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path: root/Python/pymath.c

	Commit message (Collapse)	Author	Age	Files	Lines
*	bpo-45440: Remove pymath.c fallbacks (GH-28977)	Victor Stinner	2021-10-15	1	-48/+0
| | | | | | | |	Remove fallbacks for missing round(), copysign() and hypot() in Python/pymath.c. Python now requires these functions to build. These fallbacks were needed on Visual Studio 2012 and older. They are no longer needed since Visual Stuido 2013. Python is now built with Visual Studio 2017 or newer since Python 3.6.
*	bpo-45440: Require math.h isinf() to build (GH-28894)	Victor Stinner	2021-10-13	1	-13/+0
| | | | | | | | | | | | | | |	Building Python now requires a C99 <math.h> header file providing isinf(), isnan() and isfinite() functions. Remove the Py_FORCE_DOUBLE() macro. It was used by the Py_IS_INFINITY() macro. Changes: * Remove Py_IS_NAN(), Py_IS_INFINITY() and Py_IS_FINITE() in PC/pyconfig.h. * Remove the _Py_force_double() function. * configure no longer checks if math.h defines isinf(), isnan() and isfinite().
*	bpo-45412: Move _Py_SET_53BIT_PRECISION_START to pycore_pymath.h (GH-28882)	Victor Stinner	2021-10-11	1	-5/+4
| | | | | | | | | | | | | | |	Move the following macros , to pycore_pymath.h (internal C API): * _Py_SET_53BIT_PRECISION_HEADER * _Py_SET_53BIT_PRECISION_START * _Py_SET_53BIT_PRECISION_END PEP 7: add braces to if and "do { ... } while (0)" in these macros. Move also _Py_get_387controlword() and _Py_set_387controlword() definitions to pycore_pymath.h. These functions are no longer exported. pystrtod.c now includes pycore_pymath.h.
*	bpo-29782: Consolidate _Py_Bit_Length() (GH-20739)	Niklas Fiekas	2020-06-15	1	-15/+0
| | | | | | | | | |	In GH-2866, _Py_Bit_Length() was added to pymath.h for lack of a better location. GH-20518 added a more appropriate header file for bit utilities. It also shows how to properly use intrinsics. This allows reconsidering bpo-29782. * Move the function to the new header. * Changed return type to match __builtin_clzl() and reviewed usage. * Use intrinsics where available. * Pick a fallback implementation suitable for inlining.
*	bpo-31031: Unify duplicate bits_in_digit and bit_length (GH-2866)	Niklas Fiekas	2020-01-16	1	-0/+15
| | |	Add _Py_bit_length() to unify duplicate bits_in_digit() and bit_length().
*	bpo-35214: Add _Py_ prefix to MEMORY_SANITIZER def. (GH-10503)	Gregory P. Smith	2018-11-13	1	-1/+1
| | | |	Rename our new MEMORY_SANITIZER define to _Py_MEMORY_SANITIZER. Project based C Preprocessor namespacing at its finest. :P
*	bpo-35214: Initial clang MemorySanitizer support (GH-10479)	Gregory P. Smith	2018-11-12	1	-1/+3
| | | | | | | | | |	Adds configure flags for msan and ubsan builds to make it easier to enable. These also encode the detail that address sanitizer and memory sanitizer should disable pymalloc. Define MEMORY_SANITIZER when appropriate at build time and adds workarounds to existing code to mark things as initialized where the sanitizer is otherwise unable to determine that. This lets our build succeed under the memory sanitizer. not all tests pass without sanitizer failures yet but we're in pretty good shape after this.
*	Issue 24366: Indent code (thanks to li4ick for reporting).	Yury Selivanov	2015-06-02	1	-1/+1
|
*	Recorded merge of revisions 81029 via svnmerge from	Antoine Pitrou	2010-05-09	1	-24/+24
| | | | | | | | | |	svn+ssh://pythondev@svn.python.org/python/trunk ........ r81029 | antoine.pitrou | 2010-05-09 16:46:46 +0200 (dim., 09 mai 2010) | 3 lines Untabify C files. Will watch buildbots. ........
*	Merged revisions 76978 via svnmerge from	Mark Dickinson	2009-12-21	1	-199/+0
