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php-src/ext/opcache/Optimizer/zend_cfg.c

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/*
+----------------------------------------------------------------------+
| Zend Engine, CFG - Control Flow Graph |
+----------------------------------------------------------------------+
| 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: |
| http://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: Dmitry Stogov <dmitry@php.net> |
+----------------------------------------------------------------------+
*/
#include "php.h"
#include "zend_compile.h"
#include "zend_cfg.h"
#include "zend_func_info.h"
#include "zend_worklist.h"
#include "zend_optimizer.h"
#include "zend_optimizer_internal.h"
static void zend_mark_reachable(zend_op *opcodes, zend_cfg *cfg, zend_basic_block *b) /* {{{ */
{
zend_basic_block *blocks = cfg->blocks;
while (1) {
int i;
b->flags |= ZEND_BB_REACHABLE;
if (b->successors_count == 0) {
b->flags |= ZEND_BB_EXIT;
return;
}
for (i = 0; i < b->successors_count; i++) {
zend_basic_block *succ = blocks + b->successors[i];
if (b->len != 0) {
zend_uchar opcode = opcodes[b->start + b->len - 1].opcode;
if (b->successors_count == 1) {
if (opcode == ZEND_JMP) {
succ->flags |= ZEND_BB_TARGET;
} else {
succ->flags |= ZEND_BB_FOLLOW;
if ((cfg->flags & ZEND_CFG_STACKLESS)) {
if (opcode == ZEND_INCLUDE_OR_EVAL ||
opcode == ZEND_GENERATOR_CREATE ||
opcode == ZEND_YIELD ||
opcode == ZEND_YIELD_FROM ||
opcode == ZEND_DO_FCALL ||
opcode == ZEND_DO_UCALL ||
opcode == ZEND_DO_FCALL_BY_NAME) {
succ->flags |= ZEND_BB_ENTRY;
}
}
if ((cfg->flags & ZEND_CFG_RECV_ENTRY)) {
if (opcode == ZEND_RECV ||
opcode == ZEND_RECV_INIT) {
succ->flags |= ZEND_BB_RECV_ENTRY;
}
}
}
} else if (b->successors_count == 2) {
if (i == 0 || opcode == ZEND_JMPZNZ) {
succ->flags |= ZEND_BB_TARGET;
} else {
succ->flags |= ZEND_BB_FOLLOW;
}
} else {
ZEND_ASSERT(opcode == ZEND_SWITCH_LONG || opcode == ZEND_SWITCH_STRING);
if (i == b->successors_count - 1) {
succ->flags |= ZEND_BB_FOLLOW | ZEND_BB_TARGET;
} else {
succ->flags |= ZEND_BB_TARGET;
}
}
} else {
succ->flags |= ZEND_BB_FOLLOW;
}
if (i == b->successors_count - 1) {
/* Tail call optimization */
if (succ->flags & ZEND_BB_REACHABLE) {
return;
}
b = succ;
break;
} else {
/* Recusively check reachability */
if (!(succ->flags & ZEND_BB_REACHABLE)) {
zend_mark_reachable(opcodes, cfg, succ);
}
}
}
}
}
/* }}} */
static void zend_mark_reachable_blocks(const zend_op_array *op_array, zend_cfg *cfg, int start) /* {{{ */
{
zend_basic_block *blocks = cfg->blocks;
blocks[start].flags = ZEND_BB_START;
zend_mark_reachable(op_array->opcodes, cfg, blocks + start);
if (op_array->last_try_catch) {
zend_basic_block *b;
int j, changed;
uint32_t *block_map = cfg->map;
do {
changed = 0;
/* Add exception paths */
for (j = 0; j < op_array->last_try_catch; j++) {
/* check for jumps into the middle of try block */
b = blocks + block_map[op_array->try_catch_array[j].try_op];
if (!(b->flags & ZEND_BB_REACHABLE)) {
zend_basic_block *end;
if (op_array->try_catch_array[j].catch_op) {
end = blocks + block_map[op_array->try_catch_array[j].catch_op];
while (b != end) {
if (b->flags & ZEND_BB_REACHABLE) {
op_array->try_catch_array[j].try_op = b->start;
