[mips][FastISel] Disable code generation for unsupported targets through FastISel.

[vkalintiris]

Summary

Previously, we would check whether the target is supported or not, only in
fastSelectInstruction(). This means that 64-bit targets could use FastISel too.
We fix this by checking every overridden method of the FastISel class and
by falling back to SelectionDAG if the target isn't supported. This change
should have been committed along with r243638, but somehow I missed it.

[dsanders]

LGTM. Thanks

[dsanders]

We should also merge this to the 3.7 release to avoid regressing -O0 for mips64.

Hans: Ok to merge?

[hans]

In D11755#217594, @dsanders wrote:

We should also merge this to the 3.7 release to avoid regressing -O0 for mips64.

Hans: Ok to merge?

Yes. I've merged it in r244092.

[dsanders]

Thanks

lib/Target/Mips/MipsFastISel.cpp

unsigned MipsFastISel::emitLogicalOp(unsigned ISDOpc, MVT RetVT,
   if (!RHSReg)
     return 0;
 
   emitInst(Opc, ResultReg).addReg(LHSReg).addReg(RHSReg);
   return ResultReg;
 }
 
 unsigned MipsFastISel::fastMaterializeAlloca(const AllocaInst *AI) {
+  if (!TargetSupported)
+    return 0;
+
   assert(TLI.getValueType(DL, AI->getType(), true) == MVT::i32 &&
          "Alloca should always return a pointer.");
 
   DenseMap<const AllocaInst *, int>::iterator SI =
       FuncInfo.StaticAllocaMap.find(AI);
 
   if (SI != FuncInfo.StaticAllocaMap.end()) {
     unsigned ResultReg = createResultReg(&Mips::GPR32RegClass);
emitInst(Mips::LW, DestReg)
       .addReg(MFI->getGlobalBaseReg())
       .addSym(Sym, MipsII::MO_GOT);
   return DestReg;
 }
 
 // Materialize a constant into a register, and return the register
 // number (or zero if we failed to handle it).
 unsigned MipsFastISel::fastMaterializeConstant(const Constant *C) {
+  if (!TargetSupported)
+    return 0;
+
   EVT CEVT = TLI.getValueType(DL, C->getType(), true);
 
   // Only handle simple types.
   if (!CEVT.isSimple())
     return 0;
   MVT VT = CEVT.getSimpleVT();
 
   if (const ConstantFP *CFP = dyn_cast<ConstantFP>(C))
if (RetVT != MVT::isVoid) {
 
     CLI.ResultReg = ResultReg;
     CLI.NumResultRegs = 1;
   }
   return true;
 }
 
 bool MipsFastISel::fastLowerCall(CallLoweringInfo &CLI) {
+  if (!TargetSupported)
+    return false;
+
   CallingConv::ID CC = CLI.CallConv;
   bool IsTailCall = CLI.IsTailCall;
   bool IsVarArg = CLI.IsVarArg;
   const Value *Callee = CLI.Callee;
   MCSymbol *Symbol = CLI.Symbol;
 
   // Do not handle FastCC.
   if (CC == CallingConv::Fast)
bool MipsFastISel::fastLowerCall(CallLoweringInfo &CLI) {
 
   CLI.Call = MIB;
 
   // Finish off the call including any return values.
   return finishCall(CLI, RetVT, NumBytes);
 }
 
 bool MipsFastISel::fastLowerIntrinsicCall(const IntrinsicInst *II) {
+  if (!TargetSupported)
+    return false;
+
   switch (II->getIntrinsicID()) {
   default:
     return false;
   case Intrinsic::bswap: {
     Type *RetTy = II->getCalledFunction()->getReturnType();
 
     MVT VT;
     if (!isTypeSupported(RetTy, VT))