Hugging Face's logo

Datasets:
meddyrat
/
dis-bench

Modalities:
Tabular
Text
Formats:
parquet
Size:
1K - 10K
Libraries:
Datasets
pandas
Polars
Dataset card Data Studio Files
xet
 Community
1
dis-bench / src /php /php-src /Zend /Optimizer /dce.c
meddyrat's picture
meddyrat
Replace repository contents with the original corrected artifact
1e94262
Raw History Blame Contribute Delete
23 kB
/*
+----------------------------------------------------------------------+
| Zend Engine, DCE - Dead Code Elimination |
+----------------------------------------------------------------------+
| Copyright (c) The PHP Group |
+----------------------------------------------------------------------+
| This source file is subject to version 3.01 of the PHP license, |
| that is bundled with this package in the file LICENSE, and is |
| available through the world-wide-web at the following url: |
| https://www.php.net/license/3_01.txt |
| If you did not receive a copy of the PHP license and are unable to |
| obtain it through the world-wide-web, please send a note to |
| license@php.net so we can mail you a copy immediately. |
+----------------------------------------------------------------------+
| Authors: Nikita Popov <nikic@php.net> |
| Dmitry Stogov <dmitry@php.net> |
+----------------------------------------------------------------------+
*/
#include "Optimizer/zend_optimizer_internal.h"
#include "Optimizer/zend_inference.h"
#include "Optimizer/zend_ssa.h"
#include "Optimizer/zend_func_info.h"
#include "Optimizer/zend_call_graph.h"
#include "zend_bitset.h"
/* This pass implements a form of dead code elimination (DCE). The algorithm optimistically assumes
* that all instructions and phis are dead. Instructions with immediate side-effects are then marked
* as live. We then recursively (using a worklist) propagate liveness to the instructions that def
* the used operands.
*
* Notes:
* * This pass does not perform unreachable code elimination. This happens as part of the SCCP
* pass.
* * The DCE is performed without taking control-dependence into account, i.e. all conditional
* branches are assumed to be live. It's possible to take control-dependence into account using
* the DCE algorithm described by Cytron et al., however it requires the construction of a
* postdominator tree and of postdominance frontiers, which does not seem worthwhile at this
* point.
* * We separate intrinsic side-effects from potential side-effects in the form of notices thrown
* by the instruction (in case we want to make this configurable). See may_have_side_effects() and
* zend_may_throw().
* * We often cannot DCE assignments and unsets while guaranteeing that dtors run in the same
* order. There is an optimization option to allow reordering of dtor effects.
* * The algorithm is able to eliminate dead modifications of non-escaping arrays
* and objects as well as dead arrays and objects allocations.
*/
typedef struct {
zend_ssa *ssa;
zend_op_array *op_array;
zend_bitset instr_dead;
zend_bitset phi_dead;
zend_bitset instr_worklist;
zend_bitset phi_worklist;
zend_bitset phi_worklist_no_val;
uint32_t instr_worklist_len;
uint32_t phi_worklist_len;
unsigned reorder_dtor_effects : 1;
} context;
static inline bool is_bad_mod(const zend_ssa *ssa, int use, int def) {
if (def < 0) {
/* This modification is not tracked by SSA, assume the worst */
return 1;
}
if (ssa->var_info[use].type & MAY_BE_REF) {
/* Modification of reference may have side-effect */
return 1;
}
return 0;
}
static inline bool may_have_side_effects(
zend_op_array *op_array, zend_ssa *ssa,
const zend_op *opline, const zend_ssa_op *ssa_op,
bool reorder_dtor_effects) {
switch (opline->opcode) {
case ZEND_NOP:
case ZEND_IS_IDENTICAL:
case ZEND_IS_NOT_IDENTICAL:
case ZEND_QM_ASSIGN:
case ZEND_FE_FREE:
case ZEND_TYPE_CHECK:
case ZEND_DEFINED:
case ZEND_ADD:
case ZEND_SUB:
case ZEND_MUL:
case ZEND_POW:
case ZEND_BW_OR:
case ZEND_BW_AND:
case ZEND_BW_XOR:
case ZEND_CONCAT:
case ZEND_FAST_CONCAT:
case ZEND_DIV:
case ZEND_MOD:
case ZEND_BOOL_XOR:
case ZEND_BOOL:
case ZEND_BOOL_NOT:
case ZEND_BW_NOT:
case ZEND_SL:
case ZEND_SR:
case ZEND_IS_EQUAL:
case ZEND_IS_NOT_EQUAL:
case ZEND_IS_SMALLER:
case ZEND_IS_SMALLER_OR_EQUAL:
case ZEND_CASE:
case ZEND_CASE_STRICT:
case ZEND_CAST:
case ZEND_ROPE_INIT:
case ZEND_ROPE_ADD:
case ZEND_INIT_ARRAY:
case ZEND_SPACESHIP:
case ZEND_STRLEN:
case ZEND_COUNT:
case ZEND_GET_TYPE:
case ZEND_ISSET_ISEMPTY_THIS:
case ZEND_ISSET_ISEMPTY_DIM_OBJ:
case ZEND_FETCH_DIM_IS:
case ZEND_ISSET_ISEMPTY_CV:
case ZEND_ISSET_ISEMPTY_VAR:
case ZEND_FETCH_IS:
case ZEND_IN_ARRAY:
case ZEND_FUNC_NUM_ARGS:
case ZEND_FUNC_GET_ARGS:
case ZEND_ARRAY_KEY_EXISTS:
/* No side effects */
return 0;
case ZEND_FREE:
return opline->extended_value == ZEND_FREE_VOID_CAST;
case ZEND_ADD_ARRAY_ELEMENT:
/* TODO: We can't free two vars. Keep instruction alive. <?php [0, "$a" => "$b"]; */
if ((opline->op1_type & (IS_VAR|IS_TMP_VAR)) && (opline->op2_type & (IS_VAR|IS_TMP_VAR))) {
return 1;
}
return 0;
case ZEND_ROPE_END:
/* TODO: Rope dce optimization, see #76446 */
return 1;
case ZEND_JMP:
case ZEND_JMPZ:
case ZEND_JMPNZ:
case ZEND_JMPZ_EX:
case ZEND_JMPNZ_EX:
case ZEND_JMP_SET:
case ZEND_COALESCE:
case ZEND_ASSERT_CHECK:
case ZEND_JMP_NULL:
case ZEND_BIND_INIT_STATIC_OR_JMP:
case ZEND_JMP_FRAMELESS:
/* For our purposes a jumps and branches are side effects. */
return 1;
case ZEND_BEGIN_SILENCE:
case ZEND_END_SILENCE:
case ZEND_ECHO:
case ZEND_INCLUDE_OR_EVAL:
case ZEND_THROW:
case ZEND_MATCH_ERROR:
case ZEND_EXT_STMT:
case ZEND_EXT_FCALL_BEGIN:
case ZEND_EXT_FCALL_END:
case ZEND_TICKS:
case ZEND_YIELD:
case ZEND_YIELD_FROM:
case ZEND_VERIFY_NEVER_TYPE:
/* Intrinsic side effects */
return 1;
case ZEND_DO_FCALL:
case ZEND_DO_FCALL_BY_NAME:
case ZEND_DO_ICALL:
case ZEND_DO_UCALL:
case ZEND_FRAMELESS_ICALL_0:
case ZEND_FRAMELESS_ICALL_1:
case ZEND_FRAMELESS_ICALL_2:
case ZEND_FRAMELESS_ICALL_3:
/* For now assume all calls have side effects */
return 1;
case ZEND_RECV:
case ZEND_RECV_INIT:
/* Even though RECV_INIT can be side-effect free, these cannot be simply dropped
* due to the prologue skipping code. */
return 1;
case ZEND_ASSIGN_REF:
return 1;
case ZEND_ASSIGN:
{
