[liftoff][debug] Implement StepOut

R=clemensb@chromium.org

Bug: v8:10321
Change-Id: I318d46fa638c1d6f4d5d347e5aa0ad1faf02d5e2
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2120532
Commit-Queue: Thibaud Michaud <thibaudm@chromium.org>
Reviewed-by: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66855}

src/wasm/wasm-debug.cc

@@ -709,16 +709,23 @@ class DebugInfoImpl {
     DCHECK(!it.done());
     DCHECK(it.frame()->is_wasm_compiled());
     WasmCompiledFrame* frame = WasmCompiledFrame::cast(it.frame());
+    StepAction step_action = isolate->debug()->last_step_action();
 
     // If we are at a return instruction, then any stepping action is equivalent
     // to StepOut, and we need to flood the parent function.
-    if (IsAtReturn(frame)) {
+    if (IsAtReturn(frame) || step_action == StepOut) {
       it.Advance();
       if (it.done() || !it.frame()->is_wasm_compiled()) return;
       frame = WasmCompiledFrame::cast(it.frame());
     }
 
     if (static_cast<int>(frame->function_index()) != flooded_function_index_) {
+      if (flooded_function_index_ != -1) {
+        std::vector<int>& breakpoints =
+            breakpoints_per_function_[flooded_function_index_];
+        RecompileLiftoffWithBreakpoints(flooded_function_index_,
+                                        VectorOf(breakpoints), isolate);
+      }
       FloodWithBreakpoints(frame->function_index(), isolate);
       flooded_function_index_ = frame->function_index();
     }

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

@@ -8,9 +8,13 @@ Setting breakpoint on offset 72 (should be propagated to 73, the offset of the c
     scriptId : <scriptId>
 }
 Paused at wasm://wasm/42af3c82:0:73
+Debugger.stepInto called
+Paused at wasm://wasm/42af3c82:0:52
 Debugger.stepOver called
+Paused at wasm://wasm/42af3c82:0:53
+Debugger.stepOut called
 Paused at wasm://wasm/42af3c82:0:75
-Debugger.resume called
+Debugger.stepOut called
 Paused at wasm://wasm/42af3c82:0:73
 Debugger.stepOver called
 Paused at wasm://wasm/42af3c82:0:75
@@ -20,11 +24,7 @@ Debugger.resume called
 Paused at wasm://wasm/42af3c82:0:73
 Debugger.stepInto called
 Paused at wasm://wasm/42af3c82:0:52
-Debugger.stepOver called
-Paused at wasm://wasm/42af3c82:0:53
-Debugger.stepOver called
-Paused at wasm://wasm/42af3c82:0:54
-Debugger.stepOver called
+Debugger.stepOut called
 Paused at wasm://wasm/42af3c82:0:75
 Debugger.stepInto called
 Paused at wasm://wasm/42af3c82:0:59

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

@@ -93,15 +93,15 @@ function instantiate(bytes) {
 
   InspectorTest.logMessage(bpmsg.result.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('stepInto');  // into call to wasm_A
+  await waitForPauseAndStep('stepOver');  // over first nop
+  await waitForPauseAndStep('stepOut');   // out of wasm_A
+  await waitForPauseAndStep('stepOut');   // out of wasm_B, stop on breakpoint
   await waitForPauseAndStep('stepOver');  // over call
   await waitForPauseAndStep('stepInto');  // == stepOver br
   await waitForPauseAndStep('resume');    // to next breakpoint (3rd iteration)
   await waitForPauseAndStep('stepInto');  // into wasm_A
-  // Step out of wasm_A, back to wasm_B.
-  // TODO(clemensb/thibaudm): Replace by an actual 'stepOut'.
-  for (let i = 0; i < 3; ++i) await waitForPauseAndStep('stepOver');
+  await waitForPauseAndStep('stepOut');   // out to wasm_B
   // Now step 10 times, until we are in wasm_A again.
   for (let i = 0; i < 10; ++i) await waitForPauseAndStep('stepInto');
   // 3 more times, back to wasm_B.