From mboxrd@z Thu Jan 1 00:00:00 1970 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on inbox.vuxu.org X-Spam-Level: X-Spam-Status: No, score=-1.6 required=5.0 tests=MAILING_LIST_MULTI, RCVD_IN_DNSWL_MED,RCVD_IN_MSPIKE_H3,RCVD_IN_MSPIKE_WL,URIBL_BLACK autolearn=ham autolearn_force=no version=3.4.4 Received: (qmail 31363 invoked from network); 21 Apr 2021 17:39:07 -0000 Received: from mother.openwall.net (195.42.179.200) by inbox.vuxu.org with ESMTPUTF8; 21 Apr 2021 17:39:07 -0000 Received: (qmail 25863 invoked by uid 550); 21 Apr 2021 17:39:02 -0000 Mailing-List: contact musl-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-ID: Reply-To: musl@lists.openwall.com Received: (qmail 25845 invoked from network); 21 Apr 2021 17:39:01 -0000 Date: Wed, 21 Apr 2021 13:38:48 -0400 From: Rich Felker To: =?utf-8?B?w4lyaWNv?= Nogueira , musl@lists.openwall.com Message-ID: <20210421173848.GS2546@brightrain.aerifal.cx> References: <20210420191519.23822-1-ericonr@disroot.org> <20210420191519.23822-5-ericonr@disroot.org> <20210421082458.GI2799122@port70.net> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20210421082458.GI2799122@port70.net> User-Agent: Mutt/1.5.21 (2010-09-15) Subject: Re: [musl] [PATCH] shorten __aeabi_memset by one instruction On Wed, Apr 21, 2021 at 10:24:58AM +0200, Szabolcs Nagy wrote: > * Érico Nogueira [2021-04-20 16:15:19 -0300]: > > when building for armhf, this makes libc.so text smaller by 4 bytes: > > 606619 to 606615 > > --- > > src/string/arm/__aeabi_memset.s | 3 +-- > > 1 file changed, 1 insertion(+), 2 deletions(-) > > > > diff --git a/src/string/arm/__aeabi_memset.s b/src/string/arm/__aeabi_memset.s > > index f9f60583..980774e8 100644 > > --- a/src/string/arm/__aeabi_memset.s > > +++ b/src/string/arm/__aeabi_memset.s > > @@ -24,8 +24,7 @@ __aeabi_memset: > > cmp r1, #0 > > beq 2f > > adds r1, r0, r1 > > -1: strb r2, [r0] > > - adds r0, r0, #1 > > +1: strb r2, [r0], #1 > > this is not available before armv7 as thumb instruction (and it > has 32bit thumb encoding, so you replace two 16bit instructions > with a 32bit one.) > > normally this asm is compiled in arm mode even if your toolchain > defaults to thumb (i'm not sure why), but if you select a cpu or > arch that only supports thumb then the assembler will try to use > thumb and fail e.g. on -march=armv6-m (but i'm not sure if musl > supports that compilation mode throughout) Should we hold off on doing anything about this for now then? I'd rather avoid making more work for future, and this is pure *junk* code that we do not expect to be called from anywhere (it's extremely slow) and only there to satisfy broken tooling generating calls to it rather than to the standard functions. Rich