[llvm] MachinePipeliner: Fix using getUniqueVRegDef on a physical register (PR #216793)

[Matt Arsenault via llvm-commits]

https://github.com/arsenm created https://github.com/llvm/llvm-project/pull/216793

Currently this is permissive and doesn't assert when called with
a physical register, but I'm working on changing this edge case.
No current observable change.

Co-authored-by: Claude (Claude-Opus-4.8) <noreply at anthropic.com>

>From 8e5e9e38d8ba1016cb091a208961e5b15be337c0 Mon Sep 17 00:00:00 2001
From: Matt Arsenault <Matthew.Arsenault at amd.com>
Date: Mon, 17 Aug 2026 19:46:44 +0200
Subject: [PATCH] MachinePipeliner: Fix using getUniqueVRegDef on a physical
 register

Currently this is permissive and doesn't assert when called with
a physical register, but I'm working on changing this edge case.
No current observable change.

Co-authored-by: Claude (Claude-Opus-4.8) <noreply at anthropic.com>
---
 llvm/lib/CodeGen/MachinePipeliner.cpp | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/llvm/lib/CodeGen/MachinePipeliner.cpp b/llvm/lib/CodeGen/MachinePipeliner.cpp
index cbe1c3a9d2cc2..cbac40f04fd19 100644
--- a/llvm/lib/CodeGen/MachinePipeliner.cpp
+++ b/llvm/lib/CodeGen/MachinePipeliner.cpp
@@ -1323,6 +1323,8 @@ void SwingSchedulerDAG::updatePhiDependences() {
         }
       } else if (MO.isUse()) {
         // If the register is defined by a Phi, then create a true dependence.
+        if (!Reg.isVirtual())
+          continue;
         MachineInstr *DefMI = MRI.getUniqueVRegDef(Reg);
         if (DefMI == nullptr)
           continue;