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Backport implementation of iterative Pearce's SCC finding algoritm (#12528)
Fixes GH-11795
This commit is contained in:
Dmitry Stogov
parent
b3b46a44c5
commit
52bb39e661
1 changed files with 263 additions and 30 deletions
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@ -77,11 +77,12 @@
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#define CHECK_SCC_VAR(var2) \
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do { \
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if (!ssa->vars[var2].no_val) { \
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if (dfs[var2] < 0) { \
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zend_ssa_check_scc_var(op_array, ssa, var2, index, dfs, root, stack); \
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if (ssa->vars[var2].scc < 0) { \
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zend_ssa_check_scc_var(op_array, ssa, var2, index, stack); \
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} \
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if (ssa->vars[var2].scc < 0 && dfs[root[var]] >= dfs[root[var2]]) { \
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root[var] = root[var2]; \
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if (ssa->vars[var2].scc < ssa->vars[var].scc) { \
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ssa->vars[var].scc = ssa->vars[var2].scc; \
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is_root = 0; \
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} \
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} \
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} while (0)
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@ -172,15 +173,17 @@ static inline bool sub_will_overflow(zend_long a, zend_long b) {
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}
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#endif
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static void zend_ssa_check_scc_var(const zend_op_array *op_array, zend_ssa *ssa, int var, int *index, int *dfs, int *root, zend_worklist_stack *stack) /* {{{ */
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#if 0
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/* Recursive Pearce's SCC algorithm implementation */
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static void zend_ssa_check_scc_var(const zend_op_array *op_array, zend_ssa *ssa, int var, int *index, zend_worklist_stack *stack) /* {{{ */
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{
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int is_root = 1;
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#ifdef SYM_RANGE
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zend_ssa_phi *p;
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#endif
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dfs[var] = *index;
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ssa->vars[var].scc = *index;
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(*index)++;
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root[var] = var;
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FOR_EACH_VAR_USAGE(var, CHECK_SCC_VAR);
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@ -193,17 +196,20 @@ static void zend_ssa_check_scc_var(const zend_op_array *op_array, zend_ssa *ssa,
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}
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#endif
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if (root[var] == var) {
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ssa->vars[var].scc = ssa->sccs;
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if (is_root) {
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ssa->sccs--;
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while (stack->len > 0) {
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int var2 = zend_worklist_stack_peek(stack);
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if (dfs[var2] <= dfs[var]) {
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if (ssa->vars[var2].scc < ssa->vars[var].scc) {
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break;
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}
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zend_worklist_stack_pop(stack);
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ssa->vars[var2].scc = ssa->sccs;
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(*index)--;
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}
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ssa->sccs++;
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ssa->vars[var].scc = ssa->sccs;
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ssa->vars[var].scc_entry = 1;
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(*index)--;
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} else {
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zend_worklist_stack_push(stack, var);
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}
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@ -212,50 +218,277 @@ static void zend_ssa_check_scc_var(const zend_op_array *op_array, zend_ssa *ssa,
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ZEND_API int zend_ssa_find_sccs(const zend_op_array *op_array, zend_ssa *ssa) /* {{{ */
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{
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int index = 0, *dfs, *root;
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int index = 0;
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zend_worklist_stack stack;
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int j;
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ALLOCA_FLAG(dfs_use_heap)
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ALLOCA_FLAG(root_use_heap)
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ALLOCA_FLAG(stack_use_heap)
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dfs = do_alloca(sizeof(int) * ssa->vars_count, dfs_use_heap);
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memset(dfs, -1, sizeof(int) * ssa->vars_count);
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root = do_alloca(sizeof(int) * ssa->vars_count, root_use_heap);
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ZEND_WORKLIST_STACK_ALLOCA(&stack, ssa->vars_count, stack_use_heap);
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/* Find SCCs using Tarjan's algorithm. */
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/* Find SCCs using Pearce's algorithm. */
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ssa->sccs = ssa->vars_count;
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for (j = 0; j < ssa->vars_count; j++) {
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if (!ssa->vars[j].no_val && dfs[j] < 0) {
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zend_ssa_check_scc_var(op_array, ssa, j, &index, dfs, root, &stack);
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if (!ssa->vars[j].no_val && ssa->vars[j].scc < 0) {
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zend_ssa_check_scc_var(op_array, ssa, j, &index, &stack);
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}
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}
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/* Revert SCC order. This results in a topological order. */
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if (ssa->sccs) {
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/* Shift SCC indexes. */
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for (j = 0; j < ssa->vars_count; j++) {
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if (ssa->vars[j].scc >= 0) {
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ssa->vars[j].scc = ssa->sccs - (ssa->vars[j].scc + 1);
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ssa->vars[j].scc -= ssa->sccs;
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}
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}
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}
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ssa->sccs = ssa->vars_count - ssa->sccs;
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for (j = 0; j < ssa->vars_count; j++) {
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if (ssa->vars[j].scc >= 0) {
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int var = j;
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if (root[j] == j) {
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ssa->vars[j].scc_entry = 1;
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}
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FOR_EACH_VAR_USAGE(var, CHECK_SCC_ENTRY);
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}
