Convert ZEND_ECHO operand to string during sccp

And filter out echoes of the empty string (e.g. false/null)

Split out of php#5097

Author: TysonAndre

ext/opcache/Optimizer/sccp.c

@@ -1829,6 +1829,41 @@ static void sccp_visit_instr(scdf_ctx *scdf, zend_op *opline, zend_ssa_op *ssa_o
 			}
 			SET_RESULT_BOT(result);
 			break;
+		case ZEND_ECHO:
+			// fprintf(stderr, "optimizing ZEND_ECHO type=%d\n", Z_TYPE_P(op1));
+			SKIP_IF_TOP(op1);
+			if (IS_PARTIAL_ARRAY(op1)) {
+				break;
+			}
+			if (Z_TYPE_P(op1) == IS_STRING) {
+				/* already a string */
+			} else if (zend_optimizer_eval_cast(&zv, IS_STRING, op1) == SUCCESS) {
+				opline->op1_type = IS_CONST;
+				opline->op1.constant = zend_optimizer_add_literal(ctx->scdf.op_array, &zv);
+				op1 = get_op1_value(ctx, opline, ssa_op);
+				if (ssa_op->op1_use >= 0) {
+					ZEND_ASSERT(ssa_op->op1_def == -1);
+					zend_ssa_unlink_use_chain(ctx->scdf.ssa, ssa_op - ctx->scdf.ssa->ops, ssa_op->op1_use);
+					ssa_op->op1_use = -1;
+					ssa_op->op1_use_chain = -1;
+				}
+			} else {
+				break;
+			}
+			if (Z_STRLEN_P(op1) == 0) {
+				if (ssa_op->op1_use >= 0) {
+					ZEND_ASSERT(ssa_op->op1_def == -1);
+					zend_ssa_unlink_use_chain(ctx->scdf.ssa, ssa_op - ctx->scdf.ssa->ops, ssa_op->op1_use);
+					ssa_op->op1_use = -1;
+					ssa_op->op1_use_chain = -1;
+				}
+				MAKE_NOP(opline);
+				break;
+			}
+			/* TODO: In a subsequent pass, *after* inferring values and compacting nops, combine consecutive ZEND_ECHOs using the block information from ssa->cfg */
+			/* (e.g. for ext/opcache/tests/opt/sccp_010.phpt) */
+			/* https://github.com/php/php-src/pull/5097#issuecomment-577306560 */
+			break;
 		case ZEND_DO_ICALL:
 		{
 			zend_call_info *call;

ext/opcache/tests/opt/sccp_002.phpt

@@ -32,6 +32,6 @@ foo: ; (lines=4, args=1, vars=1, tmps=0)
     ; (after optimizer)
     ; %ssccp_002.php:2-12
 L0 (2):     CV0($x) = RECV 1
-L1 (9):     ECHO int(1)
-L2 (11):    ECHO int(1)
+L1 (9):     ECHO string("1")
+L2 (11):    ECHO string("1")
 L3 (12):    RETURN null

ext/opcache/tests/opt/sccp_003.phpt

@@ -31,6 +31,6 @@ L0 (14):    RETURN int(1)
 foo: ; (lines=3, args=0, vars=0, tmps=0)
     ; (after optimizer)
     ; %ssccp_003.php:2-12
-L0 (9):     ECHO int(1)
-L1 (11):    ECHO int(1)
+L0 (9):     ECHO string("1")
+L1 (11):    ECHO string("1")
 L2 (12):    RETURN null

ext/opcache/tests/opt/sccp_004.phpt

@@ -35,6 +35,6 @@ foo: ; (lines=4, args=1, vars=1, tmps=0)
     ; (after optimizer)
     ; %ssccp_004.php:2-15
 L0 (2):     CV0($x) = RECV 1
-L1 (11):    ECHO bool(true)
-L2 (14):    ECHO int(1)
+L1 (11):    ECHO string("1")
+L2 (14):    ECHO string("1")
 L3 (15):    RETURN null

ext/opcache/tests/opt/sccp_005.phpt

@@ -25,5 +25,5 @@ foo: ; (lines=3, args=1, vars=1, tmps=0)
     ; (after optimizer)
     ; %ssccp_005.php:2-5
 L0 (2):     CV0($x) = RECV 1
-L1 (4):     ECHO int(2)
+L1 (4):     ECHO string("2")
 L2 (5):     RETURN null