| | | | | | | | | | |	svn+ssh://pythondev@svn.python.org/python/trunk ........ r76978 | mark.dickinson | 2009-12-21 15:22:00 +0000 (Mon, 21 Dec 2009) | 3 lines Issue #7518: Move substitute definitions of C99 math functions from pymath.c to Modules/_math.c. ........
*	The SSE2 detection and enabling could potentially cause	Mark Dickinson	2009-04-18	1	-5/+1
| | | | | | | |	problems for binary distributions of Python in situations where the build machine has SSE2 but the target machine does not. Therefore, don't enable SSE2 instructions automatically on x86.
*	Merged revisions 71705 via svnmerge from	Mark Dickinson	2009-04-18	1	-1/+1
| | | | | | | | | |	svn+ssh://pythondev@svn.python.org/python/trunk ........ r71705 | mark.dickinson | 2009-04-18 15:13:43 +0100 (Sat, 18 Apr 2009) | 2 lines copysign shouldn't be declared as static in pymath.c ........
*	Add check for C99 round function to configure, and define	Mark Dickinson	2009-04-18	1	-0/+13
| | | |	a fallback function if round doesn't exist.
*	Issue #1580: use short float repr where possible.	Mark Dickinson	2009-04-16	1	-0/+22
| | | | | | | | | | | | | | |	- incorporate and adapt David Gay's dtoa and strtod into the Python core - on platforms where we can use Gay's code (almost all!), repr(float) is based on the shortest sequence of decimal digits that rounds correctly. - add sys.float_repr_style attribute to indicate whether we're using Gay's code or not - add autoconf magic to detect and enable SSE2 instructions on x86/gcc - slight change to repr and str: repr switches to exponential notation at 1e16 instead of 1e17, str switches at 1e11 instead of 1e12
*	Merged revisions 69459 via svnmerge from	Mark Dickinson	2009-02-09	1	-0/+13
| | | | | | | | | | |	svn+ssh://pythondev@svn.python.org/python/trunk ........ r69459 | mark.dickinson | 2009-02-09 14:18:43 +0000 (Mon, 09 Feb 2009) | 3 lines Issue #4575: fix Py_IS_INFINITY macro to work correctly on x87 FPUs. It now forces its argument to double before testing for infinity. ........
*	Merged revisions 66552-66553 via svnmerge from	Andrew MacIntyre	2008-09-22	1	-0/+2
| | | | | | | | | | | | | | | | | | | |	svn+ssh://pythondev@svn.python.org/python/trunk ........ r66552 | andrew.macintyre | 2008-09-23 00:10:54 +1000 (Tue, 23 Sep 2008) | 5 lines should use macro'ed symbols not direct Part of source_os2emx.patch in issue 3868 Reviewed by Amaury Forgeot d'Arc ........ r66553 | andrew.macintyre | 2008-09-23 00:11:41 +1000 (Tue, 23 Sep 2008) | 5 lines any platform without HAVE_LOG1P should have DBL_EPSILON in <float.h> Part of source_os2emx.patch in issue 3868 Reviewed by Amaury Forgeot d'Arc ........
*	Merged revisions 62380,62382-62383 via svnmerge from	Christian Heimes	2008-04-19	1	-0/+232
	svn+ssh://pythondev@svn.python.org/python/trunk ........ r62380 | christian.heimes | 2008-04-19 01:13:07 +0200 (Sat, 19 Apr 2008) | 3 lines I finally got the time to update and merge Mark's and my trunk-math branch. The patch is collaborated work of Mark Dickinson and me. It was mostly done a few months ago. The patch fixes a lot of loose ends and edge cases related to operations with NaN, INF, very small values and complex math. The patch also adds acosh, asinh, atanh, log1p and copysign to all platforms. Finally it fixes differences between platforms like different results or exceptions for edge cases. Have fun :) ........ r62382 | christian.heimes | 2008-04-19 01:40:40 +0200 (Sat, 19 Apr 2008) | 2 lines Added new files to Windows project files More Windows related fixes are coming soon ........ r62383 | christian.heimes | 2008-04-19 01:49:11 +0200 (Sat, 19 Apr 2008) | 1 line Stupid me. Py_RETURN_NAN should actually return something ... ........