if (is_bad_mod(ssa, ssa_op->op1_use, ssa_op->op1_def)) {
return 1;
}
if (!reorder_dtor_effects) {
if (opline->op2_type != IS_CONST
&& (OP2_INFO() & MAY_HAVE_DTOR)
&& ssa->vars[ssa_op->op2_use].escape_state != ESCAPE_STATE_NO_ESCAPE) {
/* DCE might shorten lifetime */
return 1;
}
}
return 0;
}
case ZEND_UNSET_VAR:
return 1;
case ZEND_UNSET_CV:
{
uint32_t t1 = OP1_INFO();
if (t1 & MAY_BE_REF) {
/* We don't consider uses as the LHS of an assignment as real uses during DCE, so
* an unset may be considered dead even if there is a later assignment to the
* variable. Removing the unset in this case would not be correct if the variable
* is a reference, because unset breaks references. */
return 1;
}
return 0;
}
case ZEND_PRE_INC:
case ZEND_POST_INC:
case ZEND_PRE_DEC:
case ZEND_POST_DEC:
return is_bad_mod(ssa, ssa_op->op1_use, ssa_op->op1_def);
case ZEND_ASSIGN_OP:
return is_bad_mod(ssa, ssa_op->op1_use, ssa_op->op1_def)
|| ssa->vars[ssa_op->op1_def].escape_state != ESCAPE_STATE_NO_ESCAPE;
case ZEND_ASSIGN_DIM:
case ZEND_ASSIGN_OBJ:
if (is_bad_mod(ssa, ssa_op->op1_use, ssa_op->op1_def)
|| ssa->vars[ssa_op->op1_def].escape_state != ESCAPE_STATE_NO_ESCAPE) {
return 1;
}
if (!reorder_dtor_effects) {
opline++;
ssa_op++;
if (opline->op1_type != IS_CONST
&& (OP1_INFO() & MAY_HAVE_DTOR)) {
/* DCE might shorten lifetime */
return 1;
}
}
return 0;
case ZEND_PRE_INC_OBJ:
case ZEND_PRE_DEC_OBJ:
case ZEND_POST_INC_OBJ:
case ZEND_POST_DEC_OBJ:
if (is_bad_mod(ssa, ssa_op->op1_use, ssa_op->op1_def)
|| ssa->vars[ssa_op->op1_def].escape_state != ESCAPE_STATE_NO_ESCAPE) {
return 1;
}
return 0;
case ZEND_BIND_STATIC:
if (op_array->static_variables) {
/* Implicit and Explicit bind static is effectively prologue of closure so
report it has side effects like RECV, RECV_INIT; This allows us to
reflect on the closure and discover used variable at runtime */
if ((opline->extended_value & (ZEND_BIND_IMPLICIT|ZEND_BIND_EXPLICIT))) {
return 1;
}
/* Modifies static variables which are observable through reflection */
if ((opline->extended_value & ZEND_BIND_REF) && opline->op2_type != IS_UNUSED) {
return 1;
}
}
return 0;
case ZEND_CHECK_VAR:
return (OP1_INFO() & MAY_BE_UNDEF) != 0;
case ZEND_FE_RESET_R:
case ZEND_FE_RESET_RW:
/* Model as not having side-effects -- let the side-effect be introduced by
* FE_FETCH if the array is not known to be non-empty. */
return (OP1_INFO() & MAY_BE_ANY) != MAY_BE_ARRAY;
default:
/* For everything we didn't handle, assume a side-effect */
return 1;
}
}
static zend_always_inline void add_to_worklists(context *ctx, int var_num, int check) {
zend_ssa_var *var = &ctx->ssa->vars[var_num];
if (var->definition >= 0) {
if (!check || zend_bitset_in(ctx->instr_dead, var->definition)) {
zend_bitset_incl(ctx->instr_worklist, var->definition);
}
} else if (var->definition_phi) {
if (!check || zend_bitset_in(ctx->phi_dead, var_num)) {
zend_bitset_incl(ctx->phi_worklist, var_num);
}
}
}
static inline void add_to_phi_worklist_no_val(context *ctx, int var_num) {
zend_ssa_var *var = &ctx->ssa->vars[var_num];
if (var->definition_phi && zend_bitset_in(ctx->phi_dead, var_num)) {
