From: Aldy Hernandez <aldyh@redhat.com>
To: Richard Guenther <richard.guenther@gmail.com>
Cc: Jason Merrill <jason@redhat.com>, Jeff Law <law@redhat.com>,
gcc-patches <gcc-patches@gcc.gnu.org>,
Jakub Jelinek <jakub@redhat.com>
Subject: Re: [C++0x] contiguous bitfields race implementation
Date: Fri, 29 Jul 2011 12:02:00 -0000 [thread overview]
Message-ID: <4E3216F7.10504@redhat.com> (raw)
In-Reply-To: <CAFiYyc0+mTBfXtDdNaYGExHwk3CBDK63jhehwEtMcMh+mtGbUg@mail.gmail.com>
[-- Attachment #1: Type: text/plain, Size: 885 bytes --]
On 07/28/11 06:40, Richard Guenther wrote:
> Looking at the C++ memory model what you need is indeed simple enough
> to recover here. Still this loop does quadratic work for a struct with
> N bitfield members and a function which stores into all of them.
> And that with a big constant factor as you build a component-ref
> and even unshare trees (which isn't necessary here anyway). In fact
> you could easily manually keep track of bitpos when walking adjacent
> bitfield members. An initial call to get_inner_reference on
> TREE_OPERAND (exp, 0) would give you the starting position of the record.
>
> That would still be quadratic of course.
Actually, we don't need to call get_inner_reference at all. It seems
DECL_FIELD_BIT_OFFSET has all the information we need.
How about we simplify things further as in the attached patch?
Tested on x86-64 Linux.
OK for mainline?
[-- Attachment #2: curr --]
[-- Type: text/plain, Size: 869 bytes --]
* expr.c (get_bit_range): Get field bit offset from
DECL_FIELD_BIT_OFFSET.
Index: expr.c
===================================================================
--- expr.c (revision 176891)
+++ expr.c (working copy)
@@ -4179,18 +4179,10 @@ get_bit_range (unsigned HOST_WIDE_INT *b
prev_field_is_bitfield = true;
for (fld = TYPE_FIELDS (record_type); fld; fld = DECL_CHAIN (fld))
{
- tree t, offset;
- enum machine_mode mode;
- int unsignedp, volatilep;
-
if (TREE_CODE (fld) != FIELD_DECL)
continue;
- t = build3 (COMPONENT_REF, TREE_TYPE (exp),
- unshare_expr (TREE_OPERAND (exp, 0)),
- fld, NULL_TREE);
- get_inner_reference (t, &bitsize, &bitpos, &offset,
- &mode, &unsignedp, &volatilep, true);
+ bitpos = TREE_INT_CST_LOW (DECL_FIELD_BIT_OFFSET (fld));
if (field == fld)
found_field = true;
next prev parent reply other threads:[~2011-07-29 11:43 UTC|newest]
Thread overview: 81+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-05-09 17:12 Aldy Hernandez
2011-05-09 18:04 ` Jeff Law
2011-05-09 18:05 ` Aldy Hernandez
2011-05-09 19:19 ` Jeff Law
2011-05-09 20:11 ` Aldy Hernandez
2011-05-09 20:28 ` Jakub Jelinek
2011-05-10 11:42 ` Richard Guenther
2011-05-09 20:49 ` Jason Merrill
2011-05-13 22:35 ` Aldy Hernandez
2011-05-16 21:20 ` Aldy Hernandez
2011-05-19 7:17 ` Jason Merrill
2011-05-20 9:21 ` Aldy Hernandez
2011-05-26 18:05 ` Jason Merrill
2011-05-26 18:28 ` Aldy Hernandez
2011-05-26 19:07 ` Jason Merrill
2011-05-26 20:19 ` Aldy Hernandez
2011-05-27 20:41 ` Jason Merrill
2011-07-18 13:10 ` Aldy Hernandez
2011-07-22 19:16 ` Jason Merrill
2011-07-25 17:41 ` Aldy Hernandez
2011-07-26 5:28 ` Jason Merrill
2011-07-26 18:37 ` Aldy Hernandez
2011-07-26 17:54 ` Jason Merrill
2011-07-26 17:51 ` Aldy Hernandez
2011-07-26 18:05 ` Jason Merrill
2011-07-27 15:03 ` Richard Guenther
2011-07-27 15:12 ` Richard Guenther
2011-07-27 15:53 ` Richard Guenther
2011-07-28 13:00 ` Richard Guenther
2011-07-29 2:58 ` Jason Merrill
2011-07-29 12:02 ` Aldy Hernandez [this message]
2011-07-29 11:00 ` Richard Guenther
2011-08-01 13:51 ` Richard Guenther
2011-08-05 17:28 ` Aldy Hernandez
2011-08-09 10:52 ` Richard Guenther
2011-08-09 20:53 ` Aldy Hernandez
2011-08-10 13:34 ` Richard Guenther
2011-08-15 19:26 ` Aldy Hernandez
2011-08-27 0:05 ` Aldy Hernandez
2011-08-29 12:54 ` Richard Guenther
2011-08-30 16:07 ` Aldy Hernandez
2011-08-31 8:38 ` Richard Guenther
2011-08-31 13:56 ` Richard Guenther
2011-08-31 20:37 ` Aldy Hernandez
2011-09-01 6:58 ` Richard Guenther
2011-08-30 16:53 ` Aldy Hernandez
2011-08-31 8:55 ` Richard Guenther
2011-08-31 17:24 ` Aldy Hernandez
2011-08-30 21:33 ` Aldy Hernandez
2011-08-31 8:55 ` Richard Guenther
2011-08-31 20:37 ` Aldy Hernandez
2011-09-01 7:02 ` Richard Guenther
2011-09-01 7:05 ` Arnaud Charlet
2011-09-01 14:16 ` Aldy Hernandez
2011-09-02 8:48 ` Richard Guenther
2011-09-02 12:49 ` Aldy Hernandez
2011-09-02 13:05 ` Richard Guenther
2011-09-02 20:34 ` Jeff Law
2011-09-01 14:53 ` Aldy Hernandez
2011-09-01 15:01 ` Jason Merrill
2011-09-01 15:10 ` Aldy Hernandez
2011-09-01 15:20 ` Jason Merrill
2011-09-02 8:53 ` Richard Guenther
2011-09-02 14:10 ` Jason Merrill
2011-09-02 14:38 ` Richard Guenther
2011-09-07 18:12 ` Jason Merrill
2011-07-28 19:42 ` Aldy Hernandez
2011-07-27 18:22 ` Aldy Hernandez
2011-07-28 8:52 ` Richard Guenther
2011-07-29 12:05 ` Aldy Hernandez
2011-07-28 19:58 ` Richard Guenther
2011-07-27 17:29 ` Aldy Hernandez
2011-07-27 17:57 ` Andrew MacLeod
2011-07-27 22:27 ` Joseph S. Myers
2011-07-28 8:58 ` Richard Guenther
2011-07-28 22:26 ` Aldy Hernandez
2011-07-26 20:05 ` Aldy Hernandez
2011-07-27 18:24 ` H.J. Lu
2011-07-27 20:39 ` Aldy Hernandez
2011-07-27 20:54 ` Jakub Jelinek
2011-07-27 21:00 ` Aldy Hernandez
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