generated by cgit v0.12 at 2025-07-25 19:29:38 (GMT)

/* Peephole optimizations for bytecode compiler. */

#include "Python.h"

#include "Python-ast.h"
#include "node.h"
#include "ast.h"
#include "code.h"
#include "symtable.h"
#include "opcode.h"

#define GETARG(arr, i) ((int)((arr[i+2]<<8) + arr[i+1]))
#define UNCONDITIONAL_JUMP(op)  (op==JUMP_ABSOLUTE || op==JUMP_FORWARD)
#define CONDITIONAL_JUMP(op) (op==POP_JUMP_IF_FALSE || op==POP_JUMP_IF_TRUE \
    || op==JUMP_IF_FALSE_OR_POP || op==JUMP_IF_TRUE_OR_POP)
#define ABSOLUTE_JUMP(op) (op==JUMP_ABSOLUTE || op==CONTINUE_LOOP \
    || op==POP_JUMP_IF_FALSE || op==POP_JUMP_IF_TRUE \
    || op==JUMP_IF_FALSE_OR_POP || op==JUMP_IF_TRUE_OR_POP)
#define JUMPS_ON_TRUE(op) (op==POP_JUMP_IF_TRUE || op==JUMP_IF_TRUE_OR_POP)
#define GETJUMPTGT(arr, i) (GETARG(arr,i) + (ABSOLUTE_JUMP(arr[i]) ? 0 : i+3))
#define SETARG(arr, i, val) do {                            \
    assert(0 <= val && val <= 0xffff);                      \
    arr[i+2] = (unsigned char)(((unsigned int)val)>>8);     \
    arr[i+1] = (unsigned char)(((unsigned int)val) & 255);  \
} while(0)
#define CODESIZE(op)  (HAS_ARG(op) ? 3 : 1)
#define ISBASICBLOCK(blocks, start, bytes) \
    (blocks[start]==blocks[start+bytes-1])


#define CONST_STACK_CREATE() { \
    const_stack_size = 256; \
    const_stack = PyMem_New(PyObject *, const_stack_size); \
    load_const_stack = PyMem_New(Py_ssize_t, const_stack_size); \
    if (!const_stack || !load_const_stack) { \
        PyErr_NoMemory(); \
        goto exitError; \
    } \
    }

#define CONST_STACK_DELETE() do { \
    if (const_stack) \
        PyMem_Free(const_stack); \
    if (load_const_stack) \
        PyMem_Free(load_const_stack); \
    } while(0)

#define CONST_STACK_LEN() (const_stack_top + 1)

#define CONST_STACK_PUSH_OP(i) do { \
    PyObject *_x; \
    assert(codestr[i] == LOAD_CONST); \
    assert(PyList_GET_SIZE(consts) > GETARG(codestr, i)); \
    _x = PyList_GET_ITEM(consts, GETARG(codestr, i)); \
    if (++const_stack_top >= const_stack_size) { \
        const_stack_size *= 2; \
        PyMem_Resize(const_stack, PyObject *, const_stack_size); \
        PyMem_Resize(load_const_stack, Py_ssize_t, const_stack_size); \
        if (!const_stack || !load_const_stack) { \
            PyErr_NoMemory(); \
            goto exitError; \
        } \
    } \
    load_const_stack[const_stack_top] = i; \
    const_stack[const_stack_top] = _x; \
    in_consts = 1; \
    } while(0)

#define CONST_STACK_RESET() do { \
    const_stack_top = -1; \
    } while(0)

