/*
   +----------------------------------------------------------------------+
   | Zend Engine, SCCP - Sparse Conditional Constant Propagation          |
   +----------------------------------------------------------------------+
   | Copyright (c) 1998-2018 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: Nikita Popov <nikic@php.net>                                |
   +----------------------------------------------------------------------+
*/

#include "php.h"
#include "zend_type_info.h"
#include "ZendAccelerator.h"
#include "Optimizer/zend_optimizer_internal.h"
#include "Optimizer/zend_call_graph.h"
#include "Optimizer/scdf.h"
#include "Optimizer/zend_dump.h"
#include "ext/standard/php_string.h"

/* This implements sparse conditional constant propagation (SCCP) based on the SCDF framework. The
 * used value lattice is defined as follows:
 *
 * BOT < {constant values} < TOP
 *
 * TOP indicates an underdefined value, i.e. that we do not yet know the value of variable.
 * BOT indicates an overdefined value, i.e. that we know the variable to be non-constant.
 *
 * All variables are optimistically initialized to TOP, apart from the implicit variables defined
 * at the start of the first block. Note that variables that MAY_BE_REF are *not* initialized to
 * BOT. We rely on the fact that any operation resulting in a reference will produce a BOT anyway.
 * This is better because such operations might never be reached due to the conditional nature of
 * the algorithm.
 *
 * The meet operation for phi functions is defined as follows:
 * BOT + any = BOT
 * TOP + any = any
 * C_i + C_i = C_i (i.e. two equal constants)
 * C_i + C_j = BOT (i.e. two different constants)
 *
 * When evaluating instructions TOP and BOT are handled as follows:
 * a) If any operand is BOT, the result is BOT. The main exception to this is op1 of ASSIGN, which
 *    is ignored. However, if the op1 MAY_BE_REF we do have to propagate the BOT.
 * b) Otherwise, if the instruction can never be evaluated (either in general, or with the
 *    specific modifiers) the result is BOT.
 * c) Otherwise, if any operand is TOP, the result is TOP.
 * d) Otherwise (at this point all operands are known and constant), if we can compute the result
 *    for these specific constants (without throwing notices or similar) then that is the result.
 * e) Otherwise the result is BOT.
 *
 * It is sometimes possible to determine a result even if one argument is TOP / BOT, e.g. for things
 * like BOT*0. Right now we don't bother with this -- the only thing that is done is evaluating
 * TYPE_CHECKS based on the type information.
 *
 * Feasible successors for conditional branches are determined as follows:
 * a) If we don't support the branch type or branch on BOT, all successors are feasible.
 * b) Otherwise, if we branch on TOP none of the successors are feasible.
 * c) Otherwise (we branch on a constant), the feasible successors are marked based on the constant
 *    (usually only one successor will be feasible).
 */

#if 0
#define SCP_DEBUG(...) php_printf(__VA_ARGS__)
#else
#define SCP_DEBUG(...)
#endif

typedef struct _sccp_ctx {
	scdf_ctx scdf;
	zend_call_info **call_map;
	zval *values;
	zval top;
	zval bot;
} sccp_ctx;

#define TOP ((zend_uchar)-1) 
#define BOT ((zend_uchar)-2)
#define IS_TOP(zv) (Z_TYPE_P(zv) == TOP)
#define IS_BOT(zv) (Z_TYPE_P(zv) == BOT)

#define MAKE_TOP(zv) (Z_TYPE_INFO_P(zv) = TOP)
#define MAKE_BOT(zv) (Z_TYPE_INFO_P(zv) = BOT)

static inline zend_bool value_known(zval *zv) {
	return !IS_TOP(zv) && !IS_BOT(zv);
}

/* Sets new value for variable and ensures that it is lower or equal
 * the previous one in the constant propagation lattice. */
static void set_value(scdf_ctx *scdf, sccp_ctx *ctx, int var, zval *new) {
	zval *value = &ctx->values[var];
	if (IS_BOT(value) || IS_TOP(new)) {
		return;
	}

	if (IS_BOT(new)) {
		SCP_DEBUG("Lowering var %d to BOT\n", var);
	} else {
		SCP_DEBUG("Lowering var %d to %Z\n", var, new);
	}

	if (IS_TOP(value) || IS_BOT(new)) {
		zval_ptr_dtor_nogc(value);
		ZVAL_COPY(value, new);
		scdf_add_to_worklist(scdf, var);
		return;
	}

#if ZEND_DEBUG
	ZEND_ASSERT(zend_is_identical(value, new));
#endif
}

static zval *get_op1_value(sccp_ctx *ctx, zend_op *opline, zend_ssa_op *ssa_op) {
	if (opline->op1_type == IS_CONST) {
		return CT_CONSTANT_EX(ctx->scdf.op_array, opline->op1.constant);
	} else if (ssa_op->op1_use != -1) {
		return &ctx->values[ssa_op->op1_use];
	} else {
		return NULL;
	}
}

static zval *get_op2_value(sccp_ctx *ctx, zend_op *opline, zend_ssa_op *ssa_op) {
	if (opline->op2_type == IS_CONST) {
		return CT_CONSTANT_EX(ctx->scdf.op_array, opline->op2.constant);
	} else if (ssa_op->op2_use != -1) {
		return &ctx->values[ssa_op->op2_use];
	} else {
		return NULL;
	}
}

static zend_bool can_replace_op1(
		const zend_op_array *op_array, zend_op *opline, zend_ssa_op *ssa_op) {
	switch (opline->opcode) {
		case ZEND_PRE_INC:
		case ZEND_PRE_DEC:
		case ZEND_PRE_INC_OBJ:
		case ZEND_PRE_DEC_OBJ:
		case ZEND_POST_INC:
		case ZEND_POST_DEC:
		case ZEND_POST_INC_OBJ:
		case ZEND_POST_DEC_OBJ:
		case ZEND_ASSIGN:
		case ZEND_ASSIGN_REF:
		case ZEND_ASSIGN_DIM:
		case ZEND_ASSIGN_OBJ:
		case ZEND_ASSIGN_ADD:
		case ZEND_ASSIGN_SUB:
		case ZEND_ASSIGN_MUL:
		case ZEND_ASSIGN_DIV:
		case ZEND_ASSIGN_MOD:
		case ZEND_ASSIGN_SL:
		case ZEND_ASSIGN_SR:
		case ZEND_ASSIGN_CONCAT:
		case ZEND_ASSIGN_BW_OR:
		case ZEND_ASSIGN_BW_AND:
		case ZEND_ASSIGN_BW_XOR:
		case ZEND_ASSIGN_POW:
		case ZEND_FETCH_DIM_W:
		case ZEND_FETCH_DIM_RW:
		case ZEND_FETCH_DIM_UNSET:
		case ZEND_FETCH_DIM_FUNC_ARG:
		case ZEND_FETCH_OBJ_W:
		case ZEND_FETCH_OBJ_RW:
		case ZEND_FETCH_OBJ_UNSET:
		case ZEND_FETCH_OBJ_FUNC_ARG:
		case ZEND_UNSET_DIM:
		case ZEND_UNSET_OBJ:
		case ZEND_SEND_REF:
		case ZEND_SEND_VAR_EX:
		case ZEND_SEND_UNPACK:
		case ZEND_SEND_ARRAY:
		case ZEND_SEND_USER:
		case ZEND_FE_RESET_RW:
			return 0;
		/* Do not accept CONST */
		case ZEND_VERIFY_ABSTRACT_CLASS:
		case ZEND_ADD_INTERFACE:
		case ZEND_ADD_TRAIT:
		case ZEND_BIND_TRAITS:
		case ZEND_ROPE_ADD:
		case ZEND_ROPE_END:
		case ZEND_BIND_STATIC:
		case ZEND_BIND_GLOBAL:
		case ZEND_MAKE_REF:
		case ZEND_UNSET_CV:
		case ZEND_ISSET_ISEMPTY_CV:
		case ZEND_INSTANCEOF:
			return 0;
		case ZEND_INIT_ARRAY:
		case ZEND_ADD_ARRAY_ELEMENT:
			return !(opline->extended_value & ZEND_ARRAY_ELEMENT_REF);
		case ZEND_YIELD:
			return !(op_array->fn_flags & ZEND_ACC_RETURN_REFERENCE);
		case ZEND_VERIFY_RETURN_TYPE:
			// TODO: This would require a non-local change ???
			return 0;
		default:
			if (ssa_op->op1_def != -1) {
				ZEND_ASSERT(0);
				return 0;
			}
	}

