[clang] [llvm] [IR] Add `fpmath` to keep list of dropUBImplyingAttrsAndMetadata (PR #179019)

[Yingwei Zheng via cfe-commits]

================
@@ -69,3 +69,12 @@ EntryBlock:
 ; CHECK: select i1 %A, float 0x3FD5555560000000, float [[OP]]
 }
 
+define float @test8(i1 %A, float %B) {
+EntryBlock:
+  %cf = select i1 %A, float 1.000000e+00, float %B
+  %op= fdiv float 3.000000e+00, %cf, !fpmath !{float 2.5}
----------------
dtcxzyw wrote:

```suggestion
  %op = fdiv float 3.000000e+00, %cf, !fpmath !{float 2.5}
```

https://github.com/llvm/llvm-project/pull/179019