A64: Add support for --deopt-every-n-times for n != 2

src/a64/lithium-codegen-a64.cc

Index: src/a64/lithium-codegen-a64.cc
diff --git a/src/a64/lithium-codegen-a64.cc b/src/a64/lithium-codegen-a64.cc
index eaeb9cee9041b2c621d0af99082553167904fe99..1bf10a62d3123b8fb898f1b34cdf9900197897a3 100644
--- a/src/a64/lithium-codegen-a64.cc
+++ b/src/a64/lithium-codegen-a64.cc
@@ -958,14 +958,25 @@ bool LCodeGen::DeoptimizeHeader(LEnvironment* environment) {
     return false;
   }
 
-  ASSERT(FLAG_deopt_every_n_times < 2);  // Other values not supported on A64.
-  TODO_UNIMPLEMENTED("Support for FLAG_deopt_every_n_times >= 2.");
-  if (FLAG_deopt_every_n_times == 1 &&
-      !info()->IsStub() &&
-      info()->opt_count() == id) {
+  if (FLAG_deopt_every_n_times != 0 && !info()->IsStub()) {
+    Label not_zero;
+    ExternalReference count = ExternalReference::stress_deopt_count(isolate());
+
+    __ Push(x0, x1);
+    __ Mov(x0, Operand(count));
+    __ Ldr(w1, MemOperand(x0));
+    __ Subs(x1, x1, 1);
+    __ B(gt, &not_zero);
+    __ Mov(w1, FLAG_deopt_every_n_times);
+    __ Str(w1, MemOperand(x0));
+    __ Pop(x0, x1);
     ASSERT(frame_is_built_);
     __ Call(entry, RelocInfo::RUNTIME_ENTRY);
-    return false;
+    __ Unreachable();
+
+    __ Bind(&not_zero);
+    __ Str(w1, MemOperand(x0));
+    __ Pop(x0, x1);
   }
 
   return true;
@@ -974,8 +985,6 @@ bool LCodeGen::DeoptimizeHeader(LEnvironment* environment) {
 
 void LCodeGen::Deoptimize(LEnvironment* environment,
                           Deoptimizer::BailoutType bailout_type) {
-  if (!DeoptimizeHeader(environment)) return;
-
   ASSERT(environment->HasBeenRegistered());
   ASSERT(info()->IsOptimizing() || info()->IsStub());
   int id = environment->deoptimization_index();