	return 1;
}

static zend_bool can_replace_op2(
		const zend_op_array *op_array, zend_op *opline, zend_ssa_op *ssa_op) {
	switch (opline->opcode) {
		/* Do not accept CONST */
		case ZEND_DECLARE_INHERITED_CLASS:
		case ZEND_DECLARE_INHERITED_CLASS_DELAYED:
		case ZEND_DECLARE_ANON_INHERITED_CLASS:
		case ZEND_BIND_LEXICAL:
		case ZEND_FE_FETCH_R:
		case ZEND_FE_FETCH_RW:
			return 0;
	}
	return 1;
}

static zend_bool try_replace_op1(
		sccp_ctx *ctx, zend_op *opline, zend_ssa_op *ssa_op, int var, zval *value) {
	if (ssa_op->op1_use == var && can_replace_op1(ctx->scdf.op_array, opline, ssa_op)) {
		zval zv;
		ZVAL_COPY(&zv, value);
		if (zend_optimizer_update_op1_const(ctx->scdf.op_array, opline, &zv)) {
			/* Reconstruct SSA */
			int num;
			zend_basic_block *block;

			switch (opline->opcode) {
				case ZEND_JMPZ:
					if (zend_is_true(&zv)) {
						MAKE_NOP(opline);
						num = ctx->scdf.ssa->cfg.map[opline - ctx->scdf.op_array->opcodes];
						block = &ctx->scdf.ssa->cfg.blocks[num];
						if (block->successors_count == 2) {
							if (block->successors[1] != block->successors[0]) {
								zend_ssa_remove_predecessor(ctx->scdf.ssa, num, block->successors[0]);
							}
							block->successors_count = 1;
							block->successors[0] = block->successors[1];
						}
					} else {
						opline->opcode = ZEND_JMP;
						COPY_NODE(opline->op1, opline->op2);
						num = ctx->scdf.ssa->cfg.map[opline - ctx->scdf.op_array->opcodes];
						block = &ctx->scdf.ssa->cfg.blocks[num];
						if (block->successors_count == 2) {
							if (block->successors[1] != block->successors[0]) {
								zend_ssa_remove_predecessor(ctx->scdf.ssa, num, block->successors[1]);
							}
							block->successors_count = 1;
						}
					}
					break;
				case ZEND_JMPNZ:
					if (zend_is_true(&zv)) {
						opline->opcode = ZEND_JMP;
						COPY_NODE(opline->op1, opline->op2);
						num = ctx->scdf.ssa->cfg.map[opline - ctx->scdf.op_array->opcodes];
						block = &ctx->scdf.ssa->cfg.blocks[num];
						if (block->successors_count == 2) {
							if (block->successors[1] != block->successors[0]) {
								zend_ssa_remove_predecessor(ctx->scdf.ssa, num, block->successors[1]);
							}
							block->successors_count = 1;
						}
					} else {
						MAKE_NOP(opline);
						num = ctx->scdf.ssa->cfg.map[opline - ctx->scdf.op_array->opcodes];
						block = &ctx->scdf.ssa->cfg.blocks[num];
						if (block->successors_count == 2) {
							if (block->successors[1] != block->successors[0]) {
								zend_ssa_remove_predecessor(ctx->scdf.ssa, num, block->successors[0]);
							}
							block->successors_count = 1;
							block->successors[0] = block->successors[1];
						}
					}
					break;
				case ZEND_JMPZNZ:
					if (zend_is_true(&zv)) {
						zend_op *target_opline = ZEND_OFFSET_TO_OPLINE(opline, opline->extended_value);
						ZEND_SET_OP_JMP_ADDR(opline, opline->op1, target_opline);
						num = ctx->scdf.ssa->cfg.map[opline - ctx->scdf.op_array->opcodes];
						block = &ctx->scdf.ssa->cfg.blocks[num];
						if (block->successors_count == 2) {
							if (block->successors[1] != block->successors[0]) {
								zend_ssa_remove_predecessor(ctx->scdf.ssa, num, block->successors[0]);
							}
							block->successors_count = 1;
							block->successors[0] = block->successors[1];
						}
					} else {
						zend_op *target_opline = ZEND_OP2_JMP_ADDR(opline);
						ZEND_SET_OP_JMP_ADDR(opline, opline->op1, target_opline);
						num = ctx->scdf.ssa->cfg.map[opline - ctx->scdf.op_array->opcodes];
						block = &ctx->scdf.ssa->cfg.blocks[num];
						if (block->successors_count == 2) {
							if (block->successors[1] != block->successors[0]) {
								zend_ssa_remove_predecessor(ctx->scdf.ssa, num, block->successors[1]);
							}
							block->successors_count = 1;
						}
					}
					opline->op1_type = IS_UNUSED;
					opline->extended_value = 0;
					opline->opcode = ZEND_JMP;
					break;
				default:
					break;
			}
			return 1;
		} else {
			// TODO: check the following special cases ???
			switch (opline->opcode) {
				case ZEND_FETCH_LIST:
				case ZEND_CASE:
				case ZEND_SWITCH_STRING:
				case ZEND_SWITCH_LONG:
					if (Z_TYPE(zv) == IS_STRING) {
						zend_string_hash_val(Z_STR(zv));
					}
					opline->op1.constant = zend_optimizer_add_literal(ctx->scdf.op_array, &zv);
					opline->op1_type = IS_CONST;
					return 1;
			}
			zval_ptr_dtor_nogc(&zv);
		}
	}
	return 0;
}

static zend_bool try_replace_op2(
		sccp_ctx *ctx, zend_op *opline, zend_ssa_op *ssa_op, int var, zval *value) {
	if (ssa_op->op2_use == var && can_replace_op2(ctx->scdf.op_array, opline, ssa_op)) {
		zval zv;
		ZVAL_COPY(&zv, value);
		if (zend_optimizer_update_op2_const(ctx->scdf.op_array, opline, &zv)) {
			return 1;
		} else {
			zval_ptr_dtor_nogc(&zv);
		}
	}
	return 0;
}

static inline int zval_to_string_offset(zend_long *result, zval *op) {
	switch (Z_TYPE_P(op)) {
		case IS_LONG:
			*result = Z_LVAL_P(op);
			return SUCCESS;
		case IS_STRING:
			if (IS_LONG == is_numeric_string(
					Z_STRVAL_P(op), Z_STRLEN_P(op), result, NULL, 0)) {
				return SUCCESS;
			}
			return FAILURE;
		default:
			return FAILURE;
	}
}

static inline int fetch_array_elem(zval **result, zval *op1, zval *op2) {
	switch (Z_TYPE_P(op2)) {
		case IS_NULL:
			*result = zend_hash_find(Z_ARR_P(op1), ZSTR_EMPTY_ALLOC());
			return SUCCESS;
		case IS_FALSE:
			*result = zend_hash_index_find(Z_ARR_P(op1), 0);
			return SUCCESS;
		case IS_TRUE:
			*result = zend_hash_index_find(Z_ARR_P(op1), 1);
			return SUCCESS;
		case IS_LONG:
			*result = zend_hash_index_find(Z_ARR_P(op1), Z_LVAL_P(op2));
			return SUCCESS;
		case IS_DOUBLE:
			*result = zend_hash_index_find(Z_ARR_P(op1), zend_dval_to_lval(Z_DVAL_P(op2)));
			return SUCCESS;
		case IS_STRING:
			*result = zend_symtable_find(Z_ARR_P(op1), Z_STR_P(op2));
			return SUCCESS;
		default:
			return FAILURE;
	}
}

static inline int ct_eval_fetch_dim(zval *result, zval *op1, zval *op2, int support_strings) {
	if (Z_TYPE_P(op1) == IS_ARRAY) {
		zval *value;
		if (fetch_array_elem(&value, op1, op2) == SUCCESS && value) {
			ZVAL_COPY(result, value);
			return SUCCESS;
		}
	} else if (support_strings && Z_TYPE_P(op1) == IS_STRING) {
		zend_long index;
		if (zval_to_string_offset(&index, op2) == FAILURE) {
			return FAILURE;
		}
		if (index >= 0 && index < Z_STRLEN_P(op1)) {
			ZVAL_STR(result, zend_string_init(&Z_STRVAL_P(op1)[index], 1, 0));
			return SUCCESS;
		}
	}
	return FAILURE;
}

