[Wasm] Add compiler flag to disable exception handling proposal

Fail with unreachable instead of throwing an exception

Merge-request: KT-MR-11481
Merged-by: Svyatoslav Kuzmich <svyatoslav.kuzmich@jetbrains.com>

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

@@ -24,11 +24,11 @@ import org.jetbrains.kotlin.ir.declarations.impl.IrExternalPackageFragmentImpl
 import org.jetbrains.kotlin.ir.declarations.impl.IrFileImpl
 import org.jetbrains.kotlin.ir.symbols.IrSimpleFunctionSymbol
 import org.jetbrains.kotlin.ir.symbols.impl.DescriptorlessExternalPackageFragmentSymbol
-import org.jetbrains.kotlin.ir.types.IrSimpleType
 import org.jetbrains.kotlin.ir.types.IrTypeSystemContext
 import org.jetbrains.kotlin.ir.types.IrTypeSystemContextImpl
 import org.jetbrains.kotlin.ir.util.SymbolTable
 import org.jetbrains.kotlin.ir.util.addChild
+import org.jetbrains.kotlin.js.config.JSConfigurationKeys
 import org.jetbrains.kotlin.name.FqName
 import org.jetbrains.kotlin.name.Name
 

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

@@ -97,7 +97,10 @@ fun compileWasm(
     generateWat: Boolean = false,
     generateSourceMaps: Boolean = false,
 ): WasmCompilerResult {
-    val compiledWasmModule = WasmCompiledModuleFragment(backendContext.irBuiltIns)
+    val compiledWasmModule = WasmCompiledModuleFragment(
+        backendContext.irBuiltIns,
+        backendContext.configuration.getBoolean(JSConfigurationKeys.WASM_USE_TRAPS_INSTEAD_OF_EXCEPTIONS)
+    )
     val codeGenerator = WasmModuleFragmentGenerator(backendContext, compiledWasmModule, allowIncompleteImplementations = allowIncompleteImplementations)
     allModules.forEach { codeGenerator.collectInterfaceTables(it) }
     allModules.forEach { codeGenerator.generateModule(it) }

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

@@ -137,12 +137,22 @@ class BodyGenerator(
 
     override fun visitThrow(expression: IrThrow) {
         generateExpression(expression.value)
+        if (context.backendContext.configuration.getBoolean(JSConfigurationKeys.WASM_USE_TRAPS_INSTEAD_OF_EXCEPTIONS)) {
+            body.buildUnreachable(SourceLocation.NoLocation("Unreachable is inserted instead of a `throw` instruction"))
+            return
+        }
+
         body.buildThrow(functionContext.tagIdx, expression.getSourceLocation())
     }
 
     override fun visitTry(aTry: IrTry) {
         assert(aTry.isCanonical(irBuiltIns)) { "expected canonical try/catch" }
 
+        if (context.backendContext.configuration.getBoolean(JSConfigurationKeys.WASM_USE_TRAPS_INSTEAD_OF_EXCEPTIONS)) {
+            generateExpression(aTry.tryResult)
+            return
+        }
+
         val resultType = context.transformBlockResultType(aTry.type)
         body.buildTry(null, resultType)
         generateExpression(aTry.tryResult)

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

@@ -15,7 +15,10 @@ import org.jetbrains.kotlin.ir.util.isInterface
 import org.jetbrains.kotlin.wasm.ir.*
 import org.jetbrains.kotlin.wasm.ir.source.location.SourceLocation
 
-class WasmCompiledModuleFragment(val irBuiltIns: IrBuiltIns) {
+class WasmCompiledModuleFragment(
+    val irBuiltIns: IrBuiltIns,
+    generateTrapsInsteadOfExceptions: Boolean,
+) {
     val functions =
         ReferencableAndDefinable<IrFunctionSymbol, WasmFunction>()
     val globalFields =
@@ -49,7 +52,7 @@ class WasmCompiledModuleFragment(val irBuiltIns: IrBuiltIns) {
         ),
         emptyList()
     )
-    val tag = WasmTag(tagFuncType)
+    val tags = if (generateTrapsInsteadOfExceptions) emptyList() else listOf(WasmTag(tagFuncType))
 
     val typeInfo = ReferencableAndDefinable<IrClassSymbol, ConstantDataElement>()
 
@@ -238,7 +241,7 @@ class WasmCompiledModuleFragment(val irBuiltIns: IrBuiltIns) {
             elements = emptyList(),
             data = data,
             dataCount = true,
-            tags = listOf(tag)
+            tags = tags
         )
         module.calculateIds()
         return module