1 files changed, 91 insertions, 0 deletions
diff --git a/lib/CodeGen/MIRVRegNamerUtils.h b/lib/CodeGen/MIRVRegNamerUtils.h
new file mode 100644
index 000000000000..c5b52a968538
--- /dev/null
+++ b/lib/CodeGen/MIRVRegNamerUtils.h
@@ -0,0 +1,91 @@
+
+//===------------ MIRVRegNamerUtils.h - MIR VReg Renaming Utilities -------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// The purpose of these utilities is to abstract out parts of the MIRCanon pass
+// that are responsible for renaming virtual registers with the purpose of
+// sharing code with a MIRVRegNamer pass that could be the analog of the
+// opt -instnamer pass.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIB_CODEGEN_MIRVREGNAMERUTILS_H
+#define LLVM_LIB_CODEGEN_MIRVREGNAMERUTILS_H
+
+#include "llvm/ADT/PostOrderIterator.h"
+#include "llvm/ADT/STLExtras.h"
+#include "llvm/CodeGen/MachineFunctionPass.h"
+#include "llvm/CodeGen/MachineInstrBuilder.h"
+#include "llvm/CodeGen/MachineRegisterInfo.h"
+#include "llvm/CodeGen/Passes.h"
+#include "llvm/Support/raw_ostream.h"
+
+#include <queue>
+
+namespace llvm {
+
+/// NamedVRegCursor - The cursor is an object that keeps track of what the next
+/// vreg name should be. It does book keeping to determine when to skip the
+/// index value and by how much, or if the next vreg name should be an increment
+/// from the previous.
+class NamedVRegCursor {
+  MachineRegisterInfo &MRI;
+
+  /// virtualVRegNumber - Book keeping of the last vreg position.
+  unsigned virtualVRegNumber;
+
+  /// SkipGapSize - Used to calculate a modulo amount to skip by after every
+  /// sequence of instructions starting from a given side-effecting
+  /// MachineInstruction for a given MachineBasicBlock. The general idea is that
+  /// for a given program compiled with two different opt pipelines, there
+  /// shouldn't be greater than SkipGapSize difference in how many vregs are in
+  /// play between the two and for every def-use graph of vregs we rename we
+  /// will round up to the next SkipGapSize'th number so that we have a high
+  /// change of landing on the same name for two given matching side-effects
+  /// for the two compilation outcomes.
+  const unsigned SkipGapSize;
+
+  /// RenamedInOtherBB - VRegs that we already renamed: ie breadcrumbs.
+  std::vector<Register> RenamedInOtherBB;
+
+public:
+  NamedVRegCursor() = delete;
+  /// 1000 for the SkipGapSize was a good heuristic at the time of the writing
+  /// of the MIRCanonicalizerPass. Adjust as needed.
+  NamedVRegCursor(MachineRegisterInfo &MRI, unsigned SkipGapSize = 1000)
+      : MRI(MRI), virtualVRegNumber(0), SkipGapSize(SkipGapSize) {}
+
+  /// SkipGapSize - Skips modulo a gap value of indices. Indices are used to
+  /// produce the next vreg name.
+  void skipVRegs();
+
+  unsigned getVirtualVReg() const { return virtualVRegNumber; }
+
+  /// incrementVirtualVReg - This increments an index value that us used to
+  /// create a new vreg name. This is not a Register.
+  unsigned incrementVirtualVReg(unsigned incr = 1) {
+    virtualVRegNumber += incr;
+    return virtualVRegNumber;
+  }
+
+  /// createVirtualRegister - Given an existing vreg, create a named vreg to
+  /// take its place.
+  unsigned createVirtualRegister(unsigned VReg);
+
+  /// renameVRegs - For a given MachineBasicBlock, scan for side-effecting
+  /// instructions, walk the def-use from each side-effecting root (in sorted
+  /// root order) and rename the encountered vregs in the def-use graph in a
+  /// canonical ordering. This method maintains book keeping for which vregs
+  /// were already renamed in RenamedInOtherBB.
+  // @return changed
+  bool renameVRegs(MachineBasicBlock *MBB);
+};
+
+} // namespace llvm
+
+#endif