[llvm] [ModuloSchedule] Implement modulo variable expansion for pipelining (PR #65609)

[James Nagurne via llvm-commits]

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@@ -2096,6 +2096,631 @@ void PeelingModuloScheduleExpander::validateAgainstModuloScheduleExpander() {
   MSE.cleanup();
 }
 
+MachineInstr *ModuloScheduleExpanderMVE::cloneInstr(MachineInstr *OldMI) {
+  MachineInstr *NewMI = MF.CloneMachineInstr(OldMI);
+
+  // TODO: Offset information needs to be corrected.
+  NewMI->dropMemRefs(MF);
+
+  return NewMI;
+}
+
+/// Create a dedicated exit for Loop. Exit is the original exit for Loop.
+/// If it is already dedicated exit, return it. Otherwise, insert a new
+/// block between them and return the new block.
+static MachineBasicBlock *createDedicatedExit(MachineBasicBlock *Loop,
+                                              MachineBasicBlock *Exit) {
+  if (Exit->pred_size() == 1)
+    return Exit;
+
+  MachineFunction *MF = Loop->getParent();
+  const TargetInstrInfo *TII = MF->getSubtarget().getInstrInfo();
+
+  MachineBasicBlock *NewExit =
+      MF->CreateMachineBasicBlock(Loop->getBasicBlock());
+  MF->insert(Loop->getIterator(), NewExit);
+
+  MachineBasicBlock *TBB = nullptr, *FBB = nullptr;
+  SmallVector<MachineOperand, 4> Cond;
+  TII->analyzeBranch(*Loop, TBB, FBB, Cond);
+  if (TBB == Loop)
+    FBB = NewExit;
+  else if (FBB == Loop)
+    TBB = NewExit;
+  else
+    llvm_unreachable("unexpected loop structure");
+  TII->removeBranch(*Loop);
+  TII->insertBranch(*Loop, TBB, FBB, Cond, DebugLoc());
+  Loop->removeSuccessor(Exit);
+  Loop->addSuccessor(NewExit);
+  TII->insertUnconditionalBranch(*NewExit, Exit, DebugLoc());
+  NewExit->addSuccessor(Exit);
+
+  for (MachineInstr &Phi : Exit->phis()) {
+    for (MachineOperand &MO : Phi.operands())
+      if (MO.isMBB() && MO.getMBB() == Loop)
+        MO.setMBB(NewExit);
+  }
+
+  return NewExit;
+}
+
+/// Generate a pipelined loop that is unrolled by using MVE algorithm and any
+/// other necessary blocks. The control flow is modified to execute the
+/// pipelined loop if the trip count satisfies the condition, otherwise the
+/// original loop. The original loop is also used to execute the reminder
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DragonDisciple wrote:

'reminder' -> 'remainder'

https://github.com/llvm/llvm-project/pull/65609