[Bug c++/27140] New: Compiling LLVM now takes nearly 5x as long with 4.1 as it did with 4.0

[Bug c++/27140] New: Compiling LLVM now takes nearly 5x as long with 4.1 as it did with 4.0

[rspencer at x10sys dot com]

I'm compiling the LLVM compiler infrastructure and have noticed that GCC 4.1
takes an excessively long time to compile versus GCC 4.0. In particular, one
file (albeit 2 million source lines) takes over 10 minutes (618.97 seconds) of
CPU time to compile. On the exact same source, GCC 4.0.2 takes just over 2
minutes (130.68 seconds). GCC 3.4 was even faster (from memory).

Here are the heavy-hitters (from -ftime-report) from highest to lowest:
                        usr           sys         wall          mem  
tree SSA incremental  : 172.76 (30%)  0.61 ( 1%)  175.39 (22%)  9356kB ( 1%)
ggc
tree PHI insertion    :  55.86 (10%)  0.30 ( 1%)   57.54 ( 7%)  6346kB ( 1%)
ggc
dominance frontiers   :  40.15 ( 7%)  0.10 ( 0%)   40.02 ( 5%)     0kB ( 0%)
ggc
dominator optimization:  24.50 ( 4%)  0.57 ( 1%)   34.06 ( 4%) 74359kB ( 8%)
ggc
tree PTA              :  19.51 ( 3%)  1.44 ( 3%)   22.90 ( 3%) 15806kB ( 2%)
ggc
PRE                   :  19.09 ( 3%)  6.52 (15%)   27.10 ( 3%)  1960kB ( 0%)
ggc
TOTAL                 : 576.55       42.42        794.94       957564 kB

Attached is a tarball that contains pre-compiled source code, and the timing
statistics for both 4.0.2 and 4.1.0 as generated by GCC. 

This problem may have already been reported by or related to the following
bugs:
bug 18419, bug 17895, bug 17596.

Another thing to note. The object file for 4.1.0 is 21% larger than for 4.0.2
(1454880 vs 1759292).

Platform: (Linux FC3 with updates):
Linux 2.6.12-1.1381_FC3smp #1 SMP Fri Oct 21 04:03:26 EDT 2005 i686 i686 i386
GNU/Linux

gcc -v: (slow)
Using built-in specs.
Target: i686-pc-linux-gnu
Configured with: ../gcc-4.1.0/configure --prefix=/proj/install
--enable-languages=c,c++,java --with-gnuas --with-gnuld
Thread model: posix
gcc version 4.1.0

gcc -v: (fast)
Using built-in specs.
Target: i686-pc-linux-gnu
Configured with: ../svn/configure --prefix=/proj/install2
--enable-languages=c,c++ --with-gnuld --with-gnuas
Thread model: posix
gcc version 4.0.2


-- 
           Summary: Compiling LLVM now takes nearly 5x as long with 4.1 as
                    it did with 4.0
           Product: gcc
           Version: 4.1.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: rspencer at x10sys dot com
 GCC build triplet: i686-pc-linux-gnu
  GCC host triplet: i686-pc-linux-gnu
GCC target triplet: i686-pc-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=27140

[Bug c++/27140] Compiling LLVM now takes nearly 5x as long with 4.1 as it did with 4.0

[rspencer at x10sys dot com]

------- Comment #1 from rspencer at x10sys dot com  2006-04-13 07:48 -------
Created an attachment (id=11253)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=11253&action=view)
source code and -ftime-report output for both 4.0.2 and 4.1.0

This tarball contains 2MB of pre-compiled source code (slow.cpp) as well as two
output files (slow.out=4.1.0 and fast.out=4.0.2). These contain the command
lines used, the "gcc -v" output and the "gcc -ftime-report" output.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=27140

[Bug tree-optimization/27140] Compiling LLVM now takes nearly 5x as long with 4.1 as it did with 4.0

[pinskia at gcc dot gnu dot org]

------- Comment #2 from pinskia at gcc dot gnu dot org  2006-04-13 16:30 -------
I bet it has nothing to do with those but instead PR 26830.

