[llvm] [WIP][CodeGen] Modifying MBB's liveins representation as into regUnits (PR #129847)

[Vikash Gupta via llvm-commits]

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@@ -88,7 +88,7 @@ void LiveRegUnits::accumulate(const MachineInstr &MI) {
 static void addBlockLiveIns(LiveRegUnits &LiveUnits,
                             const MachineBasicBlock &MBB) {
   for (const auto &LI : MBB.liveins())
-    LiveUnits.addRegMasked(LI.PhysReg, LI.LaneMask);
+    LiveUnits.addRegMasked(LI, LaneBitmask::getAll());
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vg0204 wrote:

> Further simplification is possible here, since this is the only call to addRegMasked so it no longer needs a Mask argument.


Yes, agreed, for that, addRegmasked requires a default lanemask arg which is not the current case! 

https://github.com/llvm/llvm-project/pull/129847