S390: [Atomics] Remove Atomics code stubs; use TF ops

Port d412cfa2

Original commit message:
    [Atomics] Remove Atomics code stubs; use TF ops

    Reland of (https://codereview.chromium.org/1891033002)

    This is a much cleaner solution, which won't require nearly as much
    architecture-specific code. Thanks bmeurer@!

R=binji@chromium.org, joransiu@ca.ibm.com, bjaideep@ca.ibm.com, michael_dawson@ca.ibm.com, mbrandy@us.ibm.com

BUG=v8:4614
LOG=N

Review URL: https://codereview.chromium.org/1897373003

Cr-Commit-Position: refs/heads/master@{#35657}

src/compiler/s390/code-generator-s390.cc

@@ -67,8 +67,8 @@ class S390OperandConverter final : public InstructionOperandConverter {
 
   MemOperand MemoryOperand(AddressingMode* mode, size_t* first_index) {
     const size_t index = *first_index;
-    *mode = AddressingModeField::decode(instr_->opcode());
-    switch (*mode) {
+    if (mode) *mode = AddressingModeField::decode(instr_->opcode());
+    switch (AddressingModeField::decode(instr_->opcode())) {
       case kMode_None:
         break;
       case kMode_MRI:
@@ -82,7 +82,8 @@ class S390OperandConverter final : public InstructionOperandConverter {
     return MemOperand(r0);
   }
 
-  MemOperand MemoryOperand(AddressingMode* mode, size_t first_index = 0) {
+  MemOperand MemoryOperand(AddressingMode* mode = NULL,
+                           size_t first_index = 0) {
     return MemoryOperand(mode, &first_index);
   }
 
@@ -1660,6 +1661,21 @@ void CodeGenerator::AssembleArchInstruction(Instruction* instr) {
     case kCheckedStoreFloat64:
       ASSEMBLE_CHECKED_STORE_DOUBLE();
       break;
+    case kAtomicLoadInt8:
+      __ LoadB(i.OutputRegister(), i.MemoryOperand());
+      break;
+    case kAtomicLoadUint8:
+      __ LoadlB(i.OutputRegister(), i.MemoryOperand());
+      break;
+    case kAtomicLoadInt16:
+      __ LoadHalfWordP(i.OutputRegister(), i.MemoryOperand());
+      break;
+    case kAtomicLoadUint16:
+      __ LoadLogicalHalfWordP(i.OutputRegister(), i.MemoryOperand());
+      break;
+    case kAtomicLoadWord32:
+      __ Load(i.OutputRegister(), i.MemoryOperand());
+      break;
     default:
       UNREACHABLE();
       break;

src/compiler/s390/instruction-selector-s390.cc

@@ -1750,6 +1750,30 @@ void InstructionSelector::VisitFloat64InsertHighWord32(Node* node) {
        g.UseRegister(left), g.UseRegister(right));
 }
 
+void InstructionSelector::VisitAtomicLoad(Node* node) {
+  LoadRepresentation load_rep = LoadRepresentationOf(node->op());
+  S390OperandGenerator g(this);
+  Node* base = node->InputAt(0);
+  Node* index = node->InputAt(1);
+  ArchOpcode opcode = kArchNop;
+  switch (load_rep.representation()) {
+    case MachineRepresentation::kWord8:
+      opcode = load_rep.IsSigned() ? kAtomicLoadInt8 : kAtomicLoadUint8;
+      break;
+    case MachineRepresentation::kWord16:
+      opcode = load_rep.IsSigned() ? kAtomicLoadInt16 : kAtomicLoadUint16;
+      break;
+    case MachineRepresentation::kWord32:
+      opcode = kAtomicLoadWord32;
+      break;
+    default:
+      UNREACHABLE();
+      return;
+  }
+  Emit(opcode | AddressingModeField::encode(kMode_MRR),
+       g.DefineAsRegister(node), g.UseRegister(base), g.UseRegister(index));
+}
+
 // static
 MachineOperatorBuilder::Flags
 InstructionSelector::SupportedMachineOperatorFlags() {