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Simplify chains of conditional jumps.

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(Suggested by Neal Norwitz.)
This commit is contained in:
Raymond Hettinger 2004-08-25 03:18:29 +00:00
parent 08b07def43
commit ef0a82b682
1 changed files with 25 additions and 2 deletions
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27
Python/compile.c
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@ -550,11 +550,34 @@ optimize_code(PyObject *code, PyObject* consts, PyObject *names, PyObject *linen
} }
break; 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:
"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_FALSE z --> x:JUMP_IF_FALSE y+3
*/
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 */ /* Replace jumps to unconditional jumps */
case FOR_ITER: case FOR_ITER:
case JUMP_FORWARD: case JUMP_FORWARD:
case JUMP_IF_FALSE:
case JUMP_IF_TRUE:
case JUMP_ABSOLUTE: case JUMP_ABSOLUTE:
case CONTINUE_LOOP: case CONTINUE_LOOP:
case SETUP_LOOP: case SETUP_LOOP: