diff --git a/asmcomp/amd64/selection.ml b/asmcomp/amd64/selection.ml
index 4921e51..bce8104 100644
--- a/asmcomp/amd64/selection.ml
+++ b/asmcomp/amd64/selection.ml
@@ -168,6 +168,9 @@ method! select_operation op args =
         [arg1; Cconst_int n] when self#is_immediate n
                                && n = 1 lsl (Misc.log2 n) ->
           (Iintop_imm(Idiv, n), [arg1])
+        | [arg1; Cconst_natint n] when self#is_immediate_natint n
+                               && n = Nativeint.shift_left 1n (Misc.log2 (Nativeint.to_int n)) ->
+          (Iintop_imm(Idiv, Nativeint.to_int n), [arg1])
       | _ -> (Iintop Idiv, args)
       end
   | Cmodi ->
@@ -175,6 +178,9 @@ method! select_operation op args =
         [arg1; Cconst_int n] when self#is_immediate n
                                && n = 1 lsl (Misc.log2 n) ->
           (Iintop_imm(Imod, n), [arg1])
+        | [arg1; Cconst_natint n] when self#is_immediate_natint n
+                               && n = Nativeint.shift_left 1n (Misc.log2 (Nativeint.to_int n)) ->
+          (Iintop_imm(Imod, Nativeint.to_int n), [arg1])
       | _ -> (Iintop Imod, args)
       end
   (* Recognize float arithmetic with memory. *)
diff --git a/asmcomp/selectgen.ml b/asmcomp/selectgen.ml
index 50f949a..7daa239 100644
--- a/asmcomp/selectgen.ml
+++ b/asmcomp/selectgen.ml
@@ -201,6 +201,8 @@ method is_simple_expr = function
 
 method virtual is_immediate : int -> bool
 
+method virtual is_immediate_natint : nativeint -> bool
+
 (* Selection of addressing modes *)
 
 method virtual select_addressing :
@@ -238,11 +240,21 @@ method select_operation op args =
       if n = 1 lsl l
       then (Iintop_imm(Ilsl, l), [arg1])
       else self#select_arith_comm Imul args
+  | (Cmuli, [arg1; Cconst_natint n]) ->
+      let l = Misc.log2 (Nativeint.to_int n) in
+      if n = Nativeint.shift_left 1n l
+      then (Iintop_imm(Ilsl, l), [arg1])
+      else self#select_arith_comm Imul args
   | (Cmuli, [Cconst_int n; arg1]) ->
       let l = Misc.log2 n in
       if n = 1 lsl l
       then (Iintop_imm(Ilsl, l), [arg1])
       else self#select_arith_comm Imul args
+  | (Cmuli, [Cconst_natint n; arg1]) ->
+      let l = Misc.log2 (Nativeint.to_int n) in
+      if n = Nativeint.shift_left 1n l
+      then (Iintop_imm(Ilsl, l), [arg1])
+      else self#select_arith_comm Imul args
   | (Cmuli, _) -> self#select_arith_comm Imul args
   | (Cdivi, _) -> self#select_arith Idiv args
   | (Cmodi, _) -> self#select_arith_comm Imod args
@@ -270,38 +282,60 @@ method select_operation op args =
 method private select_arith_comm op = function
     [arg; Cconst_int n] when self#is_immediate n ->
       (Iintop_imm(op, n), [arg])
+  | [arg; Cconst_natint n] when self#is_immediate_natint n ->
+      (Iintop_imm(op, Nativeint.to_int n), [arg])
   | [arg; Cconst_pointer n] when self#is_immediate n ->
       (Iintop_imm(op, n), [arg])
+  | [arg; Cconst_natpointer n] when self#is_immediate_natint n ->
+      (Iintop_imm(op, Nativeint.to_int n), [arg])
   | [Cconst_int n; arg] when self#is_immediate n ->
       (Iintop_imm(op, n), [arg])
+  | [Cconst_natint n; arg] when self#is_immediate_natint n ->
+      (Iintop_imm(op, Nativeint.to_int n), [arg])
   | [Cconst_pointer n; arg] when self#is_immediate n ->
       (Iintop_imm(op, n), [arg])
+  | [Cconst_natpointer n; arg] when self#is_immediate_natint n ->
+      (Iintop_imm(op, Nativeint.to_int n), [arg])
   | args ->
       (Iintop op, args)
 
