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From: "rguenth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/63798] [5.0 regression] FAIL: gcc.target/powerpc/ppc-fmadd-1.c scan-assembler-not f(add|sub|mul|neg)
Date: Mon, 10 Nov 2014 09:57:00 -0000 [thread overview]
Message-ID: <bug-63798-4-suT3QFpmPh@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-63798-4@http.gcc.gnu.org/bugzilla/>
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63798
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Keywords| |missed-optimization
Status|UNCONFIRMED |ASSIGNED
Last reconfirmed| |2014-11-10
CC|rguenther at suse dot de |rguenth at gcc dot gnu.org
Assignee|unassigned at gcc dot gnu.org |rguenth at gcc dot gnu.org
Target Milestone|--- |5.0
Ever confirmed|0 |1
--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
There are four fneg instructions present still with r217281. I suppose
fneg 0,10
fmadd 0,11,0,12
...
fneg 0,10
fmsub 0,11,0,12
...
fneg 12,12
fmadds 0,11,12,0
...
fneg 0,0
fmsubs 0,12,0,11
should have been combined with the following instruction.
I don't see anything wrong here but eventually that
_65 = -_64;
_67 = _63 * _65 + _62;
has canonicalized operand order so that the negate is not always the
first operand of the embedded multiply?
>From expr.c:
def0 = get_def_for_expr (treeop0, NEGATE_EXPR);
def2 = get_def_for_expr (treeop2, NEGATE_EXPR);
...
indeed it doesn't consider the multiply is commutative.
I have a patch.
next parent reply other threads:[~2014-11-10 9:57 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <bug-63798-4@http.gcc.gnu.org/bugzilla/>
2014-11-10 9:57 ` rguenth at gcc dot gnu.org [this message]
2014-11-10 14:07 ` rguenth at gcc dot gnu.org
2014-11-10 14:07 ` rguenth at gcc dot gnu.org
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