ARM64: Move THR to R26 so special registers are contiguous.

runtime/vm/constants_arm64.h

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #ifndef VM_CONSTANTS_ARM64_H_
 #define VM_CONSTANTS_ARM64_H_
 
 #include "platform/assert.h"
 
 namespace dart {
@@ skipping 12 matching lines @@
   R10 = 10,
   R11 = 11,
   R12 = 12,
   R13 = 13,
   R14 = 14,
   R15 = 15,  // SP in Dart code.
   R16 = 16,  // IP0 aka TMP
   R17 = 17,  // IP1 aka TMP2
   R18 = 18,  // "platform register" on iOS.
   R19 = 19,
-  R20 = 20,  // THR
+  R20 = 20,
   R21 = 21,
   R22 = 22,
   R23 = 23,
   R24 = 24,
   R25 = 25,
-  R26 = 26,
+  R26 = 26,  // THR
   R27 = 27,  // PP
   R28 = 28,  // CTX
   R29 = 29,  // FP
   R30 = 30,  // LR
   R31 = 31,  // ZR, CSP
   kNumberOfCpuRegisters = 32,
   kNoRegister = -1,
 
   // These registers both use the encoding R31, but to avoid mistakes we give
   // them different values, and then translate before encoding.
@@ skipping 59 matching lines @@
 const Register TMP = R16;  // Used as scratch register by assembler.
 const Register TMP2 = R17;
 const Register CTX = R28;  // Location of current context at method entry.
 const Register PP = R27;  // Caches object pool pointer in generated code.
 const Register CODE_REG = R24;
 const Register FPREG = FP;  // Frame pointer register.
 const Register SPREG = R15;  // Stack pointer register.
 const Register LRREG = LR;  // Link register.
 const Register ICREG = R5;  // IC data register.
 const Register ARGS_DESC_REG = R4;  // Arguments descriptor register.
-const Register THR = R20;  // Caches current thread in generated code.
+const Register THR = R26;  // Caches current thread in generated code.
 
 
 // Exception object is passed in this register to the catch handlers when an
 // exception is thrown.
 const Register kExceptionObjectReg = R0;
 
 // Stack trace object is passed in this register to the catch handlers when
 // an exception is thrown.
 const Register kStackTraceObjectReg = R1;
 
@@ skipping 944 matching lines @@
   static Instr* At(uword pc) { return reinterpret_cast<Instr*>(pc); }
 
  private:
   DISALLOW_ALLOCATION();
   DISALLOW_IMPLICIT_CONSTRUCTORS(Instr);
 };
 
 }  // namespace dart
 
 #endif  // VM_CONSTANTS_ARM64_H_