[Bug target/22453] New: reload uses FLOAT_REGS class eagerly even if -mfpmath=sse

[bonzini at gcc dot gnu dot org]

The following code

extern double f(double, double);
void g (double x)
{
  double z, y;

  z = 0.0;
  y = 1.0 - x;

again:
  z = y - z;
  f(z, 1.0);
  if (z == 0.0)
    goto again;
}

has a fld1 instruction when compiled with "-mfpmath=sse -msse2 -msseregparm
-mtune=pentiumpro -O2".

This instruction is caused by a reload into a FLOAT_REGS register, and moving
the value to a SSE register needs secondary memory.

-- 
           Summary: reload uses FLOAT_REGS class eagerly even if -
                    mfpmath=sse
           Product: gcc
           Version: 4.1.0
            Status: UNCONFIRMED
          Keywords: missed-optimization, ra
          Severity: normal
          Priority: P2
         Component: target
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: bonzini at gcc dot gnu dot org
                CC: gcc-bugs at gcc dot gnu dot org,rguenth at gcc dot gnu
                    dot org
GCC target triplet: i686-pc-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=22453