Ensure that code base is determined after initializing heap base.

Author: peter-hofer

substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/graal/nodes/ReadReservedRegisterFixedNode.java

@@ -36,6 +36,7 @@
 import jdk.graal.compiler.nodes.spi.NodeLIRBuilderTool;
 import jdk.vm.ci.code.Register;
 
+/** @see ReadReservedRegisterFloatingNode */
 @NodeInfo(cycles = NodeCycles.CYCLES_0, size = NodeSize.SIZE_0)
 public final class ReadReservedRegisterFixedNode extends FixedWithNextNode implements LIRLowerable {
     public static final NodeClass<ReadReservedRegisterFixedNode> TYPE = NodeClass.create(ReadReservedRegisterFixedNode.class);

substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/graal/nodes/ReadReservedRegisterFloatingNode.java

@@ -25,6 +25,8 @@
 package com.oracle.svm.core.graal.nodes;
 
 import com.oracle.svm.core.FrameAccess;
+import com.oracle.svm.core.ReservedRegisters;
+import com.oracle.svm.core.graal.snippets.CEntryPointSnippets;
 
 import jdk.graal.compiler.core.common.LIRKind;
 import jdk.graal.compiler.graph.NodeClass;
@@ -36,6 +38,22 @@
 import jdk.graal.compiler.nodes.spi.NodeLIRBuilderTool;
 import jdk.vm.ci.code.Register;
 
+/**
+ * A floating node to read a reserved register, which is more efficient because it allows value
+ * numbering of multiple accesses, including floating nodes that use it as an input. This is safe
+ * without explicit dependencies because reserved registers generally contain the same value
+ * throughout a method's execution.
+ *
+ * However, these floating reads are also used in the methods that initialize reserved registers
+ * when entering an isolate (see {@link CEntryPointSnippets}). We carefully use separate methods and
+ * prevent inlining to avoid that the compiler can move register reads before their writes.
+ *
+ * Also, these nodes must not be used for deoptimization target methods because there is no proxying
+ * at deoptimization entry points for them, so deoptimization would not restore the values.
+ *
+ * @see ReservedRegisters
+ * @see ReadReservedRegisterFixedNode
+ */
 @NodeInfo(cycles = NodeCycles.CYCLES_0, size = NodeSize.SIZE_0)
 public final class ReadReservedRegisterFloatingNode extends FloatingNode implements LIRLowerable {
     public static final NodeClass<ReadReservedRegisterFloatingNode> TYPE = NodeClass.create(ReadReservedRegisterFloatingNode.class);

substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/graal/snippets/CEntryPointSnippets.java

@@ -163,9 +163,10 @@ public final class CEntryPointSnippets extends SubstrateTemplates implements Sni
     public static final SubstrateForeignCallDescriptor FAIL_FATALLY = SnippetRuntime.findForeignCall(CEntryPointSnippets.class, "failFatally", HAS_SIDE_EFFECT, LocationIdentity.any());
     public static final SubstrateForeignCallDescriptor VERIFY_ISOLATE_THREAD = SnippetRuntime.findForeignCall(CEntryPointSnippets.class, "verifyIsolateThread", HAS_SIDE_EFFECT,
                     LocationIdentity.any());
+    public static final SubstrateForeignCallDescriptor INIT_CODE_BASE = SnippetRuntime.findForeignCall(CEntryPointSnippets.class, "initCodeBase", HAS_SIDE_EFFECT, LocationIdentity.any());
 
     public static final SubstrateForeignCallDescriptor[] FOREIGN_CALLS = {CREATE_ISOLATE, INITIALIZE_ISOLATE, ATTACH_THREAD, ENSURE_JAVA_THREAD, ENTER_BY_ISOLATE,
-                    DETACH_CURRENT_THREAD, REPORT_EXCEPTION, TEAR_DOWN_ISOLATE, IS_ATTACHED, FAIL_FATALLY, VERIFY_ISOLATE_THREAD};
+                    DETACH_CURRENT_THREAD, REPORT_EXCEPTION, TEAR_DOWN_ISOLATE, IS_ATTACHED, FAIL_FATALLY, VERIFY_ISOLATE_THREAD, INIT_CODE_BASE};
 
     @NodeIntrinsic(value = ForeignCallNode.class)
     public static native int runtimeCall(@ConstantNodeParameter ForeignCallDescriptor descriptor, CEntryPointCreateIsolateParameters parameters);
@@ -185,9 +186,6 @@ public final class CEntryPointSnippets extends SubstrateTemplates implements Sni
     @NodeIntrinsic(value = ForeignCallNode.class)
     public static native int runtimeCallInitializeIsolate(@ConstantNodeParameter ForeignCallDescriptor descriptor, CEntryPointCreateIsolateParameters parameters);
 
-    @NodeIntrinsic(value = ForeignCallNode.class)
-    public static native int runtimeCallTearDownIsolate(@ConstantNodeParameter ForeignCallDescriptor descriptor);
-
     @NodeIntrinsic(value = ForeignCallNode.class)
     public static native boolean runtimeCallIsAttached(@ConstantNodeParameter ForeignCallDescriptor descriptor, Isolate isolate);
 
@@ -197,6 +195,9 @@ public final class CEntryPointSnippets extends SubstrateTemplates implements Sni
     @NodeIntrinsic(value = ForeignCallNode.class)
     public static native void runtimeCallFailFatally(@ConstantNodeParameter ForeignCallDescriptor descriptor, int code, CCharPointer message);
 
+    @NodeIntrinsic(value = ForeignCallNode.class)
+    public static native void runtimeCallInitCodeBase(@ConstantNodeParameter ForeignCallDescriptor descriptor);
+
     @Fold
     static boolean hasHeapBase() {
         return ImageSingletons.lookup(CompressEncoding.class).hasBase();
@@ -210,8 +211,13 @@ private static void setHeapBase(PointerBase heapBase) {
         }
     }
 
-    @Uninterruptible(reason = CALLED_FROM_UNINTERRUPTIBLE_CODE)
-    @NeverInline("Heap base register is set in caller, prevent reads from floating before that.")
+    /**
+     * Initializes the code base register, which accesses the heap using the heap base register. To
+     * prevent the compiler from moving reads from this method to before the heap base register is
+     * initialized in a caller, this method is a foreign call target that does not get inlined.
+     */
+    @SubstrateForeignCallTarget(stubCallingConvention = false)
+    @Uninterruptible(reason = "Thread state not yet set up.")
     private static void initCodeBase() {
         CodePointer codeBase;
         if (ImageLayerBuildingSupport.buildingImageLayer()) {
@@ -243,7 +249,7 @@ public static void earlyInitHeapBase(PointerBase heapBase) {
     public static void initBaseRegisters(PointerBase heapBase) {
         setHeapBase(heapBase);
         if (SubstrateOptions.useRelativeCodePointers()) {
-            initCodeBase();
+            runtimeCallInitCodeBase(INIT_CODE_BASE);
         }
     }
 
@@ -683,7 +689,7 @@ private static int detachCurrentThread() {
 
     @Snippet(allowMissingProbabilities = true)
     public static int tearDownIsolateSnippet() {
-        return runtimeCallTearDownIsolate(TEAR_DOWN_ISOLATE);
+        return runtimeCall(TEAR_DOWN_ISOLATE);
     }
 
     @SubstrateForeignCallTarget(stubCallingConvention = false)