break;
}
b++;
}
}
b = blocks + block_map[op_array->try_catch_array[j].try_op];
if (!(b->flags & ZEND_BB_REACHABLE)) {
if (op_array->try_catch_array[j].finally_op) {
end = blocks + block_map[op_array->try_catch_array[j].finally_op];
while (b != end) {
if (b->flags & ZEND_BB_REACHABLE) {
op_array->try_catch_array[j].try_op = op_array->try_catch_array[j].catch_op;
changed = 1;
zend_mark_reachable(op_array->opcodes, cfg, blocks + block_map[op_array->try_catch_array[j].try_op]);
break;
}
b++;
}
}
}
}
b = blocks + block_map[op_array->try_catch_array[j].try_op];
if (b->flags & ZEND_BB_REACHABLE) {
b->flags |= ZEND_BB_TRY;
if (op_array->try_catch_array[j].catch_op) {
b = blocks + block_map[op_array->try_catch_array[j].catch_op];
b->flags |= ZEND_BB_CATCH;
if (!(b->flags & ZEND_BB_REACHABLE)) {
changed = 1;
zend_mark_reachable(op_array->opcodes, cfg, b);
}
}
if (op_array->try_catch_array[j].finally_op) {
b = blocks + block_map[op_array->try_catch_array[j].finally_op];
b->flags |= ZEND_BB_FINALLY;
if (!(b->flags & ZEND_BB_REACHABLE)) {
changed = 1;
zend_mark_reachable(op_array->opcodes, cfg, b);
}
}
if (op_array->try_catch_array[j].finally_end) {
b = blocks + block_map[op_array->try_catch_array[j].finally_end];
b->flags |= ZEND_BB_FINALLY_END;
if (!(b->flags & ZEND_BB_REACHABLE)) {
changed = 1;
zend_mark_reachable(op_array->opcodes, cfg, b);
}
}
} else {
if (op_array->try_catch_array[j].catch_op) {
ZEND_ASSERT(!(blocks[block_map[op_array->try_catch_array[j].catch_op]].flags & ZEND_BB_REACHABLE));
}
if (op_array->try_catch_array[j].finally_op) {
ZEND_ASSERT(!(blocks[block_map[op_array->try_catch_array[j].finally_op]].flags & ZEND_BB_REACHABLE));
}
if (op_array->try_catch_array[j].finally_end) {
ZEND_ASSERT(!(blocks[block_map[op_array->try_catch_array[j].finally_end]].flags & ZEND_BB_REACHABLE));
}
}
}
} while (changed);
}
if (cfg->flags & ZEND_FUNC_FREE_LOOP_VAR) {
zend_basic_block *b;
int j;
uint32_t *block_map = cfg->map;
/* Mark blocks that are unreachable, but free a loop var created in a reachable block. */
for (b = blocks; b < blocks + cfg->blocks_count; b++) {
if (b->flags & ZEND_BB_REACHABLE) {
continue;
}
for (j = b->start; j < b->start + b->len; j++) {
zend_op *opline = &op_array->opcodes[j];
if (opline->opcode == ZEND_FE_FREE ||
(opline->opcode == ZEND_FREE && opline->extended_value == ZEND_FREE_SWITCH)
) {
zend_op *def_opline = zend_optimizer_get_loop_var_def(op_array, opline);
if (def_opline) {
uint32_t def_block = block_map[def_opline - op_array->opcodes];
if (blocks[def_block].flags & ZEND_BB_REACHABLE) {
b->flags |= ZEND_BB_UNREACHABLE_FREE;
break;
}
}
}
}
}
}
}
/* }}} */
void zend_cfg_remark_reachable_blocks(const zend_op_array *op_array, zend_cfg *cfg) /* {{{ */
{
zend_basic_block *blocks = cfg->blocks;
int i;
int start = 0;
for (i = 0; i < cfg->blocks_count; i++) {
if (blocks[i].flags & ZEND_BB_REACHABLE) {
start = i;
i++;
break;
}
}
/* clear all flags */
for (i = 0; i < cfg->blocks_count; i++) {
blocks[i].flags = 0;
}
zend_mark_reachable_blocks(op_array, cfg, start);
}
/* }}} */
static void initialize_block(zend_basic_block *block) {
block->flags = 0;
block->successors = block->successors_storage;
block->successors_count = 0;
