X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=compiler%2Fcmm%2FCmmExpr.hs;h=39099f1e055c283da79dbb8a944c2c9a885666cd;hb=7fc01c4671980ea3c66d549c0ece4d82fd3f5ade;hp=7ea1c4760ac6c8d6b463ce867ff5c74f6f748871;hpb=31a9d04804d9cacda35695c5397590516b964964;p=ghc-hetmet.git

diff --git a/compiler/cmm/CmmExpr.hs b/compiler/cmm/CmmExpr.hs
index 7ea1c47..39099f1 100644
--- a/compiler/cmm/CmmExpr.hs
+++ b/compiler/cmm/CmmExpr.hs
@@ -22,6 +22,7 @@ module CmmExpr
     , DefinerOfSlots, UserOfSlots, foldSlotsDefd, foldSlotsUsed
     , RegSet, emptyRegSet, elemRegSet, extendRegSet, deleteFromRegSet, mkRegSet
             , plusRegSet, minusRegSet, timesRegSet
+    , regUsedIn
     , Area(..), AreaId(..), SubArea, SubAreaSet, AreaMap, isStackSlotOf
  
    -- MachOp
@@ -49,10 +50,7 @@ import CLabel
 import Constants
 import FastString
 import FiniteMap
-import Maybes
-import Monad
 import Outputable
-import Panic
 import Unique
 import UniqSet
 
@@ -98,13 +96,32 @@ data Area
   deriving (Eq, Ord)
 
 data AreaId
-  = Old -- entry parameters, jumps, and returns share one call area at old end of stack
+  = Old            -- See Note [Old Area]
   | Young BlockId
   deriving (Eq, Ord)
 
+{- Note [Old Area] 
+~~~~~~~~~~~~~~~~~~
+There is a single call area 'Old', allocated at the extreme old
+end of the stack frame (ie just younger than the return address)
+which holds:
+  * incoming (overflow) parameters, 
+  * outgoing (overflow) parameter to tail calls,
+  * outgoing (overflow) result values 
+  * the update frame (if any)
+
+Its size is the max of all these requirements.  On entry, the stack
+pointer will point to the youngest incoming parameter, which is not
+necessarily at the young end of the Old area.
+
+End of note -}
+
 type SubArea    = (Area, Int, Int) -- area, offset, width
 type SubAreaSet = FiniteMap Area [SubArea]
+
 type AreaMap    = FiniteMap Area Int
+     -- Byte offset of the oldest byte of the Area, 
+     -- relative to the oldest byte of the Old Area
 
 data CmmLit
   = CmmInt Integer  Width
@@ -258,6 +275,16 @@ instance DefinerOfLocalRegs a => DefinerOfLocalRegs (Maybe a) where
   foldRegsDefd _ set Nothing  = set
   foldRegsDefd f set (Just x) = foldRegsDefd f set x
 
+-----------------------------------------------------------------------------
+-- Another reg utility
+
+regUsedIn :: CmmReg -> CmmExpr -> Bool
+_   `regUsedIn` CmmLit _ 	 = False
+reg `regUsedIn` CmmLoad e  _ 	 = reg `regUsedIn` e
+reg `regUsedIn` CmmReg reg' 	 = reg == reg'
+reg `regUsedIn` CmmRegOff reg' _ = reg == reg'
+reg `regUsedIn` CmmMachOp _ es   = any (reg `regUsedIn`) es
+_   `regUsedIn` CmmStackSlot _ _ = False
 
 -----------------------------------------------------------------------------
 --    Stack slots