diff -r c25b54be90ee Include/code.h
--- a/Include/code.h	Wed Mar 09 18:22:33 2011 -0500
+++ b/Include/code.h	Thu Mar 10 20:03:28 2011 -0500
@@ -99,7 +99,7 @@
                                         int lasti, PyAddrPair *bounds);
 #endif
 
-PyAPI_FUNC(PyObject*) PyCode_Optimize(PyObject *code, PyObject* consts,
+PyAPI_FUNC(PyObject*) PyCode_Optimize(PyObject *code, PyObject* consts, PyObject* constdict,
                                       PyObject *names, PyObject *lineno_obj);
 
 #ifdef __cplusplus
diff -r c25b54be90ee Python/compile.c
--- a/Python/compile.c	Wed Mar 09 18:22:33 2011 -0500
+++ b/Python/compile.c	Thu Mar 10 20:03:28 2011 -0500
@@ -892,8 +892,8 @@
     return 1;
 }
 
-static int
-compiler_add_o(struct compiler *c, PyObject *dict, PyObject *o)
+/* used in peephole.c */
+int _PyCode_AddObj(PyObject *dict, PyObject *o)
 {
     PyObject *t, *v;
     Py_ssize_t arg;
@@ -965,6 +965,12 @@
 }
 
 static int
+compiler_add_o(struct compiler *c, PyObject *dict, PyObject *o)
+{
+    return _PyCode_AddObj(dict, o);
+}
+
+static int
 compiler_addop_o(struct compiler *c, int opcode, PyObject *dict,
                      PyObject *o)
 {
@@ -3960,7 +3966,7 @@
     if (flags < 0)
         goto error;
 
-    bytecode = PyCode_Optimize(a->a_bytecode, consts, names, a->a_lnotab);
+    bytecode = PyCode_Optimize(a->a_bytecode, consts, c->u->u_consts, names, a->a_lnotab);
     if (!bytecode)
         goto error;
 
diff -r c25b54be90ee Python/peephole.c
--- a/Python/peephole.c	Wed Mar 09 18:22:33 2011 -0500
+++ b/Python/peephole.c	Thu Mar 10 20:03:28 2011 -0500
@@ -23,6 +23,27 @@
 #define ISBASICBLOCK(blocks, start, bytes) \
     (blocks[start]==blocks[start+bytes-1])
 
+/* from compile.c */
+extern int _PyCode_AddObj(PyObject *dict, PyObject *o);
+
+/* Helper to add a constant to constants list.
+   Reuses existing constant if possible, otherwise appends a new one. */
+static Py_ssize_t
+add_const(PyObject *consts, PyObject *dict, PyObject *newconst)
+{
+    Py_ssize_t idx, size;
+
+    idx = _PyCode_AddObj(dict, newconst);
+    size = PyList_GET_SIZE(consts);
+    /* newconst is already in dict or AddObj failed with -1? */
+    if (idx < size)
+	return idx;
+    assert(idx == size);
+    if (PyList_Append(consts, newconst))
+	return -1;
+    return size;
+}
+
 /* Replace LOAD_CONST c1. LOAD_CONST c2 ... LOAD_CONST cn BUILD_TUPLE n
    with    LOAD_CONST (c1, c2, ... cn).
    The consts table must still be in list form so that the
@@ -33,10 +54,10 @@
    test; for BUILD_SET it assembles a frozenset rather than a tuple.
 */
 static int
-tuple_of_constants(unsigned char *codestr, Py_ssize_t n, PyObject *consts)
+tuple_of_constants(unsigned char *codestr, Py_ssize_t n, PyObject *consts, PyObject* constdict)
 {
     PyObject *newconst, *constant;
-    Py_ssize_t i, arg, len_consts;
+    Py_ssize_t i, arg, len_consts, newidx;
 
     /* Pre-conditions */
     assert(PyList_CheckExact(consts));
@@ -69,7 +90,8 @@
     }
 
     /* Append folded constant onto consts */
-    if (PyList_Append(consts, newconst)) {
+    newidx = add_const(consts, constdict, newconst);
+    if (newidx < 0) {
         Py_DECREF(newconst);
         return 0;
     }
@@ -79,7 +101,7 @@
        add a new LOAD_CONST newconst on top of the BUILD_TUPLE n */
     memset(codestr, NOP, n*3);
     codestr[n*3] = LOAD_CONST;
-    SETARG(codestr, (n*3), len_consts);
+    SETARG(codestr, (n*3), newidx);
     return 1;
 }
 
@@ -94,10 +116,10 @@
    becoming large in the presence of code like:  (None,)*1000.
 */
 static int
-fold_binops_on_constants(unsigned char *codestr, PyObject *consts)
+fold_binops_on_constants(unsigned char *codestr, PyObject *consts, PyObject* constdict)
 {
     PyObject *newconst, *v, *w;
-    Py_ssize_t len_consts, size;
+    Py_ssize_t newidx, size;
     int opcode;
 
