Disentangle assembler from isolate.

src/s390/assembler-s390-inl.h

Index: src/s390/assembler-s390-inl.h
diff --git a/src/s390/assembler-s390-inl.h b/src/s390/assembler-s390-inl.h
index a38c518deac4acd8365d02afd1e826ecd3cdf0fb..12b607165d4b16b2ade7ae802ded19547a385f9f 100644
--- a/src/s390/assembler-s390-inl.h
+++ b/src/s390/assembler-s390-inl.h
@@ -70,7 +70,7 @@ void RelocInfo::apply(intptr_t delta) {
     // mov sequence
     DCHECK(IsInternalReferenceEncoded(rmode_));
     Address target = Assembler::target_address_at(pc_, host_);
-    Assembler::set_target_address_at(isolate_, pc_, host_, target + delta,
+    Assembler::set_target_address_at(nullptr, pc_, host_, target + delta,
                                      SKIP_ICACHE_FLUSH);
   }
 }
@@ -172,13 +172,12 @@ void RelocInfo::set_target_object(HeapObject* target,
                                   WriteBarrierMode write_barrier_mode,
                                   ICacheFlushMode icache_flush_mode) {
   DCHECK(IsCodeTarget(rmode_) || rmode_ == EMBEDDED_OBJECT);
-  Assembler::set_target_address_at(isolate_, pc_, host_,
+  Assembler::set_target_address_at(target->GetIsolate(), pc_, host_,
                                    reinterpret_cast<Address>(target),
                                    icache_flush_mode);
-  if (write_barrier_mode == UPDATE_WRITE_BARRIER && host() != NULL &&
-      target->IsHeapObject()) {
-    host()->GetHeap()->incremental_marking()->RecordWriteIntoCode(
-        host(), this, HeapObject::cast(target));
+  if (write_barrier_mode == UPDATE_WRITE_BARRIER && host() != NULL) {
+    host()->GetHeap()->incremental_marking()->RecordWriteIntoCode(host(), this,
+                                                                  target);
     host()->GetHeap()->RecordWriteIntoCode(host(), this, target);
   }
 }
@@ -193,12 +192,12 @@ Address RelocInfo::target_runtime_entry(Assembler* origin) {
   return target_address();
 }
 
-void RelocInfo::set_target_runtime_entry(Address target,
+void RelocInfo::set_target_runtime_entry(Isolate* isolate, Address target,
                                          WriteBarrierMode write_barrier_mode,
                                          ICacheFlushMode icache_flush_mode) {
   DCHECK(IsRuntimeEntry(rmode_));
   if (target_address() != target)
-    set_target_address(target, write_barrier_mode, icache_flush_mode);
+    set_target_address(isolate, target, write_barrier_mode, icache_flush_mode);
 }
 
 Handle<Cell> RelocInfo::target_cell_handle() {
@@ -260,9 +259,9 @@ Code* RelocInfo::code_age_stub() {
 void RelocInfo::set_code_age_stub(Code* stub,
                                   ICacheFlushMode icache_flush_mode) {
   DCHECK(rmode_ == RelocInfo::CODE_AGE_SEQUENCE);
-  Assembler::set_target_address_at(isolate_, pc_ + kCodeAgingTargetDelta, host_,
-                                   stub->instruction_start(),
-                                   icache_flush_mode);
+  Assembler::set_target_address_at(
+      stub->GetIsolate(), pc_ + kCodeAgingTargetDelta, host_,
+      stub->instruction_start(), icache_flush_mode);
 }
 
 Address RelocInfo::debug_call_address() {
@@ -270,9 +269,9 @@ Address RelocInfo::debug_call_address() {
   return Assembler::target_address_at(pc_, host_);
 }
 
-void RelocInfo::set_debug_call_address(Address target) {
+void RelocInfo::set_debug_call_address(Isolate* isolate, Address target) {
   DCHECK(IsDebugBreakSlot(rmode()) && IsPatchedDebugBreakSlotSequence());
-  Assembler::set_target_address_at(isolate_, pc_, host_, target);
+  Assembler::set_target_address_at(isolate, pc_, host_, target);
   if (host() != NULL) {
     Code* target_code = Code::GetCodeFromTargetAddress(target);
     host()->GetHeap()->incremental_marking()->RecordWriteIntoCode(host(), this,
@@ -280,7 +279,7 @@ void RelocInfo::set_debug_call_address(Address target) {
   }
 }
 
-void RelocInfo::WipeOut() {
+void RelocInfo::WipeOut(Isolate* isolate) {
   DCHECK(IsEmbeddedObject(rmode_) || IsCodeTarget(rmode_) ||
          IsRuntimeEntry(rmode_) || IsExternalReference(rmode_) ||
          IsInternalReference(rmode_) || IsInternalReferenceEncoded(rmode_));
@@ -290,10 +289,10 @@ void RelocInfo::WipeOut() {
   } else if (IsInternalReferenceEncoded(rmode_)) {
     // mov sequence
     // Currently used only by deserializer, no need to flush.
-    Assembler::set_target_address_at(isolate_, pc_, host_, NULL,
+    Assembler::set_target_address_at(isolate, pc_, host_, NULL,
                                      SKIP_ICACHE_FLUSH);
   } else {
-    Assembler::set_target_address_at(isolate_, pc_, host_, NULL);
+    Assembler::set_target_address_at(isolate, pc_, host_, NULL);
   }
 }
 
@@ -507,6 +506,8 @@ void Assembler::deserialization_set_target_internal_reference_at(
 void Assembler::set_target_address_at(Isolate* isolate, Address pc,
                                       Address constant_pool, Address target,
                                       ICacheFlushMode icache_flush_mode) {
+  DCHECK_IMPLIES(isolate == nullptr, icache_flush_mode == SKIP_ICACHE_FLUSH);
+
   // Check for instructions generated by Asm::mov()
   Opcode op1 = Instruction::S390OpcodeValue(reinterpret_cast<const byte*>(pc));
   SixByteInstr instr_1 =