[NFC] Referencing manual for reason why subregbit is checked

llvm-svn: 259380

diff --git a/llvm/lib/Target/Hexagon/Disassembler/HexagonDisassembler.cpp b/llvm/lib/Target/Hexagon/Disassembler/HexagonDisassembler.cpp
index fc39d09..95352fc 100644 (file)
--- a/llvm/lib/Target/Hexagon/Disassembler/HexagonDisassembler.cpp
+++ b/llvm/lib/Target/Hexagon/Disassembler/HexagonDisassembler.cpp
@@ -382,7 +382,8 @@ DecodeStatus HexagonDisassembler::getSingleInstruction(
       if (Producer >= Hexagon::W0 && Producer <= Hexagon::W15)
         Producer = ((Producer - Hexagon::W0) << 1) + SubregBit + Hexagon::V0;
       else if (SubregBit)
-        // Subreg bit should not be set for non-doublevector newvalue producers
+               // Hexagon PRM 10.11 New-value operands
+               // Nt[0] is reserved and should always be encoded as zero.
         return MCDisassembler::Fail;
       assert(Producer != Hexagon::NoRegister);
       MCO.setReg(Producer);