Validate -Xbackend-threads CLI argument value

#KT-51846 Fixed

compiler/cli/cli-common/src/org/jetbrains/kotlin/cli/common/arguments/K2JVMCompilerArguments.kt

@@ -124,7 +124,7 @@ class K2JVMCompilerArguments : CommonCompilerArguments() {
                 "0 means use a thread per processor core.\n" +
                 "Default value is 1"
     )
-    var parallelBackendThreads: String by FreezableVar("1")
+    var backendThreads: String by FreezableVar("1")
 
     @Argument(value = "-Xmodule-path", valueDescription = "<path>", description = "Paths where to find Java 9+ modules")
     var javaModulePath: String? by NullableStringFreezableVar(null)
@@ -505,7 +505,7 @@ Also sets `-jvm-target` value equal to the selected JDK version"""
 
     @Argument(
         value = "-Xlink-via-signatures",
-        description = "Link JVM IR symbols via signatures, instead of descriptors. \n" +
+        description = "Link JVM IR symbols via signatures, instead of descriptors.\n" +
                 "This mode is slower, but can be useful in troubleshooting problems with the JVM IR backend"
     )
     var linkViaSignatures: Boolean by FreezableVar(false)

compiler/cli/src/org/jetbrains/kotlin/cli/jvm/jvmArguments.kt

@@ -321,11 +321,27 @@ fun CompilerConfiguration.configureAdvancedJvmOptions(arguments: K2JVMCompilerAr
 
     arguments.declarationsOutputPath?.let { put(JVMConfigurationKeys.DECLARATIONS_JSON_PATH, it) }
 
-    val nThreadsRaw = arguments.parallelBackendThreads.toIntOrNull() ?: 1
+    val nThreadsRaw = parseBackendThreads(arguments.backendThreads, messageCollector)
     val nThreads = if (nThreadsRaw == 0) Runtime.getRuntime().availableProcessors() else nThreadsRaw
+    if (nThreads > 1) {
+        messageCollector.report(LOGGING, "Running backend in parallel with $nThreads threads")
+    }
     put(CommonConfigurationKeys.PARALLEL_BACKEND_THREADS, nThreads)
 }
 
+private fun parseBackendThreads(stringValue: String, messageCollector: MessageCollector): Int {
+    val value = stringValue.toIntOrNull()
+    if (value == null) {
+        messageCollector.report(ERROR, "Cannot parse -Xbackend-threads value: \"$stringValue\". Please use an integer number")
+        return 1
+    }
+    if (value < 0) {
+        messageCollector.report(ERROR, "-Xbackend-threads value cannot be negative")
+        return 1
+    }
+    return value
+}
+
 fun CompilerConfiguration.configureKlibPaths(arguments: K2JVMCompilerArguments) {
     val libraries = arguments.klibLibraries ?: return
     assert(arguments.useIR && !arguments.useOldBackend) { "Klib libraries can only be used with IR backend" }

compiler/testData/cli/jvm/extraHelp.out

@@ -16,6 +16,9 @@ where advanced options include:
                              -Xassertions=jvm:            enable, depend on jvm assertion settings;
                              -Xassertions=legacy:         calculate condition on each call, check depends on jvm assertion settings in the kotlin package;
                              default: legacy
+  -Xbackend-threads=<N>      When using the IR backend, run lowerings by file in N parallel threads.
+                             0 means use a thread per processor core.
+                             Default value is 1
   -Xbuild-file=<path>        Path to the .xml build file to compile
   -Xcompile-java             Reuse javac analysis and compile Java source files
   -Xdump-declarations-to=<path> Path to JSON file to dump Java to Kotlin declaration mappings
@@ -99,9 +102,6 @@ where advanced options include:
                                * ignore
                                * strict
                                * warn (report a warning)
-  -Xbackend-threads=<N>      When using the IR backend, run lowerings by file in N parallel threads.
-                             0 means use a thread per processor core.
-                             Default value is 1
   -Xprofile=<profilerPath:command:outputDir>
                              Debug option: Run compiler with async profiler and save snapshots to `outputDir`; `command` is passed to async-profiler on start.
                              `profilerPath` is a path to libasyncProfiler.so; async-profiler.jar should be on the compiler classpath.

compiler/testData/cli/jvm/kt51846_backendThreadsValidation1.args

@@ -0,0 +1,4 @@
+$TESTDATA_DIR$/simple.kt
+-d
+$TEMP_DIR$
+-Xbackend-threads=2

compiler/testData/cli/jvm/kt51846_backendThreadsValidation1.out

@@ -0,0 +1 @@
+OK

compiler/testData/cli/jvm/kt51846_backendThreadsValidation2.args

@@ -0,0 +1,4 @@
+$TESTDATA_DIR$/simple.kt
+-d
+$TEMP_DIR$
+-Xbackend-threads=abcd

compiler/testData/cli/jvm/kt51846_backendThreadsValidation2.out

@@ -0,0 +1,2 @@
+error: cannot parse -Xbackend-threads value: "abcd". Please use an integer number
+COMPILATION_ERROR

compiler/testData/cli/jvm/kt51846_backendThreadsValidation3.args

@@ -0,0 +1,4 @@
+$TESTDATA_DIR$/simple.kt
+-d
+$TEMP_DIR$
+-Xbackend-threads=-3

compiler/testData/cli/jvm/kt51846_backendThreadsValidation3.out

@@ -0,0 +1,2 @@
+error: -Xbackend-threads value cannot be negative
+COMPILATION_ERROR

compiler/tests-gen/org/jetbrains/kotlin/cli/CliTestGenerated.java

@@ -689,6 +689,21 @@ public class CliTestGenerated extends AbstractCliTest {
             runTest("compiler/testData/cli/jvm/kt49209.args");
         }
 
+        @TestMetadata("kt51846_backendThreadsValidation1.args")
+        public void testKt51846_backendThreadsValidation1() throws Exception {
+            runTest("compiler/testData/cli/jvm/kt51846_backendThreadsValidation1.args");
+        }
+
+        @TestMetadata("kt51846_backendThreadsValidation2.args")
+        public void testKt51846_backendThreadsValidation2() throws Exception {
+            runTest("compiler/testData/cli/jvm/kt51846_backendThreadsValidation2.args");
+        }
+
+        @TestMetadata("kt51846_backendThreadsValidation3.args")
+        public void testKt51846_backendThreadsValidation3() throws Exception {
+            runTest("compiler/testData/cli/jvm/kt51846_backendThreadsValidation3.args");
+        }
+
         @TestMetadata("languageVersion.args")
         public void testLanguageVersion() throws Exception {
             runTest("compiler/testData/cli/jvm/languageVersion.args");