tree fe7ffc27a5b7acce9a4694bf079965913a9461b8
parent 65a9a3d5b12449f4d32b4f6c01bcc421185a4bf6
author Asher Mancinelli <ashermancinelli@gmail.com> 1747231677 -0700
committer GitHub <noreply@github.com> 1747231677 -0700
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[flang] Add loop annotation attributes to the loop backedge (#126082)

Flang currently adds loop metadata to a conditional branch in the loop
preheader, while clang adds it to the loop latch's branch instruction.
Langref says:

> Currently, loop metadata is implemented as metadata attached to the
branch instruction in the loop latch block.
>
> https://llvm.org/docs/LangRef.html#llvm-loop

I misread langref a couple times, but I think this is the appropriate
branch op for the LoopAnnotationAttr. In a couple examples I found that
the metadata was lost entirely during canonicalization. This patch makes
the codegen look more like clang's and the annotations persist through
codegen.

* current clang: https://godbolt.org/z/8WhbcrnG3
* current flang: https://godbolt.org/z/TrPboqqcn