diff -r b7b805e05978 Python/peephole.c
--- a/Python/peephole.c	Wed Mar 09 19:01:04 2011 -0500
+++ b/Python/peephole.c	Thu Mar 10 20:07:34 2011 -0500
@@ -328,6 +328,128 @@
     return 1;
 }
 
+/* Fixup line numbers, remove NOPs and unused constants. */
+static Py_ssize_t
+fixup_code(unsigned char *codestr, Py_ssize_t codelen, PyObject* consts, PyObject *lineno_obj)
+{
+    Py_ssize_t i, j, tabsiz, pos, numconst;
+    int nops, adj, opcode;
+    int new_line, cum_orig_line, last_line;
+    unsigned char *lineno;
+    int *addrmap=NULL, *constuse=NULL;
+
+    /* Mapping to new jump targets after NOPs are removed. */
+    addrmap = (int *)PyMem_Malloc(codelen * sizeof(int));
+    if (addrmap == NULL)
+        goto exitError;
+
+    /* Table to record use and remapping of consts. */
+    numconst = PyList_GET_SIZE(consts);
+    constuse = (int *)PyMem_Malloc(numconst * sizeof(int));
+    if (constuse == NULL)
+        goto exitError;
+    memset(constuse, 0, numconst * sizeof(int));
+    /* First constant is a docstring. */
+    if (numconst > 0)
+        constuse[0] = 1;
+
+    /* Fixup linenotab and record const use. */
+    for (i=0, nops=0; i<codelen; i += CODESIZE(codestr[i])) {
+        addrmap[i] = i - nops;
+        if (codestr[i] == NOP)
+            nops++;
+        else if (codestr[i] == LOAD_CONST)
+	    constuse[GETARG(codestr, i)] = 1;
+    }
+
+    lineno = (unsigned char*)PyBytes_AS_STRING(lineno_obj);
+    tabsiz = PyBytes_GET_SIZE(lineno_obj);
+    cum_orig_line = 0;
+    last_line = 0;
+
+    for (i=0; i < tabsiz; i += 2) {
+        cum_orig_line += lineno[i];
+        new_line = addrmap[cum_orig_line];
+        assert (new_line - last_line < 255);
+        lineno[i] =((unsigned char)(new_line - last_line));
+        last_line = new_line;
+    }
+
+    /* Remove unused constants. */
+    for (i=0, j=0; i < numconst; i++) {
+	if (constuse[i] == 0)
+	    Py_DECREF(PyList_GET_ITEM(consts, i));
+	else {
+	    if (i != j)
+		PyList_GET_ITEM(consts, j) = PyList_GET_ITEM(consts, i);
+	    j++;
+	}
+    }
+
+    memset(&PyList_GET_ITEM(consts, j), 0, (numconst-j)*sizeof(PyObject*));
+    PyList_SetSlice(consts, j, numconst, NULL);
+
+    for (i=0, pos=0; i < numconst; i++) {
+	j = constuse[i];
+#ifndef NDEBUG
+	constuse[i] = j > 0 ? pos : -1;
+#else
+	constuse[i] = pos;
+#endif
+	pos += j;
+    }
+
+    /* Remove NOPs, fixup jump targets and remap consts. */
+    for (i=0, pos=0; i<codelen; ) {
+        opcode = codestr[i];
+        switch (opcode) {
+            case NOP:
+                i++;
+                continue;
+
+            case JUMP_ABSOLUTE:
+            case CONTINUE_LOOP:
+            case POP_JUMP_IF_FALSE:
+            case POP_JUMP_IF_TRUE:
+            case JUMP_IF_FALSE_OR_POP:
+            case JUMP_IF_TRUE_OR_POP:
+                j = addrmap[GETARG(codestr, i)];
+                SETARG(codestr, i, j);
+                break;
+
+            case FOR_ITER:
+            case JUMP_FORWARD:
+            case SETUP_LOOP:
+            case SETUP_EXCEPT:
+            case SETUP_FINALLY:
+            case SETUP_WITH:
+                j = addrmap[GETARG(codestr, i) + i + 3] - addrmap[i] - 3;
+                SETARG(codestr, i, j);
+                break;
+
+            case LOAD_CONST:
+                j = constuse[GETARG(codestr, i)];
+                SETARG(codestr, i, j);
+                break;
+        }
+        adj = CODESIZE(opcode);
+        while (adj--)
+            codestr[pos++] = codestr[i++];
+    }
+    assert(pos + nops == codelen);
+
+    PyMem_Free(addrmap);
+    PyMem_Free(constuse);
+    return pos;
+
+exitError:
+    if (addrmap != NULL)
+        PyMem_Free(addrmap);
+    if (constuse != NULL)
+        PyMem_Free(constuse);
+    return -1;
+}
+
 /* Perform basic peephole optimizations to components of a code object.
    The consts object should still be in list form to allow new constants
    to be appended.
@@ -350,12 +472,10 @@
 	        PyObject *names, PyObject *lineno_obj)
 {
     Py_ssize_t i, j, codelen;
-    int nops, h, adj;
-    int tgt, tgttgt, opcode;
+    int h, tgt, tgttgt, opcode;
     unsigned char *codestr = NULL;
     unsigned char *lineno;
-    int *addrmap = NULL;
-    int new_line, cum_orig_line, last_line, tabsiz;
+    int tabsiz;
     int cumlc=0, lastlc=0;      /* Count runs of consecutive LOAD_CONSTs */
     unsigned int *blocks = NULL;
     char *name;
@@ -392,11 +512,6 @@
     if (codestr[codelen-1] != RETURN_VALUE)
         goto exitUnchanged;
 