 method private select_arith op = function
     [arg; Cconst_int n] when self#is_immediate n ->
       (Iintop_imm(op, n), [arg])
+  | [arg; Cconst_natint n] when self#is_immediate_natint n ->
+      (Iintop_imm(op, Nativeint.to_int n), [arg])
   | [arg; Cconst_pointer n] when self#is_immediate n ->
       (Iintop_imm(op, n), [arg])
+  | [arg; Cconst_natpointer n] when self#is_immediate_natint n ->
+      (Iintop_imm(op, Nativeint.to_int n), [arg])
   | args ->
       (Iintop op, args)
 
 method private select_shift op = function
     [arg; Cconst_int n] when n >= 0 && n < Arch.size_int * 8 ->
       (Iintop_imm(op, n), [arg])
+  | [arg; Cconst_natint n] when n >= 0n && n < Nativeint.of_int (Arch.size_int * 8) ->
+      (Iintop_imm(op, Nativeint.to_int n), [arg])
   | args ->
       (Iintop op, args)
 
 method private select_arith_comp cmp = function
     [arg; Cconst_int n] when self#is_immediate n ->
       (Iintop_imm(Icomp cmp, n), [arg])
+  | [arg; Cconst_natint n] when self#is_immediate_natint n ->
+      (Iintop_imm(Icomp cmp, Nativeint.to_int n), [arg])
   | [arg; Cconst_pointer n] when self#is_immediate n ->
       (Iintop_imm(Icomp cmp, n), [arg])
+  | [arg; Cconst_natpointer n] when self#is_immediate_natint n ->
+      (Iintop_imm(Icomp cmp, Nativeint.to_int n), [arg])
   | [Cconst_int n; arg] when self#is_immediate n ->
       (Iintop_imm(Icomp(swap_intcomp cmp), n), [arg])
+  | [Cconst_natint n; arg] when self#is_immediate_natint n ->
+      (Iintop_imm(Icomp(swap_intcomp cmp), Nativeint.to_int n), [arg])
   | [Cconst_pointer n; arg] when self#is_immediate n ->
       (Iintop_imm(Icomp(swap_intcomp cmp), n), [arg])
+  | [Cconst_natpointer n; arg] when self#is_immediate_natint n ->
+      (Iintop_imm(Icomp(swap_intcomp cmp), Nativeint.to_int n), [arg])
   | args ->
       (Iintop(Icomp cmp), args)
 
@@ -310,12 +344,20 @@ method private select_arith_comp cmp = function
 method select_condition = function
     Cop(Ccmpi cmp, [arg1; Cconst_int n]) when self#is_immediate n ->
       (Iinttest_imm(Isigned cmp, n), arg1)
+  | Cop(Ccmpi cmp, [arg1; Cconst_natint n]) when self#is_immediate_natint n ->
+      (Iinttest_imm(Isigned cmp, Nativeint.to_int n), arg1)
   | Cop(Ccmpi cmp, [Cconst_int n; arg2]) when self#is_immediate n ->
       (Iinttest_imm(Isigned(swap_comparison cmp), n), arg2)
+  | Cop(Ccmpi cmp, [Cconst_natint n; arg2]) when self#is_immediate_natint n ->
+      (Iinttest_imm(Isigned(swap_comparison cmp), Nativeint.to_int n), arg2)
   | Cop(Ccmpi cmp, [arg1; Cconst_pointer n]) when self#is_immediate n ->
       (Iinttest_imm(Isigned cmp, n), arg1)
+  | Cop(Ccmpi cmp, [arg1; Cconst_natpointer n]) when self#is_immediate_natint n ->
+      (Iinttest_imm(Isigned cmp, Nativeint.to_int n), arg1)
   | Cop(Ccmpi cmp, [Cconst_pointer n; arg2]) when self#is_immediate n ->
       (Iinttest_imm(Isigned(swap_comparison cmp), n), arg2)
+  | Cop(Ccmpi cmp, [Cconst_natpointer n; arg2]) when self#is_immediate_natint n ->
+      (Iinttest_imm(Isigned(swap_comparison cmp), Nativeint.to_int n), arg2)
   | Cop(Ccmpi cmp, args) ->
       (Iinttest(Isigned cmp), Ctuple args)
   | Cop(Ccmpa cmp, [arg1; Cconst_pointer n]) when self#is_immediate n ->
diff --git a/asmcomp/selectgen.mli b/asmcomp/selectgen.mli
index 7c30f9f..8966ad1 100644
--- a/asmcomp/selectgen.mli
+++ b/asmcomp/selectgen.mli
@@ -23,6 +23,7 @@ class virtual selector_generic : object
   (* The following methods must or can be overridden by the processor
      description *)
   method virtual is_immediate : int -> bool
+  method virtual is_immediate_natint : nativeint -> bool
     (* Must be defined to indicate whether a constant is a suitable
        immediate operand to arithmetic instructions *)
   method virtual select_addressing :