JVM: erase conditional suspension markers from inline-only functions

Otherwise, the generated bytecode is unnecessarily suboptimal in some
(arguably weird) cases.

In the JVM backend, this was an accidental regression in #3260, as I had
not noticed that effectively inline-only functions were handled by a
separate branch in FunctionCodegen. In JVM_IR, I'm pretty sure the
redundant markers have always been there as `isSuspensionPoint` in
ExpressionCodegen never checked for effectively-inline-only-ness.

compiler/backend/src/org/jetbrains/kotlin/codegen/FunctionCodegen.java

@@ -80,7 +80,6 @@ import static org.jetbrains.kotlin.descriptors.ModalityKt.isOverridable;
 import static org.jetbrains.kotlin.load.java.JvmAbi.LOCAL_VARIABLE_INLINE_ARGUMENT_SYNTHETIC_LINE_NUMBER;
 import static org.jetbrains.kotlin.resolve.DescriptorToSourceUtils.getSourceFromDescriptor;
 import static org.jetbrains.kotlin.resolve.DescriptorUtils.*;
-import static org.jetbrains.kotlin.resolve.inline.InlineOnlyKt.isEffectivelyInlineOnly;
 import static org.jetbrains.kotlin.resolve.inline.InlineOnlyKt.isInlineOnlyPrivateInBytecode;
 import static org.jetbrains.kotlin.resolve.jvm.AsmTypes.OBJECT_TYPE;
 import static org.jetbrains.kotlin.resolve.jvm.InlineClassManglingRulesKt.shouldHideConstructorDueToInlineClassTypeValueParameters;
@@ -124,18 +123,14 @@ public class FunctionCodegen {
         if (owner.getContextKind() != OwnerKind.DEFAULT_IMPLS || function.hasBody()) {
             FunctionGenerationStrategy strategy;
             if (functionDescriptor.isSuspend()) {
-                if (isEffectivelyInlineOnly(functionDescriptor)) {
+                strategy = new SuspendFunctionGenerationStrategy(
-                    strategy = new FunctionGenerationStrategy.FunctionDefault(state, function);
+                        state,
-                } else {
+                        CoroutineCodegenUtilKt.<FunctionDescriptor>unwrapInitialDescriptorForSuspendFunction(functionDescriptor),
-                    strategy = new SuspendFunctionGenerationStrategy(
+                        function,
-                            state,
+                        v.getThisName(),
-                            CoroutineCodegenUtilKt.<FunctionDescriptor>unwrapInitialDescriptorForSuspendFunction(functionDescriptor),
+                        state.getConstructorCallNormalizationMode(),
-                            function,
+                        this
-                            v.getThisName(),
+                );
-                            state.getConstructorCallNormalizationMode(),
-                            this
-                    );
-                }
             } else {
                 strategy = new FunctionGenerationStrategy.FunctionDefault(state, function);
             }

compiler/backend/src/org/jetbrains/kotlin/codegen/coroutines/SuspendFunctionGenerationStrategy.kt

@@ -19,6 +19,7 @@ import org.jetbrains.kotlin.descriptors.ClassDescriptor
 import org.jetbrains.kotlin.descriptors.FunctionDescriptor
 import org.jetbrains.kotlin.psi.KtFunction
 import org.jetbrains.kotlin.psi.psiUtil.getElementTextWithContext
+import org.jetbrains.kotlin.resolve.inline.isEffectivelyInlineOnly
 import org.jetbrains.kotlin.resolve.jvm.diagnostics.JvmDeclarationOrigin
 import org.jetbrains.kotlin.resolve.jvm.diagnostics.OtherOrigin
 import org.jetbrains.kotlin.resolve.jvm.jvmSignature.JvmMethodSignature
@@ -56,6 +57,9 @@ class SuspendFunctionGenerationStrategy(
     override fun wrapMethodVisitor(mv: MethodVisitor, access: Int, name: String, desc: String): MethodVisitor {
         if (access and Opcodes.ACC_ABSTRACT != 0) return mv
 
