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bpo-43754: Eliminate bindings for partial pattern matches (GH-25229)

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Brandt Bucher 2021-05-02 13:02:10 -07:00 • committed by GitHub
parent 7d2b83e9f0
commit 0ad1e0384c
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10 changed files with 575 additions and 345 deletions
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593
Python/compile.c
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@ -230,8 +230,28 @@ struct compiler {
};
typedef struct {
// A list of strings corresponding to name captures. It is used to track:
// - Repeated name assignments in the same pattern.
// - Different name assignments in alternatives.
// - The order of name assignments in alternatives.
PyObject *stores;
// If 0, any name captures against our subject will raise.
int allow_irrefutable;
// An array of blocks to jump to on failure. Jumping to fail_pop[i] will pop
// i items off of the stack. The end result looks like this (with each block
// falling through to the next):
// fail_pop[4]: POP_TOP
// fail_pop[3]: POP_TOP
// fail_pop[2]: POP_TOP
// fail_pop[1]: POP_TOP
// fail_pop[0]: NOP
basicblock **fail_pop;
// The current length of fail_pop.
Py_ssize_t fail_pop_size;
// The number of items on top of the stack that need to *stay* on top of the
// stack. Variable captures go beneath these. All of them will be popped on
// failure.
Py_ssize_t on_top;
} pattern_context;
static int compiler_enter_scope(struct compiler *, identifier, int, void *, int);
@ -1188,6 +1208,8 @@ stack_effect(int opcode, int oparg, int jump)
return 1;
case MATCH_KEYS:
return 2;
case ROT_N:
return 0;
default:
return PY_INVALID_STACK_EFFECT;
}
@ -5594,11 +5616,15 @@ compiler_slice(struct compiler *c, expr_ty s)
// PEP 634: Structural Pattern Matching
// To keep things simple, all compiler_pattern_* routines follow the convention
// of replacing TOS (the subject for the given pattern) with either True (match)
// or False (no match). We do this even for irrefutable patterns; the idea is
// that it's much easier to smooth out any redundant pushing, popping, and
// jumping in the peephole optimizer than to detect or predict it here.
// To keep things simple, all compiler_pattern_* and pattern_helper_* routines
// follow the convention of consuming TOS (the subject for the given pattern)
// and calling jump_to_fail_pop on failure (no match).
// When calling into these routines, it's important that pc->on_top be kept
// updated to reflect the current number of items that we are using on the top
// of the stack: they will be popped on failure, and any name captures will be
// stored *underneath* them on success. This lets us defer all names stores
// until the *entire* pattern matches.
#define WILDCARD_CHECK(N) \
((N)->kind == MatchAs_kind && !(N)->v.MatchAs.name)
@ -5610,6 +5636,72 @@ compiler_slice(struct compiler *c, expr_ty s)
#define MATCH_VALUE_EXPR(N) \
((N)->kind == Constant_kind || (N)->kind == Attribute_kind)
// Allocate or resize pc->fail_pop to allow for n items to be popped on failure.
static int
ensure_fail_pop(struct compiler *c, pattern_context *pc, Py_ssize_t n)
{
Py_ssize_t size = n + 1;
if (size <= pc->fail_pop_size) {
return 1;
}
Py_ssize_t needed = sizeof(basicblock*) * size;
basicblock **resized = PyObject_Realloc(pc->fail_pop, needed);
if (resized == NULL) {
PyErr_NoMemory();
return 0;
}
pc->fail_pop = resized;
while (pc->fail_pop_size < size) {
basicblock *new_block;
RETURN_IF_FALSE(new_block = compiler_new_block(c));
pc->fail_pop[pc->fail_pop_size++] = new_block;
}
return 1;
}
// Use op to jump to the correct fail_pop block.
static int
jump_to_fail_pop(struct compiler *c, pattern_context *pc, int op)
{
// Pop any items on the top of the stack, plus any objects we were going to
// capture on success:
Py_ssize_t pops = pc->on_top + PyList_GET_SIZE(pc->stores);
RETURN_IF_FALSE(ensure_fail_pop(c, pc, pops));
ADDOP_JUMP(c, op, pc->fail_pop[pops]);
NEXT_BLOCK(c);
return 1;
}
// Build all of the fail_pop blocks and reset fail_pop.
static int
emit_and_reset_fail_pop(struct compiler *c, pattern_context *pc)
{
if (!pc->fail_pop_size) {
assert(pc->fail_pop == NULL);
NEXT_BLOCK(c);
return 1;
}
while (--pc->fail_pop_size) {
compiler_use_next_block(c, pc->fail_pop[pc->fail_pop_size]);
if (!compiler_addop(c, POP_TOP)) {
pc->fail_pop_size = 0;
PyObject_Free(pc->fail_pop);
pc->fail_pop = NULL;
return 0;
}
}
compiler_use_next_block(c, pc->fail_pop[0]);
PyObject_Free(pc->fail_pop);
pc->fail_pop = NULL;
return 1;
}
static int
compiler_error_duplicate_store(struct compiler *c, identifier n)
{
return compiler_error(c, "multiple assignments to name %R in pattern", n);
}
static int
pattern_helper_store_name(struct compiler *c, identifier n, pattern_context *pc)
{
@ -5621,22 +5713,16 @@ pattern_helper_store_name(struct compiler *c, identifier n, pattern_context *pc)
return 0;
}
// Can't assign to the same name twice:
if (pc->stores == NULL) {
RETURN_IF_FALSE(pc->stores = PySet_New(NULL));
int duplicate = PySequence_Contains(pc->stores, n);
if (duplicate < 0) {
return 0;
}
else {
int duplicate = PySet_Contains(pc->stores, n);
if (duplicate < 0) {
return 0;
}
if (duplicate) {
const char *e = "multiple assignments to name %R in pattern";
return compiler_error(c, e, n);
}
if (duplicate) {
return compiler_error_duplicate_store(c, n);
}
RETURN_IF_FALSE(!PySet_Add(pc->stores, n));
RETURN_IF_FALSE(compiler_nameop(c, n, Store));
return 1;
// Rotate this object underneath any items we need to preserve:
ADDOP_I(c, ROT_N, pc->on_top + PyList_GET_SIZE(pc->stores) + 1);
return !PyList_Append(pc->stores, n);
}
@ -5672,65 +5758,17 @@ pattern_helper_sequence_unpack(struct compiler *c, asdl_pattern_seq *patterns,
Py_ssize_t star, pattern_context *pc)
{
RETURN_IF_FALSE(pattern_unpack_helper(c, patterns));
// We've now got a bunch of new subjects on the stack. If any of them fail
// to match, we need to pop everything else off, then finally push False.
// fails is an array of blocks that correspond to the necessary amount of
// popping for each element:
basicblock **fails;
Py_ssize_t size = asdl_seq_LEN(patterns);
fails = (basicblock **)PyObject_Malloc(sizeof(basicblock*) * size);
if (fails == NULL) {
PyErr_NoMemory();
return 0;
}
// NOTE: Can't use our nice returning macros anymore: they'll leak memory!
// goto error on error.
for (Py_ssize_t i = 0; i < size; i++) {
fails[i] = compiler_new_block(c);
if (fails[i] == NULL) {
goto error;
}
}
// We've now got a bunch of new subjects on the stack. They need to remain
// there after each subpattern match:
pc->on_top += size;
for (Py_ssize_t i = 0; i < size; i++) {
// One less item to keep track of each time we loop through:
pc->on_top--;
pattern_ty pattern = asdl_seq_GET(patterns, i);
assert((i == star) == (pattern->kind == MatchStar_kind));
if (!compiler_pattern_subpattern(c, pattern, pc) ||
!compiler_addop_j(c, POP_JUMP_IF_FALSE, fails[i]) ||
compiler_next_block(c) == NULL)
{
goto error;
}
RETURN_IF_FALSE(compiler_pattern_subpattern(c, pattern, pc));
}
// Success!