zend_bitset_incl(ctx->phi_worklist_no_val, var_num);
}
}
static zend_always_inline void add_operands_to_worklists(context *ctx, zend_op *opline, zend_ssa_op *ssa_op, zend_ssa *ssa, int check) {
if (ssa_op->result_use >= 0) {
add_to_worklists(ctx, ssa_op->result_use, check);
}
if (ssa_op->op1_use >= 0) {
if (!zend_ssa_is_no_val_use(opline, ssa_op, ssa_op->op1_use)
|| (opline->opcode == ZEND_ASSIGN
&& (ssa->var_info[ssa_op->op1_use].type & MAY_BE_REF) != 0)) {
add_to_worklists(ctx, ssa_op->op1_use, check);
} else {
add_to_phi_worklist_no_val(ctx, ssa_op->op1_use);
}
}
if (ssa_op->op2_use >= 0) {
if (!zend_ssa_is_no_val_use(opline, ssa_op, ssa_op->op2_use)
|| (opline->opcode == ZEND_FE_FETCH_R
&& (ssa->var_info[ssa_op->op2_use].type & MAY_BE_REF) != 0)) {
add_to_worklists(ctx, ssa_op->op2_use, check);
} else {
add_to_phi_worklist_no_val(ctx, ssa_op->op2_use);
}
}
}
static zend_always_inline void add_phi_sources_to_worklists(context *ctx, zend_ssa_phi *phi, int check) {
zend_ssa *ssa = ctx->ssa;
int source;
FOREACH_PHI_SOURCE(phi, source) {
add_to_worklists(ctx, source, check);
} FOREACH_PHI_SOURCE_END();
}
static inline bool is_var_dead(context *ctx, int var_num) {
zend_ssa_var *var = &ctx->ssa->vars[var_num];
if (var->definition_phi) {
return zend_bitset_in(ctx->phi_dead, var_num);
} else if (var->definition >= 0) {
return zend_bitset_in(ctx->instr_dead, var->definition);
} else {
/* Variable has no definition, so either the definition has already been removed (var is
* dead) or this is one of the implicit variables at the start of the function (for our
* purposes live) */
return var_num >= ctx->op_array->last_var;
}
}
// Sometimes we can mark the var as EXT_UNUSED
static bool try_remove_var_def(context *ctx, int free_var, int use_chain, zend_op *opline) {
if (use_chain >= 0) {
return 0;
}
zend_ssa_var *var = &ctx->ssa->vars[free_var];
int def = var->definition;
if (def >= 0) {
zend_ssa_op *def_op = &ctx->ssa->ops[def];
if (def_op->result_def == free_var
&& var->phi_use_chain == NULL
&& var->use_chain == (opline - ctx->op_array->opcodes)) {
zend_op *def_opline = &ctx->op_array->opcodes[def];
switch (def_opline->opcode) {
case ZEND_ASSIGN:
case ZEND_ASSIGN_REF:
case ZEND_ASSIGN_DIM:
case ZEND_ASSIGN_OBJ:
case ZEND_ASSIGN_OBJ_REF:
case ZEND_ASSIGN_STATIC_PROP:
case ZEND_ASSIGN_STATIC_PROP_REF:
case ZEND_ASSIGN_OP:
case ZEND_ASSIGN_DIM_OP:
case ZEND_ASSIGN_OBJ_OP:
case ZEND_ASSIGN_STATIC_PROP_OP:
case ZEND_PRE_INC:
case ZEND_PRE_DEC:
case ZEND_PRE_INC_OBJ:
case ZEND_PRE_DEC_OBJ:
case ZEND_DO_ICALL:
case ZEND_DO_UCALL:
case ZEND_DO_FCALL_BY_NAME:
case ZEND_DO_FCALL:
case ZEND_INCLUDE_OR_EVAL:
case ZEND_YIELD:
case ZEND_YIELD_FROM:
case ZEND_ASSERT_CHECK:
def_opline->result_type = IS_UNUSED;
def_opline->result.var = 0;
def_op->result_def = -1;
var->definition = -1;
return 1;
default:
break;
}
}
}
return 0;
}
static zend_always_inline bool may_be_refcounted(uint32_t type) {
return (type & (MAY_BE_STRING|MAY_BE_ARRAY|MAY_BE_OBJECT|MAY_BE_RESOURCE|MAY_BE_REF)) != 0;
}
static inline bool is_free_of_live_var(context *ctx, zend_op *opline, zend_ssa_op *ssa_op) {
