Re: optimization/6588: throw() takes 20,000 cycles : is it expected ?

Re: optimization/6588: throw() takes 20,000 cycles : is it expected ?

[Richard Henderson]

The following reply was made to PR optimization/6588; it has been noted by GNATS.

From: Richard Henderson <rth@redhat.com>
To: Sylvain.Pion@sophia.inria.fr
Cc: gcc-gnats@gcc.gnu.org
Subject: Re: optimization/6588: throw() takes 20,000 cycles : is it expected ?
Date: Wed, 8 May 2002 14:56:51 -0700

 On Mon, May 06, 2002 at 11:35:50PM -0000, Sylvain.Pion@sophia.inria.fr wrote:
 > The sequence throw/catch appears to take about 20,000 cycles
 > on a Pentium III.  Is this expected ?
 
 Not unexpected.
 
 > Is there a way to speed this up ?
 
 I doubt it.
 
 
 r~

Re: optimization/6588: throw() takes 20,000 cycles : is it expected ?

[Richard Henderson]

The following reply was made to PR optimization/6588; it has been noted by GNATS.

From: Richard Henderson <rth@redhat.com>
To: Sylvain Pion <Sylvain.Pion@sophia.inria.fr>
Cc: gcc-gnats@gcc.gnu.org
Subject: Re: optimization/6588: throw() takes 20,000 cycles : is it expected ?
Date: Wed, 8 May 2002 15:10:47 -0700

 On Wed, May 08, 2002 at 11:58:18PM +0200, Sylvain Pion wrote:
 > I made some benchmarks with the SunPro compiler, and it's 20 times faster.
 > (maybe it's not as correct as GCC, though)
 
 One of the changes for gcc 3.0 (that probably made it slower)
 is that we support throwing exceptions between languages.
 
 
 r~

Re: optimization/6588: throw() takes 20,000 cycles : is it expected ?

[Sylvain Pion]

The following reply was made to PR optimization/6588; it has been noted by GNATS.

From: Sylvain Pion <Sylvain.Pion@sophia.inria.fr>
To: Richard Henderson <rth@redhat.com>
Cc: Sylvain.Pion@sophia.inria.fr, gcc-gnats@gcc.gnu.org
Subject: Re: optimization/6588: throw() takes 20,000 cycles : is it expected ?
Date: Wed, 8 May 2002 23:58:18 +0200

 On Wed, May 08, 2002 at 02:56:51PM -0700, Richard Henderson wrote:
 > > The sequence throw/catch appears to take about 20,000 cycles
 > > on a Pentium III.  Is this expected ?
 > 
 > Not unexpected.
 
 :(
 
 > > Is there a way to speed this up ?
 > 
 > I doubt it.
 
 :((
 
 I made some benchmarks with the SunPro compiler, and it's 20 times faster.
 (maybe it's not as correct as GCC, though)
 
 -- 
 Sylvain

optimization/6588: throw() takes 20,000 cycles : is it expected ?

[Sylvain.Pion]

>Number:         6588
>Category:       optimization
>Synopsis:       throw() takes 20,000 cycles : is it expected ?
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    unassigned
>State:          open
>Class:          pessimizes-code
>Submitter-Id:   net
>Arrival-Date:   Mon May 06 16:36:00 PDT 2002
>Closed-Date:
>Last-Modified:
>Originator:     Sylvain Pion
>Release:        3.1 and 3.2
>Organization:
>Environment:
Reading specs from /u/zosma/0/prisme/spion/gcc/Linux_trunc/lib/gcc-lib/i686-pc-linux-gnu/3.2/specs
Configured with: /u/zosma/0/prisme/spion/gcc/gcc_trunc/configure --disable-shared --disable-nls --enable-languages=c++ --prefix=/u/zosma/0/prisme/spion/gcc/Linux_trunc --with-gnu-as --with-gnu-ld --with-as=/u/zosma/0/prisme/spion/gcc/Binutils/Linux/bin/as --with-ld=/u/zosma/0/prisme/spion/gcc/Binutils/Linux/bin/ld
Thread model: single
gcc version 3.2 20020505 (experimental)
>Description:
The sequence throw/catch appears to take about 20,000 cycles
on a Pentium III.  Is this expected ?
Is there a way to speed this up ?
Even if this sequence is not supposed to happen often, the
fact that it's very slow can have a visible impact on global
performance.
>How-To-Repeat:
// Compile with optimization the following code,
// It takes more than 20 seconds to execute on my
// Pentium III at 933 MHz.
int main()
{
  for (int i=0; i<1000000; ++i)
  {
    try {
      throw(0);
    }
    catch (...) {
    }
  }
}
>Fix:

>Release-Note:
>Audit-Trail:
>Unformatted: