From 88a98a3310327d6167b21641de9db8261a926936 Mon Sep 17 00:00:00 2001
From: Josef Eisl <josef.eisl@oracle.com>
Date: Wed, 17 May 2023 11:34:30 +0200
Subject: [PATCH 01/16] svm: add static FrameInfoQueryResult#getSourceReference

---
 .../src/com/oracle/svm/core/code/FrameInfoQueryResult.java    | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/code/FrameInfoQueryResult.java b/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/code/FrameInfoQueryResult.java
index bb375834d5a2..bc187e6ed7c4 100644
--- a/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/code/FrameInfoQueryResult.java
+++ b/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/code/FrameInfoQueryResult.java
@@ -353,6 +353,10 @@ public int getSourceLineNumber() {
      * Returns the name and source code location of the method.
      */
     public StackTraceElement getSourceReference() {
+        return getSourceReference(sourceClass, sourceMethodName, sourceLineNumber);
+    }
+
+    public static StackTraceElement getSourceReference(Class<?> sourceClass, String sourceMethodName, int sourceLineNumber) {
         if (sourceClass == null) {
             return new StackTraceElement("", sourceMethodName, null, sourceLineNumber);
         }

From 25c4cf269cf517c2ff99b8d47cea92ea2aea842a Mon Sep 17 00:00:00 2001
From: Josef Eisl <josef.eisl@oracle.com>
Date: Wed, 17 May 2023 15:58:58 +0200
Subject: [PATCH 02/16] svm: no longer pass FrameInfoQueryResult to
 BacktraceDecoder#processSourceReference

---
 .../src/com/oracle/svm/core/jdk/BacktraceDecoder.java     | 6 +++---
 .../src/com/oracle/svm/core/jdk/StackTraceUtils.java      | 4 ++--
 .../src/com/oracle/svm/core/log/RealLog.java              | 8 +++++---
 3 files changed, 10 insertions(+), 8 deletions(-)

diff --git a/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jdk/BacktraceDecoder.java b/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jdk/BacktraceDecoder.java
index 91cffd6f4f88..4ca5a16a0115 100644
--- a/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jdk/BacktraceDecoder.java
+++ b/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jdk/BacktraceDecoder.java
@@ -44,7 +44,7 @@ public abstract class BacktraceDecoder {
      * 
      * @param backtrace internal backtrace stored in {@link Target_java_lang_Throwable#backtrace}
      * @param maxFramesProcessed the maximum number of frames that should be
-     *            {@linkplain #processFrameInfo processed}
+     *            {@linkplain #processSourceReference processed}
      * @param maxFramesDecode the maximum number of frames that should be decoded (0 means all)
      * @return the number of decoded frames
      */
@@ -106,7 +106,7 @@ private int visitFrame(CodePointer ip, CodeInfo tetheredCodeInfo, int oldFramesD
                 continue;
             }
             if (framesDecoded < maxFramesProcessed) {
-                processFrameInfo(frameInfo);
+                processSourceReference(frameInfo.getSourceClass(), frameInfo.getSourceMethodName(), frameInfo.getSourceLineNumber());
             }
             framesDecoded++;
             if (framesDecoded == maxFramesDecode) {
@@ -117,5 +117,5 @@ private int visitFrame(CodePointer ip, CodeInfo tetheredCodeInfo, int oldFramesD
     }
 
     @RestrictHeapAccess(access = RestrictHeapAccess.Access.UNRESTRICTED, reason = "Some implementations allocate.")
-    protected abstract void processFrameInfo(FrameInfoQueryResult frameInfo);
+    protected abstract void processSourceReference(Class<?> sourceClass, String sourceMethodName, int sourceLineNumber);
 }
diff --git a/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jdk/StackTraceUtils.java b/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jdk/StackTraceUtils.java
index 051107df4cf6..11dbfed59b65 100644
--- a/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jdk/StackTraceUtils.java
+++ b/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jdk/StackTraceUtils.java
@@ -369,8 +369,8 @@ static StackTraceElement[] build(Object backtrace) {
     private final ArrayList<StackTraceElement> trace = new ArrayList<>();
 
     @Override
-    protected void processFrameInfo(FrameInfoQueryResult frameInfo) {
-        StackTraceElement sourceReference = frameInfo.getSourceReference();
+    protected void processSourceReference(Class<?> sourceClass, String sourceMethodName, int sourceLineNumber) {
+        StackTraceElement sourceReference = FrameInfoQueryResult.getSourceReference(sourceClass, sourceMethodName, sourceLineNumber);
         trace.add(sourceReference);
     }
 }
diff --git a/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/log/RealLog.java b/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/log/RealLog.java
index b99fce5d4e8f..8bd06abc4601 100644
--- a/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/log/RealLog.java
+++ b/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/log/RealLog.java
@@ -42,10 +42,10 @@
 import com.oracle.svm.core.SubstrateOptions;
 import com.oracle.svm.core.SubstrateUtil;
 import com.oracle.svm.core.c.NonmovableArrays;
-import com.oracle.svm.core.code.FrameInfoQueryResult;
 import com.oracle.svm.core.graal.stackvalue.UnsafeStackValue;
 import com.oracle.svm.core.heap.Heap;
 import com.oracle.svm.core.heap.RestrictHeapAccess;
+import com.oracle.svm.core.hub.DynamicHub;
 import com.oracle.svm.core.jdk.BacktraceDecoder;
 import com.oracle.svm.core.jdk.JDKUtils;
 import com.oracle.svm.core.locks.VMMutex;
@@ -701,8 +701,10 @@ protected final int printBacktrace(Object backtrace, int maxFramesProcessed) {
 
         @Override
         @RestrictHeapAccess(access = RestrictHeapAccess.Access.NO_ALLOCATION, reason = "Must not allocate when logging.")
-        protected void processFrameInfo(FrameInfoQueryResult frameInfo) {
-            printJavaFrame(frameInfo.getSourceClassName(), frameInfo.getSourceMethodName(), frameInfo.getSourceFileName(), frameInfo.getSourceLineNumber());
+        protected void processSourceReference(Class<?> sourceClass, String sourceMethodName, int sourceLineNumber) {
+            String sourceClassName = sourceClass != null ? sourceClass.getName() : "";
+            String sourceFileName = sourceClass != null ? DynamicHub.fromClass(sourceClass).getSourceFileName() : null;
+            printJavaFrame(sourceClassName, sourceMethodName, sourceFileName, sourceLineNumber);
         }
     }
 }

From ee38749424c90c1c75a5d31759ef191ffac3accc Mon Sep 17 00:00:00 2001
From: Josef Eisl <josef.eisl@oracle.com>
Date: Wed, 17 May 2023 17:49:03 +0200
Subject: [PATCH 03/16] svm: support storing encoded source reference
 Throwable#backtrace

---
 .../oracle/svm/core/jdk/BacktraceDecoder.java |  33 ++-
 .../oracle/svm/core/jdk/StackTraceUtils.java  | 228 +++++++++++++++---
 2 files changed, 225 insertions(+), 36 deletions(-)

diff --git a/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jdk/BacktraceDecoder.java b/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jdk/BacktraceDecoder.java
index 4ca5a16a0115..20fec016f433 100644
--- a/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jdk/BacktraceDecoder.java
+++ b/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jdk/BacktraceDecoder.java
@@ -37,6 +37,10 @@
 import com.oracle.svm.core.heap.RestrictHeapAccess;
 import com.oracle.svm.core.util.VMError;
 
+/**
+ * Decoder for backtraces computed by {@link BacktraceVisitor} and stored in
+ * {@link Target_java_lang_Throwable#backtrace}.
+ */
 public abstract class BacktraceDecoder {
 
