Fix a harmless assert and a genuine bug in the GC-safety of stub

src/arm/code-stubs-arm.cc

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 841 matching lines @@
   } else {
     __ Strd(r0, r1, FieldMemOperand(heap_number_result,
                                     HeapNumber::kValueOffset));
   }
   // Place heap_number_result in r0 and return to the pushed return address.
   __ mov(r0, Operand(heap_number_result));
   __ pop(pc);
 }
 
 
+bool WriteInt32ToHeapNumberStub::CompilingCallsToThisStubIsGCSafe() {
+  // These variants are compiled ahead of time.  See next method.
+  if (the_int_.is(r1) && the_heap_number_.is(r0) && scratch_.is(r2)) {
+    return true;
+  }
+  if (the_int_.is(r2) && the_heap_number_.is(r0) && scratch_.is(r3)) {
+    return true;
+  }
+  // Other register combinations are generated as and when they are needed,
+  // so it is unsafe to call them from stubs (we can't generate a stub while
+  // we are generating a stub).
+  return false;
+}
+
+
+void WriteInt32ToHeapNumberStub::GenerateStubsAheadOfTime() {
+  WriteInt32ToHeapNumberStub stub1(r1, r0, r2);
+  WriteInt32ToHeapNumberStub stub2(r2, r0, r3);
+  Handle<Code> code1 = stub1.GetCode();
+  Handle<Code> code2 = stub2.GetCode();
+}
+
+
 // See comment for class.
 void WriteInt32ToHeapNumberStub::Generate(MacroAssembler* masm) {
   Label max_negative_int;
   // the_int_ has the answer which is a signed int32 but not a Smi.
   // We test for the special value that has a different exponent.  This test
   // has the neat side effect of setting the flags according to the sign.
   STATIC_ASSERT(HeapNumber::kSignMask == 0x80000000u);
   __ cmp(the_int_, Operand(0x80000000u));
   __ b(eq, &max_negative_int);
   // Set up the correct exponent in scratch_.  All non-Smi int32s have the same.
@@ skipping 320 matching lines @@
   } else {
     // Call a native function to do a comparison between two non-NaNs.
     // Call C routine that may not cause GC or other trouble.
     __ push(lr);
     __ PrepareCallCFunction(0, 2, r5);
     if (masm->use_eabi_hardfloat()) {
       CpuFeatures::Scope scope(VFP3);
       __ vmov(d0, r0, r1);
       __ vmov(d1, r2, r3);
     }
+
+    AllowExternalCallThatCantCauseGC scope(masm);
     __ CallCFunction(ExternalReference::compare_doubles(masm->isolate()),
                      0, 2);
     __ pop(pc);  // Return.
   }
 }
 
 
 // See comment at call site.
 static void EmitStrictTwoHeapObjectCompare(MacroAssembler* masm,
                                            Register lhs,
@@ skipping 2122 matching lines @@
 }
 
 
 bool CEntryStub::CompilingCallsToThisStubIsGCSafe() {
   return (!save_doubles_ || ISOLATE->fp_stubs_generated()) &&
           result_size_ == 1;
 }
 
 
 void CodeStub::GenerateStubsAheadOfTime() {
+  WriteInt32ToHeapNumberStub::GenerateStubsAheadOfTime();
 }
 
 
 void CodeStub::GenerateFPStubs() {
   CEntryStub save_doubles(1);
   save_doubles.SaveDoubles();
   Handle<Code> code = save_doubles.GetCode();
   code->GetIsolate()->set_fp_stubs_generated(true);
 }
 
@@ skipping 3384 matching lines @@
   __ mov(result, Operand::Zero());
   __ Ret();
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_ARM