Comment 2 for bug 791327

This looks like a compiler bug.

bin/bash ../../../../libtool --tag=CXX --mode=compile g++ -DHAVE_CONFIG_H -I. -I../../../../src/include -I/usr/lib/wx/include/gtk2-unicode-release-2.8 -I/usr/include/wx-2.8 -D_FILE_OFFSET_BITS=64 -D_LARGE_FILES -D__WXGTK__ -pthread -I../../../../src/include -I../../../../src/sdk/wxscintilla/include -Ulinux -Uunix -O2 -ffast-math -DCB_AUTOCONF -g -O2 -DCB_PRECOMP -Winvalid-pch -fPIC -DPIC -fexceptions -c -o byocbtris.lo byocbtris.cpp
libtool: compile: g++ -DHAVE_CONFIG_H -I. -I../../../../src/include -I/usr/lib/wx/include/gtk2-unicode-release-2.8 -I/usr/include/wx-2.8 -D_FILE_OFFSET_BITS=64 -D_LARGE_FILES -D__WXGTK__ -pthread -I../../../../src/include -I../../../../src/sdk/wxscintilla/include -Ulinux -Uunix -O2 -ffast-math -DCB_AUTOCONF -g -O2 -DCB_PRECOMP -Winvalid-pch -fPIC -DPIC -fexceptions -c byocbtris.cpp -fPIC -DPIC -o .libs/byocbtris.o
/tmp/ccQ2nsvc.s: Assembler messages:
/tmp/ccQ2nsvc.s:5100: Error: r13 not allowed here -- `rsb ip,sp,ip,lsl#2'

Reduced testcase :
g++ -c -O2 -march=armv7-a tst.cpp

$> cat tst.cpp

#include <string.h>
typedef int ChunkConfig[16];

void AlignChunk(ChunkConfig& chunk)
{

    int rowsShift = 0;
    while ( rowsShift<4 )
    {
        bool isEmpty = true;
        for ( int x=0; x<4; x++ )
            if ( chunk[rowsShift*4+x] != 0 )
            {
                isEmpty = false;
                break;
            }
        if ( !isEmpty ) break;
        rowsShift++;
    }

    int colsShift = 0;
    while ( colsShift<4 )
    {
        bool isEmpty = true;
        for ( int y=0; y<4; y++ )
            if ( chunk[colsShift+y*4] != 0 )
            {
                isEmpty = false;
                break;
            }
        if ( !isEmpty ) break;
        colsShift++;
    }

    if ( !colsShift && !rowsShift ) return;

    ChunkConfig newChunk;
    memset(newChunk,0,sizeof(newChunk));
    for ( int y=rowsShift,y2=0; y<4; y++,y2++ )
        for ( int x=colsShift,x2=0; x<4; x++,x2++ )
            newChunk[x2+y2*4] = chunk[x+y*4];
    memcpy(chunk,newChunk,sizeof(chunk));
}

Ramana