[maglev] Workaround for generator resume middle loop issue

The current abort will crash if the generator is created by the
interpreter and resumed by the maglevved code.

This current workaround is not ideal since it can introduce
a deopt-reopt loop.

Bug: v8:7700, v8:13109
Change-Id: I7db71a896711255d866ace98eddde85538aa2903
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3879228
Auto-Submit: Victor Gomes <victorgomes@chromium.org>
Commit-Queue: Jakob Linke <jgruber@chromium.org>
Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Reviewed-by: Jakob Linke <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/main@{#83054}

src/deoptimizer/deoptimize-reason.h

@@ -55,6 +55,7 @@ namespace internal {
   V(OutOfBounds, "out of bounds")                                              \
   V(Overflow, "overflow")                                                      \
   V(Smi, "Smi")                                                                \
+  V(SuspendGeneratorIsDead, "SuspendGenerator is in a dead branch")            \
   V(TransitionedToMonomorphicIC, "IC transitioned to monomorphic")             \
   V(TransitionedToMegamorphicIC, "IC transitioned to megamorphic")             \
   V(Unknown, "(unknown)")                                                      \

src/maglev/maglev-graph-builder.h

@@ -209,11 +209,8 @@ class MaglevGraphBuilder {
       // live again.
       //
       // So, manually advance the iterator to the resume, go through the motions
-      // of processing the merge state, but immediately emit an abort (which
-      // also kills the resume).
-      //
-      // TODO(leszeks): Instead of emitting an Abort, we could shrink the
-      // generator switch, removing this resume as an option.
+      // of processing the merge state, but immediately emit an unconditional
+      // deopt (which also kills the resume).
       iterator_.Advance();
       DCHECK_EQ(iterator_.current_bytecode(),
                 interpreter::Bytecode::kResumeGenerator);
@@ -221,7 +218,12 @@ class MaglevGraphBuilder {
       DCHECK_EQ(NumPredecessors(resume_offset), 1);
       ProcessMergePoint(resume_offset);
       StartNewBlock(resume_offset);
-      BuildAbort(AbortReason::kInvalidParametersAndRegistersInGenerator);
+      // TODO(v8:7700): This approach is not ideal. We can create a deopt-reopt
+      // loop: the interpreted code runs, creates a generator while feedback is
+      // still not yet allocated, then suspends the generator, tiers up to
+      // maglev, and reaches this deopt. We then deopt, but since the generator
+      // is never created again, we re-opt without the suspend part and we loop!
+      EmitUnconditionalDeopt(DeoptimizeReason::kSuspendGeneratorIsDead);
       return;
     }