php-src/Zend/Optimizer/zend_ssa.c

/*
   +----------------------------------------------------------------------+
   | Zend Engine, SSA - Static Single Assignment Form                     |
   +----------------------------------------------------------------------+
   | 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: Dmitry Stogov <dmitry@php.net>                              |
   |          Nikita Popov <nikic@php.net>                                |
   +----------------------------------------------------------------------+
*/

#include "zend_compile.h"
#include "zend_dfg.h"
#include "zend_ssa.h"
#include "zend_dump.h"
#include "zend_inference.h"
#include "Optimizer/zend_optimizer_internal.h"

static bool dominates(const zend_basic_block *blocks, int a, int b) {
	while (blocks[b].level > blocks[a].level) {
		b = blocks[b].idom;
	}
	return a == b;
}

static bool will_rejoin(
		const zend_cfg *cfg, const zend_dfg *dfg, const zend_basic_block *block,
		int other_successor, int exclude, int var) {
	int i;
	for (i = 0; i < block->predecessors_count; i++) {
		int predecessor = cfg->predecessors[block->predecessor_offset + i];
		if (predecessor == exclude) {
			continue;
		}

		/* The variable is changed in this predecessor,
		 * so we will not rejoin with the original value. */
		// TODO: This should not be limited to the direct predecessor block.
		if (DFG_ISSET(dfg->def, dfg->size, predecessor, var)) {
			continue;
		}

		/* The other successor dominates this predecessor,
		 * so we will get the original value from it. */
		if (dominates(cfg->blocks, other_successor, predecessor)) {
			return 1;
		}
	}
	return 0;
}

static bool needs_pi(const zend_op_array *op_array, const zend_dfg *dfg, const zend_ssa *ssa, int from, int to, int var) /* {{{ */
{
	const zend_basic_block *from_block, *to_block;
	int other_successor;

	if (!DFG_ISSET(dfg->in, dfg->size, to, var)) {
		/* Variable is not live, certainly won't benefit from pi */
		return 0;
	}

	/* Make sure that both successors of the from block aren't the same. Pi nodes are associated
	 * with predecessor blocks, so we can't distinguish which edge the pi belongs to. */
	from_block = &ssa->cfg.blocks[from];
	ZEND_ASSERT(from_block->successors_count == 2);
	if (from_block->successors[0] == from_block->successors[1]) {
		return 0;
	}

	to_block = &ssa->cfg.blocks[to];
	if (to_block->predecessors_count == 1) {
		/* Always place pi if one predecessor (an if branch) */
		return 1;
	}

	/* Check whether we will rejoin with the original value coming from the other successor,
	 * in which case the pi node will not have an effect. */
	other_successor = from_block->successors[0] == to
		? from_block->successors[1] : from_block->successors[0];
	return !will_rejoin(&ssa->cfg, dfg, to_block, other_successor, from, var);
}
/* }}} */

static zend_ssa_phi *add_pi(
		zend_arena **arena, const zend_op_array *op_array, zend_dfg *dfg, zend_ssa *ssa,
		int from, int to, int var) /* {{{ */
{
	zend_ssa_phi *phi;
	if (!needs_pi(op_array, dfg, ssa, from, to, var)) {
		return NULL;
	}

	phi = zend_arena_calloc(arena, 1,
		ZEND_MM_ALIGNED_SIZE(sizeof(zend_ssa_phi)) +
		ZEND_MM_ALIGNED_SIZE(sizeof(int) * ssa->cfg.blocks[to].predecessors_count) +
		sizeof(void*) * ssa->cfg.blocks[to].predecessors_count);
	phi->sources = (int*)(((char*)phi) + ZEND_MM_ALIGNED_SIZE(sizeof(zend_ssa_phi)));
	memset(phi->sources, 0xff, sizeof(int) * ssa->cfg.blocks[to].predecessors_count);
	phi->use_chains = (zend_ssa_phi**)(((char*)phi->sources) + ZEND_MM_ALIGNED_SIZE(sizeof(int) * ssa->cfg.blocks[to].predecessors_count));

	phi->pi = from;
	phi->var = var;
	phi->ssa_var = -1;
	phi->next = ssa->blocks[to].phis;
	ssa->blocks[to].phis = phi;

	/* Block "to" now defines "var" via the pi statement, so add it to the "def" set. Note that
	 * this is not entirely accurate, because the pi is actually placed along the edge from->to.
	 * If there is a back-edge to "to" this may result in non-minimal SSA form. */
	DFG_SET(dfg->def, dfg->size, to, var);

	/* If there are multiple predecessors in the target block, we need to place a phi there.
	 * However this can (generally) not be expressed in terms of dominance frontiers, so place it
	 * explicitly. dfg->use here really is dfg->phi, we're reusing the set. */
	if (ssa->cfg.blocks[to].predecessors_count > 1) {
		DFG_SET(dfg->use, dfg->size, to, var);
	}

	return phi;
}
/* }}} */

static void pi_range(
		zend_ssa_phi *phi, int min_var, int max_var, zend_long min, zend_long max,
		char underflow, char overflow, char negative) /* {{{ */
{
	zend_ssa_range_constraint *constraint = &phi->constraint.range;
	constraint->min_var = min_var;
	constraint->max_var = max_var;
	constraint->min_ssa_var = -1;
	constraint->max_ssa_var = -1;
	constraint->range.min = min;
	constraint->range.max = max;
	constraint->range.underflow = underflow;
	constraint->range.overflow = overflow;
	constraint->negative = negative ? NEG_INIT : NEG_NONE;
	phi->has_range_constraint = true;
}
/* }}} */

static inline void pi_range_equals(zend_ssa_phi *phi, int var, zend_long val) {
	pi_range(phi, var, var, val, val, 0, 0, 0);
}
static inline void pi_range_not_equals(zend_ssa_phi *phi, int var, zend_long val) {
	pi_range(phi, var, var, val, val, 0, 0, 1);
}
static inline void pi_range_min(zend_ssa_phi *phi, int var, zend_long val) {
	pi_range(phi, var, -1, val, ZEND_LONG_MAX, 0, 1, 0);
}
static inline void pi_range_max(zend_ssa_phi *phi, int var, zend_long val) {
	pi_range(phi, -1, var, ZEND_LONG_MIN, val, 1, 0, 0);
}

static void pi_type_mask(zend_ssa_phi *phi, uint32_t type_mask) {
	phi->has_range_constraint = false;
	phi->constraint.type.ce = NULL;
	phi->constraint.type.type_mask = MAY_BE_REF|MAY_BE_RC1|MAY_BE_RCN;
	phi->constraint.type.type_mask |= type_mask;
	if (type_mask & MAY_BE_NULL) {
		phi->constraint.type.type_mask |= MAY_BE_UNDEF;
	}
}
static inline void pi_not_type_mask(zend_ssa_phi *phi, uint32_t type_mask) {
	uint32_t relevant = MAY_BE_ANY|MAY_BE_ARRAY_KEY_ANY|MAY_BE_ARRAY_OF_ANY|MAY_BE_ARRAY_OF_REF;
	pi_type_mask(phi, ~type_mask & relevant);
}
static inline uint32_t mask_for_type_check(uint32_t type) {
	if (type & MAY_BE_ARRAY) {
		return type | (MAY_BE_ARRAY_KEY_ANY|MAY_BE_ARRAY_OF_ANY|MAY_BE_ARRAY_OF_REF);
	} else {
		return type;
	}
}

/* We can interpret $a + 5 == 0 as $a = 0 - 5, i.e. shift the adjustment to the other operand.
 * This negated adjustment is what is written into the "adjustment" parameter. */
static int find_adjusted_tmp_var(const zend_op_array *op_array, uint32_t build_flags, zend_op *opline, uint32_t var_num, zend_long *adjustment) /* {{{ */
{
	zend_op *op = opline;
	zval *zv;

	while (op != op_array->opcodes) {
		op--;
		if (op->result_type != IS_TMP_VAR || op->result.var != var_num) {
			continue;
		}

		if (op->opcode == ZEND_POST_DEC) {
			if (op->op1_type == IS_CV) {
				*adjustment = -1;
				return EX_VAR_TO_NUM(op->op1.var);
			}
		} else if (op->opcode == ZEND_POST_INC) {
			if (op->op1_type == IS_CV) {
				*adjustment = 1;
				return EX_VAR_TO_NUM(op->op1.var);
			}
		} else if (op->opcode == ZEND_ADD) {
			if (op->op1_type == IS_CV && op->op2_type == IS_CONST) {
				zv = CRT_CONSTANT_EX(op_array, op, op->op2);
				if (Z_TYPE_P(zv) == IS_LONG
				 && Z_LVAL_P(zv) != ZEND_LONG_MIN) {
					*adjustment = -Z_LVAL_P(zv);
					return EX_VAR_TO_NUM(op->op1.var);
				}
			} else if (op->op2_type == IS_CV && op->op1_type == IS_CONST) {
				zv = CRT_CONSTANT_EX(op_array, op, op->op1);
				if (Z_TYPE_P(zv) == IS_LONG
				 && Z_LVAL_P(zv) != ZEND_LONG_MIN) {
					*adjustment = -Z_LVAL_P(zv);
					return EX_VAR_TO_NUM(op->op2.var);
				}
			}
		} else if (op->opcode == ZEND_SUB) {
			if (op->op1_type == IS_CV && op->op2_type == IS_CONST) {
				zv = CRT_CONSTANT_EX(op_array, op, op->op2);
				if (Z_TYPE_P(zv) == IS_LONG) {
					*adjustment = Z_LVAL_P(zv);
					return EX_VAR_TO_NUM(op->op1.var);
				}
			}
		}
		break;
	}
	return -1;
}
/* }}} */