     /* Pre-conditions */
@@ -172,8 +194,8 @@
     }
 
     /* Append folded constant into consts table */
-    len_consts = PyList_GET_SIZE(consts);
-    if (PyList_Append(consts, newconst)) {
+    newidx = add_const(consts, constdict, newconst);
+    if (newidx < 0) {
         Py_DECREF(newconst);
         return 0;
     }
@@ -182,15 +204,15 @@
     /* Write NOP NOP NOP NOP LOAD_CONST newconst */
     memset(codestr, NOP, 4);
     codestr[4] = LOAD_CONST;
-    SETARG(codestr, 4, len_consts);
+    SETARG(codestr, 4, newidx);
     return 1;
 }
 
 static int
-fold_unaryops_on_constants(unsigned char *codestr, PyObject *consts)
+fold_unaryops_on_constants(unsigned char *codestr, PyObject *consts, PyObject* constdict)
 {
     PyObject *newconst=NULL, *v;
-    Py_ssize_t len_consts;
+    Py_ssize_t newidx;
     int opcode;
 
     /* Pre-conditions */
@@ -226,8 +248,8 @@
     }
 
     /* Append folded constant into consts table */
-    len_consts = PyList_GET_SIZE(consts);
-    if (PyList_Append(consts, newconst)) {
+    newidx = add_const(consts, constdict, newconst);
+    if (newidx < 0) {
         Py_DECREF(newconst);
         return 0;
     }
@@ -236,7 +258,7 @@
     /* Write NOP LOAD_CONST newconst */
     codestr[0] = NOP;
     codestr[1] = LOAD_CONST;
-    SETARG(codestr, 1, len_consts);
+    SETARG(codestr, 1, newidx);
     return 1;
 }
 
@@ -284,9 +306,9 @@
 /* Helper to replace LOAD_NAME None/True/False with LOAD_CONST
    Returns: 0 if no change, 1 if change, -1 if error */
 static int
-load_global(unsigned char *codestr, Py_ssize_t i, char *name, PyObject *consts)
+load_global(unsigned char *codestr, char *name, PyObject *consts, PyObject* constdict)
 {
-    Py_ssize_t j;
+    Py_ssize_t newidx;
     PyObject *obj;
     if (name == NULL)
         return 0;
@@ -298,17 +320,11 @@
         obj = Py_False;
     else
         return 0;
-    for (j = 0; j < PyList_GET_SIZE(consts); j++) {
-        if (PyList_GET_ITEM(consts, j) == obj)
-            break;
-    }
-    if (j == PyList_GET_SIZE(consts)) {
-        if (PyList_Append(consts, obj) < 0)
-            return -1;
-    }
-    assert(PyList_GET_ITEM(consts, j) == obj);
-    codestr[i] = LOAD_CONST;
-    SETARG(codestr, i, j);
+    newidx = add_const(consts, constdict, obj);
+    if (newidx < 0)
+	return -1;
+    codestr[0] = LOAD_CONST;
+    SETARG(codestr, 0, newidx);
     return 1;
 }
 
@@ -330,8 +346,8 @@
    a single pass.  Line numbering is adjusted accordingly. */
 
 PyObject *
-PyCode_Optimize(PyObject *code, PyObject* consts, PyObject *names,
-                PyObject *lineno_obj)
+PyCode_Optimize(PyObject *code, PyObject* consts, PyObject* constdict,
+	        PyObject *names, PyObject *lineno_obj)
 {
     Py_ssize_t i, j, codelen;
     int nops, h, adj;
@@ -427,7 +443,7 @@
             case LOAD_GLOBAL:
                 j = GETARG(codestr, i);
                 name = _PyUnicode_AsString(PyTuple_GET_ITEM(names, j));
-                h = load_global(codestr, i, name, consts);
+                h = load_global(&codestr[i], name, consts, constdict);
                 if (h < 0)
                     goto exitError;
                 else if (h == 0)
@@ -468,7 +484,7 @@
                       ISBASICBLOCK(blocks, h, 3*(j+2)) &&
                       (GETARG(codestr,i+3)==6 ||
                        GETARG(codestr,i+3)==7))) &&
-                    tuple_of_constants(&codestr[h], j, consts)) {
+                    tuple_of_constants(&codestr[h], j, consts, constdict)) {
                     assert(codestr[i] == LOAD_CONST);
                     cumlc = 1;
                     break;
@@ -506,7 +522,7 @@
             case BINARY_OR:
                 if (lastlc >= 2                  &&
                     ISBASICBLOCK(blocks, i-6, 7)  &&
-                    fold_binops_on_constants(&codestr[i-6], consts)) {
+                    fold_binops_on_constants(&codestr[i-6], consts, constdict)) {
                     i -= 2;
                     assert(codestr[i] == LOAD_CONST);
                     cumlc = 1;
@@ -520,7 +536,7 @@
             case UNARY_POSITIVE:
                 if (lastlc >= 1                  &&
                     ISBASICBLOCK(blocks, i-3, 4)  &&
-                    fold_unaryops_on_constants(&codestr[i-3], consts))                  {
+                    fold_unaryops_on_constants(&codestr[i-3], consts, constdict)) {
                     i -= 2;
                     assert(codestr[i] == LOAD_CONST);
                     cumlc = 1;