org.jetbrains.kotlin.backend.wasm.lower.FieldInitializersLowering.kt Maven / Gradle / Ivy

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/*
 * Copyright 2010-2019 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.lower.at
import org.jetbrains.kotlin.backend.common.lower.createIrBuilder
import org.jetbrains.kotlin.backend.wasm.WasmBackendContext
import org.jetbrains.kotlin.ir.IrElement
import org.jetbrains.kotlin.ir.backend.js.utils.isObjectInstanceField
import org.jetbrains.kotlin.ir.builders.irSetField
import org.jetbrains.kotlin.ir.declarations.IrField
import org.jetbrains.kotlin.ir.declarations.IrFile
import org.jetbrains.kotlin.ir.expressions.IrBlockBody
import org.jetbrains.kotlin.ir.expressions.IrConst
import org.jetbrains.kotlin.ir.expressions.IrConstKind
import org.jetbrains.kotlin.ir.expressions.IrExpression
import org.jetbrains.kotlin.ir.util.fqNameWhenAvailable
import org.jetbrains.kotlin.ir.visitors.IrElementVisitorVoid
import org.jetbrains.kotlin.ir.visitors.acceptChildrenVoid
import org.jetbrains.kotlin.name.Name

/**
 * Move initialization of global fields to start function.
 *
 * WebAssembly allows only constant expressions to be used directly in
 * field initializers.
 */
class FieldInitializersLowering(val context: WasmBackendContext) : FileLoweringPass {
    private val stringPoolFqName = context.kotlinWasmInternalPackageFqn.child(Name.identifier("stringPool"))

    override fun lower(irFile: IrFile) {
        val builder = context.createIrBuilder(context.fieldInitFunction.symbol)
        val startFunctionBody = context.fieldInitFunction.body as IrBlockBody

        irFile.acceptChildrenVoid(object : IrElementVisitorVoid {
            override fun visitElement(element: IrElement) {
                element.acceptChildrenVoid(this)
            }

            override fun visitField(declaration: IrField) {
                super.visitField(declaration)

                // External properties can be "initialized" with `= defineExternally`. Ignoring it.
                if (declaration.isExternal) return

                if (!declaration.isStatic) return
                val initValue: IrExpression = declaration.initializer?.expression ?: return
                // Constant primitive initializers without implicit casting can be processed by native wasm initializers
                if (initValue is IrConst) {
                    if (initValue.kind is IrConstKind.Null) return
                    if (initValue.type == declaration.type && initValue.kind !is IrConstKind.String) return
                }

                val initializerStatement = builder.at(initValue).irSetField(null, declaration, initValue)
                val statements = startFunctionBody.statements

                when {
                    declaration.fqNameWhenAvailable == stringPoolFqName -> statements.add(0, initializerStatement)
                    declaration.isObjectInstanceField() -> statements.add(if (statements.size >= 1) 1 else 0, initializerStatement)
                    else -> startFunctionBody.statements.add(initializerStatement)
                }

                // Replace initializer with default one
                declaration.initializer = null
            }
        })
    }
}