expand "out of stack slots" panic to suggest using -fregs-graph, see #1993

[ghc-hetmet.git] / compiler / nativeGen / RegAllocLinear.hs

diff --git a/compiler/nativeGen/RegAllocLinear.hs b/compiler/nativeGen/RegAllocLinear.hs
index debda83..e6491b7 100644 (file)
--- a/compiler/nativeGen/RegAllocLinear.hs
+++ b/compiler/nativeGen/RegAllocLinear.hs
@@ -155,8 +155,9 @@ getFreeRegs :: RegClass -> FreeRegs -> [RegNo]      -- lazilly
 getFreeRegs cls (FreeRegs g f)
     | RcDouble <- cls = go f (0x80000000) 63
     | RcInteger <- cls = go g (0x80000000) 31
+    | otherwise = pprPanic "RegAllocLinear.getFreeRegs: Bad cls" (ppr cls)
     where
-        go x 0 i = []
+        go _ 0 _ = []
         go x m i | x .&. m /= 0 = i : (go x (m `shiftR` 1) $! i-1)
                  | otherwise    = go x (m `shiftR` 1) $! i-1
 
@@ -221,7 +222,8 @@ emptyStackMap = StackMap [0..maxSpillSlots] emptyUFM
 
 getStackSlotFor :: StackMap -> Unique -> (StackMap,Int)
 getStackSlotFor (StackMap [] _) _
-       = panic "RegAllocLinear.getStackSlotFor: out of stack slots"
+       = panic "RegAllocLinear.getStackSlotFor: out of stack slots, try -fregs-graph"
+        -- This happens with darcs' SHA1.hs, see #1993
 
 getStackSlotFor fs@(StackMap (freeSlot:stack') reserved) reg =
     case lookupUFM reserved reg of