[llvm] [SelectionDAG] Preserve volatile undef stores. (PR #99918)

[Matt Arsenault via llvm-commits]

================
@@ -36,7 +34,6 @@ define amdgpu_kernel void @test_memchr(ptr addrspace(1) %src, i32 %char, i64 %le
 ; GCN: s_addc_u32 s{{[0-9]+}}, s{{[0-9]+}}, strcpy at rel32@hi+12
 define amdgpu_kernel void @test_strcpy(ptr %dst, ptr %src) #0 {
   %res = call ptr @strcpy(ptr %dst, ptr %src)
-  store volatile ptr %res, ptr addrspace(1) undef
----------------
arsenm wrote:

Same keep all these dummy uses, avoid the undefs 

https://github.com/llvm/llvm-project/pull/99918