     /**
@@ -53,12 +57,20 @@ protected final int visitBacktrace(Object backtrace, int maxFramesProcessed, int
         int framesDecoded = 0;
         if (backtrace != null) {
             final long[] trace = (long[]) backtrace;
-            for (long address : trace) {
-                if (address == 0) {
-                    break;
+            int backtraceIndex = 0;
+            while (backtraceIndex < trace.length && trace[backtraceIndex] != 0) {
+                long entry = trace[backtraceIndex];
+                if (BacktraceVisitor.isSourceReference(entry)) {
+                    /* Entry is an encoded source reference. */
+                    VMError.guarantee(backtraceIndex + BacktraceVisitor.MAX_ENTRIES_PER_FRAME <= trace.length, "Truncated backtrace array");
+                    backtraceIndex += visitSourceReference(maxFramesProcessed, framesDecoded, trace, backtraceIndex);
+                    framesDecoded++;
+                } else {
+                    /* Entry is a raw code pointer. */
+                    CodePointer ip = WordFactory.pointer(entry);
+                    framesDecoded = visitCodePointer(ip, framesDecoded, maxFramesProcessed, maxFramesDecodeLimit);
+                    backtraceIndex++;
                 }
-                CodePointer ip = WordFactory.pointer(address);
-                framesDecoded = visitCodePointer(ip, framesDecoded, maxFramesProcessed, maxFramesDecodeLimit);
                 if (framesDecoded == maxFramesDecodeLimit) {
                     break;
                 }
@@ -67,6 +79,17 @@ protected final int visitBacktrace(Object backtrace, int maxFramesProcessed, int
         return framesDecoded - maxFramesProcessed;
     }
 
+    private int visitSourceReference(int maxFramesProcessed, int framesDecoded, long[] trace, int backtraceIndex) {
+        int sourceLineNumber = BacktraceVisitor.readSourceLineNumber(trace, backtraceIndex);
+        Class<?> sourceClass = BacktraceVisitor.readSourceClass(trace, backtraceIndex);
+        String sourceMethodName = BacktraceVisitor.readSourceMethodName(trace, backtraceIndex);
+
+        if (framesDecoded < maxFramesProcessed) {
+            processSourceReference(sourceClass, sourceMethodName, sourceLineNumber);
+        }
+        return BacktraceVisitor.MAX_ENTRIES_PER_FRAME;
+    }
+
     @Uninterruptible(reason = "Prevent the GC from freeing the CodeInfo object.")
     private int visitCodePointer(CodePointer ip, int oldFramesDecoded, int maxFramesProcessed, int maxFramesDecode) {
         int framesDecoded = oldFramesDecoded;
diff --git a/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jdk/StackTraceUtils.java b/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jdk/StackTraceUtils.java
index 11dbfed59b65..902bb396b675 100644
--- a/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jdk/StackTraceUtils.java
+++ b/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jdk/StackTraceUtils.java
@@ -32,22 +32,26 @@
 import java.util.ArrayList;
 import java.util.Arrays;
 
+import org.graalvm.compiler.api.replacements.Fold;
+import org.graalvm.compiler.word.Word;
 import org.graalvm.nativeimage.AnnotationAccess;
 import org.graalvm.nativeimage.IsolateThread;
 import org.graalvm.nativeimage.c.function.CodePointer;
 import org.graalvm.word.Pointer;
+import org.graalvm.word.UnsignedWord;
 import org.graalvm.word.WordFactory;
 
 import com.oracle.svm.core.NeverInline;
 import com.oracle.svm.core.SubstrateOptions;
 import com.oracle.svm.core.SubstrateUtil;
-import com.oracle.svm.core.Uninterruptible;
 import com.oracle.svm.core.code.CodeInfo;
 import com.oracle.svm.core.code.CodeInfoAccess;
+import com.oracle.svm.core.code.CodeInfoQueryResult;
 import com.oracle.svm.core.code.CodeInfoTable;
 import com.oracle.svm.core.code.FrameInfoQueryResult;
-import com.oracle.svm.core.code.UntetheredCodeInfo;
 import com.oracle.svm.core.deopt.DeoptimizedFrame;
+import com.oracle.svm.core.heap.Heap;
+import com.oracle.svm.core.heap.ReferenceAccess;
 import com.oracle.svm.core.heap.VMOperationInfos;
 import com.oracle.svm.core.hub.DynamicHub;
 import com.oracle.svm.core.snippets.KnownIntrinsics;
@@ -259,7 +263,16 @@ protected void operate() {
  */
 final class BacktraceVisitor extends StackFrameVisitor {
 
+    /**
+     * Index into {@link #trace}
+     */
     private int index = 0;
+
+    /**
+     * Number of frames stored (native or Java frames). Because Java frames take up more than one
+     * entry in {@link #trace} this number might be different to {@link #index}.
+     */
+    private int numFrames = 0;
     private final int limit = computeNativeLimit();
 
     /*
@@ -270,6 +283,7 @@ final class BacktraceVisitor extends StackFrameVisitor {
     private long[] trace = new long[INITIAL_TRACE_SIZE];
 
     public static final int NATIVE_FRAME_LIMIT_MARGIN = 10;
+    static final int MAX_ENTRIES_PER_FRAME = useCompressedReferences() ? 2 : 3;
 
     /**
      * Gets the number of native frames to collect. Native frames and Java frames do not directly
@@ -293,45 +307,197 @@ private static int computeNativeLimit() {
         return maxJavaStackTraceDepthExtended > maxJavaStackTraceDepth ? maxJavaStackTraceDepthExtended : Integer.MAX_VALUE;
     }
 
-    @Uninterruptible(reason = "Prevent the GC from freeing the CodeInfo object.")
-    private static boolean decodeCodePointer(BuildStackTraceVisitor visitor, CodePointer ip) {
-        UntetheredCodeInfo untetheredInfo = CodeInfoTable.lookupCodeInfo(ip);
-        if (untetheredInfo.isNull()) {
-            /* Unknown frame. Must not happen for AOT-compiled code. */
-            throw VMError.shouldNotReachHere("Stack walk must walk only frames of known code.");
+    @Override
+    protected boolean visitFrame(Pointer sp, CodePointer ip, CodeInfo codeInfo, DeoptimizedFrame deoptimizedFrame) {
+        if (deoptimizedFrame != null) {
+            for (DeoptimizedFrame.VirtualFrame frame = deoptimizedFrame.getTopFrame(); frame != null; frame = frame.getCaller()) {
+                FrameInfoQueryResult frameInfo = frame.getFrameInfo();
+                if (!visitFrameInfo(frameInfo)) {
+                    return false;
+                }
+            }
+        } else if (!isAOTCodePointer(ip)) {
+            CodeInfoQueryResult queryResult = CodeInfoTable.lookupCodeInfoQueryResult(codeInfo, ip);
+            for (FrameInfoQueryResult frameInfo = queryResult.getFrameInfo(); frameInfo != null; frameInfo = frameInfo.getCaller()) {
+                if (!visitFrameInfo(frameInfo)) {
+                    return false;
+                }
+            }
+        } else {
+            visitAOTFrame(ip);
         }
+        return numFrames != limit;
+    }
 
-        Object tether = CodeInfoAccess.acquireTether(untetheredInfo);
-        try {
-            CodeInfo tetheredCodeInfo = CodeInfoAccess.convert(untetheredInfo, tether);
-            if (!visitFrame(visitor, ip, tetheredCodeInfo)) {
-                return true;
-            }
-        } finally {
-            CodeInfoAccess.releaseTether(untetheredInfo, tether);
+    private void visitAOTFrame(CodePointer ip) {
+        long rawValue = ip.rawValue();
+        VMError.guarantee(rawValue != 0, "Unexpected code pointer: 0");
+        VMError.guarantee(!isSourceReference(rawValue), "Not a code pointer: 0x%x", rawValue);
+        ensureSize(index + 1);
+        trace[index++] = rawValue;
+        numFrames++;
+    }
+
+    private boolean visitFrameInfo(FrameInfoQueryResult frameInfo) {
+        if (!StackTraceUtils.shouldShowFrame(frameInfo, false, true, false)) {
+            /* Always ignore the frame. It is an internal frame of the VM. */
+            return true;
+
+        } else if (index == 0 && Throwable.class.isAssignableFrom(frameInfo.getSourceClass())) {
+            /*
+             * We are still in the constructor invocation chain at the beginning of the stack trace,
+             * which is also filtered by the Java HotSpot VM.
+             */
+            return true;
         }
-        return false;
+        int sourceLineNumber = frameInfo.getSourceLineNumber();
+        Class<?> sourceClass = frameInfo.getSourceClass();
+        String sourceMethodName = frameInfo.getSourceMethodName();
+
+        VMError.guarantee(Heap.getHeap().isInImageHeap(sourceClass), "Source class must be in the image heap");
+        VMError.guarantee(Heap.getHeap().isInImageHeap(sourceMethodName), "Source method name string must be in the image heap");
+
+        ensureSize(index + MAX_ENTRIES_PER_FRAME);
+        index += writeSourceReference(trace, index, sourceLineNumber, sourceClass, sourceMethodName);
+        numFrames++;
+        return numFrames != limit;
     }
 
