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svn+ssh://pythondev@svn.python.org/python/trunk ........ r61058 | neal.norwitz | 2008-02-25 02:45:37 +0100 (Mon, 25 Feb 2008) | 1 line Fix indentation ........ r61059 | brett.cannon | 2008-02-25 06:33:07 +0100 (Mon, 25 Feb 2008) | 2 lines Add minor markup for a string. ........ r61060 | brett.cannon | 2008-02-25 06:33:33 +0100 (Mon, 25 Feb 2008) | 2 lines Fix a minor typo in a docstring. ........
651 lines
18 KiB
C
651 lines
18 KiB
C
/* Peephole optimizations for bytecode compiler. */
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#include "Python.h"
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#include "Python-ast.h"
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#include "node.h"
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#include "pyarena.h"
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#include "ast.h"
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#include "code.h"
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#include "compile.h"
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#include "symtable.h"
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#include "opcode.h"
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#define GETARG(arr, i) ((int)((arr[i+2]<<8) + arr[i+1]))
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#define UNCONDITIONAL_JUMP(op) (op==JUMP_ABSOLUTE || op==JUMP_FORWARD)
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#define ABSOLUTE_JUMP(op) (op==JUMP_ABSOLUTE || op==CONTINUE_LOOP)
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#define GETJUMPTGT(arr, i) (GETARG(arr,i) + (ABSOLUTE_JUMP(arr[i]) ? 0 : i+3))
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#define SETARG(arr, i, val) arr[i+2] = val>>8; arr[i+1] = val & 255
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#define CODESIZE(op) (HAS_ARG(op) ? 3 : 1)
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#define ISBASICBLOCK(blocks, start, bytes) \
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(blocks[start]==blocks[start+bytes-1])
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/* Replace LOAD_CONST c1. LOAD_CONST c2 ... LOAD_CONST cn BUILD_TUPLE n
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with LOAD_CONST (c1, c2, ... cn).
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The consts table must still be in list form so that the
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new constant (c1, c2, ... cn) can be appended.
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Called with codestr pointing to the first LOAD_CONST.
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Bails out with no change if one or more of the LOAD_CONSTs is missing.
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Also works for BUILD_LIST when followed by an "in" or "not in" test.
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*/
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static int
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tuple_of_constants(unsigned char *codestr, int n, PyObject *consts)
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{
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PyObject *newconst, *constant;
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Py_ssize_t i, arg, len_consts;
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/* Pre-conditions */
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assert(PyList_CheckExact(consts));
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assert(codestr[n*3] == BUILD_TUPLE || codestr[n*3] == BUILD_LIST);
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assert(GETARG(codestr, (n*3)) == n);
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for (i=0 ; i<n ; i++)
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assert(codestr[i*3] == LOAD_CONST);
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/* Buildup new tuple of constants */
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newconst = PyTuple_New(n);
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if (newconst == NULL)
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return 0;
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len_consts = PyList_GET_SIZE(consts);
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for (i=0 ; i<n ; i++) {
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arg = GETARG(codestr, (i*3));
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assert(arg < len_consts);
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constant = PyList_GET_ITEM(consts, arg);
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Py_INCREF(constant);
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PyTuple_SET_ITEM(newconst, i, constant);
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}
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/* Append folded constant onto consts */
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if (PyList_Append(consts, newconst)) {
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Py_DECREF(newconst);
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return 0;
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}
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Py_DECREF(newconst);
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/* Write NOPs over old LOAD_CONSTS and
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add a new LOAD_CONST newconst on top of the BUILD_TUPLE n */
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memset(codestr, NOP, n*3);
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codestr[n*3] = LOAD_CONST;
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SETARG(codestr, (n*3), len_consts);
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return 1;
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}
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/* Replace LOAD_CONST c1. LOAD_CONST c2 BINOP
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with LOAD_CONST binop(c1,c2)
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The consts table must still be in list form so that the
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new constant can be appended.
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Called with codestr pointing to the first LOAD_CONST.
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Abandons the transformation if the folding fails (i.e. 1+'a').