static inline int ct_eval_isset_dim(zval *result, uint32_t extended_value, zval *op1, zval *op2) {
	if (Z_TYPE_P(op1) == IS_ARRAY) {
		zval *value;
		if (fetch_array_elem(&value, op1, op2) == FAILURE) {
			return FAILURE;
		}
		if (extended_value & ZEND_ISSET) {
			ZVAL_BOOL(result, value && Z_TYPE_P(value) != IS_NULL);
		} else {
			ZEND_ASSERT(extended_value & ZEND_ISEMPTY);
			ZVAL_BOOL(result, !value || !zend_is_true(value));
		}
		return SUCCESS;
	} else if (Z_TYPE_P(op1) == IS_STRING) {
		// TODO
		return FAILURE;
	} else {
		ZVAL_BOOL(result, extended_value != ZEND_ISSET);
		return SUCCESS;
	}
}

static inline int ct_eval_add_array_elem(zval *result, zval *value, zval *key) {
	if (!key) {
		if ((value = zend_hash_next_index_insert(Z_ARR_P(result), value))) {
			Z_TRY_ADDREF_P(value);
			return SUCCESS;
		}
		return FAILURE;
	}

	switch (Z_TYPE_P(key)) {
		case IS_NULL:
			value = zend_hash_update(Z_ARR_P(result), ZSTR_EMPTY_ALLOC(), value);
			break;
		case IS_FALSE:
			value = zend_hash_index_update(Z_ARR_P(result), 0, value);
			break;
		case IS_TRUE:
			value = zend_hash_index_update(Z_ARR_P(result), 1, value);
			break;
		case IS_LONG:
			value = zend_hash_index_update(Z_ARR_P(result), Z_LVAL_P(key), value);
			break;
		case IS_DOUBLE:
			value = zend_hash_index_update(
				Z_ARR_P(result), zend_dval_to_lval(Z_DVAL_P(key)), value);
			break;
		case IS_STRING:
			value = zend_symtable_update(Z_ARR_P(result), Z_STR_P(key), value);
			break;
		default:
			return FAILURE;
	}

	Z_TRY_ADDREF_P(value);
	return SUCCESS;
}

static inline int ct_eval_assign_dim(zval *result, zval *value, zval *key) {
	switch (Z_TYPE_P(result)) {
		case IS_NULL:
		case IS_FALSE:
			array_init(result);
			/* break missing intentionally */
		case IS_ARRAY:
			return ct_eval_add_array_elem(result, value, key);
		case IS_STRING:
			// TODO Before enabling this case, make sure ARRAY_DIM result op is correct
#if 0
			zend_long index;
			zend_string *new_str, *value_str;
			if (!key || Z_TYPE_P(value) == IS_ARRAY
					|| zval_to_string_offset(&index, key) == FAILURE || index < 0) {
				return FAILURE;
			}

			if (index >= Z_STRLEN_P(result)) {
				new_str = zend_string_alloc(index + 1, 0);
				memcpy(ZSTR_VAL(new_str), Z_STRVAL_P(result), Z_STRLEN_P(result));
				memset(ZSTR_VAL(new_str) + Z_STRLEN_P(result), ' ', index - Z_STRLEN_P(result));
				ZSTR_VAL(new_str)[index + 1] = 0;
			} else {
				new_str = zend_string_init(Z_STRVAL_P(result), Z_STRLEN_P(result), 0);
			}

			value_str = zval_get_string(value);
			ZVAL_STR(result, new_str);
			Z_STRVAL_P(result)[index] = ZSTR_VAL(value_str)[0];
			zend_string_release(value_str);
#endif
			return FAILURE;
		default:
			return FAILURE;
	}
}

static inline int ct_eval_incdec(zval *result, zend_uchar opcode, zval *op1) {
	ZVAL_COPY(result, op1);
	if (opcode == ZEND_PRE_INC || opcode == ZEND_POST_INC) {
		increment_function(result);
	} else {
		decrement_function(result);
	}
	return SUCCESS;
}

static inline int ct_eval_isset_isempty(zval *result, uint32_t extended_value, zval *op1) {
	if (extended_value & ZEND_ISSET) {
		ZVAL_BOOL(result, Z_TYPE_P(op1) != IS_NULL);
	} else {
		ZEND_ASSERT(extended_value & ZEND_ISEMPTY);
		ZVAL_BOOL(result, !zend_is_true(op1));
	}
	return SUCCESS;
}

static inline void ct_eval_type_check(zval *result, uint32_t type, zval *op1) {
	if (type == _IS_BOOL) {
		ZVAL_BOOL(result, Z_TYPE_P(op1) == IS_TRUE || Z_TYPE_P(op1) == IS_FALSE);
	} else {
		ZVAL_BOOL(result, Z_TYPE_P(op1) == type);
	}
}

static inline int ct_eval_in_array(zval *result, uint32_t extended_value, zval *op1, zval *op2) {
	HashTable *ht;
	zend_bool res;

	if (Z_TYPE_P(op2) != IS_ARRAY) {
		return FAILURE;
	}
	ht = Z_ARRVAL_P(op2);
	if (EXPECTED(Z_TYPE_P(op1) == IS_STRING)) {
		res = zend_hash_exists(ht, Z_STR_P(op1));
	} else if (extended_value) {
		if (EXPECTED(Z_TYPE_P(op1) == IS_LONG)) {
			res = zend_hash_index_exists(ht, Z_LVAL_P(op1));
		} else {
			res = 0;
		}
	} else if (Z_TYPE_P(op1) <= IS_FALSE) {
		res = zend_hash_exists(ht, ZSTR_EMPTY_ALLOC());
	} else {
		zend_string *key;
		zval key_tmp, result_tmp;

		res = 0;
		ZEND_HASH_FOREACH_STR_KEY(ht, key) {
			ZVAL_STR(&key_tmp, key);
			compare_function(&result_tmp, op1, &key_tmp);
			if (Z_LVAL(result_tmp) == 0) {
				res = 1;
				break;
			}
		} ZEND_HASH_FOREACH_END();
	}
	ZVAL_BOOL(result, res);
	return SUCCESS;
}

/* The functions chosen here are simple to implement and either likely to affect a branch,
 * or just happened to be commonly used with constant operands in WP (need to test other
 * applications as well, of course). */
static inline int ct_eval_func_call(
		zval *result, zend_string *name, uint32_t num_args, zval **args) {
	uint32_t i;
	zend_execute_data *execute_data;
	zend_function *func;
	int overflow;

	if (num_args == 0) {
		if (zend_string_equals_literal(name, "get_magic_quotes_gpc")
				|| zend_string_equals_literal(name, "get_magic_quotes_gpc_runtime")
				|| zend_string_equals_literal(name, "php_sapi_name")
				|| zend_string_equals_literal(name, "imagetypes")
				|| zend_string_equals_literal(name, "phpversion")) {
			/* pass */
		} else {
			return FAILURE;
		}
	} else if (num_args == 1) {
		if (zend_string_equals_literal(name, "chr")) {
			zend_long c;
			if (Z_TYPE_P(args[0]) != IS_LONG) {
				return FAILURE;
			}

			c = Z_LVAL_P(args[0]) & 0xff;
			ZVAL_INTERNED_STR(result, ZSTR_CHAR(c));
			return SUCCESS;
		} else if (zend_string_equals_literal(name, "count")) {
			if (Z_TYPE_P(args[0]) != IS_ARRAY) {
				return FAILURE;
			}

