[wasm] WIP fix arm64 frame alignment.

src/compiler/instruction-selector.cc

Index: src/compiler/instruction-selector.cc
diff --git a/src/compiler/instruction-selector.cc b/src/compiler/instruction-selector.cc
index 91900be25c30dabec502028de1401680631509ae..931718174d88dace423d44c9e4d9544fdef003e2 100644
--- a/src/compiler/instruction-selector.cc
+++ b/src/compiler/instruction-selector.cc
@@ -1544,9 +1544,14 @@ void InstructionSelector::VisitCall(Node* node, BasicBlock* 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;
   }