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If the new constant is a sequence, only folds when the size
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is below a threshold value. That keeps pyc files from
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becoming large in the presence of code like: (None,)*1000.
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*/
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static int
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fold_binops_on_constants(unsigned char *codestr, PyObject *consts)
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{
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PyObject *newconst, *v, *w;
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Py_ssize_t len_consts, size;
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int opcode;
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/* Pre-conditions */
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assert(PyList_CheckExact(consts));
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assert(codestr[0] == LOAD_CONST);
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assert(codestr[3] == LOAD_CONST);
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/* Create new constant */
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v = PyList_GET_ITEM(consts, GETARG(codestr, 0));
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w = PyList_GET_ITEM(consts, GETARG(codestr, 3));
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opcode = codestr[6];
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switch (opcode) {
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case BINARY_POWER:
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newconst = PyNumber_Power(v, w, Py_None);
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break;
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case BINARY_MULTIPLY:
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newconst = PyNumber_Multiply(v, w);
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break;
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case BINARY_TRUE_DIVIDE:
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newconst = PyNumber_TrueDivide(v, w);
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break;
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case BINARY_FLOOR_DIVIDE:
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newconst = PyNumber_FloorDivide(v, w);
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break;
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case BINARY_MODULO:
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newconst = PyNumber_Remainder(v, w);
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break;
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case BINARY_ADD:
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newconst = PyNumber_Add(v, w);
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break;
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case BINARY_SUBTRACT:
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newconst = PyNumber_Subtract(v, w);
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break;
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case BINARY_SUBSCR:
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newconst = PyObject_GetItem(v, w);
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break;
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case BINARY_LSHIFT:
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newconst = PyNumber_Lshift(v, w);
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break;
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case BINARY_RSHIFT:
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newconst = PyNumber_Rshift(v, w);
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break;
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case BINARY_AND:
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newconst = PyNumber_And(v, w);
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break;
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case BINARY_XOR:
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newconst = PyNumber_Xor(v, w);
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break;
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case BINARY_OR:
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newconst = PyNumber_Or(v, w);
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break;
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default:
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/* Called with an unknown opcode */
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PyErr_Format(PyExc_SystemError,
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"unexpected binary operation %d on a constant",
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opcode);
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return 0;
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}
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if (newconst == NULL) {
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PyErr_Clear();
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return 0;
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}
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size = PyObject_Size(newconst);
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if (size == -1)
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PyErr_Clear();
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else if (size > 20) {
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Py_DECREF(newconst);
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return 0;
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}
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/* Append folded constant into consts table */
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len_consts = PyList_GET_SIZE(consts);
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if (PyList_Append(consts, newconst)) {
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Py_DECREF(newconst);
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return 0;
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}
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Py_DECREF(newconst);
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/* Write NOP NOP NOP NOP LOAD_CONST newconst */
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memset(codestr, NOP, 4);
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codestr[4] = LOAD_CONST;
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SETARG(codestr, 4, len_consts);
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return 1;
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}
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static int
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fold_unaryops_on_constants(unsigned char *codestr, PyObject *consts)
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{
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PyObject *newconst=NULL, *v;
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Py_ssize_t len_consts;
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int opcode;
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/* Pre-conditions */
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assert(PyList_CheckExact(consts));
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assert(codestr[0] == LOAD_CONST);
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/* Create new constant */
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v = PyList_GET_ITEM(consts, GETARG(codestr, 0));
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opcode = codestr[3];
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switch (opcode) {
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case UNARY_NEGATIVE:
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/* Preserve the sign of -0.0 */
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if (PyObject_IsTrue(v) == 1)
