The attributor can infer the alignment of %p at the call-site in this
example [1]:
```
define void @f(ptr align 8 %p, i1 %c1, i1 %c2) {
entry:
br i1 %c1, label %bb.1, label %exit
bb.1:
call void (...) @llvm.fake.use(ptr %p)
br label %exit
exit:
ret void
}
```
but not when there's an additional conditional branch:
```
define void @f(ptr align 8 %p, i1 %c1, i1 %c2) {
entry:
br i1 %c1, label %bb.1, label %exit
bb.1:
br i1 %c2, label %bb.2, label %exit
bb.2:
call void (...) @llvm.fake.use(ptr %p)
br label %exit
exit:
ret void
}
```
unless `-attributor-annotate-decl-cs` is enabled. This patch extends
`followUsesInMBEC` to handle such recursive branches.
n.b. admittedly I wrote this patch before discovering inferring the
alignment in this example is already possible with
`-attributor-annotate-decl-cs`, I came to realise this once writing the
tests, but this seems like a gap regardless looking at existing FIXMEs,
plus the alignment can now be inferred in this particular example
without the flag.
[1] https://godbolt.org/z/aKoc75so5
65fd9f1f89