[cfe-dev] Why no NSW/NUW with SHL instruction?

[Reid Kleckner]

What is the difference between logical and arithmetic left shift on your
target? LLVM only makes that distinction for right shift, and not for left
shift.

On Wed, Nov 19, 2014 at 10:32 AM, Ryan Taylor <ryta1203 at gmail.com> wrote:

> I'm curious why there is not always a nsw/nuw flag with shl instruction?
> For example, I have a signed int I'm shifting left (want to generate an
> arithmetic left shift in backend for signed int shift lefts and logical for
> unsigned, at the moment).... but shl on a signed int does not always have
> nsw/nuw flag present, why is this?
>
> Thank you.
>
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