Fixed crashes exposed though fuzzing.

src/x64/macro-assembler-x64.cc

Index: src/x64/macro-assembler-x64.cc
diff --git a/src/x64/macro-assembler-x64.cc b/src/x64/macro-assembler-x64.cc
index 5127ddf30cd21f35839beb909c34e878af6871de..c84839c0ed426fc6c7192b8ef912c7ca06a957c7 100644
--- a/src/x64/macro-assembler-x64.cc
+++ b/src/x64/macro-assembler-x64.cc
@@ -3206,6 +3206,53 @@ void MacroAssembler::TaggedToI(Register result_reg,
 }
 
 
+void MacroAssembler::Throw(BailoutReason reason) {
+  // We want to pass the msg string like a smi to avoid GC
+  // problems, however msg is not guaranteed to be aligned
+  // properly. Instead, we pass an aligned pointer that is
+  // a proper v8 smi, but also pass the alignment difference
+  // from the real pointer as a smi.
+  const char* msg = GetBailoutReason(reason);
+  intptr_t p1 = reinterpret_cast<intptr_t>(msg);
+  intptr_t p0 = (p1 & ~kSmiTagMask) + kSmiTag;
+  // Note: p0 might not be a valid Smi _value_, but it has a valid Smi tag.
+  ASSERT(reinterpret_cast<Object*>(p0)->IsSmi());
+#ifdef DEBUG
+  if (msg != NULL) {
+    RecordComment("Throw message: ");
+    RecordComment(msg);
+  }
+#endif
+
+  push(rax);
+  movq(kScratchRegister, reinterpret_cast<Smi*>(p0), RelocInfo::NONE64);
+  push(kScratchRegister);
+  movq(kScratchRegister, Smi::FromInt(static_cast<int>(p1 - p0)),
+       RelocInfo::NONE64);
+  push(kScratchRegister);
+
+  if (!has_frame_) {
+    // We don't actually want to generate a pile of code for this, so just
+    // claim there is a stack frame, without generating one.
+    FrameScope scope(this, StackFrame::NONE);
+    CallRuntime(Runtime::kThrowMessage, 2);
+  } else {
+    CallRuntime(Runtime::kThrowMessage, 2);
+  }
+  // Control will not return here.
+  int3();
+}
+
+
+void MacroAssembler::ThrowIfNot(Condition cc, BailoutReason reason) {
+  Label L;
+  j(cc, &L);
+  Throw(reason);
+  // will not return here
+  bind(&L);
+}
+
+
 void MacroAssembler::LoadInstanceDescriptors(Register map,
                                              Register descriptors) {
   movq(descriptors, FieldOperand(map, Map::kDescriptorsOffset));
@@ -4631,6 +4678,35 @@ int MacroAssembler::ArgumentStackSlotsForCFunctionCall(int num_arguments) {
 }
 
 
+void MacroAssembler::EmitSeqStringSetCharCheck(Register string,
+                                               Register index,
+                                               Register value,
+                                               uint32_t encoding_mask) {
+  ThrowIfNot(CheckSmi(index), kNonSmiIndex);
+  ThrowIfNot(CheckSmi(value), kNonSmiValue);
+
+  Label is_object;
+  JumpIfNotSmi(string, &is_object);
+  Throw(kNonObject);
+  bind(&is_object);
+
+  SmiCompare(index, FieldOperand(string, String::kLengthOffset));
+  ThrowIfNot(less, kIndexIsTooLarge);
+
+  SmiCompare(index, Smi::FromInt(0));
+  ThrowIfNot(greater_equal, kIndexIsNegative);
+
+  push(value);
+  movq(value, FieldOperand(string, HeapObject::kMapOffset));
+  movzxbq(value, FieldOperand(value, Map::kInstanceTypeOffset));
+
+  andb(value, Immediate(kStringRepresentationMask | kStringEncodingMask));
+  cmpq(value, Immediate(encoding_mask));
+  pop(value);
+  ThrowIfNot(equal, kUnexpectedStringType);
+}
+
+
 void MacroAssembler::PrepareCallCFunction(int num_arguments) {
   int frame_alignment = OS::ActivationFrameAlignment();
   ASSERT(frame_alignment != 0);