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bpo-42349: Compiler clean up. More yak-shaving for PEP 626. (GH-23267)

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Make sure that CFG from compiler front-end is correct. Be a bit more aggressive in the compiler back-end.
This commit is contained in:
Mark Shannon 2020-11-17 19:30:14 +00:00 • committed by GitHub
parent fa96608513
commit 266b462238
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GPG key ID: 4AEE18F83AFDEB23
7 changed files with 4765 additions and 4669 deletions
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191
Python/compile.c
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@ -2587,6 +2587,7 @@ compiler_jump_if(struct compiler *c, expr_ty e, basicblock *next, int cond)
VISIT(c, expr, (expr_ty)asdl_seq_GET(e->v.Compare.comparators, n));
ADDOP_COMPARE(c, asdl_seq_GET(e->v.Compare.ops, n));
ADDOP_JUMP(c, cond ? POP_JUMP_IF_TRUE : POP_JUMP_IF_FALSE, next);
NEXT_BLOCK(c);
basicblock *end = compiler_new_block(c);
if (end == NULL)
return 0;
@ -2610,6 +2611,7 @@ compiler_jump_if(struct compiler *c, expr_ty e, basicblock *next, int cond)
/* general implementation */
VISIT(c, expr, e);
ADDOP_JUMP(c, cond ? POP_JUMP_IF_TRUE : POP_JUMP_IF_FALSE, next);
NEXT_BLOCK(c);
return 1;
}
@ -2829,7 +2831,7 @@ compiler_async_for(struct compiler *c, stmt_ty s)
static int
compiler_while(struct compiler *c, stmt_ty s)
{
basicblock *loop, *orelse, *end, *anchor = NULL;
basicblock *loop, *body, *end, *anchor = NULL;
int constant = expr_constant(s->v.While.test);
if (constant == 0) {
@ -2850,42 +2852,32 @@ compiler_while(struct compiler *c, stmt_ty s)
return 1;
}
loop = compiler_new_block(c);
body = compiler_new_block(c);
anchor = compiler_new_block(c);
end = compiler_new_block(c);
if (constant == -1) {
anchor = compiler_new_block(c);
if (anchor == NULL)
return 0;
}
if (loop == NULL || end == NULL)
if (loop == NULL || body == NULL || anchor == NULL || end == NULL) {
return 0;
if (s->v.While.orelse) {
orelse = compiler_new_block(c);
if (orelse == NULL)
return 0;
}
else
orelse = NULL;
compiler_use_next_block(c, loop);
if (!compiler_push_fblock(c, WHILE_LOOP, loop, end, NULL))
if (!compiler_push_fblock(c, WHILE_LOOP, loop, end, NULL)) {
return 0;
if (constant == -1) {
if (!compiler_jump_if(c, s->v.While.test, anchor, 0))
return 0;
}
if (constant == -1) {
if (!compiler_jump_if(c, s->v.While.test, anchor, 0)) {
return 0;
}
}
compiler_use_next_block(c, body);
VISIT_SEQ(c, stmt, s->v.While.body);
ADDOP_JUMP(c, JUMP_ABSOLUTE, loop);
/* XXX should the two POP instructions be in a separate block
if there is no else clause ?
*/
if (constant == -1)
compiler_use_next_block(c, anchor);
compiler_pop_fblock(c, WHILE_LOOP, loop);
if (orelse != NULL) /* what if orelse is just pass? */
compiler_use_next_block(c, anchor);
if (s->v.While.orelse) {
VISIT_SEQ(c, stmt, s->v.While.orelse);
}
compiler_use_next_block(c, end);
return 1;
