Disable backend codegen during frontend-only compilation

backend.native/cli.bc/src/org/jetbrains/kotlin/cli/bc/K2Native.kt

@@ -140,6 +140,8 @@ class K2Native : CLICompiler<K2NativeCompilerArguments>() {
                 val outputKind = CompilerOutputKind.valueOf(
                     (arguments.produce ?: "program").toUpperCase())
                 put(PRODUCE, outputKind)
+                put(METADATA_KLIB, arguments.metadataKlib)
+
                 arguments.libraryVersion ?. let { put(LIBRARY_VERSION, it) }
 
                 arguments.mainPackage ?.let{ put(ENTRY, it) }

backend.native/cli.bc/src/org/jetbrains/kotlin/cli/bc/K2NativeCompilerArguments.kt

@@ -245,6 +245,9 @@ class K2NativeCompilerArguments : CommonCompilerArguments() {
     @Argument(value="-Xallocator", valueDescription = "std | mimalloc", description = "Allocator used in runtime")
     var allocator: String = "std"
 
+    @Argument(value = "-Xmetadata-klib", description = "Produce a klib that only contains the declarations metadata")
+    var metadataKlib: Boolean = false
+
     override fun configureAnalysisFlags(collector: MessageCollector): MutableMap<AnalysisFlag<*>, Any> =
             super.configureAnalysisFlags(collector).also {
                 val useExperimental = it[AnalysisFlags.useExperimental] as List<*>

backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/KonanConfig.kt

@@ -64,6 +64,8 @@ class KonanConfig(val project: Project, val configuration: CompilerConfiguration
 
     internal val produce get() = configuration.get(KonanConfigKeys.PRODUCE)!!
 
+    internal val metadataKlib get() = configuration.get(KonanConfigKeys.METADATA_KLIB)!!
+
     internal val produceStaticFramework get() = configuration.getBoolean(KonanConfigKeys.STATIC_FRAMEWORK)
 
     internal val purgeUserLibs: Boolean

backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/KonanConfigurationKeys.kt

@@ -66,6 +66,8 @@ class KonanConfigKeys {
                 = CompilerConfigurationKey.create("memory model")
         val META_INFO: CompilerConfigurationKey<List<String>> 
                 = CompilerConfigurationKey.create("generate metadata")
+        val METADATA_KLIB: CompilerConfigurationKey<Boolean>
+                = CompilerConfigurationKey.create("metadata klib")
         val MODULE_KIND: CompilerConfigurationKey<ModuleKind> 
                 = CompilerConfigurationKey.create("module kind")
         val MODULE_NAME: CompilerConfigurationKey<String?> 

backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/ToplevelPhases.kt

@@ -267,9 +267,11 @@ internal val serializerPhase = konanUnitPhase(
             val mppKlibs = config.configuration.get(CommonConfigurationKeys.KLIB_MPP)?:false
             val descriptorTable = DescriptorTable.createDefault()
 
-            serializedIr = KonanIrModuleSerializer(
-                this, irModule!!.irBuiltins, descriptorTable, expectDescriptorToSymbol, skipExpects = !mppKlibs
-            ).serializedIrModule(irModule!!)
+            serializedIr = irModule?.let { ir ->
+                KonanIrModuleSerializer(
+                    this, ir.irBuiltins, descriptorTable, expectDescriptorToSymbol, skipExpects = !mppKlibs
+                ).serializedIrModule(ir)
+            }
 
             val serializer = KlibMetadataMonolithicSerializer(
                 this.config.configuration.languageVersionSettings,
@@ -421,6 +423,22 @@ internal val bitcodePhase = namedIrModulePhase(
                 cStubsPhase
 )
 