			ZVAL_LONG(result, zend_hash_num_elements(Z_ARRVAL_P(args[0])));
			return SUCCESS;
		} else if (zend_string_equals_literal(name, "ini_get")) {
			zend_ini_entry *ini_entry;

			if (Z_TYPE_P(args[0]) != IS_STRING) {
				return FAILURE;
			}

			ini_entry = zend_hash_find_ptr(EG(ini_directives), Z_STR_P(args[0]));
			if (!ini_entry) {
				ZVAL_FALSE(result);
			} else if (ini_entry->modifiable != ZEND_INI_SYSTEM) {
				return FAILURE;
			} else if (ini_entry->value) {
				ZVAL_STR_COPY(result, ini_entry->value);
			} else {
				ZVAL_EMPTY_STRING(result);
			}
			return SUCCESS;
		} else if (zend_string_equals_literal(name, "trim")
				|| zend_string_equals_literal(name, "rtrim")
				|| zend_string_equals_literal(name, "ltrim")
				|| zend_string_equals_literal(name, "str_split")
				|| zend_string_equals_literal(name, "preg_quote")
				|| zend_string_equals_literal(name, "base64_encode")
				|| zend_string_equals_literal(name, "base64_decode")
				|| zend_string_equals_literal(name, "urlencode")
				|| zend_string_equals_literal(name, "urldecode")
				|| zend_string_equals_literal(name, "rawurlencode")
				|| zend_string_equals_literal(name, "rawurldecode")
				|| zend_string_equals_literal(name, "php_uname")) {
			if (Z_TYPE_P(args[0]) != IS_STRING) {
				return FAILURE;
			}
			/* pass */
		} else if (zend_string_equals_literal(name, "array_keys")
				|| zend_string_equals_literal(name, "array_values")) {
			if (Z_TYPE_P(args[0]) != IS_ARRAY) {
				return FAILURE;
			}
			/* pass */
		} else if (zend_string_equals_literal(name, "array_flip")) {
			zval *entry;

			if (Z_TYPE_P(args[0]) != IS_ARRAY) {
				return FAILURE;
			}
			ZEND_HASH_FOREACH_VAL(Z_ARRVAL_P(args[0]), entry) {
				if (Z_TYPE_P(entry) != IS_LONG && Z_TYPE_P(entry) != IS_STRING) {
					return FAILURE;
				}
			} ZEND_HASH_FOREACH_END();
			/* pass */
		} else if (zend_string_equals_literal(name, "implode")) {
			zval *entry;

			if (Z_TYPE_P(args[0]) != IS_ARRAY) {
				return FAILURE;
			}

			ZEND_HASH_FOREACH_VAL(Z_ARRVAL_P(args[0]), entry) {
				if (Z_TYPE_P(entry) > IS_STRING) {
					return FAILURE;
				}
			} ZEND_HASH_FOREACH_END();
			/* pass */
		} else if (zend_string_equals_literal(name, "serialize")) {
			/* pass */
		} else {
			return FAILURE;
		}
	} else if (num_args == 2) {
		if (zend_string_equals_literal(name, "in_array")) {
			if (Z_TYPE_P(args[1]) != IS_ARRAY) {
				return FAILURE;
			}
			/* pass */
		} else if (zend_string_equals_literal(name, "strpos")) {
			if (Z_TYPE_P(args[0]) != IS_STRING
					|| Z_TYPE_P(args[1]) != IS_STRING
					|| !Z_STRLEN_P(args[1])
					|| (CG(compiler_options) & ZEND_COMPILE_NO_BUILTIN_STRLEN)) {
				return FAILURE;
			}
			/* pass */
		} else if (zend_string_equals_literal(name, "str_split")) {
			if (Z_TYPE_P(args[0]) != IS_STRING
					|| Z_TYPE_P(args[1]) != IS_LONG
					|| Z_LVAL_P(args[1]) <= 0) {
				return FAILURE;
			}
			/* pass */
		} else if (zend_string_equals_literal(name, "array_key_exists")) {
			if (Z_TYPE_P(args[1]) != IS_ARRAY
					|| (Z_TYPE_P(args[0]) != IS_LONG
						&& Z_TYPE_P(args[0]) != IS_STRING
						&& Z_TYPE_P(args[0]) != IS_NULL)) {
				return FAILURE;
			}
			/* pass */
		} else if (zend_string_equals_literal(name, "trim")
				|| zend_string_equals_literal(name, "rtrim")
				|| zend_string_equals_literal(name, "ltrim")
				|| zend_string_equals_literal(name, "preg_quote")) {
			if (Z_TYPE_P(args[0]) != IS_STRING
					|| Z_TYPE_P(args[1]) != IS_STRING) {
				return FAILURE;
			}
			/* pass */
		} else if (zend_string_equals_literal(name, "str_repeat")) {
			if (Z_TYPE_P(args[0]) != IS_STRING
					|| Z_TYPE_P(args[1]) != IS_LONG
					|| zend_safe_address(Z_STRLEN_P(args[0]), Z_LVAL_P(args[1]), 0, &overflow) > 64 * 1024
					|| overflow) {
				return FAILURE;
			}
			/* pass */
		} else if (zend_string_equals_literal(name, "array_merge")
				|| zend_string_equals_literal(name, "array_replace")
				|| zend_string_equals_literal(name, "array_merge_recursive")
				|| zend_string_equals_literal(name, "array_merge_recursive")
				|| zend_string_equals_literal(name, "array_diff")
				|| zend_string_equals_literal(name, "array_diff_assoc")
				|| zend_string_equals_literal(name, "array_diff_key")) {
			for (i = 0; i < num_args; i++) {
				if (Z_TYPE_P(args[i]) != IS_ARRAY) {
					return FAILURE;
				}
			}
			/* pass */
		} else if (zend_string_equals_literal(name, "implode")) {
			zval *entry;

			if ((Z_TYPE_P(args[0]) != IS_STRING || Z_TYPE_P(args[1]) != IS_ARRAY)
					&& (Z_TYPE_P(args[0]) != IS_ARRAY || Z_TYPE_P(args[1]) != IS_STRING)) {
				return FAILURE;
			}

			if (Z_TYPE_P(args[0]) == IS_ARRAY) {
				ZEND_HASH_FOREACH_VAL(Z_ARRVAL_P(args[0]), entry) {
					if (Z_TYPE_P(entry) > IS_STRING) {
						return FAILURE;
					}
				} ZEND_HASH_FOREACH_END();
			} else {
				ZEND_HASH_FOREACH_VAL(Z_ARRVAL_P(args[1]), entry) {
					if (Z_TYPE_P(entry) > IS_STRING) {
						return FAILURE;
					}
				} ZEND_HASH_FOREACH_END();
			}
			/* pass */
		} else if (zend_string_equals_literal(name, "version_compare")) {
			if (Z_TYPE_P(args[0]) != IS_STRING
					|| Z_TYPE_P(args[1]) != IS_STRING) {
				return FAILURE;
			}
			/* pass */
		} else if (zend_string_equals_literal(name, "substr")) {
			if (Z_TYPE_P(args[0]) != IS_STRING
					|| Z_TYPE_P(args[1]) != IS_LONG
					|| (CG(compiler_options) & ZEND_COMPILE_NO_BUILTIN_STRLEN)) {
				return FAILURE;
			}
			/* pass */
		} else if (zend_string_equals_literal(name, "pow")) {
			if ((Z_TYPE_P(args[0]) != IS_LONG && Z_TYPE_P(args[0]) != IS_DOUBLE)
					|| (Z_TYPE_P(args[1]) != IS_LONG && Z_TYPE_P(args[1]) != IS_DOUBLE)) {
				return FAILURE;
			}
			/* pass */
		} else {
			return FAILURE;
		}
	} else if (num_args == 3) {
		if (zend_string_equals_literal(name, "in_array")) {
			if (Z_TYPE_P(args[1]) != IS_ARRAY
				|| (Z_TYPE_P(args[2]) != IS_FALSE
					&& Z_TYPE_P(args[2]) != IS_TRUE)) {
				return FAILURE;
			}
			/* pass */
		} else if (zend_string_equals_literal(name, "array_merge")
				|| zend_string_equals_literal(name, "array_replace")
				|| zend_string_equals_literal(name, "array_merge_recursive")
				|| zend_string_equals_literal(name, "array_merge_recursive")
				|| zend_string_equals_literal(name, "array_diff")
				|| zend_string_equals_literal(name, "array_diff_assoc")
				|| zend_string_equals_literal(name, "array_diff_key")) {
			for (i = 0; i < num_args; i++) {
				if (Z_TYPE_P(args[i]) != IS_ARRAY) {
					return FAILURE;
				}
			}
			/* pass */
		} else if (zend_string_equals_literal(name, "version_compare")) {
			if (Z_TYPE_P(args[0]) != IS_STRING
					|| Z_TYPE_P(args[1]) != IS_STRING
					|| Z_TYPE_P(args[2]) != IS_STRING) {
				return FAILURE;
			}
			/* pass */
		} else if (zend_string_equals_literal(name, "substr")) {
			if (Z_TYPE_P(args[0]) != IS_STRING
					|| Z_TYPE_P(args[1]) != IS_LONG
					|| Z_TYPE_P(args[2]) != IS_LONG
					|| (CG(compiler_options) & ZEND_COMPILE_NO_BUILTIN_STRLEN)) {
				return FAILURE;
			}
			/* pass */
		} else {
			return FAILURE;
		}
	} else {
		return FAILURE;
	}