basicblock *end = compiler_new_block(c);
if (end == NULL ||
!compiler_addop_load_const(c, Py_True) ||
!compiler_addop_j(c, JUMP_FORWARD, end))
{
goto error;
}
// This is where we handle failed sub-patterns. For a sequence pattern like
// [a, b, c, d], this will look like:
// fails[0]: POP_TOP
// fails[1]: POP_TOP
// fails[2]: POP_TOP
// fails[3]: LOAD_CONST False
for (Py_ssize_t i = 0; i < size - 1; i++) {
compiler_use_next_block(c, fails[i]);
if (!compiler_addop(c, POP_TOP)) {
goto error;
}
}
compiler_use_next_block(c, fails[size - 1]);
if (!compiler_addop_load_const(c, Py_False)) {
goto error;
}
compiler_use_next_block(c, end);
PyObject_Free(fails);
return 1;
error:
PyObject_Free(fails);
return 0;
}
// Like pattern_helper_sequence_unpack, but uses BINARY_SUBSCR instead of
@ -5740,9 +5778,8 @@ static int
pattern_helper_sequence_subscr(struct compiler *c, asdl_pattern_seq *patterns,
Py_ssize_t star, pattern_context *pc)
{
basicblock *end, *fail_pop_1;
RETURN_IF_FALSE(end = compiler_new_block(c));
RETURN_IF_FALSE(fail_pop_1 = compiler_new_block(c));
// We need to keep the subject around for extracting elements:
pc->on_top++;
Py_ssize_t size = asdl_seq_LEN(patterns);
for (Py_ssize_t i = 0; i < size; i++) {
pattern_ty pattern = asdl_seq_GET(patterns, i);
@ -5766,16 +5803,10 @@ pattern_helper_sequence_subscr(struct compiler *c, asdl_pattern_seq *patterns,
}
ADDOP(c, BINARY_SUBSCR);
RETURN_IF_FALSE(compiler_pattern_subpattern(c, pattern, pc));
ADDOP_JUMP(c, POP_JUMP_IF_FALSE, fail_pop_1);
NEXT_BLOCK(c);
}
// Pop the subject, we're done with it:
pc->on_top--;
ADDOP(c, POP_TOP);
ADDOP_LOAD_CONST(c, Py_True);
ADDOP_JUMP(c, JUMP_FORWARD, end);
compiler_use_next_block(c, fail_pop_1);
ADDOP(c, POP_TOP);
ADDOP_LOAD_CONST(c, Py_False);
compiler_use_next_block(c, end);
return 1;
}
@ -5804,26 +5835,15 @@ compiler_pattern_as(struct compiler *c, pattern_ty p, pattern_context *pc)
const char *e = "wildcard makes remaining patterns unreachable";
return compiler_error(c, e);
}
RETURN_IF_FALSE(pattern_helper_store_name(c, p->v.MatchAs.name, pc));
ADDOP_LOAD_CONST(c, Py_True);
return 1;
return pattern_helper_store_name(c, p->v.MatchAs.name, pc);
}
basicblock *end, *fail_pop_1;
RETURN_IF_FALSE(end = compiler_new_block(c));
RETURN_IF_FALSE(fail_pop_1 = compiler_new_block(c));
// Need to make a copy for (possibly) storing later:
pc->on_top++;
ADDOP(c, DUP_TOP);
RETURN_IF_FALSE(compiler_pattern(c, p->v.MatchAs.pattern, pc));
ADDOP_JUMP(c, POP_JUMP_IF_FALSE, fail_pop_1);
NEXT_BLOCK(c);
// Success! Store it:
pc->on_top--;
RETURN_IF_FALSE(pattern_helper_store_name(c, p->v.MatchAs.name, pc));
ADDOP_LOAD_CONST(c, Py_True);
ADDOP_JUMP(c, JUMP_FORWARD, end);
compiler_use_next_block(c, fail_pop_1);
// Need to pop that unused copy from before:
ADDOP(c, POP_TOP);
ADDOP_LOAD_CONST(c, Py_False);
compiler_use_next_block(c, end);
return 1;
}
@ -5832,7 +5852,6 @@ compiler_pattern_star(struct compiler *c, pattern_ty p, pattern_context *pc)
{
assert(p->kind == MatchStar_kind);
RETURN_IF_FALSE(pattern_helper_store_name(c, p->v.MatchStar.name, pc));
ADDOP_LOAD_CONST(c, Py_True);
return 1;
}
@ -5884,9 +5903,6 @@ compiler_pattern_class(struct compiler *c, pattern_ty p, pattern_context *pc)
RETURN_IF_FALSE(!validate_kwd_attrs(c, kwd_attrs, kwd_patterns));
c->u->u_col_offset = p->col_offset; // validate_kwd_attrs moves this
}
basicblock *end, *fail_pop_1;
RETURN_IF_FALSE(end = compiler_new_block(c));
RETURN_IF_FALSE(fail_pop_1 = compiler_new_block(c));
VISIT(c, expr, p->v.MatchClass.cls);
PyObject *attr_names;
RETURN_IF_FALSE(attr_names = PyTuple_New(nattrs));
@ -5898,9 +5914,9 @@ compiler_pattern_class(struct compiler *c, pattern_ty p, pattern_context *pc)
}
ADDOP_LOAD_CONST_NEW(c, attr_names);
ADDOP_I(c, MATCH_CLASS, nargs);
ADDOP_JUMP(c, POP_JUMP_IF_FALSE, fail_pop_1);
NEXT_BLOCK(c);
// TOS is now a tuple of (nargs + nkwargs) attributes.
