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Implement ??= operator

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RFC: https://wiki.php.net/rfc/null_coalesce_equal_operator

$a ??= $b is $a ?? ($a = $b), with the difference that $a is only
evaluated once, to the degree that this is possible. In particular
in $a[foo()] ?? $b function foo() is only ever called once.
However, the variable access themselves will be reevaluated.
This commit is contained in:
Nikita Popov 2019-01-15 17:04:24 +01:00
parent 50ddff94b9
commit a50198d0fe
23 changed files with 1068 additions and 517 deletions
Download patch file Download diff file Expand all files Collapse all files

69
Zend/zend_opcode.c
View file

@ -547,12 +547,27 @@ static uint32_t zend_get_brk_cont_target(const zend_op_array *op_array, const ze
return opline->opcode == ZEND_BRK ? jmp_to->brk : jmp_to->cont;
}
static void emit_live_range_raw(
zend_op_array *op_array, uint32_t var_num, uint32_t kind, uint32_t start, uint32_t end) {
zend_live_range *range;
op_array->last_live_range++;
op_array->live_range = erealloc(op_array->live_range,
sizeof(zend_live_range) * op_array->last_live_range);
ZEND_ASSERT(start < end);
range = &op_array->live_range[op_array->last_live_range - 1];
range->var = (uint32_t) (intptr_t) ZEND_CALL_VAR_NUM(NULL, op_array->last_var + var_num);
range->var |= kind;
range->start = start;
range->end = end;
}
static void emit_live_range(
zend_op_array *op_array, uint32_t var_num, uint32_t start, uint32_t end,
zend_needs_live_range_cb needs_live_range) {
zend_op *def_opline = &op_array->opcodes[start], *orig_def_opline = def_opline;
zend_op *use_opline = &op_array->opcodes[end];
zend_live_range *range;
uint32_t kind;
switch (def_opline->opcode) {
@ -589,7 +604,8 @@ static void emit_live_range(
break;
/* Objects created via ZEND_NEW are only fully initialized
* after the DO_FCALL (constructor call). */
case ZEND_NEW: {
case ZEND_NEW:
{
int level = 0;
while (def_opline + 1 < use_opline) {
def_opline++;
@ -629,6 +645,41 @@ static void emit_live_range(
kind = ZEND_LIVE_TMPVAR;
break;
}
case ZEND_COPY_TMP:
{
/* COPY_TMP has a split live-range: One from the definition until the use in
* "null" branch, and another from the start of the "non-null" branch to the
* FREE opcode. */
uint32_t rt_var_num =
(uint32_t) (intptr_t) ZEND_CALL_VAR_NUM(NULL, op_array->last_var + var_num);
zend_op *block_start_op = use_opline;
if (needs_live_range && !needs_live_range(op_array, orig_def_opline)) {
return;
}
while ((block_start_op-1)->opcode == ZEND_FREE) {
block_start_op--;
}
kind = ZEND_LIVE_TMPVAR;
start = block_start_op - op_array->opcodes;
if (start != end) {
emit_live_range_raw(op_array, var_num, kind, start, end);
}
do {
use_opline--;
} while (!(
((use_opline->op1_type & (IS_TMP_VAR|IS_VAR)) && use_opline->op1.var == rt_var_num) ||
((use_opline->op2_type & (IS_TMP_VAR|IS_VAR)) && use_opline->op2.var == rt_var_num)
));
start = def_opline + 1 - op_array->opcodes;
end = use_opline - op_array->opcodes;
emit_live_range_raw(op_array, var_num, kind, start, end);
return;
}
}
/* Check hook to determine whether a live range is necessary, e.g. based on type info. */
@ -636,16 +687,7 @@ static void emit_live_range(
return;
}
op_array->last_live_range++;
op_array->live_range = erealloc(op_array->live_range,
sizeof(zend_live_range) * op_array->last_live_range);
ZEND_ASSERT(start < end);
range = &op_array->live_range[op_array->last_live_range - 1];
range->var = (uint32_t) (intptr_t) ZEND_CALL_VAR_NUM(NULL, op_array->last_var + var_num);
range->var |= kind;
range->start = start;
range->end = end;
emit_live_range_raw(op_array, var_num, kind, start, end);
}
static zend_bool is_fake_def(zend_op *opline) {
@ -659,7 +701,8 @@ static zend_bool keeps_op1_alive(zend_op *opline) {
* it is later freed by something else. */
if (opline->opcode == ZEND_CASE
|| opline->opcode == ZEND_SWITCH_LONG
|| opline->opcode == ZEND_FETCH_LIST_R) {
|| opline->opcode == ZEND_FETCH_LIST_R
|| opline->opcode == ZEND_COPY_TMP) {
return 1;
}
ZEND_ASSERT(opline->opcode != ZEND_SWITCH_STRING