/* e-SSA construction: Pi placement (Pi is actually a Phi with single
 * source and constraint).
 * Order of Phis is important, Pis must be placed before Phis
 */
static void place_essa_pis(
		zend_arena **arena, const zend_script *script, const zend_op_array *op_array,
		uint32_t build_flags, zend_ssa *ssa, zend_dfg *dfg) /* {{{ */ {
	zend_basic_block *blocks = ssa->cfg.blocks;
	int j, blocks_count = ssa->cfg.blocks_count;
	for (j = 0; j < blocks_count; j++) {
		zend_ssa_phi *pi;
		zend_op *opline = op_array->opcodes + blocks[j].start + blocks[j].len - 1;
		int bt; /* successor block number if a condition is true */
		int bf; /* successor block number if a condition is false */

		if ((blocks[j].flags & ZEND_BB_REACHABLE) == 0 || blocks[j].len == 0) {
			continue;
		}
		/* the last instruction of basic block is conditional branch,
		 * based on comparison of CV(s)
		 */
		switch (opline->opcode) {
			case ZEND_JMPZ:
				bf = blocks[j].successors[0];
				bt = blocks[j].successors[1];
				break;
			case ZEND_JMPNZ:
				bt = blocks[j].successors[0];
				bf = blocks[j].successors[1];
				break;
			case ZEND_COALESCE:
				if (opline->op1_type == IS_CV) {
					int var = EX_VAR_TO_NUM(opline->op1.var);
					if ((pi = add_pi(arena, op_array, dfg, ssa, j, blocks[j].successors[0], var))) {
						pi_not_type_mask(pi, MAY_BE_NULL);
					}
				}
				continue;
			case ZEND_JMP_NULL:
				if (opline->op1_type == IS_CV) {
					int var = EX_VAR_TO_NUM(opline->op1.var);
					if ((pi = add_pi(arena, op_array, dfg, ssa, j, blocks[j].successors[1], var))) {
						pi_not_type_mask(pi, MAY_BE_NULL);
					}
				}
				continue;
			default:
				continue;
		}

		/* The following patterns all inspect the opline directly before the JMPZ opcode.
		 * Make sure that it is part of the same block, otherwise it might not be a dominating
		 * assignment. */
		if (blocks[j].len == 1) {
			continue;
		}

		if (opline->op1_type == IS_TMP_VAR &&
		    ((opline-1)->opcode == ZEND_IS_EQUAL ||
		     (opline-1)->opcode == ZEND_IS_NOT_EQUAL ||
		     (opline-1)->opcode == ZEND_IS_SMALLER ||
		     (opline-1)->opcode == ZEND_IS_SMALLER_OR_EQUAL) &&
		    opline->op1.var == (opline-1)->result.var) {
			int  var1 = -1;
			int  var2 = -1;
			zend_long val1 = 0;
			zend_long val2 = 0;
//			long val = 0;

			if ((opline-1)->op1_type == IS_CV) {
				var1 = EX_VAR_TO_NUM((opline-1)->op1.var);
			} else if ((opline-1)->op1_type == IS_TMP_VAR) {
				var1 = find_adjusted_tmp_var(
					op_array, build_flags, opline, (opline-1)->op1.var, &val2);
			}

			if ((opline-1)->op2_type == IS_CV) {
				var2 = EX_VAR_TO_NUM((opline-1)->op2.var);
			} else if ((opline-1)->op2_type == IS_TMP_VAR) {
				var2 = find_adjusted_tmp_var(
					op_array, build_flags, opline, (opline-1)->op2.var, &val1);
			}

			if (var1 >= 0 && var2 >= 0) {
				if (!zend_sub_will_overflow(val1, val2) && !zend_sub_will_overflow(val2, val1)) {
					zend_long tmp = val1;
					val1 -= val2;
					val2 -= tmp;
				} else {
					var1 = -1;
					var2 = -1;
				}
			} else if (var1 >= 0 && var2 < 0) {
				zend_long add_val2 = 0;
				if ((opline-1)->op2_type == IS_CONST) {
					zval *zv = CRT_CONSTANT_EX(op_array, (opline-1), (opline-1)->op2);

					if (Z_TYPE_P(zv) == IS_LONG) {
						add_val2 = Z_LVAL_P(zv);
					} else {
						var1 = -1;
					}
				} else {
					var1 = -1;
				}
				if (!zend_add_will_overflow(val2, add_val2)) {
					val2 += add_val2;
				} else {
					var1 = -1;
				}
			} else if (var1 < 0 && var2 >= 0) {
				zend_long add_val1 = 0;
				if ((opline-1)->op1_type == IS_CONST) {
					zval *zv = CRT_CONSTANT_EX(op_array, (opline-1), (opline-1)->op1);
					if (Z_TYPE_P(zv) == IS_LONG) {
						add_val1 = Z_LVAL_P(CRT_CONSTANT_EX(op_array, (opline-1), (opline-1)->op1));
					} else {
						var2 = -1;
					}
				} else {
					var2 = -1;
				}
				if (!zend_add_will_overflow(val1, add_val1)) {
					val1 += add_val1;
				} else {
					var2 = -1;
				}
			}

			if (var1 >= 0) {
				if ((opline-1)->opcode == ZEND_IS_EQUAL) {
					if ((pi = add_pi(arena, op_array, dfg, ssa, j, bt, var1))) {
						pi_range_equals(pi, var2, val2);
					}
					if ((pi = add_pi(arena, op_array, dfg, ssa, j, bf, var1))) {
						pi_range_not_equals(pi, var2, val2);
					}
				} else if ((opline-1)->opcode == ZEND_IS_NOT_EQUAL) {
					if ((pi = add_pi(arena, op_array, dfg, ssa, j, bf, var1))) {
						pi_range_equals(pi, var2, val2);
					}
					if ((pi = add_pi(arena, op_array, dfg, ssa, j, bt, var1))) {
						pi_range_not_equals(pi, var2, val2);
					}
				} else if ((opline-1)->opcode == ZEND_IS_SMALLER) {
					if (val2 > ZEND_LONG_MIN) {
						if ((pi = add_pi(arena, op_array, dfg, ssa, j, bt, var1))) {
							pi_range_max(pi, var2, val2-1);
						}
					}
					if ((pi = add_pi(arena, op_array, dfg, ssa, j, bf, var1))) {
						pi_range_min(pi, var2, val2);
					}
				} else if ((opline-1)->opcode == ZEND_IS_SMALLER_OR_EQUAL) {
					if ((pi = add_pi(arena, op_array, dfg, ssa, j, bt, var1))) {
						pi_range_max(pi, var2, val2);
					}
					if (val2 < ZEND_LONG_MAX) {
						if ((pi = add_pi(arena, op_array, dfg, ssa, j, bf, var1))) {
							pi_range_min(pi, var2, val2+1);
						}
					}
				}
			}
			if (var2 >= 0) {
				if((opline-1)->opcode == ZEND_IS_EQUAL) {
					if ((pi = add_pi(arena, op_array, dfg, ssa, j, bt, var2))) {
						pi_range_equals(pi, var1, val1);
					}
					if ((pi = add_pi(arena, op_array, dfg, ssa, j, bf, var2))) {
						pi_range_not_equals(pi, var1, val1);
					}
				} else if ((opline-1)->opcode == ZEND_IS_NOT_EQUAL) {
					if ((pi = add_pi(arena, op_array, dfg, ssa, j, bf, var2))) {
						pi_range_equals(pi, var1, val1);
					}
					if ((pi = add_pi(arena, op_array, dfg, ssa, j, bt, var2))) {
						pi_range_not_equals(pi, var1, val1);
					}
				} else if ((opline-1)->opcode == ZEND_IS_SMALLER) {
					if (val1 < ZEND_LONG_MAX) {
						if ((pi = add_pi(arena, op_array, dfg, ssa, j, bt, var2))) {
							pi_range_min(pi, var1, val1+1);
						}
					}
					if ((pi = add_pi(arena, op_array, dfg, ssa, j, bf, var2))) {
						pi_range_max(pi, var1, val1);
					}
				} else if ((opline-1)->opcode == ZEND_IS_SMALLER_OR_EQUAL) {
					if ((pi = add_pi(arena, op_array, dfg, ssa, j, bt, var2))) {
						pi_range_min(pi, var1, val1);
					}
					if (val1 > ZEND_LONG_MIN) {
						if ((pi = add_pi(arena, op_array, dfg, ssa, j, bf, var2))) {
							pi_range_max(pi, var1, val1-1);
						}
					}
				}
			}
		} else if (opline->op1_type == IS_TMP_VAR &&
		           ((opline-1)->opcode == ZEND_POST_INC ||
		            (opline-1)->opcode == ZEND_POST_DEC) &&
		           opline->op1.var == (opline-1)->result.var &&
		           (opline-1)->op1_type == IS_CV) {
			int var = EX_VAR_TO_NUM((opline-1)->op1.var);

