Bug#766840: [armhf] Illegal assembler code generated with -O2

[Ole Streicher <olebole@debian.org>]

Package: gcc
Version: 4:4.9.1-5

Hi,

If trying to compile the attached file on armhf with

gcc -O2 -c reg.c

one gets 

/tmp/ccuv9e3N.s: Assembler messages:
/tmp/ccuv9e3N.s:106: Error: registers may not be the same -- `str r2,[r2],#4'

A workaround is to use either -fno-expensive-optimizations or -fno-schedule-insns.

gcc -O1 -fexpensive-optimizations -fschedule-insns -c reg.c

shows the same error.

The file is a shortened version from one of my packages (starlink-ast) which always compiled nicely on armhf, started to fail with gcc-4.9.1 [1]. With gcc-4.8.4, the compilation succeeded [2]:

gcc -DHAVE_CONFIG_H -I. -D_FORTIFY_SOURCE=2 -I/usr/include/star -DTHREAD_SAFE -g -O2 -fstack-protector-strong -Wformat -Werror=format-security -c region.c  -fPIC -DPIC -o .libs/libstarlink_ast_la-region.o
/tmp/ccJsRMs3.s: Assembler messages:
/tmp/ccJsRMs3.s:21403: Warning: base register written back, and overlaps one of transfer registers
/tmp/ccJsRMs3.s:28133: Error: registers may not be the same -- `str r3,[r3],#4'
/tmp/ccJsRMs3.s:28971: Warning: base register written back, and overlaps one of transfer registers

The warnings are on similar places as above, just with the floats replaced by doubles or long doubles.

Best regards

Ole

[1] https://buildd.debian.org/status/fetch.php?pkg=starlink-ast&arch=armhf&ver=8.0.2%2Bdfsg-1&stamp=1414223014
[2] https://buildd.debian.org/status/fetch.php?pkg=starlink-ast&arch=armhf&ver=8.0.0%2Bdfsg-2&stamp=1400237749

#include <stdlib.h>

void *astFree();
void *astMalloc();
int astOK = 1;

int MaskF( int inside, int ndim, 
	   const int lbnd[], const int ubnd[], 
	   float in[], float val) { 

   void *used_region;
   float *c, *d, *tmp_out;
   double *lbndgd, *ubndgd;
   int *lbndg, *ubndg, idim, ipix, nax, nin, nout, npix, npixg, result = 0; 
   if ( !astOK ) return result; 
   lbndg = astMalloc( sizeof( int )*(size_t) ndim ); 
   ubndg = astMalloc( sizeof( int )*(size_t) ndim ); 
   lbndgd = astMalloc( sizeof( double )*(size_t) ndim ); 
   ubndgd = astMalloc( sizeof( double )*(size_t) ndim ); 
   npix = 1; 
   npixg = 1; 
   for ( idim = 0; idim < ndim; idim++ ) { 
     npix *= ubnd[ idim ] - lbnd[ idim ]; 
     npixg *= ubndg[ idim ] - lbndg[ idim ]; 
   } 
   if( npixg <= 0 ){ 
     if( astGetNegated( used_region )) { 
       c = in; 
       for( ipix = 0; ipix < npix; ipix++ ) *(c++) = val; 
     } 
   } else if( npixg > 0) { 
     if(astGetNegated( used_region )) { 
       tmp_out = astMalloc( sizeof( float )*(size_t) npix ); 
       if( tmp_out ) { 
	 c = tmp_out; 
       } 
     } 
     result += astResampleF( used_region, lbnd, ubnd, 
			     ubnd, lbndg, ubndg); 
   }
   return result; 
}