IR: only worry about threads in JvmIrSignatureDescriptor

General IdSignatureDescriptor is used from other backends, which have no
multi-threaded backend for now and do not need to carry the associated
runtime costs.

So IdSignatureDescriptor keeps the thread-unsafe caching of signature
builder.

compiler/ir/serialization.jvm/src/org/jetbrains/kotlin/backend/jvm/serialization/JvmIdSignatureDescriptor.kt

@@ -8,6 +8,7 @@ package org.jetbrains.kotlin.backend.jvm.serialization
 import org.jetbrains.kotlin.backend.common.serialization.signature.IdSignatureDescriptor
 import org.jetbrains.kotlin.descriptors.*
 import org.jetbrains.kotlin.incremental.components.NoLookupLocation
+import org.jetbrains.kotlin.ir.util.IdSignature
 import org.jetbrains.kotlin.ir.util.KotlinMangler
 import org.jetbrains.kotlin.load.java.descriptors.JavaForKotlinOverridePropertyDescriptor
 import org.jetbrains.kotlin.resolve.descriptorUtil.fqNameUnsafe
@@ -95,4 +96,18 @@ class JvmIdSignatureDescriptor(private val mangler: KotlinMangler.DescriptorMang
     }
 
     override fun createSignatureBuilder(): DescriptorBasedSignatureBuilder = JvmDescriptorBasedSignatureBuilder(mangler)
+
+    /* In multi-threaded environment, we cannot afford to cache a signature builder, as in IdSignatureBuilder. */
+
+    override fun composeSignature(descriptor: DeclarationDescriptor): IdSignature? {
+        return if (mangler.run { descriptor.isExported() }) {
+            createSignatureBuilder().buildSignature(descriptor)
+        } else null
+    }
+
+    override fun composeEnumEntrySignature(descriptor: ClassDescriptor): IdSignature? {
+        return if (mangler.run { descriptor.isExportEnumEntry() }) {
+            createSignatureBuilder().buildSignature(descriptor)
+        } else null
+    }
 }