AVX-512: Fixed a bug in FMA instruction selection on KNL

The FMA instruction was selected from AVX2 set instead of AVX-512

Differential Revision: http://reviews.llvm.org/D16884

llvm-svn: 259792
diff --git a/llvm/lib/Target/X86/X86InstrFormats.td b/llvm/lib/Target/X86/X86InstrFormats.td
index e2fa295..5183adc 100644
--- a/llvm/lib/Target/X86/X86InstrFormats.td
+++ b/llvm/lib/Target/X86/X86InstrFormats.td
@@ -845,7 +845,7 @@
 class FMA3<bits<8> o, Format F, dag outs, dag ins, string asm,
            list<dag>pattern, InstrItinClass itin = NoItinerary>
       : I<o, F, outs, ins, asm, pattern, itin>, T8PD,
-        VEX_4V, FMASC, Requires<[HasFMA]>;
+        VEX_4V, FMASC, Requires<[HasFMA, NoVLX]>;
 
 // FMA4 Instruction Templates
 class FMA4<bits<8> o, Format F, dag outs, dag ins, string asm,