optimization for short labels

git-svn-id: http://caml.inria.fr/svn/ocaml/branches/newoolabmult@6004 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02
bmeurer · Dec 5, 2003 · 3f1a4d0 · 3f1a4d0
1 parent e685622
commit 3f1a4d0
Showing 1 changed file with 8 additions and 7 deletions.
diff --git a/asmcomp/cmmgen.ml b/asmcomp/cmmgen.ml
@@ -334,13 +334,14 @@ let lookup_tag obj tag =
       | _ ->
           untag_uint31 tag
     in
-    let lab =
-      Cop(Cadda,
-          [Cop(Clsr,
-               [Cop(Clsl, [Cop(Cmuli, [tag; c]);
-                           Cconst_int(size_addr*8 - 31)]);
-                m]);
-           Cconst_int 2]) in
+    let mul =
+      match tag with
+        Cconst_natint n when n < 0x40000000n && size_addr = 4 ->
+          Cop(Cmuli, [Cconst_natint (Nativeint.shift_left n 1); c])
+      | _ ->
+          Cop(Clsl, [Cop(Cmuli, [tag; c]); Cconst_int(size_addr*8 - 31)])
+    in
+    let lab = Cop(Cadda, [Cop(Clsr, [mul; m]); Cconst_int 2]) in
     Clet(table, Cop (Cload Word, [obj]),
          Cop(Cload Word,
              [Cop (Cadda, [Cvar table; lsl_const lab log2_size_addr])])))