	func = zend_hash_find_ptr(CG(function_table), name);
	if (!func || func->type != ZEND_INTERNAL_FUNCTION) {
		return FAILURE;
	}

	execute_data = safe_emalloc(num_args, sizeof(zval), ZEND_CALL_FRAME_SLOT * sizeof(zval));
	memset(execute_data, 0, sizeof(zend_execute_data));
	EX(func) = func;
	EX_NUM_ARGS() = num_args;
	for (i = 0; i < num_args; i++) {
		ZVAL_COPY(EX_VAR_NUM(i), args[i]);
	}
	func->internal_function.handler(execute_data, result);
	for (i = 0; i < num_args; i++) {
		zval_ptr_dtor_nogc(EX_VAR_NUM(i));
	}
	efree(execute_data);
	return SUCCESS;
}

#define SET_RESULT(op, zv) do { \
	if (ssa_op->op##_def >= 0) { \
		set_value(scdf, ctx, ssa_op->op##_def, zv); \
	} \
} while (0)
#define SET_RESULT_BOT(op) SET_RESULT(op, &ctx->bot)
#define SET_RESULT_TOP(op) SET_RESULT(op, &ctx->top)

#define SKIP_IF_TOP(op) if (IS_TOP(op)) break;

static void sccp_visit_instr(scdf_ctx *scdf, zend_op *opline, zend_ssa_op *ssa_op) {
	sccp_ctx *ctx = (sccp_ctx *) scdf;
	zval *op1, *op2, zv; /* zv is a temporary to hold result values */

	op1 = get_op1_value(ctx, opline, ssa_op);
	op2 = get_op2_value(ctx, opline, ssa_op);

	switch (opline->opcode) {
		case ZEND_ASSIGN:
			/* The value of op1 is irrelevant here, because we are overwriting it
			 * -- unless it can be a reference, in which case we propagate a BOT. */
			if (IS_BOT(op1) && (ctx->scdf.ssa->var_info[ssa_op->op1_use].type & MAY_BE_REF)) {
				SET_RESULT_BOT(op1);
			} else {
				SET_RESULT(op1, op2);
			}

			SET_RESULT(result, op2);
			return;
		case ZEND_TYPE_CHECK:
			/* We may be able to evaluate TYPE_CHECK based on type inference info,
			 * even if we don't know the precise value. */
			if (!value_known(op1)) {
				uint32_t type = ctx->scdf.ssa->var_info[ssa_op->op1_use].type;
				uint32_t expected_type = opline->extended_value == _IS_BOOL
					? (MAY_BE_TRUE|MAY_BE_FALSE) : (1 << opline->extended_value);
				if (!(type & expected_type) && !(type & MAY_BE_UNDEF)) {
					ZVAL_FALSE(&zv);
					SET_RESULT(result, &zv);
					return;
				} else if (!(type & ((MAY_BE_ANY|MAY_BE_UNDEF) - expected_type))
						   && opline->extended_value != IS_RESOURCE) {
					ZVAL_TRUE(&zv);
					SET_RESULT(result, &zv);
					return;
				}
			}
			break;
		case ZEND_ASSIGN_DIM:
			/* If $a in $a[$b]=$c is UNDEF, treat it like NULL. There is no warning. */
			if ((ctx->scdf.ssa->var_info[ssa_op->op1_use].type & MAY_BE_ANY) == 0) {
				op1 = &EG(uninitialized_zval);
			}
			break;
		case ZEND_SEND_VAL:
		case ZEND_SEND_VAR:
		{
			/* If the value of a SEND for an ICALL changes, we need to reconsider the
			 * ICALL result value. Otherwise we can ignore the opcode. */
			zend_call_info *call;
			if (!ctx->call_map) {
				return;
			}

			call = ctx->call_map[opline - ctx->scdf.op_array->opcodes];
			if (IS_TOP(op1) || !call || call->caller_call_opline->opcode != ZEND_DO_ICALL) {
				return;
			}

			opline = call->caller_call_opline;
			ssa_op = &ctx->scdf.ssa->ops[opline - ctx->scdf.op_array->opcodes];
			break;
		}
	}

	if ((op1 && IS_BOT(op1)) || (op2 && IS_BOT(op2))) {
		/* If any operand is BOT, mark the result as BOT right away.
		 * Exceptions to this rule are handled above. */
		SET_RESULT_BOT(result);
		SET_RESULT_BOT(op1);
		SET_RESULT_BOT(op2);
		return;
	}

	switch (opline->opcode) {
		case ZEND_ADD:
		case ZEND_SUB:
		case ZEND_MUL:
		case ZEND_DIV:
		case ZEND_MOD:
		case ZEND_POW:
		case ZEND_SL:
		case ZEND_SR:
		case ZEND_CONCAT:
		case ZEND_FAST_CONCAT:
		case ZEND_IS_EQUAL:
		case ZEND_IS_NOT_EQUAL:
		case ZEND_IS_SMALLER:
		case ZEND_IS_SMALLER_OR_EQUAL:
		case ZEND_IS_IDENTICAL:
		case ZEND_IS_NOT_IDENTICAL:
		case ZEND_BW_OR:
		case ZEND_BW_AND:
		case ZEND_BW_XOR:
		case ZEND_BOOL_XOR:
		case ZEND_CASE:
			SKIP_IF_TOP(op1);
			SKIP_IF_TOP(op2);

			if (zend_optimizer_eval_binary_op(&zv, opline->opcode, op1, op2) == SUCCESS) {
				SET_RESULT(result, &zv);
				zval_ptr_dtor_nogc(&zv);
				break;
			}
			SET_RESULT_BOT(result);
			break;
		case ZEND_ASSIGN_ADD:
		case ZEND_ASSIGN_SUB:
		case ZEND_ASSIGN_MUL:
		case ZEND_ASSIGN_DIV:
		case ZEND_ASSIGN_MOD:
		case ZEND_ASSIGN_SL:
		case ZEND_ASSIGN_SR:
		case ZEND_ASSIGN_CONCAT:
		case ZEND_ASSIGN_BW_OR:
		case ZEND_ASSIGN_BW_AND:
		case ZEND_ASSIGN_BW_XOR:
		case ZEND_ASSIGN_POW:
			/* Obj/dim compound assign */
			if (opline->extended_value) {
				SET_RESULT_BOT(op1);
				SET_RESULT_BOT(result);
				break;
			}

