[PATCH] D104636: [LoopIdiom] [LoopNest] let the pass deal with runtime memset size

[Roman Lebedev via Phabricator via llvm-commits]

lebedev.ri added a comment.

In D104636#2886251 <https://reviews.llvm.org/D104636#2886251>, @efriedma wrote:

> I'm not sure we actually need to version the loop to handle overflow.

That was my comment, too, and i've yet to see a concise explanation why that isn't the case.

> In any given address-space, there are at most 2^N bytes addressable by "gep ptr, i" where N is DataLayout::getIndexTypeSizeInBits().  Assuming the memset isn't volatile, there isn't any point to storing to an address more than once. So we only actually need to memset `min(2^N, TotalBytes)` bytes.  You should be able to pass that number to memset.


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https://reviews.llvm.org/D104636