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

diff --git a/compiler/nativeGen/RegAllocLinear.hs b/compiler/nativeGen/RegAllocLinear.hs
index 888ef16..e6491b7 100644 (file)
--- a/compiler/nativeGen/RegAllocLinear.hs
+++ b/compiler/nativeGen/RegAllocLinear.hs
@@ -222,7 +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