[llvm-dev] RFC: Killing undef and spreading poison

[Chandler Carruth via llvm-dev]

I'm still digesting the proposal in its entirety, but one point I want to
call out here:

On Tue, Oct 18, 2016 at 1:39 PM Friedman, Eli via llvm-dev <
llvm-dev at lists.llvm.org> wrote:

> Instcombine currently transforms "memcpy(dst, src, 4)" to "load i32 src;
> store i32 dst".  I guess that's illegal under this model?  How about the
> related transform "memcpy(dst, src, 4)" to "load <4 x i8> src; store <4
> x i8> dst"?  (SROA also performs similar transforms.)
>

I think it is really important that memcpy and load/store pair be
equivalent. If this is in fact true about the proposal, I would want to
really dig into why and whether anything could be done to make them
equivalent.
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