[llvm-dev] Errononous scheduling of COPY instruction.

[Tim Northover via llvm-dev]

Hi Dominique,

On Thu, 20 Sep 2018 at 16:27, Dominique Torette via llvm-dev
<llvm-dev at lists.llvm.org> wrote:
>         MOV_AB_ro @s1, %fab_roff0
>         %6:fpuaoffsetclass = COPY %fab_roff0; FPUaOffsetClass:%6

The MOV_AB_ro instruction there is only reading %fab_roff0 so there's
no reason for LLVM to think it can't be swapped with the following
copy. Should it maybe write that register instead?

If not, what's the architectural constraint that *does* prevent
movement? we might be able to help with how you need to describe that
to LLVM.

Cheers.

Tim.