error: unable to find a register to spill in class 'POINTER_REGS'

Projects Programming
1

I've tried to compile the program below with the latest (1.6.6.) and
with the 1.5.7 environment, but both give an error (see below) when
i 'un-comment' the first Serial.println statement in the SimpleLinearRegression
function.

google searches indicated that this could be due to:

  1. non printable characters in the code (not the case here)
  2. compiler bug (could be? but then i've tried two different ones and both still give the issue)
  3. 'old' arduino software that was installed on the same pc and is messing things up (but i've deleted all previous arduino installations and related stuff)

what am i missing?

void SimpleLinearRegression(double *arr, int n, double slope){

  double x = (float(n)-1.0f) * float(n) / 2;
  double xx = 0.0f;
  double y = 0.0f;
  double xy = 0.0f;
  
  for ( int i = 0; i < n; i++) {
    xx += i * i;
    y  += arr[i];
    xy += i * arr[i];    
  }
  
  Serial.println(xx);      // when commenting this line, the sketch compiles
  Serial.println(y);
  Serial.println(xy);
  Serial.println(x);
  
  slope = (float(n) * xy - x * y) / (float(n) * xx - x * x);
  
}



void setup() {
  Serial.begin(9600);
  // put your setup code here, to run once:
  double g[4] = {0,2,4,6};
  int n = 4;
  double slope = 0.0f;

  Serial.println(slope);
  SimpleLinearRegression(g,n,slope);
  Serial.println(slope);
}

For reference: the error

sketch_nov27a.ino: In function 'void SimpleLinearRegression(double*, int, double)':
sketch_nov27a.ino:22:1: error: unable to find a register to spill in class 'POINTER_REGS'
sketch_nov27a.ino:22:1: error: this is the insn:
(insn 68 67 70 3 (set (reg:SF 71 [ D.3834 ])
(mem:SF (post_inc:HI (reg:HI 2 r2 [orig:74 ivtmp.12 ] [74])) [2 MEM[base: _34, offset: 0B]+0 S4 A8])) sketch_nov27a.ino:11 99 {*movsf}
(expr_list:REG_INC (reg:HI 2 r2 [orig:74 ivtmp.12 ] [74])
(nil)))
sketch_nov27a.ino:22: confused by earlier errors, bailing out

2

Interesting; it's only the Serial.println(xy); (and the lack of "void loop () {}" ) that causes problems.

It's an optimiser problem by the look of it.

3

Thanks. Also other text implemented there gives the same error.
Even with the loop() function i get the same issues.

Optimiser as in the optimiser in the compiler? Is there any way one
can code around that, or should i use another compiler (which?)

Cheers, fien

4

If you make x, xx, y and xy global?

(nasty, I know, but if it gets you out of a hole...)

5

will try the global options and report back (next week).

thanks for the input