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 20:00:02 2011 -0500
@@ -23,6 +23,49 @@
 #define ISBASICBLOCK(blocks, start, bytes) \
     (blocks[start]==blocks[start+bytes-1])
 
+static int
+number_as_complex(PyObject *num, Py_complex *z)
+{
+    if (PyFloat_Check(num)) {
+	z->real = PyFloat_AS_DOUBLE(num);
+	z->imag = 0;
+	return 1;
+    }
+    if (PyComplex_Check(num)) {
+	*z = PyComplex_AsCComplex(num);
+	return 1;
+    }
+    return 0;
+}
+
+/* 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 *newconst)
+{
+    Py_ssize_t i, size;
+    PyObject *item;
+    Py_complex z1, z2;
+
+    size = PyList_GET_SIZE(consts);
+    for (i = 0; i < size; i++) {
+	item = PyList_GET_ITEM(consts, i);
+	if (Py_TYPE(item) == Py_TYPE(newconst) &&
+	    PyObject_RichCompareBool(item, newconst, Py_EQ) == 1) {
+	    /* Special handling for -0.0 in float in complex. */
+            if (number_as_complex(item, &z1) &&
+		number_as_complex(newconst, &z2) &&
+		(copysign(1.0, z1.real) != copysign(1.0, z2.real) ||
+		 copysign(1.0, z1.imag) != copysign(1.0, z2.imag)))
+		continue;
+            return i;
+	}
+    }
+    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
@@ -36,7 +79,7 @@
 tuple_of_constants(unsigned char *codestr, Py_ssize_t n, PyObject *consts)
 {
     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 +112,8 @@
     }
 
     /* Append folded constant onto consts */
-    if (PyList_Append(consts, newconst)) {
+    newidx = add_const(consts, newconst);
+    if (newidx < 0) {
         Py_DECREF(newconst);
         return 0;
     }
@@ -79,7 +123,7 @@
        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;
 }
 
@@ -97,7 +141,7 @@
 fold_binops_on_constants(unsigned char *codestr, PyObject *consts)
 {
     PyObject *newconst, *v, *w;
-    Py_ssize_t len_consts, size;
+    Py_ssize_t newidx, size;
     int opcode;
 
     /* Pre-conditions */
@@ -172,8 +216,8 @@
     }
 
     /* Append folded constant into consts table */
-    len_consts = PyList_GET_SIZE(consts);
-    if (PyList_Append(consts, newconst)) {
+    newidx = add_const(consts, newconst);
+    if (newidx < 0) {
         Py_DECREF(newconst);
         return 0;
     }
@@ -182,7 +226,7 @@
     /* 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;
 }
 
@@ -190,7 +234,7 @@
 fold_unaryops_on_constants(unsigned char *codestr, PyObject *consts)
 {
     PyObject *newconst=NULL, *v;
-    Py_ssize_t len_consts;
+    Py_ssize_t newidx;
     int opcode;
 
     /* Pre-conditions */
@@ -226,8 +270,8 @@
     }
 
     /* Append folded constant into consts table */
-    len_consts = PyList_GET_SIZE(consts);
-    if (PyList_Append(consts, newconst)) {
+    newidx = add_const(consts, newconst);
+    if (newidx < 0) {
         Py_DECREF(newconst);
         return 0;
     }
@@ -236,7 +280,7 @@
     /* 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 +328,9 @@
 /* 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)
 {
-    Py_ssize_t j;
+    Py_ssize_t newidx;
     PyObject *obj;
     if (name == NULL)
         return 0;
@@ -298,17 +342,11 @@
         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, obj);
+    if (newidx < 0)
+	return -1;
+    codestr[0] = LOAD_CONST;
+    SETARG(codestr, 0, newidx);
     return 1;
 }
 
@@ -427,7 +465,7 @@
             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);
                 if (h < 0)
                     goto exitError;
                 else if (h == 0)
@@ -520,7 +558,7 @@
             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)) {
                     i -= 2;
                     assert(codestr[i] == LOAD_CONST);
                     cumlc = 1;