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[3.10] bpo-45773: Stop "optimizing" certain jump patterns (GH-29526)

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Brandt Bucher 2021-11-11 13:52:43 -08:00 • committed by GitHub
parent c5bfb88eb6
commit a89bbde83f
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6 changed files with 60 additions and 81 deletions
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115
Python/compile.c
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@ -21,6 +21,8 @@
* objects.
*/
#include <stdbool.h>
#include "Python.h"
#include "pycore_ast.h" // _PyAST_GetDocString()
#include "pycore_compile.h" // _PyFuture_FromAST()
@ -7264,25 +7266,24 @@ fold_rotations(struct instr *inst, int n)
}
}
static int
eliminate_jump_to_jump(basicblock *bb, int opcode) {
assert (bb->b_iused > 0);
struct instr *inst = &bb->b_instr[bb->b_iused-1];
assert (is_jump(inst));
assert (inst->i_target->b_iused > 0);
struct instr *target = &inst->i_target->b_instr[0];
if (inst->i_target == target->i_target) {
/* Nothing to do */
return 0;
// Attempt to eliminate jumps to jumps by updating inst to jump to
// target->i_target using the provided opcode. Return whether or not the
// optimization was successful.
static bool
jump_thread(struct instr *inst, struct instr *target, int opcode)
{
assert(is_jump(inst));
assert(is_jump(target));
// bpo-45773: If inst->i_target == target->i_target, then nothing actually
// changes (and we fall into an infinite loop):
if (inst->i_lineno == target->i_lineno &&
inst->i_target != target->i_target)
{
inst->i_target = target->i_target;
inst->i_opcode = opcode;
return true;
}
int lineno = target->i_lineno;
if (add_jump_to_block(bb, opcode, lineno, target->i_target) == 0) {
return -1;
}
assert (bb->b_iused >= 2);
bb->b_instr[bb->b_iused-2].i_opcode = NOP;
return 0;
return false;
}
/* Maximum size of basic block that should be copied in optimizer */
@ -7399,25 +7400,21 @@ optimize_basic_block(struct compiler *c, basicblock *bb, PyObject *consts)
where y+1 is the instruction following the second test.
*/
case JUMP_IF_FALSE_OR_POP:
switch(target->i_opcode) {
switch (target->i_opcode) {
case POP_JUMP_IF_FALSE:
if (inst->i_lineno == target->i_lineno) {
*inst = *target;
i--;
}
i -= jump_thread(inst, target, POP_JUMP_IF_FALSE);
break;
case JUMP_ABSOLUTE:
case JUMP_FORWARD:
case JUMP_IF_FALSE_OR_POP:
if (inst->i_lineno == target->i_lineno &&
inst->i_target != target->i_target) {
inst->i_target = target->i_target;
i--;
}
i -= jump_thread(inst, target, JUMP_IF_FALSE_OR_POP);
break;
case JUMP_IF_TRUE_OR_POP:
assert (inst->i_target->b_iused == 1);
case POP_JUMP_IF_TRUE:
if (inst->i_lineno == target->i_lineno) {
// We don't need to bother checking for loops here,
// since a block's b_next cannot point to itself:
assert(inst->i_target != inst->i_target->b_next);
inst->i_opcode = POP_JUMP_IF_FALSE;
inst->i_target = inst->i_target->b_next;
--i;
@ -7425,27 +7422,22 @@ optimize_basic_block(struct compiler *c, basicblock *bb, PyObject *consts)
break;
}
break;
case JUMP_IF_TRUE_OR_POP:
switch(target->i_opcode) {
switch (target->i_opcode) {
case POP_JUMP_IF_TRUE:
if (inst->i_lineno == target->i_lineno) {
*inst = *target;
i--;
}
i -= jump_thread(inst, target, POP_JUMP_IF_TRUE);
break;
case JUMP_ABSOLUTE:
case JUMP_FORWARD:
case JUMP_IF_TRUE_OR_POP:
if (inst->i_lineno == target->i_lineno &&
inst->i_target != target->i_target) {
inst->i_target = target->i_target;
i--;
}
i -= jump_thread(inst, target, JUMP_IF_TRUE_OR_POP);
break;
case JUMP_IF_FALSE_OR_POP:
assert (inst->i_target->b_iused == 1);
case POP_JUMP_IF_FALSE:
if (inst->i_lineno == target->i_lineno) {
// We don't need to bother checking for loops here,
// since a block's b_next cannot point to itself:
assert(inst->i_target != inst->i_target->b_next);
inst->i_opcode = POP_JUMP_IF_TRUE;
inst->i_target = inst->i_target->b_next;
--i;
@ -7453,54 +7445,33 @@ optimize_basic_block(struct compiler *c, basicblock *bb, PyObject *consts)
break;
}
break;
case POP_JUMP_IF_FALSE:
switch(target->i_opcode) {
switch (target->i_opcode) {
case JUMP_ABSOLUTE:
case JUMP_FORWARD:
if (inst->i_lineno == target->i_lineno) {
inst->i_target = target->i_target;
i--;
}
break;
case JUMP_IF_FALSE_OR_POP:
i -= jump_thread(inst, target, POP_JUMP_IF_FALSE);
}
break;
case POP_JUMP_IF_TRUE:
switch(target->i_opcode) {
switch (target->i_opcode) {
case JUMP_ABSOLUTE:
case JUMP_FORWARD:
if (inst->i_lineno == target->i_lineno) {
inst->i_target = target->i_target;
i--;
}
break;
case JUMP_IF_TRUE_OR_POP:
i -= jump_thread(inst, target, POP_JUMP_IF_TRUE);
}
break;
case JUMP_ABSOLUTE:
case JUMP_FORWARD:
assert (i == bb->b_iused-1);
switch(target->i_opcode) {
case JUMP_FORWARD:
if (eliminate_jump_to_jump(bb, inst->i_opcode)) {
goto error;
}
break;
switch (target->i_opcode) {
case JUMP_ABSOLUTE:
if (eliminate_jump_to_jump(bb, JUMP_ABSOLUTE)) {
goto error;
}
break;
case JUMP_FORWARD:
i -= jump_thread(inst, target, JUMP_ABSOLUTE);
}
break;
case FOR_ITER:
assert (i == bb->b_iused-1);
if (target->i_opcode == JUMP_FORWARD) {
if (eliminate_jump_to_jump(bb, inst->i_opcode)) {
goto error;
}
i -= jump_thread(inst, target, FOR_ITER);
}
break;
case ROT_N: