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From: Craig Rodrigues <rodrigc@mediaone.net>
To: nobody@gcc.gnu.org
Cc: gcc-prs@gcc.gnu.org,
Subject: Re: optimization/5244: Dead code in simplify_logical()
Date: Mon, 28 Jan 2002 20:06:00 -0000 [thread overview]
Message-ID: <20020129040610.22341.qmail@sources.redhat.com> (raw)
The following reply was made to PR optimization/5244; it has been noted by GNATS.
From: Craig Rodrigues <rodrigc@mediaone.net>
To: gcc-gnats@gcc.gnu.org, gcc-prs@gcc.gnu.org, Kai.Tietz@onevision.de,
gcc-bugs@gcc.gnu.org, nobody@gcc.gnu.org
Cc:
Subject: Re: optimization/5244: Dead code in simplify_logical()
Date: Mon, 28 Jan 2002 23:06:21 -0500
In PR 5244:
http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=5244
you submitted a patch, which I have reproduced here
in unified context diff format. Can you explain
why this patch is necessary? I did not
understand your explanation.
Index: combine.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/combine.c,v
retrieving revision 1.183.2.8
diff -u -r1.183.2.8 combine.c
--- combine.c 2001/11/05 19:10:32 1.183.2.8
+++ combine.c 2002/01/29 03:58:03
@@ -5391,8 +5391,25 @@
If we have (and (ior A B) C), apply the distributive law and then
the inverse distributive law to see if things simplify. */
+ /* Similarly, taking advantage of the fact that
+ (and (not A) (xor B C)) == (xor (ior A B) (ior A C)) */
+
+ if (GET_CODE (op0) == NOT && GET_CODE (op1) == XOR)
+ return apply_distributive_law
+ (gen_binary (XOR, mode,
+ gen_binary (IOR, mode, XEXP (op0, 0), XEXP (op1, 0)),
+ gen_binary (IOR, mode, copy_rtx (XEXP (op0, 0)),
+ XEXP (op1, 1))));
+
+ else if (GET_CODE (op1) == NOT && GET_CODE (op0) == XOR)
+ return apply_distributive_law
+ (gen_binary (XOR, mode,
+ gen_binary (IOR, mode, XEXP (op1, 0), XEXP (op0, 0)),
+ gen_binary (IOR, mode, copy_rtx (XEXP (op1, 0)), XEXP (op0, 1))));
+
if (GET_CODE (op0) == IOR || GET_CODE (op0) == XOR)
{
+ /* ??? May we get better code, if we do this optimization anyway */
x = apply_distributive_law
(gen_binary (GET_CODE (op0), mode,
gen_binary (AND, mode, XEXP (op0, 0), op1),
@@ -5409,21 +5426,6 @@
gen_binary (AND, mode, XEXP (op1, 1),
copy_rtx (op0))));
- /* Similarly, taking advantage of the fact that
- (and (not A) (xor B C)) == (xor (ior A B) (ior A C)) */
-
- if (GET_CODE (op0) == NOT && GET_CODE (op1) == XOR)
- return apply_distributive_law
- (gen_binary (XOR, mode,
- gen_binary (IOR, mode, XEXP (op0, 0), XEXP (op1, 0)),
- gen_binary (IOR, mode, copy_rtx (XEXP (op0, 0)),
- XEXP (op1, 1))));
-
- else if (GET_CODE (op1) == NOT && GET_CODE (op0) == XOR)
- return apply_distributive_law
- (gen_binary (XOR, mode,
- gen_binary (IOR, mode, XEXP (op1, 0), XEXP (op0, 0)),
- gen_binary (IOR, mode, copy_rtx (XEXP (op1, 0)), XEXP (op0, 1))));
break;
case IOR:
--
Craig Rodrigues
http://www.gis.net/~craigr
rodrigc@mediaone.net
next reply other threads:[~2002-01-29 4:06 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-01-28 20:06 Craig Rodrigues [this message]
-- strict thread matches above, loose matches on Subject: below --
2003-02-23 20:30 neroden
2002-11-06 7:18 Wolfgang Bangerth
2002-01-29 5:36 Kai.Tietz
2002-01-03 1:56 Kai.Tietz
2002-01-02 22:51 rodrigc
2002-01-02 4:56 Kai.Tietz
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