[llvm] [LiveIntervals] Ignore artificial regs when adding kill flags (PR #116963)

[Matt Arsenault via llvm-commits]

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@@ -730,7 +730,16 @@ void LiveIntervals::addKillFlags(const VirtRegMap *VRM) {
     // Find the regunit intervals for the assigned register. They may overlap
     // the virtual register live range, cancelling any kills.
     RU.clear();
-    for (MCRegUnit Unit : TRI->regunits(PhysReg)) {
+    LaneBitmask ArtificialLanes = LaneBitmask::getNone();
+    for (MCRegUnitMaskIterator UI(PhysReg, TRI); UI.isValid(); ++UI) {
+      auto [Unit, Bitmask] = *UI;
+      // Record lane mask for all artificial RegUnits for this physreg.
+      for (MCRegUnitRootIterator Root(Unit, TRI); Root.isValid(); ++Root) {
+        if (TRI->isArtificial(*Root)) {
+          ArtificialLanes |= Bitmask;
+          break;
+        }
+      }
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arsenm wrote:

Move this to a helper function that returns the mask instead of breaking out of the loop

https://github.com/llvm/llvm-project/pull/116963