[Bug middle-end/43861] New: -Os creates larger binaries than before in some cases (-falign-... options enabled)

[rwahl at gmx dot de]

Hi,

I just noticed that some of my libraries are greater when compiled with gcc
4.4.3 instead of gcc 4.3.2. Diffing the output of "gcc --help=optimizers -Q
-Os" shows this in 4.3.2:

  -falign-jumps                        [disabled]
  -falign-labels                       [disabled]
  -falign-loops                        [enabled]

and this for 4.4.3:

  -falign-functions                     [enabled]
  -falign-jumps                         [enabled]
  -falign-labels                        [enabled]
  -falign-loops                         [disabled]

when explicitely disabling the alignment options then the code size shrinks.
For libxml2 in my case from 704256 to 675584 bytes.

The manual says:

  -Os disables the following optimization flags: -falign-functions
           -falign-jumps  -falign-loops -falign-labels  -freorder-blocks
           -freorder-blocks-and-partition -fprefetch-loop-arrays
           -ftree-vect-loop-version

which is not true (even not for 4.3.2 since loop alignment was enabled). Some
other opts like -freorder-blocks is enabled as well.

So is this actually a bug or is the documentation outdated or even both?


-- 
           Summary: -Os creates larger binaries than before in some cases (-
                    falign-... options enabled)
           Product: gcc
           Version: 4.4.3
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: middle-end
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: rwahl at gmx dot de


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43861