Re: [PATCH 0/2] RISC-V: New pass to optimize calculation of offsets for memory operations.

[Manolis Tsamis <manolis.tsamis@vrull.eu>]

On Thu, May 25, 2023 at 4:42 PM Jeff Law <jeffreyalaw@gmail.com> wrote:
>
>
>
> On 5/25/23 06:35, Manolis Tsamis wrote:
> >
> > This pass tries to optimize memory offset calculations by moving them
> > from add immediate instructions to the memory loads/stores.
> > For example it can transform this:
> >
> >    addi t4,sp,16
> >    add  t2,a6,t4
> >    shl  t3,t2,1
> >    ld   a2,0(t3)
> >    addi a2,1
> >    sd   a2,8(t2)
> >
> > into the following (one instruction less):
> >
> >    add  t2,a6,sp
> >    shl  t3,t2,1
> >    ld   a2,32(t3)
> >    addi a2,1
> >    sd   a2,24(t2)
> >
> > Although there are places where this is done already, this pass is more
> > powerful and can handle the more difficult cases that are currently not
> > optimized. Also, it runs late enough and can optimize away unnecessary
> > stack pointer calculations.
> >
> > The first patch in the series contains the implementation of this pass
> > while the second is a minor change that enables cprop_hardreg's
> > propgation of the stack pointer, because this pass depends on cprop
> > to do the propagation of optimized operations. If preferred I can split
> > this into two different patches (in which cases some of the testcases
> > included will fail temporarily).
> Thanks Manolis.  Do you happen to know if this includes the fixes I
> passed along to Philipp a few months back?  My recollection is one fixed
> stale DF data which prevented an ICE during bootstrapping, the other
> needed to ignore debug insns in one or two places so that the behavior
> didn't change based on the existence of debug insns.
>

Hi Jeff,

Yes this does include your fixes for DF and debug insns, along with
some other minor improvements.
Also, thanks for catching these!

Manolis

>
> Jeff