// TOS is now a tuple of (nargs + nattrs) attributes. Preserve it:
pc->on_top++;
RETURN_IF_FALSE(jump_to_fail_pop(c, pc, POP_JUMP_IF_FALSE));
for (i = 0; i < nargs + nattrs; i++) {
pattern_ty pattern;
if (i < nargs) {
@ -5919,17 +5935,10 @@ compiler_pattern_class(struct compiler *c, pattern_ty p, pattern_context *pc)
ADDOP_LOAD_CONST_NEW(c, PyLong_FromSsize_t(i));
ADDOP(c, BINARY_SUBSCR);
RETURN_IF_FALSE(compiler_pattern_subpattern(c, pattern, pc));
ADDOP_JUMP(c, POP_JUMP_IF_FALSE, fail_pop_1);
NEXT_BLOCK(c);
}
// Success! Pop the tuple of attributes:
pc->on_top--;
ADDOP(c, POP_TOP);
ADDOP_LOAD_CONST(c, Py_True);
ADDOP_JUMP(c, JUMP_FORWARD, end);
compiler_use_next_block(c, fail_pop_1);
ADDOP(c, POP_TOP);
ADDOP_LOAD_CONST(c, Py_False);
compiler_use_next_block(c, end);
return 1;
}
@ -5937,10 +5946,6 @@ static int
compiler_pattern_mapping(struct compiler *c, pattern_ty p, pattern_context *pc)
{
assert(p->kind == MatchMapping_kind);
basicblock *end, *fail_pop_1, *fail_pop_3;
RETURN_IF_FALSE(end = compiler_new_block(c));
RETURN_IF_FALSE(fail_pop_1 = compiler_new_block(c));
RETURN_IF_FALSE(fail_pop_3 = compiler_new_block(c));
asdl_expr_seq *keys = p->v.MatchMapping.keys;
asdl_pattern_seq *patterns = p->v.MatchMapping.patterns;
Py_ssize_t size = asdl_seq_LEN(keys);
@ -5953,18 +5958,14 @@ compiler_pattern_mapping(struct compiler *c, pattern_ty p, pattern_context *pc)
}
// We have a double-star target if "rest" is set
PyObject *star_target = p->v.MatchMapping.rest;
// We need to keep the subject on top during the mapping and length checks:
pc->on_top++;
ADDOP(c, MATCH_MAPPING);
ADDOP_JUMP(c, POP_JUMP_IF_FALSE, fail_pop_1);
NEXT_BLOCK(c);
RETURN_IF_FALSE(jump_to_fail_pop(c, pc, POP_JUMP_IF_FALSE));
if (!size && !star_target) {
// If the pattern is just "{}", we're done!
// If the pattern is just "{}", we're done! Pop the subject:
pc->on_top--;
ADDOP(c, POP_TOP);
ADDOP_LOAD_CONST(c, Py_True);
ADDOP_JUMP(c, JUMP_FORWARD, end);
compiler_use_next_block(c, fail_pop_1);
ADDOP(c, POP_TOP);
ADDOP_LOAD_CONST(c, Py_False);
compiler_use_next_block(c, end);
return 1;
}
if (size) {
@ -5972,8 +5973,7 @@ compiler_pattern_mapping(struct compiler *c, pattern_ty p, pattern_context *pc)
ADDOP(c, GET_LEN);
ADDOP_LOAD_CONST_NEW(c, PyLong_FromSsize_t(size));
ADDOP_COMPARE(c, GtE);
ADDOP_JUMP(c, POP_JUMP_IF_FALSE, fail_pop_1);
NEXT_BLOCK(c);
RETURN_IF_FALSE(jump_to_fail_pop(c, pc, POP_JUMP_IF_FALSE));
}
if (INT_MAX < size - 1) {
return compiler_error(c, "too many sub-patterns in mapping pattern");
@ -5996,9 +5996,10 @@ compiler_pattern_mapping(struct compiler *c, pattern_ty p, pattern_context *pc)
}
ADDOP_I(c, BUILD_TUPLE, size);
ADDOP(c, MATCH_KEYS);
ADDOP_JUMP(c, POP_JUMP_IF_FALSE, fail_pop_3);
NEXT_BLOCK(c);
// So far so good. There's now a tuple of values on the stack to match
// There's now a tuple of keys and a tuple of values on top of the subject:
pc->on_top += 2;
RETURN_IF_FALSE(jump_to_fail_pop(c, pc, POP_JUMP_IF_FALSE));
// So far so good. Use that tuple of values on the stack to match
// sub-patterns against:
for (Py_ssize_t i = 0; i < size; i++) {
pattern_ty pattern = asdl_seq_GET(patterns, i);
@ -6009,10 +6010,10 @@ compiler_pattern_mapping(struct compiler *c, pattern_ty p, pattern_context *pc)
ADDOP_LOAD_CONST_NEW(c, PyLong_FromSsize_t(i));
ADDOP(c, BINARY_SUBSCR);
RETURN_IF_FALSE(compiler_pattern_subpattern(c, pattern, pc));
ADDOP_JUMP(c, POP_JUMP_IF_FALSE, fail_pop_3);
NEXT_BLOCK(c);
}
// If we get this far, it's a match! We're done with that tuple of values.