			if ((opline-1)->opcode == ZEND_POST_DEC) {
				if ((pi = add_pi(arena, op_array, dfg, ssa, j, bf, var))) {
					pi_range_equals(pi, -1, -1);
				}
				if ((pi = add_pi(arena, op_array, dfg, ssa, j, bt, var))) {
					pi_range_not_equals(pi, -1, -1);
				}
			} else if ((opline-1)->opcode == ZEND_POST_INC) {
				if ((pi = add_pi(arena, op_array, dfg, ssa, j, bf, var))) {
					pi_range_equals(pi, -1, 1);
				}
				if ((pi = add_pi(arena, op_array, dfg, ssa, j, bt, var))) {
					pi_range_not_equals(pi, -1, 1);
				}
			}
		} else if (opline->op1_type == IS_TMP_VAR &&
		           ((opline-1)->opcode == ZEND_PRE_INC ||
		            (opline-1)->opcode == ZEND_PRE_DEC) &&
		           opline->op1.var == (opline-1)->result.var &&
		           (opline-1)->op1_type == IS_CV) {
			int var = EX_VAR_TO_NUM((opline-1)->op1.var);

			if ((pi = add_pi(arena, op_array, dfg, ssa, j, bf, var))) {
				pi_range_equals(pi, -1, 0);
			}
			/* speculative */
			if ((pi = add_pi(arena, op_array, dfg, ssa, j, bt, var))) {
				pi_range_not_equals(pi, -1, 0);
			}
		} else if (opline->op1_type == IS_TMP_VAR && (opline-1)->opcode == ZEND_TYPE_CHECK &&
				   opline->op1.var == (opline-1)->result.var && (opline-1)->op1_type == IS_CV) {
			int var = EX_VAR_TO_NUM((opline-1)->op1.var);
			uint32_t type = (opline-1)->extended_value;
			if ((pi = add_pi(arena, op_array, dfg, ssa, j, bt, var))) {
				pi_type_mask(pi, mask_for_type_check(type));
			}
			if (type != MAY_BE_RESOURCE) {
				/* is_resource() may return false for closed resources */
				if ((pi = add_pi(arena, op_array, dfg, ssa, j, bf, var))) {
					pi_not_type_mask(pi, mask_for_type_check(type));
				}
			}
		} else if (opline->op1_type == IS_TMP_VAR &&
				   ((opline-1)->opcode == ZEND_IS_IDENTICAL
					|| (opline-1)->opcode == ZEND_IS_NOT_IDENTICAL) &&
				   opline->op1.var == (opline-1)->result.var) {
			int var;
			zval *val;
			uint32_t type_mask;
			if ((opline-1)->op1_type == IS_CV && (opline-1)->op2_type == IS_CONST) {
				var = EX_VAR_TO_NUM((opline-1)->op1.var);
				val = CRT_CONSTANT_EX(op_array, (opline-1), (opline-1)->op2);
			} else if ((opline-1)->op1_type == IS_CONST && (opline-1)->op2_type == IS_CV) {
				var = EX_VAR_TO_NUM((opline-1)->op2.var);
				val = CRT_CONSTANT_EX(op_array, (opline-1), (opline-1)->op1);
			} else {
				continue;
			}

			/* We're interested in === null/true/false comparisons here, because they eliminate
			 * a type in the false-branch. Other === VAL comparisons are unlikely to be useful. */
			if (Z_TYPE_P(val) != IS_NULL && Z_TYPE_P(val) != IS_TRUE && Z_TYPE_P(val) != IS_FALSE) {
				continue;
			}

			type_mask = _const_op_type(val);
			if ((opline-1)->opcode == ZEND_IS_IDENTICAL) {
				if ((pi = add_pi(arena, op_array, dfg, ssa, j, bt, var))) {
					pi_type_mask(pi, type_mask);
				}
				if ((pi = add_pi(arena, op_array, dfg, ssa, j, bf, var))) {
					pi_not_type_mask(pi, type_mask);
				}
			} else {
				if ((pi = add_pi(arena, op_array, dfg, ssa, j, bf, var))) {
					pi_type_mask(pi, type_mask);
				}
				if ((pi = add_pi(arena, op_array, dfg, ssa, j, bt, var))) {
					pi_not_type_mask(pi, type_mask);
				}
			}
		} else if (opline->op1_type == IS_TMP_VAR && (opline-1)->opcode == ZEND_INSTANCEOF &&
				   opline->op1.var == (opline-1)->result.var && (opline-1)->op1_type == IS_CV &&
				   (opline-1)->op2_type == IS_CONST) {
			int var = EX_VAR_TO_NUM((opline-1)->op1.var);
			zend_string *lcname = Z_STR_P(CRT_CONSTANT_EX(op_array, (opline-1), (opline-1)->op2) + 1);
			zend_class_entry *ce = zend_optimizer_get_class_entry(script, op_array, lcname);
			if (!ce) {
				continue;
			}

			if ((pi = add_pi(arena, op_array, dfg, ssa, j, bt, var))) {
				pi_type_mask(pi, MAY_BE_OBJECT);
				pi->constraint.type.ce = ce;
			}
		}
	}
}
/* }}} */

static zend_always_inline int _zend_ssa_rename_op(const zend_op_array *op_array, const zend_op *opline, uint32_t k, uint32_t build_flags, int ssa_vars_count, zend_ssa_op *ssa_ops, int *var) /* {{{ */
{
	const zend_op *next;

	if (opline->op1_type & (IS_CV|IS_VAR|IS_TMP_VAR)) {
		ssa_ops[k].op1_use = var[EX_VAR_TO_NUM(opline->op1.var)];
		//USE_SSA_VAR(op_array->last_var + opline->op1.var)
	}
	if (opline->op2_type & (IS_CV|IS_VAR|IS_TMP_VAR)) {
		ssa_ops[k].op2_use = var[EX_VAR_TO_NUM(opline->op2.var)];
		//USE_SSA_VAR(op_array->last_var + opline->op2.var)
	}
	if ((build_flags & ZEND_SSA_USE_CV_RESULTS)
	 && opline->result_type == IS_CV
	 && opline->opcode != ZEND_RECV) {
		ssa_ops[k].result_use = var[EX_VAR_TO_NUM(opline->result.var)];
		//USE_SSA_VAR(op_array->last_var + opline->result.var)
	}

