From: Jason Merrill <jason@redhat.com>
To: gcc@gcc.gnu.org
Subject: [tree-ssa] Simplifying TARGET_EXPR
Date: Tue, 16 Jul 2002 09:52:00 -0000 [thread overview]
Message-ID: <wvlptxoousm.fsf@prospero.cambridge.redhat.com> (raw)
Thinking about simplifying TARGET_EXPR, I see two issues to be dealt with:
1) expand_expr's treatment of TARGET_EXPR depends on whether or not it is
being expanded with a target: if so, it initializes the target object;
if not, it initializes a new object. There's no way to model that
behavior with the current simplification code, as there's no concept
of 'target'.
However, I think that the copy-elision should only occur under an
INIT_EXPR, so we can check for TARGET_EXPR in simplify_modify_expr.
This should work fine.
2) Passing a TARGET_EXPR to a call means initializing the temporary on the
stack and passing its address to the call. There's no way to express
this in a simplified form; if we replace the TARGET_EXPR with the
variable it initializes, expand_call will make a bitwise copy, which is
wrong. I can think of two solutions to this:
a) Change expand_call to not copy variables with DECL_ARTIFICIAL set.
b) Pass an ADDR_EXPR of the variable instead, and change expand_call
to handle that case.
My preference is for (b), as (a) might have unintended consequences.
Thoughts?
Jason
next reply other threads:[~2002-07-16 10:22 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-07-16 9:52 Jason Merrill [this message]
2002-07-20 18:54 Jason Merrill
2002-07-21 0:41 ` Richard Henderson
2002-07-21 17:32 ` Mark Mitchell
2002-07-21 18:04 ` Gabriel Dos Reis
2002-07-21 18:14 ` Mark Mitchell
2002-07-21 20:39 ` Gabriel Dos Reis
2002-07-22 8:32 ` Michael Matz
2002-07-22 12:02 ` Gabriel Dos Reis
2002-07-24 3:22 ` Mark Mitchell
2002-07-22 12:33 ` Nathan Sidwell
2002-07-22 12:53 ` Gabriel Dos Reis
2002-07-22 13:10 ` Jason Merrill
2002-07-21 22:35 ` Jason Merrill
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=wvlptxoousm.fsf@prospero.cambridge.redhat.com \
--to=jason@redhat.com \
--cc=gcc@gcc.gnu.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).