[Turbofan] Add the concept of aliasing to RegisterConfiguration.

src/register-configuration.h

Index: src/register-configuration.h
diff --git a/src/register-configuration.h b/src/register-configuration.h
index 4e304b6a9ca6a37e6498457d3c6e5395fa132ec5..ff34a63d5dcceb5137d74cd8cd5e09f222973433 100644
--- a/src/register-configuration.h
+++ b/src/register-configuration.h
@@ -6,6 +6,7 @@
 #define V8_COMPILER_REGISTER_CONFIGURATION_H_
 
 #include "src/base/macros.h"
+#include "src/machine-type.h"
 
 namespace v8 {
 namespace internal {
@@ -21,6 +22,13 @@ class RegisterConfiguration {
   // until x87 TF supports all of the registers that Crankshaft does.
   enum CompilerSelector { CRANKSHAFT, TURBOFAN };
 
+  enum AliasingKind {
+    // Registers alias a single register of every other size (e.g. Intel).
+    OVERLAP,
+    // Registers alias two registers of the next smaller size (e.g. ARM).
+    COMBINE
+  };
+
   // Architecture independent maxes.
   static const int kMaxGeneralRegisters = 32;
   static const int kMaxFPRegisters = 32;
@@ -30,7 +38,7 @@ class RegisterConfiguration {
   RegisterConfiguration(int num_general_registers, int num_double_registers,
                         int num_allocatable_general_registers,
                         int num_allocatable_double_registers,
-                        int num_allocatable_aliased_double_registers,
+                        AliasingKind fp_aliasing_kind,
                         const int* allocatable_general_codes,
                         const int* allocatable_double_codes,
                         char const* const* general_names,
@@ -38,6 +46,7 @@ class RegisterConfiguration {
                         char const* const* double_names);
 
   int num_general_registers() const { return num_general_registers_; }
+  int num_float_registers() const { return num_float_registers_; }
   int num_double_registers() const { return num_double_registers_; }
   int num_allocatable_general_registers() const {
     return num_allocatable_general_registers_;
@@ -45,12 +54,10 @@ class RegisterConfiguration {
   int num_allocatable_double_registers() const {
     return num_allocatable_double_registers_;
   }
-  // TODO(turbofan): This is a temporary work-around required because our
-  // register allocator does not yet support the aliasing of single/double
-  // registers on ARM.
-  int num_allocatable_aliased_double_registers() const {
-    return num_allocatable_aliased_double_registers_;
+  int num_allocatable_float_registers() const {
+    return num_allocatable_float_registers_;
   }
+  AliasingKind fp_aliasing_kind() const { return fp_aliasing_kind_; }
   int32_t allocatable_general_codes_mask() const {
     return allocatable_general_codes_mask_;
   }
@@ -63,6 +70,9 @@ class RegisterConfiguration {
   int GetAllocatableDoubleCode(int index) const {
     return allocatable_double_codes_[index];
   }
+  int GetAllocatableFloatCode(int index) const {
+    return allocatable_float_codes_[index];
+  }
   const char* GetGeneralRegisterName(int code) const {
     return general_register_names_[code];
   }
@@ -78,17 +88,33 @@ class RegisterConfiguration {
   const int* allocatable_double_codes() const {
     return allocatable_double_codes_;
   }
+  const int* allocatable_float_codes() const {
+    return allocatable_float_codes_;
+  }
+
+  // Aliasing calculations for floating point registers, when fp_aliasing_kind
+  // is COMBINE. Assumes rep and other_rep are kFloat32, or kFloat64.
+  // Returns the number of aliases of rep/index of type other_rep/other_index,
+  // and their base index.
+  int GetAliases(MachineRepresentation rep, int index,
+                 MachineRepresentation other_rep, int* alias_base_index) const;
+  // Returns whether the two registers alias each other.
+  bool AreAliases(MachineRepresentation rep, int index,
+                  MachineRepresentation other_rep, int other_index) const;
 
  private:
   const int num_general_registers_;
+  int num_float_registers_;
   const int num_double_registers_;
   int num_allocatable_general_registers_;
   int num_allocatable_double_registers_;
-  int num_allocatable_aliased_double_registers_;
+  int num_allocatable_float_registers_;
+  AliasingKind fp_aliasing_kind_;
   int32_t allocatable_general_codes_mask_;
   int32_t allocatable_double_codes_mask_;
   const int* allocatable_general_codes_;
   const int* allocatable_double_codes_;
+  int allocatable_float_codes_[kMaxFPRegisters];
   char const* const* general_register_names_;
   char const* const* float_register_names_;
   char const* const* double_register_names_;