-    @Uninterruptible(reason = "Wraps the now safe call to the possibly interruptible visitor.", callerMustBe = true, calleeMustBe = false)
-    private static boolean visitFrame(BuildStackTraceVisitor visitor, CodePointer ip, CodeInfo tetheredCodeInfo) {
-        return visitor.visitFrame(WordFactory.nullPointer(), ip, tetheredCodeInfo, null);
+    /**
+     * Determines whether a {@link CodePointer} refers to AOT compiled code that is stored in the
+     * image heap and therefore cannot be garbage collected.
+     */
+    public static boolean isAOTCodePointer(CodePointer ip) {
+        return CodeInfoAccess.contains(CodeInfoTable.getImageCodeInfo(), ip);
     }
 
-    @Override
-    protected boolean visitFrame(Pointer sp, CodePointer ip, CodeInfo codeInfo, DeoptimizedFrame deoptimizedFrame) {
-        VMError.guarantee(deoptimizedFrame == null, "Deoptimization not supported");
-        long rawValue = ip.rawValue();
-        VMError.guarantee(rawValue != 0, "Unexpected code pointer: 0");
-        add(rawValue);
-        return index != limit;
+    /**
+     * Determines whether an entry in the {@link Target_java_lang_Throwable#backtrace} array is a
+     * source reference, as written by {@link #writeSourceReference}.
+     *
+     * @implNote A source reference entry has their high bit set, i.e., it is a negative number in
+     *           the tows complement representation (see {@link #encodeLineNumber}).
+     * @see #writeSourceReference
+     * @see #encodeLineNumber
+     */
+    public static boolean isSourceReference(long entry) {
+        return entry < 0;
+    }
+
+    /**
+     * Encodes line number information of a source reference to be stored in the
+     * {@link Target_java_lang_Throwable#backtrace} array. Line numbers can be positive for regular
+     * line number, or zero or negative for to mark special source references.
+     *
+     * @implNote A line number ({@code int}) is stored as a negative {@code long} value to
+     *           distinguish it from an ordinary {@link CodePointer}.
+     *
+     * @see #isSourceReference
+     */
+    public static long encodeLineNumber(int lineNumber) {
+        return 0xffffffff_00000000L | lineNumber;
+    }
+
+    /**
+     * Decodes a line number previously encoded by {@link #encodeLineNumber}.
+     */
+    public static int decodeLineNumber(long entry) {
+        return (int) entry;
     }
 
-    private void add(long value) {
-        if (index == trace.length) {
-            trace = Arrays.copyOf(trace, Math.min(trace.length * 2, limit));
+    /**
+     * Writes source reference to a backtrace array.
+     *
+     * @return the numbers of elements written
+     */
+    static int writeSourceReference(long[] backtrace, int pos, int sourceLineNumber, Class<?> sourceClass, String sourceMethodName) {
+        long encodedLineNumber = encodeLineNumber(sourceLineNumber);
+        VMError.guarantee(isSourceReference(encodedLineNumber), "Encoded line number looks like a code pointer: %s", encodedLineNumber);
+        backtrace[pos] = encodedLineNumber;
+        if (useCompressedReferences()) {
+            long sourceClassOop = assertNonZero(ReferenceAccess.singleton().getCompressedRepresentation(sourceClass).rawValue());
+            long sourceMethodNameOop = assertNonZero(ReferenceAccess.singleton().getCompressedRepresentation(sourceMethodName).rawValue());
+            backtrace[pos + 1] = (sourceClassOop << 32) | (0xfffffffL & sourceMethodNameOop);
+        } else {
+            backtrace[pos + 1] = assertNonZero(Word.objectToUntrackedPointer(sourceClass).rawValue());
+            backtrace[pos + 2] = assertNonZero(Word.objectToUntrackedPointer(sourceMethodName).rawValue());
+        }
+        return MAX_ENTRIES_PER_FRAME;
+    }
+
+    /**
+     * Return the source line number of a source reference entry created by
+     * {@link #writeSourceReference}.
+     * 
+     * @param backtrace the backtrace array
+     * @param pos the start position of the source reference entry
+     * @return the source line number
+     */
+    static int readSourceLineNumber(long[] backtrace, int pos) {
+        return BacktraceVisitor.decodeLineNumber(backtrace[pos]);
+    }
+
+    /**
+     * Return the source class of a source reference entry created by {@link #writeSourceReference}.
+     *
+     * @param backtrace the backtrace array
+     * @param pos the start position of the source reference entry
+     * @return the source class
+     */
+    static Class<?> readSourceClass(long[] backtrace, int pos) {
+        if (useCompressedReferences()) {
+            UnsignedWord ref = WordFactory.unsigned(backtrace[pos + 1]).unsignedShiftRight(32);
+            return (Class<?>) ReferenceAccess.singleton().uncompressReference(ref);
+        } else {
+            Word sourceClassPtr = WordFactory.pointer(backtrace[pos + 1]);
+            return sourceClassPtr.toObject(Class.class, true);
+        }
+    }
+
+    /**
+     * Return the source method name of a source reference entry created by
+     * {@link #writeSourceReference}.
+     *
+     * @param backtrace the backtrace array
+     * @param pos the start position of the source reference entry
+     * @return the source method name
+     */
+    static String readSourceMethodName(long[] backtrace, int pos) {
+        if (useCompressedReferences()) {
+            UnsignedWord ref = WordFactory.unsigned(backtrace[pos + 1]).and(WordFactory.unsigned(0xffffffffL));
+            return (String) ReferenceAccess.singleton().uncompressReference(ref);
+        } else {
+            Word sourceMethodNamePtr = WordFactory.pointer(backtrace[pos + 2]);
+            return sourceMethodNamePtr.toObject(String.class, true);
+        }
+    }
+
+    /**
+     * Determines whether compressed references are enabled. If so, two references can be packed in
+     * a single {@code long} entry.
+     */
+    @Fold
+    static boolean useCompressedReferences() {
+        return ReferenceAccess.singleton().getCompressEncoding().hasShift();
+    }
+
+    private static long assertNonZero(long rawValue) {
+        VMError.guarantee(rawValue != 0, "Must not write 0 values to backtrace");
+        return rawValue;
+    }
+
+    private void ensureSize(int minLength) {
+        if (minLength > trace.length) {
+            trace = Arrays.copyOf(trace, saturatedMultiply(trace.length, 2));
+        }
+    }
+
+    static int saturatedMultiply(int a, int b) {
+        long r = (long) a * (long) b;
+        if ((int) r != r) {
+            return Integer.MAX_VALUE;
         }
-        trace[index++] = value;
+        return (int) r;
     }
 
     /**

From 5230eed715b3ae102ba3e062614defc688290869 Mon Sep 17 00:00:00 2001
From: Josef Eisl <josef.eisl@oracle.com>
Date: Tue, 23 May 2023 15:30:08 +0200
Subject: [PATCH 04/16] svm: avoid VMError.guarantee with format string

---
 .../src/com/oracle/svm/core/jdk/StackTraceUtils.java      | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jdk/StackTraceUtils.java b/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jdk/StackTraceUtils.java
index 902bb396b675..61ae6460a8a5 100644
--- a/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jdk/StackTraceUtils.java
+++ b/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jdk/StackTraceUtils.java
@@ -332,7 +332,9 @@ protected boolean visitFrame(Pointer sp, CodePointer ip, CodeInfo codeInfo, Deop
     private void visitAOTFrame(CodePointer ip) {
         long rawValue = ip.rawValue();
         VMError.guarantee(rawValue != 0, "Unexpected code pointer: 0");
-        VMError.guarantee(!isSourceReference(rawValue), "Not a code pointer: 0x%x", rawValue);
+        if (isSourceReference(rawValue)) {
+            throw VMError.shouldNotReachHere("Not a code pointer: 0x" + Long.toHexString(rawValue));
+        }
         ensureSize(index + 1);
         trace[index++] = rawValue;
         numFrames++;
@@ -412,7 +414,9 @@ public static int decodeLineNumber(long entry) {
      */
     static int writeSourceReference(long[] backtrace, int pos, int sourceLineNumber, Class<?> sourceClass, String sourceMethodName) {
         long encodedLineNumber = encodeLineNumber(sourceLineNumber);
-        VMError.guarantee(isSourceReference(encodedLineNumber), "Encoded line number looks like a code pointer: %s", encodedLineNumber);
+        if (!isSourceReference(encodedLineNumber)) {
+            throw VMError.shouldNotReachHere("Encoded line number looks like a code pointer: " + encodedLineNumber);
+        }
         backtrace[pos] = encodedLineNumber;
         if (useCompressedReferences()) {
             long sourceClassOop = assertNonZero(ReferenceAccess.singleton().getCompressedRepresentation(sourceClass).rawValue());