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newconst = PyNumber_Negative(v);
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break;
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case UNARY_INVERT:
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newconst = PyNumber_Invert(v);
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break;
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default:
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/* Called with an unknown opcode */
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PyErr_Format(PyExc_SystemError,
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"unexpected unary operation %d on a constant",
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opcode);
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return 0;
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}
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if (newconst == NULL) {
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PyErr_Clear();
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return 0;
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}
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/* Append folded constant into consts table */
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len_consts = PyList_GET_SIZE(consts);
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if (PyList_Append(consts, newconst)) {
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Py_DECREF(newconst);
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return 0;
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}
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Py_DECREF(newconst);
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/* Write NOP LOAD_CONST newconst */
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codestr[0] = NOP;
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codestr[1] = LOAD_CONST;
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SETARG(codestr, 1, len_consts);
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return 1;
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}
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static unsigned int *
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markblocks(unsigned char *code, int len)
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{
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unsigned int *blocks = (unsigned int *)PyMem_Malloc(len*sizeof(int));
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int i,j, opcode, blockcnt = 0;
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if (blocks == NULL) {
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PyErr_NoMemory();
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return NULL;
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}
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memset(blocks, 0, len*sizeof(int));
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/* Mark labels in the first pass */
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for (i=0 ; i<len ; i+=CODESIZE(opcode)) {
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opcode = code[i];
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switch (opcode) {
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case FOR_ITER:
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case JUMP_FORWARD:
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case JUMP_IF_FALSE:
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case JUMP_IF_TRUE:
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case JUMP_ABSOLUTE:
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case CONTINUE_LOOP:
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case SETUP_LOOP:
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case SETUP_EXCEPT:
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case SETUP_FINALLY:
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j = GETJUMPTGT(code, i);
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blocks[j] = 1;
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break;
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}
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}
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/* Build block numbers in the second pass */
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for (i=0 ; i<len ; i++) {
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blockcnt += blocks[i]; /* increment blockcnt over labels */
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blocks[i] = blockcnt;
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}
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return blocks;
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}
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/* Helper to replace LOAD_NAME None/True/False with LOAD_CONST
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Returns: 0 if no change, 1 if change, -1 if error */
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static int
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load_global(unsigned char *codestr, Py_ssize_t i, char *name, PyObject *consts)
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{
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Py_ssize_t j;
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PyObject *obj;
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if (name == NULL)
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return 0;
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if (strcmp(name, "None") == 0)
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obj = Py_None;
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else if (strcmp(name, "True") == 0)
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obj = Py_True;
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else if (strcmp(name, "False") == 0)
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obj = Py_False;
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else
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return 0;
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for (j = 0; j < PyList_GET_SIZE(consts); j++) {
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if (PyList_GET_ITEM(consts, j) == obj)
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break;
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}
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if (j == PyList_GET_SIZE(consts)) {
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if (PyList_Append(consts, obj) < 0)
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return -1;
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}
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assert(PyList_GET_ITEM(consts, j) == obj);
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codestr[i] = LOAD_CONST;
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SETARG(codestr, i, j);
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return 1;
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}
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/* Perform basic peephole optimizations to components of a code object.
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The consts object should still be in list form to allow new constants
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to be appended.
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To keep the optimizer simple, it bails out (does nothing) for code that
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has a length over 32,700, and does not calculate extended arguments.
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That allows us to avoid overflow and sign issues. Likewise, it bails when
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the lineno table has complex encoding for gaps >= 255. EXTENDED_ARG can
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appear before MAKE_FUNCTION; in this case both opcodes are skipped.
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EXTENDED_ARG preceding any other opcode causes the optimizer to bail.