block->predecessors_count = 0;
block->predecessor_offset = -1;
block->idom = -1;
block->loop_header = -1;
block->level = -1;
block->children = -1;
block->next_child = -1;
}
#define BB_START(i) do { \
if (!block_map[i]) { blocks_count++;} \
block_map[i]++; \
} while (0)
int zend_build_cfg(zend_arena **arena, const zend_op_array *op_array, uint32_t build_flags, zend_cfg *cfg) /* {{{ */
{
uint32_t flags = 0;
uint32_t i;
int j;
uint32_t *block_map;
zend_function *fn;
int blocks_count = 0;
zend_basic_block *blocks;
zval *zv;
zend_bool extra_entry_block = 0;
cfg->flags = build_flags & (ZEND_CFG_STACKLESS|ZEND_CFG_RECV_ENTRY);
cfg->map = block_map = zend_arena_calloc(arena, op_array->last, sizeof(uint32_t));
/* Build CFG, Step 1: Find basic blocks starts, calculate number of blocks */
BB_START(0);
for (i = 0; i < op_array->last; i++) {
zend_op *opline = op_array->opcodes + i;
switch (opline->opcode) {
case ZEND_RECV:
case ZEND_RECV_INIT:
if (build_flags & ZEND_CFG_RECV_ENTRY) {
BB_START(i + 1);
}
break;
case ZEND_RETURN:
case ZEND_RETURN_BY_REF:
case ZEND_GENERATOR_RETURN:
case ZEND_EXIT:
case ZEND_THROW:
if (i + 1 < op_array->last) {
BB_START(i + 1);
}
break;
case ZEND_INCLUDE_OR_EVAL:
flags |= ZEND_FUNC_INDIRECT_VAR_ACCESS;
case ZEND_GENERATOR_CREATE:
case ZEND_YIELD:
case ZEND_YIELD_FROM:
if (build_flags & ZEND_CFG_STACKLESS) {
BB_START(i + 1);
}
break;
case ZEND_DO_FCALL:
case ZEND_DO_UCALL:
case ZEND_DO_FCALL_BY_NAME:
flags |= ZEND_FUNC_HAS_CALLS;
if (build_flags & ZEND_CFG_STACKLESS) {
BB_START(i + 1);
}
break;
case ZEND_DO_ICALL:
flags |= ZEND_FUNC_HAS_CALLS;
break;
case ZEND_INIT_FCALL:
case ZEND_INIT_NS_FCALL_BY_NAME:
zv = CRT_CONSTANT(opline->op2);
if (opline->opcode == ZEND_INIT_NS_FCALL_BY_NAME) {
/* The third literal is the lowercased unqualified name */
zv += 2;
}
if ((fn = zend_hash_find_ptr(EG(function_table), Z_STR_P(zv))) != NULL) {
if (fn->type == ZEND_INTERNAL_FUNCTION) {
flags |= zend_optimizer_classify_function(
Z_STR_P(zv), opline->extended_value);
}
}
break;
case ZEND_FAST_CALL:
BB_START(OP_JMP_ADDR(opline, opline->op1) - op_array->opcodes);
BB_START(i + 1);
break;
case ZEND_FAST_RET:
if (i + 1 < op_array->last) {
BB_START(i + 1);
}
break;
case ZEND_JMP:
BB_START(OP_JMP_ADDR(opline, opline->op1) - op_array->opcodes);
if (i + 1 < op_array->last) {
BB_START(i + 1);
}
break;
case ZEND_JMPZNZ:
BB_START(OP_JMP_ADDR(opline, opline->op2) - op_array->opcodes);
BB_START(ZEND_OFFSET_TO_OPLINE_NUM(op_array, opline, opline->extended_value));
if (i + 1 < op_array->last) {
BB_START(i + 1);
}
break;
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:
BB_START(OP_JMP_ADDR(opline, opline->op2) - op_array->opcodes);
BB_START(i + 1);
break;
case ZEND_CATCH:
if (!(opline->extended_value & ZEND_LAST_CATCH)) {
BB_START(OP_JMP_ADDR(opline, opline->op2) - op_array->opcodes);
}
BB_START(i + 1);
break;
case ZEND_FE_FETCH_R:
case ZEND_FE_FETCH_RW:
BB_START(ZEND_OFFSET_TO_OPLINE_NUM(op_array, opline, opline->extended_value));
BB_START(i + 1);
break;
case ZEND_FE_RESET_R:
case ZEND_FE_RESET_RW:
BB_START(OP_JMP_ADDR(opline, opline->op2) - op_array->opcodes);
BB_START(i + 1);
break;
case ZEND_SWITCH_LONG:
case ZEND_SWITCH_STRING:
{
HashTable *jumptable = Z_ARRVAL_P(CRT_CONSTANT(opline->op2));
