X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=compiler%2Fcmm%2FZipCfgCmmRep.hs;h=451450e6f0b4ad44ac215dcb7f97fa3bc5334bcc;hb=2440b61a15e56f0cdee349c2574cdfc40adc6053;hp=27191f38c9844b336893f3ae48278a1dacdafc1a;hpb=b25c93f1c914d81d77aeafeb49263f29bed128aa;p=ghc-hetmet.git

diff --git a/compiler/cmm/ZipCfgCmmRep.hs b/compiler/cmm/ZipCfgCmmRep.hs
index 27191f3..451450e 100644
--- a/compiler/cmm/ZipCfgCmmRep.hs
+++ b/compiler/cmm/ZipCfgCmmRep.hs
@@ -103,12 +103,15 @@ data Last
 	    -- This is really needed at the *return* point rather than here
 	    -- at the call, but in practice it's convenient to record it here.
 
-        cml_ret_off :: Maybe UpdFrameOffset
-          -- Stack offset for return (update frames);
-          -- The return offset should be Nothing only if we have to create
-          -- a new call, e.g. for a procpoint, in which case it's an invariant
-          -- that the call does not stand for a return or a tail call,
-          -- and the successor does not need an info table.
+        cml_ret_off :: Maybe ByteOff
+          -- For calls *only*, the byte offset of the base of the frame that
+	  -- must be described by the info table for the return point.  
+ 	  -- The older words are an update frames, which have their own
+	  -- info-table and layout information
+
+	  -- From a liveness point of view, the stack words older than
+	  -- cml_ret_off are treated as live, even if the sequel of
+	  -- the call goes into a loop.
 	}
 
 data MidCallTarget	-- The target of a MidUnsafeCall
@@ -456,10 +459,9 @@ pprMiddle stmt = pp_stmt <+> pp_debug
     	-- call "ccall" foo(x, y)[r1, r2];
     	-- ToDo ppr volatile
     	MidForeignCall safety target results args ->
-    	    hsep [ if null results
-    	              then empty
-    	              else parens (commafy $ map ppr results) <+> equals,
-                      ppr_safety safety,
+    	    hsep [ ppUnless (null results) $
+    	              parens (commafy $ map ppr results) <+> equals,
+                   ppr_safety safety,
     	           ptext $ sLit "call", 
     	           ppr_call_target target <> parens (commafy $ map ppr args) <> semi]