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}
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ZEND_WORKLIST_STACK_FREE_ALLOCA(&stack, stack_use_heap);
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free_alloca(root, root_use_heap);
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free_alloca(dfs, dfs_use_heap);
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return SUCCESS;
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}
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/* }}} */
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#else
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/* Iterative Pearce's SCC algorithm implementation */
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typedef struct _zend_scc_iterator {
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int state;
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int last;
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union {
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int use;
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zend_ssa_phi *phi;
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};
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} zend_scc_iterator;
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static int zend_scc_next(const zend_op_array *op_array, zend_ssa *ssa, int var, zend_scc_iterator *iterator) /* {{{ */
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{
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zend_ssa_phi *phi;
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int use, var2;
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switch (iterator->state) {
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case 0: goto state_0;
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case 1: use = iterator->use; goto state_1;
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case 2: use = iterator->use; goto state_2;
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case 3: use = iterator->use; goto state_3;
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case 4: use = iterator->use; goto state_4;
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case 5: use = iterator->use; goto state_5;
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case 6: use = iterator->use; goto state_6;
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case 7: use = iterator->use; goto state_7;
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case 8: use = iterator->use; goto state_8;
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case 9: phi = iterator->phi; goto state_9;
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#ifdef SYM_RANGE
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case 10: phi = iterator->phi; goto state_10;
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#endif
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case 11: goto state_11;
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}
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state_0:
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use = ssa->vars[var].use_chain;
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while (use >= 0) {
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iterator->use = use;
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var2 = ssa->ops[use].op1_def;
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if (var2 >= 0 && !ssa->vars[var2].no_val) {
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iterator->state = 1;
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return var2;
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}
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state_1:
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var2 = ssa->ops[use].op2_def;
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if (var2 >= 0 && !ssa->vars[var2].no_val) {
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iterator->state = 2;
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return var2;
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}
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state_2:
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var2 = ssa->ops[use].result_def;
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if (var2 >= 0 && !ssa->vars[var2].no_val) {
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iterator->state = 3;
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return var2;
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}
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state_3:
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if (op_array->opcodes[use].opcode == ZEND_OP_DATA) {
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var2 = ssa->ops[use-1].op1_def;
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if (var2 >= 0 && !ssa->vars[var2].no_val) {
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iterator->state = 4;
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return var2;
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}
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state_4:
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var2 = ssa->ops[use-1].op2_def;
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if (var2 >= 0 && !ssa->vars[var2].no_val) {
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iterator->state = 5;
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return var2;
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}
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state_5:
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var2 = ssa->ops[use-1].result_def;
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if (var2 >= 0 && !ssa->vars[var2].no_val) {
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iterator->state = 8;
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return var2;
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}
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} else if ((uint32_t)use+1 < op_array->last &&
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op_array->opcodes[use+1].opcode == ZEND_OP_DATA) {
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var2 = ssa->ops[use+1].op1_def;
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if (var2 >= 0 && !ssa->vars[var2].no_val) {
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iterator->state = 6;
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return var2;
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}
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state_6:
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var2 = ssa->ops[use+1].op2_def;
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if (var2 >= 0 && !ssa->vars[var2].no_val) {
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iterator->state = 7;
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return var2;
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}
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state_7:
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var2 = ssa->ops[use+1].result_def;
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if (var2 >= 0 && !ssa->vars[var2].no_val) {
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iterator->state = 8;
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return var2;
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}
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}
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state_8:
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use = zend_ssa_next_use(ssa->ops, var, use);
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}
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phi = ssa->vars[var].phi_use_chain;
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while (phi) {
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var2 = phi->ssa_var;
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if (!ssa->vars[var2].no_val) {
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iterator->state = 9;
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iterator->phi = phi;
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return var2;
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}
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state_9:
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phi = zend_ssa_next_use_phi(ssa, var, phi);
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}
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#ifdef SYM_RANGE
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/* Process symbolic control-flow constraints */
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phi = ssa->vars[var].sym_use_chain;