// If we get this far, it's a match! We're done with the tuple of values,
// and whatever happens next should consume the tuple of keys underneath it:
pc->on_top -= 2;
ADDOP(c, POP_TOP);
if (star_target) {
// If we have a starred name, bind a dict of remaining items to it:
@ -6024,19 +6025,8 @@ compiler_pattern_mapping(struct compiler *c, pattern_ty p, pattern_context *pc)
ADDOP(c, POP_TOP);
}
// Pop the subject:
pc->on_top--;
ADDOP(c, POP_TOP);
ADDOP_LOAD_CONST(c, Py_True);
ADDOP_JUMP(c, JUMP_FORWARD, end);
// The top two items are a tuple of values or None, followed by a tuple of
// keys. Pop them both:
compiler_use_next_block(c, fail_pop_3);
ADDOP(c, POP_TOP);
ADDOP(c, POP_TOP);
compiler_use_next_block(c, fail_pop_1);
// Pop the subject:
ADDOP(c, POP_TOP);
ADDOP_LOAD_CONST(c, Py_False);
compiler_use_next_block(c, end);
return 1;
}
@ -6044,69 +6034,148 @@ static int
compiler_pattern_or(struct compiler *c, pattern_ty p, pattern_context *pc)
{
assert(p->kind == MatchOr_kind);
// control is the set of names bound by the first alternative. If all of the
// others bind the same names (they should), then this becomes pc->stores.
PyObject *control = NULL;
basicblock *end, *pass_pop_1;
basicblock *end;
RETURN_IF_FALSE(end = compiler_new_block(c));
RETURN_IF_FALSE(pass_pop_1 = compiler_new_block(c));
Py_ssize_t size = asdl_seq_LEN(p->v.MatchOr.patterns);
assert(size > 1);
// We're going to be messing with pc. Keep the original info handy:
PyObject *stores_init = pc->stores;
int allow_irrefutable = pc->allow_irrefutable;
pattern_context old_pc = *pc;
Py_INCREF(pc->stores);
// control is the list of names bound by the first alternative. It is used
// for checking different name bindings in alternatives, and for correcting
// the order in which extracted elements are placed on the stack.
PyObject *control = NULL;
// NOTE: We can't use returning macros anymore! goto error on error.
for (Py_ssize_t i = 0; i < size; i++) {
// NOTE: Can't use our nice returning macros in here: they'll leak sets!
pattern_ty alt = asdl_seq_GET(p->v.MatchOr.patterns, i);
pc->stores = PySet_New(stores_init);
// An irrefutable sub-pattern must be last, if it is allowed at all:
int is_last = i == size - 1;
pc->allow_irrefutable = allow_irrefutable && is_last;
SET_LOC(c, alt);
if (pc->stores == NULL ||
// Only copy the subject if we're *not* on the last alternative:
(!is_last && !compiler_addop(c, DUP_TOP)) ||
!compiler_pattern(c, alt, pc) ||
// Only jump if we're *not* on the last alternative:
(!is_last && !compiler_addop_j(c, POP_JUMP_IF_TRUE, pass_pop_1)) ||
!compiler_next_block(c))
{
goto fail;
PyObject *pc_stores = PyList_New(0);
if (pc_stores == NULL) {
goto error;
}
Py_SETREF(pc->stores, pc_stores);
// An irrefutable sub-pattern must be last, if it is allowed at all:
pc->allow_irrefutable = (i == size - 1) && old_pc.allow_irrefutable;
pc->fail_pop = NULL;
pc->fail_pop_size = 0;
pc->on_top = 0;
if (!compiler_addop(c, DUP_TOP) || !compiler_pattern(c, alt, pc)) {
goto error;
}
// Success!
