Re: [committed][RISC-V] Remove errant hunk of code

[Vineet Gupta <vineetg@rivosinc.com>]

On 8/3/23 16:15, Jeff Law wrote:
>
>
> On 8/3/23 16:26, Vineet Gupta wrote:
>>
>> As discussed in Tue call, I definitely have 1 fix to riscv_rtx_costs 
>> (), which is worth pondering. It adjusts the cost of consts and helps 
>> Hoist GCSE constants (which granted kicks in only at -Os). However it 
>> does affect codegen in subtle ways since CSE1 now for some cases 
>> generates additional REG_EQUAL note.
> Yea, we'll definitely want to take a look.  It's not likely affecting 
> my work, but definitely want to evaluate as part of the overall 
> costing question.

OK, I'll spin it and post to the list after a testsuite run.

>
>
>>
>> On a different but slightly related note, I was playing with Zicond 
>> this morning (enabling by default in toolchain build and qemu) and I 
>> was surprised to see that glibc build currently doesn't have a single 
>> czero* insn - although gcc has bene configured with
> Probably costing ;-)   That little hunk that snuck through is part of 
> how I arrange to get more czero instructions when running the GCC 
> testsuite.
>
> Also note that if you're disassembling with binutils, I think it just 
> dumps it out as a .word or something similar.

Yeah something was off, I was building /using the latest binutils but 
then my fancy over-engineered objdump helper was pointing to an a 
non-zicond binutils :-)

>
>>
>> Point being, I can help with riscv_rtx_costs and friends, if you have 
>> something specific, but seems like you are in the thick of it and 
>> have that handled so I'll stay out of the way and refrain from zicond 
>> work/testing for the time being.
> ;-)  Actually if you wanted to poke at zicond, the most interesting 
> unexplored area I've come across is the COND_EXPR handling in gimple. 
> When we expand a COND_EXPR into RTL the first approach we take is to 
> try mov<mode>cc in RTL.
>
> Unfortunately we don't create COND_EXPRs all that often in gimple.  
> Some simple match.pd patterns would likely really help here.
>
> The problem is RTL expansion when mov<mode>cc FAILs is usually poor at 
> best.  So if we're going to add those match.pd patterns, we probably 
> need to beef up the RTL expansion code to do a better job when the 
> target doesn't have a mov<mode>cc RTL pattern.

Ok, I'll add that to my todo list.

Thx,
-Vineet