-    /* Mapping to new jump targets after NOPs are removed */
-    addrmap = (int *)PyMem_Malloc(codelen * sizeof(int));
-    if (addrmap == NULL)
-        goto exitError;
-
     blocks = markblocks(codestr, codelen);
     if (blocks == NULL)
         goto exitError;
@@ -645,58 +760,11 @@
         }
     }
 
-    /* Fixup linenotab */
-    for (i=0, nops=0 ; i<codelen ; i += CODESIZE(codestr[i])) {
-        addrmap[i] = i - nops;
-        if (codestr[i] == NOP)
-            nops++;
-    }
-    cum_orig_line = 0;
-    last_line = 0;
-    for (i=0 ; i < tabsiz ; i+=2) {
-        cum_orig_line += lineno[i];
-        new_line = addrmap[cum_orig_line];
-        assert (new_line - last_line < 255);
-        lineno[i] =((unsigned char)(new_line - last_line));
-        last_line = new_line;
-    }
+    codelen = fixup_code(codestr, codelen, consts, lineno_obj);
+    if (codelen < 0)
+	goto exitError;
 
-    /* Remove NOPs and fixup jump targets */
-    for (i=0, h=0 ; i<codelen ; ) {
-        opcode = codestr[i];
-        switch (opcode) {
-            case NOP:
-                i++;
-                continue;
-
-            case JUMP_ABSOLUTE:
-            case CONTINUE_LOOP:
-            case POP_JUMP_IF_FALSE:
-            case POP_JUMP_IF_TRUE:
-            case JUMP_IF_FALSE_OR_POP:
-            case JUMP_IF_TRUE_OR_POP:
-                j = addrmap[GETARG(codestr, i)];
-                SETARG(codestr, i, j);
-                break;
-
-            case FOR_ITER:
-            case JUMP_FORWARD:
-            case SETUP_LOOP:
-            case SETUP_EXCEPT:
-            case SETUP_FINALLY:
-            case SETUP_WITH:
-                j = addrmap[GETARG(codestr, i) + i + 3] - addrmap[i] - 3;
-                SETARG(codestr, i, j);
-                break;
-        }
-        adj = CODESIZE(opcode);
-        while (adj--)
-            codestr[h++] = codestr[i++];
-    }
-    assert(h + nops == codelen);
-
-    code = PyBytes_FromStringAndSize((char *)codestr, h);
-    PyMem_Free(addrmap);
+    code = PyBytes_FromStringAndSize((char *)codestr, codelen);
     PyMem_Free(codestr);
     PyMem_Free(blocks);
     return code;
@@ -707,8 +775,6 @@
  exitUnchanged:
     if (blocks != NULL)
         PyMem_Free(blocks);
-    if (addrmap != NULL)
-        PyMem_Free(addrmap);
     if (codestr != NULL)
         PyMem_Free(codestr);
     Py_XINCREF(code);