[wasm] WIP fix arm64 frame alignment.

src/compiler/instruction-selector.cc

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/compiler/instruction-selector.h"
 
 #include <limits>
 
 #include "src/base/adapters.h"
 #include "src/compiler/instruction-selector-impl.h"
@@ skipping 1526 matching lines @@
     DCHECK_EQ(IrOpcode::kIfException, handler->front()->opcode());
     IfExceptionHint hint = OpParameter<IfExceptionHint>(handler->front());
     if (hint == IfExceptionHint::kLocallyCaught) {
       flags |= CallDescriptor::kHasLocalCatchHandler;
     }
     flags |= CallDescriptor::kHasExceptionHandler;
     buffer.instruction_args.push_back(g.Label(handler));
   }
 
   // (arm64 only) caller uses JSSP but callee might destroy it.
-  if (descriptor->UseNativeStack() &&
-      !linkage()->GetIncomingDescriptor()->UseNativeStack()) {
-    flags |= CallDescriptor::kRestoreJSSP;
+  bool caller_native_stack =

[ahaas, 2016/03/29 08:33:58]

Similar to the code in the instruction-selector-arm64 you could call this
variable "from_native_stack".

[titzer, 2016/03/29 09:10:53]

Done.

+      linkage()->GetIncomingDescriptor()->UseNativeStack();
+  bool to_native_stack = descriptor->UseNativeStack();
+  if (caller_native_stack != to_native_stack) {
+    // Mismatch in the use of stack pointers. One or the other has to be
+    // restored.
+    flags |= to_native_stack ? CallDescriptor::kRestoreJSSP
+                             : CallDescriptor::kRestoreCSP;
   }
 
 
   // Select the appropriate opcode based on the call type.
   InstructionCode opcode = kArchNop;
   switch (descriptor->kind()) {
     case CallDescriptor::kCallAddress:
       opcode =
           kArchCallCFunction |
           MiscField::encode(static_cast<int>(descriptor->CParameterCount()));
@@ skipping 225 matching lines @@
   return new (instruction_zone()) FrameStateDescriptor(
       instruction_zone(), state_info.type(), state_info.bailout_id(),
       state_info.state_combine(), parameters, locals, stack,
       state_info.shared_info(), outer_state);
 }
 
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8