diff --git a/.idea/misc.xml b/.idea/misc.xml
index d1ca2e70450..8ff9c44e7a1 100644
--- a/.idea/misc.xml
+++ b/.idea/misc.xml
@@ -95,4 +95,4 @@
   <component name="intellij-api-watcher-check-current-project">
     <option name="shouldCheckCurrentProject" value="true" />
   </component>
-</project>
\ No newline at end of file
+</project>
diff --git a/compiler/cli/cli-js/src/org/jetbrains/kotlin/cli/js/K2JsIrCompiler.kt b/compiler/cli/cli-js/src/org/jetbrains/kotlin/cli/js/K2JsIrCompiler.kt
index bf58b331a9e..d115563b7eb 100644
--- a/compiler/cli/cli-js/src/org/jetbrains/kotlin/cli/js/K2JsIrCompiler.kt
+++ b/compiler/cli/cli-js/src/org/jetbrains/kotlin/cli/js/K2JsIrCompiler.kt
@@ -36,11 +36,14 @@ import org.jetbrains.kotlin.incremental.js.IncrementalDataProvider
 import org.jetbrains.kotlin.incremental.js.IncrementalNextRoundChecker
 import org.jetbrains.kotlin.incremental.js.IncrementalResultsConsumer
 import org.jetbrains.kotlin.ir.backend.js.*
+import org.jetbrains.kotlin.ir.backend.js.ic.actualizeCacheForModule
+import org.jetbrains.kotlin.ir.backend.js.ic.buildCache
+import org.jetbrains.kotlin.ir.backend.js.ic.checkCaches
+import org.jetbrains.kotlin.ir.declarations.impl.IrFactoryImpl
 import org.jetbrains.kotlin.ir.backend.js.codegen.JsGenerationGranularity
 import org.jetbrains.kotlin.ir.backend.js.ic.*
 import org.jetbrains.kotlin.ir.backend.js.transformers.irToJs.IrModuleToJsTransformer
 import org.jetbrains.kotlin.ir.backend.js.transformers.irToJs.IrModuleToJsTransformerTmp
-import org.jetbrains.kotlin.ir.declarations.impl.IrFactoryImpl
 import org.jetbrains.kotlin.ir.declarations.persistent.PersistentIrFactory
 import org.jetbrains.kotlin.js.analyzer.JsAnalysisResult
 import org.jetbrains.kotlin.js.config.*
diff --git a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/JsIntrinsics.kt b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/JsIntrinsics.kt
index b9573374d44..54d8180b30b 100644
--- a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/JsIntrinsics.kt
+++ b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/JsIntrinsics.kt
@@ -26,6 +26,9 @@ class JsIntrinsics(private val irBuiltIns: IrBuiltIns, val context: JsIrBackendC
 
     // TODO: Should we drop operator intrinsics in favor of IrDynamicOperatorExpression?
 
+    // Global variables
+    val globalThis = getInternalProperty("globalThis")
+
     // Equality operations:
 
     val jsEqeq = getInternalFunction("jsEqeq")
@@ -328,6 +331,9 @@ class JsIntrinsics(private val irBuiltIns: IrBuiltIns, val context: JsIrBackendC
     private fun getInternalFunction(name: String) =
         context.symbolTable.referenceSimpleFunction(context.getJsInternalFunction(name))
 
+    private fun getInternalProperty(name: String) =
+        context.symbolTable.referenceProperty(context.getJsInternalProperty(name))
+
     private fun getInternalWithoutPackage(name: String) =
         context.symbolTable.referenceSimpleFunction(context.getFunctions(FqName(name)).single())
 
diff --git a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/JsIrBackendContext.kt b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/JsIrBackendContext.kt
index 3c12accc901..d8824709d09 100644
--- a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/JsIrBackendContext.kt
+++ b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/JsIrBackendContext.kt
@@ -123,6 +123,7 @@ class JsIrBackendContext(
         // TODO: what is more clear way reference this getter?
         private val REFLECT_PACKAGE_FQNAME = KOTLIN_PACKAGE_FQN.child(Name.identifier("reflect"))
         private val JS_PACKAGE_FQNAME = KOTLIN_PACKAGE_FQN.child(Name.identifier("js"))
+        private val JS_POLYFILLS_PACKAGE = JS_PACKAGE_FQNAME.child(Name.identifier("polyfill"))
         private val JS_INTERNAL_PACKAGE_FQNAME = JS_PACKAGE_FQNAME.child(Name.identifier("internal"))
 
