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From: "rth at gcc dot gnu dot org" <gcc-bugzilla@gcc.gnu.org>
To: java-prs@gcc.gnu.org
Subject: [Bug rtl-optimization/17731] sub-optimal code generated for left shift
Date: Wed, 29 Sep 2004 19:39:00 -0000	[thread overview]
Message-ID: <20040929193947.5399.qmail@sourceware.org> (raw)
In-Reply-To: <20040929175802.17731.tromey@gcc.gnu.org>


------- Additional Comments From rth at gcc dot gnu dot org  2004-09-29 19:39 -------
This will be done properly if SHIFT_COUNT_TRUNCATED is true.

The problem is that SHIFT_COUNT_TRUNCATED applies to *all* shifts and at
the given mode size.  Which is not true for x86, since HImode shifts are
still masked to 31, not 15.

Ideally we'd extend Richard Sandiford's new target.shift_truncation_mask
such that it can replace SHIFT_COUNT_TRUNCATED.

In the short term, Java could examine shift_truncation_mask and avoid
creating the AND at the tree level in the first place.

Not sure whether "middle-end" or "rtl-opt" is a better category, but this
is definitely not target-specific and thus "target" doesn't apply.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
          Component|target                      |rtl-optimization


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17731


  parent reply	other threads:[~2004-09-29 19:39 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2004-09-29 17:58 [Bug java/17731] New: " tromey at gcc dot gnu dot org
2004-09-29 18:05 ` [Bug java/17731] " pinskia at gcc dot gnu dot org
2004-09-29 18:09 ` tromey at gcc dot gnu dot org
2004-09-29 18:11 ` pinskia at gcc dot gnu dot org
2004-09-29 18:14 ` [Bug target/17731] " pinskia at gcc dot gnu dot org
2004-09-29 18:16 ` pinskia at gcc dot gnu dot org
2004-09-29 19:39 ` rth at gcc dot gnu dot org [this message]
2004-09-29 21:03 ` [Bug rtl-optimization/17731] " tromey at gcc dot gnu dot org
     [not found] <bug-17731-8172@http.gcc.gnu.org/bugzilla/>
2011-05-22 15:52 ` steven at gcc dot gnu.org

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