Andrew Haley [EMAIL PROTECTED] writes:
It appears that memory references to arrays aren't being hoisted out
of loops: in this test case, gcc 3.4 doesn't touch memory at all in
the loop, but 4.3pre (and 4.2, etc) does.
Here's the test case:
void foo(int *a)
{ int i;
for (i
On 05 Jan 2007 07:18:47 -0800, Ian Lance Taylor [EMAIL PROTECTED] wrote:
At the tree level, the problem is that the assignment to a[0] is seen
as aliasing a[1]. This causes the use of a[1] to look like a USE of
an SMT, and the assignment to a[0] to look like a DEF of the same
SMT. So in
On 1/5/07, Andrew Haley [EMAIL PROTECTED] wrote:
This is from the gcc-help mailing list. It's mentioned there for ARM,
but it's just as bad for x86-64.
It appears that memory references to arrays aren't being hoisted out
of loops: in this test case, gcc 3.4 doesn't touch memory at all in
the
Steven Bosscher writes:
Steven What does the code look like if you compile with -O2 -fgcse-sm?
Yep. Mark and I recently discussed whether gcse-sm should be
enabled by default at some optimization level. We're hiding performance
from GCC users.
David
Steven Bosscher writes:
On 1/5/07, Andrew Haley [EMAIL PROTECTED] wrote:
This is from the gcc-help mailing list. It's mentioned there for ARM,
but it's just as bad for x86-64.
It appears that memory references to arrays aren't being hoisted out
of loops: in this test case, gcc
On 1/5/07, David Edelsohn [EMAIL PROTECTED] wrote:
Steven Bosscher writes:
Steven What does the code look like if you compile with -O2 -fgcse-sm?
Yep. Mark and I recently discussed whether gcse-sm should be
enabled by default at some optimization level. We're hiding performance
- Message d'origine
De : Steven Bosscher [EMAIL PROTECTED]
À : David Edelsohn [EMAIL PROTECTED]
Cc : Andrew Haley [EMAIL PROTECTED]; gcc@gcc.gnu.org
Envoyé le : Vendredi, 5 Janvier 2007, 17h55mn 47s
Objet : Re: gcc 3.4 mainline performance regression
On 1/5/07, David Edelsohn [EMAIL PROTECTED
Please don't top-post. It's very confusing.
Mick CORNUT writes:
I don't know exactly if I've understood all your previous
explanation (excepted the load store motion part), but we pointed
out 2 different problems:
Pb n°1: depending on the optimization level -03, a[0] and a[1] are
On 05 Jan 2007 07:18:47 -0800, Ian Lance Taylor [EMAIL PROTECTED] wrote:
Andrew Haley [EMAIL PROTECTED] writes:
It appears that memory references to arrays aren't being hoisted out
of loops: in this test case, gcc 3.4 doesn't touch memory at all in
the loop, but 4.3pre (and 4.2, etc) does.