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Optimizations are restricted to simple transformations occuring within a
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single basic block. All transformations keep the code size the same or
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smaller. For those that reduce size, the gaps are initially filled with
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NOPs. Later those NOPs are removed and the jump addresses retargeted in
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a single pass. Line numbering is adjusted accordingly. */
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PyObject *
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PyCode_Optimize(PyObject *code, PyObject* consts, PyObject *names,
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PyObject *lineno_obj)
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{
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Py_ssize_t i, j, codelen;
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int nops, h, adj;
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int tgt, tgttgt, opcode;
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unsigned char *codestr = NULL;
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unsigned char *lineno;
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int *addrmap = NULL;
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int new_line, cum_orig_line, last_line, tabsiz;
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int cumlc=0, lastlc=0; /* Count runs of consecutive LOAD_CONSTs */
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unsigned int *blocks = NULL;
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char *name;
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/* Bail out if an exception is set */
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if (PyErr_Occurred())
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goto exitUnchanged;
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/* Bypass optimization when the lineno table is too complex */
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assert(PyString_Check(lineno_obj));
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lineno = (unsigned char*)PyString_AS_STRING(lineno_obj);
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tabsiz = PyString_GET_SIZE(lineno_obj);
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if (memchr(lineno, 255, tabsiz) != NULL)
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goto exitUnchanged;
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/* Avoid situations where jump retargeting could overflow */
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assert(PyString_Check(code));
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codelen = PyString_GET_SIZE(code);
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if (codelen > 32700)
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goto exitUnchanged;
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/* Make a modifiable copy of the code string */
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codestr = (unsigned char *)PyMem_Malloc(codelen);
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if (codestr == NULL)
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goto exitUnchanged;
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codestr = (unsigned char *)memcpy(codestr,
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PyString_AS_STRING(code), codelen);
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/* Verify that RETURN_VALUE terminates the codestring. This allows
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the various transformation patterns to look ahead several
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instructions without additional checks to make sure they are not
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looking beyond the end of the code string.
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*/
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if (codestr[codelen-1] != RETURN_VALUE)
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goto exitUnchanged;
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/* Mapping to new jump targets after NOPs are removed */
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addrmap = (int *)PyMem_Malloc(codelen * sizeof(int));
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if (addrmap == NULL)
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goto exitUnchanged;
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blocks = markblocks(codestr, codelen);
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if (blocks == NULL)
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goto exitUnchanged;
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assert(PyList_Check(consts));
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for (i=0 ; i<codelen ; i += CODESIZE(codestr[i])) {
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opcode = codestr[i];
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lastlc = cumlc;
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cumlc = 0;
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switch (opcode) {
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/* Replace UNARY_NOT JUMP_IF_FALSE POP_TOP with
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with JUMP_IF_TRUE POP_TOP */
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case UNARY_NOT:
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if (codestr[i+1] != JUMP_IF_FALSE ||
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codestr[i+4] != POP_TOP ||
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!ISBASICBLOCK(blocks,i,5))
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continue;
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tgt = GETJUMPTGT(codestr, (i+1));
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if (codestr[tgt] != POP_TOP)
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continue;
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j = GETARG(codestr, i+1) + 1;
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codestr[i] = JUMP_IF_TRUE;
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SETARG(codestr, i, j);
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codestr[i+3] = POP_TOP;
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codestr[i+4] = NOP;
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break;
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/* not a is b --> a is not b
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not a in b --> a not in b
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not a is not b --> a is b
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not a not in b --> a in b
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*/
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case COMPARE_OP:
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j = GETARG(codestr, i);
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if (j < 6 || j > 9 ||
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codestr[i+3] != UNARY_NOT ||
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!ISBASICBLOCK(blocks,i,4))
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continue;
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SETARG(codestr, i, (j^1));
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codestr[i+3] = NOP;
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break;
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/* Replace LOAD_GLOBAL/LOAD_NAME None/True/False
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with LOAD_CONST None/True/False */
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case LOAD_NAME:
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case LOAD_GLOBAL:
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j = GETARG(codestr, i);
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name = PyUnicode_AsString(PyTuple_GET_ITEM(names, j));
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h = load_global(codestr, i, name, consts);
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if (h < 0)
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goto exitUnchanged;
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else if (h == 0)
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continue;
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cumlc = lastlc + 1;
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break;
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/* Skip over LOAD_CONST trueconst
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JUMP_IF_FALSE xx POP_TOP */
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case LOAD_CONST:
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cumlc = lastlc + 1;
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j = GETARG(codestr, i);
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if (codestr[i+3] != JUMP_IF_FALSE ||
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codestr[i+6] != POP_TOP ||
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!ISBASICBLOCK(blocks,i,7) ||
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!PyObject_IsTrue(PyList_GET_ITEM(consts, j)))
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continue;
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memset(codestr+i, NOP, 7);
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cumlc = 0;
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break;
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/* Try to fold tuples of constants (includes a case for lists
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which are only used for "in" and "not in" tests).
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Skip over BUILD_SEQN 1 UNPACK_SEQN 1.
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Replace BUILD_SEQN 2 UNPACK_SEQN 2 with ROT2.
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Replace BUILD_SEQN 3 UNPACK_SEQN 3 with ROT3 ROT2. */
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case BUILD_TUPLE:
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case BUILD_LIST:
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j = GETARG(codestr, i);
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h = i - 3 * j;
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if (h >= 0 &&
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j <= lastlc &&
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((opcode == BUILD_TUPLE &&
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ISBASICBLOCK(blocks, h, 3*(j+1))) ||
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(opcode == BUILD_LIST &&
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codestr[i+3]==COMPARE_OP &&
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ISBASICBLOCK(blocks, h, 3*(j+2)) &&
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(GETARG(codestr,i+3)==6 ||
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GETARG(codestr,i+3)==7))) &&
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tuple_of_constants(&codestr[h], j, consts)) {
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assert(codestr[i] == LOAD_CONST);
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cumlc = 1;
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break;
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}
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if (codestr[i+3] != UNPACK_SEQUENCE ||
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!ISBASICBLOCK(blocks,i,6) ||
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j != GETARG(codestr, i+3))
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continue;
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if (j == 1) {
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memset(codestr+i, NOP, 6);
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} else if (j == 2) {
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codestr[i] = ROT_TWO;
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memset(codestr+i+1, NOP, 5);
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} else if (j == 3) {
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codestr[i] = ROT_THREE;
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codestr[i+1] = ROT_TWO;
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memset(codestr+i+2, NOP, 4);
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}
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break;
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/* Fold binary ops on constants.
|
|
LOAD_CONST c1 LOAD_CONST c2 BINOP --> LOAD_CONST binop(c1,c2) */
|
|
case BINARY_POWER:
|
|
case BINARY_MULTIPLY:
|
|
case BINARY_TRUE_DIVIDE:
|
|
case BINARY_FLOOR_DIVIDE:
|
|
case BINARY_MODULO:
|
|
case BINARY_ADD:
|
|
case BINARY_SUBTRACT:
|
|
case BINARY_SUBSCR:
|
|
case BINARY_LSHIFT:
|
|
case BINARY_RSHIFT:
|
|
case BINARY_AND:
|
|
case BINARY_XOR:
|
|
case BINARY_OR:
|
|
if (lastlc >= 2 &&
|
|
ISBASICBLOCK(blocks, i-6, 7) &&
|
|
fold_binops_on_constants(&codestr[i-6], consts)) {
|
|
i -= 2;
|
|
assert(codestr[i] == LOAD_CONST);
|
|
cumlc = 1;
|
|
}
|
|
break;
|
|
|
|
/* Fold unary ops on constants.
|
|
LOAD_CONST c1 UNARY_OP --> LOAD_CONST unary_op(c) */
|
|
case UNARY_NEGATIVE:
|
|
case UNARY_INVERT:
|
|
if (lastlc >= 1 &&
|
|
ISBASICBLOCK(blocks, i-3, 4) &&
|
|
fold_unaryops_on_constants(&codestr[i-3], consts)) {
|
|
i -= 2;
|
|
assert(codestr[i] == LOAD_CONST);
|
|
cumlc = 1;
|
|
}
|
|
break;
|
|
|
|
/* Simplify conditional jump to conditional jump where the
|
|
result of the first test implies the success of a similar
|
|
test or the failure of the opposite test.
|
|
Arises in code like:
|
|
"if a and b:"
|
|
"if a or b:"
|
|
"a and b or c"
|
|
"(a and b) and c"
|
|
x:JUMP_IF_FALSE y y:JUMP_IF_FALSE z --> x:JUMP_IF_FALSE z
|
|
x:JUMP_IF_FALSE y y:JUMP_IF_TRUE z --> x:JUMP_IF_FALSE y+3
|
|
where y+3 is the instruction following the second test.
|
|
*/
|
|
case JUMP_IF_FALSE:
|
|
case JUMP_IF_TRUE:
|
|
tgt = GETJUMPTGT(codestr, i);
|
|
j = codestr[tgt];
|
|
if (j == JUMP_IF_FALSE || j == JUMP_IF_TRUE) {
|
|
if (j == opcode) {
|
|
tgttgt = GETJUMPTGT(codestr, tgt) - i - 3;
|
|
SETARG(codestr, i, tgttgt);
|
|
} else {
|
|
tgt -= i;
|
|
SETARG(codestr, i, tgt);
|
|
}
|
|
break;
|
|
}
|
|
/* Intentional fallthrough */
|
|
|
|
/* Replace jumps to unconditional jumps */
|
|
case FOR_ITER:
|
|
case JUMP_FORWARD:
|
|
case JUMP_ABSOLUTE:
|
|
case CONTINUE_LOOP:
|
|
case SETUP_LOOP:
|
|
case SETUP_EXCEPT:
|
|
case SETUP_FINALLY:
|
|
tgt = GETJUMPTGT(codestr, i);
|
|
/* Replace JUMP_* to a RETURN into just a RETURN */
|
|
if (UNCONDITIONAL_JUMP(opcode) &&
|
|
codestr[tgt] == RETURN_VALUE) {
|
|
codestr[i] = RETURN_VALUE;
|
|
memset(codestr+i+1, NOP, 2);
|
|
continue;
|
|
}
|
|
if (!UNCONDITIONAL_JUMP(codestr[tgt]))
|
|
continue;
|
|
tgttgt = GETJUMPTGT(codestr, tgt);
|
|
if (opcode == JUMP_FORWARD) /* JMP_ABS can go backwards */
|
|
opcode = JUMP_ABSOLUTE;
|
|
if (!ABSOLUTE_JUMP(opcode))
|
|
tgttgt -= i + 3; /* Calc relative jump addr */
|
|
if (tgttgt < 0) /* No backward relative jumps */
|
|
continue;
|
|
codestr[i] = opcode;
|
|
SETARG(codestr, i, tgttgt);
|
|
break;
|
|
|
|
case EXTENDED_ARG:
|
|
if (codestr[i+3] != MAKE_FUNCTION)
|
|
goto exitUnchanged;
|
|
/* don't visit MAKE_FUNCTION as GETARG will be wrong */
|
|
i += 3;
|
|
break;
|
|
|
|
/* Replace RETURN LOAD_CONST None RETURN with just RETURN */
|
|
/* Remove unreachable JUMPs after RETURN */
|
|
case RETURN_VALUE:
|
|
if (i+4 >= codelen)
|
|
continue;
|
|
if (codestr[i+4] == RETURN_VALUE &&
|
|
ISBASICBLOCK(blocks,i,5))
|
|
memset(codestr+i+1, NOP, 4);
|
|
else if (UNCONDITIONAL_JUMP(codestr[i+1]) &&
|
|
ISBASICBLOCK(blocks,i,4))
|
|
memset(codestr+i+1, NOP, 3);
|
|
break;
|
|
}
|
|
}
|
|
|
|
/* 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;
|
|
}
|
|
|
|
/* 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:
|
|
j = addrmap[GETARG(codestr, i)];
|
|
SETARG(codestr, i, j);
|
|
break;
|
|
|
|
case FOR_ITER:
|
|
case JUMP_FORWARD:
|
|
case JUMP_IF_FALSE:
|
|
case JUMP_IF_TRUE:
|
|
case SETUP_LOOP:
|
|
case SETUP_EXCEPT:
|
|
case SETUP_FINALLY:
|
|
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 = PyString_FromStringAndSize((char *)codestr, h);
|
|
PyMem_Free(addrmap);
|
|
PyMem_Free(codestr);
|
|
PyMem_Free(blocks);
|
|
return code;
|
|
|
|
exitUnchanged:
|
|
if (blocks != NULL)
|
|
PyMem_Free(blocks);
|
|
if (addrmap != NULL)
|
|
PyMem_Free(addrmap);
|
|
if (codestr != NULL)
|
|
PyMem_Free(codestr);
|
|
Py_INCREF(code);
|
|
return code;
|
|
}
|