Re: [PATCH] LoongArch: Correct the definition of is_branch_ins()

[Tiezhu Yang]

On 12/16/2022 11:18 AM, Jinyang He wrote:
> Hi, Tiezhu,
>
>
> On 2022-12-14 16:30, Tiezhu Yang wrote:
> > The current definition of is_branch_ins() is not correct,
>
> But the branch instruction opcode only use the high 6 bits,

Yes, I noticed that, the logic result of current code is right,
but it seems a little strange (only consider reg1i21_format)
at the first glance, the initial aim of this patch is to make
it theoretically correct, maybe it is not the best change.

I think we can neglect the instruction formats and check the
high 6 bits instead, what do you think of the following change?

diff --git a/arch/loongarch/include/asm/inst.h 
b/arch/loongarch/include/asm/inst.h
index c00e151..fd31752 100644
--- a/arch/loongarch/include/asm/inst.h
+++ b/arch/loongarch/include/asm/inst.h
@@ -329,8 +329,8 @@ static inline bool is_pc_ins(union 
loongarch_instruction *ip)

 static inline bool is_branch_ins(union loongarch_instruction *ip)
 {
-       return ip->reg1i21_format.opcode >= beqz_op &&
-               ip->reg1i21_format.opcode <= bgeu_op;
+       return ((ip->word >> 26) & 0x3f) >= beqz_op &&
+               ((ip->word >> 26) & 0x3f) <= bgeu_op;
 }

Thanks,
Tiezhu