			SKIP_IF_TOP(op1);
			SKIP_IF_TOP(op2);

			if (zend_optimizer_eval_binary_op(&zv, zend_compound_assign_to_binary_op(opline->opcode), op1, op2) == SUCCESS) {
				SET_RESULT(op1, &zv);
				SET_RESULT(result, &zv);
				zval_ptr_dtor_nogc(&zv);
				break;
			}
			SET_RESULT_BOT(op1);
			SET_RESULT_BOT(result);
			break;
		case ZEND_PRE_INC:
		case ZEND_PRE_DEC:
			SKIP_IF_TOP(op1);
			if (ct_eval_incdec(&zv, opline->opcode, op1) == SUCCESS) {
				SET_RESULT(op1, &zv);
				SET_RESULT(result, &zv);
				zval_ptr_dtor_nogc(&zv);
				break;
			}
			SET_RESULT_BOT(op1);
			SET_RESULT_BOT(result);
			break;
		case ZEND_POST_INC:
		case ZEND_POST_DEC:
			SKIP_IF_TOP(op1);
			SET_RESULT(result, op1);
			if (ct_eval_incdec(&zv, opline->opcode, op1) == SUCCESS) {
				SET_RESULT(op1, &zv);
				zval_ptr_dtor_nogc(&zv);
				break;
			}
			SET_RESULT_BOT(op1);
			break;
		case ZEND_BW_NOT:
		case ZEND_BOOL_NOT:
			SKIP_IF_TOP(op1);
			if (zend_optimizer_eval_unary_op(&zv, opline->opcode, op1) == SUCCESS) {
				SET_RESULT(result, &zv);
				zval_ptr_dtor_nogc(&zv);
				break;
			}
			SET_RESULT_BOT(result);
			break;
		case ZEND_CAST:
			SKIP_IF_TOP(op1);
			if (zend_optimizer_eval_cast(&zv, opline->extended_value, op1) == SUCCESS) {
				SET_RESULT(result, &zv);
				zval_ptr_dtor_nogc(&zv);
				break;
			}
			SET_RESULT_BOT(result);
			break;
		case ZEND_BOOL:
		case ZEND_JMPZ_EX:
		case ZEND_JMPNZ_EX:
			SKIP_IF_TOP(op1);
			ZVAL_BOOL(&zv, zend_is_true(op1));
			SET_RESULT(result, &zv);
			break;
		case ZEND_STRLEN:
			SKIP_IF_TOP(op1);
			if (zend_optimizer_eval_strlen(&zv, op1) == SUCCESS) {
				SET_RESULT(result, &zv);
				zval_ptr_dtor_nogc(&zv);
				break;
			}
			SET_RESULT_BOT(result);
			break;
		case ZEND_COUNT:
			SKIP_IF_TOP(op1);
			if (Z_TYPE_P(op1) == IS_ARRAY) {
				ZVAL_LONG(&zv, zend_hash_num_elements(Z_ARRVAL_P(op1)));
				SET_RESULT(result, &zv);
				zval_ptr_dtor_nogc(&zv);
				break;
			}
			SET_RESULT_BOT(result);
			break;
		case ZEND_IN_ARRAY:
			SKIP_IF_TOP(op1);
			SKIP_IF_TOP(op2);
			if (ct_eval_in_array(&zv, opline->extended_value, op1, op2) == SUCCESS) {
				SET_RESULT(result, &zv);
				zval_ptr_dtor_nogc(&zv);
				break;
			}
			SET_RESULT_BOT(result);
			break;
		case ZEND_FETCH_DIM_R:
		case ZEND_FETCH_DIM_IS:
		case ZEND_FETCH_LIST:
			SKIP_IF_TOP(op1);
			SKIP_IF_TOP(op2);

			if (ct_eval_fetch_dim(&zv, op1, op2, (opline->opcode != ZEND_FETCH_LIST)) == SUCCESS) {
				SET_RESULT(result, &zv);
				zval_ptr_dtor_nogc(&zv);
				break;
			}
			SET_RESULT_BOT(result);
			break;
		case ZEND_ISSET_ISEMPTY_DIM_OBJ:
			SKIP_IF_TOP(op1);
			SKIP_IF_TOP(op2);

			if (ct_eval_isset_dim(&zv, opline->extended_value, op1, op2) == SUCCESS) {
				SET_RESULT(result, &zv);
				zval_ptr_dtor_nogc(&zv);
				break;
			}
			SET_RESULT_BOT(result);
			break;
		case ZEND_QM_ASSIGN:
		case ZEND_JMP_SET:
		case ZEND_COALESCE:
			SET_RESULT(result, op1);
			break;
		case ZEND_FETCH_CLASS:
			if (!op1) {
				SET_RESULT_BOT(result);
				break;
			}
			SET_RESULT(result, op1);
			break;
		case ZEND_ISSET_ISEMPTY_CV:
			SKIP_IF_TOP(op1);
			if (ct_eval_isset_isempty(&zv, opline->extended_value, op1) == SUCCESS) {
				SET_RESULT(result, &zv);
				zval_ptr_dtor_nogc(&zv);
				break;
			}
			SET_RESULT_BOT(result);
			break;
		case ZEND_TYPE_CHECK:
			SKIP_IF_TOP(op1);
			ct_eval_type_check(&zv, opline->extended_value, op1);
			SET_RESULT(result, &zv);
			zval_ptr_dtor_nogc(&zv);
			break;
		case ZEND_INSTANCEOF:
			SKIP_IF_TOP(op1);
			ZVAL_FALSE(&zv);
			SET_RESULT(result, &zv);
			break;
		case ZEND_ROPE_INIT:
			SKIP_IF_TOP(op2);
			if (zend_optimizer_eval_cast(&zv, IS_STRING, op2) == SUCCESS) {
				SET_RESULT(result, &zv);
				zval_ptr_dtor_nogc(&zv);
				break;
			}
			SET_RESULT_BOT(result);
			break;
		case ZEND_ROPE_ADD:
		case ZEND_ROPE_END:
			// TODO The way this is currently implemented will result in quadratic runtime
			// This is not necessary, the way the algorithm works it's okay to reuse the same
			// string for all SSA vars with some extra checks
			SKIP_IF_TOP(op1);
			SKIP_IF_TOP(op2);
			if (zend_optimizer_eval_binary_op(&zv, ZEND_CONCAT, op1, op2) == SUCCESS) {
				SET_RESULT(result, &zv);
				zval_ptr_dtor_nogc(&zv);
				break;
			}
			SET_RESULT_BOT(result);
			break;
		case ZEND_INIT_ARRAY:
		case ZEND_ADD_ARRAY_ELEMENT:
		{
			zval *result = NULL;
			if (opline->extended_value & ZEND_ARRAY_ELEMENT_REF) {
				SET_RESULT_BOT(result);
				SET_RESULT_BOT(op1);
				break;
			}

			if (opline->opcode == ZEND_ADD_ARRAY_ELEMENT) {
				result = &ctx->values[ssa_op->result_use];
				if (IS_BOT(result)) {
					SET_RESULT_BOT(result);
					break;
				}
				SKIP_IF_TOP(result);
			}

			SKIP_IF_TOP(op1);
			if (op2) {
				SKIP_IF_TOP(op2);
			}

			/* We want to avoid keeping around intermediate arrays for each SSA variable in the
			 * ADD_ARRAY_ELEMENT chain. We do this by only keeping the array on the last opcode
			 * and use a NULL value everywhere else. */
			if (Z_TYPE(ctx->values[ssa_op->result_def]) == IS_NULL) {
				break;
			}

			if (result) {
				ZVAL_COPY_VALUE(&zv, result);
				ZVAL_NULL(result);
			} else {
				array_init(&zv);
			}

			if (ct_eval_add_array_elem(&zv, op1, op2) == SUCCESS) {
				SET_RESULT(result, &zv);
				zval_ptr_dtor_nogc(&zv);
				break;
			}
			SET_RESULT_BOT(result);
			zval_ptr_dtor_nogc(&zv);
			break;
		}
		case ZEND_ASSIGN_DIM:
		{
			zval *data = get_op1_value(ctx, opline+1, ssa_op+1);
			if (IS_BOT(data)) {
				SET_RESULT_BOT(op1);
				SET_RESULT_BOT(result);
				break;
			}

			SKIP_IF_TOP(data);
			SKIP_IF_TOP(op1);
			if (op2) {
				SKIP_IF_TOP(op2);
			}

			ZVAL_DUP(&zv, op1);
			if (ct_eval_assign_dim(&zv, data, op2) == SUCCESS) {
				SET_RESULT(result, data);
				SET_RESULT(op1, &zv);
				zval_ptr_dtor_nogc(&zv);
				break;
			}
			SET_RESULT_BOT(result);
			SET_RESULT_BOT(op1);
			zval_ptr_dtor_nogc(&zv);
			break;
		}
		case ZEND_DO_ICALL:
		{
			zend_call_info *call;
			zval *name, *args[3] = {NULL};
			int i;

			if (!ctx->call_map) {
				SET_RESULT_BOT(result);
				break;
			}

			call = ctx->call_map[opline - ctx->scdf.op_array->opcodes];
			name = CT_CONSTANT_EX(ctx->scdf.op_array, call->caller_init_opline->op2.constant);

			/* We already know it can't be evaluated, don't bother checking again */
			if (ssa_op->result_def < 0 || IS_BOT(&ctx->values[ssa_op->result_def])) {
				break;
			}