#define CONST_STACK_TOP() \
    const_stack[const_stack_top]

#define CONST_STACK_LASTN(i) \
    &const_stack[const_stack_top - i + 1]

#define CONST_STACK_POP(i) do { \
    assert(const_stack_top + 1 >= i); \
    const_stack_top -= i; \
    } while(0)

#define CONST_STACK_OP_LASTN(i) \
    ((const_stack_top >= i - 1) ? load_const_stack[const_stack_top - i + 1] : -1)


/* 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
   new constant (c1, c2, ... cn) can be appended.
   Called with codestr pointing to the first LOAD_CONST.
   Bails out with no change if one or more of the LOAD_CONSTs is missing.
   Also works for BUILD_LIST and BUILT_SET when followed by an "in" or "not in"
   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, PyObject **objs)
{
    PyObject *newconst, *constant;
    Py_ssize_t i, len_consts;

    /* Pre-conditions */
    assert(PyList_CheckExact(consts));

    /* Buildup new tuple of constants */
    newconst = PyTuple_New(n);
    if (newconst == NULL)
        return 0;
    len_consts = PyList_GET_SIZE(consts);
    for (i=0 ; i<n ; i++) {
        constant = objs[i];
        Py_INCREF(constant);
        PyTuple_SET_ITEM(newconst, i, constant);
    }

    /* If it's a BUILD_SET, use the PyTuple we just built to create a
      PyFrozenSet, and use that as the constant instead: */
    if (codestr[0] == BUILD_SET) {
        PyObject *tuple = newconst;
        newconst = PyFrozenSet_New(tuple);
        Py_DECREF(tuple);
        if (newconst == NULL)
            return 0;
    }

    /* Append folded constant onto consts */
    if (PyList_Append(consts, newconst)) {
        Py_DECREF(newconst);
        return 0;
    }
    Py_DECREF(newconst);

    /* Write NOPs over old LOAD_CONSTS and
       add a new LOAD_CONST newconst on top of the BUILD_TUPLE n */
    codestr[0] = LOAD_CONST;
    SETARG(codestr, 0, len_consts);
    return 1;
}

/* Replace LOAD_CONST c1. LOAD_CONST c2 BINOP
   with    LOAD_CONST binop(c1,c2)
   The consts table must still be in list form so that the
   new constant can be appended.
   Called with codestr pointing to the BINOP.
   Abandons the transformation if the folding fails (i.e.  1+'a').
   If the new constant is a sequence, only folds when the size
   is below a threshold value.  That keeps pyc files from
   becoming large in the presence of code like:  (None,)*1000.
*/
static int
fold_binops_on_constants(unsigned char *codestr, PyObject *consts, PyObject **objs)
{
    PyObject *newconst, *v, *w;
    Py_ssize_t len_consts, size;
    int opcode;

    /* Pre-conditions */
    assert(PyList_CheckExact(consts));

    /* Create new constant */
    v = objs[0];
    w = objs[1];
    opcode = codestr[0];
    switch (opcode) {
        case BINARY_POWER:
            newconst = PyNumber_Power(v, w, Py_None);
            break;
        case BINARY_MULTIPLY:
            newconst = PyNumber_Multiply(v, w);
            break;
        case BINARY_TRUE_DIVIDE:
            newconst = PyNumber_TrueDivide(v, w);
            break;
        case BINARY_FLOOR_DIVIDE:
            newconst = PyNumber_FloorDivide(v, w);
            break;
        case BINARY_MODULO:
            newconst = PyNumber_Remainder(v, w);
            break;
        case BINARY_ADD:
            newconst = PyNumber_Add(v, w);
            break;
        case BINARY_SUBTRACT:
            newconst = PyNumber_Subtract(v, w);
            break;
        case BINARY_SUBSCR:
            newconst = PyObject_GetItem(v, w);
            break;
        case BINARY_LSHIFT:
            newconst = PyNumber_Lshift(v, w);
            break;
        case BINARY_RSHIFT:
            newconst = PyNumber_Rshift(v, w);
            break;
        case BINARY_AND:
            newconst = PyNumber_And(v, w);
            break;
        case BINARY_XOR:
            newconst = PyNumber_Xor(v, w);
            break;
        case BINARY_OR:
            newconst = PyNumber_Or(v, w);
            break;
        default:
            /* Called with an unknown opcode */
            PyErr_Format(PyExc_SystemError,
                 "unexpected binary operation %d on a constant",
                     opcode);
            return 0;
    }
    if (newconst == NULL) {
        if(!PyErr_ExceptionMatches(PyExc_KeyboardInterrupt))
            PyErr_Clear();
        return 0;
    }
    size = PyObject_Size(newconst);
    if (size == -1) {
        if (PyErr_ExceptionMatches(PyExc_KeyboardInterrupt))
            return 0;
        PyErr_Clear();
    } else if (size > 20) {
        Py_DECREF(newconst);
        return 0;
    }

