WASM: Generate throw instruction instead of wasmThrow call

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

@@ -340,12 +340,6 @@ private val wasmVarargExpressionLoweringPhase = makeWasmModulePhase(
     description = "Lower varargs"
 )
 
-private val wasmThrowDebugLoweringPhase = makeWasmModulePhase(
-    ::WasmThrowDebugLowering,
-    name = "WasmThrowDebugLowering",
-    description = "Instrument throws with debug print information"
-)
-
 private val fieldInitializersLoweringPhase = makeWasmModulePhase(
     ::FieldInitializersLowering,
     name = "FieldInitializersLowering",
@@ -503,7 +497,6 @@ val wasmPhases = NamedCompilerPhase(
             builtInsLoweringPhase then
 
             virtualDispatchReceiverExtractionPhase then
-            wasmThrowDebugLoweringPhase then
             staticMembersLoweringPhase then
             wasmNullSpecializationLowering then
             validateIrAfterLowering

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

@@ -138,8 +138,6 @@ class WasmSymbols(
     val nullableFloatIeee754Equals = getInternalFunction("nullableFloatIeee754Equals")
     val nullableDoubleIeee754Equals = getInternalFunction("nullableDoubleIeee754Equals")
 
-    val wasmThrow = getInternalFunction("wasmThrow")
-
     val exportString = getInternalFunction("exportString")
     val unsafeGetScratchRawMemory = getInternalFunction("unsafeGetScratchRawMemory")
 

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

@@ -23,6 +23,7 @@ import org.jetbrains.kotlin.ir.types.*
 import org.jetbrains.kotlin.ir.util.*
 import org.jetbrains.kotlin.ir.visitors.IrElementVisitorVoid
 import org.jetbrains.kotlin.ir.visitors.acceptVoid
+import org.jetbrains.kotlin.psi2ir.intermediate.generateExpressionValue
 import org.jetbrains.kotlin.wasm.ir.*
 
 class BodyGenerator(val context: WasmFunctionCodegenContext) : IrElementVisitorVoid {
@@ -61,6 +62,11 @@ class BodyGenerator(val context: WasmFunctionCodegenContext) : IrElementVisitorV
         error("Unexpected element of type ${element::class}")
     }
 
+    override fun visitThrow(expression: IrThrow) {
+        generateExpression(expression.value)
+        body.buildThrow(context.tagIdx)
+    }
+
     override fun visitTypeOperator(expression: IrTypeOperatorCall) {
         when (expression.operator) {
             IrTypeOperator.REINTERPRET_CAST -> generateExpression(expression.argument)

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

@@ -33,6 +33,8 @@ class WasmCompiledModuleFragment {
         ReferencableElements<WasmSignature, Int>()
     val stringLiteralId =
         ReferencableElements<String, Int>()
+    val tagFuncType = WasmFunctionType("ex_handling_tag", listOf(WasmAnyRef), emptyList())
+    val tag = WasmTag(tagFuncType)
 
     val runtimeTypes =
         ReferencableAndDefinable<IrClassSymbol, WasmGlobal>()
@@ -250,7 +252,7 @@ class WasmCompiledModuleFragment {
         val sortedRttGlobals = runtimeTypes.elements.sortedBy { (it.type as WasmRtt).depth }
 
         val module = WasmModule(
-            functionTypes = functionTypes.elements,
+            functionTypes = functionTypes.elements + tagFuncType,
             gcTypes = gcTypes.elements,
             importsInOrder = importedFunctions,
             importedFunctions = importedFunctions,
@@ -261,7 +263,8 @@ class WasmCompiledModuleFragment {
             exports = exports,
             startFunction = startFunction!!,
             elements = listOf(elements) + interfaceTableElements,
-            data = data
+            data = data,
+            tags = listOf(tag)
         )
         module.calculateIds()
         return module

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

@@ -24,5 +24,8 @@ interface WasmFunctionCodegenContext : WasmBaseCodegenContext {
     fun defineLoopLevel(irLoop: IrLoop, labelType: LoopLabelType, level: Int)
     fun referenceLoopLevel(irLoop: IrLoop, labelType: LoopLabelType): Int
 