         // TODO: due to name clash those weird suffix is required, remove it once `MemberNameGenerator` is implemented
@@ -334,6 +335,10 @@ class JsIrBackendContext(
     internal fun getJsInternalFunction(name: String): SimpleFunctionDescriptor =
         findFunctions(internalPackage.memberScope, Name.identifier(name)).singleOrNull() ?: error("Internal function '$name' not found")
 
+    internal fun getJsInternalProperty(name: String): PropertyDescriptor =
+        findProperty(internalPackage.memberScope, Name.identifier(name)).singleOrNull() ?: error("Internal function '$name' not found")
+
+
     fun getFunctions(fqName: FqName): List<SimpleFunctionDescriptor> =
         findFunctions(module.getPackage(fqName.parent()).memberScope, fqName.shortName())
 
diff --git a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/JsLoweringPhases.kt b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/JsLoweringPhases.kt
index 73a4e7e968a..8860319ef43 100644
--- a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/JsLoweringPhases.kt
+++ b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/JsLoweringPhases.kt
@@ -784,6 +784,12 @@ private val captureStackTraceInThrowablesPhase = makeBodyLoweringPhase(
     description = "Capture stack trace in Throwable constructors"
 )
 
+private val escapedIdentifiersLowering = makeBodyLoweringPhase(
+    ::EscapedIdentifiersLowering,
+    name = "EscapedIdentifiersLowering",
+    description = "Convert global variables with invalid names access to globalThis member expression"
+)
+
 private val cleanupLoweringPhase = makeBodyLoweringPhase(
     { CleanupLowering() },
     name = "CleanupLowering",
@@ -903,6 +909,7 @@ val loweringList = listOf<Lowering>(
     objectUsageLoweringPhase,
     captureStackTraceInThrowablesPhase,
     callsLoweringPhase,
+    escapedIdentifiersLowering,
     cleanupLoweringPhase,
     // Currently broken due to static members lowering making single-open-class
     // files non-recognizable as single-class files
diff --git a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/lower/EscapedIdentifiersLowering.kt b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/lower/EscapedIdentifiersLowering.kt
new file mode 100644
index 00000000000..70ed0cf71ea
--- /dev/null
+++ b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/lower/EscapedIdentifiersLowering.kt
@@ -0,0 +1,162 @@
+/*
+ * 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.ir.backend.js.lower
+
+import org.jetbrains.kotlin.backend.common.BodyLoweringPass
+import org.jetbrains.kotlin.backend.common.runOnFilePostfix
+import org.jetbrains.kotlin.config.LanguageFeature
+import org.jetbrains.kotlin.config.languageVersionSettings
+import org.jetbrains.kotlin.ir.UNDEFINED_OFFSET
+import org.jetbrains.kotlin.ir.backend.js.JsIrBackendContext
+import org.jetbrains.kotlin.ir.backend.js.utils.getJsNameOrKotlinName
+import org.jetbrains.kotlin.ir.backend.js.utils.hasStableJsName
+import org.jetbrains.kotlin.ir.backend.js.utils.realOverrideTarget
+import org.jetbrains.kotlin.ir.declarations.*
+import org.jetbrains.kotlin.ir.expressions.*
+import org.jetbrains.kotlin.ir.expressions.impl.*
+import org.jetbrains.kotlin.ir.symbols.impl.IrFieldSymbolImpl
+import org.jetbrains.kotlin.ir.symbols.impl.IrValueParameterSymbolImpl
+import org.jetbrains.kotlin.ir.util.isEffectivelyExternal
+import org.jetbrains.kotlin.ir.visitors.IrElementTransformerVoid
+import org.jetbrains.kotlin.ir.visitors.transformChildrenVoid
+import org.jetbrains.kotlin.js.common.isValidES5Identifier
+import org.jetbrains.kotlin.js.config.JSConfigurationKeys
+import org.jetbrains.kotlin.name.SpecialNames
+import org.jetbrains.kotlin.serialization.js.ModuleKind
+
+class EscapedIdentifiersLowering(context: JsIrBackendContext) : BodyLoweringPass {
+    private val transformer = ReferenceTransformer(context)
+    private val moduleKind = context.configuration[JSConfigurationKeys.MODULE_KIND]!!
+    private val isEscapedIdentifiersResolved =
+        context.configuration.languageVersionSettings.supportsFeature(LanguageFeature.JsAllowInvalidCharsIdentifiersEscaping)
+
+    override fun lower(irFile: IrFile) {
+        if (!isEscapedIdentifiersResolved || moduleKind != ModuleKind.PLAIN) return
+        runOnFilePostfix(irFile, withLocalDeclarations = true)
+    }
+
+    override fun lower(irBody: IrBody, container: IrDeclaration) {
+        if (!isEscapedIdentifiersResolved || moduleKind != ModuleKind.PLAIN) return
+        irBody.transformChildrenVoid(transformer)
+    }
+
+    private class ReferenceTransformer(val context: JsIrBackendContext) : IrElementTransformerVoid() {
+        private val globalThisReceiver
+            get() = IrCallImpl(
+                startOffset = UNDEFINED_OFFSET,
+                endOffset = UNDEFINED_OFFSET,
+                type = context.dynamicType,
+                symbol = context.intrinsics.globalThis.owner.getter!!.symbol,
+                typeArgumentsCount = 0,
+                valueArgumentsCount = 0,
+            )
