[AVX512] Remove leftover code for when i1 was a legal type from the fast isel load/store code.

[craig.topper]

Summary

I don't think we need this code anymore. It only existed because i1 used to be legal.

There's probably more unneeded code in fast isel still.

lib/Target/X86/X86FastISel.cpp

bool X86FastISel::X86FastEmitLoad(EVT VT, X86AddressMode &AM,
   bool IsNonTemporal = MMO && MMO->isNonTemporal();
 
   // Get opcode and regclass of the output for the given load instruction.
   unsigned Opc = 0;
   const TargetRegisterClass *RC = nullptr;
   switch (VT.getSimpleVT().SimpleTy) {
   default: return false;
   case MVT::i1:
-    // TODO: Support this properly.
-    if (Subtarget->hasAVX512())
-      return false;
-    LLVM_FALLTHROUGH;
   case MVT::i8:
     Opc = X86::MOV8rm;
     RC  = &X86::GR8RegClass;
     break;
   case MVT::i16:
     Opc = X86::MOV16rm;
     RC  = &X86::GR16RegClass;
     break;
bool X86FastISel::X86FastEmitStore(EVT VT, unsigned ValReg, bool ValIsKill,
   bool IsNonTemporal = MMO && MMO->isNonTemporal();
 
   // Get opcode and regclass of the output for the given store instruction.
   unsigned Opc = 0;
   switch (VT.getSimpleVT().SimpleTy) {
   case MVT::f80: // No f80 support yet.
   default: return false;
   case MVT::i1: {
-    // In case ValReg is a K register, COPY to a GPR
-    if (MRI.getRegClass(ValReg) == &X86::VK1RegClass) {
-      unsigned KValReg = ValReg;
-      ValReg = createResultReg(&X86::GR32RegClass);
-      BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DbgLoc,
-              TII.get(TargetOpcode::COPY), ValReg)
-          .addReg(KValReg);
-      ValReg = fastEmitInst_extractsubreg(MVT::i8, ValReg, /*Kill=*/true,
-                                          X86::sub_8bit);
-    }
     // Mask out all but lowest bit.
     unsigned AndResult = createResultReg(&X86::GR8RegClass);
     BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DbgLoc,
             TII.get(X86::AND8ri), AndResult)
       .addReg(ValReg, getKillRegState(ValIsKill)).addImm(1);
     ValReg = AndResult;
     LLVM_FALLTHROUGH; // handle i1 as i8.
   }