JDWP: Optimized single step during debugging
For single stepping full deoptimization and undeoptimizations were
performed with significant overhead, because every code will be
executed in interpreted mode during a single step, even if it is not
strictly required.
For example, if we have a computation heavy method call and we would
like to step over it, that method (and all the methods called from it)
will run in interpreter mode. This can take so long in some cases
(e.g. multiple minutes) that it makes debugging process unusable.
The solution for this limitation is not using full deoptimizations for
single steps and force interpreter only for those methods that we are
about to step into, and require stack deoptimization before step outs.
Bug: 17750566
Bug: 18094282
Bug: https://code.google.com/p/android/issues/detail?id=77984
Change-Id: I683c52465883146c4c84ec47bf96f8efd920527f
Signed-off-by: Daniel Mihalyi <daniel.mihalyi@mattakis.com>
diff --git a/runtime/entrypoints/quick/quick_trampoline_entrypoints.cc b/runtime/entrypoints/quick/quick_trampoline_entrypoints.cc
index 70ee042..5eb97d8 100644
--- a/runtime/entrypoints/quick/quick_trampoline_entrypoints.cc
+++ b/runtime/entrypoints/quick/quick_trampoline_entrypoints.cc
@@ -30,6 +30,7 @@
#include "mirror/object_array-inl.h"
#include "runtime.h"
#include "scoped_thread_state_change.h"
+#include "debugger.h"
namespace art {
@@ -639,6 +640,14 @@
JValue result = interpreter::EnterInterpreterFromEntryPoint(self, code_item, shadow_frame);
// Pop transition.
self->PopManagedStackFragment(fragment);
+
+ // Request a stack deoptimization if needed
+ mirror::ArtMethod* caller = QuickArgumentVisitor::GetCallingMethod(sp);
+ if (UNLIKELY(Dbg::IsForcedInterpreterNeededForUpcall(self, caller))) {
+ self->SetException(Thread::GetDeoptimizationException());
+ self->SetDeoptimizationReturnValue(result);
+ }
+
// No need to restore the args since the method has already been run by the interpreter.
return result.GetJ();
}
@@ -950,14 +959,37 @@
called->GetDexCache()->SetResolvedMethod(called_dex_method_idx, called);
}
}
+
// Ensure that the called method's class is initialized.
StackHandleScope<1> hs(soa.Self());
Handle<mirror::Class> called_class(hs.NewHandle(called->GetDeclaringClass()));
linker->EnsureInitialized(soa.Self(), called_class, true, true);
if (LIKELY(called_class->IsInitialized())) {
- code = called->GetEntryPointFromQuickCompiledCode();
+ if (UNLIKELY(Dbg::IsForcedInterpreterNeededForResolution(self, called))) {
+ // If we are single-stepping or the called method is deoptimized (by a
+ // breakpoint, for example), then we have to execute the called method
+ // with the interpreter.
+ code = GetQuickToInterpreterBridge();
+ } else if (UNLIKELY(Dbg::IsForcedInstrumentationNeededForResolution(self, caller))) {
+ // If the caller is deoptimized (by a breakpoint, for example), we have to
+ // continue its execution with interpreter when returning from the called
+ // method. Because we do not want to execute the called method with the
+ // interpreter, we wrap its execution into the instrumentation stubs.
+ // When the called method returns, it will execute the instrumentation
+ // exit hook that will determine the need of the interpreter with a call
+ // to Dbg::IsForcedInterpreterNeededForUpcall and deoptimize the stack if
+ // it is needed.
+ code = GetQuickInstrumentationEntryPoint();
+ } else {
+ code = called->GetEntryPointFromQuickCompiledCode();
+ }
} else if (called_class->IsInitializing()) {
- if (invoke_type == kStatic) {
+ if (UNLIKELY(Dbg::IsForcedInterpreterNeededForResolution(self, called))) {
+ // If we are single-stepping or the called method is deoptimized (by a
+ // breakpoint, for example), then we have to execute the called method
+ // with the interpreter.
+ code = GetQuickToInterpreterBridge();
+ } else if (invoke_type == kStatic) {
// Class is still initializing, go to oat and grab code (trampoline must be left in place
// until class is initialized to stop races between threads).
code = linker->GetQuickOatCodeFor(called);