[liftoff] Allow resuming execution after stepping

R=clemensb@chromium.org

Bug: v8:10321
Change-Id: Ia082b842de8947ead3931943b3bc05903a0f9e29
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2101002Reviewed-by: Clemens Backes <clemensb@chromium.org>
Commit-Queue: Thibaud Michaud <thibaudm@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66704}

src/runtime/runtime-wasm.cc

@@ -619,6 +619,7 @@ RUNTIME_FUNCTION(Runtime_WasmDebugBreak) {
   const auto undefined = ReadOnlyRoots(isolate).undefined_value();
   auto* debug_info = frame_finder.frame()->native_module()->GetDebugInfo();
   if (debug_info->IsStepping(frame_finder.frame())) {
+    debug_info->ClearStepping();
     isolate->debug()->OnDebugBreak(isolate->factory()->empty_fixed_array());
     return undefined;
   }

src/wasm/wasm-debug.cc

@@ -684,10 +684,14 @@ class DebugInfoImpl {
                            isolate);
       stepping_frame_ = frame->id();
     }
+    stepping_ = true;
   }
 
+  void ClearStepping() { stepping_ = false; }
+
   bool IsStepping(WasmCompiledFrame* frame) {
-    return frame->id() == stepping_frame_;
+    DCHECK_IMPLIES(stepping_, stepping_frame_ != NO_ID);
+    return stepping_;
   }
 
   void RemoveDebugSideTables(Vector<WasmCode* const> codes) {
@@ -788,6 +792,7 @@ class DebugInfoImpl {
   // Store the frame ID when stepping, to avoid breaking in recursive calls of
   // the same function.
   StackFrameId stepping_frame_ = NO_ID;
+  bool stepping_ = false;
 
   DISALLOW_COPY_AND_ASSIGN(DebugInfoImpl);
 };
@@ -813,6 +818,8 @@ void DebugInfo::SetBreakpoint(int func_index, int offset,
 
 void DebugInfo::PrepareStep(Isolate* isolate) { impl_->PrepareStep(isolate); }
 
+void DebugInfo::ClearStepping() { impl_->ClearStepping(); }
+
 bool DebugInfo::IsStepping(WasmCompiledFrame* frame) {
   return impl_->IsStepping(frame);
 }

src/wasm/wasm-debug.h

@@ -149,6 +149,8 @@ class DebugInfo {
 
   void PrepareStep(Isolate*);
 
+  void ClearStepping();
+
   bool IsStepping(WasmCompiledFrame*);
 
   void RemoveDebugSideTables(Vector<WasmCode* const>);

test/inspector/debugger/wasm-stepping-liftoff-expected.txt

@@ -10,6 +10,16 @@ Setting breakpoint on offset 59 (should be propagated to 60, the offset of the c
 Paused at wasm://wasm/befe41aa:0:60
 Debugger.stepOver called
 Paused at wasm://wasm/befe41aa:0:62
+Debugger.resume called
+Paused at wasm://wasm/befe41aa:0:60
+Debugger.stepOver called
+Paused at wasm://wasm/befe41aa:0:62
+Debugger.stepOver called
+Paused at wasm://wasm/befe41aa:0:46
+Debugger.resume called
+Paused at wasm://wasm/befe41aa:0:60
+Debugger.stepOver called
+Paused at wasm://wasm/befe41aa:0:62
 Debugger.stepOver called
 Paused at wasm://wasm/befe41aa:0:46
 Debugger.stepOver called
@@ -27,4 +37,9 @@ Paused at wasm://wasm/befe41aa:0:57
 Debugger.stepOver called
 Paused at wasm://wasm/befe41aa:0:60
 Debugger.stepOver called
+Paused at wasm://wasm/befe41aa:0:62
+Debugger.stepOver called
+Paused at wasm://wasm/befe41aa:0:46
+Debugger.resume called
+exports.main returned!
 Finished!

test/inspector/debugger/wasm-stepping-liftoff.js

@@ -75,8 +75,17 @@ function instantiate(bytes) {
   const actualLocation = bpmsg.result.actualLocation;
   InspectorTest.logMessage(actualLocation);
   Protocol.Runtime.evaluate({ expression: 'instance.exports.main(4)' });
+  await waitForPauseAndStep('stepOver');  // over call to wasm_A
+  await waitForPauseAndStep('resume');    // stop on breakpoint
+  await waitForPauseAndStep('stepOver');  // over call
+  await waitForPauseAndStep('stepOver');  // over br
+  await waitForPauseAndStep('resume');    // to next breakpoint (3rd iteration)
+  await waitForPauseAndStep('stepOver');  // over wasm_A
   // Step over 10 times.
   for (let i = 0; i < 10; ++i) await waitForPauseAndStep('stepOver');
+  // Then just resume.
+  await waitForPauseAndStep('resume');
+  InspectorTest.log('exports.main returned!');
   InspectorTest.log('Finished!');
 })().catch(reason => InspectorTest.log(`Failed: ${reason}`))
     .finally(InspectorTest.completeTest);