ext/opcache/tests/opt/sccp_007.phpt

@@ -29,5 +29,5 @@ foo: ; (lines=3, args=1, vars=1, tmps=0)
     ; (after optimizer)
     ; %ssccp_007.php:2-9
 L0 (2):     CV0($x) = RECV 1
-L1 (8):     ECHO int(0)
+L1 (8):     ECHO string("0")
 L2 (9):     RETURN null

ext/opcache/tests/opt/sccp_009.phpt

@@ -26,5 +26,5 @@ foo: ; (lines=3, args=1, vars=1, tmps=0)
     ; (after optimizer)
     ; %ssccp_009.php:2-6
 L0 (2):     CV0($x) = RECV 1
-L1 (5):     ECHO int(2)
+L1 (5):     ECHO string("2")
 L2 (6):     RETURN null

ext/opcache/tests/opt/sccp_010.phpt

@@ -32,6 +32,6 @@ L0 (15):    RETURN int(1)
 foo: ; (lines=3, args=0, vars=0, tmps=0)
     ; (after optimizer)
     ; %ssccp_010.php:2-13
-L0 (10):    ECHO int(1)
-L1 (12):    ECHO int(1)
+L0 (10):    ECHO string("1")
+L1 (12):    ECHO string("1")
 L2 (13):    RETURN null

ext/opcache/tests/opt/sccp_011.phpt

@@ -32,5 +32,5 @@ foo: ; (lines=3, args=1, vars=1, tmps=0)
     ; (after optimizer)
     ; %ssccp_011.php:2-12
 L0 (2):     CV0($x) = RECV 1
-L1 (11):    ECHO int(0)
+L1 (11):    ECHO string("0")
 L2 (12):    RETURN null

ext/opcache/tests/opt/sccp_012.phpt

@@ -34,6 +34,6 @@ L0 (17):    RETURN int(1)
 foo: ; (lines=3, args=0, vars=0, tmps=0)
     ; (after optimizer)
     ; %ssccp_012.php:2-15
-L0 (10):    ECHO int(1)
-L1 (14):    ECHO int(4)
+L0 (10):    ECHO string("1")
+L1 (14):    ECHO string("4")
 L2 (15):    RETURN null

ext/opcache/tests/opt/sccp_022.phpt

@@ -32,7 +32,7 @@ L1 (3):     ASSIGN_DIM CV1($a) int(0)
 L2 (3):     OP_DATA CV0($x)
 L3 (4):     ASSIGN_DIM CV1($a) int(1)
 L4 (4):     OP_DATA int(5)
-L5 (5):     ECHO int(5)
+L5 (5):     ECHO string("5")
 L6 (6):     ASSIGN_OBJ CV1($a) string("foo")
 L7 (6):     OP_DATA int(5)
 L8 (7):     T2 = FETCH_DIM_R CV1($a) int(1)

ext/opcache/tests/opt/sccp_031.phpt

@@ -0,0 +1,36 @@
+--TEST--
+SCCP 031: Echo optimizations
+--INI--
+opcache.enable=1
+opcache.enable_cli=1
+opcache.optimization_level=-1
+opcache.opt_debug_level=0x20000
+opcache.preload=
+--SKIPIF--
+<?php require_once('skipif.inc'); ?>
+--FILE--
+<?php
+function foo() {
+	$k = 0;
+	$a = [null];
+	echo isset($a[$k]);
+	echo "b";
+	echo isset($a[$k+1]);
+	echo "c";
+	echo $a[$k];
+	echo $a; // Should not be optimized
+}
+?>
+--EXPECTF--
+$_main: ; (lines=1, args=0, vars=0, tmps=0)
+    ; (after optimizer)
+    ; %ssccp_031.php:1-13
+L0 (13):    RETURN int(1)
+
+foo: ; (lines=4, args=0, vars=0, tmps=0)
+    ; (after optimizer)
+    ; %s_031.php:2-11
+L0 (6):     ECHO string("b")
+L1 (8):     ECHO string("c")
+L2 (10):    ECHO array(...)
+L3 (11):    RETURN null