Just a quick question since you might know before I go looking into the source.
Does this source has a big switch and a couple of loops in it?
If it does this almost for sure PR 26830 fixed part of the compile time issue,
at least for 4.1.1.


-- 

pinskia at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |pinskia at gcc dot gnu dot
                   |                            |org
          Component|c++                         |tree-optimization
           Keywords|                            |compile-time-hog


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=27140

[Bug tree-optimization/27140] Compiling LLVM now takes nearly 5x as long with 4.1 as it did with 4.0

[sabre at nondot dot org]

------- Comment #3 from sabre at nondot dot org  2006-04-13 16:31 -------
Note: "(albeit 2 million source lines)" isn't right, it's only 79K LOC. :)

-Chris


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=27140

[Bug tree-optimization/27140] Compiling LLVM now takes nearly 5x as long with 4.1 as it did with 4.0

[rspencer at x10sys dot com]

------- Comment #4 from rspencer at x10sys dot com  2006-04-13 17:26 -------
Re: 2 million lines:
Yes, my apologies for the late night blunder. It is 2,231,753 bytes and 79,037
lines.

Re: large switch statements:
There are several switch statements, none of them large. The largest is about
200 lines of code. None have more than 100 cases. The 200 line one only a few
cases with some complex if/else code in each case.  You'll have to look at the
source yourself to get a better idea of "complex"


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=27140

[Bug tree-optimization/27140] Compiling LLVM now takes nearly 5x as long with 4.1 as it did with 4.0

[rspencer at x10sys dot com]

------- Comment #5 from rspencer at x10sys dot com  2006-04-13 20:13 -------
Created an attachment (id=11260)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=11260&action=view)
Timing results when using GCC 4.1.1

This attachment provides the -ftime-report output for the same compilation but
with GCC 4.1.1 (prerelease).  This takes about 1/2 the time as 4.1.0 but is
still twice the time of 4.0.2.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=27140

[Bug tree-optimization/27140] Compiling LLVM now takes nearly 5x as long with 4.1 as it did with 4.0

[rspencer at x10sys dot com]

------- Comment #6 from rspencer at x10sys dot com  2006-04-13 20:30 -------
Created an attachment (id=11261)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=11261&action=view)
Timing results with -fno-tree-salias

Andrew Pinskia suggested that I try -fno-tree-salias. This decreased
compilation time by about 10% (244 secs vs 265 secs). 


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=27140

[Bug tree-optimization/27140] Compiling LLVM now takes nearly 5x as long with 4.1 as it did with 4.0

[dberlin at dberlin dot org]

------- Comment #7 from dberlin at gcc dot gnu dot org  2006-04-13 22:40 -------
Subject: Re:  Compiling LLVM now takes nearly 5x as long with 4.1 as it did
with 4.0


On Apr 13, 2006, at 1:30 PM, rspencer at x10sys dot com wrote:

>
>
> ------- Comment #6 from rspencer at x10sys dot com  2006-04-13  
> 20:30 -------
> Created an attachment (id=11261)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=11261&action=view)
>  --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=11261&action=view)
> Timing results with -fno-tree-salias
>
> Andrew Pinskia suggested that I try -fno-tree-salias. This decreased
> compilation time by about 10% (244 secs vs 265 secs).

Only by virtue of the fact that you have a smaller number of phi nodes.
It's not going to give an order of magnitude improvement here.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=27140

Re: [Bug tree-optimization/27140] Compiling LLVM now takes nearly 5x as long with 4.1 as it did with 4.0

[Daniel Berlin]

On Apr 13, 2006, at 1:30 PM, rspencer at x10sys dot com wrote:

>
>
> ------- Comment #6 from rspencer at x10sys dot com  2006-04-13  
> 20:30 -------
> Created an attachment (id=11261)
>  --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=11261&action=view)
> Timing results with -fno-tree-salias
>
> Andrew Pinskia suggested that I try -fno-tree-salias. This decreased
> compilation time by about 10% (244 secs vs 265 secs).