switch (opline->opcode) {
case ZEND_FREE:
/* It is always safe to remove FREEs of non-refcounted values, even if they are live. */
if ((ctx->ssa->var_info[ssa_op->op1_use].type & (MAY_BE_REF|MAY_BE_ANY|MAY_BE_UNDEF)) != 0
&& !may_be_refcounted(ctx->ssa->var_info[ssa_op->op1_use].type)) {
return 0;
}
ZEND_FALLTHROUGH;
case ZEND_FE_FREE:
return !is_var_dead(ctx, ssa_op->op1_use);
default:
return 0;
}
}
/* Returns whether the instruction has been DCEd */
static bool dce_instr(context *ctx, zend_op *opline, zend_ssa_op *ssa_op) {
zend_ssa *ssa = ctx->ssa;
int free_var = -1;
uint8_t free_var_type;
if (opline->opcode == ZEND_NOP) {
return 0;
}
/* We mark FREEs as dead, but they're only really dead if the destroyed var is dead */
if (is_free_of_live_var(ctx, opline, ssa_op)) {
return 0;
}
if ((opline->op1_type & (IS_VAR|IS_TMP_VAR))&& !is_var_dead(ctx, ssa_op->op1_use)) {
if (!try_remove_var_def(ctx, ssa_op->op1_use, ssa_op->op1_use_chain, opline)) {
if (may_be_refcounted(ssa->var_info[ssa_op->op1_use].type)
&& opline->opcode != ZEND_CASE && opline->opcode != ZEND_CASE_STRICT) {
free_var = ssa_op->op1_use;
free_var_type = opline->op1_type;
}
}
}
if ((opline->op2_type & (IS_VAR|IS_TMP_VAR)) && !is_var_dead(ctx, ssa_op->op2_use)) {
if (!try_remove_var_def(ctx, ssa_op->op2_use, ssa_op->op2_use_chain, opline)) {
if (may_be_refcounted(ssa->var_info[ssa_op->op2_use].type)) {
if (free_var >= 0) {
// TODO: We can't free two vars. Keep instruction alive.
zend_bitset_excl(ctx->instr_dead, opline - ctx->op_array->opcodes);
return 0;
}
free_var = ssa_op->op2_use;
free_var_type = opline->op2_type;
}
}
}
zend_ssa_rename_defs_of_instr(ctx->ssa, ssa_op);
zend_ssa_remove_instr(ctx->ssa, opline, ssa_op);
if (free_var >= 0) {
opline->opcode = ZEND_FREE;
opline->op1.var = EX_NUM_TO_VAR(ssa->vars[free_var].var);
opline->op1_type = free_var_type;
ssa_op->op1_use = free_var;
ssa_op->op1_use_chain = ssa->vars[free_var].use_chain;
ssa->vars[free_var].use_chain = ssa_op - ssa->ops;
return 0;
}
return 1;
}
static inline int get_common_phi_source(zend_ssa *ssa, zend_ssa_phi *phi) {
int common_source = -1;
int source;
FOREACH_PHI_SOURCE(phi, source) {
if (source == phi->ssa_var) {
continue;
}
if (common_source == -1) {
common_source = source;
} else if (common_source != source) {
return -1;
}
} FOREACH_PHI_SOURCE_END();
/* If all sources are phi->ssa_var this phi must be in an unreachable cycle.
* We can't easily drop the phi in that case, as we don't have something to replace it with.
* Ideally SCCP would eliminate the whole cycle. */
return common_source;
}
static void try_remove_trivial_phi(context *ctx, zend_ssa_phi *phi) {
zend_ssa *ssa = ctx->ssa;
if (phi->pi < 0) {
/* Phi assignment with identical source operands */
int common_source = get_common_phi_source(ssa, phi);
if (common_source >= 0) {
zend_ssa_rename_var_uses(ssa, phi->ssa_var, common_source, 1);
zend_ssa_remove_phi(ssa, phi);
}
} else {
/* Pi assignment that is only used in Phi/Pi assignments */
// TODO What if we want to rerun type inference after DCE? Maybe separate this?
