[AVR] Redefine the 'LSL' instruction as an alias of 'ADD'

The 'LSL Rd' instruction is equivalent to 'ADD Rd, Rd'.

llvm-svn: 341278
diff --git a/llvm/lib/Target/AVR/AVRISelLowering.cpp b/llvm/lib/Target/AVR/AVRISelLowering.cpp
index 43f54d8..57fc978 100644
--- a/llvm/lib/Target/AVR/AVRISelLowering.cpp
+++ b/llvm/lib/Target/AVR/AVRISelLowering.cpp
@@ -1441,8 +1441,9 @@
   default:
     llvm_unreachable("Invalid shift opcode!");
   case AVR::Lsl8:
-    Opc = AVR::LSLRd;
+    Opc = AVR::ADDRdRr; // LSL is an alias of ADD Rd, Rd
     RC = &AVR::GPR8RegClass;
+    HasRepeatedOperand = true;
     break;
   case AVR::Lsl16:
     Opc = AVR::LSLWRd;