[Bug c++/18418] New: GCC 3.4.3 builds worse code than GCC 3.3.4 using template expressions

[Bug c++/18418] New: GCC 3.4.3 builds worse code than GCC 3.3.4 using template expressions

[ayqazi at yahoo dot co dot uk]

Hi,

Using a template expressions 3D maths library I'm developing, I have discovered
that GCC 3.4.3 builds worse code than GCC 3.3.4 (and predecessors.)

I have attached a test case file using a part of the template expression library
that highlights this case.

Regardless of which -march flag I used to compile it (i386, etc.) and regardless
of the -msse flag being present or not, the asm output was clearly longer by
about 20% in the gcc 3.4.3 compiled code.

p.s. it will work if an optimisation flag is present (I have verified it.) 
Without an optimisation flag, GCC doesn't generate proper code (this bug has
already been reported.)

-- 
           Summary: GCC 3.4.3 builds worse code than GCC 3.3.4 using
                    template expressions
           Product: gcc
           Version: 3.4.3
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: ayqazi at yahoo dot co dot uk
                CC: gcc-bugs at gcc dot gnu dot org
 GCC build triplet: i686-linux
  GCC host triplet: i686-linux
GCC target triplet: i686-linux


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18418

[Bug c++/18418] GCC 3.4.3 builds worse code than GCC 3.3.4 using template expressions

[ayqazi at yahoo dot co dot uk]

------- Additional Comments From ayqazi at yahoo dot co dot uk  2004-11-10 13:54 -------
Created an attachment (id=7516)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=7516&action=view)
Test case for differences in GCC 3.4.3 and 3.3.4 template expression code gen

Compile to assembler (e.g. g++ -S -O) using same flags with both a GCC 3.3
series compiler, and a GCC 3.4 series compiler and spot the file length
difference - you MUST use an optimisation flag for it to compile correctly
(another bug, already submitted.)


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18418

[Bug c++/18418] [3.4 only] GCC 3.4.3 builds worse code than GCC 3.3.4 using template expressions

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2004-11-10 14:07 -------
First this is invalid code as explained in PR 18415.
Second this works fine on the mainline as get close to optimial code.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |missed-optimization
      Known to work|                            |4.0.0 3.3.3
            Summary|GCC 3.4.3 builds worse code |[3.4 only] GCC 3.4.3 builds
                   |than GCC 3.3.4 using        |worse code than GCC 3.3.4
                   |template expressions        |using template expressions
   Target Milestone|---                         |3.4.4


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18418

[Bug c++/18418] [3.4 only] GCC 3.4.3 builds worse code than GCC 3.3.4 using template expressions

[giovannibajo at libero dot it]

------- Additional Comments From giovannibajo at libero dot it  2004-11-10 18:52 -------
Notice that I would prefer to see a runtime benchmark before confirming this 
bug. A 20% increase in code size could probably be caused by better inlining -- 
it does not automatically means that the code is slower unless you prove 
otherwise.

If you compile with -O2, you should test run-time speed with a run-time 
benchmark: try doing some calculations and time them with different compilers. 
If you care about code size, try with -Os.

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18418

[Bug c++/18418] [3.4 only] GCC 3.4.3 builds worse code than GCC 3.3.4 using template expressions

[bangerth at dealii dot org]

------- Additional Comments From bangerth at dealii dot org  2005-02-09 19:24 -------
There's also other stuff lurking in assembler files, such as a lot of 
notes for labels. These aren't code, and I've seen cases where newer 
compilers output more labels than older ones for some reason. 
 
Unless you show us some run-time comparisons, I guess there isn't much 
willingness here to do something about it. I'll put this PR into "waiting" 
state. 
 
Thanks 
  Wolfgang 

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


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18418

[Bug c++/18418] [3.4 only] GCC 3.4.3 builds worse code than GCC 3.3.4 using template expressions

[ayqazi at yahoo dot co dot uk]

------- Additional Comments From ayqazi at yahoo dot co dot uk  2005-02-10 17:23 -------
Once GCC 4.0 is out, I'll experiment with it and submit test cases etc. for it.
 No use trying to fix an older release's optimisations IMHO.

Thanks anyway.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|WAITING                     |SUSPENDED


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18418

[Bug c++/18418] [3.4 only] GCC 3.4.3 builds worse code than GCC 3.3.4 using template expressions

[mmitchel at gcc dot gnu dot org]

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|3.4.4                       |3.4.5


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18418

[Bug c++/18418] [3.4 only] GCC 3.4.3 builds worse code than GCC 3.3.4 using template expressions

[gdr at gcc dot gnu dot org]

------- Comment #6 from gdr at gcc dot gnu dot org  2006-02-28 09:44 -------
won't fix for 3.4.6


-- 

gdr at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|SUSPENDED                   |RESOLVED
         Resolution|                            |WONTFIX


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18418

[Bug c++/18418] [3.4 only] GCC 3.4.3 builds worse code than GCC 3.3.4 using template expressions

[gdr at gcc dot gnu dot org]

-- 

gdr at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|3.4.5                       |3.4.6


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18418