ARM64: Support arbitrary offset in load/store pair.

src/arm64/assembler-arm64.h

Index: src/arm64/assembler-arm64.h
diff --git a/src/arm64/assembler-arm64.h b/src/arm64/assembler-arm64.h
index e16ea875c47288bfa2d51e1c36ac13e3db91c251..d0effa79a0fa6651307bc46e2f937bc608daabea 100644
--- a/src/arm64/assembler-arm64.h
+++ b/src/arm64/assembler-arm64.h
@@ -1945,6 +1945,10 @@ class Assembler : public AssemblerBase {
   static bool IsImmLSUnscaled(ptrdiff_t offset);
   static bool IsImmLSScaled(ptrdiff_t offset, LSDataSize size);
 
+  void LoadStorePair(const CPURegister& rt, const CPURegister& rt2,
+                     const MemOperand& addr, LoadStorePairOp op);
+  static bool IsImmLSPair(ptrdiff_t offset, LSDataSize size);
+
   void Logical(const Register& rd,
                const Register& rn,
                const Operand& operand,
@@ -2027,10 +2031,6 @@ class Assembler : public AssemblerBase {
                                 const Operand& operand,
                                 FlagsUpdate S,
                                 Instr op);
-  void LoadStorePair(const CPURegister& rt,
-                     const CPURegister& rt2,
-                     const MemOperand& addr,
-                     LoadStorePairOp op);
   void LoadStorePairNonTemporal(const CPURegister& rt,
                                 const CPURegister& rt2,
                                 const MemOperand& addr,