[all-commits] [llvm/llvm-project] 65fd9f: [Attributor] Support nested conditional branches (...

[Cullen Rhodes via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 65fd9f1f891bcc4bc1a27a00a45a4c1d9670ae63
      https://github.com/llvm/llvm-project/commit/65fd9f1f891bcc4bc1a27a00a45a4c1d9670ae63
  Author: Cullen Rhodes <cullen.rhodes at arm.com>
  Date:   2025-11-24 (Mon, 24 Nov 2025)

  Changed paths:
    M llvm/lib/Transforms/IPO/AttributorAttributes.cpp
    M llvm/test/Transforms/Attributor/dereferenceable-1.ll
    M llvm/test/Transforms/Attributor/nonnull.ll
    M llvm/test/Transforms/Attributor/value-simplify-pointer-info.ll
    M llvm/test/Transforms/Attributor/willreturn.ll
    M llvm/test/Transforms/FunctionAttrs/nonnull.ll

  Log Message:
  -----------
  [Attributor] Support nested conditional branches (#168532)

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



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