Proper support for deopt_every_n_times option on the x64 and ARM architectures.

src/arm/lithium-codegen-arm.cc

Index: src/arm/lithium-codegen-arm.cc
diff --git a/src/arm/lithium-codegen-arm.cc b/src/arm/lithium-codegen-arm.cc
index 8eca27d77d9427f5c4fa58ae0d58e8cf4956b28c..094e164c918c94241d4bb2a5d40b62b2804bb79f 100644
--- a/src/arm/lithium-codegen-arm.cc
+++ b/src/arm/lithium-codegen-arm.cc
@@ -769,13 +769,39 @@ void LCodeGen::DeoptimizeIf(Condition condition,
     return;
   }
 
-  ASSERT(FLAG_deopt_every_n_times < 2);  // Other values not supported on ARM.
-  if (FLAG_deopt_every_n_times == 1 &&
-      !info()->IsStub() &&
-      info()->opt_count() == id) {
-    ASSERT(frame_is_built_);
-    __ Call(entry, RelocInfo::RUNTIME_ENTRY);
-    return;
+  if (FLAG_deopt_every_n_times != 0 && !info()->IsStub()) {
+    Register scratch = scratch0();

[vincent.belliard.fr, 2013/11/07 08:43:24]

May be you can leave the case FLAG_deopt_every_n_times == 1. It really generates
less code for this special case.

+    ExternalReference count = ExternalReference::stress_deopt_count(isolate());
+
+    // Store the condition on the stack if necessary
+    if (condition != al) {
+      __ mov(scratch, Operand::Zero());

[vincent.belliard.fr, 2013/11/07 08:43:24]

You can also make this mov conditional (you must negate the condition).

+      __ mov(scratch, Operand(1), LeaveCC, condition);
+      __ push(scratch);
+    }
+
+    __ push(r1);
+    __ mov(scratch, Operand(count));
+    __ ldr(r1, MemOperand(scratch));
+    __ sub(r1, r1, Operand(1), SetCC);
+    __ movw(r1, FLAG_deopt_every_n_times, eq);
+    __ str(r1, MemOperand(scratch));
+    __ pop(r1);
+
+    if (condition != al) {
+      // Clean up the stack before the deoptimizer call
+      __ pop(scratch);
+    }
+
+    __ Call(entry, RelocInfo::RUNTIME_ENTRY, eq);
+
+    // 'Restore' the condition in a slightly hacky way. (It would be better
+    // to use 'msr' and 'mrs' instructions here, but they are not supported by

[vincent.belliard.fr, 2013/11/07 08:43:24]

mrs and msr are available (assembler-arm.h line 1029).

+    // our ARM simulator).
+    if (condition != al) {
+      condition = ne;
+      __ cmp(scratch, Operand::Zero());
+    }
   }
 
   if (info()->ShouldTrapOnDeopt()) {