checking of constant/writable arguments

[bgregoir]

No description provided.

[eponier]

This example is artificial, but do we want to accept such things?

fn f (reg ptr u64[1] r) -> reg u64 {
  reg u64 res;
  stack u64[1] s;

  r = s;
  r[0] = 1;
  res = r[0];

  return res;
}

export fn main () -> reg u64 {
  reg u64 res;
  stack u64[1] s;

  s[0] = 1;

  res = f(s);

  return res;
}

[vbgl]

This is not ready. The following program is now rejected:

fn zerofill(reg mut ptr u64[1] x) -> reg ptr u64[1] {
  x[0] = 0;
  return x;
}

export
fn main() -> reg u64 {
  stack u64[1] s;
  s = zerofill(s);
  reg u64 r;
  r = s[0];
  return r;
}

[eponier]

With @bgregoir, we are not sure what to do exactly, so let's postpone this a bit.

make check works now

[vbgl]

IMHO, it is OK to reject the artificial example above.

[bgregoir]

I did not see your last commit and I did the same patch.
Anyway I think we try to ensure something that is verified later by the compiler without having all the information.
We can do a variation of zerofill example:

inline fn zerofill(stack u64[1] x) -> stack u64[1] {
x[0] = 0;
return x;
}

export
fn main() -> reg u64 {
stack u64[1] s;
reg const ptr u64[1] t;
t = s;
s = zerofill(t);
reg u64 r;
r = s[0];
return r;
}

[vbgl]

Unless someone wants to implement a more precise check, I recommend to merge this PR as is.

[bgregoir]

Ok with this.

[bgregoir]

Apparently I can't merge it myself.

[eponier]

You have to accept it first (i.e. add a positive review).

[eponier]

@bgregoir accepts his own PR