[Bug 1271743] [NEW] Enabed flags for -Os different from man page

[giorgos000]

Public bug reported:

The flags enabled when using gcc's command-line parameter -Os are:

$ gcc -c -Q -Os --help=optimizers | grep 'align\|reorder-blocks\|prefetch-loop\|tree-vect-loop'
  -falign-functions                     [enabled]
  -falign-jumps                         [enabled]
  -falign-labels                        [enabled]
  -falign-loops                         [enabled]
  -fprefetch-loop-arrays                [enabled]
  -freorder-blocks                      [enabled]
  -freorder-blocks-and-partition        [disabled]
  -ftree-vect-loop-version              [enabled]

But according to gcc's man page: "-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"

Maybe gcc is using some wrong defaults for parameter "-Os"?

This is the default package, details follow:

$ gcc --version
gcc (Ubuntu/Linaro 4.8.1-10ubuntu9) 4.8.1
Copyright (C) 2013 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

$ gcc -v
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-linux-gnu/4.8/lto-wrapper
Target: x86_64-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Ubuntu/Linaro 4.8.1-10ubuntu9' --with-bugurl=file:///usr/share/doc/gcc-4.8/README.Bugs --enable-languages=c,c++,java,go,d,fortran,objc,obj-c++ --prefix=/usr --program-suffix=-4.8 --enable-shared --enable-linker-build-id --libexecdir=/usr/lib --without-included-gettext --enable-threads=posix --with-gxx-include-dir=/usr/include/c++/4.8 --libdir=/usr/lib --enable-nls --with-sysroot=/ --enable-clocale=gnu --enable-libstdcxx-debug --enable-libstdcxx-time=yes --enable-gnu-unique-object --enable-plugin --with-system-zlib --disable-browser-plugin --enable-java-awt=gtk --enable-gtk-cairo --with-java-home=/usr/lib/jvm/java-1.5.0-gcj-4.8-amd64/jre --enable-java-home --with-jvm-root-dir=/usr/lib/jvm/java-1.5.0-gcj-4.8-amd64 --with-jvm-jar-dir=/usr/lib/jvm-exports/java-1.5.0-gcj-4.8-amd64 --with-arch-directory=amd64 --with-ecj-jar=/usr/share/java/eclipse-ecj.jar --enable-objc-gc --enable-multiarch --disable-werror --with-arch-32=i686 --with-abi=m64 --with-multilib-list=m32,m64,mx32 --with-tune=generic --enable-checking=release --build=x86_64-linux-gnu --host=x86_64-linux-gnu --target=x86_64-linux-gnu
Thread model: posix
gcc version 4.8.1 (Ubuntu/Linaro 4.8.1-10ubuntu9)

** Affects: gcc-4.8 (Ubuntu)
     Importance: Undecided
         Status: New

-- 
You received this bug notification because you are a member of Ubuntu
Foundations Bugs, which is subscribed to gcc-4.8 in Ubuntu.
https://bugs.launchpad.net/bugs/1271743

Title:
  Enabed flags for -Os different from man page

Status in “gcc-4.8” package in Ubuntu:
  New

Bug description:
  The flags enabled when using gcc's command-line parameter -Os are:

  $ gcc -c -Q -Os --help=optimizers | grep 'align\|reorder-blocks\|prefetch-loop\|tree-vect-loop'
    -falign-functions                     [enabled]
    -falign-jumps                         [enabled]
    -falign-labels                        [enabled]
    -falign-loops                         [enabled]
    -fprefetch-loop-arrays                [enabled]
    -freorder-blocks                      [enabled]
    -freorder-blocks-and-partition        [disabled]
    -ftree-vect-loop-version              [enabled]

  But according to gcc's man page: "-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"

  Maybe gcc is using some wrong defaults for parameter "-Os"?

  This is the default package, details follow:

  $ gcc --version
  gcc (Ubuntu/Linaro 4.8.1-10ubuntu9) 4.8.1
  Copyright (C) 2013 Free Software Foundation, Inc.
  This is free software; see the source for copying conditions.  There is NO
  warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

  $ gcc -v
  Using built-in specs.
  COLLECT_GCC=gcc
  COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-linux-gnu/4.8/lto-wrapper
  Target: x86_64-linux-gnu
  Configured with: ../src/configure -v --with-pkgversion='Ubuntu/Linaro 4.8.1-10ubuntu9' --with-bugurl=file:///usr/share/doc/gcc-4.8/README.Bugs --enable-languages=c,c++,java,go,d,fortran,objc,obj-c++ --prefix=/usr --program-suffix=-4.8 --enable-shared --enable-linker-build-id --libexecdir=/usr/lib --without-included-gettext --enable-threads=posix --with-gxx-include-dir=/usr/include/c++/4.8 --libdir=/usr/lib --enable-nls --with-sysroot=/ --enable-clocale=gnu --enable-libstdcxx-debug --enable-libstdcxx-time=yes --enable-gnu-unique-object --enable-plugin --with-system-zlib --disable-browser-plugin --enable-java-awt=gtk --enable-gtk-cairo --with-java-home=/usr/lib/jvm/java-1.5.0-gcj-4.8-amd64/jre --enable-java-home --with-jvm-root-dir=/usr/lib/jvm/java-1.5.0-gcj-4.8-amd64 --with-jvm-jar-dir=/usr/lib/jvm-exports/java-1.5.0-gcj-4.8-amd64 --with-arch-directory=amd64 --with-ecj-jar=/usr/share/java/eclipse-ecj.jar --enable-objc-gc --enable-multiarch --disable-werror --with-arch-32=i686 --with-abi=m64 --with-multilib-list=m32,m64,mx32 --with-tune=generic --enable-checking=release --build=x86_64-linux-gnu --host=x86_64-linux-gnu --target=x86_64-linux-gnu
  Thread model: posix
  gcc version 4.8.1 (Ubuntu/Linaro 4.8.1-10ubuntu9)

To manage notifications about this bug go to:
https://bugs.launchpad.net/ubuntu/+source/gcc-4.8/+bug/1271743/+subscriptions