Py_ssize_t nstores = PyList_GET_SIZE(pc->stores);
if (!i) {
// If this is the first alternative, save its stores as a "control"
// for the others (they can't bind a different set of names):
// This is the first alternative, so save its stores as a "control"
// for the others (they can't bind a different set of names, and
// might need to be reordered):
assert(control == NULL);
control = pc->stores;
continue;
Py_INCREF(control);
}
if (PySet_GET_SIZE(pc->stores) || PySet_GET_SIZE(control)) {
// Otherwise, check to see if we differ from the control set:
PyObject *diff = PyNumber_InPlaceXor(pc->stores, control);
if (diff == NULL) {
goto fail;
}
if (PySet_GET_SIZE(diff)) {
// The names differ! Raise.
Py_DECREF(diff);
compiler_error(c, "alternative patterns bind different names");
goto fail;
}
Py_DECREF(diff);
else if (nstores != PyList_GET_SIZE(control)) {
goto diff;
}
else if (nstores) {
// There were captures. Check to see if we differ from control:
Py_ssize_t icontrol = nstores;
while (icontrol--) {
PyObject *name = PyList_GET_ITEM(control, icontrol);
Py_ssize_t istores = PySequence_Index(pc->stores, name);
if (istores < 0) {
PyErr_Clear();
goto diff;
}
if (icontrol != istores) {
// Reorder the names on the stack to match the order of the
// names in control. There's probably a better way of doing
// this; the current solution is potentially very
// inefficient when each alternative subpattern binds lots
// of names in different orders. It's fine for reasonable
// cases, though.
assert(istores < icontrol);
Py_ssize_t rotations = istores + 1;
// Perfom the same rotation on pc->stores:
PyObject *rotated = PyList_GetSlice(pc->stores, 0,
rotations);
if (rotated == NULL ||
PyList_SetSlice(pc->stores, 0, rotations, NULL) ||
PyList_SetSlice(pc->stores, icontrol - istores,
icontrol - istores, rotated))
{
Py_XDECREF(rotated);
goto error;
}
Py_DECREF(rotated);
// That just did:
// rotated = pc_stores[:rotations]
// del pc_stores[:rotations]
// pc_stores[icontrol-istores:icontrol-istores] = rotated
// Do the same thing to the stack, using several ROT_Ns:
while (rotations--) {
if (!compiler_addop_i(c, ROT_N, icontrol + 1)) {
goto error;
}
}
}
}
}
assert(control);
if (!compiler_addop_j(c, JUMP_FORWARD, end) ||
!compiler_next_block(c) ||
!emit_and_reset_fail_pop(c, pc))
{
goto error;
}
Py_DECREF(pc->stores);
}
Py_XDECREF(stores_init);
// Update pc->stores and restore pc->allow_irrefutable:
pc->stores = control;
pc->allow_irrefutable = allow_irrefutable;
ADDOP_JUMP(c, JUMP_FORWARD, end);
compiler_use_next_block(c, pass_pop_1);
ADDOP(c, POP_TOP);
ADDOP_LOAD_CONST(c, Py_True);
Py_DECREF(pc->stores);
*pc = old_pc;
Py_INCREF(pc->stores);
// Need to NULL this for the PyObject_Free call in the error block.
old_pc.fail_pop = NULL;
// No match. Pop the remaining copy of the subject and fail:
if (!compiler_addop(c, POP_TOP) || !jump_to_fail_pop(c, pc, JUMP_FORWARD)) {
goto error;
}
compiler_use_next_block(c, end);
Py_ssize_t nstores = PyList_GET_SIZE(control);
// There's a bunch of stuff on the stack between any where the new stores
// are and where they need to be:
// - The other stores.
// - A copy of the subject.
// - Anything else that may be on top of the stack.
// - Any previous stores we've already stashed away on the stack.
int nrots = nstores + 1 + pc->on_top + PyList_GET_SIZE(pc->stores);
for (Py_ssize_t i = 0; i < nstores; i++) {
// Rotate this capture to its proper place on the stack:
if (!compiler_addop_i(c, ROT_N, nrots)) {
goto error;
}
// Update the list of previous stores with this new name, checking for
// duplicates:
PyObject *name = PyList_GET_ITEM(control, i);
int dupe = PySequence_Contains(pc->stores, name);
if (dupe < 0) {
goto error;
}
if (dupe) {
compiler_error_duplicate_store(c, name);
goto error;
}
if (PyList_Append(pc->stores, name)) {
goto error;
}
}
Py_DECREF(old_pc.stores);
Py_DECREF(control);
// NOTE: Returning macros are safe again.
