A64: Add and use a double register which holds the 0.0 value.

src/a64/assembler-a64.h

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 246 matching lines @@
     return IsValidFPRegister();
   }
 
   static FPRegister SRegFromCode(unsigned code);
   static FPRegister DRegFromCode(unsigned code);
 
   // Start of V8 compatibility section ---------------------
   static const int kMaxNumRegisters = kNumberOfFPRegisters;
 
   // Crankshaft can use all the FP registers except:
-  //   - d29 which is used in crankshaft as a double scratch register
-  //   - d30 which is used to keep the 0 double value
+  //   - d15 which is used to keep the 0 double value
+  //   - d30 which is used in crankshaft as a double scratch register
   //   - d31 which is used in the MacroAssembler as a double scratch register
-  static const int kNumReservedRegisters = 3;
+  static const unsigned kAllocatableLowRangeBegin = 0;
+  static const unsigned kAllocatableLowRangeEnd = 14;
+  static const unsigned kAllocatableHighRangeBegin = 16;
+  static const unsigned kAllocatableHighRangeEnd = 29;
+
+  static const RegList kAllocatableFPRegisters = 0x3fff7fff;
+
+  // Gap between low and high ranges.
+  static const int kAllocatableRangeGapSize =
+      (kAllocatableHighRangeBegin - kAllocatableLowRangeEnd) - 1;
+
   static const int kMaxNumAllocatableRegisters =
-      kNumberOfFPRegisters - kNumReservedRegisters;
+      (kAllocatableLowRangeEnd - kAllocatableLowRangeBegin + 1) +
+      (kAllocatableHighRangeEnd - kAllocatableHighRangeBegin + 1);
   static int NumAllocatableRegisters() { return kMaxNumAllocatableRegisters; }
-  static const RegList kAllocatableFPRegisters =
-      (1 << kMaxNumAllocatableRegisters) - 1;
 
-  static FPRegister FromAllocationIndex(int index) {
-    ASSERT((index >= 0) && (index < NumAllocatableRegisters()));
-    return from_code(index);
+  // Return true if the register is one that crankshaft can allocate.
+  bool IsAllocatable() const {
+    return (Bit() & kAllocatableFPRegisters) != 0;
+  }
+
+  static FPRegister FromAllocationIndex(unsigned int index) {
+    ASSERT(index < static_cast<unsigned>(NumAllocatableRegisters()));
+
+    return (index <= kAllocatableLowRangeEnd)
+        ? from_code(index)
+        : from_code(index + kAllocatableRangeGapSize);
   }
 
   static const char* AllocationIndexToString(int index) {
     ASSERT((index >= 0) && (index < NumAllocatableRegisters()));
+    ASSERT((kAllocatableLowRangeBegin == 0) &&
+           (kAllocatableLowRangeEnd == 14) &&
+           (kAllocatableHighRangeBegin == 16) &&
+           (kAllocatableHighRangeEnd == 29));
     const char* const names[] = {
       "d0", "d1", "d2", "d3", "d4", "d5", "d6", "d7",
-      "d8", "d9", "d10", "d11", "d12", "d13", "d14", "d15",
+      "d8", "d9", "d10", "d11", "d12", "d13", "d14",
       "d16", "d17", "d18", "d19", "d20", "d21", "d22", "d23",
-      "d24", "d25", "d26", "d27", "d28",
+      "d24", "d25", "d26", "d27", "d28", "d29"
     };
     return names[index];
   }
 
   static int ToAllocationIndex(FPRegister reg) {
-    int code = reg.code();
-    ASSERT(code < NumAllocatableRegisters());
-    return code;
+    ASSERT(reg.IsAllocatable());
+    unsigned code = reg.code();
+
+    return (code <= kAllocatableLowRangeEnd)
+        ? code
+        : code - kAllocatableRangeGapSize;
   }
 
   static FPRegister from_code(int code) {
     // Always return a D register.
     return FPRegister::Create(code, kDRegSize);
   }
   // End of V8 compatibility section -----------------------
 };
 
 
@@ skipping 61 matching lines @@
 // We chose x28 because it is contiguous with the other specific purpose
 // registers.
 STATIC_ASSERT(kJSSPCode == 28);
 ALIAS_REGISTER(Register, jssp, x28);
 ALIAS_REGISTER(Register, wjssp, w28);
 ALIAS_REGISTER(Register, fp, x29);
 ALIAS_REGISTER(Register, lr, x30);
 ALIAS_REGISTER(Register, xzr, x31);
 ALIAS_REGISTER(Register, wzr, w31);
 
+// Keeps the 0 double value.
+ALIAS_REGISTER(FPRegister, fp_zero, d15);
 // Crankshaft double scratch register.
-ALIAS_REGISTER(FPRegister, crankshaft_fp_scratch, d29);
-// Keeps the 0 double value.
-ALIAS_REGISTER(FPRegister, fp_zero, d30);
+ALIAS_REGISTER(FPRegister, crankshaft_fp_scratch, d30);
 // MacroAssembler double scratch register.
 ALIAS_REGISTER(FPRegister, fp_scratch, d31);
 
 #undef ALIAS_REGISTER
 
 
 Register GetAllocatableRegisterThatIsNotOneOf(Register reg1,
                                               Register reg2 = NoReg,
                                               Register reg3 = NoReg,
                                               Register reg4 = NoReg);
@@ skipping 1760 matching lines @@
 class EnsureSpace BASE_EMBEDDED {
  public:
   explicit EnsureSpace(Assembler* assembler) {
     assembler->CheckBuffer();
   }
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_A64_ASSEMBLER_A64_H_