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SF patch #707257: Improve code generation 

Adds a single function to improve generated bytecode.  Has a single line
attachment point, so it is completely de-coupled from both the compiler
and ceval.c.

Makes three simple transforms that do not require a basic block analysis
or re-ordering of code.  Gives improved timings on pystone, pybench,
and any code using either "while 1" or "x,y=y,x".
This commit is contained in:
Raymond Hettinger 2003-03-26 01:07:54 +00:00
parent 590fe02ebd
commit f6f575ae6f
1 changed files with 94 additions and 2 deletions
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96
Python/compile.c
View File

@ -323,6 +323,99 @@ intern_strings(PyObject *tuple)
return 0;
}
#define GETARG(arr, i) ((int)((arr[i+2]<<8) + arr[i+1]))
#define UNCONDITIONAL_JUMP(op) (op==JUMP_ABSOLUTE || op==JUMP_FORWARD)
#define GETJUMPTGT(arr, i) (GETARG(arr,i) + (arr[i]==JUMP_ABSOLUTE ? 0 : i+3))
#define SETARG(arr, i, val) arr[i+2] = val>>8; arr[i+1] = val & 255
static PyObject *
optimize_code(PyObject *code, PyObject* consts)
{
int i, j, codelen;
int tgt, tgttgt, opcode;
unsigned char *codestr;
/* Make a modifiable copy of the code string */
if (!PyString_Check(code))
goto exitUnchanged;
codelen = PyString_Size(code);
codestr = PyMem_Malloc(codelen);
if (codestr == NULL)
goto exitUnchanged;
codestr = memcpy(codestr, PyString_AS_STRING(code), codelen);
assert(PyTuple_Check(consts));
for (i=0 ; i<codelen-7 ; i += HAS_ARG(codestr[i]) ? 3 : 1) {
opcode = codestr[i];
switch (opcode) {
/* Skip over LOAD_CONST trueconst JUMP_IF_FALSE xx POP_TOP.
Note, only the first opcode is changed, the others still
perform normally if they happen to be jump targets. */
case LOAD_CONST:
j = GETARG(codestr, i);
if (codestr[i+3] != JUMP_IF_FALSE ||
codestr[i+6] != POP_TOP ||
!PyObject_IsTrue(PyTuple_GET_ITEM(consts, j)))
continue;
codestr[i] = JUMP_FORWARD;
SETARG(codestr, i, 4);
break;
/* Replace BUILD_SEQN 2 UNPACK_SEQN 2 with ROT2 JMP+2.
Note, these opcodes occur together only in assignment
statements. Accordingly, the unpack opcode is never
a jump target. */
case BUILD_TUPLE:
case BUILD_LIST:
if (codestr[i+3] != UNPACK_SEQUENCE ||
GETARG(codestr, i) != 2 ||
GETARG(codestr, i+3) != 2)
continue;
codestr[i] = ROT_TWO;
codestr[i+1] = JUMP_FORWARD;
SETARG(codestr, i+1, 2);
codestr[i+4] = DUP_TOP; /* Filler codes used as NOPs */
codestr[i+5] = POP_TOP;
break;
/* Replace jumps to unconditional jumps */
case JUMP_FORWARD:
case JUMP_IF_FALSE:
case JUMP_IF_TRUE:
case JUMP_ABSOLUTE:
case CONTINUE_LOOP:
case SETUP_LOOP:
case SETUP_EXCEPT:
case SETUP_FINALLY:
tgt = GETJUMPTGT(codestr, i);
if (!UNCONDITIONAL_JUMP(codestr[tgt]))
continue;
tgttgt = GETJUMPTGT(codestr, tgt);
if (opcode == JUMP_FORWARD) /* JMP_ABS can go backwards */
opcode = JUMP_ABSOLUTE;
if (opcode != JUMP_ABSOLUTE && opcode != CONTINUE_LOOP)
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:
PyMem_Free(codestr);
goto exitUnchanged;
}
}
code = PyString_FromStringAndSize(codestr, codelen);
PyMem_Free(codestr);
return code;
exitUnchanged:
Py_INCREF(code);
return code;
}
PyCodeObject *
PyCode_New(int argcount, int nlocals, int stacksize, int flags,
PyObject *code, PyObject *consts, PyObject *names,
@ -366,8 +459,7 @@ PyCode_New(int argcount, int nlocals, int stacksize, int flags,
co->co_nlocals = nlocals;
co->co_stacksize = stacksize;
co->co_flags = flags;
Py_INCREF(code);
co->co_code = code;
co->co_code = optimize_code(code, consts);
Py_INCREF(consts);
co->co_consts = consts;
Py_INCREF(names);