Re: [PATCH] Find more cases for AUTO_INC_DEC

[Adam Nemet <anemet at lnxw dot com>]

I write:
> Richard Henderson writes:
>> Have a look at Joern's large auto-increment patch.
> OK, I did.  It does not fix the basic testcase.  It seems to me that
> unless recognize_related_for_insn creates an entry in rel_base_list
> nothing gets optimized in optmize_relate_values_0.  In the testcase,
> insns that set up potentially related registers are hard regs and
> recognize_related_for_insn ignores those.  It is not clear if this is
> just a temporary limitation but this prevents any related-value
> optmization on the testcase.
> 
> But in my opinion even if this pass could deal with all auto-increment
> opportunities the real question is whether it will supersede the basic
> auto-increment optimization in flow.  I assume it would not.  All the
> required information to do the tranformation there is readily
> avaiable: reg_next_use is used to set up LOG_LINKs not just for
> AUTO_INC.  And if I am correct so far then my patch just takes another
> look at the same reg_next_use information in terms of the RHS of the
> addition: (r = p + 1; *(p + 1)), if P's next use is the address
> expression then we can substitute R there and then do the basic
> auto-increment optimization assuming R is not used or set in between.
> This results in 52% more auto-increment optimizations during a
> ppc-darwin bootstrap.
> 
> In the meantime, I also tested arm-elf on the simulator with no
> regression.  On ARM the basic testcase behaves similarly after the
> patch:
> 
> Before:
> 
>   stwu4:
>   	  str     r1, [r0, #4]
>   	  add     r0, r0, #4
>   	  bx      lr
> 
> 
> After:
> 
>   stwu4:
>   	  str     r1, [r0, #4]!
>   	  bx      lr

It's been two weeks since my response, so this is just a reminder
email.  The patch is here:
http://gcc.gnu.org/ml/gcc-patches/2005-07/msg01096.html.

Adam