From eff75a1c4fb8ae583e8ed33fcf923b0df2de7a73 Mon Sep 17 00:00:00 2001
From: Josef Eisl <josef.eisl@oracle.com>
Date: Wed, 31 May 2023 11:50:13 +0200
Subject: [PATCH 05/16] svm: make BacktraceDecoder more readable

---
 .../src/com/oracle/svm/core/jdk/BacktraceDecoder.java     | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jdk/BacktraceDecoder.java b/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jdk/BacktraceDecoder.java
index 20fec016f433..38a28bccbb51 100644
--- a/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jdk/BacktraceDecoder.java
+++ b/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jdk/BacktraceDecoder.java
@@ -63,11 +63,14 @@ protected final int visitBacktrace(Object backtrace, int maxFramesProcessed, int
                 if (BacktraceVisitor.isSourceReference(entry)) {
                     /* Entry is an encoded source reference. */
                     VMError.guarantee(backtraceIndex + BacktraceVisitor.MAX_ENTRIES_PER_FRAME <= trace.length, "Truncated backtrace array");
-                    backtraceIndex += visitSourceReference(maxFramesProcessed, framesDecoded, trace, backtraceIndex);
+                    visitSourceReference(maxFramesProcessed, framesDecoded, trace, backtraceIndex);
+                    /* Always a single frame. */
                     framesDecoded++;
+                    backtraceIndex += BacktraceVisitor.MAX_ENTRIES_PER_FRAME;
                 } else {
                     /* Entry is a raw code pointer. */
                     CodePointer ip = WordFactory.pointer(entry);
+                    /* Arbitrary number of Java frames for a single native frame (inlining). */
                     framesDecoded = visitCodePointer(ip, framesDecoded, maxFramesProcessed, maxFramesDecodeLimit);
                     backtraceIndex++;
                 }
@@ -79,7 +82,7 @@ protected final int visitBacktrace(Object backtrace, int maxFramesProcessed, int
         return framesDecoded - maxFramesProcessed;
     }
 
-    private int visitSourceReference(int maxFramesProcessed, int framesDecoded, long[] trace, int backtraceIndex) {
+    private void visitSourceReference(int maxFramesProcessed, int framesDecoded, long[] trace, int backtraceIndex) {
         int sourceLineNumber = BacktraceVisitor.readSourceLineNumber(trace, backtraceIndex);
         Class<?> sourceClass = BacktraceVisitor.readSourceClass(trace, backtraceIndex);
         String sourceMethodName = BacktraceVisitor.readSourceMethodName(trace, backtraceIndex);
@@ -87,7 +90,6 @@ private int visitSourceReference(int maxFramesProcessed, int framesDecoded, long
         if (framesDecoded < maxFramesProcessed) {
             processSourceReference(sourceClass, sourceMethodName, sourceLineNumber);
         }
-        return BacktraceVisitor.MAX_ENTRIES_PER_FRAME;
     }
 
     @Uninterruptible(reason = "Prevent the GC from freeing the CodeInfo object.")

From 936b7bff953979c568a0142ff43b7fbd7e925886 Mon Sep 17 00:00:00 2001
From: Josef Eisl <josef.eisl@oracle.com>
Date: Wed, 31 May 2023 13:56:06 +0200
Subject: [PATCH 06/16] svm: make BacktraceVisitor more readable

---
 .../oracle/svm/core/jdk/StackTraceUtils.java  | 78 +++++++++++++++++--
 1 file changed, 73 insertions(+), 5 deletions(-)

diff --git a/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jdk/StackTraceUtils.java b/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jdk/StackTraceUtils.java
index 61ae6460a8a5..8fa39d10d11e 100644
--- a/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jdk/StackTraceUtils.java
+++ b/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jdk/StackTraceUtils.java
@@ -260,6 +260,67 @@ protected void operate() {
 /**
  * Visits the stack frames and collects a backtrace in an internal format to be stored in
  * {@link Target_java_lang_Throwable#backtrace}.
+ *
+ * The {@link Target_java_lang_Throwable#backtrace} is a {@code long} array that either stores a
+ * native instruction pointer (for AOT compiled methods) or an encoded Java source reference
+ * containing a source line number, a source class and a source method name (for JIT compiled
+ * methods). A native instruction pointer is always a single {@code long} element, while an encoded
+ * Java source reference takes {@linkplain #MAX_ENTRIES_PER_FRAME 2 elements} if references are
+ * {@link #useCompressedReferences() compressed}, or 3 otherwise. Native instruction pointers and
+ * source references can be mixed. The source line number of the source reference is
+ * {@linkplain #encodeLineNumber encoded} in a way that it can be distinguished from a native
+ * instruction pointer.
+ *
+ * <h2>Uncompressed References</h2>
+ * 
+ * <pre>
+ *                      backtrace content      |   Number of Java frames
+ *                    ---------------------------------------------------
+ * backtrace[pos + 0] | native inst. pointer   |   X Java frames
+ *                    --------------------------
+ * backtrace[pos + 1] | native inst. pointer   |   Y Java frames
+ *                    --------------------------
+ * backtrace[pos + 2] | encoded src line nr    |   1 Java frame
+ * backtrace[pos + 3] | source class ref       |
+ * backtrace[pos + 4] | source method name ref |
+ *                    --------------------------
+ * backtrace[pos + 5] | encoded src line nr    |   1 Java frame
+ * backtrace[pos + 6] | source class ref       |
+ * backtrace[pos + 7] | source method name ref |
+ *                    --------------------------
+ * backtrace[pos + 8] | native inst. pointer   |   Z Java frames
+ *                    --------------------------
+ *                    | ... remaining          |
+ *                    --------------------------
+ *                    | 0                      |   0 terminated if not all elements are used
+ * </pre>
+ *
+ * <h2>Compressed References</h2>
+ * 
+ * <pre>
+ *                      backtrace content                                   |   Number of Java frames
+ *                    --------------------------------------------------------------------------------
+ * backtrace[pos + 0] | native inst. pointer                                |   X Java frames
+ *                    -------------------------------------------------------
+ * backtrace[pos + 1] | native inst. pointer                                |   Y Java frames
+ *                    -------------------------------------------------------
+ * backtrace[pos + 2] | encoded src line nr                                 |   1 Java frame
+ * backtrace[pos + 3] | (source class ref) << 32 | (source method name ref) |
+ *                    -------------------------------------------------------
+ * backtrace[pos + 4] | encoded src line nr                                 |   1 Java frame
+ * backtrace[pos + 5] | (source class ref) << 32 | (source method name ref) |
+ *                    -------------------------------------------------------
+ * backtrace[pos + 5] | native inst. pointer                                |   Z Java frames
+ *                    -------------------------------------------------------
+ *                    | ... remaining                                       |
+ *                    -------------------------------------------------------
+ *                    | 0                                                   |   0 terminated if not all elements are used
+ * </pre>
+ *
+ * @see #writeSourceReference writes the source references into the backtrace array
+ * @see #visitAOTFrame writes a native instruction pointer into the backtrace array
+ * @see BacktraceDecoder decodes the backtrace array
+ *
  */
 final class BacktraceVisitor extends StackFrameVisitor {
 
