X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=compiler%2Fcmm%2FCmm.hs;h=0d1876e0e61068db72f6c8c766dc48b1d08c4a72;hb=d5e821c43df34fa228727e7f4e9453d0fde39fb6;hp=d30f96317e1ca9ca64303e6071412f4020866792;hpb=49c98d143c382a1341e1046f5ca00819a25691ba;p=ghc-hetmet.git

diff --git a/compiler/cmm/Cmm.hs b/compiler/cmm/Cmm.hs
index d30f963..0d1876e 100644
--- a/compiler/cmm/Cmm.hs
+++ b/compiler/cmm/Cmm.hs
@@ -10,17 +10,17 @@ module Cmm (
 	GenCmm(..), Cmm,
 	GenCmmTop(..), CmmTop,
 	GenBasicBlock(..), CmmBasicBlock, blockId, blockStmts,
-	CmmStmt(..),  
+	CmmStmt(..), CmmActuals, CmmFormals,
 	CmmCallTarget(..),
 	CmmStatic(..), Section(..),
 	CmmExpr(..), cmmExprRep, 
 	CmmReg(..), cmmRegRep,
 	CmmLit(..), cmmLitRep,
 	LocalReg(..), localRegRep,
-	BlockId(..),
+	BlockId(..), BlockEnv,
 	GlobalReg(..), globalRegRep,
 
-	node, nodeReg, spReg, hpReg,
+	node, nodeReg, spReg, hpReg, spLimReg
   ) where
 
 #include "HsVersions.h"
@@ -29,6 +29,7 @@ import MachOp
 import CLabel
 import ForeignCall
 import Unique
+import UniqFM
 import FastString
 
 import Data.Word
@@ -113,8 +114,8 @@ data CmmStmt
 
   | CmmCall	 		 -- A foreign call, with 
      CmmCallTarget
-     [(CmmReg,MachHint)]	 -- zero or more results
-     [(CmmExpr,MachHint)]	 -- zero or more arguments
+     CmmFormals			 -- zero or more results
+     CmmActuals			 -- zero or more arguments
      (Maybe [GlobalReg])	 -- Global regs that may need to be saved
 				 -- if they will be clobbered by the call.
 				 -- Nothing <=> save *all* globals that
@@ -130,8 +131,50 @@ data CmmStmt
 	--	one  -> second block etc
 	-- Undefined outside range, and when there's a Nothing
 
-  | CmmJump CmmExpr [LocalReg]    -- Jump to another function, with these 
-				  -- parameters.
+  | CmmJump CmmExpr               -- Jump to another function,
+    CmmActuals                    -- with these parameters.
+
+  | CmmReturn                     -- Return from a function,
+    CmmActuals                    -- with these return values.
+
+type CmmActuals = [(CmmExpr,MachHint)]
+type CmmFormals = [(CmmReg,MachHint)]
+
+{-
+Discussion
+~~~~~~~~~~
+
+One possible problem with the above type is that the only way to do a
+non-local conditional jump is to encode it as a branch to a block that
+contains a single jump.  This leads to inefficient code in the back end.
+
+One possible way to fix this would be:
+
+data CmmStat = 
+  ...
+  | CmmJump CmmBranchDest
+  | CmmCondJump CmmExpr CmmBranchDest
+  ...
+
+data CmmBranchDest
+  = Local BlockId
+  | NonLocal CmmExpr [LocalReg]
+
+In favour:
+
++ one fewer constructors in CmmStmt
++ allows both cond branch and switch to jump to non-local destinations
+
+Against:
+
+- not strictly necessary: can already encode as branch+jump
+- not always possible to implement any better in the back end
+- could do the optimisation in the back end (but then plat-specific?)
+- C-- doesn't have it
+- back-end optimisation might be more general (jump shortcutting)
+
+So we'll stick with the way it is, and add the optimisation to the NCG.
+-}
 
 -----------------------------------------------------------------------------
 --		CmmCallTarget
@@ -164,6 +207,7 @@ data CmmExpr
 	--        ** is shorthand only, meaning **
 	-- CmmMachOp (MO_S_Add rep (CmmReg reg) (CmmLit (CmmInt i rep)))
 	--	where rep = cmmRegRep reg
+  deriving Eq
 
 cmmExprRep :: CmmExpr -> MachRep
 cmmExprRep (CmmLit lit)      = cmmLitRep lit
@@ -212,6 +256,7 @@ data CmmLit
         -- It is also used inside the NCG during when generating
         -- position-independent code. 
   | CmmLabelDiffOff CLabel CLabel Int   -- label1 - label2 + offset
+  deriving Eq
 
 cmmLitRep :: CmmLit -> MachRep
 cmmLitRep (CmmInt _ rep)    = rep
@@ -231,6 +276,8 @@ newtype BlockId = BlockId Unique
 instance Uniquable BlockId where
   getUnique (BlockId u) = u
 
+type BlockEnv a = UniqFM {- BlockId -} a
+
 -----------------------------------------------------------------------------
 --		Static Data
 -----------------------------------------------------------------------------
@@ -307,9 +354,10 @@ data GlobalReg
 	 )
 
 -- convenient aliases
-spReg, hpReg, nodeReg :: CmmReg
+spReg, hpReg, spLimReg, nodeReg :: CmmReg
 spReg = CmmGlobal Sp
 hpReg = CmmGlobal Hp
+spLimReg = CmmGlobal SpLim
 nodeReg = CmmGlobal node
 
 node :: GlobalReg