+
+        private val IrFunction.dummyDispatchReceiverParameter
+            get() = context.irFactory.createValueParameter(
+                startOffset, endOffset,
+                origin,
+                IrValueParameterSymbolImpl(),
+                SpecialNames.THIS,
+                -1,
+                context.irBuiltIns.anyType,
+                null,
+                isCrossinline = false,
+                isNoinline = false,
+                isHidden = false,
+                isAssignable = false
+            ).also { it.parent = this }
+
+        override fun visitGetValue(expression: IrGetValue): IrExpression {
+            val owner = expression.symbol.owner
+
+            return if (
+                !owner.isEffectivelyExternal() ||
+                owner.isThisReceiver() ||
+                !owner.needToBeWrappedWithGlobalThis()
+            ) {
+                super.visitGetValue(expression)
+            } else {
+                owner.wrapInGlobalThis(expression)
+            }
+        }
+
+        override fun visitSetValue(expression: IrSetValue): IrExpression {
+            val field = expression.symbol.owner
+
+            return if (
+                !field.isEffectivelyExternal() ||
+                !field.needToBeWrappedWithGlobalThis()
+            ) {
+                super.visitSetValue(expression)
+            } else {
+                IrSetFieldImpl(
+                    startOffset = expression.startOffset,
+                    endOffset = expression.endOffset,
+                    receiver = field.wrapInGlobalThis(expression),
+                    value = expression.value,
+                    type = expression.type,
+                    origin = null,
+                    superQualifierSymbol = null,
+                    symbol = IrFieldSymbolImpl(),
+                )
+            }
+        }
+
+        override fun visitGetObjectValue(expression: IrGetObjectValue): IrExpression {
+            val owner = expression.symbol.owner
+
+            return if (
+                !owner.isEffectivelyExternal() ||
+                !owner.needToBeWrappedWithGlobalThis()
+            ) {
+                super.visitGetObjectValue(expression)
+            } else {
+                owner.wrapInGlobalThis(expression)
+            }
+        }
+
+        override fun visitCall(expression: IrCall): IrExpression {
+            val function = expression.symbol.owner.realOverrideTarget
+            val property = function.correspondingPropertySymbol?.owner ?: function
+
+            val updatedCall = if (
+                expression.dispatchReceiver != null ||
+                !property.isEffectivelyExternal() ||
+                !property.needToBeWrappedWithGlobalThis()
+            ) {
+                expression
+            } else {
+                expression
+                    .apply { dispatchReceiver = globalThisReceiver }
+                    .also {
+                        if (function.dispatchReceiverParameter == null) {
+                            function.dispatchReceiverParameter = function.dummyDispatchReceiverParameter
+                        }
+                    }
+            }
+
+            return super.visitCall(updatedCall)
+        }
+
+        private fun IrDeclarationWithName.needToBeWrappedWithGlobalThis(): Boolean =
+            !getJsNameOrKotlinName().toString().isValidES5Identifier()
+
+        private fun IrDeclarationWithName.wrapInGlobalThis(expression: IrExpression): IrDynamicMemberExpression =
+            IrDynamicMemberExpressionImpl(
+                startOffset = expression.startOffset,
+                endOffset = expression.endOffset,
+                type = expression.type,
+                memberName = getJsNameOrKotlinName().asString(),
+                receiver = globalThisReceiver
+            )
+
+        private fun IrValueDeclaration.isThisReceiver(): Boolean = this !is IrVariable && when (val p = parent) {
+            is IrSimpleFunction -> this === p.dispatchReceiverParameter
+            is IrClass -> this === p.thisReceiver
+            else -> false
+        }
+    }
+}
\ No newline at end of file
diff --git a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/transformers/irToJs/IrElementToJsExpressionTransformer.kt b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/transformers/irToJs/IrElementToJsExpressionTransformer.kt
index df342749788..d13f72bea6e 100644
--- a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/transformers/irToJs/IrElementToJsExpressionTransformer.kt
+++ b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/transformers/irToJs/IrElementToJsExpressionTransformer.kt
@@ -111,6 +111,7 @@ class IrElementToJsExpressionTransformer : BaseIrElementToJsNodeTransformer<JsEx
                     expression
                 )
             return JsNameRef(field.getJsNameOrKotlinName().identifier, receiver).withSource(expression, context)
+                .also { context.staticContext.polyfills.visitDeclaration(field) }
         }
 
