[AtomicExpand] Drop explicit datalayout from test

Also remove the R600 checks this test as well as a duplicate RUN line.

Reviewed By: arsenm

Pull Request: #137923

Author: arichardson

llvm/test/Transforms/AtomicExpand/AMDGPU/expand-atomic-i16.ll

@@ -1,9 +1,5 @@
 ; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
-; RUN: opt -mtriple=amdgcn-amd-amdhsa -S -passes=atomic-expand %s | FileCheck -check-prefixes=CHECK,GCN,BASE %s
-; RUN: opt -mtriple=amdgcn-amd-amdhsa -S -passes=atomic-expand %s | FileCheck -check-prefixes=CHECK,GCN,GFX942 %s
-; RUN: opt -mtriple=r600-mesa-mesa3d -S -passes=atomic-expand %s | FileCheck  -check-prefixes=CHECK,R600 %s
-
-target datalayout = "e-p:64:64-p1:64:64-p2:32:32-p3:32:32-p4:64:64-p5:32:32-p6:32:32-p7:160:256:256:32-p8:128:128-i64:64-v16:16-v24:32-v32:32-v48:64-v96:128-v192:256-v256:256-v512:512-v1024:1024-v2048:2048-n32:64-S32-A5"
+; RUN: opt -mtriple=amdgcn-amd-amdhsa -S -passes=atomic-expand %s | FileCheck --check-prefixes=CHECK,GCN %s
 
 define i16 @test_atomicrmw_xchg_i16_global_agent(ptr addrspace(1) %ptr, i16 %value) {
 ; CHECK-LABEL: @test_atomicrmw_xchg_i16_global_agent(
@@ -1377,7 +1373,4 @@ define i16 @test_atomicrmw_add_i16_buffer_fat_agent_align4(ptr addrspace(7) %ptr
 !8 = !{!"Simple C/C++ TBAA"}
 
 ;; NOTE: These prefixes are unused and the list is autogenerated. Do not add tests below this line:
-; BASE: {{.*}}
 ; GCN: {{.*}}
-; GFX942: {{.*}}
-; R600: {{.*}}