canShortcut _ = Nothing
+-- The helper ensures that we don't follow cycles.
shortcutJump :: (BlockId -> Maybe JumpDest) -> Instr -> Instr
-shortcutJump fn insn@(JXX cc id) =
- case fn id of
- Nothing -> insn
- Just (DestBlockId id') -> shortcutJump fn (JXX cc id')
- Just (DestImm imm) -> shortcutJump fn (JXX_GBL cc imm)
-
-shortcutJump _ other = other
+shortcutJump fn insn = shortcutJump' fn emptyBlockSet insn
+ where shortcutJump' fn seen insn@(JXX cc id) =
+ if elemBlockSet id seen then insn
+ else case fn id of
+ Nothing -> insn
+ Just (DestBlockId id') -> shortcutJump' fn seen' (JXX cc id')
+ Just (DestImm imm) -> shortcutJump' fn seen' (JXX_GBL cc imm)
+ where seen' = extendBlockSet seen id
+ shortcutJump' _ _ other = other
-- Here because it knows about JumpDest