	switch (opline->opcode) {
		case ZEND_ASSIGN:
			if ((build_flags & ZEND_SSA_RC_INFERENCE) && opline->op2_type == IS_CV) {
				ssa_ops[k].op2_def = ssa_vars_count;
				var[EX_VAR_TO_NUM(opline->op2.var)] = ssa_vars_count;
				ssa_vars_count++;
				//NEW_SSA_VAR(opline->op2.var)
			}
			if (opline->op1_type == IS_CV) {
add_op1_def:
				ssa_ops[k].op1_def = ssa_vars_count;
				var[EX_VAR_TO_NUM(opline->op1.var)] = ssa_vars_count;
				ssa_vars_count++;
				//NEW_SSA_VAR(opline->op1.var)
			}
			break;
		case ZEND_ASSIGN_REF:
			if (opline->op2_type == IS_CV) {
				ssa_ops[k].op2_def = ssa_vars_count;
				var[EX_VAR_TO_NUM(opline->op2.var)] = ssa_vars_count;
				ssa_vars_count++;
				//NEW_SSA_VAR(opline->op2.var)
			}
			if (opline->op1_type == IS_CV) {
				goto add_op1_def;
			}
			break;
		case ZEND_ASSIGN_DIM:
		case ZEND_ASSIGN_OBJ:
			next = opline + 1;
			if (next->op1_type & (IS_CV|IS_VAR|IS_TMP_VAR)) {
				ssa_ops[k + 1].op1_use = var[EX_VAR_TO_NUM(next->op1.var)];
				//USE_SSA_VAR(op_array->last_var + next->op1.var);
				if (build_flags & ZEND_SSA_RC_INFERENCE && next->op1_type == IS_CV) {
					ssa_ops[k + 1].op1_def = ssa_vars_count;
					var[EX_VAR_TO_NUM(next->op1.var)] = ssa_vars_count;
					ssa_vars_count++;
					//NEW_SSA_VAR(next->op1.var)
				}
			}
			if (opline->op1_type == IS_CV) {
				ssa_ops[k].op1_def = ssa_vars_count;
				var[EX_VAR_TO_NUM(opline->op1.var)] = ssa_vars_count;
				ssa_vars_count++;
				//NEW_SSA_VAR(opline->op1.var)
			}
			break;
		case ZEND_ASSIGN_OBJ_REF:
			if (opline->op1_type == IS_CV) {
				ssa_ops[k].op1_def = ssa_vars_count;
				var[EX_VAR_TO_NUM(opline->op1.var)] = ssa_vars_count;
				ssa_vars_count++;
				//NEW_SSA_VAR(opline->op1.var)
			}
			next = opline + 1;
			if (next->op1_type & (IS_CV|IS_VAR|IS_TMP_VAR)) {
				ssa_ops[k + 1].op1_use = var[EX_VAR_TO_NUM(next->op1.var)];
				//USE_SSA_VAR(op_array->last_var + next->op1.var);
				if (next->op1_type == IS_CV) {
					ssa_ops[k + 1].op1_def = ssa_vars_count;
					var[EX_VAR_TO_NUM(next->op1.var)] = ssa_vars_count;
					ssa_vars_count++;
					//NEW_SSA_VAR(next->op1.var)
				}
			}
			break;
		case ZEND_ASSIGN_STATIC_PROP:
			next = opline + 1;
			if (next->op1_type & (IS_CV|IS_VAR|IS_TMP_VAR)) {
				ssa_ops[k + 1].op1_use = var[EX_VAR_TO_NUM(next->op1.var)];
				//USE_SSA_VAR(op_array->last_var + next->op1.var);
				if ((build_flags & ZEND_SSA_RC_INFERENCE) && next->op1_type == IS_CV) {
					ssa_ops[k + 1].op1_def = ssa_vars_count;
					var[EX_VAR_TO_NUM(next->op1.var)] = ssa_vars_count;
					ssa_vars_count++;
					//NEW_SSA_VAR(next->op1.var)
				}
			}
			break;
		case ZEND_ASSIGN_STATIC_PROP_REF:
			next = opline + 1;
			if (next->op1_type & (IS_CV|IS_VAR|IS_TMP_VAR)) {
				ssa_ops[k + 1].op1_use = var[EX_VAR_TO_NUM(next->op1.var)];
				//USE_SSA_VAR(op_array->last_var + next->op1.var);
				if (next->op1_type == IS_CV) {
					ssa_ops[k + 1].op1_def = ssa_vars_count;
					var[EX_VAR_TO_NUM(next->op1.var)] = ssa_vars_count;
					ssa_vars_count++;
					//NEW_SSA_VAR(next->op1.var)
				}
			}
			break;
		case ZEND_ASSIGN_STATIC_PROP_OP:
			next = opline + 1;
			if (next->op1_type & (IS_CV|IS_VAR|IS_TMP_VAR)) {
				ssa_ops[k + 1].op1_use = var[EX_VAR_TO_NUM(next->op1.var)];
				//USE_SSA_VAR(op_array->last_var + next->op1.var);
			}
			break;
		case ZEND_ASSIGN_DIM_OP:
		case ZEND_ASSIGN_OBJ_OP:
			if (opline->op1_type == IS_CV) {
				ssa_ops[k].op1_def = ssa_vars_count;
				var[EX_VAR_TO_NUM(opline->op1.var)] = ssa_vars_count;
				ssa_vars_count++;
				//NEW_SSA_VAR(opline->op1.var)
			}
			next = opline + 1;
			if (next->op1_type & (IS_CV|IS_VAR|IS_TMP_VAR)) {
				ssa_ops[k + 1].op1_use = var[EX_VAR_TO_NUM(next->op1.var)];
				//USE_SSA_VAR(op_array->last_var + next->op1.var);
			}
			break;
		case ZEND_ASSIGN_OP:
		case ZEND_PRE_INC:
		case ZEND_PRE_DEC:
		case ZEND_POST_INC:
		case ZEND_POST_DEC:
		case ZEND_BIND_GLOBAL:
		case ZEND_BIND_STATIC:
		case ZEND_BIND_INIT_STATIC_OR_JMP:
		case ZEND_SEND_VAR_NO_REF:
		case ZEND_SEND_VAR_NO_REF_EX:
		case ZEND_SEND_VAR_EX:
		case ZEND_SEND_FUNC_ARG:
		case ZEND_SEND_REF:
		case ZEND_SEND_UNPACK:
		case ZEND_FE_RESET_RW:
		case ZEND_MAKE_REF:
		case ZEND_PRE_INC_OBJ:
		case ZEND_PRE_DEC_OBJ:
		case ZEND_POST_INC_OBJ:
		case ZEND_POST_DEC_OBJ:
		case ZEND_UNSET_DIM:
		case ZEND_UNSET_OBJ:
		case ZEND_FETCH_DIM_W:
		case ZEND_FETCH_DIM_RW:
		case ZEND_FETCH_DIM_FUNC_ARG:
		case ZEND_FETCH_DIM_UNSET:
		case ZEND_FETCH_LIST_W:
			if (opline->op1_type == IS_CV) {
				goto add_op1_def;
			}
			break;
		case ZEND_SEND_VAR:
		case ZEND_CAST:
		case ZEND_QM_ASSIGN:
		case ZEND_JMP_SET:
		case ZEND_COALESCE:
		case ZEND_FE_RESET_R:
			if ((build_flags & ZEND_SSA_RC_INFERENCE) && opline->op1_type == IS_CV) {
				goto add_op1_def;
			}
			break;
		case ZEND_ADD_ARRAY_UNPACK:
			ssa_ops[k].result_use = var[EX_VAR_TO_NUM(opline->result.var)];
			break;
		case ZEND_ADD_ARRAY_ELEMENT:
			ssa_ops[k].result_use = var[EX_VAR_TO_NUM(opline->result.var)];
			ZEND_FALLTHROUGH;
		case ZEND_INIT_ARRAY:
			if (((build_flags & ZEND_SSA_RC_INFERENCE)
						|| (opline->extended_value & ZEND_ARRAY_ELEMENT_REF))
					&& opline->op1_type == IS_CV) {
				goto add_op1_def;
			}
			break;
		case ZEND_YIELD:
			if (opline->op1_type == IS_CV
					&& ((op_array->fn_flags & ZEND_ACC_RETURN_REFERENCE)
						|| (build_flags & ZEND_SSA_RC_INFERENCE))) {
				goto add_op1_def;
			}
			break;
		case ZEND_UNSET_CV:
			goto add_op1_def;
		case ZEND_VERIFY_RETURN_TYPE:
			if (opline->op1_type & (IS_TMP_VAR|IS_VAR|IS_CV)) {
				goto add_op1_def;
			}
			break;
		case ZEND_FE_FETCH_R:
		case ZEND_FE_FETCH_RW:
			if (opline->op2_type != IS_CV) {
				ssa_ops[k].op2_use = -1; /* not used */
			}
			ssa_ops[k].op2_def = ssa_vars_count;
			var[EX_VAR_TO_NUM(opline->op2.var)] = ssa_vars_count;
			ssa_vars_count++;
			//NEW_SSA_VAR(opline->op2.var)
			break;
		case ZEND_BIND_LEXICAL:
			if ((opline->extended_value & ZEND_BIND_REF) || (build_flags & ZEND_SSA_RC_INFERENCE)) {
				ssa_ops[k].op2_def = ssa_vars_count;
				var[EX_VAR_TO_NUM(opline->op2.var)] = ssa_vars_count;
				ssa_vars_count++;
				//NEW_SSA_VAR(opline->op2.var)
			}
			break;
		case ZEND_COPY_TMP:
			if (build_flags & ZEND_SSA_RC_INFERENCE) {
				ssa_ops[k].op1_def = ssa_vars_count;
				var[EX_VAR_TO_NUM(opline->op1.var)] = ssa_vars_count;
				ssa_vars_count++;
				//NEW_SSA_VAR(opline->op1.var)
			}
			break;
		default:
			break;
	}

	if (opline->result_type & (IS_CV|IS_VAR|IS_TMP_VAR)) {
		ssa_ops[k].result_def = ssa_vars_count;
		var[EX_VAR_TO_NUM(opline->result.var)] = ssa_vars_count;
		ssa_vars_count++;
		//NEW_SSA_VAR(op_array->last_var + opline->result.var)
	}

	return ssa_vars_count;
}
/* }}} */

ZEND_API int zend_ssa_rename_op(const zend_op_array *op_array, const zend_op *opline, uint32_t k, uint32_t build_flags, int ssa_vars_count, zend_ssa_op *ssa_ops, int *var) /* {{{ */
{
	return _zend_ssa_rename_op(op_array, opline, k, build_flags, ssa_vars_count, ssa_ops, var);
}
/* }}} */

static zend_result zend_ssa_rename(const zend_op_array *op_array, uint32_t build_flags, zend_ssa *ssa, int *var, int n) /* {{{ */
{
	zend_basic_block *blocks = ssa->cfg.blocks;
	zend_ssa_block *ssa_blocks = ssa->blocks;
	zend_ssa_op *ssa_ops = ssa->ops;
	int ssa_vars_count = ssa->vars_count;
	int i, j;
	zend_op *opline, *end;
	int *tmp = NULL;
	ALLOCA_FLAG(use_heap = 0);

