module SPARC.ShortcutJump (
	JumpDest(..), getJumpDestBlockId,
	canShortcut,
	shortcutJump,
	shortcutStatics,
	shortBlockId
)

where

import SPARC.Instr
import SPARC.Imm

import CLabel
import BlockId
import OldCmm

import Panic
import Unique



data JumpDest 
	= DestBlockId BlockId 
	| DestImm Imm

getJumpDestBlockId :: JumpDest -> Maybe BlockId
getJumpDestBlockId (DestBlockId bid) = Just bid
getJumpDestBlockId _                 = Nothing


canShortcut :: Instr -> Maybe JumpDest
canShortcut _ = Nothing


shortcutJump :: (BlockId -> Maybe JumpDest) -> Instr -> Instr
shortcutJump _ other = other



shortcutStatics :: (BlockId -> Maybe JumpDest) -> CmmStatics -> CmmStatics
shortcutStatics fn (Statics lbl statics)
  = Statics lbl $ map (shortcutStatic fn) statics
  -- we need to get the jump tables, so apply the mapping to the entries
  -- of a CmmData too.

shortcutLabel :: (BlockId -> Maybe JumpDest) -> CLabel -> CLabel
shortcutLabel fn lab
  | Just uq <- maybeAsmTemp lab = shortBlockId fn (mkBlockId uq)
  | otherwise                   = lab

shortcutStatic :: (BlockId -> Maybe JumpDest) -> CmmStatic -> CmmStatic
shortcutStatic fn (CmmStaticLit (CmmLabel lab))
	= CmmStaticLit (CmmLabel (shortcutLabel fn lab))
shortcutStatic fn (CmmStaticLit (CmmLabelDiffOff lbl1 lbl2 off))
	= CmmStaticLit (CmmLabelDiffOff (shortcutLabel fn lbl1) lbl2 off)
-- slightly dodgy, we're ignoring the second label, but this
-- works with the way we use CmmLabelDiffOff for jump tables now.
shortcutStatic _ other_static
        = other_static


shortBlockId :: (BlockId -> Maybe JumpDest) -> BlockId -> CLabel
shortBlockId fn blockid =
   case fn blockid of
      Nothing -> mkAsmTempLabel (getUnique blockid)
      Just (DestBlockId blockid')  -> shortBlockId fn blockid'
      Just (DestImm (ImmCLbl lbl)) -> lbl
      _other -> panic "shortBlockId"