@@ -360,7 +421,8 @@ private boolean visitFrameInfo(FrameInfoQueryResult frameInfo) {
         VMError.guarantee(Heap.getHeap().isInImageHeap(sourceMethodName), "Source method name string must be in the image heap");
 
         ensureSize(index + MAX_ENTRIES_PER_FRAME);
-        index += writeSourceReference(trace, index, sourceLineNumber, sourceClass, sourceMethodName);
+        writeSourceReference(trace, index, sourceLineNumber, sourceClass, sourceMethodName);
+        index += MAX_ENTRIES_PER_FRAME;
         numFrames++;
         return numFrames != limit;
     }
@@ -410,9 +472,12 @@ public static int decodeLineNumber(long entry) {
     /**
      * Writes source reference to a backtrace array.
      *
-     * @return the numbers of elements written
+     * @see #readSourceLineNumber
+     * @see #readSourceClass
+     * @see #readSourceMethodName
      */
-    static int writeSourceReference(long[] backtrace, int pos, int sourceLineNumber, Class<?> sourceClass, String sourceMethodName) {
+    static void writeSourceReference(long[] backtrace, int pos, int sourceLineNumber, Class<?> sourceClass, String sourceMethodName) {
+        // TODO document frame format
         long encodedLineNumber = encodeLineNumber(sourceLineNumber);
         if (!isSourceReference(encodedLineNumber)) {
             throw VMError.shouldNotReachHere("Encoded line number looks like a code pointer: " + encodedLineNumber);
@@ -421,12 +486,13 @@ static int writeSourceReference(long[] backtrace, int pos, int sourceLineNumber,
         if (useCompressedReferences()) {
             long sourceClassOop = assertNonZero(ReferenceAccess.singleton().getCompressedRepresentation(sourceClass).rawValue());
             long sourceMethodNameOop = assertNonZero(ReferenceAccess.singleton().getCompressedRepresentation(sourceMethodName).rawValue());
-            backtrace[pos + 1] = (sourceClassOop << 32) | (0xfffffffL & sourceMethodNameOop);
+            VMError.guarantee((0xffffffff_00000000L & sourceClassOop) == 0L, "Compressed source class reference with high bits");
+            VMError.guarantee((0xffffffff_00000000L & sourceMethodNameOop) == 0L, "Compressed source methode name reference with high bits");
+            backtrace[pos + 1] = (sourceClassOop << 32) | sourceMethodNameOop;
         } else {
             backtrace[pos + 1] = assertNonZero(Word.objectToUntrackedPointer(sourceClass).rawValue());
             backtrace[pos + 2] = assertNonZero(Word.objectToUntrackedPointer(sourceMethodName).rawValue());
         }
-        return MAX_ENTRIES_PER_FRAME;
     }
 
     /**
@@ -436,6 +502,8 @@ static int writeSourceReference(long[] backtrace, int pos, int sourceLineNumber,
      * @param backtrace the backtrace array
      * @param pos the start position of the source reference entry
      * @return the source line number
+     *
+     * @see #writeSourceReference
      */
     static int readSourceLineNumber(long[] backtrace, int pos) {
         return BacktraceVisitor.decodeLineNumber(backtrace[pos]);

From 1ef3ab58fe05e9dbe91ef54e8e94c377c962c1f1 Mon Sep 17 00:00:00 2001
From: Josef Eisl <josef.eisl@oracle.com>
Date: Wed, 31 May 2023 14:02:08 +0200
Subject: [PATCH 07/16] svm: eliminate dead code in fillInStackTrace if
 deoptimization is disabled

---
 .../src/com/oracle/svm/core/jdk/BacktraceDecoder.java     | 4 +++-
 .../src/com/oracle/svm/core/jdk/StackTraceUtils.java      | 8 ++++++--
 2 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jdk/BacktraceDecoder.java b/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jdk/BacktraceDecoder.java
index 38a28bccbb51..804dd0388732 100644
--- a/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jdk/BacktraceDecoder.java
+++ b/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jdk/BacktraceDecoder.java
@@ -34,6 +34,7 @@
 import com.oracle.svm.core.code.CodeInfoTable;
 import com.oracle.svm.core.code.FrameInfoQueryResult;
 import com.oracle.svm.core.code.UntetheredCodeInfo;
+import com.oracle.svm.core.deopt.DeoptimizationSupport;
 import com.oracle.svm.core.heap.RestrictHeapAccess;
 import com.oracle.svm.core.util.VMError;
 
@@ -60,7 +61,7 @@ protected final int visitBacktrace(Object backtrace, int maxFramesProcessed, int
             int backtraceIndex = 0;
             while (backtraceIndex < trace.length && trace[backtraceIndex] != 0) {
                 long entry = trace[backtraceIndex];
-                if (BacktraceVisitor.isSourceReference(entry)) {
+                if (DeoptimizationSupport.enabled() && BacktraceVisitor.isSourceReference(entry)) {
                     /* Entry is an encoded source reference. */
                     VMError.guarantee(backtraceIndex + BacktraceVisitor.MAX_ENTRIES_PER_FRAME <= trace.length, "Truncated backtrace array");
                     visitSourceReference(maxFramesProcessed, framesDecoded, trace, backtraceIndex);
@@ -68,6 +69,7 @@ protected final int visitBacktrace(Object backtrace, int maxFramesProcessed, int
                     framesDecoded++;
                     backtraceIndex += BacktraceVisitor.MAX_ENTRIES_PER_FRAME;
                 } else {
+                    VMError.guarantee(!BacktraceVisitor.isSourceReference(entry), "Unexpected source reference");
                     /* Entry is a raw code pointer. */
                     CodePointer ip = WordFactory.pointer(entry);
                     /* Arbitrary number of Java frames for a single native frame (inlining). */
diff --git a/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jdk/StackTraceUtils.java b/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jdk/StackTraceUtils.java
index 8fa39d10d11e..96579995ff68 100644
--- a/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jdk/StackTraceUtils.java
+++ b/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jdk/StackTraceUtils.java
@@ -49,7 +49,9 @@
 import com.oracle.svm.core.code.CodeInfoQueryResult;
 import com.oracle.svm.core.code.CodeInfoTable;
 import com.oracle.svm.core.code.FrameInfoQueryResult;
+import com.oracle.svm.core.deopt.DeoptimizationSupport;
 import com.oracle.svm.core.deopt.DeoptimizedFrame;
+import com.oracle.svm.core.graal.RuntimeCompilation;
 import com.oracle.svm.core.heap.Heap;
 import com.oracle.svm.core.heap.ReferenceAccess;
 import com.oracle.svm.core.heap.VMOperationInfos;
@@ -370,14 +372,14 @@ private static int computeNativeLimit() {
 
     @Override
     protected boolean visitFrame(Pointer sp, CodePointer ip, CodeInfo codeInfo, DeoptimizedFrame deoptimizedFrame) {
-        if (deoptimizedFrame != null) {
+        if (DeoptimizationSupport.enabled() && deoptimizedFrame != null) {
             for (DeoptimizedFrame.VirtualFrame frame = deoptimizedFrame.getTopFrame(); frame != null; frame = frame.getCaller()) {
                 FrameInfoQueryResult frameInfo = frame.getFrameInfo();
                 if (!visitFrameInfo(frameInfo)) {
                     return false;
                 }
             }
-        } else if (!isAOTCodePointer(ip)) {
+        } else if (RuntimeCompilation.isEnabled() && !isAOTCodePointer(ip)) {
             CodeInfoQueryResult queryResult = CodeInfoTable.lookupCodeInfoQueryResult(codeInfo, ip);
             for (FrameInfoQueryResult frameInfo = queryResult.getFrameInfo(); frameInfo != null; frameInfo = frameInfo.getCaller()) {
                 if (!visitFrameInfo(frameInfo)) {
@@ -385,6 +387,8 @@ protected boolean visitFrame(Pointer sp, CodePointer ip, CodeInfo codeInfo, Deop
                 }
             }
         } else {
+            VMError.guarantee(deoptimizedFrame == null, "deoptimizedFrame non-null");
+            VMError.guarantee(isAOTCodePointer(ip), "Trying to store native instruction pointer of a JIT method");
             visitAOTFrame(ip);
         }
         return numFrames != limit;

From 27a1cc8648b5e358ce25b2581acea314853c0222 Mon Sep 17 00:00:00 2001
From: Josef Eisl <josef.eisl@oracle.com>
Date: Wed, 31 May 2023 14:06:35 +0200
Subject: [PATCH 08/16] svm: disable Throwable#getOurStackTrace in
 TruffleFeature