    /* Append folded constant into consts table */
    len_consts = PyList_GET_SIZE(consts);
    if (PyList_Append(consts, newconst)) {
        Py_DECREF(newconst);
        return 0;
    }
    Py_DECREF(newconst);

    /* Write NOP NOP NOP NOP LOAD_CONST newconst */
    codestr[-2] = LOAD_CONST;
    SETARG(codestr, -2, len_consts);
    return 1;
}

static int
fold_unaryops_on_constants(unsigned char *codestr, PyObject *consts, PyObject *v)
{
    PyObject *newconst;
    Py_ssize_t len_consts;
    int opcode;

    /* Pre-conditions */
    assert(PyList_CheckExact(consts));
    assert(codestr[0] == LOAD_CONST);

    /* Create new constant */
    opcode = codestr[3];
    switch (opcode) {
        case UNARY_NEGATIVE:
            newconst = PyNumber_Negative(v);
            break;
        case UNARY_INVERT:
            newconst = PyNumber_Invert(v);
            break;
        case UNARY_POSITIVE:
            newconst = PyNumber_Positive(v);
            break;
        default:
            /* Called with an unknown opcode */
            PyErr_Format(PyExc_SystemError,
                 "unexpected unary operation %d on a constant",
                     opcode);
            return 0;
    }
    if (newconst == NULL) {
        if(!PyErr_ExceptionMatches(PyExc_KeyboardInterrupt))
            PyErr_Clear();
        return 0;
    }

    /* Append folded constant into consts table */
    len_consts = PyList_GET_SIZE(consts);
    if (PyList_Append(consts, newconst)) {
        Py_DECREF(newconst);
        PyErr_Clear();
        return 0;
    }
    Py_DECREF(newconst);

    /* Write NOP LOAD_CONST newconst */
    codestr[0] = NOP;
    codestr[1] = LOAD_CONST;
    SETARG(codestr, 1, len_consts);
    return 1;
}

static unsigned int *
markblocks(unsigned char *code, Py_ssize_t len)
{
    unsigned int *blocks = PyMem_New(unsigned int, len);
    int i,j, opcode, blockcnt = 0;

    if (blocks == NULL) {
        PyErr_NoMemory();
        return NULL;
    }
    memset(blocks, 0, len*sizeof(int));

    /* Mark labels in the first pass */
    for (i=0 ; i<len ; i+=CODESIZE(opcode)) {
        opcode = code[i];
        switch (opcode) {
            case FOR_ITER:
            case JUMP_FORWARD:
            case JUMP_IF_FALSE_OR_POP:
            case JUMP_IF_TRUE_OR_POP:
            case POP_JUMP_IF_FALSE:
            case POP_JUMP_IF_TRUE:
            case JUMP_ABSOLUTE:
            case CONTINUE_LOOP:
            case SETUP_LOOP:
            case SETUP_EXCEPT:
            case SETUP_FINALLY:
            case SETUP_WITH:
            case SETUP_ASYNC_WITH:
                j = GETJUMPTGT(code, i);
                blocks[j] = 1;
                break;
        }
    }
    /* Build block numbers in the second pass */
    for (i=0 ; i<len ; i++) {
        blockcnt += blocks[i];          /* increment blockcnt over labels */
        blocks[i] = blockcnt;
    }
    return blocks;
}

/* 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.