zval *zv;
ZEND_HASH_FOREACH_VAL(jumptable, zv) {
BB_START(ZEND_OFFSET_TO_OPLINE_NUM(op_array, opline, Z_LVAL_P(zv)));
} ZEND_HASH_FOREACH_END();
BB_START(ZEND_OFFSET_TO_OPLINE_NUM(op_array, opline, opline->extended_value));
BB_START(i + 1);
break;
}
case ZEND_FETCH_R:
case ZEND_FETCH_W:
case ZEND_FETCH_RW:
case ZEND_FETCH_FUNC_ARG:
case ZEND_FETCH_IS:
case ZEND_FETCH_UNSET:
case ZEND_UNSET_VAR:
case ZEND_ISSET_ISEMPTY_VAR:
if (opline->extended_value & ZEND_FETCH_LOCAL) {
flags |= ZEND_FUNC_INDIRECT_VAR_ACCESS;
} else if ((opline->extended_value & (ZEND_FETCH_GLOBAL | ZEND_FETCH_GLOBAL_LOCK)) &&
!op_array->function_name) {
flags |= ZEND_FUNC_INDIRECT_VAR_ACCESS;
}
break;
case ZEND_FUNC_GET_ARGS:
flags |= ZEND_FUNC_VARARG;
break;
case ZEND_EXT_NOP:
case ZEND_EXT_STMT:
flags |= ZEND_FUNC_HAS_EXTENDED_STMT;
break;
case ZEND_EXT_FCALL_BEGIN:
case ZEND_EXT_FCALL_END:
flags |= ZEND_FUNC_HAS_EXTENDED_FCALL;
break;
case ZEND_FREE:
if (opline->extended_value == ZEND_FREE_SWITCH) {
flags |= ZEND_FUNC_FREE_LOOP_VAR;
}
break;
case ZEND_FE_FREE:
flags |= ZEND_FUNC_FREE_LOOP_VAR;
break;
}
}
/* If the entry block has predecessors, we may need to split it */
if ((build_flags & ZEND_CFG_NO_ENTRY_PREDECESSORS)
&& op_array->last > 0 && block_map[0] > 1) {
extra_entry_block = 1;
}
if (op_array->last_try_catch) {
for (j = 0; j < op_array->last_try_catch; j++) {
BB_START(op_array->try_catch_array[j].try_op);
if (op_array->try_catch_array[j].catch_op) {
BB_START(op_array->try_catch_array[j].catch_op);
}
if (op_array->try_catch_array[j].finally_op) {
BB_START(op_array->try_catch_array[j].finally_op);
}
if (op_array->try_catch_array[j].finally_end) {
BB_START(op_array->try_catch_array[j].finally_end);
}
}
}
blocks_count += extra_entry_block;
cfg->blocks_count = blocks_count;
/* Build CFG, Step 2: Build Array of Basic Blocks */
cfg->blocks = blocks = zend_arena_calloc(arena, sizeof(zend_basic_block), blocks_count);
blocks_count = -1;
if (extra_entry_block) {
initialize_block(&blocks[0]);
blocks[0].start = 0;
blocks[0].len = 0;
blocks_count++;
}
for (i = 0; i < op_array->last; i++) {
if (block_map[i]) {
if (blocks_count >= 0) {
blocks[blocks_count].len = i - blocks[blocks_count].start;
}
blocks_count++;
initialize_block(&blocks[blocks_count]);
blocks[blocks_count].start = i;
}
block_map[i] = blocks_count;
}
blocks[blocks_count].len = i - blocks[blocks_count].start;
blocks_count++;
/* Build CFG, Step 3: Calculate successors */
for (j = 0; j < blocks_count; j++) {
zend_basic_block *block = &blocks[j];
zend_op *opline;
if (block->len == 0) {
block->successors_count = 1;
block->successors[0] = j + 1;
continue;
}
opline = op_array->opcodes + block->start + block->len - 1;
switch (opline->opcode) {
case ZEND_FAST_RET:
case ZEND_RETURN:
case ZEND_RETURN_BY_REF:
case ZEND_GENERATOR_RETURN:
case ZEND_EXIT:
case ZEND_THROW:
break;
case ZEND_JMP:
block->successors_count = 1;
block->successors[0] = block_map[OP_JMP_ADDR(opline, opline->op1) - op_array->opcodes];
break;
case ZEND_JMPZNZ:
block->successors_count = 2;
block->successors[0] = block_map[OP_JMP_ADDR(opline, opline->op2) - op_array->opcodes];
block->successors[1] = block_map[ZEND_OFFSET_TO_OPLINE_NUM(op_array, opline, opline->extended_value)];
break;
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:
block->successors_count = 2;
block->successors[0] = block_map[OP_JMP_ADDR(opline, opline->op2) - op_array->opcodes];
block->successors[1] = j + 1;
break;
case ZEND_CATCH:
if (!(opline->extended_value & ZEND_LAST_CATCH)) {
block->successors_count = 2;
block->successors[0] = block_map[OP_JMP_ADDR(opline, opline->op2) - op_array->opcodes];
block->successors[1] = j + 1;
} else {
block->successors_count = 1;
block->successors[0] = j + 1;
}
break;
case ZEND_FE_FETCH_R:
case ZEND_FE_FETCH_RW:
block->successors_count = 2;
block->successors[0] = block_map[ZEND_OFFSET_TO_OPLINE_NUM(op_array, opline, opline->extended_value)];
block->successors[1] = j + 1;
break;
case ZEND_FE_RESET_R:
case ZEND_FE_RESET_RW:
block->successors_count = 2;
block->successors[0] = block_map[OP_JMP_ADDR(opline, opline->op2) - op_array->opcodes];
block->successors[1] = j + 1;
break;
case ZEND_FAST_CALL:
block->successors_count = 2;
block->successors[0] = block_map[OP_JMP_ADDR(opline, opline->op1) - op_array->opcodes];
block->successors[1] = j + 1;
break;
case ZEND_SWITCH_LONG:
case ZEND_SWITCH_STRING:
{
HashTable *jumptable = Z_ARRVAL_P(CRT_CONSTANT(opline->op2));
zval *zv;
uint32_t s = 0;
block->successors_count = 2 + zend_hash_num_elements(jumptable);
block->successors = zend_arena_calloc(arena, block->successors_count, sizeof(int));
ZEND_HASH_FOREACH_VAL(jumptable, zv) {
block->successors[s++] = block_map[ZEND_OFFSET_TO_OPLINE_NUM(op_array, opline, Z_LVAL_P(zv))];
} ZEND_HASH_FOREACH_END();
block->successors[s++] = block_map[ZEND_OFFSET_TO_OPLINE_NUM(op_array, opline, opline->extended_value)];
block->successors[s++] = j + 1;
break;
}
default:
block->successors_count = 1;
block->successors[0] = j + 1;
break;
}
}
/* Build CFG, Step 4, Mark Reachable Basic Blocks */
zend_mark_reachable_blocks(op_array, cfg, 0);
cfg->flags |= flags;
return SUCCESS;
}
/* }}} */
int zend_cfg_build_predecessors(zend_arena **arena, zend_cfg *cfg) /* {{{ */
{
int j, s, edges;
zend_basic_block *b;
zend_basic_block *blocks = cfg->blocks;
zend_basic_block *end = blocks + cfg->blocks_count;
int *predecessors;
edges = 0;
for (b = blocks; b < end; b++) {
b->predecessors_count = 0;
}
for (b = blocks; b < end; b++) {
if (!(b->flags & ZEND_BB_REACHABLE)) {
b->successors_count = 0;
b->predecessors_count = 0;
} else {
for (s = 0; s < b->successors_count; s++) {
edges++;
blocks[b->successors[s]].predecessors_count++;
}
}
}
cfg->edges_count = edges;
cfg->predecessors = predecessors = (int*)zend_arena_calloc(arena, sizeof(int), edges);
edges = 0;
for (b = blocks; b < end; b++) {
if (b->flags & ZEND_BB_REACHABLE) {
b->predecessor_offset = edges;
edges += b->predecessors_count;
b->predecessors_count = 0;
}
}
for (j = 0; j < cfg->blocks_count; j++) {
if (blocks[j].flags & ZEND_BB_REACHABLE) {
/* SWITCH_STRING/LONG may have few identical successors */
for (s = 0; s < blocks[j].successors_count; s++) {
int duplicate = 0;
int p;
for (p = 0; p < s; p++) {
if (blocks[j].successors[p] == blocks[j].successors[s]) {
duplicate = 1;
break;
}
}
if (!duplicate) {
zend_basic_block *b = blocks + blocks[j].successors[s];
predecessors[b->predecessor_offset + b->predecessors_count] = j;
b->predecessors_count++;