@ -2916,6 +2908,7 @@ compiler_return(struct compiler *c, stmt_ty s)
VISIT(c, expr, s->v.Return.value);
}
ADDOP(c, RETURN_VALUE);
NEXT_BLOCK(c);
return 1;
}
@ -2934,6 +2927,7 @@ compiler_break(struct compiler *c)
return 0;
}
ADDOP_JUMP(c, JUMP_ABSOLUTE, loop->fb_exit);
NEXT_BLOCK(c);
return 1;
}
@ -2948,6 +2942,7 @@ compiler_continue(struct compiler *c)
return compiler_error(c, "'continue' not properly in loop");
}
ADDOP_JUMP(c, JUMP_ABSOLUTE, loop->fb_block);
NEXT_BLOCK(c)
return 1;
}
@ -3087,6 +3082,7 @@ compiler_try_except(struct compiler *c, stmt_ty s)
ADDOP(c, DUP_TOP);
VISIT(c, expr, handler->v.ExceptHandler.type);
ADDOP_JUMP(c, JUMP_IF_NOT_EXC_MATCH, except);
NEXT_BLOCK(c);
}
ADDOP(c, POP_TOP);
if (handler->v.ExceptHandler.name) {
@ -3427,6 +3423,7 @@ compiler_visit_stmt(struct compiler *c, stmt_ty s)
}
}
ADDOP_I(c, RAISE_VARARGS, (int)n);
NEXT_BLOCK(c);
break;
case Try_kind:
return compiler_try(c, s);
@ -4798,6 +4795,7 @@ compiler_with_except_finish(struct compiler *c) {
if (exit == NULL)
return 0;
ADDOP_JUMP(c, POP_JUMP_IF_TRUE, exit);
NEXT_BLOCK(c);
ADDOP(c, RERAISE);
compiler_use_next_block(c, exit);
ADDOP(c, POP_TOP);
@ -5521,6 +5519,7 @@ stackdepth(struct compiler *c)
}
}
if (next != NULL) {
assert(b->b_nofallthrough == 0);
stackdepth_push(&sp, next, depth);
}
}
@ -6096,7 +6095,6 @@ optimize_basic_block(basicblock *bb, PyObject *consts)
struct instr nop;
nop.i_opcode = NOP;
struct instr *target;
int lineno;
for (int i = 0; i < bb->b_iused; i++) {
struct instr *inst = &bb->b_instr[i];
int oparg = inst->i_oparg;
@ -6112,23 +6110,50 @@ optimize_basic_block(basicblock *bb, PyObject *consts)
target = &nop;
}
switch (inst->i_opcode) {
/* Skip over LOAD_CONST trueconst
POP_JUMP_IF_FALSE xx. This improves
"while 1" performance. */
/* Remove LOAD_CONST const; conditional jump */
case LOAD_CONST:
if (nextop != POP_JUMP_IF_FALSE) {
break;
}
PyObject* cnt = PyList_GET_ITEM(consts, oparg);
int is_true = PyObject_IsTrue(cnt);
if (is_true == -1) {
goto error;
}
if (is_true == 1) {
inst->i_opcode = NOP;
bb->b_instr[i+1].i_opcode = NOP;
{
PyObject* cnt;
int is_true;
int jump_if_true;
switch(nextop) {
case POP_JUMP_IF_FALSE:
case POP_JUMP_IF_TRUE:
cnt = PyList_GET_ITEM(consts, oparg);
is_true = PyObject_IsTrue(cnt);
if (is_true == -1) {
goto error;
}
inst->i_opcode = NOP;
jump_if_true = nextop == POP_JUMP_IF_TRUE;
if (is_true == jump_if_true) {
bb->b_instr[i+1].i_opcode = JUMP_ABSOLUTE;
bb->b_nofallthrough = 1;
}
else {
bb->b_instr[i+1].i_opcode = NOP;
}
break;
case JUMP_IF_FALSE_OR_POP:
case JUMP_IF_TRUE_OR_POP:
cnt = PyList_GET_ITEM(consts, oparg);
is_true = PyObject_IsTrue(cnt);
if (is_true == -1) {
goto error;
}
jump_if_true = nextop == JUMP_IF_TRUE_OR_POP;
if (is_true == jump_if_true) {
bb->b_instr[i+1].i_opcode = JUMP_ABSOLUTE;
bb->b_nofallthrough = 1;
}
else {
inst->i_opcode = NOP;
bb->b_instr[i+1].i_opcode = NOP;
}
break;
}
break;
}
/* Try to fold tuples of constants.
Skip over BUILD_SEQN 1 UNPACK_SEQN 1.
