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From: "jv244 at cam dot ac dot uk" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug fortran/40168] missing unrolling/scalarization/reassoc/free
Date: Mon, 18 May 2009 12:20:00 -0000	[thread overview]
Message-ID: <20090518121958.17879.qmail@sourceware.org> (raw)
In-Reply-To: <bug-40168-6642@http.gcc.gnu.org/bugzilla/>



------- Comment #14 from jv244 at cam dot ac dot uk  2009-05-18 12:19 -------
Created an attachment (id=17886)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=17886&action=view)
simplified testcase for common subexpressions.

Richard,

thanks very much for the first patch. I tried to get a better testcase for the
issue with the number of multiplies being too large (compile with gfortran -O3
-march=native -ffast-math -cpp test.f90). This is the newly attached
test_reassoc.f90. The module contains two equivalent subroutines S1 and S2. In
S1,  gcc manages to reduce the multiplies nearly to the optimal one (I believe
optimal is 81+81+9+9=180, gcc finds 198). In S2, which introduces a temporary
array somewhat like in the original, this doesn't happen, and the number of
multiplies is 324. Looks like the introduction of the temporary array blocks
some optimisation.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40168


  parent reply	other threads:[~2009-05-18 12:20 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2009-05-16  9:35 [Bug middle-end/40168] New: " jv244 at cam dot ac dot uk
2009-05-16  9:36 ` [Bug middle-end/40168] " jv244 at cam dot ac dot uk
2009-05-16  9:54 ` [Bug fortran/40168] " rguenth at gcc dot gnu dot org
2009-05-16 10:04 ` rguenth at gcc dot gnu dot org
2009-05-16 11:19 ` jv244 at cam dot ac dot uk
2009-05-16 11:20 ` rguenth at gcc dot gnu dot org
2009-05-16 11:31 ` jv244 at cam dot ac dot uk
2009-05-16 11:39 ` rguenther at suse dot de
2009-05-16 12:20 ` jv244 at cam dot ac dot uk
2009-05-16 12:39 ` jv244 at cam dot ac dot uk
2009-05-16 13:46 ` jvdelisle at gcc dot gnu dot org
2009-05-16 14:48 ` pinskia at gcc dot gnu dot org
2009-05-18  8:53 ` rguenth at gcc dot gnu dot org
2009-05-18 10:25 ` rguenth at gcc dot gnu dot org
2009-05-18 12:20 ` jv244 at cam dot ac dot uk [this message]
2009-05-27 11:01 ` rguenth at gcc dot gnu dot org
2009-06-06  7:08 ` jv244 at cam dot ac dot uk
2009-06-14 12:31 ` rguenther at suse dot de
2009-06-14 13:40 ` rguenth at gcc dot gnu dot org
2009-12-18 14:32 ` pault at gcc dot gnu dot org
2009-12-18 14:45 ` [Bug tree-optimization/40168] " rguenth at gcc dot gnu dot org

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