LibJS/JIT: Add fast path for Int32 & Int32

Userland/Libraries/LibJS/JIT/Compiler.cpp

@@ -626,6 +626,35 @@ void Compiler::compile_less_than(Bytecode::Op::LessThan const& op)
     end.link(m_assembler);
 }
 
+static Value cxx_bitwise_and(VM& vm, Value lhs, Value rhs)
+{
+    return TRY_OR_SET_EXCEPTION(bitwise_and(vm, lhs, rhs));
+}
+
+void Compiler::compile_bitwise_and(Bytecode::Op::BitwiseAnd const& op)
+{
+    load_vm_register(ARG1, op.lhs());
+    load_accumulator(ARG2);
+
+    Assembler::Label end {};
+
+    branch_if_both_int32(ARG1, ARG2, [&] {
+        // NOTE: Since both sides are Int32, we know that the upper 32 bits are nothing but the INT32_TAG.
+        //       This means we can get away with just a simple 64-bit bitwise and.
+        m_assembler.bitwise_and(
+            Assembler::Operand::Register(ARG1),
+            Assembler::Operand::Register(ARG2));
+
+        store_accumulator(ARG1);
+        m_assembler.jump(end);
+    });
+
+    native_call((void*)cxx_bitwise_and);
+    store_accumulator(RET);
+    check_exception();
+    end.link(m_assembler);
+}
+
 static ThrowCompletionOr<Value> not_(VM&, Value value)
 {
     return Value(!value.to_boolean());

Userland/Libraries/LibJS/JIT/Compiler.h

@@ -54,7 +54,6 @@ private:
         O(LooselyEquals, abstract_equals)                       \
         O(StrictlyInequals, typed_inequals)                     \
         O(StrictlyEquals, typed_equals)                         \
-        O(BitwiseAnd, bitwise_and)                              \
         O(BitwiseOr, bitwise_or)                                \
         O(BitwiseXor, bitwise_xor)                              \
         O(LeftShift, left_shift)                                \