+    // So far always a single tag
+    val tagIdx: Int
+
     val bodyGen: WasmExpressionBuilder
 }

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

@@ -23,6 +23,9 @@ class WasmFunctionCodegenContextImpl(
     override val bodyGen: WasmExpressionBuilder =
         WasmIrExpressionBuilder(wasmFunction.instructions)
 
+    override val tagIdx: Int
+        get() = 0
+
     private val wasmLocals = LinkedHashMap<IrValueSymbol, WasmLocal>()
     private val loopLevels = LinkedHashMap<Pair<IrLoop, LoopLabelType>, Int>()
 

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

@@ -1,37 +0,0 @@
-/*
- * Copyright 2010-2020 JetBrains s.r.o. and Kotlin Programming Language contributors.
- * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
- */
-
-package org.jetbrains.kotlin.backend.wasm.lower
-
-import org.jetbrains.kotlin.backend.common.FileLoweringPass
-import org.jetbrains.kotlin.backend.common.IrElementTransformerVoidWithContext
-import org.jetbrains.kotlin.backend.common.lower.createIrBuilder
-import org.jetbrains.kotlin.backend.wasm.WasmBackendContext
-import org.jetbrains.kotlin.ir.builders.irCall
-import org.jetbrains.kotlin.ir.declarations.IrFile
-import org.jetbrains.kotlin.ir.expressions.IrExpression
-import org.jetbrains.kotlin.ir.expressions.IrThrow
-import org.jetbrains.kotlin.ir.visitors.transformChildrenVoid
-
-/**
- * Replace throw expressions with a runtime function call.
- * TODO: Remove when full-blown exception handling is implemented
- */
-internal class WasmThrowDebugLowering(
-    private val context: WasmBackendContext
-) : FileLoweringPass, IrElementTransformerVoidWithContext() {
-    override fun lower(irFile: IrFile) {
-        irFile.transformChildrenVoid(this)
-    }
-
-    override fun visitThrow(expression: IrThrow): IrExpression {
-        expression.transformChildrenVoid(this)
-        val builder = context.createIrBuilder(currentScope!!.scope.scopeOwnerSymbol)
-
-        return builder.irCall(context.wasmSymbols.wasmThrow).apply {
-            this.putValueArgument(0, expression.value)
-        }
-    }
-}

js/js.tests/test/org/jetbrains/kotlin/js/test/BasicWasmBoxTest.kt

@@ -86,6 +86,7 @@ abstract class BasicWasmBoxTest(
                 .run(
                     "--experimental-wasm-typed-funcref",
                     "--experimental-wasm-gc",
+                    "--experimental-wasm-eh",
                     outputJsFile
                 )
         }

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

@@ -67,8 +67,3 @@ internal fun <T, R> boxIntrinsic(x: T): R =
 @ExcludedFromCodegen
 internal fun <T, R> unboxIntrinsic(x: T): R =
     implementedAsIntrinsic
-
-internal fun wasmThrow(e: Throwable): Nothing {
-    println("Kotlin/Wasm exception wasm thrown: ${e.message}")
-    wasm_unreachable()
-}

wasm/wasm.ir/src/org/jetbrains/kotlin/wasm/ir/WasmExpressionBuilder.kt

@@ -72,6 +72,14 @@ abstract class WasmExpressionBuilder {
         buildInstr(WasmOp.BR, WasmImmediate.LabelIdx(relativeLevel))
     }
 
+    fun buildThrow(tagIdx: Int) {
+        buildInstr(WasmOp.THROW, WasmImmediate.TagIdx(tagIdx))
+    }
+
+    fun buildCatch(tagIdx: Int) {
+        buildInstr(WasmOp.CATCH, WasmImmediate.TagIdx(tagIdx))
+    }
+
     fun buildBrIf(absoluteBlockLevel: Int) {
         val relativeLevel = numberOfNestedBlocks - absoluteBlockLevel
         assert(relativeLevel >= 0) { "Negative relative block index" }