}
}
}
}
return SUCCESS;
}
/* }}} */
/* Computes a postorder numbering of the CFG */
static void compute_postnum_recursive(
int *postnum, int *cur, const zend_cfg *cfg, int block_num) /* {{{ */
{
int s;
zend_basic_block *block = &cfg->blocks[block_num];
if (postnum[block_num] != -1) {
return;
}
postnum[block_num] = -2; /* Marker for "currently visiting" */
for (s = 0; s < block->successors_count; s++) {
compute_postnum_recursive(postnum, cur, cfg, block->successors[s]);
}
postnum[block_num] = (*cur)++;
}
/* }}} */
/* Computes dominator tree using algorithm from "A Simple, Fast Dominance Algorithm" by
* Cooper, Harvey and Kennedy. */
int zend_cfg_compute_dominators_tree(const zend_op_array *op_array, zend_cfg *cfg) /* {{{ */
{
zend_basic_block *blocks = cfg->blocks;
int blocks_count = cfg->blocks_count;
int j, k, changed;
ALLOCA_FLAG(use_heap)
int *postnum = do_alloca(sizeof(int) * cfg->blocks_count, use_heap);
memset(postnum, -1, sizeof(int) * cfg->blocks_count);
j = 0;
compute_postnum_recursive(postnum, &j, cfg, 0);
/* FIXME: move declarations */
blocks[0].idom = 0;
do {
changed = 0;
/* Iterating in RPO here would converge faster */
for (j = 1; j < blocks_count; j++) {
int idom = -1;
if ((blocks[j].flags & ZEND_BB_REACHABLE) == 0) {
continue;
}
for (k = 0; k < blocks[j].predecessors_count; k++) {
int pred = cfg->predecessors[blocks[j].predecessor_offset + k];
if (idom < 0) {
if (blocks[pred].idom >= 0)
idom = pred;
continue;
}
if (blocks[pred].idom >= 0) {
while (idom != pred) {
while (postnum[pred] < postnum[idom]) pred = blocks[pred].idom;
while (postnum[idom] < postnum[pred]) idom = blocks[idom].idom;
}
}
}
if (idom >= 0 && blocks[j].idom != idom) {
blocks[j].idom = idom;
changed = 1;
}
}
} while (changed);
blocks[0].idom = -1;
for (j = 1; j < blocks_count; j++) {
if ((blocks[j].flags & ZEND_BB_REACHABLE) == 0) {
continue;
}
if (blocks[j].idom >= 0) {
/* Sort by block number to traverse children in pre-order */
if (blocks[blocks[j].idom].children < 0 ||
j < blocks[blocks[j].idom].children) {
blocks[j].next_child = blocks[blocks[j].idom].children;
blocks[blocks[j].idom].children = j;
} else {
int k = blocks[blocks[j].idom].children;
while (blocks[k].next_child >=0 && j > blocks[k].next_child) {
k = blocks[k].next_child;
}
blocks[j].next_child = blocks[k].next_child;
blocks[k].next_child = j;
}
}
}
for (j = 0; j < blocks_count; j++) {
int idom = blocks[j].idom, level = 0;
if ((blocks[j].flags & ZEND_BB_REACHABLE) == 0) {
continue;
}
while (idom >= 0) {
level++;
if (blocks[idom].level >= 0) {
level += blocks[idom].level;
break;
} else {
idom = blocks[idom].idom;
}
}
blocks[j].level = level;
}
free_alloca(postnum, use_heap);
return SUCCESS;
}
/* }}} */
static int dominates(zend_basic_block *blocks, int a, int b) /* {{{ */
{
while (blocks[b].level > blocks[a].level) {
b = blocks[b].idom;
}
return a == b;
}
/* }}} */
typedef struct {
int id;
int level;
} block_info;
static int compare_block_level(const block_info *a, const block_info *b) {
return b->level - a->level;
}
static void swap_blocks(block_info *a, block_info *b) {
block_info tmp = *a;
*a = *b;
*b = tmp;
}
int zend_cfg_identify_loops(const zend_op_array *op_array, zend_cfg *cfg) /* {{{ */
{
int i, j, k, n;
int time;
