X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2FcoreSyn%2FCoreUtils.lhs;h=7e5fbb4866cb072505dc4fd66bb628c05d7c0dbc;hb=e66106a53dab255670ad1229b280cf36d16bc44c;hp=5c26e0da780bba25a19ae73eb0c67395d0df04f6;hpb=31d1bcbed45e4b6ff9543193ab7813e05b29e9b4;p=ghc-hetmet.git

diff --git a/ghc/compiler/coreSyn/CoreUtils.lhs b/ghc/compiler/coreSyn/CoreUtils.lhs
index 5c26e0d..7e5fbb4 100644
--- a/ghc/compiler/coreSyn/CoreUtils.lhs
+++ b/ghc/compiler/coreSyn/CoreUtils.lhs
@@ -214,7 +214,12 @@ mkCoerce2 to_ty from_ty expr
 mkSCC :: CostCentre -> Expr b -> Expr b
 	-- Note: Nested SCC's *are* preserved for the benefit of
 	--       cost centre stack profiling
+	-- Note2: We throw away an SCC on a single variable.  If the
+	--	 variable is a value, then there is no work to do in
+	-- 	 evaluating it, and if it is a thunk, then it will be
+	--       attributed to its own CCS anyhow.
 mkSCC cc (Lit lit)  	    = Lit lit
+mkSCC cc (Var v)	    = Var v
 mkSCC cc (Lam x e)  	    = Lam x (mkSCC cc e)  -- Move _scc_ inside lambda
 mkSCC cc (Note (SCC cc') e) = Note (SCC cc) (Note (SCC cc') e)
 mkSCC cc (Note n e) 	    = Note n (mkSCC cc e) -- Move _scc_ inside notes