore (exp addr) (exp e)
+ middle (MidUnsafeCall tgt fs as) = MidUnsafeCall (midcall tgt) fs (map exp as)
+ middle (MidAddToContext e es) = MidAddToContext (exp e) (map exp es)
+ last (LastBranch id) = LastBranch (lookup id)
+ last (LastCondBranch e ti fi) = LastCondBranch (exp e) (lookup ti) (lookup fi)
+ last (LastSwitch e tbl) = LastSwitch (exp e) (map (fmap lookup) tbl)
+ last (LastCall tgt mb_id s) = LastCall (exp tgt) (fmap lookup mb_id) s
+ last (LastJump e s) = LastJump (exp e) s
+ last (LastReturn s) = LastReturn s
+ midcall (ForeignTarget e c) = ForeignTarget (exp e) c
+ midcall m@(PrimTarget _) = m
+ exp e@(CmmLit _) = e
+ exp (CmmLoad addr ty) = CmmLoad (exp addr) ty
+ exp e@(CmmReg _) = e
+ exp (CmmMachOp op es) = CmmMachOp op $ map exp es
+ exp e@(CmmRegOff _ _) = e
+ exp (CmmStackSlot (CallArea (Young id)) i) =
+ CmmStackSlot (CallArea (Young (lookup id))) i
+ exp e@(CmmStackSlot _ _) = e
+ lookup id = fmap lookup (lookupBlockEnv env id) `orElse` id
+
+----------------------------------------------------------------
+-- Build a map from a block to its set of predecessors. Very useful.
+predMap :: G.LastNode l => G.LGraph m l -> BlockEnv BlockSet
+predMap g = G.fold_blocks add_preds emptyBlockEnv g -- find the back edges
+ where add_preds b env = foldl (add b) env (G.succs b)
+ add (G.Block bid _ _) env b' =
+ extendBlockEnv env b' $
+ extendBlockSet (lookupBlockEnv env b' `orElse` emptyBlockSet) bid
+----------------------------------------------------------------
+-- If a block B branches to a label L, and L has no other predecessors,
+-- then we can splice the block starting with L onto the end of B.
+-- Because this optmization can be inhibited by unreachable blocks,
+-- we first take a pass to drops unreachable blocks.
+-- Order matters, so we work bottom up (reverse postorder DFS).
+--
+-- To ensure correctness, we have to make sure that the BlockId of the block
+-- we are about to eliminate is not named in another instruction
+-- (except an adjacent stack pointer adjustment, which we expect and also eliminate).
+-- For
+--
+-- Note: This optimization does _not_ subsume branch chain elimination.
+blockConcatZ :: Tx CmmGraph
+blockConcatZ = removeUnreachableBlocksZ `seqTx` blockConcatZ'
+blockConcatZ' :: Tx CmmGraph
+blockConcatZ' g@(G.LGraph eid off blocks) =
+ tx $ pprTrace "concatMap" (ppr concatMap) $ replaceLabelsZ concatMap $ G.LGraph eid off blocks'
+ where (changed, blocks', concatMap) =
+ foldr maybe_concat (False, blocks, emptyBlockEnv) $ G.postorder_dfs g
+ maybe_concat b@(G.Block bid _ _) (changed, blocks', concatMap) =
+ let unchanged = (changed, extendBlockEnv blocks' bid b, concatMap)
+ in case G.goto_end $ G.unzip b of
+ (h, G.LastOther (LastBranch b')) ->
+ if num_preds b' == 1 then
+ (True, extendBlockEnv blocks' bid $ splice blocks' h b',
+ extendBlockEnv concatMap b' bid)
+ else unchanged
+ _ -> unchanged
+ num_preds bid = liftM sizeBlockSet (lookupBlockEnv backEdges bid) `orElse` 0
+ backEdges = predMap g
+ splice blocks' h bid' =
+ case lookupBlockEnv blocks' bid' of
+ Just (G.Block _ Nothing t) -> G.zip $ G.ZBlock h t
+ Just (G.Block _ (Just _) _) ->
+ panic "trying to concatenate but successor block has incoming args"
+ Nothing -> panic "unknown successor block"
+ tx = if changed then aTx else noTx