add CHECK

Author: aeubanks

llvm/test/Transforms/PGOProfile/unreachable-block.ll

@@ -1,8 +1,9 @@
 ; RUN: llvm-profdata merge %S/Inputs/unreachable-block.proftext -o %t.profdata
-; RUN: opt < %s -passes=pgo-instr-use -pgo-test-profile-file=%t.profdata -S
+; RUN: opt < %s -passes=pgo-instr-use -pgo-test-profile-file=%t.profdata -S | FileCheck %s
 
 declare ptr @bar()
 
+; CHECK: define ptr @foo
 define ptr @foo() {
 entry:
   ret ptr null