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SubjectRe: [RFC PATCH v3 11/12] powerpc: Remove unreachable() from WARN_ON()
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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


Christophe

>
> Signed-off-by: Sathvika Vasireddy <sv@linux.ibm.com>
> ---
> arch/powerpc/include/asm/bug.h | 1 -
> 1 file changed, 1 deletion(-)
>
> diff --git a/arch/powerpc/include/asm/bug.h b/arch/powerpc/include/asm/bug.h
> index ecbae1832de3..df6c11e008b9 100644
> --- a/arch/powerpc/include/asm/bug.h
> +++ b/arch/powerpc/include/asm/bug.h
> @@ -97,7 +97,6 @@
> __label__ __label_warn_on; \
> \
> WARN_ENTRY("twi 31, 0, 0", BUGFLAG_WARNING | (flags), __label_warn_on); \
> - unreachable(); \
> \
> __label_warn_on: \
> break; \
\
 
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