PPC/s390: [heap] Remove the old write barrier.

Port ef6c175c

R=ulan@chromium.org, joransiu@ca.ibm.com, michael_dawson@ca.ibm.com
BUG=

Change-Id: I045c22ac71d6ac18e10429e7ba1a7a5ef107529e
Reviewed-on: https://chromium-review.googlesource.com/755894Reviewed-by: Joran Siu <joransiu@ca.ibm.com>
Commit-Queue: Junliang Yan <jyan@ca.ibm.com>
Cr-Commit-Position: refs/heads/master@{#49163}

src/ppc/code-stubs-ppc.cc

@@ -149,6 +149,10 @@ void DoubleToIStub::Generate(MacroAssembler* masm) {
   __ Ret();
 }
 
+void StoreRegistersStateStub::Generate(MacroAssembler* masm) {
+  __ PushSafepointRegisters();
+  __ blr();
+}
 
 void RestoreRegistersStateStub::Generate(MacroAssembler* masm) {
   __ PopSafepointRegisters();

src/s390/code-stubs-s390.cc

@@ -143,6 +143,11 @@ void DoubleToIStub::Generate(MacroAssembler* masm) {
   __ Ret();
 }
 
+void StoreRegistersStateStub::Generate(MacroAssembler* masm) {
+  __ PushSafepointRegisters();
+  __ b(r14);
+}
+
 void RestoreRegistersStateStub::Generate(MacroAssembler* masm) {
   __ PopSafepointRegisters();
   __ b(r14);
@@ -259,7 +264,6 @@ bool CEntryStub::NeedsImmovableCode() { return true; }
 
 void CodeStub::GenerateStubsAheadOfTime(Isolate* isolate) {
   CEntryStub::GenerateAheadOfTime(isolate);
-  StoreBufferOverflowStub::GenerateFixedRegStubsAheadOfTime(isolate);
   CommonArrayConstructorStub::GenerateStubsAheadOfTime(isolate);
   StoreRegistersStateStub::GenerateAheadOfTime(isolate);
   RestoreRegistersStateStub::GenerateAheadOfTime(isolate);
@@ -279,7 +283,6 @@ void RestoreRegistersStateStub::GenerateAheadOfTime(Isolate* isolate) {
 void CodeStub::GenerateFPStubs(Isolate* isolate) {
   SaveFPRegsMode mode = kSaveFPRegs;
   CEntryStub(isolate, 1, mode).GetCode();
-  StoreBufferOverflowStub(isolate, mode).GetCode();
 }
 
 void CEntryStub::GenerateAheadOfTime(Isolate* isolate) {