Date: Fri, 24 Aug 2018 15:50:10 -0700 From: Andre McCurdy <armccurdy@...il.com> To: musl@...ts.openwall.com Subject: Re: [PATCH] fix build failure on arm because of missing clz instruction On Fri, Aug 24, 2018 at 3:05 PM, Szabolcs Nagy <nsz@...t70.net> wrote: > * Andre McCurdy <armccurdy@...il.com> [2018-08-24 14:58:04 -0700]: >> On Fri, Aug 24, 2018 at 12:30 PM, Szabolcs Nagy <nsz@...t70.net> wrote: >> > another arm patch, clz usage (in fma) was broken with -mthumb -march=armv5t. >> >> That conditional was originally written under the assumption that musl >> doesn't support thumb1 (so -mthumb -march=armv5t is not a supported >> configuration). >> >> Was that assumption wrong? > > the asm code in musl does not support thumb1, > but you can compile everything else with thumb1 > (the compiler does not pass -mthumb to the assembler > by default so all asm code will be in arm mode) > > so with the changed condition the build succeeds > with -mthumb -march=armv5t, but the resulting libc > will not be competely thumb code, i think that's > an improvement. Yes, I agree it's an improvement. Mostly thumb1 with a little ARM is still useful for a lot of use cases. As an aside, it seems that glibc unconditionally includes some thumb2 when targeting ARMv7, so there's precedent for mixing ARM and thumb in libc. https://sourceware.org/bugzilla/show_bug.cgi?id=23031#c15
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