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gh-93554: Conditional jump opcodes only jump forward (GH-96318)

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Irit Katriel 2022-09-01 21:36:47 +01:00 • committed by GitHub
parent a91f25577c
commit 4c72517cad
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GPG key ID: 4AEE18F83AFDEB23
13 changed files with 298 additions and 448 deletions
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154
Python/compile.c
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@ -96,23 +96,11 @@
#define IS_ASSEMBLER_OPCODE(opcode) \
((opcode) == JUMP_FORWARD || \
(opcode) == JUMP_BACKWARD || \
(opcode) == JUMP_BACKWARD_NO_INTERRUPT || \
(opcode) == POP_JUMP_FORWARD_IF_NONE || \
(opcode) == POP_JUMP_BACKWARD_IF_NONE || \
(opcode) == POP_JUMP_FORWARD_IF_NOT_NONE || \
(opcode) == POP_JUMP_BACKWARD_IF_NOT_NONE || \
(opcode) == POP_JUMP_FORWARD_IF_TRUE || \
(opcode) == POP_JUMP_BACKWARD_IF_TRUE || \
(opcode) == POP_JUMP_FORWARD_IF_FALSE || \
(opcode) == POP_JUMP_BACKWARD_IF_FALSE)
(opcode) == JUMP_BACKWARD_NO_INTERRUPT)
#define IS_BACKWARDS_JUMP_OPCODE(opcode) \
((opcode) == JUMP_BACKWARD || \
(opcode) == JUMP_BACKWARD_NO_INTERRUPT || \
(opcode) == POP_JUMP_BACKWARD_IF_NONE || \
(opcode) == POP_JUMP_BACKWARD_IF_NOT_NONE || \
(opcode) == POP_JUMP_BACKWARD_IF_TRUE || \
(opcode) == POP_JUMP_BACKWARD_IF_FALSE)
(opcode) == JUMP_BACKWARD_NO_INTERRUPT)
#define IS_UNCONDITIONAL_JUMP_OPCODE(opcode) \
((opcode) == JUMP || \
@ -1146,17 +1134,9 @@ stack_effect(int opcode, int oparg, int jump)
case JUMP_IF_FALSE_OR_POP:
return jump ? 0 : -1;
case POP_JUMP_BACKWARD_IF_NONE:
case POP_JUMP_FORWARD_IF_NONE:
case POP_JUMP_IF_NONE:
case POP_JUMP_BACKWARD_IF_NOT_NONE:
case POP_JUMP_FORWARD_IF_NOT_NONE:
case POP_JUMP_IF_NOT_NONE:
case POP_JUMP_FORWARD_IF_FALSE:
case POP_JUMP_BACKWARD_IF_FALSE:
case POP_JUMP_IF_FALSE:
case POP_JUMP_FORWARD_IF_TRUE:
case POP_JUMP_BACKWARD_IF_TRUE:
case POP_JUMP_IF_TRUE:
return -1;
@ -7747,63 +7727,91 @@ assemble_emit(struct assembler *a, struct instr *i)
return 1;
}
static void
normalize_jumps(basicblock *entryblock)
static int
normalize_jumps_in_block(cfg_builder *g, basicblock *b) {
struct instr *last = basicblock_last_instr(b);
if (last == NULL || !is_jump(last)) {
return 0;
}
assert(!IS_ASSEMBLER_OPCODE(last->i_opcode));
bool is_forward = last->i_target->b_visited == 0;
switch(last->i_opcode) {
case JUMP:
last->i_opcode = is_forward ? JUMP_FORWARD : JUMP_BACKWARD;
return 0;
case JUMP_NO_INTERRUPT:
last->i_opcode = is_forward ?
JUMP_FORWARD : JUMP_BACKWARD_NO_INTERRUPT;
return 0;
}
int reversed_opcode = 0;
switch(last->i_opcode) {
case POP_JUMP_IF_NOT_NONE:
reversed_opcode = POP_JUMP_IF_NONE;
break;
case POP_JUMP_IF_NONE:
reversed_opcode = POP_JUMP_IF_NOT_NONE;
break;
case POP_JUMP_IF_FALSE:
reversed_opcode = POP_JUMP_IF_TRUE;
break;
case POP_JUMP_IF_TRUE:
reversed_opcode = POP_JUMP_IF_FALSE;
break;
case JUMP_IF_TRUE_OR_POP:
case JUMP_IF_FALSE_OR_POP:
if (!is_forward) {
/* As far as we can tell, the compiler never emits
* these jumps with a backwards target. If/when this
* exception is raised, we have found a use case for
* a backwards version of this jump (or to replace
* it with the sequence (COPY 1, POP_JUMP_IF_T/F, POP)
*/
PyErr_Format(PyExc_SystemError,
"unexpected %s jumping backwards",
last->i_opcode == JUMP_IF_TRUE_OR_POP ?
