Date: Fri, 16 Dec 2016 00:01:28 -0800 From: Mark Millard <markmi@dsl-only.net> To: Justin Hibbits <jhibbits@FreeBSD.org> Cc: Nathan Whitehorn <nwhitehorn@freebsd.org>, FreeBSD PowerPC ML <freebsd-ppc@freebsd.org> Subject: Re: sys/powerpc/powerpc/trap.c has messed up masking operation?: use of || for bit field masling Message-ID: <6335DBE9-4942-45B2-8DD7-0EDF781CA0F4@dsl-only.net> In-Reply-To: <96CACD85-DED4-46C6-BBE3-53B4DEFF89DD@FreeBSD.org> References: <0661C9A5-5D4C-4F00-9B0C-F80688BED8A4@dsl-only.net> <96CACD85-DED4-46C6-BBE3-53B4DEFF89DD@FreeBSD.org>
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On 2016-Dec-15, at 8:42 PM, Justin Hibbits <jhibbits at FreeBSD.org> = wrote: > Hi Mark, >=20 > On Dec 13, 2016, at 10:41 PM, Mark Millard wrote: >=20 >> clang 3.9.0 is complaining about: >>=20 >> --- trap.o --- >> /usr/src/sys/powerpc/powerpc/trap.c:283:42: warning: use of logical = '||' with constant operand [-Wconstant-logical-operand] >> frame->cpu.booke.dbcr0 &=3D ~(DBCR0_IDM || = DBCR0_IC); >> ^ = ~~~~~~~~ >> /usr/src/sys/powerpc/powerpc/trap.c:283:42: note: use '|' for a = bitwise operation >> frame->cpu.booke.dbcr0 &=3D ~(DBCR0_IDM || = DBCR0_IC); >> ^~ >> | >> Looking around: >>=20 >>=20 >> # grep DBCR0_ /usr/src/sys/powerpc/include/spr.h >> . . . >> #define DBCR0_IDM 0x40000000 /* Internal Debug Mode = */ >> . . . >> #define DBCR0_IC 0x08000000 /* Instruction = Completion debug event */ >> . . . >>=20 >> || use seems unlikely to be correct for the context. >>=20 >=20 > Good find. Fixed in r310146, to be merged to stable/11 in a couple = weeks. Thanks. >>=20 >> There is also this that I happened to notice = sys/powerpc/powerpc/intr_machdep.c : >>=20 >> --- intr_machdep.o --- >> /usr/src/sys/powerpc/powerpc/intr_machdep.c:454:15: warning: = comparison of constant -1 with expression of type 'enum intr_trigger' is = always false [-Wtautological-constant-out-of-range-compare] >> if (i->trig =3D=3D -1) >> ~~~~~~~ ^ ~~ >> /usr/src/sys/powerpc/powerpc/intr_machdep.c:500:16: warning: = comparison of constant -1 with expression of type 'enum intr_trigger' is = always false [-Wtautological-constant-out-of-range-compare] >> if (i->trig =3D=3D -1) >> ~~~~~~~ ^ ~~ >=20 > This may or may not be a problem, depending on optimization settings. = Can you file a bug for this so it doesn't get lost? Bugzilla 215333 has the submittal. >>=20 >> There are other comparisons around with a constant >> result at compile time. But they tend to be in less >> central areas like zfs. Similarly for some other >> types of compiler reports. >>=20 >> =3D=3D=3D >> Mark Millard >> markmi at dsl-only.net >>=20 >=20 >=20 > Thanks for the clang and external toolchain testing. Lots of good = finds. Glad to help. > - Justin =3D=3D=3D Mark Millard markmi at dsl-only.net
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