Revert "Do away with variable length memcpy to Set/Get registers in simulator"

src/arm64/simulator-arm64.h

Index: src/arm64/simulator-arm64.h
diff --git a/src/arm64/simulator-arm64.h b/src/arm64/simulator-arm64.h
index 0dc534c5f98b7b022500b973ff96eacbf256f51b..29a6583ffd7ede78bb4b1c65bb9bc6c0e11ed569 100644
--- a/src/arm64/simulator-arm64.h
+++ b/src/arm64/simulator-arm64.h
@@ -133,28 +133,35 @@ class SimSystemRegister {
 
 
 // Represent a register (r0-r31, v0-v31).
+template<int kSizeInBytes>
 class SimRegisterBase {
  public:
   template<typename T>
-  void Set(T new_value) {
-    value_ = 0;
-    memcpy(&value_, &new_value, sizeof(T));
+  void Set(T new_value, unsigned size = sizeof(T)) {
+    ASSERT(size <= kSizeInBytes);
+    ASSERT(size <= sizeof(new_value));
+    // All AArch64 registers are zero-extending; Writing a W register clears the
+    // top bits of the corresponding X register.
+    memset(value_, 0, kSizeInBytes);
+    memcpy(value_, &new_value, size);
   }
 
+  // Copy 'size' bytes of the register to the result, and zero-extend to fill
+  // the result.
   template<typename T>
-  T Get() const {
+  T Get(unsigned size = sizeof(T)) const {
+    ASSERT(size <= kSizeInBytes);
     T result;
-    memcpy(&result, &value_, sizeof(T));
+    memset(&result, 0, sizeof(result));
+    memcpy(&result, value_, size);
     return result;
   }
 
  protected:
-  int64_t value_;
+  uint8_t value_[kSizeInBytes];
 };
-
-
-typedef SimRegisterBase SimRegister;      // r0-r31
-typedef SimRegisterBase SimFPRegister;    // v0-v31
+typedef SimRegisterBase<kXRegSize> SimRegister;      // r0-r31
+typedef SimRegisterBase<kDRegSize> SimFPRegister;    // v0-v31
 
 
 class Simulator : public DecoderVisitor {
@@ -321,53 +328,86 @@ class Simulator : public DecoderVisitor {
   VISITOR_LIST(DECLARE)
   #undef DECLARE
 
-  bool IsZeroRegister(unsigned code, Reg31Mode r31mode) const {
-    return ((code == 31) && (r31mode == Reg31IsZeroRegister));
-  }
-
   // Register accessors.
+
   // Return 'size' bits of the value of an integer register, as the specified
   // type. The value is zero-extended to fill the result.
   //
+  // The only supported values of 'size' are kXRegSizeInBits and
+  // kWRegSizeInBits.
   template<typename T>
-  T reg(unsigned code, Reg31Mode r31mode = Reg31IsZeroRegister) const {
+  T reg(unsigned size, unsigned code,
+        Reg31Mode r31mode = Reg31IsZeroRegister) const {
+    unsigned size_in_bytes = size / 8;
+    ASSERT(size_in_bytes <= sizeof(T));
+    ASSERT((size == kXRegSizeInBits) || (size == kWRegSizeInBits));
     ASSERT(code < kNumberOfRegisters);
-    if (IsZeroRegister(code, r31mode)) {
-      return 0;
+
+    if ((code == 31) && (r31mode == Reg31IsZeroRegister)) {
+      T result;
+      memset(&result, 0, sizeof(result));
+      return result;
     }
-    return registers_[code].Get<T>();
+    return registers_[code].Get<T>(size_in_bytes);
+  }
+
+  // Like reg(), but infer the access size from the template type.
+  template<typename T>
+  T reg(unsigned code, Reg31Mode r31mode = Reg31IsZeroRegister) const {
+    return reg<T>(sizeof(T) * 8, code, r31mode);
   }
 
   // Common specialized accessors for the reg() template.
-  int32_t wreg(unsigned code, Reg31Mode r31mode = Reg31IsZeroRegister) const {
+  int32_t wreg(unsigned code,
+               Reg31Mode r31mode = Reg31IsZeroRegister) const {
     return reg<int32_t>(code, r31mode);
   }
 
-  int64_t xreg(unsigned code, Reg31Mode r31mode = Reg31IsZeroRegister) const {
+  int64_t xreg(unsigned code,
+               Reg31Mode r31mode = Reg31IsZeroRegister) const {
     return reg<int64_t>(code, r31mode);
   }
 
+  int64_t reg(unsigned size, unsigned code,
+              Reg31Mode r31mode = Reg31IsZeroRegister) const {
+    return reg<int64_t>(size, code, r31mode);
+  }
+
   // Write 'size' bits of 'value' into an integer register. The value is
   // zero-extended. This behaviour matches AArch64 register writes.
+  //
+  // The only supported values of 'size' are kXRegSizeInBits and
+  // kWRegSizeInBits.
+  template<typename T>
+  void set_reg(unsigned size, unsigned code, T value,
+               Reg31Mode r31mode = Reg31IsZeroRegister) {
+    unsigned size_in_bytes = size / 8;
+    ASSERT(size_in_bytes <= sizeof(T));
+    ASSERT((size == kXRegSizeInBits) || (size == kWRegSizeInBits));
+    ASSERT(code < kNumberOfRegisters);
+
+    if ((code == 31) && (r31mode == Reg31IsZeroRegister)) {
+      return;
+    }
+    return registers_[code].Set(value, size_in_bytes);
+  }
 
