WASM: Canonicalize catches without finally blocks

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

@@ -298,6 +298,13 @@ private val returnableBlockLoweringPhase = makeWasmModulePhase(
     prerequisite = setOf(functionInliningPhase)
 )
 
+private val tryCatchCanonicalization = makeWasmModulePhase(
+    ::TryCatchCanonicalization,
+    name = "TryCatchCanonicalization",
+    description = "Transforms try/catch statements into canonical form supported by the wasm codegen",
+    prerequisite = setOf(functionInliningPhase)
+)
+
 private val bridgesConstructionPhase = makeWasmModulePhase(
     ::WasmBridgesConstruction,
     name = "BridgesConstruction",
@@ -461,6 +468,7 @@ val wasmPhases = NamedCompilerPhase(
 
             stringConstructorLowering then
             returnableBlockLoweringPhase then
+            tryCatchCanonicalization then
 
             forLoopsLoweringPhase then
             propertyAccessorInlinerLoweringPhase then

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

@@ -0,0 +1,104 @@
+/*
+ * Copyright 2010-2021 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.*
+import org.jetbrains.kotlin.backend.wasm.WasmBackendContext
+import org.jetbrains.kotlin.backend.wasm.utils.isCanonical
+import org.jetbrains.kotlin.ir.IrElement
+import org.jetbrains.kotlin.ir.builders.*
+import org.jetbrains.kotlin.ir.builders.declarations.buildVariable
+import org.jetbrains.kotlin.ir.declarations.IrDeclarationOrigin
+import org.jetbrains.kotlin.ir.declarations.IrFile
+import org.jetbrains.kotlin.ir.expressions.IrExpression
+import org.jetbrains.kotlin.ir.expressions.IrTry
+import org.jetbrains.kotlin.ir.visitors.*
+import org.jetbrains.kotlin.name.Name
+
+// This pass transforms try/catch statements into a simple canonical form which is easily mapped into wasm instruction set.
+// From this:
+//    try {
+//        ...exprs
+//    } catch (e: Foo) {
+//        ...exprs
+//    } catch (e: Bar) {
+//        ...exprs
+//    } finally {
+//        ...exprs
+//    }
+// We get this:
+//    try {
+//        ...exprs
+//    } catch (e: Throwable) {
+//        when (e) {
+//            is Foo -> ...exprs
+//            is Bar -> ...exprs
+//        }
+//    }
+// TODO: Describe finally transformation
+
+internal class TryCatchCanonicalization(private val ctx: WasmBackendContext) : FileLoweringPass {
+    override fun lower(irFile: IrFile) {
+        irFile.transformChildrenVoid(CatchMerger(ctx))
+
+        irFile.acceptVoid(object : IrElementVisitorVoid {
+            override fun visitElement(element: IrElement) {
+                element.acceptChildrenVoid(this)
+            }
+
+            override fun visitTry(aTry: IrTry) {
+                check(aTry.isCanonical(ctx.irBuiltIns)) { "Found non canonical try/catch $aTry" }
+            }
+        })
+    }
+}
+
+internal class CatchMerger(private val ctx: WasmBackendContext): IrElementTransformerVoidWithContext() {
+    override fun visitTry(aTry: IrTry): IrExpression {
+        // First, handle all nested constructs
+        aTry.transformChildrenVoid(this)
+
+        // Nothing to do
+        if (aTry.catches.isEmpty() ||
+            aTry.catches.singleOrNull()?.catchParameter?.symbol?.owner?.type == ctx.irBuiltIns.throwableType)
+            return aTry
+
+        ctx.createIrBuilder(currentScope!!.scope.scopeOwnerSymbol).run {
+            val newCatchParameter = buildVariable(
+                currentScope!!.scope.getLocalDeclarationParent(),
+                startOffset,
+                endOffset,
+                IrDeclarationOrigin.CATCH_PARAMETER,
+                Name.identifier("merged_catch_param"),
+                ctx.irBuiltIns.throwableType
+            )
+
+            val newCatchBody = irBlock(aTry) {
+                +irWhen(
+                    aTry.type,
+                    aTry.catches.map {
+                        irBranch(
+                            irIs(irGet(newCatchParameter), it.catchParameter.type),
+                            irBlock(it.result) {
+                                it.catchParameter.initializer = irImplicitCast(irGet(newCatchParameter), it.catchParameter.type)
+                                it.catchParameter.origin = IrDeclarationOrigin.DEFINED
+                                +it.catchParameter
+                                +it.result
+                            }
+                        )
+                    } + irElseBranch(irThrow(irGet(newCatchParameter)))
+                )
+            }
+
+            val newCatch = irCatch(newCatchParameter, newCatchBody)
+
+            return irTry(aTry.type, aTry.tryResult, listOf(newCatch), aTry.finallyExpression)
+        }
+    }
+}
+

compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/builders/ExpressionHelpers.kt

@@ -336,6 +336,9 @@ fun IrBuilderWithScope.irVararg(elementType: IrType, values: List<IrExpression>)
 fun IrBuilderWithScope.irRawFunctionReferefence(type: IrType, symbol: IrFunctionSymbol) =
     IrRawFunctionReferenceImpl(startOffset, endOffset, type, symbol)
 
+fun IrBuilderWithScope.irTry(type: IrType, tryResult: IrExpression, catches: List<IrCatch>, finallyExpression: IrExpression?) =
+    IrTryImpl(startOffset, endOffset, type, tryResult, catches, finallyExpression)
+
 inline fun IrBuilderWithScope.irBlock(
     startOffset: Int = this.startOffset,
     endOffset: Int = this.endOffset,

compiler/testData/codegen/box/controlStructures/tcbInEliminatedCondition.kt

@@ -1,5 +1,3 @@
-// IGNORE_BACKEND: WASM
-
 fun foo() {}
 
 inline fun test1(v: Int) {

compiler/testData/codegen/box/enum/initEntriesInCompanionObject.kt

@@ -1,5 +1,4 @@
 // IGNORE_BACKEND: JS
-// IGNORE_BACKEND: WASM
 
 var l = ""
 

compiler/testData/codegen/box/enum/initEntriesInValueOf.kt

@@ -1,5 +1,4 @@
 // IGNORE_BACKEND: JS
-// IGNORE_BACKEND: WASM
 
 var l = ""
 

compiler/testData/codegen/box/properties/unreachableUninitializedProperty.kt

@@ -1,5 +1,3 @@
-// IGNORE_BACKEND: WASM
-// WASM_MUTE_REASON: EXCEPTIONS_NOT_IMPLEMENTED
 // WITH_RUNTIME
 // KT-44496