[PATCH] D136284: SROA should freeze undefs for loads with no prior stores

Fri Oct 21 06:22:45 PDT 2022

jamieschmeiser added a comment.

In D136284#3869306 <https://reviews.llvm.org/D136284#3869306>, @nlopes wrote:

>> However, multiple loads of the same memory must be equal
>
> This premise is incorrect w.r.t. with current semantics, which say that loads return undef for uninit memory.
>
> As Nikita mentioned we are working towards changing this semantics. The work is ongoing, but we pivoted to make a couple of improvements in other areas to avoid perf regressions. For example, see the clang !noundef patches.

This is a C/C++ language semantics statement.  Yes, I realize that LLVM is not language specific, but this is what is generated for this, and also, what freeze appears specifically designed to handle.

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  https://reviews.llvm.org/D136284/new/

https://reviews.llvm.org/D136284