[Bug c/57054] New: Compilation with -O3 passes, with -O2 fails (ARM/NEON)

["nizamov.shawkat at gmail dot com" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57054

             Bug #: 57054
           Summary: Compilation with -O3 passes, with -O2 fails (ARM/NEON)
    Classification: Unclassified
           Product: gcc
           Version: 4.7.3
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: nizamov.shawkat@gmail.com


While learning ARM/NEON I found what seems to be a bug in GCC/ARM. 

The compilation of the same function fails with:

==========================
gcc -c -fPIC -fwrapv -O2 -fno-strict-aliasing -I/usr/include/python2.7
-march=armv7-a -mfpu=neon -mtune=cortex-a8 -fomit-frame-pointer -save-temps
bug.c                                                                          
==========================

and succeeds when -O2 is changed to -O3. 



The error message is:
==========================
In file included from bug.c:1:0:
/usr/lib/gcc/arm-linux-gnueabihf/4.7/include/arm_neon.h: In function âstreamVâ:
/usr/lib/gcc/arm-linux-gnueabihf/4.7/include/arm_neon.h:4994:48: error:
argument must be a constant
/usr/lib/gcc/arm-linux-gnueabihf/4.7/include/arm_neon.h:4994: confused by
earlier errors, bailing out
==========================


It seems that problem is connected with these intrinsics: 

vget_lane_u8(vector, lane) 
vgetq_lane_u16(vector, lane)

when the "lane" is specified as a variable, and not as a constant. 


==========================
gcc -v
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/lib/gcc/arm-linux-gnueabihf/4.7/lto-wrapper
Target: arm-linux-gnueabihf
Configured with: ../src/configure -v --with-pkgversion='Ubuntu/Linaro
4.7.3-1ubuntu1' --with-bugurl=file:///usr/share/doc/gcc-4.7/README.Bugs
--enable-languages=c,c++,go,fortran,objc,obj-c++ --prefix=/usr
--program-suffix=-4.7 --enable-shared --enable-linker-build-id
--libexecdir=/usr/lib --without-included-gettext --enable-threads=posix
--with-gxx-include-dir=/usr/include/c++/4.7 --libdir=/usr/lib --enable-nls
--with-sysroot=/ --enable-clocale=gnu --enable-libstdcxx-debug
--enable-libstdcxx-time=yes --enable-gnu-unique-object --disable-libitm
--enable-plugin --with-system-zlib --enable-objc-gc --with-cloog
--enable-cloog-backend=ppl --disable-cloog-version-check
--disable-ppl-version-check --enable-multiarch --enable-multilib
--disable-sjlj-exceptions --with-arch=armv7-a --with-fpu=vfpv3-d16
--with-float=hard --with-mode=thumb --disable-werror --enable-checking=release
--build=arm-linux-gnueabihf --host=arm-linux-gnueabihf
--target=arm-linux-gnueabihf
Thread model: posix
gcc version 4.7.3 (Ubuntu/Linaro 4.7.3-1ubuntu1) 
==========================

I am using the Beagleboard XM, with a Ubuntu Raring on it (kernel is custom
compiled).