[maglev] Fix spill slots for InitialValue

InitialValue needs to have a spill slot (e.g. for deopts) but shouldn't
emit an actual spill (since they're already on stack).

Drive-by, fix printing of Checkpoint and CheckMaps parameters.

Bug: v8:7700
Change-Id: I3c1acfce6638b1ad604f7c7a1938694814c326ee
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3497371
Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Auto-Submit: Leszek Swirski <leszeks@chromium.org>
Reviewed-by: Victor Gomes <victorgomes@chromium.org>
Commit-Queue: Victor Gomes <victorgomes@chromium.org>
Cr-Commit-Position: refs/heads/main@{#79320}

src/maglev/maglev-code-generator.cc

@@ -118,12 +118,18 @@ class MaglevCodeGeneratingNodeProcessor {
     if (std::is_base_of<ValueNode, NodeT>::value) {
       ValueNode* value_node = node->template Cast<ValueNode>();
       if (value_node->is_spilled()) {
-        if (FLAG_code_comments) __ RecordComment("--   Spill:");
         compiler::AllocatedOperand source =
             compiler::AllocatedOperand::cast(value_node->result().operand());
         // We shouldn't spill nodes which already output to the stack.
-        DCHECK(!source.IsStackSlot());
-        __ movq(GetStackSlot(value_node->spill_slot()), ToRegister(source));
+        if (!source.IsStackSlot()) {
+          if (FLAG_code_comments) __ RecordComment("--   Spill:");
+          DCHECK(!source.IsStackSlot());
+          __ movq(GetStackSlot(value_node->spill_slot()), ToRegister(source));
+        } else {
+          // Otherwise, the result source stack slot should be equal to the
+          // spill slot.
+          DCHECK_EQ(source.index(), value_node->spill_slot().index());
+        }
       }
     }
   }

src/maglev/maglev-ir.cc

@@ -258,12 +258,13 @@ void EmitDeopt(MaglevCodeGenState* code_gen_state, Node* node,
   for (int i = 0; i < compilation_unit->register_count(); ++i) {
     ValueNode* node = checkpoint_state->get(interpreter::Register(i));
     if (node == nullptr) continue;
-    __ Push(GetStackSlot(node->spill_slot()));
+    __ Push(ToMemOperand(node->spill_slot()));
     num_saved_slots++;
   }
-  if (checkpoint_state->accumulator()) {
+  ValueNode* accumulator = checkpoint_state->accumulator();
+  if (accumulator) {
     __ movq(kInterpreterAccumulatorRegister,
-            GetStackSlot(checkpoint_state->accumulator()->spill_slot()));
+            ToMemOperand(accumulator->spill_slot()));
   }
 
   __ RecordComment("Load registers from extra pushed slots");
@@ -387,7 +388,7 @@ void Checkpoint::GenerateCode(MaglevCodeGenState* code_gen_state,
                               const ProcessingState& state) {}
 void Checkpoint::PrintParams(std::ostream& os,
                              MaglevGraphLabeller* graph_labeller) const {
-  os << "(" << accumulator() << ")";
+  os << "(" << PrintNodeLabel(graph_labeller, accumulator()) << ")";
 }
 
 void SoftDeopt::AllocateVreg(MaglevVregAllocationState* vreg_state,
@@ -551,7 +552,7 @@ void CheckMaps::GenerateCode(MaglevCodeGenState* code_gen_state,
 }
 void CheckMaps::PrintParams(std::ostream& os,
                             MaglevGraphLabeller* graph_labeller) const {
-  os << "(" << map() << ")";
+  os << "(" << *map().object() << ")";
 }
 
 void LoadField::AllocateVreg(MaglevVregAllocationState* vreg_state,

src/maglev/maglev-regalloc.cc

@@ -374,10 +374,12 @@ void StraightForwardRegisterAllocator::AllocateNodeResult(ValueNode* node) {
     DCHECK(node->Is<InitialValue>());
     DCHECK_LT(operand.fixed_slot_index(), 0);
     // Set the stack slot to exactly where the value is.
-    node->result().SetAllocated(compiler::AllocatedOperand::STACK_SLOT,
-                                MachineRepresentation::kTagged,
-                                operand.fixed_slot_index());
-    info->stack_slot = node->result().operand();
+    compiler::AllocatedOperand location(compiler::AllocatedOperand::STACK_SLOT,
+                                        MachineRepresentation::kTagged,
+                                        operand.fixed_slot_index());
+    node->result().SetAllocated(location);
+    node->Spill(location);
+    info->stack_slot = location;
     return;
   }