gcc/testsuite/gcc.target/i386/387-3.c

/* Verify that 387 mathematical constants are recognized.  */
/* { dg-do compile } */
/* { dg-options "-O2 -mfpmath=387 -mfancy-math-387 -mtune=generic" } */
/* { dg-final { scan-assembler "fldpi" } } */
/* { dg-require-effective-target large_long_double } */

long double add_pi(long double x)
{
  return x + 3.1415926535897932385128089594061862044L;
}