[fastcall] Remove stack slot caching

This CL removes the caching of the stack slot used for the fallback mechanism
in V8, as the current implementation is incorrect and needs to be reworked.

Bug: chromium:1185753
Change-Id: I9f77bc42bfd649e0dbcd294b000b48c928cf99d0
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2743886
Commit-Queue: Maya Lekova <mslekova@chromium.org>
Reviewed-by: Georg Neis <neis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#73300}

src/compiler/effect-control-linearizer.cc

@@ -50,8 +50,7 @@ class EffectControlLinearizer {
         broker_(broker),
         graph_assembler_(js_graph, temp_zone, base::nullopt,
                          should_maintain_schedule() ? schedule : nullptr),
-        frame_state_zapper_(nullptr),
-        fast_api_call_stack_slot_(nullptr) {}
+        frame_state_zapper_(nullptr) {}
 
   void Run();
 
@@ -322,8 +321,6 @@ class EffectControlLinearizer {
   JSHeapBroker* broker_;
   JSGraphAssembler graph_assembler_;
   Node* frame_state_zapper_;  // For tracking down compiler::Node::New crashes.
-  Node* fast_api_call_stack_slot_;  // For caching the stack slot allocated for
-  // fast API calls.
 };
 
 namespace {
@@ -5011,28 +5008,24 @@ Node* EffectControlLinearizer::LowerFastApiCall(Node* node) {
   CHECK_EQ(FastApiCallNode::ArityForArgc(c_arg_count, js_arg_count),
            value_input_count);
 
-  if (fast_api_call_stack_slot_ == nullptr) {
+  Node* stack_slot = nullptr;
+  if (c_signature->HasOptions()) {
     int kAlign = alignof(v8::FastApiCallbackOptions);
     int kSize = sizeof(v8::FastApiCallbackOptions);
     // If this check fails, you've probably added new fields to
     // v8::FastApiCallbackOptions, which means you'll need to write code
-    // that initializes and reads from them too (see the Store and Load to
-    // fast_api_call_stack_slot_ below).
+    // that initializes and reads from them too.
     CHECK_EQ(kSize, sizeof(uintptr_t) * 2);
-    fast_api_call_stack_slot_ = __ StackSlot(kSize, kAlign);
-  }
+    stack_slot = __ StackSlot(kSize, kAlign);
 
-  // Leave the slot uninit if the callback doesn't use it.
-  if (c_signature->HasOptions()) {
-    // Generate the stores to `fast_api_call_stack_slot_`.
     __ Store(
         StoreRepresentation(MachineRepresentation::kWord32, kNoWriteBarrier),
-        fast_api_call_stack_slot_,
+        stack_slot,
         static_cast<int>(offsetof(v8::FastApiCallbackOptions, fallback)),
         __ ZeroConstant());
     __ Store(StoreRepresentation(MachineType::PointerRepresentation(),
                                  kNoWriteBarrier),
-             fast_api_call_stack_slot_,
+             stack_slot,
              static_cast<int>(offsetof(v8::FastApiCallbackOptions, data)),
              n.SlowCallArgument(FastApiCallNode::kSlowCallDataArgumentIndex));
   }
@@ -5047,7 +5040,7 @@ Node* EffectControlLinearizer::LowerFastApiCall(Node* node) {
     builder.AddParam(machine_type);
   }
   if (c_signature->HasOptions()) {
-    builder.AddParam(MachineType::Pointer());  // fast_api_call_stack_slot_
+    builder.AddParam(MachineType::Pointer());  // stack_slot
   }
 
   CallDescriptor* call_descriptor =
@@ -5076,7 +5069,7 @@ Node* EffectControlLinearizer::LowerFastApiCall(Node* node) {
     }
   }
   if (c_signature->HasOptions()) {
-    inputs[c_arg_count + 1] = fast_api_call_stack_slot_;
+    inputs[c_arg_count + 1] = stack_slot;
     inputs[c_arg_count + 2] = __ effect();
     inputs[c_arg_count + 3] = __ control();
   } else {
@@ -5125,9 +5118,9 @@ Node* EffectControlLinearizer::LowerFastApiCall(Node* node) {
 
   if (!c_signature->HasOptions()) return fast_call_result;
 
-  // Generate the load from `fast_api_call_stack_slot_`.
+  DCHECK_NOT_NULL(stack_slot);
   Node* load =
-      __ Load(MachineType::Int32(), fast_api_call_stack_slot_,
+      __ Load(MachineType::Int32(), stack_slot,
               static_cast<int>(offsetof(v8::FastApiCallbackOptions, fallback)));
 
   Node* is_zero = __ Word32Equal(load, __ Int32Constant(0));