From 6c9fbc473bb7b5a98f0945678bc47bde39a75e8d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bj=C3=B6rn=20Gustavsson?= <bjorn@erlang.org>
Date: Fri, 30 Dec 2011 12:17:04 +0100
Subject: v3_kernel: Don't attempt to share identical literals

It is unlikely that sharing literals will actually save any time.
Literals that can be shared are usually small. It is more likely
that maintaining the dictionary of literals will waste time.
---
 lib/compiler/src/v3_kernel.erl | 65 ++++++++++--------------------------------
 1 file changed, 15 insertions(+), 50 deletions(-)

(limited to 'lib/compiler/src')

diff --git a/lib/compiler/src/v3_kernel.erl b/lib/compiler/src/v3_kernel.erl
index 8bbaf183c8..0638041950 100644
--- a/lib/compiler/src/v3_kernel.erl
+++ b/lib/compiler/src/v3_kernel.erl
@@ -118,7 +118,6 @@ copy_anno(Kdst, Ksrc) ->
 	       funs=[],				%Fun functions
 	       free=[],				%Free variables
 	       ws=[]   :: [warning()],		%Warnings.
-	       lit,			        %Constant pool for literals.
 	       guard_refc=0}).			%> 0 means in guard
 
 -spec module(cerl:c_module(), [compile:option()]) ->
@@ -127,7 +126,7 @@ copy_anno(Kdst, Ksrc) ->
 module(#c_module{anno=A,name=M,exports=Es,attrs=As,defs=Fs}, _Options) ->
     Kas = attributes(As),
     Kes = map(fun (#c_var{name={_,_}=Fname}) -> Fname end, Es),
-    St0 = #kern{lit=dict:new()},
+    St0 = #kern{},
     {Kfs,St} = mapfoldl(fun function/2, St0, Fs),
     {ok,#k_mdef{anno=A,name=M#c_literal.val,exports=Kes,attributes=Kas,
 		body=Kfs ++ St#kern.funs},lists:sort(St#kern.ws)}.
@@ -248,26 +247,20 @@ expr(#c_var{anno=A,name={_Name,Arity}}=Fname, Sub, St) ->
     expr(Fun, Sub, St);
 expr(#c_var{anno=A,name=V}, Sub, St) ->
     {#k_var{anno=A,name=get_vsub(V, Sub)},[],St};
-expr(#c_literal{}=Lit, Sub, St) ->
-    Core = handle_literal(Lit),
-    expr(Core, Sub, St);
-expr(#k_literal{val=Val0}=Klit, _Sub, #kern{lit=Literals0}=St) ->
-    %% Share identical literals to save some space and time during compilation.
-    case dict:find(Val0, Literals0) of
-	{ok,Val} ->
-	    {Klit#k_literal{val=Val},[],St};
-	error ->
-	    Literals = dict:store(Val0, Val0, Literals0),
-	    {Klit,[],St#kern{lit=Literals}}
-    end;
-expr(#k_nil{}=V, _Sub, St) ->
-    {V,[],St};
-expr(#k_int{}=V, _Sub, St) ->
-    {V,[],St};
-expr(#k_float{}=V, _Sub, St) ->
-    {V,[],St};
-expr(#k_atom{}=V, _Sub, St) ->
-    {V,[],St};
+expr(#c_literal{anno=A,val=V}, _Sub, St) ->
+    Klit = case V of
+	       [] ->
+		   #k_nil{anno=A};
+	       V when is_integer(V) ->
+		   #k_int{anno=A,val=V};
+	       V when is_float(V) ->
+		   #k_float{anno=A,val=V};
+	       V when is_atom(V) ->
+		   #k_atom{anno=A,val=V};
+	       _ ->
+		   #k_literal{anno=A,val=V}
+	   end,
+    {Klit,[],St};
 expr(#c_cons{anno=A,hd=Ch,tl=Ct}, Sub, St0) ->
     %% Do cons in two steps, first the expressions left to right, then
     %% any remaining literals right to left.
@@ -1845,34 +1838,6 @@ pat_list_vars(Ps) ->
 		  {union(Used0, Used),union(New0, New)} end,
 	  {[],[]}, Ps).
 
-%% handle_literal(Literal, Anno) -> Kernel
-%%  Examine the literal. Complex (heap-based) literals such as lists,
-%%  tuples, and binaries should be kept as literals and put into the constant pool.
-%%
-%%  (If necessary, this function could be extended to go through the literal
-%%  and convert huge binary literals to bit syntax expressions. We don't do that
-%%  because v3_core does not produce huge binary literals, and the optimizations in
-%%  sys_core_fold don't do much optimizations of binaries. IF THAT CHANGE IS MADE,
-%%  ALSO CHANGE sys_core_dsetel.)
-
-handle_literal(#c_literal{anno=A,val=V}) ->
-    case V of
-	[_|_] ->
-	    #k_literal{anno=A,val=V};
-	[] ->
-	    #k_nil{anno=A};
-	V when is_tuple(V) ->
-	    #k_literal{anno=A,val=V};
-	V when is_bitstring(V) ->
-	    #k_literal{anno=A,val=V};
-	V when is_integer(V) ->
-	    #k_int{anno=A,val=V};
-	V when is_float(V) ->
-	    #k_float{anno=A,val=V};
-	V when is_atom(V) ->
-	    #k_atom{anno=A,val=V}
-    end.
-
 make_list(Es) ->
     foldr(fun(E, Acc) ->
  		  #c_cons{hd=E,tl=Acc}
-- 
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