         if (fieldParent is IrClass && fieldParent.isInline) {
@@ -121,9 +122,11 @@ class IrElementToJsExpressionTransformer : BaseIrElementToJsNodeTransformer<JsEx
     }
 
     override fun visitGetValue(expression: IrGetValue, context: JsGenerationContext): JsExpression {
-        if (expression.symbol.owner.isThisReceiver()) return JsThisRef().withSource(expression, context)
-        val possibleGlobalVarRef = context.getNameForValueDeclaration(expression.symbol.owner).makeRef().withSource(expression, context)
-        return jsGlobalVarRef(possibleGlobalVarRef)
+        val owner = expression.symbol.owner
+        if (owner.isThisReceiver()) return JsThisRef().withSource(expression, context)
+
+        return context.getNameForValueDeclaration(owner).makeRef().withSource(expression, context)
+            .also { context.staticContext.polyfills.visitDeclaration(owner) }
     }
 
     override fun visitGetObjectValue(expression: IrGetObjectValue, context: JsGenerationContext): JsExpression {
@@ -131,22 +134,24 @@ class IrElementToJsExpressionTransformer : BaseIrElementToJsNodeTransformer<JsEx
         assert(obj.kind == ClassKind.OBJECT)
         assert(obj.isEffectivelyExternal()) { "Non external IrGetObjectValue must be lowered" }
 
-        val possibleGlobalVarRef = context.getRefForExternalClass(obj).withSource(expression, context)
-        return jsGlobalVarRef(possibleGlobalVarRef)
+        return context.getRefForExternalClass(obj).withSource(expression, context)
     }
 
     override fun visitSetField(expression: IrSetField, context: JsGenerationContext): JsExpression {
-        val fieldName = context.getNameForField(expression.symbol.owner)
+        val field = expression.symbol.owner
+        val fieldName = context.getNameForField(field)
         val dest = jsElementAccess(fieldName.ident, expression.receiver?.accept(this, context))
         val source = expression.value.accept(this, context)
         return jsAssignment(dest, source).withSource(expression, context)
+            .also { context.staticContext.polyfills.visitDeclaration(field) }
     }
 