---
 .../src/com/oracle/svm/truffle/TruffleFeature.java               | 1 +
 1 file changed, 1 insertion(+)

diff --git a/substratevm/src/com.oracle.svm.truffle/src/com/oracle/svm/truffle/TruffleFeature.java b/substratevm/src/com.oracle.svm.truffle/src/com/oracle/svm/truffle/TruffleFeature.java
index 70ef4882f9a2..a9feffc28088 100644
--- a/substratevm/src/com.oracle.svm.truffle/src/com/oracle/svm/truffle/TruffleFeature.java
+++ b/substratevm/src/com.oracle.svm.truffle/src/com/oracle/svm/truffle/TruffleFeature.java
@@ -583,6 +583,7 @@ private void initializeMethodBlocklist(MetaAccessProvider metaAccess, FeatureAcc
         blocklistMethod(metaAccess, Throwable.class, "fillInStackTrace");
         // Implementations which don't call Throwable.fillInStackTrace are allowed
         implementationOnlyBlocklist(metaAccess, Throwable.class, "fillInStackTrace");
+        blocklistMethod(metaAccess, Throwable.class, "getOurStackTrace");
         blocklistMethod(metaAccess, Throwable.class, "initCause", Throwable.class);
         blocklistMethod(metaAccess, Throwable.class, "addSuppressed", Throwable.class);
         blocklistMethod(metaAccess, System.class, "getProperty", String.class);

From 6cd7b7a6e7cbe9981c6182a65f7d602512b79ee0 Mon Sep 17 00:00:00 2001
From: Josef Eisl <josef.eisl@oracle.com>
Date: Wed, 31 May 2023 14:26:10 +0200
Subject: [PATCH 09/16] svm: fix style issues

---
 .../src/com/oracle/svm/core/jdk/StackTraceUtils.java            | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jdk/StackTraceUtils.java b/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jdk/StackTraceUtils.java
index 96579995ff68..4c888498c4b6 100644
--- a/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jdk/StackTraceUtils.java
+++ b/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jdk/StackTraceUtils.java
@@ -327,7 +327,7 @@ protected void operate() {
 final class BacktraceVisitor extends StackFrameVisitor {
 
     /**
-     * Index into {@link #trace}
+     * Index into {@link #trace}.
      */
     private int index = 0;
 

From 6b4862c74e2be0200f353bcfde9fb8ee962c6cc3 Mon Sep 17 00:00:00 2001
From: Josef Eisl <josef.eisl@oracle.com>
Date: Fri, 2 Jun 2023 06:15:12 +0000
Subject: [PATCH 10/16] svm: remove left-over TODO from StackTraceUtils.java

---
 .../src/com/oracle/svm/core/jdk/StackTraceUtils.java             | 1 -
 1 file changed, 1 deletion(-)

diff --git a/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jdk/StackTraceUtils.java b/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jdk/StackTraceUtils.java
index 4c888498c4b6..d0e316870f3b 100644
--- a/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jdk/StackTraceUtils.java
+++ b/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jdk/StackTraceUtils.java
@@ -481,7 +481,6 @@ public static int decodeLineNumber(long entry) {
      * @see #readSourceMethodName
      */
     static void writeSourceReference(long[] backtrace, int pos, int sourceLineNumber, Class<?> sourceClass, String sourceMethodName) {
-        // TODO document frame format
         long encodedLineNumber = encodeLineNumber(sourceLineNumber);
         if (!isSourceReference(encodedLineNumber)) {
             throw VMError.shouldNotReachHere("Encoded line number looks like a code pointer: " + encodedLineNumber);

From aad71dd26729651e0ae82e201a8a35526a66bf03 Mon Sep 17 00:00:00 2001
From: Josef Eisl <josef.eisl@oracle.com>
Date: Mon, 5 Jun 2023 07:51:41 +0200
Subject: [PATCH 11/16] svm: update Javadoc in fillInStackTrace code

---
 .../oracle/svm/core/jdk/StackTraceUtils.java  | 36 ++++++-------------
 1 file changed, 11 insertions(+), 25 deletions(-)

diff --git a/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jdk/StackTraceUtils.java b/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jdk/StackTraceUtils.java
index d0e316870f3b..62c59246d3b3 100644
--- a/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jdk/StackTraceUtils.java
+++ b/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jdk/StackTraceUtils.java
@@ -278,19 +278,11 @@ protected void operate() {
  * <pre>
  *                      backtrace content      |   Number of Java frames
  *                    ---------------------------------------------------
- * backtrace[pos + 0] | native inst. pointer   |   X Java frames
+ * backtrace[pos + 0] | native inst. pointer   |   0..n Java frames
  *                    --------------------------
- * backtrace[pos + 1] | native inst. pointer   |   Y Java frames
- *                    --------------------------
- * backtrace[pos + 2] | encoded src line nr    |   1 Java frame
- * backtrace[pos + 3] | source class ref       |
- * backtrace[pos + 4] | source method name ref |
- *                    --------------------------
- * backtrace[pos + 5] | encoded src line nr    |   1 Java frame
- * backtrace[pos + 6] | source class ref       |
- * backtrace[pos + 7] | source method name ref |
- *                    --------------------------
- * backtrace[pos + 8] | native inst. pointer   |   Z Java frames
+ * backtrace[pos + 1] | encoded src line nr    |   1 Java frame
+ * backtrace[pos + 2] | source class ref       |
+ * backtrace[pos + 3] | source method name ref |
  *                    --------------------------
  *                    | ... remaining          |
  *                    --------------------------
@@ -302,17 +294,10 @@ protected void operate() {
  * <pre>
  *                      backtrace content                                   |   Number of Java frames
  *                    --------------------------------------------------------------------------------
- * backtrace[pos + 0] | native inst. pointer                                |   X Java frames
- *                    -------------------------------------------------------
- * backtrace[pos + 1] | native inst. pointer                                |   Y Java frames
- *                    -------------------------------------------------------
- * backtrace[pos + 2] | encoded src line nr                                 |   1 Java frame
- * backtrace[pos + 3] | (source class ref) << 32 | (source method name ref) |
- *                    -------------------------------------------------------
- * backtrace[pos + 4] | encoded src line nr                                 |   1 Java frame
- * backtrace[pos + 5] | (source class ref) << 32 | (source method name ref) |
+ * backtrace[pos + 0] | native inst. pointer                                |   0..n Java frames
  *                    -------------------------------------------------------
- * backtrace[pos + 5] | native inst. pointer                                |   Z Java frames
+ * backtrace[pos + 1] | encoded src line nr                                 |   1 Java frame
+ * backtrace[pos + 2] | (source class ref) << 32 | (source method name ref) |
  *                    -------------------------------------------------------
  *                    | ... remaining                                       |
  *                    -------------------------------------------------------
@@ -332,8 +317,9 @@ final class BacktraceVisitor extends StackFrameVisitor {
     private int index = 0;
 
     /**
-     * Number of frames stored (native or Java frames). Because Java frames take up more than one
-     * entry in {@link #trace} this number might be different to {@link #index}.
+     * Number of frames stored (native instruction pointers or encoded Java source reference).
+     * Because Java frames take up more than one entry in {@link #trace} this number might be
+     * different to {@link #index}.
      */
     private int numFrames = 0;
     private final int limit = computeNativeLimit();
@@ -444,7 +430,7 @@ public static boolean isAOTCodePointer(CodePointer ip) {
      * source reference, as written by {@link #writeSourceReference}.
      *
      * @implNote A source reference entry has their high bit set, i.e., it is a negative number in
-     *           the tows complement representation (see {@link #encodeLineNumber}).
+     *           the two's complement representation (see {@link #encodeLineNumber}).
      * @see #writeSourceReference
      * @see #encodeLineNumber
      */

From 66f2e8f502399db35daf930c0a23de932f7496d3 Mon Sep 17 00:00:00 2001
From: Josef Eisl <josef.eisl@oracle.com>
Date: Tue, 6 Jun 2023 14:11:27 +0200
Subject: [PATCH 12/16] svm: use getReferenceSize to check for compressed
 reference

