[Bug tree-optimization/65077] [4.9/5 Regression] memcpy generates incorrect code with floating point numbers and -O1

[anders.blomdell at control dot lth.se]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65077

--- Comment #8 from anders.blomdell at control dot lth.se ---
(In reply to Richard Biener from comment #6)
> (In reply to anders.blomdell from comment #5)
> > No, but my users insists on using Matlab/Simulink, and the testcase is a
> > heavily downsized version of what is done in their S-functions.
> 
> I mean - seriously storing a pointer as FP values of the upper/lower word
> of the pointer?  So I suppose this is what Matlab/Simulink generate
> internally
> and what gets compiled - thus this is machine generated?
Nope, part of C-code that users should include in their S-functions.
Code used to work with gcc-4.8.3. This will become a major problem :-(

> 
> A workaround is to use -fno-tree-pta btw (for 64bit pointers the out-of-bound
> write still occurs, but that may be due to your simplification?).
The out of bound write is because I'm a klutz, the bug occurs with this as well

S theS;

double *getP(void *p) {
  union u {
    void *p;
    int i[2];
  } u;
  u.p = &theS;
  P[0] = u.i[0];
  P[1] = u.i[1];
  return P;
}