[llvm] r202106 - [SROA] Add a debugging tool which shuffles the slices sequence prior to

[Chandler Carruth]

On Mon, Mar 3, 2014 at 6:11 PM, Adrian Prantl <aprantl at apple.com> wrote:

> I see. Shouldn’t it be a call to std::stable_sort(), then?


Well, the whole point is that it *isn't* a call to stable_sort because the
order of equal ranges shouldn't matter.

In practice, we have messed up and made the order matter in several
significant cases.

Right now, the order only matters in that it impacts the name
de-duplication and the order of use-def chains created by SROA (much like
serializing and deserializing through bitcode does), but I used this to
debug a bunch of other more serious issues.

Even in a no-asserts build, the resulting binary isn't perfectly stable
because we have some passes that are sensitive to incoming use-def ordering
sadly. =/
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