+private val backendCodegen = namedUnitPhase(
+        name = "Backend codegen",
+        description = "Backend code generation",
+        lower = takeFromContext<Context, Unit, IrModuleFragment> { it.irModule!! } then
+                allLoweringsPhase then // Lower current module first.
+                dependenciesLowerPhase then // Then lower all libraries in topological order.
+                                            // With that we guarantee that inline functions are unlowered while being inlined.
+                entryPointPhase then
+                bitcodePhase then
+                verifyBitcodePhase then
+                printBitcodePhase then
+                linkBitcodeDependenciesPhase then
+                bitcodeOptimizationPhase then
+                unitSink()
+)
+
 // Have to hide Context as type parameter in order to expose toplevelPhase outside of this module.
 val toplevelPhase: CompilerPhase<*, Unit, Unit> = namedUnitPhase(
         name = "Compiler",
@@ -436,16 +454,7 @@ val toplevelPhase: CompilerPhase<*, Unit, Unit> = namedUnitPhase(
                 namedUnitPhase(
                         name = "Backend",
                         description = "All backend",
-                        lower = takeFromContext<Context, Unit, IrModuleFragment> { it.irModule!! } then
-                                allLoweringsPhase then // Lower current module first.
-                                dependenciesLowerPhase then // Then lower all libraries in topological order.
-                                                            // With that we guarantee that inline functions are unlowered while being inlined.
-                                entryPointPhase then
-                                bitcodePhase then
-                                verifyBitcodePhase then
-                                printBitcodePhase then
-                                linkBitcodeDependenciesPhase then
-                                bitcodeOptimizationPhase then
+                        lower = backendCodegen then
                                 produceOutputPhase then
                                 disposeLLVMPhase then
                                 unitSink()
@@ -485,5 +494,11 @@ internal fun PhaseConfig.konanPhasesConfig(config: KonanConfig) {
         disableUnless(dcePhase, getBoolean(KonanConfigKeys.OPTIMIZATION))
         disableUnless(ghaPhase, getBoolean(KonanConfigKeys.OPTIMIZATION))
         disableUnless(verifyBitcodePhase, config.needCompilerVerification || getBoolean(KonanConfigKeys.VERIFY_BITCODE))
+
+        val isDescriptorsOnlyLibrary = config.metadataKlib == true
+        disableIf(psiToIrPhase, isDescriptorsOnlyLibrary)
+        disableIf(destroySymbolTablePhase, isDescriptorsOnlyLibrary)
+        disableIf(copyDefaultValuesToActualPhase, isDescriptorsOnlyLibrary)
+        disableIf(backendCodegen, isDescriptorsOnlyLibrary)
     }
 }

backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/llvm/BitcodePhases.kt

@@ -6,6 +6,10 @@
 package org.jetbrains.kotlin.backend.konan.llvm
 
 import llvm.*
+import org.jetbrains.kotlin.backend.common.phaser.CompilerPhase
+import org.jetbrains.kotlin.backend.common.phaser.PhaseConfig
+import org.jetbrains.kotlin.backend.common.phaser.PhaserState
+import org.jetbrains.kotlin.backend.common.phaser.namedUnitPhase
 import org.jetbrains.kotlin.backend.konan.*
 import org.jetbrains.kotlin.backend.konan.descriptors.GlobalHierarchyAnalysis
 import org.jetbrains.kotlin.backend.konan.optimizations.*
@@ -44,10 +48,14 @@ internal val createLLVMDeclarationsPhase = makeKonanModuleOpPhase(
         }
 )
 
-internal val disposeLLVMPhase = makeKonanModuleOpPhase(
+internal val disposeLLVMPhase = namedUnitPhase(
         name = "DisposeLLVM",
         description = "Dispose LLVM",
-        op = { context, _ -> context.disposeLlvm() }
+        lower = object : CompilerPhase<Context, Unit, Unit> {
+            override fun invoke(phaseConfig: PhaseConfig, phaserState: PhaserState<Unit>, context: Context, input: Unit) {
+                context.disposeLlvm()
+            }
+        }
 )
 
 internal val RTTIPhase = makeKonanModuleOpPhase(
@@ -265,10 +273,14 @@ internal val bitcodeOptimizationPhase = makeKonanModuleOpPhase(
         op = { context, _ -> runLlvmOptimizationPipeline(context) }
 )
 
-internal val produceOutputPhase = makeKonanModuleOpPhase(
+internal val produceOutputPhase = namedUnitPhase(
         name = "ProduceOutput",
         description = "Produce output",
-        op = { context, _ -> produceOutput(context) }
+        lower = object : CompilerPhase<Context, Unit, Unit> {
+            override fun invoke(phaseConfig: PhaseConfig, phaserState: PhaserState<Unit>, context: Context, input: Unit) {
+                produceOutput(context)
+            }
+        }
 )
 
 internal val verifyBitcodePhase = makeKonanModuleOpPhase(