Change the register allocator so that it no longer tracks references...

src/register-allocator.h

Index: src/register-allocator.h
===================================================================
--- src/register-allocator.h	(revision 2055)
+++ src/register-allocator.h	(working copy)
@@ -30,6 +30,16 @@
 
 #include "macro-assembler.h"
 
+#if V8_TARGET_ARCH_IA32
+#include "ia32/register-allocator-ia32.h"
+#elif V8_TARGET_ARCH_X64
+#include "x64/register-allocator-x64.h"
+#elif V8_TARGET_ARCH_ARM
+#include "arm/register-allocator-arm.h"
+#else
+#error Unsupported target architecture.
+#endif
+
 namespace v8 {
 namespace internal {
 
@@ -241,25 +251,28 @@
     }
   }
 
-  // Predicates and accessors for the reference counts.  The versions
-  // that take a register code rather than a register are for
-  // convenience in loops over the register codes.
-  bool is_used(int reg_code) const { return ref_counts_[reg_code] > 0; }
-  bool is_used(Register reg) const { return is_used(reg.code()); }
-  int count(int reg_code) const { return ref_counts_[reg_code]; }
-  int count(Register reg) const { return count(reg.code()); }
+  // Predicates and accessors for the reference counts.
+  bool is_used(int num) {
+    ASSERT(0 <= num && num < kNumRegisters);
+    return ref_counts_[num] > 0;
+  }
 
+  int count(int num) {
+    ASSERT(0 <= num && num < kNumRegisters);
+    return ref_counts_[num];
+  }
+
   // Record a use of a register by incrementing its reference count.
-  void Use(Register reg) {
-    ref_counts_[reg.code()]++;
+  void Use(int num) {
+    ASSERT(0 <= num && num < kNumRegisters);
+    ref_counts_[num]++;
   }
 
   // Record that a register will no longer be used by decrementing its
   // reference count.
-  void Unuse(Register reg) {
-    ASSERT(!reg.is(no_reg));
-    ASSERT(is_used(reg.code()));
-    ref_counts_[reg.code()]--;
+  void Unuse(int num) {
+    ASSERT(is_used(num));
+    ref_counts_[num]--;
   }
 
   // Copy the reference counts from this register file to the other.
@@ -270,17 +283,18 @@
   }
 
  private:
+  static const int kNumRegisters = RegisterAllocatorConstants::kNumRegisters;
+
   int ref_counts_[kNumRegisters];
 
-  // Very fast inlined loop to find a free register.
-  // Used in RegisterAllocator::AllocateWithoutSpilling.
-  // Returns kNumRegisters if no free register found.
-  inline int ScanForFreeRegister() {
-    int i = 0;
-    for (; i < kNumRegisters ; ++i) {
-      if (ref_counts_[i] == 0) break;
+  // Very fast inlined loop to find a free register.  Used in
+  // RegisterAllocator::AllocateWithoutSpilling.  Returns
+  // kInvalidRegister if no free register found.
+  int ScanForFreeRegister() {
+    for (int i = 0; i < RegisterAllocatorConstants::kNumRegisters; i++) {
+      if (!is_used(i)) return i;
     }
-    return i;
+    return RegisterAllocatorConstants::kInvalidRegister;
   }
 
   friend class RegisterAllocator;
@@ -293,55 +307,62 @@
 
 class RegisterAllocator BASE_EMBEDDED {
  public:
+  static const int kNumRegisters =
+      RegisterAllocatorConstants::kNumRegisters;
+  static const int kInvalidRegister =
+      RegisterAllocatorConstants::kInvalidRegister;
+
   explicit RegisterAllocator(CodeGenerator* cgen) : cgen_(cgen) {}
 
-  // A register file with each of the reserved registers counted once.
-  static RegisterFile Reserved();
+  // True if the register is reserved by the code generator, false if it
+  // can be freely used by the allocator Defined in the
+  // platform-specific XXX-inl.h files..
+  static inline bool IsReserved(Register reg);
 
-  // Unuse all the reserved registers in a register file.
-  static void UnuseReserved(RegisterFile* register_file);
+  // Convert between (unreserved) assembler registers and allocator
+  // numbers.  Defined in the platform-specific XXX-inl.h files.
+  static inline int ToNumber(Register reg);
+  static inline Register ToRegister(int num);
 
-  // True if the register is reserved by the code generator, false if it
-  // can be freely used by the allocator.
-  static bool IsReserved(int reg_code);
-  static bool IsReserved(Register reg) { return IsReserved(reg); }
-
   // Predicates and accessors for the registers' reference counts.
-  bool is_used(int reg_code) const { return registers_.is_used(reg_code); }
-  bool is_used(Register reg) const { return registers_.is_used(reg.code()); }
-  int count(int reg_code) const { return registers_.count(reg_code); }
-  int count(Register reg) const { return registers_.count(reg.code()); }
+  bool is_used(int num) { return registers_.is_used(num); }
+  bool is_used(Register reg) { return registers_.is_used(ToNumber(reg)); }
 
+  int count(int num) { return registers_.count(num); }
+  int count(Register reg) { return registers_.count(ToNumber(reg)); }
+
   // Explicitly record a reference to a register.
-  void Use(Register reg) { registers_.Use(reg); }
+  void Use(int num) { registers_.Use(num); }
+  void Use(Register reg) { registers_.Use(ToNumber(reg)); }
 
   // Explicitly record that a register will no longer be used.
-  void Unuse(Register reg) { registers_.Unuse(reg); }
+  void Unuse(int num) { registers_.Unuse(num); }
+  void Unuse(Register reg) { registers_.Unuse(ToNumber(reg)); }
 
+  // Reset the register reference counts to free all non-reserved registers.
+  void Reset() { registers_.Reset(); }
+
   // Initialize the register allocator for entry to a JS function.  On
-  // entry, the registers used by the JS calling convention are
-  // externally referenced (ie, outside the virtual frame); and the
-  // other registers are free.
-  void Initialize();
+  // entry, the (non-reserved) registers used by the JS calling
+  // convention are referenced and the other (non-reserved) registers
+  // are free.
+  inline void Initialize();
 
-  // Reset the register reference counts to free all non-reserved registers.
-  // A frame-external reference is kept to each of the reserved registers.
-  void Reset();
-
   // Allocate a free register and return a register result if possible or
   // fail and return an invalid result.
   Result Allocate();
 
-  // Allocate a specific register if possible, spilling it from the frame if
-  // necessary, or else fail and return an invalid result.
+  // Allocate a specific register if possible, spilling it from the
+  // current frame if necessary, or else fail and return an invalid
+  // result.
   Result Allocate(Register target);
 
-  // Allocate a free register without spilling any from the current frame or
-  // fail and return an invalid result.
+  // Allocate a free register without spilling any from the current
+  // frame or fail and return an invalid result.
   Result AllocateWithoutSpilling();
 
-  // Allocate a free byte register without spilling any from the
-  // current frame or fail and return an invalid result.
+  // Allocate a free byte register without spilling any from the current
+  // frame or fail and return an invalid result.
   Result AllocateByteRegisterWithoutSpilling();
 
   // Copy the internal state to a register file, to be restored later by
@@ -350,6 +371,7 @@
     registers_.CopyTo(register_file);
   }
 
+  // Restore the internal state.
   void RestoreFrom(RegisterFile* register_file) {
     register_file->CopyTo(&registers_);
   }