Do not generate safepoints for initializer functions (#4700)

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

@@ -350,6 +350,13 @@ internal class FunctionGenerationContext(val function: LLVMValueRef,
     // for example.
     var needsRuntimeInit = false
 
+    // Marks that function is not allowed to call into Kotlin runtime. For this function no safepoints, no enter/leave
+    // frames are generated.
+    // TODO: Should forbid all calls into runtime except for explicitly allowed. Also should impose the same restriction
+    //       on function being called from this one.
+    // TODO: Consider using a different abstraction than `FunctionGenerationContext`.
+    var forbidRuntime = false
+
     init {
         irFunction?.let {
             if (!irFunction.isExported()) {
@@ -1221,6 +1228,7 @@ internal class FunctionGenerationContext(val function: LLVMValueRef,
     internal fun epilogue() {
         appendingTo(prologueBb) {
             if (needsRuntimeInit) {
+                check(!forbidRuntime) { "Attempt to init runtime where runtime usage is forbidden" }
                 call(context.llvm.initRuntimeIfNeeded, emptyList())
             }
             val slots = if (needSlotsPhi)
@@ -1228,6 +1236,7 @@ internal class FunctionGenerationContext(val function: LLVMValueRef,
             else
                 kNullObjHeaderPtrPtr
             if (needSlots) {
+                check(!forbidRuntime) { "Attempt to start a frame where runtime usage is forbidden" }
                 // Zero-init slots.
                 val slotsMem = bitcast(kInt8Ptr, slots)
                 call(context.llvm.memsetFunction,
@@ -1267,7 +1276,7 @@ internal class FunctionGenerationContext(val function: LLVMValueRef,
                 returnType == voidType -> {
                     releaseVars()
                     assert(returnSlot == null)
-                    if (context.memoryModel == MemoryModel.EXPERIMENTAL)
+                    if (!forbidRuntime && context.memoryModel == MemoryModel.EXPERIMENTAL)
                         call(context.llvm.Kotlin_mm_safePointFunctionEpilogue, emptyList())
                     LLVMBuildRetVoid(builder)
                 }
@@ -1278,7 +1287,7 @@ internal class FunctionGenerationContext(val function: LLVMValueRef,
                         updateReturnRef(returnPhi, returnSlot!!)
                     }
                     releaseVars()
-                    if (context.memoryModel == MemoryModel.EXPERIMENTAL)
+                    if (!forbidRuntime && context.memoryModel == MemoryModel.EXPERIMENTAL)
                         call(context.llvm.Kotlin_mm_safePointFunctionEpilogue, emptyList())
                     LLVMBuildRet(builder, returnPhi)
                 }
@@ -1320,7 +1329,7 @@ internal class FunctionGenerationContext(val function: LLVMValueRef,
             }
 
             releaseVars()
-            if (context.memoryModel == MemoryModel.EXPERIMENTAL)
+            if (!forbidRuntime && context.memoryModel == MemoryModel.EXPERIMENTAL)
                 call(context.llvm.Kotlin_mm_safePointExceptionUnwind, emptyList())
             LLVMBuildResume(builder, landingpad)
         }
@@ -1452,6 +1461,7 @@ internal class FunctionGenerationContext(val function: LLVMValueRef,
 
     private fun releaseVars() {
         if (needSlots) {
+            check(!forbidRuntime) { "Attempt to leave a frame where runtime usage is forbidden" }
             call(context.llvm.leaveFrameFunction,
                     listOf(slotsPhi!!, Int32(vars.skipSlots).llvm, Int32(slotCount).llvm))
         }

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

@@ -513,6 +513,7 @@ internal class CodeGeneratorVisitor(val context: Context, val lifetimes: Map<IrE
         )
         LLVMSetLinkage(ctorFunction, LLVMLinkage.LLVMPrivateLinkage)
         generateFunction(codegen, ctorFunction) {
+            forbidRuntime = true
             call(context.llvm.appendToInitalizersTail, listOf(initNodePtr))
             ret(null)
         }
@@ -2413,6 +2414,7 @@ internal class CodeGeneratorVisitor(val context: Context, val lifetimes: Map<IrE
             // Runtime is linked into stdlib module only, so import runtime global from it.
             val global = codegen.importGlobal(name, value.llvmType, context.standardLlvmSymbolsOrigin)
             val initializer = generateFunction(codegen, functionType(voidType, false), "") {
+                forbidRuntime = true
                 store(value.llvm, global)
                 ret(null)
             }
@@ -2519,6 +2521,7 @@ internal class CodeGeneratorVisitor(val context: Context, val lifetimes: Map<IrE
 
     private fun appendStaticInitializers(ctorFunction: LLVMValueRef, initializers: List<LLVMValueRef>) {
         generateFunction(codegen, ctorFunction) {
+            forbidRuntime = true
             val initGuardName = ctorFunction.name.orEmpty() + "_guard"
             val initGuard = LLVMAddGlobal(context.llvmModule, int32Type, initGuardName)
             LLVMSetInitializer(initGuard, kImmZero)
@@ -2558,6 +2561,7 @@ internal class CodeGeneratorVisitor(val context: Context, val lifetimes: Map<IrE
             )
             LLVMSetLinkage(globalCtorFunction, LLVMLinkage.LLVMPrivateLinkage)
             generateFunction(codegen, globalCtorFunction) {
+                forbidRuntime = true
                 ctorFunctions.forEach {
                     call(it, emptyList(), Lifetime.IRRELEVANT,
                             exceptionHandler = ExceptionHandler.Caller, verbatim = true)

kotlin-native/backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/llvm/objcexport/ObjCExportCodeGenerator.kt

@@ -354,6 +354,7 @@ internal class ObjCExportCodeGenerator(
         if (externalGlobalInitializers.isEmpty()) return
 
         val initializer = generateFunction(codegen, functionType(voidType, false), "initObjCExportGlobals") {
+            forbidRuntime = true
             externalGlobalInitializers.forEach { (global, value) ->
                 store(value.llvm, global)
             }