From 769b3e48ea97a13756cf096ae235d7434c0cae34 Mon Sep 17 00:00:00 2001
From: Claes Redestad <redestad@openjdk.org>
Date: Sun, 2 Jun 2024 20:29:03 +0000
Subject: [PATCH] 8333182: Add truncated tracing mode for TraceBytecodes

Reviewed-by: dholmes, fparain, coleenp
---
 .../share/interpreter/bytecodeTracer.cpp      | 33 ++++++++++++-------
 src/hotspot/share/runtime/globals.hpp         |  3 ++
 2 files changed, 24 insertions(+), 12 deletions(-)

diff --git a/src/hotspot/share/interpreter/bytecodeTracer.cpp b/src/hotspot/share/interpreter/bytecodeTracer.cpp
index b7617c38602..e5a3e9c16f4 100644
--- a/src/hotspot/share/interpreter/bytecodeTracer.cpp
+++ b/src/hotspot/share/interpreter/bytecodeTracer.cpp
@@ -96,7 +96,8 @@ class BytecodePrinter {
   // the adjustments that BytecodeStream performs applies.
   void trace(const methodHandle& method, address bcp, uintptr_t tos, uintptr_t tos2, outputStream* st) {
     ResourceMark rm;
-    if (_current_method != method()) {
+    bool method_changed = _current_method != method();
+    if (method_changed) {
       // Note 1: This code will not work as expected with true MT/MP.
       //         Need an explicit lock or a different solution.
       // It is possible for this block to be skipped, if a garbage
@@ -119,17 +120,24 @@ class BytecodePrinter {
       code = Bytecodes::code_at(method(), bcp);
     }
     _code = code;
-     int bci = (int)(bcp - method->code_base());
-    st->print("[%ld] ", (long) Thread::current()->osthread()->thread_id());
-    if (Verbose) {
-      st->print("%8d  %4d  " INTPTR_FORMAT " " INTPTR_FORMAT " %s",
-           BytecodeCounter::counter_value(), bci, tos, tos2, Bytecodes::name(code));
-    } else {
-      st->print("%8d  %4d  %s",
-           BytecodeCounter::counter_value(), bci, Bytecodes::name(code));
-    }
     _next_pc = is_wide() ? bcp+2 : bcp+1;
-    print_attributes(bci, st);
+    // Trace each bytecode unless we're truncating the tracing output, then only print the first
+    // bytecode in every method as well as returns/throws that pop control flow
+    if (!TraceBytecodesTruncated || method_changed ||
+        code == Bytecodes::_athrow ||
+        code == Bytecodes::_return_register_finalizer ||
+        (code >= Bytecodes::_ireturn && code <= Bytecodes::_return)) {
+      int bci = (int)(bcp - method->code_base());
+      st->print("[%ld] ", (long) Thread::current()->osthread()->thread_id());
+      if (Verbose) {
+        st->print("%8d  %4d  " INTPTR_FORMAT " " INTPTR_FORMAT " %s",
+            BytecodeCounter::counter_value(), bci, tos, tos2, Bytecodes::name(code));
+      } else {
+        st->print("%8d  %4d  %s",
+            BytecodeCounter::counter_value(), bci, Bytecodes::name(code));
+      }
+      print_attributes(bci, st);
+    }
     // Set is_wide for the next one, since the caller of this doesn't skip
     // the next bytecode.
     _is_wide = (code == Bytecodes::_wide);
@@ -336,7 +344,8 @@ void BytecodePrinter::print_attributes(int bci, outputStream* st) {
   // If the code doesn't have any fields there's nothing to print.
   // note this is ==1 because the tableswitch and lookupswitch are
   // zero size (for some reason) and we want to print stuff out for them.
-  if (Bytecodes::length_for(code) == 1) {
+  // Also skip this if we're truncating bytecode output
+  if (TraceBytecodesTruncated || Bytecodes::length_for(code) == 1) {
     st->cr();
     return;
   }
diff --git a/src/hotspot/share/runtime/globals.hpp b/src/hotspot/share/runtime/globals.hpp
index 43771d550a2..481115ddbe9 100644
--- a/src/hotspot/share/runtime/globals.hpp
+++ b/src/hotspot/share/runtime/globals.hpp
@@ -869,6 +869,9 @@ const int ObjectAlignmentInBytes = 8;
   develop(bool, TraceBytecodes, false,                                      \
           "Trace bytecode execution")                                       \
                                                                             \
+  develop(bool, TraceBytecodesTruncated, false,                             \
+          "Truncate non control-flow bytecode when tracing bytecode")       \
+                                                                            \
   develop(bool, VerifyDependencies, trueInDebug,                            \
           "Exercise and verify the compilation dependency mechanism")       \
                                                                             \