[s390] Port native routines to use UseScratchRegisterScope

Change-Id: If012756df78646769fb89200f2d10d71827d01a5
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1687063
Commit-Queue: Junliang Yan <jyan@ca.ibm.com>
Reviewed-by: Junliang Yan <jyan@ca.ibm.com>
Cr-Commit-Position: refs/heads/master@{#62787}

src/codegen/s390/assembler-s390.cc

@@ -351,7 +351,8 @@ void Assembler::AllocateAndInstallRequestedHeapObjects(Isolate* isolate) {
 
 Assembler::Assembler(const AssemblerOptions& options,
                      std::unique_ptr<AssemblerBuffer> buffer)
-    : AssemblerBase(options, std::move(buffer)) {
+    : AssemblerBase(options, std::move(buffer)),
+      scratch_register_list_(ip.bit()) {
   reloc_info_writer.Reposition(buffer_start_ + buffer_->size(), pc_);
   last_bound_pos_ = 0;
   relocations_.reserve(128);
@@ -830,6 +831,23 @@ void Assembler::EmitRelocations() {
   }
 }
 
+UseScratchRegisterScope::UseScratchRegisterScope(Assembler* assembler)
+    : assembler_(assembler),
+      old_available_(*assembler->GetScratchRegisterList()) {}
+
+UseScratchRegisterScope::~UseScratchRegisterScope() {
+  *assembler_->GetScratchRegisterList() = old_available_;
+}
+
+Register UseScratchRegisterScope::Acquire() {
+  RegList* available = assembler_->GetScratchRegisterList();
+  DCHECK_NOT_NULL(available);
+  DCHECK_NE(*available, 0);
+  int index = static_cast<int>(base::bits::CountTrailingZeros32(*available));
+  Register reg = Register::from_code(index);
+  *available &= ~reg.bit();
+  return reg;
+}
 }  // namespace internal
 }  // namespace v8
 #endif  // V8_TARGET_ARCH_S390

src/codegen/s390/assembler-s390.h

@@ -307,7 +307,6 @@ class V8_EXPORT_PRIVATE Assembler : public AssemblerBase {
   // in the code, so the serializer should not step forwards in memory after
   // a target is resolved and written.
   static constexpr int kSpecialTargetSize = 0;
-
 // Number of bytes for instructions used to store pointer sized constant.
 #if V8_TARGET_ARCH_S390X
   static constexpr int kBytesForPtrConstant = 12;  // IIHF + IILF
@@ -315,6 +314,8 @@ class V8_EXPORT_PRIVATE Assembler : public AssemblerBase {
   static constexpr int kBytesForPtrConstant = 6;  // IILF
 #endif
 
+  RegList* GetScratchRegisterList() { return &scratch_register_list_; }
+
   // ---------------------------------------------------------------------------
   // Code generation
 
@@ -1376,6 +1377,9 @@ class V8_EXPORT_PRIVATE Assembler : public AssemblerBase {
   RelocInfoWriter reloc_info_writer;
   std::vector<DeferredRelocInfo> relocations_;
 
+  // Scratch registers available for use by the Assembler.
+  RegList scratch_register_list_;
+
   // The bound position, before this we cannot do instruction elimination.
   int last_bound_pos_;
 
@@ -1455,6 +1459,7 @@ class V8_EXPORT_PRIVATE Assembler : public AssemblerBase {
   friend class RegExpMacroAssemblerS390;
   friend class RelocInfo;
   friend class EnsureSpace;
+  friend class UseScratchRegisterScope;
 };
 
 class EnsureSpace {
@@ -1462,6 +1467,24 @@ class EnsureSpace {
   explicit EnsureSpace(Assembler* assembler) { assembler->CheckBuffer(); }
 };
 
+class V8_EXPORT_PRIVATE UseScratchRegisterScope {
+ public:
+  explicit UseScratchRegisterScope(Assembler* assembler);
+  ~UseScratchRegisterScope();
+
+  Register Acquire();
+
+  // Check if we have registers available to acquire.
+  bool CanAcquire() const { return *assembler_->GetScratchRegisterList() != 0; }
+
+ private:
+  friend class Assembler;
+  friend class TurboAssembler;
+
+  Assembler* assembler_;
+  RegList old_available_;
+};
+
 }  // namespace internal
 }  // namespace v8