Have JavaFrameRootInfo give more info about provenance of root.

It can be useful to differentiate between java frame roots being the
methods declaring class, from a proxy method, being unknown due to
an imprecise walk or being indeterminable. This passes that
information with the Vreg.

Test: ./test.py --host
Bug: 134162467

Change-Id: I74842d3eeedee5c836511e046652502a53de0f7e

1 files changed, 15 insertions, 0 deletions

diff --git a/runtime/java_frame_root_info.h b/runtime/java_frame_root_info.h
index 8141ea24fd..c21eee1b32 100644
--- a/runtime/java_frame_root_info.h
+++ b/runtime/java_frame_root_info.h
@@ -18,6 +18,7 @@
 #define ART_RUNTIME_JAVA_FRAME_ROOT_INFO_H_
 
 #include <iosfwd>
+#include <limits>
 
 #include "base/locks.h"
 #include "base/macros.h"
@@ -29,6 +30,20 @@ class StackVisitor;
 
 class JavaFrameRootInfo final : public RootInfo {
  public:
+  static_assert(std::numeric_limits<size_t>::max() > std::numeric_limits<uint16_t>::max(),
+                "No extra space in vreg to store meta-data");
+  // Unable to determine what register number the root is from.
+  static constexpr size_t kUnknownVreg = -1;
+  // The register number for the root might be determinable but we did not attempt to find that
+  // information.
+  static constexpr size_t kImpreciseVreg = -2;
+  // The root is from the declaring class of the current method.
+  static constexpr size_t kMethodDeclaringClass = -3;
+  // The root is from the argument to a Proxy invoke.
+  static constexpr size_t kProxyReferenceArgument = -4;
+  // The maximum precise vreg number
+  static constexpr size_t kMaxVReg = std::numeric_limits<uint16_t>::max();
+
   JavaFrameRootInfo(uint32_t thread_id, const StackVisitor* stack_visitor, size_t vreg)
      : RootInfo(kRootJavaFrame, thread_id), stack_visitor_(stack_visitor), vreg_(vreg) {
   }