AMDGPU: Switch test to generated checks (#131315)

I doubt this is testing what it originally intended anymore. Also
replace an undef.

Author: arsenm

llvm/test/CodeGen/AMDGPU/subreg-eliminate-dead.ll

@@ -1,16 +1,19 @@
-; RUN: llc -mtriple=amdgcn-- -verify-machineinstrs -o - %s | FileCheck %s
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py UTC_ARGS: --version 5
+; RUN: llc -mtriple=amdgcn-- -mcpu=tahiti < %s | FileCheck %s
 ; LiveRangeEdit::eliminateDeadDef did not update LiveInterval sub ranges
 ; properly.
 
 ; Just make sure this test doesn't crash.
-; CHECK-LABEL: foobar:
-; CHECK: s_endpgm
 define amdgpu_kernel void @foobar() {
+; CHECK-LABEL: foobar:
+; CHECK:       ; %bb.0:
+; CHECK-NEXT:    s_endpgm
   %v0 = icmp eq <4 x i32> poison, <i32 0, i32 1, i32 2, i32 3>
   %v3 = sext <4 x i1> %v0 to <4 x i32>
   %v4 = extractelement <4 x i32> %v3, i32 1
   %v5 = icmp ne i32 %v4, 0
-  %v6 = select i1 %v5, i32 undef, i32 0
+  %undef = freeze i32 poison
+  %v6 = select i1 %v5, i32 %undef, i32 0
   %v15 = insertelement <2 x i32> poison, i32 %v6, i32 1
   store <2 x i32> %v15, ptr addrspace(1) poison, align 8
   ret void