[Bug rtl-optimization/48823] New: gcc-4.6.0 floating-point optimization regression on ia64-Linux

[mariah.lenox at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48823

           Summary: gcc-4.6.0 floating-point optimization regression on
                    ia64-Linux
           Product: gcc
           Version: 4.6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: rtl-optimization
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: mariah.lenox@gmail.com


/* gcc-4.6.0 floating-point optimization regression on ia64-Linux

% gcc -O1 -o foo foo.c
% foo
g3  = 35f2349dc34f3df6
i[1]= 3ca1a62633145c07
i[2]= b92f1976b7ed8fbc
j[1]= 3ca4d57ee2b1013a
j[2]= b92618713a31d3e2
val = 35bfd0f99254c580
8.53973422267356774285
402114580b45d475
% 
%
% gcc -O2 -o foo foo.c
% foo
g3  = 35f2349dc34f3df6
i[1]= 3ca1a62633145c07
i[2]= b92f1976b7ed8fbc
j[1]= 3ca4d57ee2b1013a
j[2]= b92618713a31d3e2
val = 35bfd0f99254c590
8.53973422267356596649
402114580b45d474
**ERROR** QD_check failed at x[0]
%
%
% gcc-4.5.1 -O2 -o foo foo.c
% foo
g3  = 35f2349dc34f3df6
i[1]= 3ca1a62633145c07
i[2]= b92f1976b7ed8fbc
j[1]= 3ca4d57ee2b1013a
j[2]= b92618713a31d3e2
val = 35bfd0f99254c590
8.53973422267356774285
402114580b45d475
%

# note that this code compiles and runs successfully 
# with gcc-4.5.1 -03


% gcc -v
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/local/gcc-4.6.0/ia64-Linux-gmp-5.0.1/libexec/gcc/ia64-unknown-linux-gnu/4.6.0/lto-wrapper
Target: ia64-unknown-linux-gnu
Configured with: /usr/local/gcc-4.6.0/src/gcc-4.6.0/configure
--enable-languages=c,c++,fortran --with-gnu-as
--with-as=/usr/local/binutils-2.21/ia64-Linux-rhel-gcc-4.5.1/bin/as
--with-gnu-ld
--with-ld=/usr/local/binutils-2.21/ia64-Linux-rhel-gcc-4.5.1/bin/ld
--with-gmp=/usr/local/gmp-5.0.1/ia64-Linux-rhel-gcc-4.5.0
--with-mpfr=/usr/local/mpfr-3.0.1/ia64-Linux-rhel-gmp-5.0.1-gcc-4.6.0
--with-mpc=/usr/local/mpc-0.9/ia64-Linux-rhel-gmp-5.0.1-mpfr-3.0.1-gcc-4.6.0
--prefix=/usr/local/gcc-4.6.0/ia64-Linux-gmp-5.0.1
Thread model: posix
gcc version 4.6.0 (GCC) 
%

*/

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <fpu_control.h>

double QD_e[4]={2.718281828459045091e+00,1.445646891729250158e-16,
                -2.127717108038176765e-33,1.515630159841218954e-49};
double QD_pi[4]=
{3.141592653589793116e+00,1.224646799147353207e-16,
 -2.994769809718339666e-33,1.112454220863365282e-49};

#define QD_qsum(a,b,s,e) {double z1; s=a+b; z1=s-a; e=b-z1;}
#define QD_sum(a,b,s,e)\
 {double bb,z1,z2; s=a+b; bb=s-a; z1=s-bb; z2=a-z1; z1=b-bb; e=z1+z2;}
#define QD_split(a,hi,lo)\
{double xt=134217729.0*a,z1; z1=xt-a; hi=xt-z1; lo=a-hi;}
#define QD_prod(a,b,p,e)\
{double ah,al,bh,bl,z1,z2,z3,z4; p=a*b; QD_split(a,ah,al); QD_split(b,bh,bl);\
 z1=ah*bh; z2=z1-p; z1=ah*bl; z3=al*bh; z4=z1+z3; z1=z2+z4; z3=al*bl; e=z1+z3;}


double QD_mul(double *i,double *j,double *o)
{
  double a0,a1,b1,b2,c1,c2,d2,d3,e2,e3,f2,f3;
  double g3,h1,h2,h3,k2,k3,l2,l3,m2,m3,n2,n3,p2,p3;
  double t1,t2,t3;
  double a2, a3,o0;
  double val;

  QD_prod(i[0],j[0],a0,a1); 
  QD_prod(i[0],j[1],b1,b2);
  QD_prod(i[1],j[0],c1,c2); 
  QD_prod(i[0],j[2],d2,d3);
  QD_prod(i[2],j[0],e2,e3); 
  QD_prod(i[1],j[1],f2,f3);
  g3=i[0]*j[3]+i[3]*j[0]; 
  QD_sum(a1,b1,t1,t2); 
  QD_sum(c1,t1,h1,t3); 
  QD_sum(t2,t3,h2,h3);
  QD_sum(b2,c2,k2,k3); 
  QD_sum(d2,e2,l2,l3); 
  QD_sum(f2,h2,m2,m3);
printf("g3  = %lx\n", g3); 
printf("i[1]= %lx\n", i[1]); 
printf("i[2]= %lx\n", i[2]); 
printf("j[1]= %lx\n", j[1]); 
printf("j[2]= %lx\n", j[2]); 
  g3+=(i[1]*j[2]+i[2]*j[1]); 
val = g3;  /* printing g3 here makes the bug disappear, so use return */
  QD_sum(k2,l2,n2,n3); 
  QD_sum(m2,n2,p2,p3);
  g3+=d3+e3+f3+h3+k3+l3+m3+n3+p3; 
  QD_qsum(p2,g3,a2,a3); 
  QD_qsum(h1,a2,b1,b2); 
  QD_qsum(a0,b1,o0,c1);
  o[0]=o0; 
  QD_qsum(c1,b2,o[1],d2); 
  QD_qsum(d2,a3,o[2],o[3]);
  return val;
}

void errorit(S) char *S; {printf("**ERROR** %s\n",S); exit(-1);}

int main()
{
  double x[4]; 
  double val;
  /* This fpu_control code should set the control
   word of the floating point processor to round to an 
   IEEE-754 double (53-bit mantissa, 64-bits in total), rather
   than the default extended precision

   However the bug also occurs if this fpu_control code is
   removed or commented out.
  */
  fpu_control_t fpu_control=0x027f; _FPU_SETCW(fpu_control);

  val = QD_mul(QD_pi,QD_e,x);
printf("val = %lx\n", val);
printf("%1.20f\n", x[0]);
printf("%lx\n", x[0]);
  if (x[0]!=8.53973422267356774285) errorit("QD_check failed at x[0]");
  if (x[1]!=-6.7738152905024242803e-16) errorit("QD_check failed at x[1]");
  if (x[2]!=1.6082340642907151632e-32) errorit("QD_check failed at x[2]");
  return 0;
}