Only by virtue of the fact that you have a smaller number of phi nodes.
It's not going to give an order of magnitude improvement here.

[Bug tree-optimization/27140] Compiling LLVM now takes nearly 5x as long with 4.1 as it did with 4.0

[rguenth at gcc dot gnu dot org]

------- Comment #8 from rguenth at gcc dot gnu dot org  2006-04-17 10:16 -------
This may be fixed by Zdeneks optimization of phi argument rewrite and dominator
updating.  Though I bet these are not appropriate for 4.1.1.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=27140

[Bug tree-optimization/27140] Compiling LLVM now takes nearly 5x as long with 4.1 as it did with 4.0

[rspencer at x10sys dot com]

------- Comment #9 from rspencer at x10sys dot com  2006-04-21 23:12 -------
Andrew Pinskia wanted me to mention that there are other source files in LLVM
that exhibit the slow down. The one I attached is the worst offender, but there
are others. Unfortunately, I don't remember which files and I removed GCC 4.1
from my system so I can't easily find out. If you build LLVM with GCC 4.1,
you'll quickly discover which files are the slow ones.


-- 

rspencer at x10sys dot com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |rspencer at x10sys dot com


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=27140

[Bug tree-optimization/27140] Compiling LLVM now takes nearly 5x as long with 4.1 as it did with 4.0

[rspencer at x10sys dot com]

------- Comment #10 from rspencer at x10sys dot com  2006-10-17 22:42 -------
This is still a problem with:
gcc (GCC) 4.1.1 20060525 (Red Hat 4.1.1-1)

Additionally, link times are much longer than with 3.4.6


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=27140

Re: [Bug tree-optimization/27140] Compiling LLVM now takes nearly 5x as long with 4.1 as it did with 4.0

[Andrew Pinski]

> Additionally, link times are much longer than with 3.4.6

Link times are usually a binutils issue unless you are comparing
with the same version of binutils.

-- Pinski

[Bug tree-optimization/27140] Compiling LLVM now takes nearly 5x as long with 4.1 as it did with 4.0

[pinskia at physics dot uc dot edu]

------- Comment #11 from pinskia at physics dot uc dot edu  2006-10-17 22:44 -------
Subject: Re:  Compiling LLVM now takes nearly 5x as long with 4.1 as it did
with 4.0

> Additionally, link times are much longer than with 3.4.6

Link times are usually a binutils issue unless you are comparing
with the same version of binutils.

-- Pinski


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=27140

[Bug tree-optimization/27140] Compiling LLVM now takes nearly 5x as long with 4.1 as it did with 4.0

[rguenth at gcc dot gnu dot org]

------- Comment #12 from rguenth at gcc dot gnu dot org  2008-01-26 22:57 -------
How is the situation with 4.2 or 4.3?


-- 

rguenth at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |WAITING


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=27140

[Bug tree-optimization/27140] Compiling LLVM now takes nearly 5x as long with 4.1 as it did with 4.0

[pinskia at gcc dot gnu dot org]

------- Comment #13 from pinskia at gcc dot gnu dot org  2008-09-03 02:12 -------
2008-05-08  Richard Guenther  <rguenther@suse.de>

Remove struct aliasing which fixed some compile time, there were other patches
too like mem-ssa.
But it would be nice if we could get new compile time numbers here.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=27140

[Bug tree-optimization/27140] Compiling LLVM now takes nearly 5x as long with 4.1 as it did with 4.0

[jessieluv22 at gmail dot com]

------- Comment #14 from jessieluv22 at gmail dot com  2009-08-14 16:27 -------
Created an attachment (id=18364)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=18364&action=view)
 Witha butterfil on a flower

 It is a   beautiful fly with colorful wings


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=27140