     override fun visitSetValue(expression: IrSetValue, context: JsGenerationContext): JsExpression {
-        val possibleGlobalRef = JsNameRef(context.getNameForValueDeclaration(expression.symbol.owner))
-        val ref = jsGlobalVarRef(possibleGlobalRef)
+        val field = expression.symbol.owner
+        val ref = JsNameRef(context.getNameForValueDeclaration(field))
         val value = expression.value.accept(this, context)
         return JsBinaryOperation(JsBinaryOperator.ASG, ref, value).withSource(expression, context)
+            .also { context.staticContext.polyfills.visitDeclaration(field) }
     }
 
     override fun visitDelegatingConstructorCall(expression: IrDelegatingConstructorCall, context: JsGenerationContext): JsExpression {
@@ -250,6 +255,10 @@ class IrElementToJsExpressionTransformer : BaseIrElementToJsNodeTransformer<JsEx
 
         }
         return translateCall(expression, context, this).withSource(expression, context)
+            .also {
+                val function = expression.symbol.owner
+                context.staticContext.polyfills.visitDeclaration(function.correspondingPropertySymbol?.owner ?: function)
+            }
     }
 
     override fun visitWhen(expression: IrWhen, context: JsGenerationContext): JsExpression {
diff --git a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/transformers/irToJs/IrElementToJsStatementTransformer.kt b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/transformers/irToJs/IrElementToJsStatementTransformer.kt
index e943ea7d153..1ea96b78956 100644
--- a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/transformers/irToJs/IrElementToJsStatementTransformer.kt
+++ b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/transformers/irToJs/IrElementToJsStatementTransformer.kt
@@ -84,9 +84,11 @@ class IrElementToJsStatementTransformer : BaseIrElementToJsNodeTransformer<JsSta
     }
 
     override fun visitSetValue(expression: IrSetValue, context: JsGenerationContext): JsStatement {
-        val ref = JsNameRef(context.getNameForValueDeclaration(expression.symbol.owner))
+        val owner = expression.symbol.owner
+        val ref = JsNameRef(context.getNameForValueDeclaration(owner))
         return expression.value
             .maybeOptimizeIntoSwitch(context) { jsAssignment(ref, it).withSource(expression, context).makeStmt() }
+            .also { context.staticContext.polyfills.visitDeclaration(owner) }
     }
 
     override fun visitReturn(expression: IrReturn, context: JsGenerationContext): JsStatement {
@@ -153,6 +155,7 @@ class IrElementToJsStatementTransformer : BaseIrElementToJsNodeTransformer<JsSta
             }
         }
         return translateCall(expression, data, IrElementToJsExpressionTransformer()).withSource(expression, data).makeStmt()
+            .also { data.staticContext.polyfills.visitDeclaration(expression.symbol.owner) }
     }
 
     override fun visitInstanceInitializerCall(expression: IrInstanceInitializerCall, context: JsGenerationContext): JsStatement {
diff --git a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/transformers/irToJs/IrModuleToJsTransformer.kt b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/transformers/irToJs/IrModuleToJsTransformer.kt
index 45e79292bb8..f67732cc6e2 100644
--- a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/transformers/irToJs/IrModuleToJsTransformer.kt
+++ b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/transformers/irToJs/IrModuleToJsTransformer.kt
@@ -42,8 +42,7 @@ class IrModuleToJsTransformer(
     private val multiModule: Boolean = false,
     private val relativeRequirePath: Boolean = false,
     private val moduleToName: Map<IrModuleFragment, String> = emptyMap(),
-    private val removeUnusedAssociatedObjects: Boolean = true,
-    private val generateGlobalThisPolyfill: Boolean = false
+    private val removeUnusedAssociatedObjects: Boolean = true
 ) {
     private val generateRegionComments = backendContext.configuration.getBoolean(JSConfigurationKeys.GENERATE_REGION_COMMENTS)
 
@@ -152,7 +151,6 @@ class IrModuleToJsTransformer(
             )
 
         val moduleBody = generateModuleBody(modules, staticContext)
-
         val internalModuleName = JsName("_", false)
         val globalNames = NameTable<String>(namer.globalNames)
         val exportStatements = ExportModelToJsStatements(nameGenerator) { globalNames.declareFreshName(it, it) }
@@ -173,6 +171,7 @@ class IrModuleToJsTransformer(
                 parameters += JsParameter(internalModuleName)
                 parameters += (importedJsModules + importedKotlinModules).map { JsParameter(it.internalName) }
                 with(body) {
+                    statements += JsStringLiteral("use strict").makeStmt()
                     statements.addWithComment("block: imports", importStatements + crossModuleImports)
                     statements += moduleBody
                     statements.addWithComment("block: exports", exportStatements + crossModuleExports)
@@ -221,6 +220,7 @@ class IrModuleToJsTransformer(
                 null
             }
 
