lkml.org 
[lkml]   [2022]   [Jun]   [27]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
SubjectRe: [RFC PATCH v3 11/12] powerpc: Remove unreachable() from WARN_ON()
From

On 25/06/22 12:16, Christophe Leroy wrote:
>
> Le 24/06/2022 à 20:32, Sathvika Vasireddy a écrit :
>> objtool is throwing *unannotated intra-function call*
>> warnings with a few instructions that are marked
>> unreachable. Remove unreachable() from WARN_ON()
>> to fix these warnings, as the codegen remains same
>> with and without unreachable() in WARN_ON().
> Did you try the two exemples described in commit 1e688dd2a3d6
> ("powerpc/bug: Provide better flexibility to WARN_ON/__WARN_FLAGS() with
> asm goto") ?
>
> Without your patch:
>
> 00000640 <test>:
> 640: 81 23 00 84 lwz r9,132(r3)
> 644: 71 29 40 00 andi. r9,r9,16384
> 648: 40 82 00 0c bne 654 <test+0x14>
> 64c: 80 63 00 0c lwz r3,12(r3)
> 650: 4e 80 00 20 blr
> 654: 0f e0 00 00 twui r0,0
>
> 00000658 <test9w>:
> 658: 2c 04 00 00 cmpwi r4,0
> 65c: 41 82 00 0c beq 668 <test9w+0x10>
> 660: 7c 63 23 96 divwu r3,r3,r4
> 664: 4e 80 00 20 blr
> 668: 0f e0 00 00 twui r0,0
> 66c: 38 60 00 00 li r3,0
> 670: 4e 80 00 20 blr
>
>
> With your patch:
>
> 00000640 <test>:
> 640: 81 23 00 84 lwz r9,132(r3)
> 644: 71 29 40 00 andi. r9,r9,16384
> 648: 40 82 00 0c bne 654 <test+0x14>
> 64c: 80 63 00 0c lwz r3,12(r3)
> 650: 4e 80 00 20 blr
> 654: 0f e0 00 00 twui r0,0
> 658: 4b ff ff f4 b 64c <test+0xc> <==
>
> 0000065c <test9w>:
> 65c: 2c 04 00 00 cmpwi r4,0
> 660: 41 82 00 0c beq 66c <test9w+0x10>
> 664: 7c 63 23 96 divwu r3,r3,r4
> 668: 4e 80 00 20 blr
> 66c: 0f e0 00 00 twui r0,0
> 670: 38 60 00 00 li r3,0 <==
> 674: 4e 80 00 20 blr <==
> 678: 38 60 00 00 li r3,0
> 67c: 4e 80 00 20 blr
>
The builtin variant of unreachable (__builtin_unreachable()) works.

How about using that instead of unreachable() ?


- Sathvika

\
 
 \ /
  Last update: 2022-06-27 17:37    [W:0.190 / U:1.584 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site