Messages in this thread | | | From | Christophe Leroy <> | Subject | Re: [RFC PATCH v3 11/12] powerpc: Remove unreachable() from WARN_ON() | Date | Mon, 27 Jun 2022 15:46:29 +0000 |
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Le 27/06/2022 à 17:35, Sathvika Vasireddy a écrit : > > 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() ? >
That seems odd.
Look at linux/compiler.h
It seems like unreachable() exists to help objtool.
Christophe
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