+        if (originalSuspendDescriptor.isEffectivelyInlineOnly()) {
+            return SuspendForInlineOnlyMethodVisitor(mv, access, name, desc)
+        }
         val stateMachineBuilder = createStateMachineBuilder(mv, access, name, desc)
         if (originalSuspendDescriptor.isInline) {
             return SuspendForInlineCopyingMethodVisitor(stateMachineBuilder, access, name, desc, functionCodegen::newMethod, keepAccess = false)
@@ -156,6 +160,13 @@ class SuspendFunctionGenerationStrategy(
     }
 }
 
+private class SuspendForInlineOnlyMethodVisitor(delegate: MethodVisitor, access: Int, name: String, desc: String) :
+    TransformationMethodVisitor(delegate, access, name, desc, null, null) {
+    override fun performTransformations(methodNode: MethodNode) {
+        methodNode.preprocessSuspendMarkers(forInline = true, keepFakeContinuation = false)
+    }
+}
+
 // For named suspend function we generate two methods:
 // 1) to use as noinline function, which have state machine
 // 2) to use from inliner: private one without state machine

compiler/ir/backend.jvm/src/org/jetbrains/kotlin/backend/jvm/codegen/ClassCodegen.kt

@@ -355,7 +355,7 @@ class ClassCodegen private constructor(
 
         val (node, smap) = generateMethodNode(method)
         node.preprocessSuspendMarkers(
-            method.origin == JvmLoweredDeclarationOrigin.FOR_INLINE_STATE_MACHINE_TEMPLATE,
+            method.origin == JvmLoweredDeclarationOrigin.FOR_INLINE_STATE_MACHINE_TEMPLATE || method.isEffectivelyInlineOnly(),
             method.origin == JvmLoweredDeclarationOrigin.FOR_INLINE_STATE_MACHINE_TEMPLATE_CAPTURES_CROSSINLINE
         )
         val mv = with(node) { visitor.newMethod(method.OtherOrigin, access, name, desc, signature, exceptions.toTypedArray()) }

compiler/testData/codegen/bytecodeText/coroutines/effectivelyInlineOnly.kt

@@ -0,0 +1,4 @@
+// WITH_COROUTINES
+// TREAT_AS_ONE_FILE
+inline suspend fun <reified T> f(x: suspend () -> T) = x()
+// 0 InlineMarker

compiler/tests/org/jetbrains/kotlin/codegen/BytecodeTextTestGenerated.java

@@ -1391,6 +1391,11 @@ public class BytecodeTextTestGenerated extends AbstractBytecodeTextTest {
             runTest("compiler/testData/codegen/bytecodeText/coroutines/doNotReassignContinuation.kt");
         }
 
+        @TestMetadata("effectivelyInlineOnly.kt")
+        public void testEffectivelyInlineOnly() throws Exception {
+            runTest("compiler/testData/codegen/bytecodeText/coroutines/effectivelyInlineOnly.kt");
+        }
+
         @TestMetadata("nonLocalReturn.kt")
         public void testNonLocalReturn() throws Exception {
             runTest("compiler/testData/codegen/bytecodeText/coroutines/nonLocalReturn.kt");

compiler/tests/org/jetbrains/kotlin/codegen/ir/IrBytecodeTextTestGenerated.java

@@ -1401,6 +1401,11 @@ public class IrBytecodeTextTestGenerated extends AbstractIrBytecodeTextTest {
             runTest("compiler/testData/codegen/bytecodeText/coroutines/doNotReassignContinuation.kt");
         }
 
+        @TestMetadata("effectivelyInlineOnly.kt")
+        public void testEffectivelyInlineOnly() throws Exception {
+            runTest("compiler/testData/codegen/bytecodeText/coroutines/effectivelyInlineOnly.kt");
+        }
+
         @TestMetadata("nonLocalReturn.kt")
         public void testNonLocalReturn() throws Exception {
             runTest("compiler/testData/codegen/bytecodeText/coroutines/nonLocalReturn.kt");