+        staticContext.polyfills.addAllNeededPolyfillsTo(jsCode)
         program.accept(JsToStringGenerationVisitor(jsCode, sourceMapBuilderConsumer ?: NoOpSourceLocationConsumer))
 
         return CompilationOutputs(
@@ -284,12 +284,10 @@ class IrModuleToJsTransformer(
     }
 
     private fun generateModuleBody(modules: Iterable<IrModuleFragment>, staticContext: JsStaticContext): List<JsStatement> {
-        val statements = mutableListOf<JsStatement>().also {
-            if (!generateScriptModule) it += JsStringLiteral("use strict").makeStmt()
-            if (generateGlobalThisPolyfill) it += jsGlobalThisPolyfill()
-        }
+        val statements = mutableListOf<JsStatement>()
 
         val preDeclarationBlock = JsGlobalBlock()
+
         val postDeclarationBlock = JsGlobalBlock()
 
         statements.addWithComment("block: pre-declaration", preDeclarationBlock)
diff --git a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/transformers/irToJs/JsPolyfillsVisitor.kt b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/transformers/irToJs/JsPolyfillsVisitor.kt
new file mode 100644
index 00000000000..e8f574a3ef8
--- /dev/null
+++ b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/transformers/irToJs/JsPolyfillsVisitor.kt
@@ -0,0 +1,28 @@
+/*
+ * 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.ir.backend.js.transformers.irToJs
+
+import org.jetbrains.kotlin.ir.declarations.IrDeclaration
+import org.jetbrains.kotlin.ir.backend.js.utils.getJsNativeImplementation
+import org.jetbrains.kotlin.ir.util.isEffectivelyExternal
+import org.jetbrains.kotlin.js.util.TextOutput
+
+class JsPolyfillsVisitor {
+    private val polyfills = mutableSetOf<String>()
+
+    fun visitDeclaration(declaration: IrDeclaration) {
+        if (!declaration.isEffectivelyExternal()) return
+        val implementation = declaration.getJsNativeImplementation() ?: return
+        polyfills.add(implementation)
+    }
+
+    fun addAllNeededPolyfillsTo(output: TextOutput) {
+        if (polyfills.isEmpty()) return
+        output.print("// region block: polyfills")
+        output.print(polyfills.joinToString("\n"))
+        output.print("// endregion\n")
+    }
+}
\ No newline at end of file
diff --git a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/transformers/irToJs/jsAstUtils.kt b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/transformers/irToJs/jsAstUtils.kt
index 014bd83b691..50f8535d522 100644
--- a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/transformers/irToJs/jsAstUtils.kt
+++ b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/transformers/irToJs/jsAstUtils.kt
@@ -45,25 +45,6 @@ fun <T : JsNode> IrWhen.toJsNode(
         }
     }
 
-// https://mathiasbynens.be/notes/globalthis
-// TODO: add DCE for globalThis polyfill declaration
-fun jsGlobalThisPolyfill(): List<JsStatement> =
-    parseJsCode(
-        """
-        (function() {
-            if (typeof globalThis === 'object') return; 
-            Object.defineProperty(Object.prototype, '__magic__', {
-                get: function() {
-                    return this;
-                },
-                configurable: true
-            });
-            __magic__.globalThis = __magic__;
-            delete Object.prototype.__magic__;
-        }());
-        """.trimIndent()
-    ) ?: emptyList()
-
 fun jsElementAccess(name: String, receiver: JsExpression?): JsExpression =
     if (receiver == null || name.isValidES5Identifier()) {
         JsNameRef(JsName(name, false), receiver)
@@ -71,13 +52,6 @@ fun jsElementAccess(name: String, receiver: JsExpression?): JsExpression =
         JsArrayAccess(receiver, JsStringLiteral(name))
     }
 
