[Wasm] Add fast path for null in externRefToAny

- Introduce new intrinsics `wasm_ref_cast_null` & `wasm_ref_test_null`.
- Support getting type for immediate from generic argument.
- Remove redundant null check in `tryGetOrSetExternrefBox`.

compiler/ir/backend.wasm/src/org/jetbrains/kotlin/backend/wasm/compiler.kt

@@ -109,8 +109,8 @@ fun WasmCompiledModuleFragment.generateJs(): String {
     //language=js
     val runtime = """
     const externrefBoxes = new WeakMap();
+    // ref must be non-null
     function tryGetOrSetExternrefBox(ref, ifNotCached) {
-        if (ref == null) return null;
         if (typeof ref !== 'object') return ifNotCached;
         const cachedBox = externrefBoxes.get(ref);
         if (cachedBox !== void 0) return cachedBox;

compiler/ir/backend.wasm/src/org/jetbrains/kotlin/backend/wasm/ir2wasm/BodyGenerator.kt

@@ -461,7 +461,7 @@ class BodyGenerator(
         call: IrFunctionAccessExpression,
         function: IrFunction
     ): Boolean {
-        if (tryToGenerateWasmOpIntrinsicCall(function)) {
+        if (tryToGenerateWasmOpIntrinsicCall(call, function)) {
             return true
         }
 
@@ -840,7 +840,7 @@ class BodyGenerator(
     }
 
     // Return true if function is recognized as intrinsic.
-    private fun tryToGenerateWasmOpIntrinsicCall(function: IrFunction): Boolean {
+    private fun tryToGenerateWasmOpIntrinsicCall(call: IrFunctionAccessExpression, function: IrFunction): Boolean {
         if (function.hasWasmNoOpCastAnnotation()) {
             return true
         }
@@ -853,14 +853,19 @@ class BodyGenerator(
                     body.buildInstr(op)
                 }
                 1 -> {
+                    fun getReferenceGcType(): WasmSymbol<WasmTypeDeclaration> {
+                        val type = function.dispatchReceiverParameter?.type ?: call.getTypeArgument(0)!!
+                        return context.referenceGcType(type.classOrNull!!)
+                    }
+
                     val immediates = arrayOf(
                         when (val imm = op.immediates[0]) {
                             WasmImmediateKind.MEM_ARG ->
                                 WasmImmediate.MemArg(0u, 0u)
                             WasmImmediateKind.STRUCT_TYPE_IDX ->
-                                WasmImmediate.GcType(context.referenceGcType(function.dispatchReceiverParameter!!.type.classOrNull!!))
+                                WasmImmediate.GcType(getReferenceGcType())
                             WasmImmediateKind.TYPE_IDX ->
-                                WasmImmediate.TypeIdx(context.referenceGcType(function.dispatchReceiverParameter!!.type.classOrNull!!))
+                                WasmImmediate.TypeIdx(getReferenceGcType())
 
                             else ->
                                 error("Immediate $imm is unsupported")

libraries/stdlib/wasm/internal/kotlin/wasm/internal/ExternalWrapper.kt

@@ -141,13 +141,13 @@ internal fun externRefToAny(ref: ExternalInterfaceType): Any? {
     // TODO rewrite it so to get something like:
     // block {
     //     refAsAnyref
-    //     br_on_cast_fail 0 $kotlin.Any
+    //     br_on_cast_fail null 0 $kotlin.Any
     //     return
     // }
     // If ref is an instance of kotlin class -- return it casted to Any
     val refAsAnyref = ref.externAsWasmAnyref()
-    if (wasm_ref_test<Any>(refAsAnyref)) {
-        return wasm_ref_cast<Any>(refAsAnyref)
+    if (wasm_ref_test_null<Any>(refAsAnyref)) {
+        return wasm_ref_cast_null<Any>(refAsAnyref)
     }
 
     // If we have Null in notNullRef -- return null

libraries/stdlib/wasm/internal/kotlin/wasm/internal/WasmInstructions.kt

@@ -22,9 +22,19 @@ internal fun wasm_unreachable(): Nothing =
 internal fun <To> wasm_ref_cast(a: Any?): To =
     implementedAsIntrinsic
 
+@Suppress("REIFIED_TYPE_PARAMETER_NO_INLINE")
+@WasmOp(WasmOp.REF_CAST_NULL)
+internal fun <reified To> wasm_ref_cast_null(a: Any?): To =
+    implementedAsIntrinsic
+
 internal fun <To> wasm_ref_test(a: Any?): Boolean =
     implementedAsIntrinsic
 
+@Suppress("REIFIED_TYPE_PARAMETER_NO_INLINE")
+@WasmOp(WasmOp.REF_TEST_NULL)
+internal fun <reified To> wasm_ref_test_null(a: Any?): Boolean =
+    implementedAsIntrinsic
+
 internal fun <T> wasm_array_copy(destination: T, destinationIndex: Int, source: T, sourceIndex: Int, length: Int): Unit =
     implementedAsIntrinsic