   // Like set_reg(), but infer the access size from the template type.
   template<typename T>
   void set_reg(unsigned code, T value,
                Reg31Mode r31mode = Reg31IsZeroRegister) {
-    ASSERT(code < kNumberOfRegisters);
-    if (!IsZeroRegister(code, r31mode))
-      registers_[code].Set(value);
+    set_reg(sizeof(value) * 8, code, value, r31mode);
   }
 
   // Common specialized accessors for the set_reg() template.
   void set_wreg(unsigned code, int32_t value,
                 Reg31Mode r31mode = Reg31IsZeroRegister) {
-    set_reg(code, value, r31mode);
+    set_reg(kWRegSizeInBits, code, value, r31mode);
   }
 
   void set_xreg(unsigned code, int64_t value,
                 Reg31Mode r31mode = Reg31IsZeroRegister) {
-    set_reg(code, value, r31mode);
+    set_reg(kXRegSizeInBits, code, value, r31mode);
   }
 
   // Commonly-used special cases.
@@ -392,10 +432,24 @@ class Simulator : public DecoderVisitor {
 
   Address get_sp() { return reg<Address>(31, Reg31IsStackPointer); }
 
+  // Return 'size' bits of the value of a floating-point register, as the
+  // specified type. The value is zero-extended to fill the result.
+  //
+  // The only supported values of 'size' are kDRegSizeInBits and
+  // kSRegSizeInBits.
+  template<typename T>
+  T fpreg(unsigned size, unsigned code) const {
+    unsigned size_in_bytes = size / 8;
+    ASSERT(size_in_bytes <= sizeof(T));
+    ASSERT((size == kDRegSizeInBits) || (size == kSRegSizeInBits));
+    ASSERT(code < kNumberOfFPRegisters);
+    return fpregisters_[code].Get<T>(size_in_bytes);
+  }
+
+  // Like fpreg(), but infer the access size from the template type.
   template<typename T>
   T fpreg(unsigned code) const {
-    ASSERT(code < kNumberOfRegisters);
-    return fpregisters_[code].Get<T>();
+    return fpreg<T>(sizeof(T) * 8, code);
   }
 
   // Common specialized accessors for the fpreg() template.
@@ -431,7 +485,7 @@ class Simulator : public DecoderVisitor {
   void set_fpreg(unsigned code, T value) {
     ASSERT((sizeof(value) == kDRegSize) || (sizeof(value) == kSRegSize));
     ASSERT(code < kNumberOfFPRegisters);
-    fpregisters_[code].Set(value);
+    fpregisters_[code].Set(value, sizeof(value));
   }
 
   // Common specialized accessors for the set_fpreg() template.
@@ -571,19 +625,14 @@ class Simulator : public DecoderVisitor {
     return !ConditionPassed(cond);
   }
 
-  template<typename T>
-  void AddSubHelper(Instruction* instr, T op2);
-  template<typename T>
-  T AddWithCarry(bool set_flags,
-                 T src1,
-                 T src2,
-                 T carry_in = 0);
-  template<typename T>
-  void AddSubWithCarry(Instruction* instr);
-  template<typename T>
-  void LogicalHelper(Instruction* instr, T op2);
-  template<typename T>
-  void ConditionalCompareHelper(Instruction* instr, T op2);
+  void AddSubHelper(Instruction* instr, int64_t op2);
+  int64_t AddWithCarry(unsigned reg_size,
+                       bool set_flags,
+                       int64_t src1,
+                       int64_t src2,
+                       int64_t carry_in = 0);
+  void LogicalHelper(Instruction* instr, int64_t op2);
+  void ConditionalCompareHelper(Instruction* instr, int64_t op2);
   void LoadStoreHelper(Instruction* instr,
                        int64_t offset,
                        AddrMode addrmode);
@@ -610,21 +659,18 @@ class Simulator : public DecoderVisitor {
   void MemoryWrite64(uint8_t* address, uint64_t value);
   void MemoryWriteFP64(uint8_t* address, double value);
 
-
-  template <typename T>
-  T ShiftOperand(T value,
+  int64_t ShiftOperand(unsigned reg_size,
+                       int64_t value,
+                       Shift shift_type,
+                       unsigned amount);
+  int64_t Rotate(unsigned reg_width,
+                 int64_t value,
                  Shift shift_type,
                  unsigned amount);
-  template <typename T>
-  T ExtendValue(T value,
-                Extend extend_type,
-                unsigned left_shift = 0);
-  template <typename T>
-  void Extract(Instruction* instr);
-  template <typename T>
-  void DataProcessing2Source(Instruction* instr);
-  template <typename T>
-  void BitfieldHelper(Instruction* instr);
+  int64_t ExtendValue(unsigned reg_width,
+                      int64_t value,
+                      Extend extend_type,
+                      unsigned left_shift = 0);
 
   uint64_t ReverseBits(uint64_t value, unsigned num_bits);
   uint64_t ReverseBytes(uint64_t value, ReverseByteMode mode);
@@ -750,9 +796,8 @@ class Simulator : public DecoderVisitor {
     // is irrelevant, and is not checked here.
   }
 
-  template <typename T>
-  static int CalcNFlag(T result) {
-    return (result >> (sizeof(T) * 8 - 1)) & 1;
+  static int CalcNFlag(uint64_t result, unsigned reg_size) {
+    return (result >> (reg_size - 1)) & 1;
   }
 
   static int CalcZFlag(uint64_t result) {