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Patch #1346214: correctly optimize away "if 0"-style stmts

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(thanks to Neal for review)
This commit is contained in:
Georg Brandl 2006-06-04 21:56:52 +00:00
parent 9f16760666
commit ddbaa660d3
5 changed files with 57 additions and 18 deletions
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43
Python/compile.c
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@ -2148,7 +2148,7 @@ static int
compiler_if(struct compiler *c, stmt_ty s)
{
basicblock *end, *next;
int constant;
assert(s->kind == If_kind);
end = compiler_new_block(c);
if (end == NULL)
@ -2156,15 +2156,27 @@ compiler_if(struct compiler *c, stmt_ty s)
next = compiler_new_block(c);
if (next == NULL)
return 0;
VISIT(c, expr, s->v.If.test);
ADDOP_JREL(c, JUMP_IF_FALSE, next);
ADDOP(c, POP_TOP);
VISIT_SEQ(c, stmt, s->v.If.body);
ADDOP_JREL(c, JUMP_FORWARD, end);
compiler_use_next_block(c, next);
ADDOP(c, POP_TOP);
if (s->v.If.orelse)
VISIT_SEQ(c, stmt, s->v.If.orelse);
constant = expr_constant(s->v.If.test);
/* constant = 0: "if 0"
* constant = 1: "if 1", "if 2", ...
* constant = -1: rest */
if (constant == 0) {
if (s->v.If.orelse)
VISIT_SEQ(c, stmt, s->v.If.orelse);
} else if (constant == 1) {
VISIT_SEQ(c, stmt, s->v.If.body);
} else {
VISIT(c, expr, s->v.If.test);
ADDOP_JREL(c, JUMP_IF_FALSE, next);
ADDOP(c, POP_TOP);
VISIT_SEQ(c, stmt, s->v.If.body);
ADDOP_JREL(c, JUMP_FORWARD, end);
compiler_use_next_block(c, next);
ADDOP(c, POP_TOP);
if (s->v.If.orelse)
VISIT_SEQ(c, stmt, s->v.If.orelse);
}
compiler_use_next_block(c, end);
return 1;
}
@ -2639,10 +2651,6 @@ compiler_visit_stmt(struct compiler *c, stmt_ty s)
if (c->u->u_ste->ste_type != FunctionBlock)
return compiler_error(c, "'return' outside function");
if (s->v.Return.value) {
if (c->u->u_ste->ste_generator) {
return compiler_error(c,
"'return' with argument inside generator");
}
VISIT(c, expr, s->v.Return.value);
}
else
@ -3356,6 +3364,13 @@ expr_constant(expr_ty e)
return PyObject_IsTrue(e->v.Num.n);
case Str_kind:
return PyObject_IsTrue(e->v.Str.s);
case Name_kind:
/* __debug__ is not assignable, so we can optimize
* it away in if and while statements */
if (strcmp(PyString_AS_STRING(e->v.Name.id),
"__debug__") == 0)
return ! Py_OptimizeFlag;
/* fall through */
default:
return -1;
}