   To keep the optimizer simple, it bails out (does nothing) for code that
   has a length over 32,700, and does not calculate extended arguments.
   That allows us to avoid overflow and sign issues. Likewise, it bails when
   the lineno table has complex encoding for gaps >= 255. EXTENDED_ARG can
   appear before MAKE_FUNCTION; in this case both opcodes are skipped.
   EXTENDED_ARG preceding any other opcode causes the optimizer to bail.

   Optimizations are restricted to simple transformations occurring within a
   single basic block.  All transformations keep the code size the same or
   smaller.  For those that reduce size, the gaps are initially filled with
   NOPs.  Later those NOPs are removed and the jump addresses retargeted in
   a single pass.  Line numbering is adjusted accordingly. */

PyObject *
PyCode_Optimize(PyObject *code, PyObject* consts, PyObject *names,
                PyObject *lineno_obj)
{
    Py_ssize_t i, j, codelen;
    int nops, h, adj;
    int tgt, tgttgt, opcode;
    unsigned char *codestr = NULL;
    unsigned char *lineno;
    int *addrmap = NULL;
    int new_line, cum_orig_line, last_line;
    Py_ssize_t tabsiz;
    PyObject **const_stack = NULL;
    Py_ssize_t *load_const_stack = NULL;
    Py_ssize_t const_stack_top = -1;
    Py_ssize_t const_stack_size = 0;
    int in_consts = 0;  /* whether we are in a LOAD_CONST sequence */
    unsigned int *blocks = NULL;

    /* Bail out if an exception is set */
    if (PyErr_Occurred())
        goto exitError;

    /* Bypass optimization when the lineno table is too complex */
    assert(PyBytes_Check(lineno_obj));
    lineno = (unsigned char*)PyBytes_AS_STRING(lineno_obj);
    tabsiz = PyBytes_GET_SIZE(lineno_obj);
    if (memchr(lineno, 255, tabsiz) != NULL)
        goto exitUnchanged;

    /* Avoid situations where jump retargeting could overflow */
    assert(PyBytes_Check(code));
    codelen = PyBytes_GET_SIZE(code);
    if (codelen > 32700)
        goto exitUnchanged;

    /* Make a modifiable copy of the code string */
    codestr = (unsigned char *)PyMem_Malloc(codelen);
    if (codestr == NULL) {
        PyErr_NoMemory();
        goto exitError;
    }
    codestr = (unsigned char *)memcpy(codestr,
                                      PyBytes_AS_STRING(code), codelen);

    /* Verify that RETURN_VALUE terminates the codestring.      This allows
       the various transformation patterns to look ahead several
       instructions without additional checks to make sure they are not
       looking beyond the end of the code string.
    */
    if (codestr[codelen-1] != RETURN_VALUE)
        goto exitUnchanged;

    /* Mapping to new jump targets after NOPs are removed */
    addrmap = PyMem_New(int, codelen);
    if (addrmap == NULL) {
        PyErr_NoMemory();
        goto exitError;
    }

    blocks = markblocks(codestr, codelen);
    if (blocks == NULL)
        goto exitError;
    assert(PyList_Check(consts));

    CONST_STACK_CREATE();

    for (i=0 ; i<codelen ; i += CODESIZE(codestr[i])) {
      reoptimize_current:
        opcode = codestr[i];

        if (!in_consts) {
            CONST_STACK_RESET();
        }
        in_consts = 0;

        switch (opcode) {
            /* Replace UNARY_NOT POP_JUMP_IF_FALSE
               with    POP_JUMP_IF_TRUE */
            case UNARY_NOT:
                if (codestr[i+1] != POP_JUMP_IF_FALSE
                    || !ISBASICBLOCK(blocks,i,4))
                    continue;
                j = GETARG(codestr, i+1);
                codestr[i] = POP_JUMP_IF_TRUE;
                SETARG(codestr, i, j);
                codestr[i+3] = NOP;
                goto reoptimize_current;

