[RISCV] Initial codegen support for ALU operations

This adds the minimum necessary to support codegen for simple ALU operations
on RV32. Prolog and epilog insertion, support for memory operations etc etc 
follow in future patches.

Leave guessInstructionProperties=1 until https://reviews.llvm.org/D37065 is 
reviewed and lands.

Differential Revision: https://reviews.llvm.org/D29933


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@316188 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 63 insertions, 0 deletions

diff --git a/lib/Target/RISCV/RISCVISelDAGToDAG.cpp b/lib/Target/RISCV/RISCVISelDAGToDAG.cpp
new file mode 100644
index 00000000000..78f61fa4184
--- /dev/null
+++ b/lib/Target/RISCV/RISCVISelDAGToDAG.cpp
@@ -0,0 +1,63 @@
+//===-- RISCVISelDAGToDAG.cpp - A dag to dag inst selector for RISCV ------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file defines an instruction selector for the RISCV target.
+//
+//===----------------------------------------------------------------------===//
+
+#include "RISCV.h"
+#include "MCTargetDesc/RISCVMCTargetDesc.h"
+#include "RISCVTargetMachine.h"
+#include "llvm/CodeGen/SelectionDAGISel.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/MathExtras.h"
+#include "llvm/Support/raw_ostream.h"
+using namespace llvm;
+
+#define DEBUG_TYPE "riscv-isel"
+
+// RISCV-specific code to select RISCV machine instructions for
+// SelectionDAG operations.
+namespace {
+class RISCVDAGToDAGISel final : public SelectionDAGISel {
+public:
+  explicit RISCVDAGToDAGISel(RISCVTargetMachine &TargetMachine)
+      : SelectionDAGISel(TargetMachine) {}
+
+  StringRef getPassName() const override {
+    return "RISCV DAG->DAG Pattern Instruction Selection";
+  }
+
+  void Select(SDNode *Node) override;
+
+// Include the pieces autogenerated from the target description.
+#include "RISCVGenDAGISel.inc"
+};
+}
+
+void RISCVDAGToDAGISel::Select(SDNode *Node) {
+  // Dump information about the Node being selected.
+  DEBUG(dbgs() << "Selecting: "; Node->dump(CurDAG); dbgs() << "\n");
+
+  // If we have a custom node, we have already selected
+  if (Node->isMachineOpcode()) {
+    DEBUG(dbgs() << "== "; Node->dump(CurDAG); dbgs() << "\n");
+    Node->setNodeId(-1);
+    return;
+  }
+
+  // Select the default instruction.
+  SelectCode(Node);
+}
+
+// This pass converts a legalized DAG into a RISCV-specific DAG, ready
+// for instruction scheduling.
+FunctionPass *llvm::createRISCVISelDag(RISCVTargetMachine &TM) {
+  return new RISCVDAGToDAGISel(TM);
+}