			/* We're only interested in functions with up to three arguments right now */
			if (call->num_args > 3) {
				SET_RESULT_BOT(result);
				break;
			}

			for (i = 0; i < call->num_args; i++) {
				zend_op *opline = call->arg_info[i].opline;
				if (opline->opcode != ZEND_SEND_VAL && opline->opcode != ZEND_SEND_VAR) {
					SET_RESULT_BOT(result);
					return;
				}

				args[i] = get_op1_value(ctx, opline,
					&ctx->scdf.ssa->ops[opline - ctx->scdf.op_array->opcodes]);
				if (args[i]) {
					if (IS_BOT(args[i])) {
						SET_RESULT_BOT(result);
						return;
					} else if (IS_TOP(args[i])) {
						return;
					}
				}
			}

			/* We didn't get a BOT argument, so value stays the same */
			if (!IS_TOP(&ctx->values[ssa_op->result_def])) {
				break;
			}

			if (ct_eval_func_call(&zv, Z_STR_P(name), call->num_args, args) == SUCCESS) {
				SET_RESULT(result, &zv);
				zval_ptr_dtor_nogc(&zv);
				break;
			}

#if 0
			/* sort out | uniq -c | sort -n */
			fprintf(stderr, "%s\n", Z_STRVAL_P(name));
			/*if (args[1]) {
				php_printf("%s %Z %Z\n", Z_STRVAL_P(name), args[0], args[1]);
			} else {
				php_printf("%s %Z\n", Z_STRVAL_P(name), args[0]);
			}*/
#endif

			SET_RESULT_BOT(result);
			break;
		}
		default:
		{
			/* If we have no explicit implementation return BOT */
			SET_RESULT_BOT(result);
			SET_RESULT_BOT(op1);
			SET_RESULT_BOT(op2);
			break;
		}
	}
}

/* Returns whether there is a successor */
static void sccp_mark_feasible_successors(
		scdf_ctx *scdf,
		int block_num, zend_basic_block *block,
		zend_op *opline, zend_ssa_op *ssa_op) {
	sccp_ctx *ctx = (sccp_ctx *) scdf;
	zval *op1;
	int s;

	/* We can't determine the branch target at compile-time for these */
	switch (opline->opcode) {
		case ZEND_ASSERT_CHECK:
		case ZEND_CATCH:
		case ZEND_DECLARE_ANON_CLASS:
		case ZEND_DECLARE_ANON_INHERITED_CLASS:
		case ZEND_FE_FETCH_R:
		case ZEND_FE_FETCH_RW:
			scdf_mark_edge_feasible(scdf, block_num, block->successors[0]);
			scdf_mark_edge_feasible(scdf, block_num, block->successors[1]);
			return;
	}

	op1 = get_op1_value(ctx, opline, ssa_op);

	/* Branch target can be either one */
	if (!op1 || IS_BOT(op1)) {
		for (s = 0; s < block->successors_count; s++) {
			scdf_mark_edge_feasible(scdf, block_num, block->successors[s]);
		}
		return;
	}

	/* Branch target not yet known */
	if (IS_TOP(op1)) {
		return;
	}

	switch (opline->opcode) {
		case ZEND_JMPZ:
		case ZEND_JMPZNZ:
		case ZEND_JMPZ_EX:
			s = zend_is_true(op1);
			break;
		case ZEND_JMPNZ:
		case ZEND_JMPNZ_EX:
		case ZEND_JMP_SET:
			s = !zend_is_true(op1);
			break;
		case ZEND_COALESCE:
			s = (Z_TYPE_P(op1) == IS_NULL);
			break;
		case ZEND_FE_RESET_R:
		case ZEND_FE_RESET_RW:
			if (Z_TYPE_P(op1) != IS_ARRAY) {
				scdf_mark_edge_feasible(scdf, block_num, block->successors[0]);
				scdf_mark_edge_feasible(scdf, block_num, block->successors[1]);
				return;
			}
			s = zend_hash_num_elements(Z_ARR_P(op1)) != 0;
			break;
		default:
			for (s = 0; s < block->successors_count; s++) {
				scdf_mark_edge_feasible(scdf, block_num, block->successors[s]);
			}
			return;
	}
	scdf_mark_edge_feasible(scdf, block_num, block->successors[s]);
}

static void join_phi_values(zval *a, zval *b) {
	if (IS_BOT(a) || IS_TOP(b)) {
		return;
	}
	if (IS_TOP(a)) {
		zval_ptr_dtor_nogc(a);
		ZVAL_COPY(a, b);
		return;
	}
	if (IS_BOT(b) || !zend_is_identical(a, b)) {
		zval_ptr_dtor_nogc(a);
		MAKE_BOT(a);
	}
}

static void sccp_visit_phi(scdf_ctx *scdf, zend_ssa_phi *phi) {
	sccp_ctx *ctx = (sccp_ctx *) scdf;
	zend_ssa *ssa = scdf->ssa;
	ZEND_ASSERT(phi->ssa_var >= 0);
	if (!IS_BOT(&ctx->values[phi->ssa_var])) {
		zend_basic_block *block = &ssa->cfg.blocks[phi->block];
		int *predecessors = &ssa->cfg.predecessors[block->predecessor_offset];

		int i;
		zval result;
		MAKE_TOP(&result);
		SCP_DEBUG("Handling PHI(");
		if (phi->pi >= 0) {
			ZEND_ASSERT(phi->sources[0] >= 0);
			if (scdf_is_edge_feasible(scdf, phi->pi, phi->block)) {
				join_phi_values(&result, &ctx->values[phi->sources[0]]);
			}
		} else {
			for (i = 0; i < block->predecessors_count; i++) {
				ZEND_ASSERT(phi->sources[i] >= 0);
				if (scdf_is_edge_feasible(scdf, predecessors[i], phi->block)) {
					SCP_DEBUG("val, ");
					join_phi_values(&result, &ctx->values[phi->sources[i]]);
				} else {
					SCP_DEBUG("--, ");
				}
			}
		}
		SCP_DEBUG(")\n");

		set_value(scdf, ctx, phi->ssa_var, &result);
		zval_ptr_dtor_nogc(&result);
	}
}

static zval *value_from_type_and_range(sccp_ctx *ctx, int var_num, zval *tmp) {
	zend_ssa *ssa = ctx->scdf.ssa;
	zend_ssa_var_info *info = &ssa->var_info[var_num];

	if (ssa->vars[var_num].var >= ctx->scdf.op_array->last_var) {
		// TODO Non-CVs may cause issues with FREEs
		return NULL;
	}

	if (info->type & MAY_BE_UNDEF) {
		return NULL;
	}

	if (!(info->type & ((MAY_BE_ANY|MAY_BE_UNDEF)-MAY_BE_NULL))) {
		ZVAL_NULL(tmp);
		return tmp;
	}
	if (!(info->type & ((MAY_BE_ANY|MAY_BE_UNDEF)-MAY_BE_FALSE))) {
		ZVAL_FALSE(tmp);
		return tmp;
	}
	if (!(info->type & ((MAY_BE_ANY|MAY_BE_UNDEF)-MAY_BE_TRUE))) {
		ZVAL_TRUE(tmp);
		return tmp;
	}

	if (!(info->type & ((MAY_BE_ANY|MAY_BE_UNDEF)-MAY_BE_LONG))
			&& info->has_range
			&& !info->range.overflow && !info->range.underflow
			&& info->range.min == info->range.max) {
		ZVAL_LONG(tmp, info->range.min);
		return tmp;
	}

	return NULL;
}

/* This will try to replace uses of SSA variables we have determined to be constant. Not all uses
 * can be replaced, because some instructions don't accept constant operands or only accept them
 * if they have a certain type. */
static int replace_constant_operands(sccp_ctx *ctx) {
	zend_ssa *ssa = ctx->scdf.ssa;
	zend_op_array *op_array = ctx->scdf.op_array;
	int i;
	zval tmp;
	int removed_ops = 0;