"JUMP_IF_TRUE_OR_POP" : "JUMP_IF_FALSE_OR_POP");
}
return 0;
}
if (is_forward) {
return 0;
}
/* transform 'conditional jump T' to
* 'reversed_jump b_next' followed by 'jump_backwards T'
*/
basicblock *target = last->i_target;
basicblock *backwards_jump = cfg_builder_new_block(g);
if (backwards_jump == NULL) {
return -1;
}
basicblock_addop(backwards_jump, JUMP, target->b_label, NO_LOCATION);
backwards_jump->b_instr[0].i_target = target;
last->i_opcode = reversed_opcode;
last->i_target = b->b_next;
backwards_jump->b_cold = b->b_cold;
backwards_jump->b_next = b->b_next;
b->b_next = backwards_jump;
return 0;
}
static int
normalize_jumps(cfg_builder *g)
{
basicblock *entryblock = g->g_entryblock;
for (basicblock *b = entryblock; b != NULL; b = b->b_next) {
b->b_visited = 0;
}
for (basicblock *b = entryblock; b != NULL; b = b->b_next) {
b->b_visited = 1;
struct instr *last = basicblock_last_instr(b);
if (last == NULL) {
continue;
}
assert(!IS_ASSEMBLER_OPCODE(last->i_opcode));
if (is_jump(last)) {
bool is_forward = last->i_target->b_visited == 0;
switch(last->i_opcode) {
case JUMP:
last->i_opcode = is_forward ? JUMP_FORWARD : JUMP_BACKWARD;
break;
case JUMP_NO_INTERRUPT:
last->i_opcode = is_forward ?
JUMP_FORWARD : JUMP_BACKWARD_NO_INTERRUPT;
break;
case POP_JUMP_IF_NOT_NONE:
last->i_opcode = is_forward ?
POP_JUMP_FORWARD_IF_NOT_NONE : POP_JUMP_BACKWARD_IF_NOT_NONE;
break;
case POP_JUMP_IF_NONE:
last->i_opcode = is_forward ?
POP_JUMP_FORWARD_IF_NONE : POP_JUMP_BACKWARD_IF_NONE;
break;
case POP_JUMP_IF_FALSE:
last->i_opcode = is_forward ?
POP_JUMP_FORWARD_IF_FALSE : POP_JUMP_BACKWARD_IF_FALSE;
break;
case POP_JUMP_IF_TRUE:
last->i_opcode = is_forward ?
POP_JUMP_FORWARD_IF_TRUE : POP_JUMP_BACKWARD_IF_TRUE;
break;
case JUMP_IF_TRUE_OR_POP:
case JUMP_IF_FALSE_OR_POP:
if (!is_forward) {
/* As far as we can tell, the compiler never emits
* these jumps with a backwards target. If/when this
* exception is raised, we have found a use case for
* a backwards version of this jump (or to replace
* it with the sequence (COPY 1, POP_JUMP_IF_T/F, POP)
*/
PyErr_Format(PyExc_SystemError,
"unexpected %s jumping backwards",
last->i_opcode == JUMP_IF_TRUE_OR_POP ?
"JUMP_IF_TRUE_OR_POP" : "JUMP_IF_FALSE_OR_POP");
}
break;
}
if (normalize_jumps_in_block(g, b) < 0) {
return -1;
}
}
return 0;
}
static void
@ -8638,7 +8646,9 @@ assemble(struct compiler *c, int addNone)
}
/* Order of basic blocks must have been determined by now */
normalize_jumps(g->g_entryblock);
if (normalize_jumps(g) < 0) {
goto error;
}
if (add_checks_for_loads_of_unknown_variables(g->g_entryblock, c) < 0) {
goto error;