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while (phi) {
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var2 = phi->ssa_var;
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if (!ssa->vars[var2].no_val) {
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iterator->state = 10;
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iterator->phi = phi;
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return var2;
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}
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state_10:
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phi = phi->sym_use_chain;
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}
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#endif
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iterator->state = 11;
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state_11:
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return -1;
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}
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/* }}} */
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static void zend_ssa_check_scc_var(const zend_op_array *op_array, zend_ssa *ssa, int var, int *index, zend_worklist_stack *stack, zend_worklist_stack *vstack, zend_scc_iterator *iterators) /* {{{ */
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{
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restart:
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zend_worklist_stack_push(vstack, var);
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iterators[var].state = 0;
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iterators[var].last = -1;
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ssa->vars[var].scc_entry = 1;
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ssa->vars[var].scc = *index;
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(*index)++;
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while (vstack->len > 0) {
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var = zend_worklist_stack_peek(vstack);
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while (1) {
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int var2;
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if (iterators[var].last >= 0) {
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/* finish edge */
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var2 = iterators[var].last;
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if (ssa->vars[var2].scc < ssa->vars[var].scc) {
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ssa->vars[var].scc = ssa->vars[var2].scc;
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ssa->vars[var].scc_entry = 0;
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}
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}
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var2 = zend_scc_next(op_array, ssa, var, iterators + var);
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iterators[var].last = var2;
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if (var2 < 0) break;
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/* begin edge */
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if (ssa->vars[var2].scc < 0) {
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var = var2;
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goto restart;
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}
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}
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/* finish visiting */
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zend_worklist_stack_pop(vstack);
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if (ssa->vars[var].scc_entry) {
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ssa->sccs--;
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while (stack->len > 0) {
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int var2 = zend_worklist_stack_peek(stack);
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if (ssa->vars[var2].scc < ssa->vars[var].scc) {
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break;
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}
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zend_worklist_stack_pop(stack);
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ssa->vars[var2].scc = ssa->sccs;
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(*index)--;
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}
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ssa->vars[var].scc = ssa->sccs;
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(*index)--;
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} else {
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zend_worklist_stack_push(stack, var);
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}
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}
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}
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/* }}} */
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ZEND_API int zend_ssa_find_sccs(const zend_op_array *op_array, zend_ssa *ssa) /* {{{ */
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{
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int index = 0;
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zend_worklist_stack stack, vstack;
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zend_scc_iterator *iterators;
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int j;
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ALLOCA_FLAG(stack_use_heap)
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ALLOCA_FLAG(vstack_use_heap)
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ALLOCA_FLAG(iterators_use_heap)
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iterators = do_alloca(sizeof(zend_scc_iterator) * ssa->vars_count, iterators_use_heap);
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ZEND_WORKLIST_STACK_ALLOCA(&vstack, ssa->vars_count, vstack_use_heap);
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ZEND_WORKLIST_STACK_ALLOCA(&stack, ssa->vars_count, stack_use_heap);
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/* Find SCCs using Pearce's algorithm. */
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ssa->sccs = ssa->vars_count;
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for (j = 0; j < ssa->vars_count; j++) {
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if (!ssa->vars[j].no_val && ssa->vars[j].scc < 0) {
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zend_ssa_check_scc_var(op_array, ssa, j, &index, &stack, &vstack, iterators);
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}
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}
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if (ssa->sccs) {
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/* Shift SCC indexes. */
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for (j = 0; j < ssa->vars_count; j++) {
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if (ssa->vars[j].scc >= 0) {
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ssa->vars[j].scc -= ssa->sccs;
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}
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}
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}
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ssa->sccs = ssa->vars_count - ssa->sccs;
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for (j = 0; j < ssa->vars_count; j++) {
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if (ssa->vars[j].scc >= 0) {
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int var = j;
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FOR_EACH_VAR_USAGE(var, CHECK_SCC_ENTRY);
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}
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}
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ZEND_WORKLIST_STACK_FREE_ALLOCA(&stack, stack_use_heap);
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ZEND_WORKLIST_STACK_FREE_ALLOCA(&vstack, vstack_use_heap);
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free_alloca(iterators, iterators_use_heap);
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return SUCCESS;
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}
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/* }}} */
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#endif
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ZEND_API int zend_ssa_find_false_dependencies(const zend_op_array *op_array, zend_ssa *ssa) /* {{{ */
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{
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zend_ssa_var *ssa_vars = ssa->vars;
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