	// FIXME: Can we optimize this copying out in some cases?
	if (blocks[n].next_child >= 0) {
		tmp = do_alloca(sizeof(int) * (op_array->last_var + op_array->T), use_heap);
		memcpy(tmp, var, sizeof(int) * (op_array->last_var + op_array->T));
		var = tmp;
	}

	if (ssa_blocks[n].phis) {
		zend_ssa_phi *phi = ssa_blocks[n].phis;
		do {
			if (phi->ssa_var < 0) {
				phi->ssa_var = ssa_vars_count;
				var[phi->var] = ssa_vars_count;
				ssa_vars_count++;
			} else {
				var[phi->var] = phi->ssa_var;
			}
			phi = phi->next;
		} while (phi);
	}

	opline = op_array->opcodes + blocks[n].start;
	end = opline + blocks[n].len;
	for (; opline < end; opline++) {
		uint32_t k = opline - op_array->opcodes;
		if (opline->opcode != ZEND_OP_DATA) {
			ssa_vars_count = _zend_ssa_rename_op(op_array, opline, k, build_flags, ssa_vars_count, ssa_ops, var);
		}
	}

	zend_ssa_op *fe_fetch_ssa_op = blocks[n].len != 0
			&& ((end-1)->opcode == ZEND_FE_FETCH_R || (end-1)->opcode == ZEND_FE_FETCH_RW)
			&& (end-1)->op2_type == IS_CV
		? &ssa_ops[blocks[n].start + blocks[n].len - 1] : NULL;
	for (i = 0; i < blocks[n].successors_count; i++) {
		int succ = blocks[n].successors[i];
		zend_ssa_phi *p;
		for (p = ssa_blocks[succ].phis; p; p = p->next) {
			if (p->pi == n) {
				/* e-SSA Pi */
				if (p->has_range_constraint) {
					if (p->constraint.range.min_var >= 0) {
						p->constraint.range.min_ssa_var = var[p->constraint.range.min_var];
					}
					if (p->constraint.range.max_var >= 0) {
						p->constraint.range.max_ssa_var = var[p->constraint.range.max_var];
					}
				}
				for (j = 0; j < blocks[succ].predecessors_count; j++) {
					p->sources[j] = var[p->var];
				}
				if (p->ssa_var < 0) {
					p->ssa_var = ssa_vars_count;
					ssa_vars_count++;
				}
			} else if (p->pi < 0) {
				/* Normal Phi */
				for (j = 0; j < blocks[succ].predecessors_count; j++)
					if (ssa->cfg.predecessors[blocks[succ].predecessor_offset + j] == n) {
						break;
					}
				ZEND_ASSERT(j < blocks[succ].predecessors_count);
				p->sources[j] = var[p->var];
				if (fe_fetch_ssa_op && i == 0 && p->sources[j] == fe_fetch_ssa_op->op2_def) {
					/* On the exit edge of an FE_FETCH, use the pre-modification value instead. */
					p->sources[j] = fe_fetch_ssa_op->op2_use;
				}
			}
		}
		for (p = ssa_blocks[succ].phis; p && (p->pi >= 0); p = p->next) {
			if (p->pi == n) {
				zend_ssa_phi *q = p->next;
				while (q) {
					if (q->pi < 0 && q->var == p->var) {
						for (j = 0; j < blocks[succ].predecessors_count; j++) {
							if (ssa->cfg.predecessors[blocks[succ].predecessor_offset + j] == n) {
								break;
							}
						}
						ZEND_ASSERT(j < blocks[succ].predecessors_count);
						q->sources[j] = p->ssa_var;
					}
					q = q->next;
				}
			}
		}
	}

	ssa->vars_count = ssa_vars_count;

	j = blocks[n].children;
	while (j >= 0) {
		// FIXME: Tail call optimization?
		if (zend_ssa_rename(op_array, build_flags, ssa, var, j) == FAILURE)
			return FAILURE;
		j = blocks[j].next_child;
	}

	if (tmp) {
		free_alloca(tmp, use_heap);
	}

	return SUCCESS;
}
/* }}} */

ZEND_API zend_result zend_build_ssa(zend_arena **arena, const zend_script *script, const zend_op_array *op_array, uint32_t build_flags, zend_ssa *ssa) /* {{{ */
{
	zend_basic_block *blocks = ssa->cfg.blocks;
	zend_ssa_block *ssa_blocks;
	int blocks_count = ssa->cfg.blocks_count;
	uint32_t set_size;
	zend_bitset def, in, phi;
	int *var = NULL;
	int i, j, k, changed;
	zend_dfg dfg;
	ALLOCA_FLAG(dfg_use_heap)
	ALLOCA_FLAG(var_use_heap)

	if ((blocks_count * (op_array->last_var + op_array->T)) > 4 * 1024 * 1024) {
	    /* Don't build SSA for very big functions */
		return FAILURE;
	}

	ssa_blocks = zend_arena_calloc(arena, blocks_count, sizeof(zend_ssa_block));
	ssa->blocks = ssa_blocks;

	/* Compute Variable Liveness */
	dfg.vars = op_array->last_var + op_array->T;
	dfg.size = set_size = zend_bitset_len(dfg.vars);
	dfg.tmp = do_alloca((set_size * sizeof(zend_ulong)) * (blocks_count * 4 + 1), dfg_use_heap);
	memset(dfg.tmp, 0, (set_size * sizeof(zend_ulong)) * (blocks_count * 4 + 1));
	dfg.def = dfg.tmp + set_size;
	dfg.use = dfg.def + set_size * blocks_count;
	dfg.in  = dfg.use + set_size * blocks_count;
	dfg.out = dfg.in  + set_size * blocks_count;

	zend_build_dfg(op_array, &ssa->cfg, &dfg, build_flags);

	if (build_flags & ZEND_SSA_DEBUG_LIVENESS) {
		zend_dump_dfg(op_array, &ssa->cfg, &dfg);
	}

	def = dfg.def;
	in  = dfg.in;

	/* Reuse the "use" set, as we no longer need it */
	phi = dfg.use;
	zend_bitset_clear(phi, set_size * blocks_count);

	/* Place e-SSA pis. This will add additional "def" points, so it must
	 * happen before def propagation. */
	place_essa_pis(arena, script, op_array, build_flags, ssa, &dfg);

	/* SSA construction, Step 1: Propagate "def" sets in merge points */
	do {
		changed = 0;
		for (j = 0; j < blocks_count; j++) {
			zend_bitset def_j = def + j * set_size, phi_j = phi + j * set_size;
			if ((blocks[j].flags & ZEND_BB_REACHABLE) == 0) {
				continue;
			}
			if (blocks[j].predecessors_count > 1) {
				if (blocks[j].flags & ZEND_BB_IRREDUCIBLE_LOOP) {
					/* Prevent any values from flowing into irreducible loops by
					   replacing all incoming values with explicit phis.  The
					   register allocator depends on this property.  */
					zend_bitset_union(phi_j, in + (j * set_size), set_size);
				} else {
					for (k = 0; k < blocks[j].predecessors_count; k++) {
						i = ssa->cfg.predecessors[blocks[j].predecessor_offset + k];
						while (i != -1 && i != blocks[j].idom) {
							zend_bitset_union_with_intersection(
								phi_j, phi_j, def + (i * set_size), in + (j * set_size), set_size);
							i = blocks[i].idom;
						}
					}
				}
				if (!zend_bitset_subset(phi_j, def_j, set_size)) {
					zend_bitset_union(def_j, phi_j, set_size);
					changed = 1;
				}
			}
		}
	} while (changed);

