[MSP430] Allow functions to be defined with MSP430_BUILTIN CC

[LemonBoy]

Summary

Small patch to stop llc from triggering an error upon seeing a cc94 function.
The included test ensures the arguments and return values are correctly placed in the registers mandated by the EABI P3.3.5.

[LemonBoy]

PENG

llvm/lib/Target/MSP430/MSP430ISelLowering.cpp

 SDValue MSP430TargetLowering::LowerFormalArguments(
     SDValue Chain, CallingConv::ID CallConv, bool isVarArg,
     const SmallVectorImpl<ISD::InputArg> &Ins, const SDLoc &dl,
     SelectionDAG &DAG, SmallVectorImpl<SDValue> &InVals) const {
 
   switch (CallConv) {
   default:
     report_fatal_error("Unsupported calling convention");
+  case CallingConv::MSP430_BUILTIN:
   case CallingConv::C:
   case CallingConv::Fast:
     return LowerCCCArguments(Chain, CallConv, isVarArg, Ins, dl, DAG, InVals);
   case CallingConv::MSP430_INTR:
     if (Ins.empty())
       return Chain;
     report_fatal_error("ISRs cannot have arguments");
   }

llvm/test/CodeGen/MSP430/cc_args.ll

 ; CHECK: mov  &g_i64_2+2, r13
 ; CHECK: mov  &g_i64_2+4, r14
 ; CHECK: mov  &g_i64_2+6, r15
 ; CHECK: call #__mspabi_divlli
   %3 = sdiv i64 %1, %2
   ret i64 %3
 }
 
+define cc94 i64 @helper_i64(i64 %a, i64 %b) {
+; CHECK-LABEL: helper_i64:
+; CHECK: mov  r15, &g_i64_2+6
+; CHECK-NEXT: mov r14, &g_i64_2+4
+; CHECK-NEXT: mov r13, &g_i64_2+2
+; CHECK-NEXT: mov r12, &g_i64_2
+; CHECK-NEXT: mov r11, &g_i64+6
+; CHECK-NEXT: mov r10, &g_i64+4
+; CHECK-NEXT: mov r9, &g_i64+2
+; CHECK-NEXT: mov r8, &g_i64
+; CHECK-NEXT: mov #30600, r12
+; CHECK-NEXT: mov #21862, r13
+; CHECK-NEXT: mov #13124, r14
+; CHECK-NEXT: mov #4386, r15
+; CHECK-NEXT: ret
+  store i64 %a, i64* @g_i64, align 2
+  store i64 %b, i64* @g_i64_2, align 2
+  ret i64 1234605616436508552
+}
+
 attributes #0 = { nounwind "less-precise-fpmad"="false" "frame-pointer"="all" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "unsafe-fp-math"="false" "use-soft-float"="false" }