-fun jsGlobalVarRef(ref: JsNameRef): JsExpression =
-    if (ref.qualifier != null || ref.ident.isValidES5Identifier()) {
-        ref
-    } else {
-        jsElementAccess(ref.ident, JsNameRef("globalThis"))
-    }
-
 fun jsAssignment(left: JsExpression, right: JsExpression) = JsBinaryOperation(JsBinaryOperator.ASG, left, right)
 
 fun prototypeOf(classNameRef: JsExpression) = JsNameRef(Namer.PROTOTYPE_NAME, classNameRef)
@@ -154,7 +128,7 @@ fun translateCall(
         ) {
             val propertyName = context.getNameForProperty(property)
             val nameRef = when (jsDispatchReceiver) {
-                null -> jsGlobalVarRef(JsNameRef(propertyName))
+                null -> JsNameRef(propertyName)
                 else -> jsElementAccess(propertyName.ident, jsDispatchReceiver)
             }
             return when (function) {
@@ -201,7 +175,7 @@ fun translateCall(
     }
 
     val ref = when (jsDispatchReceiver) {
-        null -> jsGlobalVarRef(JsNameRef(symbolName))
+        null -> JsNameRef(symbolName)
         else -> jsElementAccess(symbolName.ident, jsDispatchReceiver)
     }
 
diff --git a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/utils/AnnotationUtils.kt b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/utils/AnnotationUtils.kt
index 412009215e8..ef87cc54670 100644
--- a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/utils/AnnotationUtils.kt
+++ b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/utils/AnnotationUtils.kt
@@ -27,6 +27,7 @@ object JsAnnotations {
     val jsNativeSetter = FqName("kotlin.js.nativeSetter")
     val jsNativeInvoke = FqName("kotlin.js.nativeInvoke")
     val jsFunFqn = FqName("kotlin.js.JsFun")
+    val jsNativeImplementationFqn = FqName("kotlin.js.JsNativeImplementation")
 }
 
 @Suppress("UNCHECKED_CAST")
@@ -45,6 +46,9 @@ fun IrAnnotationContainer.getJsQualifier(): String? =
 fun IrAnnotationContainer.getJsName(): String? =
     getAnnotation(JsAnnotations.jsNameFqn)?.getSingleConstStringArgument()
 
+fun IrAnnotationContainer.getJsNativeImplementation(): String? =
+    getAnnotation(JsAnnotations.jsNativeImplementationFqn)?.getSingleConstStringArgument()
+
 fun IrAnnotationContainer.getJsFunAnnotation(): String? =
     getAnnotation(JsAnnotations.jsFunFqn)?.getSingleConstStringArgument()
 
diff --git a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/utils/JsStaticContext.kt b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/utils/JsStaticContext.kt
index 325f7bc319f..b564619a75a 100644
--- a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/utils/JsStaticContext.kt
+++ b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/utils/JsStaticContext.kt
@@ -8,6 +8,7 @@ package org.jetbrains.kotlin.ir.backend.js.utils
 import org.jetbrains.kotlin.ir.backend.js.JsIrBackendContext
 import org.jetbrains.kotlin.ir.backend.js.transformers.irToJs.JsIntrinsicTransformers
 import org.jetbrains.kotlin.ir.backend.js.transformers.irToJs.JsIrClassModel
+import org.jetbrains.kotlin.ir.backend.js.transformers.irToJs.JsPolyfillsVisitor
 import org.jetbrains.kotlin.ir.declarations.IrDeclaration
 import org.jetbrains.kotlin.ir.symbols.IrClassSymbol
 import org.jetbrains.kotlin.js.backend.ast.JsGlobalBlock
@@ -19,6 +20,7 @@ class JsStaticContext(
     private val irNamer: IrNamer,
     val globalNameScope: NameTable<IrDeclaration>,
 ) : IrNamer by irNamer {
+    val polyfills = JsPolyfillsVisitor()
     val intrinsics = JsIntrinsicTransformers(backendContext)
     val classModels = mutableMapOf<IrClassSymbol, JsIrClassModel>()
     val coroutineImplDeclaration = backendContext.ir.symbols.coroutineImpl.owner
diff --git a/js/js.translator/testData/box/escapedIdentifiers/externalEscapedTopLevel.kt b/js/js.translator/testData/box/escapedIdentifiers/externalEscapedTopLevel.kt
index bb1c6422896..8a2bf3b7e96 100644
--- a/js/js.translator/testData/box/escapedIdentifiers/externalEscapedTopLevel.kt
+++ b/js/js.translator/testData/box/escapedIdentifiers/externalEscapedTopLevel.kt
@@ -14,10 +14,12 @@ external object `+some+object%:` {
 }
 