	/* SSA construction, Step 2: Phi placement based on Dominance Frontiers */
	var = do_alloca(sizeof(int) * (op_array->last_var + op_array->T), var_use_heap);
	if (!var) {
		free_alloca(dfg.tmp, dfg_use_heap);
		return FAILURE;
	}

	for (j = 0; j < blocks_count; j++) {
		if ((blocks[j].flags & ZEND_BB_REACHABLE) == 0) {
			continue;
		}
		if (!zend_bitset_empty(phi + j * set_size, set_size)) {
			ZEND_BITSET_REVERSE_FOREACH(phi + j * set_size, set_size, i) {
				zend_ssa_phi *phi = zend_arena_calloc(arena, 1,
					ZEND_MM_ALIGNED_SIZE(sizeof(zend_ssa_phi)) +
					ZEND_MM_ALIGNED_SIZE(sizeof(int) * blocks[j].predecessors_count) +
					sizeof(void*) * blocks[j].predecessors_count);

				phi->sources = (int*)(((char*)phi) + ZEND_MM_ALIGNED_SIZE(sizeof(zend_ssa_phi)));
				memset(phi->sources, 0xff, sizeof(int) * blocks[j].predecessors_count);
				phi->use_chains = (zend_ssa_phi**)(((char*)phi->sources) + ZEND_MM_ALIGNED_SIZE(sizeof(int) * ssa->cfg.blocks[j].predecessors_count));

				phi->pi = -1;
				phi->var = i;
				phi->ssa_var = -1;

				/* Place phis after pis */
				{
					zend_ssa_phi **pp = &ssa_blocks[j].phis;
					while (*pp) {
						if ((*pp)->pi < 0) {
							break;
						}
						pp = &(*pp)->next;
					}
					phi->next = *pp;
					*pp = phi;
				}
			} ZEND_BITSET_FOREACH_END();
		}
	}

	if (build_flags & ZEND_SSA_DEBUG_PHI_PLACEMENT) {
		zend_dump_phi_placement(op_array, ssa);
	}

	/* SSA construction, Step 3: Renaming */
	ssa->ops = zend_arena_calloc(arena, op_array->last, sizeof(zend_ssa_op));
	memset(ssa->ops, 0xff, op_array->last * sizeof(zend_ssa_op));
	memset(var + op_array->last_var, 0xff, op_array->T * sizeof(int));
	/* Create uninitialized SSA variables for each CV */
	for (j = 0; j < op_array->last_var; j++) {
		var[j] = j;
	}
	ssa->vars_count = op_array->last_var;
	if (zend_ssa_rename(op_array, build_flags, ssa, var, 0) == FAILURE) {
		free_alloca(var, var_use_heap);
		free_alloca(dfg.tmp, dfg_use_heap);
		return FAILURE;
	}

	free_alloca(var, var_use_heap);
	free_alloca(dfg.tmp, dfg_use_heap);

	return SUCCESS;
}
/* }}} */

ZEND_API void zend_ssa_compute_use_def_chains(zend_arena **arena, const zend_op_array *op_array, zend_ssa *ssa) /* {{{ */
{
	zend_ssa_var *ssa_vars;
	int i;

	if (!ssa->vars) {
		ssa->vars = zend_arena_calloc(arena, ssa->vars_count, sizeof(zend_ssa_var));
	}
	ssa_vars = ssa->vars;

	for (i = 0; i < op_array->last_var; i++) {
		ssa_vars[i].var = i;
		ssa_vars[i].scc = -1;
		ssa_vars[i].definition = -1;
		ssa_vars[i].use_chain = -1;
	}
	for (i = op_array->last_var; i < ssa->vars_count; i++) {
		ssa_vars[i].var = -1;
		ssa_vars[i].scc = -1;
		ssa_vars[i].definition = -1;
		ssa_vars[i].use_chain = -1;
	}

	for (i = op_array->last - 1; i >= 0; i--) {
		zend_ssa_op *op = ssa->ops + i;

		if (op->op1_use >= 0) {
			op->op1_use_chain = ssa_vars[op->op1_use].use_chain;
			ssa_vars[op->op1_use].use_chain = i;
		}
		if (op->op2_use >= 0 && op->op2_use != op->op1_use) {
			op->op2_use_chain = ssa_vars[op->op2_use].use_chain;
			ssa_vars[op->op2_use].use_chain = i;
		}
		if (op->result_use >= 0 && op->result_use != op->op1_use && op->result_use != op->op2_use) {
			op->res_use_chain = ssa_vars[op->result_use].use_chain;
			ssa_vars[op->result_use].use_chain = i;
		}
		if (op->op1_def >= 0) {
			ssa_vars[op->op1_def].var = EX_VAR_TO_NUM(op_array->opcodes[i].op1.var);
			ssa_vars[op->op1_def].definition = i;
		}
		if (op->op2_def >= 0) {
			ssa_vars[op->op2_def].var = EX_VAR_TO_NUM(op_array->opcodes[i].op2.var);
			ssa_vars[op->op2_def].definition = i;
		}
		if (op->result_def >= 0) {
			ssa_vars[op->result_def].var = EX_VAR_TO_NUM(op_array->opcodes[i].result.var);
			ssa_vars[op->result_def].definition = i;
		}
	}

	for (i = 0; i < ssa->cfg.blocks_count; i++) {
		zend_ssa_phi *phi = ssa->blocks[i].phis;
		while (phi) {
			phi->block = i;
			ssa_vars[phi->ssa_var].var = phi->var;
			ssa_vars[phi->ssa_var].definition_phi = phi;
			if (phi->pi >= 0) {
				zend_ssa_phi *p;

				ZEND_ASSERT(phi->sources[0] >= 0);
				p = ssa_vars[phi->sources[0]].phi_use_chain;
				while (p && p != phi) {
					p = zend_ssa_next_use_phi(ssa, phi->sources[0], p);
				}
				if (!p) {
					phi->use_chains[0] = ssa_vars[phi->sources[0]].phi_use_chain;
					ssa_vars[phi->sources[0]].phi_use_chain = phi;
				}
				if (phi->has_range_constraint) {
					/* min and max variables can't be used together */
					zend_ssa_range_constraint *constraint = &phi->constraint.range;
					if (constraint->min_ssa_var >= 0) {
						phi->sym_use_chain = ssa_vars[constraint->min_ssa_var].sym_use_chain;
						ssa_vars[constraint->min_ssa_var].sym_use_chain = phi;
					} else if (constraint->max_ssa_var >= 0) {
						phi->sym_use_chain = ssa_vars[constraint->max_ssa_var].sym_use_chain;
						ssa_vars[constraint->max_ssa_var].sym_use_chain = phi;
					}
				}
			} else {
				int j;

				for (j = 0; j < ssa->cfg.blocks[i].predecessors_count; j++) {
					zend_ssa_phi *p;

					ZEND_ASSERT(phi->sources[j] >= 0);
					p = ssa_vars[phi->sources[j]].phi_use_chain;
					while (p && p != phi) {
						p = zend_ssa_next_use_phi(ssa, phi->sources[j], p);
					}
					if (!p) {
						phi->use_chains[j] = ssa_vars[phi->sources[j]].phi_use_chain;
						ssa_vars[phi->sources[j]].phi_use_chain = phi;
					}
				}
			}
			phi = phi->next;
		}
	}

	/* Mark indirectly accessed variables */
	for (i = 0; i < op_array->last_var; i++) {
		if ((ssa->cfg.flags & ZEND_FUNC_INDIRECT_VAR_ACCESS)) {
			ssa_vars[i].alias = SYMTABLE_ALIAS;
		} else if (zend_string_equals_literal(op_array->vars[i], "http_response_header")) {
			ssa_vars[i].alias = HTTP_RESPONSE_HEADER_ALIAS;
		}
	}
	for (i = op_array->last_var; i < ssa->vars_count; i++) {
		if (ssa_vars[i].var < op_array->last_var) {
			ssa_vars[i].alias = ssa_vars[ssa_vars[i].var].alias;
		}
	}
}
/* }}} */

void zend_ssa_unlink_use_chain(zend_ssa *ssa, int op, int var) /* {{{ */
{
	if (ssa->vars[var].use_chain == op) {
		ssa->vars[var].use_chain = zend_ssa_next_use(ssa->ops, var, op);
		return;
	}
	int use = ssa->vars[var].use_chain;

	while (use >= 0) {
		if (ssa->ops[use].result_use == var) {
			if (ssa->ops[use].res_use_chain == op) {
				ssa->ops[use].res_use_chain = zend_ssa_next_use(ssa->ops, var, op);
				return;
			} else {
				use = ssa->ops[use].res_use_chain;
			}
		} else if (ssa->ops[use].op1_use == var) {
			if (ssa->ops[use].op1_use_chain == op) {
				ssa->ops[use].op1_use_chain = zend_ssa_next_use(ssa->ops, var, op);
				return;
			} else {
				use = ssa->ops[use].op1_use_chain;
			}
		} else if (ssa->ops[use].op2_use == var) {
			if (ssa->ops[use].op2_use_chain == op) {
				ssa->ops[use].op2_use_chain = zend_ssa_next_use(ssa->ops, var, op);
				return;
			} else {
				use = ssa->ops[use].op2_use_chain;
			}
		} else {
			break;
		}
	}
	/* something wrong */
	ZEND_UNREACHABLE();
}
/* }}} */

void zend_ssa_replace_use_chain(zend_ssa *ssa, int op, int new_op, int var) /* {{{ */
{
	if (ssa->vars[var].use_chain == op) {
		ssa->vars[var].use_chain = new_op;
		return;
	} else {
		int use = ssa->vars[var].use_chain;

