NCG: Split linear allocator into separate modules.

1 files changed, 72 insertions, 0 deletions

diff --git a/compiler/nativeGen/RegAlloc/Linear/StackMap.hs b/compiler/nativeGen/RegAlloc/Linear/StackMap.hs
new file mode 100644
index 0000000000..56382aa804
--- /dev/null
+++ b/compiler/nativeGen/RegAlloc/Linear/StackMap.hs
@@ -0,0 +1,72 @@
+
+-- | The assignment of virtual registers to stack slots
+
+-- 	We have lots of stack slots. Memory-to-memory moves are a pain on most
+-- 	architectures. Therefore, we avoid having to generate memory-to-memory moves
+-- 	by simply giving every virtual register its own stack slot.
+
+-- 	The StackMap stack map keeps track of virtual register - stack slot
+-- 	associations and of which stack slots are still free. Once it has been
+-- 	associated, a stack slot is never "freed" or removed from the StackMap again,
+-- 	it remains associated until we are done with the current CmmProc.
+--
+module RegAlloc.Linear.StackMap (
+	StackSlot,
+	StackMap(..),
+	emptyStackMap,
+	getStackSlotFor
+)
+
+where
+
+import RegAllocInfo	(maxSpillSlots)
+
+import Outputable
+import UniqFM
+import Unique
+
+
+-- | Identifier for a stack slot.
+type StackSlot = Int
+
+data StackMap 
+	= StackMap 
+
+	-- | The slots that are still available to be allocated.
+	{ stackMapFreeSlots	:: [StackSlot]
+
+	-- | Assignment of vregs to stack slots.
+	, stackMapAssignment	:: UniqFM StackSlot }
+
+
+-- | An empty stack map, with all slots available.
+emptyStackMap :: StackMap
+emptyStackMap = StackMap [0..maxSpillSlots] emptyUFM
+
+
+-- | If this vreg unique already has a stack assignment then return the slot number,
+--	otherwise allocate a new slot, and update the map.
+--
+getStackSlotFor :: StackMap -> Unique -> (StackMap, Int)
+
+getStackSlotFor (StackMap [] _) _
+
+        -- This happens all the time when trying to compile darcs' SHA1.hs, see Track #1993
+	--	SHA1.lhs has also been added to the Crypto library on Hackage,
+	--	so we see this all the time.  
+	--
+	-- It would be better to automatically invoke the graph allocator, or do something
+	--	else besides panicing, but that's a job for a different day.  -- BL 2009/02
+	--
+	= panic $   "RegAllocLinear.getStackSlotFor: out of stack slots\n"
+		++  "   If you are trying to compile SHA1.hs from the crypto library then this\n"
+		++  "   is a known limitation in the linear allocator.\n"
+		++  "\n"
+		++  "   Try enabling the graph colouring allocator with -fregs-graph instead."
+		++  "   You can still file a bug report if you like.\n"
+		
+getStackSlotFor fs@(StackMap (freeSlot:stack') reserved) reg =
+    case lookupUFM reserved reg of
+    	Just slot	-> (fs, slot)
+    	Nothing		-> (StackMap stack' (addToUFM reserved reg freeSlot), freeSlot)
+