[mips][FastISel] Fix call lowering by bailing out on "fastcc" calls.

Summary:
Currently, we support only the MIPS O32 ABI calling convention for call
lowering. With this change we avoid using the O32 calling convetion for
lowering calls marked as using the fast calling convention.

Reviewers: dsanders

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D11515

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@243485 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Target/Mips/MipsFastISel.cpp

@@ -1245,6 +1245,10 @@ bool MipsFastISel::fastLowerCall(CallLoweringInfo &CLI) {
   const Value *Callee = CLI.Callee;
   MCSymbol *Symbol = CLI.Symbol;
 
+  // Do not handle FastCC.
+  if (CC == CallingConv::Fast)
+    return false;
+
   // Allow SelectionDAG isel to handle tail calls.
   if (IsTailCall)
     return false;
@@ -1422,6 +1426,11 @@ bool MipsFastISel::selectRet(const Instruction *I) {
 
   if (Ret->getNumOperands() > 0) {
     CallingConv::ID CC = F.getCallingConv();
+
+    // Do not handle FastCC.
+    if (CC == CallingConv::Fast)
+      return false;
+
     SmallVector<ISD::OutputArg, 4> Outs;
     GetReturnInfo(F.getReturnType(), F.getAttributes(), Outs, TLI, DL);