zend_basic_block *blocks = cfg->blocks;
int *entry_times, *exit_times;
zend_worklist work;
int flag = ZEND_FUNC_NO_LOOPS;
block_info *sorted_blocks;
ALLOCA_FLAG(list_use_heap)
ALLOCA_FLAG(tree_use_heap)
ALLOCA_FLAG(sorted_blocks_use_heap)
ZEND_WORKLIST_ALLOCA(&work, cfg->blocks_count, list_use_heap);
/* We don't materialize the DJ spanning tree explicitly, as we are only interested in ancestor
* queries. These are implemented by checking entry/exit times of the DFS search. */
entry_times = do_alloca(2 * sizeof(int) * cfg->blocks_count, tree_use_heap);
exit_times = entry_times + cfg->blocks_count;
memset(entry_times, -1, 2 * sizeof(int) * cfg->blocks_count);
zend_worklist_push(&work, 0);
time = 0;
while (zend_worklist_len(&work)) {
next:
i = zend_worklist_peek(&work);
if (entry_times[i] == -1) {
entry_times[i] = time++;
}
/* Visit blocks immediately dominated by i. */
for (j = blocks[i].children; j >= 0; j = blocks[j].next_child) {
if (zend_worklist_push(&work, j)) {
goto next;
}
}
/* Visit join edges. */
for (j = 0; j < blocks[i].successors_count; j++) {
int succ = blocks[i].successors[j];
if (blocks[succ].idom == i) {
continue;
} else if (zend_worklist_push(&work, succ)) {
goto next;
}
}
exit_times[i] = time++;
zend_worklist_pop(&work);
}
/* Sort blocks by decreasing level, which is the order in which we want to process them */
sorted_blocks = do_alloca(sizeof(block_info) * cfg->blocks_count, sorted_blocks_use_heap);
for (i = 0; i < cfg->blocks_count; i++) {
sorted_blocks[i].id = i;
sorted_blocks[i].level = blocks[i].level;
}
zend_sort(sorted_blocks, cfg->blocks_count, sizeof(block_info),
(compare_func_t) compare_block_level, (swap_func_t) swap_blocks);
/* Identify loops. See Sreedhar et al, "Identifying Loops Using DJ
Graphs". */
for (n = 0; n < cfg->blocks_count; n++) {
i = sorted_blocks[n].id;
zend_bitset_clear(work.visited, zend_bitset_len(cfg->blocks_count));
for (j = 0; j < blocks[i].predecessors_count; j++) {
int pred = cfg->predecessors[blocks[i].predecessor_offset + j];
/* A join edge is one for which the predecessor does not
immediately dominate the successor. */
if (blocks[i].idom == pred) {
continue;
}
/* In a loop back-edge (back-join edge), the successor dominates
the predecessor. */
if (dominates(blocks, i, pred)) {
blocks[i].flags |= ZEND_BB_LOOP_HEADER;
flag &= ~ZEND_FUNC_NO_LOOPS;
zend_worklist_push(&work, pred);
} else {
/* Otherwise it's a cross-join edge. See if it's a branch
to an ancestor on the DJ spanning tree. */
if (entry_times[pred] > entry_times[i] && exit_times[pred] < exit_times[i]) {
blocks[i].flags |= ZEND_BB_IRREDUCIBLE_LOOP;
flag |= ZEND_FUNC_IRREDUCIBLE;
flag &= ~ZEND_FUNC_NO_LOOPS;
}
}
}
while (zend_worklist_len(&work)) {
j = zend_worklist_pop(&work);
while (blocks[j].loop_header >= 0) {
j = blocks[j].loop_header;
}
if (j != i) {
blocks[j].loop_header = i;
for (k = 0; k < blocks[j].predecessors_count; k++) {
zend_worklist_push(&work, cfg->predecessors[blocks[j].predecessor_offset + k]);
}
}
}
}
free_alloca(sorted_blocks, sorted_blocks_use_heap);
free_alloca(entry_times, tree_use_heap);
ZEND_WORKLIST_FREE_ALLOCA(&work, list_use_heap);
cfg->flags |= flag;
return SUCCESS;
}
/* }}} */
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