From: kenner@vlsi1.ultra.nyu.edu (Richard Kenner)
To: jason@redhat.com
Cc: gcc-patches@gcc.gnu.org
Subject: Re: [patch] for PR 18040
Date: Tue, 19 Oct 2004 23:03:00 -0000 [thread overview]
Message-ID: <10410192305.AA14845@vlsi1.ultra.nyu.edu> (raw)
I don't think anybody is suggesting that we break up reference chains
in a way that would introduce aggregate temporaries. Only things that
can be expressed like
t = &a.b;
a.b.c => t->c
"t" here is a scalar temporary, so the optimizers should be able to do
useful things with it.
But that has it's own set of problems:
(1) We're taking an address of something that didn't used to have its
address taken.
(2) Suppose a.b is not addressable? Then you *do* have to make a copy
and hence an aggregate temporary.
If a.b.c is not valid GIMPLE, then even if we had a tree combiner (and
ignoring the nonaddressable issue), we couldn't undo this pessimization.
For example, suppose A were small enough to go into a register. Taking
the address of a.b would preclude that.
next reply other threads:[~2004-10-19 23:01 UTC|newest]
Thread overview: 61+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-10-19 23:03 Richard Kenner [this message]
2004-10-19 23:13 ` Jason Merrill
-- strict thread matches above, loose matches on Subject: below --
2004-10-20 13:27 Richard Kenner
2004-10-20 0:25 Richard Kenner
2004-10-19 23:26 Richard Kenner
2004-10-19 23:22 Richard Kenner
2004-10-19 22:48 Richard Kenner
2004-10-19 23:01 ` Jason Merrill
2004-10-19 23:07 ` Zack Weinberg
2004-10-18 17:48 Richard Kenner
2004-10-18 15:42 Richard Kenner
2004-10-18 14:52 Richard Kenner
2004-10-18 15:20 ` Daniel Berlin
2004-10-18 14:38 Richard Kenner
2004-10-18 14:24 Richard Kenner
2004-10-19 22:50 ` Zack Weinberg
2004-10-18 14:22 Richard Kenner
2004-10-19 22:47 ` Zack Weinberg
2004-10-18 3:12 Richard Kenner
2004-10-18 4:02 ` Zack Weinberg
2004-10-18 4:26 ` Daniel Berlin
2004-10-18 2:46 Richard Kenner
2004-10-18 2:38 Richard Kenner
2004-10-18 3:14 ` Zack Weinberg
2004-10-18 2:35 Richard Kenner
2004-10-18 2:51 ` Zack Weinberg
2004-10-17 23:06 Richard Kenner
2004-10-17 23:45 ` Zack Weinberg
2004-10-18 0:23 ` Zack Weinberg
2004-10-17 22:30 Richard Kenner
2004-10-17 22:36 ` Andrew Pinski
2004-10-17 23:41 ` Zack Weinberg
2004-10-18 13:13 ` Florian Weimer
2004-10-18 17:24 ` Jason Merrill
2004-10-18 17:37 ` Florian Weimer
2004-10-18 18:02 ` Jason Merrill
2004-10-19 22:40 ` Zack Weinberg
2004-10-17 21:24 Richard Kenner
2004-10-17 21:43 ` Zack Weinberg
2004-10-17 21:18 Richard Kenner
2004-10-17 21:26 ` Zack Weinberg
2004-10-17 21:04 Richard Kenner
2004-10-17 21:10 ` Zack Weinberg
2004-10-19 21:36 ` Richard Henderson
2004-10-19 22:19 ` Daniel Berlin
2004-10-20 7:03 ` Jason Merrill
2004-10-19 22:51 ` Zack Weinberg
2004-10-20 0:02 ` Richard Henderson
2004-10-17 20:25 Richard Kenner
2004-10-17 20:47 ` Daniel Berlin
2004-10-17 20:17 Richard Kenner
2004-10-17 20:25 ` Daniel Berlin
2004-10-17 19:46 Richard Kenner
2004-10-17 19:46 ` Daniel Berlin
2004-10-17 19:48 ` Zdenek Dvorak
2004-10-17 20:01 ` Daniel Berlin
2004-10-17 19:28 Zdenek Dvorak
2004-10-19 21:36 ` Richard Henderson
2004-10-19 22:03 ` Zdenek Dvorak
2004-10-19 22:04 ` Andrew Pinski
2004-10-19 22:06 ` Zdenek Dvorak
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