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

[Jeff Law <jeffreyalaw@gmail.com>]

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.


Jeff