                /* not a is b -->  a is not b
                   not a in b -->  a not in b
                   not a is not b -->  a is b
                   not a not in b -->  a in b
                */
            case COMPARE_OP:
                j = GETARG(codestr, i);
                if (j < 6  ||  j > 9  ||
                    codestr[i+3] != UNARY_NOT  ||
                    !ISBASICBLOCK(blocks,i,4))
                    continue;
                SETARG(codestr, i, (j^1));
                codestr[i+3] = NOP;
                break;

                /* Skip over LOAD_CONST trueconst
                   POP_JUMP_IF_FALSE xx. This improves
                   "while 1" performance. */
            case LOAD_CONST:
                CONST_STACK_PUSH_OP(i);
                j = GETARG(codestr, i);
                if (codestr[i+3] != POP_JUMP_IF_FALSE  ||
                    !ISBASICBLOCK(blocks,i,6)  ||
                    !PyObject_IsTrue(PyList_GET_ITEM(consts, j)))
                    continue;
                memset(codestr+i, NOP, 6);
                CONST_STACK_RESET();
                break;

                /* Try to fold tuples of constants (includes a case for lists and sets
                   which are only used for "in" and "not in" tests).
                   Skip over BUILD_SEQN 1 UNPACK_SEQN 1.
                   Replace BUILD_SEQN 2 UNPACK_SEQN 2 with ROT2.
                   Replace BUILD_SEQN 3 UNPACK_SEQN 3 with ROT3 ROT2. */
            case BUILD_TUPLE:
            case BUILD_LIST:
            case BUILD_SET:
                j = GETARG(codestr, i);
                if (j == 0)
                    break;
                h = CONST_STACK_OP_LASTN(j);
                assert((h >= 0 || CONST_STACK_LEN() < j));
                if (h >= 0 && j > 0 && j <= CONST_STACK_LEN() &&
                    ((opcode == BUILD_TUPLE &&
                      ISBASICBLOCK(blocks, h, i-h+3)) ||
                     ((opcode == BUILD_LIST || opcode == BUILD_SET) &&
                      codestr[i+3]==COMPARE_OP &&
                      ISBASICBLOCK(blocks, h, i-h+6) &&
                      (GETARG(codestr,i+3)==6 ||
                       GETARG(codestr,i+3)==7))) &&
                    tuple_of_constants(&codestr[i], j, consts, CONST_STACK_LASTN(j))) {
                    assert(codestr[i] == LOAD_CONST);
                    memset(&codestr[h], NOP, i - h);
                    CONST_STACK_POP(j);
                    CONST_STACK_PUSH_OP(i);
                    break;
                }
                if (codestr[i+3] != UNPACK_SEQUENCE  ||
                    !ISBASICBLOCK(blocks,i,6) ||
                    j != GETARG(codestr, i+3) ||
                    opcode == BUILD_SET)
                    continue;
                if (j == 1) {
                    memset(codestr+i, NOP, 6);
                } else if (j == 2) {
                    codestr[i] = ROT_TWO;
                    memset(codestr+i+1, NOP, 5);
                    CONST_STACK_RESET();
                } else if (j == 3) {
                    codestr[i] = ROT_THREE;
                    codestr[i+1] = ROT_TWO;
                    memset(codestr+i+2, NOP, 4);
                    CONST_STACK_RESET();
                }
                break;