		while (use >= 0) {
			if (ssa->ops[use].result_use == var) {
				if (ssa->ops[use].res_use_chain == op) {
					ssa->ops[use].res_use_chain = new_op;
					return;
				} else {
					use = ssa->ops[use].res_use_chain;
				}
			} else if (ssa->ops[use].op1_use == var) {
				if (ssa->ops[use].op1_use_chain == op) {
					ssa->ops[use].op1_use_chain = new_op;
					return;
				} else {
					use = ssa->ops[use].op1_use_chain;
				}
			} else if (ssa->ops[use].op2_use == var) {
				if (ssa->ops[use].op2_use_chain == op) {
					ssa->ops[use].op2_use_chain = new_op;
					return;
				} else {
					use = ssa->ops[use].op2_use_chain;
				}
			} else {
				break;
			}
		}
	}
	/* something wrong */
	ZEND_UNREACHABLE();
}
/* }}} */

void zend_ssa_remove_instr(zend_ssa *ssa, zend_op *opline, zend_ssa_op *ssa_op) /* {{{ */
{
	if (ssa_op->result_use >= 0) {
		zend_ssa_unlink_use_chain(ssa, ssa_op - ssa->ops, ssa_op->result_use);
		ssa_op->result_use = -1;
		ssa_op->res_use_chain = -1;
	}
	if (ssa_op->op1_use >= 0) {
		if (ssa_op->op1_use != ssa_op->op2_use) {
			zend_ssa_unlink_use_chain(ssa, ssa_op - ssa->ops, ssa_op->op1_use);
		} else {
			ssa_op->op2_use_chain = ssa_op->op1_use_chain;
		}
		ssa_op->op1_use = -1;
		ssa_op->op1_use_chain = -1;
	}
	if (ssa_op->op2_use >= 0) {
		zend_ssa_unlink_use_chain(ssa, ssa_op - ssa->ops, ssa_op->op2_use);
		ssa_op->op2_use = -1;
		ssa_op->op2_use_chain = -1;
	}

	/* We let the caller make sure that all defs are gone */
	ZEND_ASSERT(ssa_op->result_def == -1);
	ZEND_ASSERT(ssa_op->op1_def == -1);
	ZEND_ASSERT(ssa_op->op2_def == -1);

	MAKE_NOP(opline);
}
/* }}} */

static inline zend_ssa_phi **zend_ssa_next_use_phi_ptr(zend_ssa *ssa, int var, zend_ssa_phi *p) /* {{{ */
{
	if (p->pi >= 0) {
		return &p->use_chains[0];
	} else {
		int j;
		for (j = 0; j < ssa->cfg.blocks[p->block].predecessors_count; j++) {
			if (p->sources[j] == var) {
				return &p->use_chains[j];
			}
		}
	}
	ZEND_UNREACHABLE();
	return NULL;
}
/* }}} */

/* May be called even if source is not used in the phi (useful when removing uses in a phi
 * with multiple identical operands) */
static inline void zend_ssa_remove_use_of_phi_source(zend_ssa *ssa, zend_ssa_phi *phi, int source, zend_ssa_phi *next_use_phi) /* {{{ */
{
	zend_ssa_phi **cur = &ssa->vars[source].phi_use_chain;
	while (*cur && *cur != phi) {
		cur = zend_ssa_next_use_phi_ptr(ssa, source, *cur);
	}
	if (*cur) {
		*cur = next_use_phi;
	}
}
/* }}} */

static void zend_ssa_remove_uses_of_phi_sources(zend_ssa *ssa, zend_ssa_phi *phi) /* {{{ */
{
	int source;
	FOREACH_PHI_SOURCE(phi, source) {
		zend_ssa_remove_use_of_phi_source(ssa, phi, source, zend_ssa_next_use_phi(ssa, source, phi));
	} FOREACH_PHI_SOURCE_END();
}
/* }}} */

static void zend_ssa_remove_phi_from_block(zend_ssa *ssa, zend_ssa_phi *phi) /* {{{ */
{
	zend_ssa_block *block = &ssa->blocks[phi->block];
	zend_ssa_phi **cur = &block->phis;
	while (*cur != phi) {
		ZEND_ASSERT(*cur != NULL);
		cur = &(*cur)->next;
	}
	*cur = (*cur)->next;
}
/* }}} */

void zend_ssa_remove_defs_of_instr(zend_ssa *ssa, zend_ssa_op *ssa_op) /* {{{ */
{
	if (ssa_op->op1_def >= 0) {
		zend_ssa_remove_uses_of_var(ssa, ssa_op->op1_def);
		zend_ssa_remove_op1_def(ssa, ssa_op);
	}
	if (ssa_op->op2_def >= 0) {
		zend_ssa_remove_uses_of_var(ssa, ssa_op->op2_def);
		zend_ssa_remove_op2_def(ssa, ssa_op);
	}
	if (ssa_op->result_def >= 0) {
		zend_ssa_remove_uses_of_var(ssa, ssa_op->result_def);
		zend_ssa_remove_result_def(ssa, ssa_op);
	}
}
/* }}} */

static inline void zend_ssa_remove_phi_source(zend_ssa *ssa, zend_ssa_phi *phi, int pred_offset, int predecessors_count) /* {{{ */
{
	int j, var_num = phi->sources[pred_offset];
	zend_ssa_phi *next_phi = phi->use_chains[pred_offset];

	predecessors_count--;
	if (pred_offset < predecessors_count) {
		memmove(phi->sources + pred_offset, phi->sources + pred_offset + 1, (predecessors_count - pred_offset) * sizeof(uint32_t));
		memmove(phi->use_chains + pred_offset, phi->use_chains + pred_offset + 1, (predecessors_count - pred_offset) * sizeof(zend_ssa_phi*));
	}

	/* Check if they same var is used in a different phi operand as well, in this case we don't
	 * need to adjust the use chain (but may have to move the next pointer). */
	for (j = 0; j < predecessors_count; j++) {
		if (phi->sources[j] == var_num) {
			if (j < pred_offset) {
				ZEND_ASSERT(next_phi == NULL);
			} else if (j >= pred_offset) {
				phi->use_chains[j] = next_phi;
			}
			return;
		}
	}

	/* Variable only used in one operand, remove the phi from the use chain. */
	zend_ssa_remove_use_of_phi_source(ssa, phi, var_num, next_phi);
}
/* }}} */

void zend_ssa_remove_phi(zend_ssa *ssa, zend_ssa_phi *phi) /* {{{ */
{
	ZEND_ASSERT(phi->ssa_var >= 0);
	ZEND_ASSERT(ssa->vars[phi->ssa_var].use_chain < 0
		&& ssa->vars[phi->ssa_var].phi_use_chain == NULL);
	zend_ssa_remove_uses_of_phi_sources(ssa, phi);
	zend_ssa_remove_phi_from_block(ssa, phi);
	ssa->vars[phi->ssa_var].definition_phi = NULL;
	phi->ssa_var = -1;
}
/* }}} */

void zend_ssa_remove_uses_of_var(zend_ssa *ssa, int var_num) /* {{{ */
{
	zend_ssa_var *var = &ssa->vars[var_num];
	zend_ssa_phi *phi;
	int use;
	FOREACH_PHI_USE(var, phi) {
		int i, end = NUM_PHI_SOURCES(phi);
		for (i = 0; i < end; i++) {
			if (phi->sources[i] == var_num) {
				phi->use_chains[i] = NULL;
			}
		}
	} FOREACH_PHI_USE_END();
	var->phi_use_chain = NULL;
	FOREACH_USE(var, use) {
		zend_ssa_op *ssa_op = &ssa->ops[use];
		if (ssa_op->op1_use == var_num) {
			ssa_op->op1_use = -1;
			ssa_op->op1_use_chain = -1;
		}
		if (ssa_op->op2_use == var_num) {
			ssa_op->op2_use = -1;
			ssa_op->op2_use_chain = -1;
		}
		if (ssa_op->result_use == var_num) {
			ssa_op->result_use = -1;
			ssa_op->res_use_chain = -1;
		}
	} FOREACH_USE_END();
	var->use_chain = -1;
}
/* }}} */

void zend_ssa_remove_predecessor(zend_ssa *ssa, int from, int to) /* {{{ */
{
	zend_basic_block *next_block = &ssa->cfg.blocks[to];
	zend_ssa_block *next_ssa_block = &ssa->blocks[to];
	zend_ssa_phi *phi;
	int j;

	/* Find at which predecessor offset this block is referenced */
	int pred_offset = -1;
	int *predecessors = &ssa->cfg.predecessors[next_block->predecessor_offset];

	for (j = 0; j < next_block->predecessors_count; j++) {
		if (predecessors[j] == from) {
			pred_offset = j;
			break;
		}
	}