 fun box(): String {
-    val a = js("2")
     assertEquals(42, `some+value`)
     assertEquals("%%++%%", `+some+object%:`.foo)
     assertEquals("something invalid", `@get something-invalid`())
 
+    `some+value` = 43
+    assertEquals(43, `some+value`)
+
     return "OK"
 }
\ No newline at end of file
diff --git a/libraries/stdlib/js-ir/runtime/globalThis.kt b/libraries/stdlib/js-ir/runtime/globalThis.kt
new file mode 100644
index 00000000000..cafb01ad109
--- /dev/null
+++ b/libraries/stdlib/js-ir/runtime/globalThis.kt
@@ -0,0 +1,21 @@
+/*
+ * 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 kotlin.js
+
+@JsNativeImplementation("""
+(function() {
+    if (typeof globalThis === 'object') return; 
+    Object.defineProperty(Object.prototype, '__magic__', {
+        get: function() {
+            return this;
+        },
+        configurable: true
+    });
+    __magic__.globalThis = __magic__;
+    delete Object.prototype.__magic__;
+}());
+""")
+internal external val globalThis: dynamic
\ No newline at end of file
diff --git a/libraries/stdlib/js-ir/runtime/math.kt b/libraries/stdlib/js-ir/runtime/math.kt
new file mode 100644
index 00000000000..9792710078b
--- /dev/null
+++ b/libraries/stdlib/js-ir/runtime/math.kt
@@ -0,0 +1,15 @@
+/*
+ * Copyright 2010-2018 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license
+ * that can be found in the license/LICENSE.txt file.
+ */
+@file:JsQualifier("Math")
+package kotlin.js
+
+@JsNativeImplementation("""
+if (typeof Math == "object" && Math !== null & typeof Math.imul === "undefined") {
+  Math.imul = function imul(a, b) {
+    return ((a & 0xffff0000) * (b & 0xffff) + (a & 0xffff) * (b | 0)) | 0; 
+  }
+}
+""")
+internal external fun imul(a_local: Int, b_local: Int): Int
diff --git a/libraries/stdlib/js-ir/runtime/misc.kt b/libraries/stdlib/js-ir/runtime/misc.kt
deleted file mode 100644
index 3eb9122d156..00000000000
--- a/libraries/stdlib/js-ir/runtime/misc.kt
+++ /dev/null
@@ -1,13 +0,0 @@
-/*
- * Copyright 2010-2018 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license
- * that can be found in the license/LICENSE.txt file.
- */
-
-package kotlin.js
-
-// TODO: Polyfill
-internal fun imul(a_local: Int, b_local: Int): Int {
-    val lhs = jsBitwiseAnd(a_local, js("0xffff0000")).toDouble() * jsBitwiseAnd(b_local, 0xffff).toDouble()
-    val rhs = jsBitwiseAnd(a_local, 0xffff).toDouble() * b_local.toDouble()
-    return jsBitwiseOr(lhs + rhs, 0)
-}
diff --git a/libraries/stdlib/js/src/kotlin/internalAnnotations.kt b/libraries/stdlib/js/src/kotlin/internalAnnotations.kt
new file mode 100644
index 00000000000..3cf64c2f2f2
--- /dev/null
+++ b/libraries/stdlib/js/src/kotlin/internalAnnotations.kt
@@ -0,0 +1,10 @@
+/*
+ * 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 kotlin.js
+
+@Retention(AnnotationRetention.BINARY)
+@Target(AnnotationTarget.FUNCTION, AnnotationTarget.PROPERTY)
+internal annotation class JsNativeImplementation(val implementation: String)