[RISCV] Initial support for function calls

Note that this is just enough for simple function call examples to generate 
working code. Support for varargs etc follows in future patches.

Differential Revision: https://reviews.llvm.org/D29936

llvm-svn: 317691
diff --git a/llvm/lib/Target/RISCV/RISCVInstrInfo.cpp b/llvm/lib/Target/RISCV/RISCVInstrInfo.cpp
index 63178bb..5b4f4fc 100644
--- a/llvm/lib/Target/RISCV/RISCVInstrInfo.cpp
+++ b/llvm/lib/Target/RISCV/RISCVInstrInfo.cpp
@@ -28,7 +28,8 @@
 
 using namespace llvm;
 
-RISCVInstrInfo::RISCVInstrInfo() : RISCVGenInstrInfo() {}
+RISCVInstrInfo::RISCVInstrInfo()
+    : RISCVGenInstrInfo(RISCV::ADJCALLSTACKDOWN, RISCV::ADJCALLSTACKUP) {}
 
 void RISCVInstrInfo::copyPhysReg(MachineBasicBlock &MBB,
                                  MachineBasicBlock::iterator MBBI,