                /* 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:
                /* NOTE: LOAD_CONST is saved at `i-2` since it has an arg
                   while BINOP hasn't */
                h = CONST_STACK_OP_LASTN(2);
                assert((h >= 0 || CONST_STACK_LEN() < 2));
                if (h >= 0 &&
                    ISBASICBLOCK(blocks, h, i-h+1)  &&
                    fold_binops_on_constants(&codestr[i], consts, CONST_STACK_LASTN(2))) {
                    i -= 2;
                    memset(&codestr[h], NOP, i - h);
                    assert(codestr[i] == LOAD_CONST);
                    CONST_STACK_POP(2);
                    CONST_STACK_PUSH_OP(i);
                }
                break;

                /* Fold unary ops on constants.
                   LOAD_CONST c1  UNARY_OP -->                  LOAD_CONST unary_op(c) */
            case UNARY_NEGATIVE:
            case UNARY_INVERT:
            case UNARY_POSITIVE:
                h = CONST_STACK_OP_LASTN(1);
                assert((h >= 0 || CONST_STACK_LEN() < 1));
                if (h >= 0 &&
                    ISBASICBLOCK(blocks, h, i-h+1)  &&
                    fold_unaryops_on_constants(&codestr[i-3], consts, CONST_STACK_TOP())) {
                    i -= 2;
                    assert(codestr[i] == LOAD_CONST);
                    CONST_STACK_POP(1);
                    CONST_STACK_PUSH_OP(i);
                }
                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_OR_POP y   y:JUMP_IF_FALSE_OR_POP z
                      -->  x:JUMP_IF_FALSE_OR_POP z
                   x:JUMP_IF_FALSE_OR_POP y   y:JUMP_IF_TRUE_OR_POP z
                      -->  x:POP_JUMP_IF_FALSE y+3
                   where y+3 is the instruction following the second test.
                */
            case JUMP_IF_FALSE_OR_POP:
            case JUMP_IF_TRUE_OR_POP:
                tgt = GETJUMPTGT(codestr, i);
                j = codestr[tgt];
                if (CONDITIONAL_JUMP(j)) {
                    /* NOTE: all possible jumps here are
                       absolute! */
                    if (JUMPS_ON_TRUE(j) == JUMPS_ON_TRUE(opcode)) {
                        /* The second jump will be
                           taken iff the first is. */
                        tgttgt = GETJUMPTGT(codestr, tgt);
                        /* The current opcode inherits
                           its target's stack behaviour */
                        codestr[i] = j;
                        SETARG(codestr, i, tgttgt);
                        goto reoptimize_current;
                    } else {
                        /* The second jump is not taken
                           if the first is (so jump past
                           it), and all conditional
                           jumps pop their argument when
                           they're not taken (so change
                           the first jump to pop its
                           argument when it's taken). */
                        if (JUMPS_ON_TRUE(opcode))
                            codestr[i] = POP_JUMP_IF_TRUE;
                        else
                            codestr[i] = POP_JUMP_IF_FALSE;
                        SETARG(codestr, i, (tgt + 3));
                        goto reoptimize_current;
                    }
                }
                /* Intentional fallthrough */

                /* Replace jumps to unconditional jumps */
            case POP_JUMP_IF_FALSE:
            case POP_JUMP_IF_TRUE:
            case FOR_ITER:
            case JUMP_FORWARD:
            case JUMP_ABSOLUTE:
            case CONTINUE_LOOP:
            case SETUP_LOOP:
            case SETUP_EXCEPT:
            case SETUP_FINALLY:
            case SETUP_WITH:
            case SETUP_ASYNC_WITH:
                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])) {
        assert(i - nops <= INT_MAX);
        addrmap[i] = (int)(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:
            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:
            case SETUP_ASYNC_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);
    CONST_STACK_DELETE();
    PyMem_Free(addrmap);
    PyMem_Free(codestr);
    PyMem_Free(blocks);
    return code;

 exitError:
    code = NULL;

 exitUnchanged:
    CONST_STACK_DELETE();
    if (blocks != NULL)
        PyMem_Free(blocks);
    if (addrmap != NULL)
        PyMem_Free(addrmap);
    if (codestr != NULL)
        PyMem_Free(codestr);
    Py_XINCREF(code);
    return code;
}