ARM, ARM64: Optimize array copy

src/arm64/macro-assembler-arm64.cc

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/v8.h"
 
 #if V8_TARGET_ARCH_ARM64
 
 #include "src/bootstrapper.h"
 #include "src/codegen.h"
@@ skipping 416 matching lines @@
   if (operand.NeedsRelocation(this)) {
     UseScratchRegisterScope temps(this);
     Register temp = temps.AcquireX();
     Ldr(temp, operand.immediate());
     AddSubMacro(rd, rn, temp, S, op);
   } else if ((operand.IsImmediate() &&
               !IsImmAddSub(operand.ImmediateValue()))      ||
              (rn.IsZero() && !operand.IsShiftedRegister()) ||
              (operand.IsShiftedRegister() && (operand.shift() == ROR))) {
     UseScratchRegisterScope temps(this);
-    Register temp = temps.AcquireSameSizeAs(rn);
+    // Use rd as a temp if possible.
+    Register temp =
+        (rd.Is(rn) || rd.IsSP() || rd.IsZero()) ?
+            temps.AcquireSameSizeAs(rn) : rd;
     Mov(temp, operand);
     AddSub(rd, rn, temp, S, op);
   } else {
     AddSub(rd, rn, operand, S, op);
   }
 }
 
 
 void MacroAssembler::AddSubWithCarryMacro(const Register& rd,
                                           const Register& rn,
@@ skipping 4846 matching lines @@
   }
 }
 
 
 #undef __
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_ARM64