Re: RISC-V: Folding memory for FP + constant case

[Jeff Law <jeffreyalaw@gmail.com>]

On 8/1/23 17:06, Philipp Tomsich wrote:
> Very helpful! Looks as if regprop for stack_pointer is now either too
> conservative — or one of our patches is missing in everyone's test
> setup; we'll take a closer look.
They must not be working as expected or folks are using old trees. 
Manolis's work for regcprop has been on the trunk for about 5-6 weeks ag 
this point:


> commit 893883f2f8f56984209c6ed210ee992ff71a14b0
> Author: Manolis Tsamis <manolis.tsamis@vrull.eu>
> Date:   Tue Jun 20 16:23:52 2023 +0200
> 
>     cprop_hardreg: fix ORIGINAL_REGNO/REG_ATTRS/REG_POINTER handling
>     
>     Fixes: 6a2e8dcbbd4bab3
>     
>     Propagation for the stack pointer in regcprop was enabled in
>     6a2e8dcbbd4bab3, but set ORIGINAL_REGNO/REG_ATTRS/REG_POINTER for
>     stack_pointer_rtx which caused regression (e.g., PR 110313, PR 110308).
>     
>     This fix adds special handling for stack_pointer_rtx in the places
>     where maybe_mode_change is called. This also adds an check in
>     maybe_mode_change to return the stack pointer only when the requested
>     mode matches the mode of stack_pointer_rtx.
>     
>             PR debug/110308
>     
>     gcc/ChangeLog:
>     
>             * regcprop.cc (maybe_mode_change): Check stack_pointer_rtx mode.
>             (maybe_copy_reg_attrs): New function.
>             (find_oldest_value_reg): Use maybe_copy_reg_attrs.
>             (copyprop_hardreg_forward_1): Ditto.
>     
>     gcc/testsuite/ChangeLog:
>     
>             * g++.dg/torture/pr110308.C: New test.
>     
>     Signed-off-by: Manolis Tsamis <manolis.tsamis@vrull.eu>
>     Signed-off-by: Philipp Tomsich <philipp.tomsich@vrull.eu>
> 
> commit 6a2e8dcbbd4bab374b27abea375bf7a921047800
> Author: Manolis Tsamis <manolis.tsamis@vrull.eu>
> Date:   Thu May 25 13:44:41 2023 +0200
> 
>     cprop_hardreg: Enable propagation of the stack pointer if possible
>     
>     Propagation of the stack pointer in cprop_hardreg is currenty
>     forbidden in all cases, due to maybe_mode_change returning NULL.
>     Relax this restriction and allow propagation when no mode change is
>     requested.
>     
>     gcc/ChangeLog:
>     
>             * regcprop.cc (maybe_mode_change): Enable stack pointer
>             propagation.