[RISCV] Add stub backend

This contains just enough for lib/Target/RISCV to compile. Notably a basic 
RISCVTargetMachine and RISCVTargetInfo. At this point you can attempt llc 
-march=riscv32 myinput.ll and will find it fails due to the lack of 
MCAsmInfo.

See http://lists.llvm.org/pipermail/llvm-dev/2016-August/103748.html for 
further discussion

Differential Revision: https://reviews.llvm.org/D23560

llvm-svn: 285712

1 files changed, 35 insertions, 0 deletions

diff --git a/llvm/lib/Target/RISCV/TargetInfo/RISCVTargetInfo.cpp b/llvm/lib/Target/RISCV/TargetInfo/RISCVTargetInfo.cpp
new file mode 100644
index 00000000000..3cb657a9978
--- /dev/null
+++ b/llvm/lib/Target/RISCV/TargetInfo/RISCVTargetInfo.cpp
@@ -0,0 +1,35 @@
+//===-- RISCVTargetInfo.cpp - RISCV Target Implementation -----------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Support/TargetRegistry.h"
+using namespace llvm;
+
+namespace llvm {
+Target &getTheRISCV32Target() {
+  static Target TheRISCV32Target;
+  return TheRISCV32Target;
+}
+
+Target &getTheRISCV64Target() {
+  static Target TheRISCV64Target;
+  return TheRISCV64Target;
+}
+}
+
+extern "C" void LLVMInitializeRISCVTargetInfo() {
+  RegisterTarget<Triple::riscv32> X(getTheRISCV32Target(), "riscv32",
+                                    "32-bit RISC-V");
+  RegisterTarget<Triple::riscv64> Y(getTheRISCV64Target(), "riscv64",
+                                    "64-bit RISC-V");
+}
+
+// FIXME: Temporary stub - this function must be defined for linking
+// to succeed and will be called unconditionally by llc, so must be a no-op.
+// Remove once this function is properly implemented.
+extern "C" void LLVMInitializeRISCVTargetMC() {}