ARM64: Use the shifter operand to merge in previous shift instructions.

src/arm64/lithium-codegen-arm64.h

Index: src/arm64/lithium-codegen-arm64.h
diff --git a/src/arm64/lithium-codegen-arm64.h b/src/arm64/lithium-codegen-arm64.h
index 4aea1fbcd1ce5f6cc0f715ce7ca393b8b752642f..8cae5b0496e893d7756ba8313e983dfa627edde3 100644
--- a/src/arm64/lithium-codegen-arm64.h
+++ b/src/arm64/lithium-codegen-arm64.h
@@ -81,6 +81,7 @@ class LCodeGen: public LCodeGenBase {
   // information on it.
   void FinishCode(Handle<Code> code);
 
+  enum IntegerSignedness { SIGNED_INT32, UNSIGNED_INT32 };
   // Support for converting LOperands to assembler types.
   // LOperand must be a register.
   Register ToRegister(LOperand* op) const;
@@ -93,6 +94,25 @@ class LCodeGen: public LCodeGenBase {
                           StackMode stack_mode = kCanUseStackPointer) const;
   Handle<Object> ToHandle(LConstantOperand* op) const;
 
+  template<class LI>
+  Operand ToShiftedRightOperand32I(LOperand* right,
+                                   LI* shift_info) {
+    return ToShiftedRightOperand32(right, shift_info, SIGNED_INT32);
+  }
+  template<class LI>
+  Operand ToShiftedRightOperand32U(LOperand* right,
+                                   LI* shift_info) {
+    return ToShiftedRightOperand32(right, shift_info, UNSIGNED_INT32);
+  }
+  template<class LI>
+  Operand ToShiftedRightOperand32(LOperand* right,
+                                  LI* shift_info,
+                                  IntegerSignedness signedness);
+
+  int JSShiftAmountFromLConstant(LOperand* constant) {
+    return ToInteger32(LConstantOperand::cast(constant)) & 0x1f;
+  }
+
   // TODO(jbramley): Examine these helpers and check that they make sense.
   // IsInteger32Constant returns true for smi constants, for example.
   bool IsInteger32Constant(LConstantOperand* op) const;
@@ -122,7 +142,6 @@ class LCodeGen: public LCodeGenBase {
                                Label* exit,
                                Label* allocation_entry);
 
-  enum IntegerSignedness { SIGNED_INT32, UNSIGNED_INT32 };
   void DoDeferredNumberTagU(LInstruction* instr,
                             LOperand* value,
                             LOperand* temp1,