[PATCH v2 4/5] LoongArch: Add support for LA32 in sysdeps/unix/sysv/linux/loongarch

[WANG Xuerui]

On 12/18/25 21:05, Adhemerval Zanella Netto wrote:
> 
> 
> On 18/12/25 09:30, mengqinggang wrote:
>> [snip]
>>   
>> @@ -54,7 +54,7 @@ ENTRY (__clone)
>>   	syscall		0
>>   
>>   	blt		a0, zero ,L (error)
>> -	beqz		a0,L (thread_start)
>> +	beq		a0, zero, L (thread_start)
>>   
>>   	/* Successful return from the parent.  */
>>   	ret
> 
> Does it meant that loongarch32 does not support all the branch
> instruction from loongarch64? Or that binutils is not recognizing
> beqz as a alias for beq reg, zero ?

It is a bit interesting: b{eq,ne}z are *different* instructions in LA64 
and LA32S so that an additional 5 bits becomes free for encoding the 
offset. The reduced subset, LA32R, doesn't have them for simplicity reasons.

We may be able to make "b{eq,ne}z x, y" aliases for "b{eq,ne} x, zero, 
y" respectively for LA32R, and this won't affect compatibility because 
one has to use up-to-date binutils anyway to get any LA32 support at all.

I don't know if doing this would create confusion for someone 
deliberately choosing beqz for a big offset that isn't expressible with 
beq, but I guess the case is contrived because beq already can reach 
+/-128KiB which is more than enough for conditional branches. Maybe 
someone from Loongson would prepare a patch for binutils, or I can do it 
later (next week or so).

-- 
Regards,
WANG "xen0n" Xuerui

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