[clang] [clang][amdgpu] mapCABIAtomicOrdering - fix MSVC not all control paths return a value warning. NFC. (PR #180500)

[Simon Pilgrim via cfe-commits]

https://github.com/RKSimon created https://github.com/llvm/llvm-project/pull/180500

None

>From c5d0987f17312fc67775a6c05c39c654838c93a7 Mon Sep 17 00:00:00 2001
From: Simon Pilgrim <llvm-dev at redking.me.uk>
Date: Mon, 9 Feb 2026 10:28:47 +0000
Subject: [PATCH] [clang][amdgpu] mapCABIAtomicOrdering - fix MSVC not all
 control paths return a value warning. NFC.

---
 clang/lib/CodeGen/TargetBuiltins/AMDGPU.cpp | 1 +
 1 file changed, 1 insertion(+)

diff --git a/clang/lib/CodeGen/TargetBuiltins/AMDGPU.cpp b/clang/lib/CodeGen/TargetBuiltins/AMDGPU.cpp
index e923c285eff28..d3a2b08fb7a98 100644
--- a/clang/lib/CodeGen/TargetBuiltins/AMDGPU.cpp
+++ b/clang/lib/CodeGen/TargetBuiltins/AMDGPU.cpp
@@ -290,6 +290,7 @@ static llvm::AtomicOrdering mapCABIAtomicOrdering(unsigned AO) {
   case llvm::AtomicOrderingCABI::relaxed:
     return llvm::AtomicOrdering::Monotonic;
   }
+  llvm_unreachable("Unknown AtomicOrderingCABI enum");
 }
 
 // For processing memory ordering and memory scope arguments of various