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

[Christudasan Devadasan via llvm-commits]

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

>From c32897019c4cac0b2d491acbf042c9d37a377857 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 8e2574974a82d..b52205322819a 100644
--- a/llvm/include/llvm/CodeGen/MachineInstr.h
+++ b/llvm/include/llvm/CodeGen/MachineInstr.h
@@ -123,8 +123,9 @@ class MachineInstr
     NoUSWrap = 1 << 20,      // Instruction supports geps
                              // no unsigned signed wrap.
     SameSign = 1 << 21,      // Both operands have the same sign.
-    InBounds = 1 << 22       // Pointer arithmetic remains inbounds.
+    InBounds = 1 << 22,      // Pointer arithmetic remains inbounds.
                              // Implies NoUSWrap.
+    LRSplit = 1 << 23        // Instruction for live range split.
   };
 
 private:
diff --git a/llvm/lib/CodeGen/SplitKit.cpp b/llvm/lib/CodeGen/SplitKit.cpp
index 8ec4bfbb5a330..e7fdceb7f4923 100644
--- a/llvm/lib/CodeGen/SplitKit.cpp
+++ b/llvm/lib/CodeGen/SplitKit.cpp
@@ -531,6 +531,7 @@ 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();
@@ -550,6 +551,7 @@ 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();
   }