[llvm] [Hexagon] Add Hexagon Copy Hoisting pass (PR #89313)

[Krzysztof Parzyszek via llvm-commits]

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@@ -0,0 +1,291 @@
+//===--------- HexagonCopyHoisting.cpp - Hexagon Copy Hoisting  ----------===//
+//
+// 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 this pass is to move the copy instructions that are
+// present in all the successor of a basic block (BB) to the end of BB.
+//===----------------------------------------------------------------------===//
+
+#include "HexagonTargetMachine.h"
+#include "llvm/ADT/PostOrderIterator.h"
+#include "llvm/ADT/SmallString.h"
+#include "llvm/ADT/StringMap.h"
+#include "llvm/ADT/StringRef.h"
+#include "llvm/ADT/Twine.h"
+#include "llvm/CodeGen/LiveInterval.h"
+#include "llvm/CodeGen/LiveIntervals.h"
+#include "llvm/CodeGen/MachineDominators.h"
+#include "llvm/CodeGen/MachineInstrBuilder.h"
+#include "llvm/CodeGen/MachineRegisterInfo.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/Support/Debug.h"
+
+#define DEBUG_TYPE "CopyHoist"
+
+using namespace llvm;
+
+static cl::opt<std::string> CPHoistFn("cphoistfn", cl::Hidden, cl::desc(""),
+                                      cl::init(""));
+
+namespace llvm {
+void initializeHexagonCopyHoistingPass(PassRegistry &Registry);
+FunctionPass *createHexagonCopyHoisting();
+} // namespace llvm
+
+namespace {
+
+class HexagonCopyHoisting : public MachineFunctionPass {
+
+public:
+  static char ID;
+  HexagonCopyHoisting() : MachineFunctionPass(ID), MFN(0), MRI(0) {
+    initializeHexagonCopyHoistingPass(*PassRegistry::getPassRegistry());
+  }
+
+  StringRef getPassName() const override { return "Hexagon Copy Hoisting"; }
+
+  void getAnalysisUsage(AnalysisUsage &AU) const override {
+    AU.addRequired<SlotIndexes>();
+    AU.addRequired<LiveIntervals>();
+    AU.addPreserved<SlotIndexes>();
+    AU.addPreserved<LiveIntervals>();
+    AU.addRequired<MachineDominatorTree>();
+    AU.addPreserved<MachineDominatorTree>();
+    MachineFunctionPass::getAnalysisUsage(AU);
+  }
+
+  bool runOnMachineFunction(MachineFunction &Fn) override;
+  void collectCopyInst();
+  void addMItoCopyList(MachineInstr *MI);
+  bool analyzeCopy(MachineBasicBlock *BB);
+  bool isSafetoMove(MachineInstr *CandMI);
+  void moveCopyInstr(MachineBasicBlock *DestBB, StringRef key,
+                     MachineInstr *MI);
+
+  MachineFunction *MFN;
+  MachineRegisterInfo *MRI;
+  StringMap<MachineInstr *> CopyMI;
+  std::vector<StringMap<MachineInstr *>> CopyMIList;
+};
+
+} // namespace
+
+char HexagonCopyHoisting::ID = 0;
+
+namespace llvm {
+char &HexagonCopyHoistingID = HexagonCopyHoisting::ID;
+}
+
+bool HexagonCopyHoisting::runOnMachineFunction(MachineFunction &Fn) {
+
+  if ((CPHoistFn != "") && (CPHoistFn != Fn.getFunction().getName()))
+    return false;
+
+  MFN = &Fn;
+  MRI = &Fn.getRegInfo();
+
+  LLVM_DEBUG(dbgs() << "\nCopy Hoisting:" << "\'" << Fn.getName() << "\'\n");
+
+  CopyMIList.clear();
+  CopyMIList.resize(Fn.getNumBlockIDs());
+
+  // Traverse through all basic blocks and collect copy instructions.
+  collectCopyInst();
+
+  // Traverse through the basic blocks again and move the COPY instructions
+  // that are present in all the successors of BB to BB.
+  bool changed = false;
+  for (auto I = po_begin(&Fn), E = po_end(&Fn); I != E; ++I) {
----------------
kparzysz wrote:

Prefer to use range-for loops over iterator based loops.  Most things in LLVM that have begin/end iterators also have an iterator range that you can use in a range-for loop.

Here specifically that would be `for (MachineBasicBlock *BB : post_order(&Fn))`, then you'd need to use `BB->` instead of `BB.` in the body.

https://github.com/llvm/llvm-project/pull/89313