
module SPARC.Stack (
	spRel,
	fpRel,
	spillSlotToOffset,
	maxSpillSlots
)

where

import SPARC.AddrMode
import SPARC.Regs
import SPARC.Base
import SPARC.Imm

import Outputable

-- | Get an AddrMode relative to the address in sp.
--	This gives us a stack relative addressing mode for volatile
-- 	temporaries and for excess call arguments.  
--
spRel :: Int		-- ^ stack offset in words, positive or negative
      -> AddrMode

spRel n	= AddrRegImm sp (ImmInt (n * wordLength))


-- | Get an address relative to the frame pointer.
--	This doesn't work work for offsets greater than 13 bits; we just hope for the best
--
fpRel :: Int -> AddrMode
fpRel n
	= AddrRegImm fp (ImmInt (n * wordLength))


-- | Convert a spill slot number to a *byte* offset, with no sign.
--
spillSlotToOffset :: Int -> Int
spillSlotToOffset slot
	| slot >= 0 && slot < maxSpillSlots
	= 64 + spillSlotSize * slot

	| otherwise
	= pprPanic "spillSlotToOffset:" 
	              (   text "invalid spill location: " <> int slot
		      $$  text "maxSpillSlots:          " <> int maxSpillSlots)


-- | The maximum number of spill slots available on the C stack.
--	If we use up all of the slots, then we're screwed.
--
--	Why do we reserve 64 bytes, instead of using the whole thing??
--		-- BL 2009/02/15
--
maxSpillSlots :: Int
maxSpillSlots 
	= ((spillAreaLength - 64) `div` spillSlotSize) - 1

