[mips] handle UImm16_AltRelaxed match type

Currently, UImm16_AltRelaxed match type is not handled in
MatchAndEmitInstruction() function, which may result in
llvm_unreachable() behavior.
This patch adds necessary case for this match type.

Patch by Aleksandar Beserminji.

Differential Revision: https://reviews.llvm.org/D37682

llvm-svn: 313077
diff --git a/llvm/lib/Target/Mips/AsmParser/MipsAsmParser.cpp b/llvm/lib/Target/Mips/AsmParser/MipsAsmParser.cpp
index 8716def..9fcf917 100644
--- a/llvm/lib/Target/Mips/AsmParser/MipsAsmParser.cpp
+++ b/llvm/lib/Target/Mips/AsmParser/MipsAsmParser.cpp
@@ -5122,6 +5122,7 @@
                  "expected 11-bit signed immediate");
   case Match_UImm16:
   case Match_UImm16_Relaxed:
+  case Match_UImm16_AltRelaxed:
     return Error(RefineErrorLoc(IDLoc, Operands, ErrorInfo),
                  "expected 16-bit unsigned immediate");
   case Match_SImm16: