Make the lazily initialized callTargets array volatile (GR-40520)

The array is initialized by copying existing CallTargets. If the field
is not volatile, then the array may be published to other threads before
all its values are fully initialized.

Author: steve-s

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/nodes/function/GeneratorExpressionNode.java

@@ -45,7 +45,7 @@
 public final class GeneratorExpressionNode extends ExpressionDefinitionNode {
     private final TruffleString name;
     private final TruffleString qualname;
-    @CompilationFinal(dimensions = 1) private RootCallTarget[] callTargets;
+    @CompilationFinal(dimensions = 1) private volatile RootCallTarget[] callTargets;
     private final FrameDescriptor frameDescriptor;
     private final GeneratorInfo generatorInfo;
 

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/nodes/generator/GeneratorFunctionRootNode.java

@@ -63,7 +63,7 @@
 
 public class GeneratorFunctionRootNode extends PClosureFunctionRootNode {
     private final RootCallTarget callTarget;
-    @CompilationFinal(dimensions = 1) private RootCallTarget[] callTargets;
+    @CompilationFinal(dimensions = 1) private volatile RootCallTarget[] callTargets;
     private final FrameDescriptor frameDescriptor;
     private final GeneratorInfo generatorInfo;
     private final ExecutionCellSlots cellSlots;