@ -6176,16 +6201,21 @@ optimize_basic_block(basicblock *bb, PyObject *consts)
switch(target->i_opcode) {
case POP_JUMP_IF_FALSE:
*inst = *target;
--i;
break;
case JUMP_ABSOLUTE:
case JUMP_FORWARD:
case JUMP_IF_FALSE_OR_POP:
inst->i_target = target->i_target;
if (inst->i_target != target->i_target) {
inst->i_target = target->i_target;
--i;
}
break;
case JUMP_IF_TRUE_OR_POP:
assert (inst->i_target->b_iused == 1);
inst->i_opcode = POP_JUMP_IF_FALSE;
inst->i_target = inst->i_target->b_next;
--i;
break;
}
break;
@ -6194,16 +6224,21 @@ optimize_basic_block(basicblock *bb, PyObject *consts)
switch(target->i_opcode) {
case POP_JUMP_IF_TRUE:
*inst = *target;
--i;
break;
case JUMP_ABSOLUTE:
case JUMP_FORWARD:
case JUMP_IF_TRUE_OR_POP:
inst->i_target = target->i_target;
if (inst->i_target != target->i_target) {
inst->i_target = target->i_target;
--i;
}
break;
case JUMP_IF_FALSE_OR_POP:
assert (inst->i_target->b_iused == 1);
inst->i_opcode = POP_JUMP_IF_TRUE;
inst->i_target = inst->i_target->b_next;
--i;
break;
}
break;
@ -6212,7 +6247,10 @@ optimize_basic_block(basicblock *bb, PyObject *consts)
switch(target->i_opcode) {
case JUMP_ABSOLUTE:
case JUMP_FORWARD:
inst->i_target = target->i_target;
if (inst->i_target != target->i_target) {
inst->i_target = target->i_target;
--i;
}
break;
}
break;
@ -6221,7 +6259,10 @@ optimize_basic_block(basicblock *bb, PyObject *consts)
switch(target->i_opcode) {
case JUMP_ABSOLUTE:
case JUMP_FORWARD:
inst->i_target = target->i_target;
if (inst->i_target != target->i_target) {
inst->i_target = target->i_target;
--i;
}
break;
}
break;
@ -6231,12 +6272,17 @@ optimize_basic_block(basicblock *bb, PyObject *consts)
assert (i == bb->b_iused-1);
switch(target->i_opcode) {
case JUMP_FORWARD:
inst->i_target = target->i_target;
if (inst->i_target != target->i_target) {
inst->i_target = target->i_target;
--i;
}
break;
case JUMP_ABSOLUTE:
lineno = inst->i_lineno;
*inst = *target;
inst->i_lineno = lineno;
if (inst->i_target != target->i_target) {
inst->i_target = target->i_target;
inst->i_opcode = target->i_opcode;
--i;
}
break;
}
if (inst->i_target->b_exit && inst->i_target->b_iused <= MAX_COPY_SIZE) {
@ -6268,15 +6314,15 @@ clean_basic_block(basicblock *bb) {
for (int src = 0; src < bb->b_iused; src++) {
int lineno = bb->b_instr[src].i_lineno;
if (bb->b_instr[src].i_opcode == NOP) {
/* Eliminate no-op if it doesn't have a line number, or
* if the next instruction has same line number or no line number, or
* if the previous instruction had the same line number. */
/* Eliminate no-op if it doesn't have a line number */
if (lineno < 0) {
continue;
}
/* or, if the previous instruction had the same line number. */
if (prev_lineno == lineno) {
continue;
}
/* or, if the next instruction has same line number or no line number */
if (src < bb->b_iused - 1) {
int next_lineno = bb->b_instr[src+1].i_lineno;
if (next_lineno < 0 || next_lineno == lineno) {
@ -6284,6 +6330,19 @@ clean_basic_block(basicblock *bb) {
continue;
}
}
else {
basicblock* next = bb->b_next;
while (next && next->b_iused == 0) {
next = next->b_next;
}
/* or if last instruction in BB and next BB has same line number */
if (next) {
if (lineno == next->b_instr[0].i_lineno) {
continue;
}
}
}
}
if (dest != src) {
bb->b_instr[dest] = bb->b_instr[src];
@ -6295,30 +6354,36 @@ clean_basic_block(basicblock *bb) {
bb->b_iused = dest;
}
static void
normalise_basic_block(basicblock *bb) {
/* Remove any code following a return or re-raise,
and mark those blocks as exit and/or nofallthrough. */
static int
normalize_basic_block(basicblock *bb) {
/* Mark blocks as exit and/or nofallthrough.
Raise SystemError if CFG is malformed. */
for (int i = 0; i < bb->b_iused; i++) {
switch(bb->b_instr[i].i_opcode) {
case RETURN_VALUE:
case RAISE_VARARGS:
case RERAISE:
bb->b_iused = i+1;
bb->b_exit = 1;
bb->b_nofallthrough = 1;
return;
/* fall through */
case JUMP_ABSOLUTE:
case JUMP_FORWARD:
bb->b_iused = i+1;
bb->b_nofallthrough = 1;
return;
/* fall through */
case POP_JUMP_IF_FALSE:
case POP_JUMP_IF_TRUE:
case JUMP_IF_FALSE_OR_POP:
case JUMP_IF_TRUE_OR_POP:
if (i != bb->b_iused-1) {
PyErr_SetString(PyExc_SystemError, "malformed control flow graph.");
return -1;
}
}
}
return 0;
}
static int
mark_reachable(struct assembler *a) {
basicblock **stack, **sp;
@ -6363,7 +6428,9 @@ static int
optimize_cfg(struct assembler *a, PyObject *consts)
{
for (basicblock *b = a->a_entry; b != NULL; b = b->b_next) {
normalise_basic_block(b);
if (normalize_basic_block(b)) {
return -1;
}
}
for (basicblock *b = a->a_entry; b != NULL; b = b->b_next) {
if (optimize_basic_block(b, consts)) {