	/* If there are duplicate successors, the predecessors may have been removed in
	 * a previous iteration already. */
	if (pred_offset == -1) {
		return;
	}

	/* For phis in successor blocks, remove the operands associated with this block */
	for (phi = next_ssa_block->phis; phi; phi = phi->next) {
		if (phi->pi >= 0) {
			if (phi->pi == from) {
				zend_ssa_rename_var_uses(ssa, phi->ssa_var, phi->sources[0], /* update_types */ 0);
				zend_ssa_remove_phi(ssa, phi);
			}
		} else {
			ZEND_ASSERT(phi->sources[pred_offset] >= 0);
			zend_ssa_remove_phi_source(ssa, phi, pred_offset, next_block->predecessors_count);
		}
	}

	/* Remove this predecessor */
	next_block->predecessors_count--;
	if (pred_offset < next_block->predecessors_count) {
		predecessors = &ssa->cfg.predecessors[next_block->predecessor_offset + pred_offset];
		memmove(predecessors, predecessors + 1, (next_block->predecessors_count - pred_offset) * sizeof(uint32_t));
	}
}
/* }}} */

void zend_ssa_remove_block(zend_op_array *op_array, zend_ssa *ssa, int i) /* {{{ */
{
	zend_basic_block *block = &ssa->cfg.blocks[i];
	zend_ssa_block *ssa_block = &ssa->blocks[i];
	zend_ssa_phi *phi;
	int j;

	block->flags &= ~ZEND_BB_REACHABLE;

	/* Removes phis in this block */
	for (phi = ssa_block->phis; phi; phi = phi->next) {
		zend_ssa_remove_uses_of_var(ssa, phi->ssa_var);
		zend_ssa_remove_phi(ssa, phi);
	}

	/* Remove instructions in this block */
	for (j = block->start; j < block->start + block->len; j++) {
		if (op_array->opcodes[j].opcode == ZEND_NOP) {
			continue;
		}

		zend_ssa_remove_defs_of_instr(ssa, &ssa->ops[j]);
		zend_ssa_remove_instr(ssa, &op_array->opcodes[j], &ssa->ops[j]);
	}

	zend_ssa_remove_block_from_cfg(ssa, i);
}
/* }}} */

void zend_ssa_remove_block_from_cfg(zend_ssa *ssa, int i) /* {{{ */
{
	zend_basic_block *block = &ssa->cfg.blocks[i];
	int *predecessors;
	int j, s;

	for (s = 0; s < block->successors_count; s++) {
		zend_ssa_remove_predecessor(ssa, i, block->successors[s]);
	}

	/* Remove successors of predecessors */
	predecessors = &ssa->cfg.predecessors[block->predecessor_offset];
	for (j = 0; j < block->predecessors_count; j++) {
		if (predecessors[j] >= 0) {
			zend_basic_block *prev_block = &ssa->cfg.blocks[predecessors[j]];

			for (s = 0; s < prev_block->successors_count; s++) {
				if (prev_block->successors[s] == i) {
					memmove(prev_block->successors + s,
							prev_block->successors + s + 1,
							sizeof(int) * (prev_block->successors_count - s - 1));
					prev_block->successors_count--;
					s--;
				}
			}
		}
	}

	block->successors_count = 0;
	block->predecessors_count = 0;

	/* Remove from dominators tree */
	if (block->idom >= 0) {
		j = ssa->cfg.blocks[block->idom].children;
		if (j == i) {
			ssa->cfg.blocks[block->idom].children = block->next_child;
		} else if (j >= 0) {
			while (ssa->cfg.blocks[j].next_child >= 0) {
				if (ssa->cfg.blocks[j].next_child == i) {
					ssa->cfg.blocks[j].next_child = block->next_child;
					break;
				}
				j = ssa->cfg.blocks[j].next_child;
			}
		}
	}
	block->idom = -1;
	block->level = -1;
	block->children = -1;
	block->next_child = -1;
}
/* }}} */

static void propagate_phi_type_widening(zend_ssa *ssa, int var) /* {{{ */
{
	zend_ssa_phi *phi;
	FOREACH_PHI_USE(&ssa->vars[var], phi) {
		if (ssa->var_info[var].type & ~ssa->var_info[phi->ssa_var].type) {
			ssa->var_info[phi->ssa_var].type |= ssa->var_info[var].type;
			propagate_phi_type_widening(ssa, phi->ssa_var);
		}
	} FOREACH_PHI_USE_END();
}
/* }}} */

void zend_ssa_rename_var_uses(zend_ssa *ssa, int old, int new, bool update_types) /* {{{ */
{
	zend_ssa_var *old_var = &ssa->vars[old];
	zend_ssa_var *new_var = &ssa->vars[new];
	int use;
	zend_ssa_phi *phi;

	ZEND_ASSERT(old >= 0 && new >= 0);
	ZEND_ASSERT(old != new);

	/* Only a no_val is both variables are */
	new_var->no_val &= old_var->no_val;

	/* Update ssa_op use chains */
	FOREACH_USE(old_var, use) {
		zend_ssa_op *ssa_op = &ssa->ops[use];

		/* If the op already uses the new var, don't add the op to the use
		 * list again. Instead move the use_chain to the correct operand. */
		bool add_to_use_chain = 1;
		if (ssa_op->result_use == new) {
			add_to_use_chain = 0;
		} else if (ssa_op->op1_use == new) {
			if (ssa_op->result_use == old) {
				ssa_op->res_use_chain = ssa_op->op1_use_chain;
				ssa_op->op1_use_chain = -1;
			}
			add_to_use_chain = 0;
		} else if (ssa_op->op2_use == new) {
			if (ssa_op->result_use == old) {
				ssa_op->res_use_chain = ssa_op->op2_use_chain;
				ssa_op->op2_use_chain = -1;
			} else if (ssa_op->op1_use == old) {
				ssa_op->op1_use_chain = ssa_op->op2_use_chain;
				ssa_op->op2_use_chain = -1;
			}
			add_to_use_chain = 0;
		}

		/* Perform the actual renaming */
		if (ssa_op->result_use == old) {
			ssa_op->result_use = new;
		}
		if (ssa_op->op1_use == old) {
			ssa_op->op1_use = new;
		}
		if (ssa_op->op2_use == old) {
			ssa_op->op2_use = new;
		}

		/* Add op to use chain of new var (if it isn't already). We use the
		 * first use chain of (result, op1, op2) that has the new variable. */
		if (add_to_use_chain) {
			if (ssa_op->result_use == new) {
				ssa_op->res_use_chain = new_var->use_chain;
				new_var->use_chain = use;
			} else if (ssa_op->op1_use == new) {
				ssa_op->op1_use_chain = new_var->use_chain;
				new_var->use_chain = use;
			} else {
				ZEND_ASSERT(ssa_op->op2_use == new);
				ssa_op->op2_use_chain = new_var->use_chain;
				new_var->use_chain = use;
			}
		}
	} FOREACH_USE_END();
	old_var->use_chain = -1;

	/* Update phi use chains */
	FOREACH_PHI_USE(old_var, phi) {
		int j;
		bool after_first_new_source = 0;

		/* If the phi already uses the new var, find its use chain, as we may
		 * need to move it to a different source operand. */
		zend_ssa_phi **existing_use_chain_ptr = NULL;
		for (j = 0; j < ssa->cfg.blocks[phi->block].predecessors_count; j++) {
			if (phi->sources[j] == new) {
				existing_use_chain_ptr = &phi->use_chains[j];
				break;
			}
		}

		for (j = 0; j < ssa->cfg.blocks[phi->block].predecessors_count; j++) {
			if (phi->sources[j] == new) {
				after_first_new_source = 1;
			} else if (phi->sources[j] == old) {
				phi->sources[j] = new;

				/* Either move existing use chain to this source, or add the phi
				 * to the phi use chain of the new variables. Do this only once. */
				if (!after_first_new_source) {
					if (existing_use_chain_ptr) {
						phi->use_chains[j] = *existing_use_chain_ptr;
						*existing_use_chain_ptr = NULL;
					} else {
						phi->use_chains[j] = new_var->phi_use_chain;
						new_var->phi_use_chain = phi;
					}
					after_first_new_source = 1;
				} else {
					phi->use_chains[j] = NULL;
				}
			}
		}

		/* Make sure phi result types are not incorrectly narrow after renaming.
		 * This should not normally happen, but can occur if we DCE an assignment
		 * or unset and there is an improper phi-indirected use lateron. */
		// TODO Alternatively we could rerun type-inference after DCE
		if (update_types && (ssa->var_info[new].type & ~ssa->var_info[phi->ssa_var].type)) {
			ssa->var_info[phi->ssa_var].type |= ssa->var_info[new].type;
			propagate_phi_type_widening(ssa, phi->ssa_var);
		}
	} FOREACH_PHI_USE_END();
	old_var->phi_use_chain = NULL;
}
/* }}} */