// Pop the copy of the subject:
ADDOP(c, POP_TOP);
return 1;
fail:
Py_XDECREF(stores_init);
diff:
compiler_error(c, "alternative patterns bind different names");
error:
PyObject_Free(old_pc.fail_pop);
Py_DECREF(old_pc.stores);
Py_XDECREF(control);
return 0;
}
@ -6136,32 +6205,29 @@ compiler_pattern_sequence(struct compiler *c, pattern_ty p, pattern_context *pc)
}
only_wildcard &= WILDCARD_CHECK(pattern);
}
basicblock *end, *fail_pop_1;
RETURN_IF_FALSE(end = compiler_new_block(c));
RETURN_IF_FALSE(fail_pop_1 = compiler_new_block(c));
// We need to keep the subject on top during the sequence and length checks:
pc->on_top++;
ADDOP(c, MATCH_SEQUENCE);
ADDOP_JUMP(c, POP_JUMP_IF_FALSE, fail_pop_1);
NEXT_BLOCK(c);
RETURN_IF_FALSE(jump_to_fail_pop(c, pc, POP_JUMP_IF_FALSE));
if (star < 0) {
// No star: len(subject) == size
ADDOP(c, GET_LEN);
ADDOP_LOAD_CONST_NEW(c, PyLong_FromSsize_t(size));
ADDOP_COMPARE(c, Eq);
ADDOP_JUMP(c, POP_JUMP_IF_FALSE, fail_pop_1);
NEXT_BLOCK(c);
RETURN_IF_FALSE(jump_to_fail_pop(c, pc, POP_JUMP_IF_FALSE));
}
else if (size > 1) {
// Star: len(subject) >= size - 1
ADDOP(c, GET_LEN);
ADDOP_LOAD_CONST_NEW(c, PyLong_FromSsize_t(size - 1));
ADDOP_COMPARE(c, GtE);
ADDOP_JUMP(c, POP_JUMP_IF_FALSE, fail_pop_1);
NEXT_BLOCK(c);
RETURN_IF_FALSE(jump_to_fail_pop(c, pc, POP_JUMP_IF_FALSE));
}
// Whatever comes next should consume the subject:
pc->on_top--;
if (only_wildcard) {
// Patterns like: [] / [_] / [_, _] / [*_] / [_, *_] / [_, _, *_] / etc.
ADDOP(c, POP_TOP);
ADDOP_LOAD_CONST(c, Py_True);
}
else if (star_wildcard) {
RETURN_IF_FALSE(pattern_helper_sequence_subscr(c, patterns, star, pc));
@ -6169,11 +6235,6 @@ compiler_pattern_sequence(struct compiler *c, pattern_ty p, pattern_context *pc)
else {
RETURN_IF_FALSE(pattern_helper_sequence_unpack(c, patterns, star, pc));
}
ADDOP_JUMP(c, JUMP_FORWARD, end);
compiler_use_next_block(c, fail_pop_1);
ADDOP(c, POP_TOP)
ADDOP_LOAD_CONST(c, Py_False);
compiler_use_next_block(c, end);
return 1;
}
@ -6188,6 +6249,7 @@ compiler_pattern_value(struct compiler *c, pattern_ty p, pattern_context *pc)
}
VISIT(c, expr, value);
ADDOP_COMPARE(c, Eq);
RETURN_IF_FALSE(jump_to_fail_pop(c, pc, POP_JUMP_IF_FALSE));
return 1;
}
@ -6197,6 +6259,7 @@ compiler_pattern_singleton(struct compiler *c, pattern_ty p, pattern_context *pc
assert(p->kind == MatchSingleton_kind);
ADDOP_LOAD_CONST(c, p->v.MatchSingleton.value);
ADDOP_COMPARE(c, Is);
RETURN_IF_FALSE(jump_to_fail_pop(c, pc, POP_JUMP_IF_FALSE));
return 1;
}
@ -6229,39 +6292,48 @@ compiler_pattern(struct compiler *c, pattern_ty p, pattern_context *pc)
}
static int
compiler_match(struct compiler *c, stmt_ty s)
compiler_match_inner(struct compiler *c, stmt_ty s, pattern_context *pc)
{
VISIT(c, expr, s->v.Match.subject);
basicblock *next, *end;
basicblock *end;
RETURN_IF_FALSE(end = compiler_new_block(c));
Py_ssize_t cases = asdl_seq_LEN(s->v.Match.cases);
assert(cases > 0);
pattern_context pc;
// We use pc.stores to track:
// - Repeated name assignments in the same pattern.
// - Different name assignments in alternatives.
