[llvm] [CodeGen] Introduce MI flag for Live Range split instructions (PR #117543)

[Christudasan Devadasan via llvm-commits]

https://github.com/cdevadas created https://github.com/llvm/llvm-project/pull/117543

For some targets, it is required to identify the COPY instruction
corresponds to the RA inserted live range split. Adding the new
flag `MachineInstr::LRSplit` to serve the purpose.

>From 90f830fe1e7aabf73ba3b4dd43cf4360dbd28571 Mon Sep 17 00:00:00 2001
From: Christudasan Devadasan <Christudasan.Devadasan at amd.com>
Date: Thu, 14 Nov 2024 14:11:44 +0530
Subject: [PATCH] [CodeGen] Introduce MI flag for Live Range split instructions

For some targets, it is required to identify the COPY instruction
corresponds to the RA inserted live range split. Adding the new
flag `MachineInstr::LRSplit` to serve the purpose.
---
 llvm/include/llvm/CodeGen/MachineInstr.h | 3 ++-
 llvm/lib/CodeGen/SplitKit.cpp            | 2 ++
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/llvm/include/llvm/CodeGen/MachineInstr.h b/llvm/include/llvm/CodeGen/MachineInstr.h
index ead6bbe1d5f641..4545b205d07466 100644
--- a/llvm/include/llvm/CodeGen/MachineInstr.h
+++ b/llvm/include/llvm/CodeGen/MachineInstr.h
@@ -119,7 +119,8 @@ class MachineInstr
     Disjoint = 1 << 19,      // Each bit is zero in at least one of the inputs.
     NoUSWrap = 1 << 20,      // Instruction supports geps
                              // no unsigned signed wrap.
-    SameSign = 1 << 21       // Both operands have the same sign.
+    SameSign = 1 << 21,      // Both operands have the same sign.
+    LRSplit = 1 << 22        // Instruction for live range split.
   };
 
 private:
diff --git a/llvm/lib/CodeGen/SplitKit.cpp b/llvm/lib/CodeGen/SplitKit.cpp
index eb33b93c197d7c..5042f074c26c45 100644
--- a/llvm/lib/CodeGen/SplitKit.cpp
+++ b/llvm/lib/CodeGen/SplitKit.cpp
@@ -533,6 +533,7 @@ SlotIndex SplitEditor::buildSingleSubRegCopy(
               | getInternalReadRegState(!FirstCopy), SubIdx)
       .addReg(FromReg, 0, SubIdx);
 
+  CopyMI->setFlag(MachineInstr::LRSplit);
   SlotIndexes &Indexes = *LIS.getSlotIndexes();
   if (FirstCopy) {
     Def = Indexes.insertMachineInstrInMaps(*CopyMI, Late).getRegSlot();
@@ -552,6 +553,7 @@ SlotIndex SplitEditor::buildCopy(Register FromReg, Register ToReg,
     // The full vreg is copied.
     MachineInstr *CopyMI =
         BuildMI(MBB, InsertBefore, DebugLoc(), Desc, ToReg).addReg(FromReg);
+    CopyMI->setFlag(MachineInstr::LRSplit);
     return Indexes.insertMachineInstrInMaps(*CopyMI, Late).getRegSlot();
   }