Better panic message in RegAllocLinear

diff --git a/compiler/nativeGen/RegAllocLinear.hs b/compiler/nativeGen/RegAllocLinear.hs
index c67ce3e..c4a5a4a 100644 (file)
--- a/compiler/nativeGen/RegAllocLinear.hs
+++ b/compiler/nativeGen/RegAllocLinear.hs
@@ -699,8 +699,11 @@ allocateRegsAndSpill reading keep spills alloc (r:rs) = do
                -- to spill.  We just pick the first one that isn't used in 
                -- the current instruction for now.
 
-               let (temp_to_push_out, my_reg) = myHead "regalloc" candidates2
-
+               let (temp_to_push_out, my_reg) 
+                       = case candidates2 of
+                               []      -> panic "RegAllocLinear.allocRegsAndSpill: no spill candidates"
+                               (x:_)   -> x
+                               
                (spill_insn, slot) <- spillR (RealReg my_reg) temp_to_push_out
                let spill_store  = (if reading then id else reverse)
                                        [ COMMENT (fsLit "spill alloc") 
@@ -741,9 +744,6 @@ loadTemp _ _ _ _ spills =
    return spills
 
 
-myHead s [] = panic s
-myHead _ (x:_) = x
-
 -- -----------------------------------------------------------------------------
 -- Joining a jump instruction to its targets