	/* We iterate the variables backwards, so we can eliminate sequences like INIT_ROPE
	 * and INIT_ARRAY. */
	for (i = ssa->vars_count - 1; i >= op_array->last_var; i--) {
		zend_ssa_var *var = &ssa->vars[i];
		zval *value;
		int use;

		if (value_known(&ctx->values[i])) {
			value = &ctx->values[i];
		} else {
			value = value_from_type_and_range(ctx, i, &tmp);
			if (!value) {
				continue;
			}
		}

		FOREACH_USE(var, use) {
			zend_op *opline = &op_array->opcodes[use];
			zend_ssa_op *ssa_op = &ssa->ops[use];
			if (try_replace_op1(ctx, opline, ssa_op, i, value)) {
				if (opline->opcode == ZEND_NOP) {
					removed_ops++;
				}
				ZEND_ASSERT(ssa_op->op1_def == -1);
				if (ssa_op->op1_use != ssa_op->op2_use) {
					zend_ssa_unlink_use_chain(ssa, use, 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 (try_replace_op2(ctx, opline, ssa_op, i, value)) {
				ZEND_ASSERT(ssa_op->op2_def == -1);
				if (ssa_op->op2_use != ssa_op->op1_use) {
					zend_ssa_unlink_use_chain(ssa, use, ssa_op->op2_use);
				}
				ssa_op->op2_use = -1;
				ssa_op->op2_use_chain = -1;
			}
		} FOREACH_USE_END();

		/* This is a basic DCE pass we run after SCCP. It only works on those instructions those result
		 * value(s) were determined by SCCP. It removes dead computational instructions and converts
		 * CV-affecting instructions into CONST ASSIGNs. This basic DCE is performed for multiple reasons:
		 * a) During operand replacement we eliminate FREEs. The corresponding computational instructions
		 *    must be removed to avoid leaks. This way SCCP can run independently of the full DCE pass.
		 * b) The main DCE pass relies on type analysis to determine whether instructions have side-effects
		 *    and can't be DCEd. This means that it will not be able collect all instructions rendered dead
		 *    by SCCP, because they may have potentially side-effecting types, but the actual values are
		 *    not. As such doing DCE here will allow us to eliminate more dead code in combination.
		 * c) The ordinary DCE pass cannot collect dead calls. However SCCP can result in dead calls, which
		 *    we need to collect. */

		if (var->definition >= 0 && value_known(&ctx->values[i])) {
			zend_op *opline = &op_array->opcodes[var->definition];
			zend_ssa_op *ssa_op = &ssa->ops[var->definition];
			if (opline->opcode == ZEND_ASSIGN) {
				/* Leave assigns to DCE (due to dtor effects) */
				continue;
			}

			if (ssa_op->result_def == i
					&& ssa_op->op1_def < 0
					&& ssa_op->op2_def < 0
					&& var->use_chain < 0
					&& var->phi_use_chain == NULL) {
				if (opline->opcode == ZEND_DO_ICALL) {
					/* Call instruction -> remove opcodes that are part of the call */
					zend_call_info *call;
					int i;

					ZEND_ASSERT(ctx->call_map);
					call = ctx->call_map[var->definition];
					ZEND_ASSERT(call);
					ZEND_ASSERT(call->caller_call_opline == opline);
					if (opline->result_type & (IS_TMP_VAR|IS_VAR)) {
						zend_optimizer_remove_live_range_ex(op_array, opline->result.var, var->definition);
					}
					zend_ssa_remove_result_def(ssa, ssa_op);
					zend_ssa_remove_instr(ssa, opline, ssa_op);
					zend_ssa_remove_instr(ssa, call->caller_init_opline,
						&ssa->ops[call->caller_init_opline - op_array->opcodes]);

					for (i = 0; i < call->num_args; i++) {
						zend_ssa_remove_instr(ssa, call->arg_info[i].opline,
							&ssa->ops[call->arg_info[i].opline - op_array->opcodes]);
					}
					removed_ops = call->num_args + 2;

					// TODO: remove call_info completely???
					call->callee_func = NULL;
				} else {
					/* Ordinary computational instruction -> remove it */
					if (opline->result_type & (IS_TMP_VAR|IS_VAR)) {
						zend_optimizer_remove_live_range_ex(op_array, opline->result.var, var->definition);
					}
					zend_ssa_remove_result_def(ssa, ssa_op);
					zend_ssa_remove_instr(ssa, opline, ssa_op);
					removed_ops++;
				}
			} else if (ssa_op->op1_def == i) {
				/* Compound assign or incdec -> convert to direct ASSIGN */

				/* Destroy previous op2 */
				if (opline->op2_type == IS_CONST) {
					literal_dtor(&ZEND_OP2_LITERAL(opline));
				} else if (ssa_op->op2_use >= 0) {
					if (ssa_op->op2_use != ssa_op->op1_use) {
						zend_ssa_unlink_use_chain(ssa, var->definition, ssa_op->op2_use);
					}
					ssa_op->op2_use = -1;
					ssa_op->op2_use_chain = -1;
				}

				/* Mark result unused, if possible */
				if (ssa_op->result_def >= 0
						&& ssa->vars[ssa_op->result_def].use_chain < 0
						&& ssa->vars[ssa_op->result_def].phi_use_chain == NULL) {
					if (opline->result_type & (IS_TMP_VAR|IS_VAR)) {
						zend_optimizer_remove_live_range_ex(op_array, opline->result.var, var->definition);
					}
					zend_ssa_remove_result_def(ssa, ssa_op);
					opline->result_type = IS_UNUSED;
				}

				/* Remove OP_DATA opcode */
				if (opline->opcode == ZEND_ASSIGN_DIM) {
					removed_ops++;
					zend_ssa_remove_instr(ssa, opline + 1, ssa_op + 1);
				}

				/* Convert to ASSIGN */
				opline->opcode = ZEND_ASSIGN;
				opline->op2_type = IS_CONST;
				opline->op2.constant = zend_optimizer_add_literal(op_array, value);
				Z_TRY_ADDREF_P(value);
			}
		}
		if (var->definition_phi
				&& value_known(&ctx->values[i])
				&& var->use_chain < 0
				&& var->phi_use_chain == NULL) {
			zend_ssa_remove_phi(ssa, var->definition_phi);
		}
	}

	return removed_ops;
}

static void sccp_context_init(zend_optimizer_ctx *ctx, sccp_ctx *sccp,
		zend_ssa *ssa, zend_op_array *op_array, zend_call_info **call_map) {
	int i;
	sccp->call_map = call_map;
	sccp->values = zend_arena_alloc(&ctx->arena, sizeof(zval) * ssa->vars_count);

	MAKE_TOP(&sccp->top);
	MAKE_BOT(&sccp->bot);

	i = 0;
	for (; i < op_array->last_var; ++i) {
		/* These are all undefined variables, which we have to mark BOT.
		 * Otherwise the undefined variable warning might not be preserved. */
		MAKE_BOT(&sccp->values[i]);
	}
	for (; i < ssa->vars_count; ++i) {
		if (ssa->vars[i].alias) {
			MAKE_BOT(&sccp->values[i]);
		} else {
			MAKE_TOP(&sccp->values[i]);
		}
	}
}

static void sccp_context_free(sccp_ctx *sccp) {
	int i;
	for (i = sccp->scdf.op_array->last_var; i < sccp->scdf.ssa->vars_count; ++i) {
		zval_ptr_dtor_nogc(&sccp->values[i]);
	}
}

int sccp_optimize_op_array(zend_optimizer_ctx *ctx, zend_op_array *op_array, zend_ssa *ssa, zend_call_info **call_map)
{
	sccp_ctx sccp;
	int removed_ops = 0;
	void *checkpoint = zend_arena_checkpoint(ctx->arena);

	sccp_context_init(ctx, &sccp, ssa, op_array, call_map);

	sccp.scdf.handlers.visit_instr = sccp_visit_instr;
	sccp.scdf.handlers.visit_phi = sccp_visit_phi;
	sccp.scdf.handlers.mark_feasible_successors = sccp_mark_feasible_successors;

	scdf_init(ctx, &sccp.scdf, op_array, ssa);
	scdf_solve(&sccp.scdf, "SCCP");

	removed_ops += scdf_remove_unreachable_blocks(&sccp.scdf);
	removed_ops += replace_constant_operands(&sccp);

	sccp_context_free(&sccp);
	zend_arena_release(&ctx->arena, checkpoint);

	return removed_ops;
}
