[Xtensa][MC] Add _bnez.n and _beqz.n alias instructions

Author: sstefan1

llvm/lib/Target/Xtensa/XtensaInstrInfo.td

@@ -804,6 +804,9 @@ let isBranch = 1, isTerminator = 1 in {
   }
 }
 
+def : InstAlias<"_beqz.n\t$s, $target", (BEQZ_N AR:$s, brtarget:$target)>, Requires<[HasDensity]>;
+def : InstAlias<"_bnez.n\t$s, $target", (BNEZ_N AR:$s, brtarget:$target)>, Requires<[HasDensity]>;
+
 def ILL_N : RRRN_Inst<0x0D, (outs), (ins),
                      "ill.n", []>, Requires<[HasDensity]> {
   let r = 0xF;

llvm/test/MC/Xtensa/code_density.s

@@ -29,6 +29,16 @@ beqz.n  a3, LBL1
 # CHECK: encoding: [0xcc'A',0x03'A']
 bnez.n  a3, LBL1
 
+# Instruction format BRI6
+# CHECK-INST:  bnez.n    a5, LBL0
+# CHECK: encoding: [0xcc'A',0x05'A']
+_bnez.n a5, LBL0
+
+# Instruction format BRI6
+# CHECK-INST:  beqz.n    a5, LBL0
+# CHECK: encoding: [0x8c'A',0x05'A']
+_beqz.n a5, LBL0
+
 # Instruction format RRRN
 # CHECK-INST: ill.n
 # CHECK: encoding: [0x6d,0xf0]