/*ZEND_ASSERT(phi->sources[0] != -1);
if (ssa->vars[phi->ssa_var].use_chain < 0) {
zend_ssa_rename_var_uses_keep_types(ssa, phi->ssa_var, phi->sources[0], 1);
zend_ssa_remove_phi(ssa, phi);
}*/
}
}
static inline bool may_break_varargs(const zend_op_array *op_array, const zend_ssa *ssa, const zend_ssa_op *ssa_op) {
if (ssa_op->op1_def >= 0
&& ssa->vars[ssa_op->op1_def].var < op_array->num_args) {
return 1;
}
if (ssa_op->op2_def >= 0
&& ssa->vars[ssa_op->op2_def].var < op_array->num_args) {
return 1;
}
if (ssa_op->result_def >= 0
&& ssa->vars[ssa_op->result_def].var < op_array->num_args) {
return 1;
}
return 0;
}
static inline bool may_throw_dce_exception(const zend_op *opline) {
return opline->opcode == ZEND_ADD_ARRAY_ELEMENT && opline->op2_type == IS_UNUSED;
}
int dce_optimize_op_array(zend_op_array *op_array, zend_optimizer_ctx *optimizer_ctx, zend_ssa *ssa, bool reorder_dtor_effects) {
int i;
zend_ssa_phi *phi;
int removed_ops = 0;
/* DCE of CV operations that changes arguments may affect vararg functions. */
bool has_varargs = (ssa->cfg.flags & ZEND_FUNC_VARARG) != 0;
context ctx;
ctx.ssa = ssa;
ctx.op_array = op_array;
ctx.reorder_dtor_effects = reorder_dtor_effects;
void *checkpoint = zend_arena_checkpoint(optimizer_ctx->arena);
/* We have no dedicated phi vector, so we use the whole ssa var vector instead */
ctx.instr_worklist_len = zend_bitset_len(op_array->last);
ctx.instr_worklist = zend_arena_calloc(&optimizer_ctx->arena, ctx.instr_worklist_len, sizeof(zend_ulong));
ctx.phi_worklist_len = zend_bitset_len(ssa->vars_count);
ctx.phi_worklist = zend_arena_calloc(&optimizer_ctx->arena, ctx.phi_worklist_len, sizeof(zend_ulong));
ctx.phi_worklist_no_val = zend_arena_calloc(&optimizer_ctx->arena, ctx.phi_worklist_len, sizeof(zend_ulong));
/* Optimistically assume all instructions and phis to be dead */
ctx.instr_dead = zend_arena_calloc(&optimizer_ctx->arena, ctx.instr_worklist_len, sizeof(zend_ulong));
ctx.phi_dead = zend_arena_alloc(&optimizer_ctx->arena, ctx.phi_worklist_len * sizeof(zend_ulong));
memset(ctx.phi_dead, 0xff, sizeof(zend_ulong) * ctx.phi_worklist_len);
/* Mark non-CV phis as live. Even if the result is unused, we generally cannot remove one
* of the producing instructions, as it combines producing the result with control flow.
* This can be made more precise if there are any cases where this is not the case. */
FOREACH_PHI(phi) {
if (phi->var >= op_array->last_var
&& may_be_refcounted(ssa->var_info[phi->ssa_var].type)) {
zend_bitset_excl(ctx.phi_dead, phi->ssa_var);
add_phi_sources_to_worklists(&ctx, phi, 0);
}
} FOREACH_PHI_END();
/* Mark reachable instruction without side effects as dead */
int b = ssa->cfg.blocks_count;
while (b > 0) {
int op_data = -1;
b--;
zend_basic_block *block = &ssa->cfg.blocks[b];
if (!(block->flags & ZEND_BB_REACHABLE)) {
continue;
}
i = block->start + block->len;
while (i > block->start) {
i--;
if (op_array->opcodes[i].opcode == ZEND_OP_DATA) {
op_data = i;
continue;
}
if (zend_bitset_in(ctx.instr_worklist, i)) {
zend_bitset_excl(ctx.instr_worklist, i);
add_operands_to_worklists(&ctx, &op_array->opcodes[i], &ssa->ops[i], ssa, 0);
if (op_data >= 0) {
add_operands_to_worklists(&ctx, &op_array->opcodes[op_data], &ssa->ops[op_data], ssa, 0);
}
} else if (may_have_side_effects(op_array, ssa, &op_array->opcodes[i], &ssa->ops[i], ctx.reorder_dtor_effects)
|| (zend_may_throw(&op_array->opcodes[i], &ssa->ops[i], op_array, ssa)
&& !may_throw_dce_exception(&op_array->opcodes[i]))
|| (has_varargs && may_break_varargs(op_array, ssa, &ssa->ops[i]))) {
if (op_array->opcodes[i].opcode == ZEND_NEW
&& op_array->opcodes[i+1].opcode == ZEND_DO_FCALL
&& ssa->ops[i].result_def >= 0
&& ssa->vars[ssa->ops[i].result_def].escape_state == ESCAPE_STATE_NO_ESCAPE) {
zend_bitset_incl(ctx.instr_dead, i);
zend_bitset_incl(ctx.instr_dead, i+1);
} else {
add_operands_to_worklists(&ctx, &op_array->opcodes[i], &ssa->ops[i], ssa, 0);
if (op_data >= 0) {
add_operands_to_worklists(&ctx, &op_array->opcodes[op_data], &ssa->ops[op_data], ssa, 0);
}
}
} else {
zend_bitset_incl(ctx.instr_dead, i);
if (op_data >= 0) {
zend_bitset_incl(ctx.instr_dead, op_data);
}
}
op_data = -1;
}
}
/* Propagate liveness backwards to all definitions of used vars */
while (!zend_bitset_empty(ctx.instr_worklist, ctx.instr_worklist_len)
|| !zend_bitset_empty(ctx.phi_worklist, ctx.phi_worklist_len)) {
while ((i = zend_bitset_pop_first(ctx.instr_worklist, ctx.instr_worklist_len)) >= 0) {
zend_bitset_excl(ctx.instr_dead, i);
add_operands_to_worklists(&ctx, &op_array->opcodes[i], &ssa->ops[i], ssa, 1);
if (i < op_array->last
&& (op_array->opcodes[i+1].opcode == ZEND_OP_DATA
|| (op_array->opcodes[i].opcode == ZEND_NEW
&& op_array->opcodes[i+1].opcode == ZEND_DO_FCALL))) {
zend_bitset_excl(ctx.instr_dead, i+1);
add_operands_to_worklists(&ctx, &op_array->opcodes[i+1], &ssa->ops[i+1], ssa, 1);
}
}
while ((i = zend_bitset_pop_first(ctx.phi_worklist, ctx.phi_worklist_len)) >= 0) {
zend_bitset_excl(ctx.phi_dead, i);
zend_bitset_excl(ctx.phi_worklist_no_val, i);
add_phi_sources_to_worklists(&ctx, ssa->vars[i].definition_phi, 1);
}
}
/* Eliminate dead instructions */
ZEND_BITSET_FOREACH(ctx.instr_dead, ctx.instr_worklist_len, i) {
removed_ops += dce_instr(&ctx, &op_array->opcodes[i], &ssa->ops[i]);
} ZEND_BITSET_FOREACH_END();
/* Improper uses don't count as "uses" for the purpose of instruction elimination,
* but we have to retain phis defining them.
* Propagate this information backwards, marking any phi with an improperly used
* target as non-dead. */
while ((i = zend_bitset_pop_first(ctx.phi_worklist_no_val, ctx.phi_worklist_len)) >= 0) {
zend_ssa_phi *phi = ssa->vars[i].definition_phi;
int source;
zend_bitset_excl(ctx.phi_dead, i);
FOREACH_PHI_SOURCE(phi, source) {
add_to_phi_worklist_no_val(&ctx, source);
} FOREACH_PHI_SOURCE_END();
}
/* Now collect the actually dead phis */
FOREACH_PHI(phi) {
if (zend_bitset_in(ctx.phi_dead, phi->ssa_var)) {
zend_ssa_remove_uses_of_var(ssa, phi->ssa_var);
zend_ssa_remove_phi(ssa, phi);
} else {
/* Remove trivial phis (phis with identical source operands) */
try_remove_trivial_phi(&ctx, phi);
}
} FOREACH_PHI_END();
zend_arena_release(&optimizer_ctx->arena, checkpoint);
return removed_ops;
}