[Bug target/24007] New: very weird register allocation, putting a fp in the ctr register

[pinskia at gcc dot gnu dot org]

Take the following example:
extern float a, b;

float BG_SplineLength ()
{
  float result27;
  float result;
  float lastPoint;
  float vec1;
  float vec0;
  float dist;
  float i;

  vec0 = a;
  vec1 = b;
  result = vec1 - vec0;
  i = 9.99999977648258209228515625e-3f;
  dist = 0.0;

do {
  result27 = vec1 - vec0;
  lastPoint = result;

  while (!(i != 0.0))
    {
      i = i + 9.99999977648258209228515625e-3f;
      lastPoint = result27;
    }

  vec0 = result27 - lastPoint;
  dist = dist + vec0;
  i = i + 9.99999977648258209228515625e-3f;
  
  if (! (i <= 1.0e+0))
    return dist;

  result = result27;
  } while (1);

}
---
On the mainline, we get:
L3:
        lis r11,ha16(LC4)
        fsubs f11,f9,f12
        la r11,lo16(LC4)(r11)
        lfs f0,0(r11)
        fcmpu cr7,f13,f0
        bne- cr7,L4
        fmr f12,f10
L5:
        fadds f13,f13,f12
        fcmpu cr7,f13,f0
        beq+ cr7,L5
        lfs f10,lo16(LC0)(r9)
        fmr f12,f11
        lfs f0,lo16(LC1)(r2)
        fadds f13,f13,f10
        stfs f11,-16(r1)
        fsubs f12,f11,f12
        lwz r0,-16(r1)
        fcmpu cr7,f13,f0
        mtctr r0
        fadds f1,f1,f12
        cror 30,28,30
        beq+ cr7,L3


Notice how we move through memory and use the ctr register.  That is just wrong.

If I change the type from float to double, it works correctly but only if I don't also use -m64.

-- 
           Summary: very weird register allocation, putting a fp in the ctr
                    register
           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: pinskia at gcc dot gnu dot org
                CC: gcc-bugs at gcc dot gnu dot org
GCC target triplet: powerpc-darwin


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24007