[PATCH] D18890: [AArch64] add SSA Load Store optimization pass

[James Molloy via llvm-commits]

jmolloy added a comment.

In http://reviews.llvm.org/D18890#418230, @JongwonLee wrote:

> In http://reviews.llvm.org/D18890#417820, @jmolloy wrote:
>
> > Hi,
> >
> > So why aren't you doing this in codegen prepare or dag combine?
> >
> > Cheers,
> >
> > James
>
>
> Hi,
>  I didn't try this work on other positions except backend.
>  As I mentioned before, this work is only considering AArch64 not other backends.
>  Is there any advantages of doing this work on codegen prepare or dag combine?


Hi Jongwon,

Sure, there are advantages. Modifying IR is substantially easier and less prone to error than modifying machine instructions. This is also a generic optimization fixing a problem that likely affects more than just the AArch64 target, therefore the right thing to do is to implement it in such a way that it will benefit other targets (unless that causes a very high cost).

In this case it would seem to me quicker, easier and less technical debt later to implement this higher up in the compiler.

James


http://reviews.llvm.org/D18890