From 7a8bafb92b5504977afbc6abfd2b3606315e52c3 Mon Sep 17 00:00:00 2001
From: ndossche <7771979+ndossche@users.noreply.github.com>
Date: Fri, 2 Oct 2026 21:09:32 +0200
Subject: [PATCH] JIT: Optimize array checks in comparisons

There are two optimizations:
1. This patch implements the JIT counterpart of the VM change 2d6b8694 to
   optimize comparisons against empty arrays.
2. This patch ensures that if a type can be array, the element count
   check happens inline rather than going to a slow path.

PHP demo code for #1:
```php
function f(array $a) {
	if ($a) return 0;
	return 1;
}
```

Before #1 (for func JIT in this case):
```asm
.L1:
	movq $0x418d88c0, (%r14)        ; EX(opline) = opline
	leaq 0x50(%r14), %rdi           ; arg = &CV0($a)
	movabsq $zend_is_true, %rax
	callq *%rax
	testb %al, %al
	je .L2
```

After #1:
```asm
.L1:
	movq 0x50(%r14), %rax           ; Z_ARRVAL($a)
	cmpl $0, 0x1c(%rax)             ; compare nNumOfElements
	je .L2
```

PHP demo code for #2:
```php
function is_empty(array $a) {
	if ($a === []) return 1;
	return 2;
}
```

Before #2:
```asm
.L1:
	leaq 0x50(%r14), %rdi           ; arg1 = &CV0($a)
	movl $0x418d8ad8, %esi          ; arg2 = &literal []
	movabsq $zend_is_identical, %rax
	callq *%rax
	testb %al, %al
	je .L2
```

After #2:
```asm
.L1:
	movq 0x50(%r14), %rax           ; Z_ARRVAL($a)
	cmpl $0, 0x1c(%rax)             ; compare nNumOfElements
	jne .L2
```

It ain't much, but it should help.
I think many small frontend improvements can make a nice change in
total together.
---
 ext/opcache/jit/zend_jit_ir.c | 31 +++++++++++++++++++++++++++++--
 1 file changed, 29 insertions(+), 2 deletions(-)

diff --git a/ext/opcache/jit/zend_jit_ir.c b/ext/opcache/jit/zend_jit_ir.c
index c6d4927d41bd..2d0e6356ab04 100644
--- a/ext/opcache/jit/zend_jit_ir.c
+++ b/ext/opcache/jit/zend_jit_ir.c
@@ -7263,6 +7263,13 @@ static int zend_jit_cmp(zend_jit_ctx   *jit,
 	return 1;
 }
 
+static bool zend_jit_is_const_empty_array(zend_jit_addr addr)
+{
+	return Z_MODE(addr) == IS_CONST_ZVAL
+		&& Z_TYPE_P(Z_ZV(addr)) == IS_ARRAY
+		&& zend_hash_num_elements(Z_ARRVAL_P(Z_ZV(addr))) == 0;
+}
+
 static int zend_jit_identical(zend_jit_ctx   *jit,
                               const zend_op  *opline,
                               uint32_t        op1_info,
@@ -7424,6 +7431,14 @@ static int zend_jit_identical(zend_jit_ctx   *jit,
 			zval *val = Z_ZV(op2_addr);
 
 			ref = ir_EQ(jit_Z_TYPE(jit, op1_addr), ir_CONST_U8(Z_TYPE_P(val)));
+		} else if (zend_jit_is_const_empty_array(op1_addr) && (op2_info & (MAY_BE_ANY|MAY_BE_UNDEF)) == MAY_BE_ARRAY) {
+			// JIT: zend_hash_num_elements(Z_ARRVAL_P(op2)) == 0
+			ref = ir_EQ(ir_LOAD_U32(ir_ADD_OFFSET(jit_Z_PTR(jit, op2_addr), offsetof(HashTable, nNumOfElements))),
+				ir_CONST_U32(0));
+		} else if (zend_jit_is_const_empty_array(op2_addr) && (op1_info & (MAY_BE_ANY|MAY_BE_UNDEF)) == MAY_BE_ARRAY) {
+			// JIT: zend_hash_num_elements(Z_ARRVAL_P(op1)) == 0
+			ref = ir_EQ(ir_LOAD_U32(ir_ADD_OFFSET(jit_Z_PTR(jit, op1_addr), offsetof(HashTable, nNumOfElements))),
+				ir_CONST_U32(0));
 		} else {
 			if (Z_MODE(op1_addr) == IS_REG) {
 				zend_jit_addr real_addr = ZEND_ADDR_MEM_ZVAL(ZREG_FP, opline->op1.var);
@@ -7762,8 +7777,20 @@ static int zend_jit_bool_jmpznz(zend_jit_ctx *jit, const zend_op *opline, uint32
 	}
 
 	if (op1_info & (MAY_BE_ANY - (MAY_BE_NULL|MAY_BE_FALSE|MAY_BE_TRUE|MAY_BE_LONG|MAY_BE_DOUBLE))) {
-		jit_SET_EX_OPLINE(jit, opline);
-		ref = ir_CALL_1(IR_BOOL, ir_CONST_FC_FUNC(zend_is_true), jit_ZVAL_ADDR(jit, op1_addr));
+		if ((op1_info & (MAY_BE_ANY - (MAY_BE_NULL|MAY_BE_FALSE|MAY_BE_TRUE|MAY_BE_LONG|MAY_BE_DOUBLE))) == MAY_BE_ARRAY) {
+			/* CV deref handled above. These opcodes only take CONST|TMP|CV operands, and TMPs never hold references. */
+			ZEND_ASSERT(opline->op1_type == IS_CV || !(op1_info & MAY_BE_REF));
+			// JIT: zend_hash_num_elements(Z_ARRVAL_P(op1)) != 0
+			ref = ir_NE(ir_LOAD_U32(ir_ADD_OFFSET(jit_Z_PTR(jit, op1_addr), offsetof(HashTable, nNumOfElements))),
+				ir_CONST_U32(0));
+			if (opline->op1_type == IS_CV) {
+				/* The check above can't throw, and a CV isn't freed. */
+				may_throw = 0;
+			}
+		} else {
+			jit_SET_EX_OPLINE(jit, opline);
+			ref = ir_CALL_1(IR_BOOL, ir_CONST_FC_FUNC(zend_is_true), jit_ZVAL_ADDR(jit, op1_addr));
+		}
 		jit_FREE_OP(jit, opline->op1_type, opline->op1, op1_info, NULL);
 		if (may_throw) {
 			zend_jit_check_exception_undef_result(jit, opline);