[llvm] AArch64: Guard optimizeCondBranch against a physical copy source (PR #216699)

[Matt Arsenault via llvm-commits]

https://github.com/arsenm created https://github.com/llvm/llvm-project/pull/216699

optimizeCondBranch walks COPY chains from the branch condition register,
calling getVRegDef on each copy's source operand. A COPY source can be a
physical register which doesn't make sense to pass to getVRegDef.

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

>From 55cd35876fa16ff399c95dba6344255e71799e82 Mon Sep 17 00:00:00 2001
From: Matt Arsenault <Matthew.Arsenault at amd.com>
Date: Mon, 17 Aug 2026 13:22:10 +0200
Subject: [PATCH] AArch64: Guard optimizeCondBranch against a physical copy
 source

optimizeCondBranch walks COPY chains from the branch condition register,
calling getVRegDef on each copy's source operand. A COPY source can be a
physical register which doesn't make sense to pass to getVRegDef.

Co-authored-by: Claude (Claude-Opus-4.8) <noreply at anthropic.com>
---
 llvm/lib/Target/AArch64/AArch64InstrInfo.cpp | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/llvm/lib/Target/AArch64/AArch64InstrInfo.cpp b/llvm/lib/Target/AArch64/AArch64InstrInfo.cpp
index bd4cacc737fd7..ced050e3bbd8a 100644
--- a/llvm/lib/Target/AArch64/AArch64InstrInfo.cpp
+++ b/llvm/lib/Target/AArch64/AArch64InstrInfo.cpp
@@ -10096,6 +10096,8 @@ bool AArch64InstrInfo::optimizeCondBranch(MachineInstr &MI) const {
   // Look through COPY instructions to find definition.
   while (DefMI->isCopy()) {
     Register CopyVReg = DefMI->getOperand(1).getReg();
+    if (!CopyVReg.isVirtual())
+      return false;
     if (!MRI->hasOneNonDBGUse(CopyVReg))
       return false;
     if (!MRI->hasOneDef(CopyVReg))