---
 .../src/com/oracle/svm/core/jdk/StackTraceUtils.java           | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jdk/StackTraceUtils.java b/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jdk/StackTraceUtils.java
index 62c59246d3b3..4cea1c5c0ec0 100644
--- a/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jdk/StackTraceUtils.java
+++ b/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jdk/StackTraceUtils.java
@@ -49,6 +49,7 @@
 import com.oracle.svm.core.code.CodeInfoQueryResult;
 import com.oracle.svm.core.code.CodeInfoTable;
 import com.oracle.svm.core.code.FrameInfoQueryResult;
+import com.oracle.svm.core.config.ConfigurationValues;
 import com.oracle.svm.core.deopt.DeoptimizationSupport;
 import com.oracle.svm.core.deopt.DeoptimizedFrame;
 import com.oracle.svm.core.graal.RuntimeCompilation;
@@ -539,7 +540,7 @@ static String readSourceMethodName(long[] backtrace, int pos) {
      */
     @Fold
     static boolean useCompressedReferences() {
-        return ReferenceAccess.singleton().getCompressEncoding().hasShift();
+        return ConfigurationValues.getObjectLayout().getReferenceSize() == 4;
     }
 
     private static long assertNonZero(long rawValue) {

From f41d2963a51619b9cf4e5340b13b5f63052ca65f Mon Sep 17 00:00:00 2001
From: Josef Eisl <josef.eisl@oracle.com>
Date: Tue, 6 Jun 2023 14:12:31 +0200
Subject: [PATCH 13/16] svm: rename MAX_ENTRIES_PER_FRAME to
 ENTRIES_PER_SOURCE_REFERENCE

---
 .../com/oracle/svm/core/jdk/BacktraceDecoder.java    |  4 ++--
 .../src/com/oracle/svm/core/jdk/StackTraceUtils.java | 12 ++++++------
 2 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jdk/BacktraceDecoder.java b/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jdk/BacktraceDecoder.java
index 804dd0388732..e585c257ceb9 100644
--- a/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jdk/BacktraceDecoder.java
+++ b/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jdk/BacktraceDecoder.java
@@ -63,11 +63,11 @@ protected final int visitBacktrace(Object backtrace, int maxFramesProcessed, int
                 long entry = trace[backtraceIndex];
                 if (DeoptimizationSupport.enabled() && BacktraceVisitor.isSourceReference(entry)) {
                     /* Entry is an encoded source reference. */
-                    VMError.guarantee(backtraceIndex + BacktraceVisitor.MAX_ENTRIES_PER_FRAME <= trace.length, "Truncated backtrace array");
+                    VMError.guarantee(backtraceIndex + BacktraceVisitor.ENTRIES_PER_SOURCE_REFERENCE <= trace.length, "Truncated backtrace array");
                     visitSourceReference(maxFramesProcessed, framesDecoded, trace, backtraceIndex);
                     /* Always a single frame. */
                     framesDecoded++;
-                    backtraceIndex += BacktraceVisitor.MAX_ENTRIES_PER_FRAME;
+                    backtraceIndex += BacktraceVisitor.ENTRIES_PER_SOURCE_REFERENCE;
                 } else {
                     VMError.guarantee(!BacktraceVisitor.isSourceReference(entry), "Unexpected source reference");
                     /* Entry is a raw code pointer. */
diff --git a/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jdk/StackTraceUtils.java b/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jdk/StackTraceUtils.java
index 4cea1c5c0ec0..b42ac77a91d3 100644
--- a/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jdk/StackTraceUtils.java
+++ b/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jdk/StackTraceUtils.java
@@ -268,9 +268,9 @@ protected void operate() {
  * native instruction pointer (for AOT compiled methods) or an encoded Java source reference
  * containing a source line number, a source class and a source method name (for JIT compiled
  * methods). A native instruction pointer is always a single {@code long} element, while an encoded
- * Java source reference takes {@linkplain #MAX_ENTRIES_PER_FRAME 2 elements} if references are
- * {@link #useCompressedReferences() compressed}, or 3 otherwise. Native instruction pointers and
- * source references can be mixed. The source line number of the source reference is
+ * Java source reference takes {@linkplain #ENTRIES_PER_SOURCE_REFERENCE 2 elements} if references
+ * are {@link #useCompressedReferences() compressed}, or 3 otherwise. Native instruction pointers
+ * and source references can be mixed. The source line number of the source reference is
  * {@linkplain #encodeLineNumber encoded} in a way that it can be distinguished from a native
  * instruction pointer.
  *
@@ -333,7 +333,7 @@ final class BacktraceVisitor extends StackFrameVisitor {
     private long[] trace = new long[INITIAL_TRACE_SIZE];
 
     public static final int NATIVE_FRAME_LIMIT_MARGIN = 10;
-    static final int MAX_ENTRIES_PER_FRAME = useCompressedReferences() ? 2 : 3;
+    static final int ENTRIES_PER_SOURCE_REFERENCE = useCompressedReferences() ? 2 : 3;
 
     /**
      * Gets the number of native frames to collect. Native frames and Java frames do not directly
@@ -411,9 +411,9 @@ private boolean visitFrameInfo(FrameInfoQueryResult frameInfo) {
         VMError.guarantee(Heap.getHeap().isInImageHeap(sourceClass), "Source class must be in the image heap");
         VMError.guarantee(Heap.getHeap().isInImageHeap(sourceMethodName), "Source method name string must be in the image heap");
 
-        ensureSize(index + MAX_ENTRIES_PER_FRAME);
+        ensureSize(index + ENTRIES_PER_SOURCE_REFERENCE);
         writeSourceReference(trace, index, sourceLineNumber, sourceClass, sourceMethodName);
-        index += MAX_ENTRIES_PER_FRAME;
+        index += ENTRIES_PER_SOURCE_REFERENCE;
         numFrames++;
         return numFrames != limit;
     }

From c4c79089af503a9837a1481d25240d82f2ba9929 Mon Sep 17 00:00:00 2001
From: Josef Eisl <josef.eisl@oracle.com>
Date: Tue, 6 Jun 2023 14:19:18 +0200
Subject: [PATCH 14/16] svm: replace ENTRIES_PER_SOURCE_REFERENCE with
 entriesPerSourceReference()

---
 .../com/oracle/svm/core/jdk/BacktraceDecoder.java    |  4 ++--
 .../src/com/oracle/svm/core/jdk/StackTraceUtils.java | 12 ++++++++----
 2 files changed, 10 insertions(+), 6 deletions(-)

diff --git a/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jdk/BacktraceDecoder.java b/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jdk/BacktraceDecoder.java
index e585c257ceb9..e1f286775694 100644
--- a/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jdk/BacktraceDecoder.java
+++ b/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jdk/BacktraceDecoder.java
@@ -63,11 +63,11 @@ protected final int visitBacktrace(Object backtrace, int maxFramesProcessed, int
                 long entry = trace[backtraceIndex];
                 if (DeoptimizationSupport.enabled() && BacktraceVisitor.isSourceReference(entry)) {
                     /* Entry is an encoded source reference. */
-                    VMError.guarantee(backtraceIndex + BacktraceVisitor.ENTRIES_PER_SOURCE_REFERENCE <= trace.length, "Truncated backtrace array");
+                    VMError.guarantee(backtraceIndex + BacktraceVisitor.entriesPerSourceReference() <= trace.length, "Truncated backtrace array");
                     visitSourceReference(maxFramesProcessed, framesDecoded, trace, backtraceIndex);
                     /* Always a single frame. */
                     framesDecoded++;
-                    backtraceIndex += BacktraceVisitor.ENTRIES_PER_SOURCE_REFERENCE;
+                    backtraceIndex += BacktraceVisitor.entriesPerSourceReference();
                 } else {
                     VMError.guarantee(!BacktraceVisitor.isSourceReference(entry), "Unexpected source reference");
                     /* Entry is a raw code pointer. */
diff --git a/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jdk/StackTraceUtils.java b/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jdk/StackTraceUtils.java
index b42ac77a91d3..0314054aac24 100644
--- a/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jdk/StackTraceUtils.java
+++ b/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jdk/StackTraceUtils.java
@@ -268,7 +268,7 @@ protected void operate() {
  * native instruction pointer (for AOT compiled methods) or an encoded Java source reference
  * containing a source line number, a source class and a source method name (for JIT compiled
  * methods). A native instruction pointer is always a single {@code long} element, while an encoded
- * Java source reference takes {@linkplain #ENTRIES_PER_SOURCE_REFERENCE 2 elements} if references
+ * Java source reference takes {@linkplain #entriesPerSourceReference() 2 elements} if references
  * are {@link #useCompressedReferences() compressed}, or 3 otherwise. Native instruction pointers
  * and source references can be mixed. The source line number of the source reference is
  * {@linkplain #encodeLineNumber encoded} in a way that it can be distinguished from a native
@@ -333,7 +333,11 @@ final class BacktraceVisitor extends StackFrameVisitor {
     private long[] trace = new long[INITIAL_TRACE_SIZE];
 
     public static final int NATIVE_FRAME_LIMIT_MARGIN = 10;
-    static final int ENTRIES_PER_SOURCE_REFERENCE = useCompressedReferences() ? 2 : 3;
+
+    @Fold
+    static int entriesPerSourceReference() {
+        return useCompressedReferences() ? 2 : 3;
+    }
 
