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From: Falk Hueffner <falk.hueffner@student.uni-tuebingen.de> To: nobody@gcc.gnu.org Cc: gcc-prs@gcc.gnu.org, Subject: Re: target/6882: [SPARC] Useless stack adjustment code Date: Mon, 31 Mar 2003 09:47:00 -0000 [thread overview] Message-ID: <20030331085601.9390.qmail@sources.redhat.com> (raw) The following reply was made to PR target/6882; it has been noted by GNATS. From: Falk Hueffner <falk.hueffner@student.uni-tuebingen.de> To: Eric Botcazou <ebotcazou@libertysurf.fr> Cc: Hans-Peter Nilsson <hp@bitrange.com>, <dann@godzilla.ics.uci.edu>, <gcc-bugs@gcc.gnu.org>, <nobody@gcc.gnu.org>, <gcc-gnats@gcc.gnu.org> Subject: Re: target/6882: [SPARC] Useless stack adjustment code Date: 31 Mar 2003 10:50:21 +0200 Eric Botcazou <ebotcazou@libertysurf.fr> writes: > > No, it seems a valid optimization request to not emit the > > stack-adjustment code. Could you find a *specific* reason for > > the stack-adjustment code? (Please state that in the PR.) > > No, I don't see a "specific" reason. But: > - functions from the same translation unit that call it (and that appear > after it in normal mode, but the restriction is lifted with > -funit-at-a-time) don't actually emit the call, > - would the benefit be worth it in real life, given that the costly operation > is to call the function itself (for nothing)? I think the real optimization > is not to emit the call at all. Don't know about SPARC, but on Alpha, this also occurs with non-nop functions: struct s2 { unsigned long a, b; }; unsigned long f8(struct s2 x) { return x.a + x.b; } 0000000000000000 <f8>: 0: 00 04 11 42 addq a0,a1,v0 4: f0 ff de 23 lda sp,-16(sp) 8: 10 00 de 23 lda sp,16(sp) c: 01 80 fa 6b ret While the optimization certainly isn't that important, it also seems to be not too difficult, and the code size saving is also nice. -- Falk
next reply other threads:[~2003-03-31 8:56 UTC|newest] Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top 2003-03-31 9:47 Falk Hueffner [this message] -- strict thread matches above, loose matches on Subject: below -- 2003-03-31 14:36 Eric Botcazou 2003-03-31 12:46 Hans-Peter Nilsson 2003-03-31 8:56 Eric Botcazou 2003-03-31 5:06 hp 2003-03-31 4:18 Hans-Peter Nilsson 2003-03-29 9:51 ebotcazou
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