[IR] Make detailed structural hash test look at diffs

[aidengrossman]

Summary

This patch makes structural-hash-detailed.ll look at diffs rather than
specific values to make the test more robust against the underlying
hashing implementation while still testing that the hash value is
deterministic across multiple runs.

[aeubanks]

llvm/test/Analysis/StructuralHash/structural-hash-detailed.ll

5–11

can FileCheck --input-file=%t.1 %s below to run opt one less time

llvm/test/Analysis/StructuralHash/structural-hash-detailed.ll

-; Require 64 bits here as the hash will change depending upon whether we are on a 32-bit
-; or 64-bit platform.
-; REQUIRE: llvm-64-bits
+; Ensure that the value of the structural hash is consistent across runs to
+; check that we aren't doing something like hashing a pointer that could
+; introduce non-determinism.
 
-; RUN: opt -passes='print<structural-hash><detailed>' -disable-output %s 2>&1 | FileCheck %s
+; RUN: opt -passes='print<structural-hash><detailed>' -disable-output %s &> %t.1
+; RUN: opt -passes='print<structural-hash><detailed>' -disable-output %s &> %t.2
+; RUN: diff %t.1 %t.2
+
+; Check that we get valid output in the detailed case.
+
+; cat %t.1 | FileCheck %s
 
 define i64 @f1(i64 %a) {
   ret i64 %a
 }
 
-; These values here are explicitly defined to ensure that they are deterministic
-; on all 64-bit platforms and across runs.
-
-; CHECK: Module Hash: 81f1328ced269bd
-; CHECK: Function f1 Hash: 81f1328ced269bd
+; CHECK: Module Hash: {{([a-z0-9]{14,})}}
+; CHECK: Function f1 Hash: {{([a-z0-9]{14,})}}