     /**
      * Gets the number of native frames to collect. Native frames and Java frames do not directly
@@ -411,9 +415,9 @@ private boolean visitFrameInfo(FrameInfoQueryResult frameInfo) {
         VMError.guarantee(Heap.getHeap().isInImageHeap(sourceClass), "Source class must be in the image heap");
         VMError.guarantee(Heap.getHeap().isInImageHeap(sourceMethodName), "Source method name string must be in the image heap");
 
-        ensureSize(index + ENTRIES_PER_SOURCE_REFERENCE);
+        ensureSize(index + entriesPerSourceReference());
         writeSourceReference(trace, index, sourceLineNumber, sourceClass, sourceMethodName);
-        index += ENTRIES_PER_SOURCE_REFERENCE;
+        index += entriesPerSourceReference();
         numFrames++;
         return numFrames != limit;
     }

From bfb06115637c96a524aebddafd70ef9a68626671 Mon Sep 17 00:00:00 2001
From: Josef Eisl <josef.eisl@oracle.com>
Date: Fri, 9 Jun 2023 07:46:39 +0200
Subject: [PATCH 15/16] Revert "svm: eliminate dead code in fillInStackTrace if
 deoptimization is disabled"

This reverts commit 1ef3ab58fe05e9dbe91ef54e8e94c377c962c1f1.
---
 .../src/com/oracle/svm/core/jdk/BacktraceDecoder.java     | 4 +---
 .../src/com/oracle/svm/core/jdk/StackTraceUtils.java      | 8 ++------
 2 files changed, 3 insertions(+), 9 deletions(-)

diff --git a/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jdk/BacktraceDecoder.java b/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jdk/BacktraceDecoder.java
index e1f286775694..ba2e2f4849f0 100644
--- a/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jdk/BacktraceDecoder.java
+++ b/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jdk/BacktraceDecoder.java
@@ -34,7 +34,6 @@
 import com.oracle.svm.core.code.CodeInfoTable;
 import com.oracle.svm.core.code.FrameInfoQueryResult;
 import com.oracle.svm.core.code.UntetheredCodeInfo;
-import com.oracle.svm.core.deopt.DeoptimizationSupport;
 import com.oracle.svm.core.heap.RestrictHeapAccess;
 import com.oracle.svm.core.util.VMError;
 
@@ -61,7 +60,7 @@ protected final int visitBacktrace(Object backtrace, int maxFramesProcessed, int
             int backtraceIndex = 0;
             while (backtraceIndex < trace.length && trace[backtraceIndex] != 0) {
                 long entry = trace[backtraceIndex];
-                if (DeoptimizationSupport.enabled() && BacktraceVisitor.isSourceReference(entry)) {
+                if (BacktraceVisitor.isSourceReference(entry)) {
                     /* Entry is an encoded source reference. */
                     VMError.guarantee(backtraceIndex + BacktraceVisitor.entriesPerSourceReference() <= trace.length, "Truncated backtrace array");
                     visitSourceReference(maxFramesProcessed, framesDecoded, trace, backtraceIndex);
@@ -69,7 +68,6 @@ protected final int visitBacktrace(Object backtrace, int maxFramesProcessed, int
                     framesDecoded++;
                     backtraceIndex += BacktraceVisitor.entriesPerSourceReference();
                 } else {
-                    VMError.guarantee(!BacktraceVisitor.isSourceReference(entry), "Unexpected source reference");
                     /* Entry is a raw code pointer. */
                     CodePointer ip = WordFactory.pointer(entry);
                     /* Arbitrary number of Java frames for a single native frame (inlining). */
diff --git a/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jdk/StackTraceUtils.java b/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jdk/StackTraceUtils.java
index 0314054aac24..73e22630509d 100644
--- a/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jdk/StackTraceUtils.java
+++ b/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jdk/StackTraceUtils.java
@@ -50,9 +50,7 @@
 import com.oracle.svm.core.code.CodeInfoTable;
 import com.oracle.svm.core.code.FrameInfoQueryResult;
 import com.oracle.svm.core.config.ConfigurationValues;
-import com.oracle.svm.core.deopt.DeoptimizationSupport;
 import com.oracle.svm.core.deopt.DeoptimizedFrame;
-import com.oracle.svm.core.graal.RuntimeCompilation;
 import com.oracle.svm.core.heap.Heap;
 import com.oracle.svm.core.heap.ReferenceAccess;
 import com.oracle.svm.core.heap.VMOperationInfos;
@@ -363,14 +361,14 @@ private static int computeNativeLimit() {
 
     @Override
     protected boolean visitFrame(Pointer sp, CodePointer ip, CodeInfo codeInfo, DeoptimizedFrame deoptimizedFrame) {
-        if (DeoptimizationSupport.enabled() && deoptimizedFrame != null) {
+        if (deoptimizedFrame != null) {
             for (DeoptimizedFrame.VirtualFrame frame = deoptimizedFrame.getTopFrame(); frame != null; frame = frame.getCaller()) {
                 FrameInfoQueryResult frameInfo = frame.getFrameInfo();
                 if (!visitFrameInfo(frameInfo)) {
                     return false;
                 }
             }
-        } else if (RuntimeCompilation.isEnabled() && !isAOTCodePointer(ip)) {
+        } else if (!isAOTCodePointer(ip)) {
             CodeInfoQueryResult queryResult = CodeInfoTable.lookupCodeInfoQueryResult(codeInfo, ip);
             for (FrameInfoQueryResult frameInfo = queryResult.getFrameInfo(); frameInfo != null; frameInfo = frameInfo.getCaller()) {
                 if (!visitFrameInfo(frameInfo)) {
@@ -378,8 +376,6 @@ protected boolean visitFrame(Pointer sp, CodePointer ip, CodeInfo codeInfo, Deop
                 }
             }
         } else {
-            VMError.guarantee(deoptimizedFrame == null, "deoptimizedFrame non-null");
-            VMError.guarantee(isAOTCodePointer(ip), "Trying to store native instruction pointer of a JIT method");
             visitAOTFrame(ip);
         }
         return numFrames != limit;

From e7f30465de199d54a8d1c07a29063e4ec35fc5dc Mon Sep 17 00:00:00 2001
From: Josef Eisl <josef.eisl@oracle.com>
Date: Fri, 9 Jun 2023 13:50:09 +0200
Subject: [PATCH 16/16] Revert "svm: disable Throwable#getOurStackTrace in
 TruffleFeature"

This reverts commit 27a1cc8648b5e358ce25b2581acea314853c0222.
---
 .../src/com/oracle/svm/truffle/TruffleFeature.java               | 1 -
 1 file changed, 1 deletion(-)

diff --git a/substratevm/src/com.oracle.svm.truffle/src/com/oracle/svm/truffle/TruffleFeature.java b/substratevm/src/com.oracle.svm.truffle/src/com/oracle/svm/truffle/TruffleFeature.java
index a9feffc28088..70ef4882f9a2 100644
--- a/substratevm/src/com.oracle.svm.truffle/src/com/oracle/svm/truffle/TruffleFeature.java
+++ b/substratevm/src/com.oracle.svm.truffle/src/com/oracle/svm/truffle/TruffleFeature.java
@@ -583,7 +583,6 @@ private void initializeMethodBlocklist(MetaAccessProvider metaAccess, FeatureAcc
         blocklistMethod(metaAccess, Throwable.class, "fillInStackTrace");
         // Implementations which don't call Throwable.fillInStackTrace are allowed
         implementationOnlyBlocklist(metaAccess, Throwable.class, "fillInStackTrace");
-        blocklistMethod(metaAccess, Throwable.class, "getOurStackTrace");
         blocklistMethod(metaAccess, Throwable.class, "initCause", Throwable.class);
         blocklistMethod(metaAccess, Throwable.class, "addSuppressed", Throwable.class);
         blocklistMethod(metaAccess, System.class, "getProperty", String.class);