[ARM/AArch64] Support FP16 +fp16fml instructions

Add +fp16fml feature for new FP16 instructions, which are a
mandatory part of FP16 from v8.4-A and an optional part of FP16
from v8.2-A. It doesn't seem to be possible to model this in
LLVM, but the relationship between the options is handled by
the related clang patch.

In keeping with what I think is the usual practice, the fp16fml
extension is accepted regardless of base architecture version.

Builds on/replaces Sjoerd Meijer's patch to add these instructions at
https://reviews.llvm.org/D49839.

Differential Revision: https://reviews.llvm.org/D50228

llvm-svn: 340013
diff --git a/llvm/lib/Target/ARM/AsmParser/ARMAsmParser.cpp b/llvm/lib/Target/ARM/AsmParser/ARMAsmParser.cpp
index a5fbbbf..da6296a 100644
--- a/llvm/lib/Target/ARM/AsmParser/ARMAsmParser.cpp
+++ b/llvm/lib/Target/ARM/AsmParser/ARMAsmParser.cpp
@@ -5626,7 +5626,8 @@
       Mnemonic.startswith("vsel") || Mnemonic == "vins" || Mnemonic == "vmovx" ||
       Mnemonic == "bxns"  || Mnemonic == "blxns" ||
       Mnemonic == "vudot" || Mnemonic == "vsdot" ||
-      Mnemonic == "vcmla" || Mnemonic == "vcadd")
+      Mnemonic == "vcmla" || Mnemonic == "vcadd" ||
+      Mnemonic == "vfmal" || Mnemonic == "vfmsl")
     return Mnemonic;
 
   // First, split out any predication code. Ignore mnemonics we know aren't
@@ -5716,7 +5717,8 @@
       (FullInst.startswith("vmull") && FullInst.endswith(".p64")) ||
       Mnemonic == "vmovx" || Mnemonic == "vins" ||
       Mnemonic == "vudot" || Mnemonic == "vsdot" ||
-      Mnemonic == "vcmla" || Mnemonic == "vcadd") {
+      Mnemonic == "vcmla" || Mnemonic == "vcadd" ||
+      Mnemonic == "vfmal" || Mnemonic == "vfmsl") {
     // These mnemonics are never predicable
     CanAcceptPredicationCode = false;
   } else if (!isThumb()) {