// It's a set of names, but we don't create it until it's needed:
pc.stores = NULL;
match_case_ty m = asdl_seq_GET(s->v.Match.cases, cases - 1);
int has_default = WILDCARD_CHECK(m->pattern) && 1 < cases;
for (Py_ssize_t i = 0; i < cases - has_default; i++) {
m = asdl_seq_GET(s->v.Match.cases, i);
SET_LOC(c, m->pattern);
RETURN_IF_FALSE(next = compiler_new_block(c));
// If pc.allow_irrefutable is 0, any name captures against our subject
// will raise. Irrefutable cases must be either guarded, last, or both:
pc.allow_irrefutable = m->guard != NULL || i == cases - 1;
// Only copy the subject if we're *not* on the last case:
if (i != cases - has_default - 1) {
ADDOP(c, DUP_TOP);
}
int result = compiler_pattern(c, m->pattern, &pc);
Py_CLEAR(pc.stores);
RETURN_IF_FALSE(result);
ADDOP_JUMP(c, POP_JUMP_IF_FALSE, next);
NEXT_BLOCK(c);
RETURN_IF_FALSE(pc->stores = PyList_New(0));
// Irrefutable cases must be either guarded, last, or both:
pc->allow_irrefutable = m->guard != NULL || i == cases - 1;
pc->fail_pop = NULL;
pc->fail_pop_size = 0;
pc->on_top = 0;
// NOTE: Can't use returning macros here (they'll leak pc->stores)!
if (!compiler_pattern(c, m->pattern, pc)) {
Py_DECREF(pc->stores);
return 0;
}
assert(!pc->on_top);
// It's a match! Store all of the captured names (they're on the stack).
Py_ssize_t nstores = PyList_GET_SIZE(pc->stores);
for (Py_ssize_t n = 0; n < nstores; n++) {
PyObject *name = PyList_GET_ITEM(pc->stores, n);
if (!compiler_nameop(c, name, Store)) {
Py_DECREF(pc->stores);
return 0;
}
}
Py_DECREF(pc->stores);
// NOTE: Returning macros are safe again.
if (m->guard) {
RETURN_IF_FALSE(compiler_jump_if(c, m->guard, next, 0));
RETURN_IF_FALSE(ensure_fail_pop(c, pc, 0));
RETURN_IF_FALSE(compiler_jump_if(c, m->guard, pc->fail_pop[0], 0));
}
// Success! Pop the subject off, we're done with it:
if (i != cases - has_default - 1) {
@ -6269,7 +6341,7 @@ compiler_match(struct compiler *c, stmt_ty s)
}
VISIT_SEQ(c, stmt, m->body);
ADDOP_JUMP(c, JUMP_FORWARD, end);
compiler_use_next_block(c, next);
RETURN_IF_FALSE(emit_and_reset_fail_pop(c, pc));
}
if (has_default) {
if (cases == 1) {
@ -6289,6 +6361,16 @@ compiler_match(struct compiler *c, stmt_ty s)
return 1;
}
static int
compiler_match(struct compiler *c, stmt_ty s)
{
pattern_context pc;
pc.fail_pop = NULL;
int result = compiler_match_inner(c, s, &pc);
PyObject_Free(pc.fail_pop);
return result;
}
#undef WILDCARD_CHECK
#undef WILDCARD_STAR_CHECK
@ -7031,6 +7113,38 @@ fold_tuple_on_constants(struct compiler *c,
}
// Eliminate n * ROT_N(n).
static void
fold_rotations(struct instr *inst, int n)
{
for (int i = 0; i < n; i++) {
int rot;
switch (inst[i].i_opcode) {
case ROT_N:
rot = inst[i].i_oparg;
break;
case ROT_FOUR:
rot = 4;
break;
case ROT_THREE:
rot = 3;
break;
case ROT_TWO:
rot = 2;
break;
default:
return;
}
if (rot != n) {
return;
}
}
for (int i = 0; i < n; i++) {
inst[i].i_opcode = NOP;
}
}
static int
eliminate_jump_to_jump(basicblock *bb, int opcode) {
assert (bb->b_iused > 0);
@ -7273,6 +7387,27 @@ optimize_basic_block(struct compiler *c, basicblock *bb, PyObject *consts)
bb->b_exit = 1;
}
}
break;
case ROT_N:
switch (oparg) {
case 0:
case 1:
inst->i_opcode = NOP;
continue;
case 2:
inst->i_opcode = ROT_TWO;
break;
case 3:
inst->i_opcode = ROT_THREE;
break;
case 4:
inst->i_opcode = ROT_FOUR;
break;
}
if (i >= oparg - 1) {
fold_rotations(inst - oparg + 1, oparg);
}
break;
}
}
return 0;