Hi Andrew,

> >> Oh yeah, and in case you haven't figured it out on your own, you'll
> >> have to remove WIDEN_MULT_EXPR from the range-ops init table.   This
> >> non-standard mechanism only gets checked if there is no standard
> >> range-op table entry for the tree code :-P
> >>
> > Hmm it looks like it'll work, but it keeps segfaulting in:
> >
> > bool
> > range_op_handler::fold_range (vrange &r, tree type,
> > 			      const vrange &lh,
> > 			      const vrange &rh,
> > 			      relation_trio rel) const
> > {
> >    gcc_checking_assert (m_valid);
> >    if (m_int)
> >      return m_int->fold_range (as_a <irange> (r), type,
> > 			   as_a <irange> (lh),
> > 			   as_a <irange> (rh), rel);
> >
> > while trying to call fold_range.
> >
> > But m_int is set to the right instance. Probably something I'm
> > missing, I'll double check it all.
> >
> Hmm.  whats your class operator_widen_mult* look like? what are you
> inheriting from?   Send me your patch and I'll have a look if you want. this is
> somewhat  new territory :-)

I've attached the patch, and my testcase is:

int decMultiplyOp_zacc, decMultiplyOp_iacc;
int *decMultiplyOp_lp;
void decMultiplyOp() {
  decMultiplyOp_lp = &decMultiplyOp_zacc;
  for (; decMultiplyOp_lp < &decMultiplyOp_zacc + decMultiplyOp_iacc;
       decMultiplyOp_lp++)
    *decMultiplyOp_lp = 0;
}

And compiling with aarch64-none-elf-gcc -O2 zero.c -S -o - -Werror=stringop-overflow

Also to explain a bit on why we're only seeing this now:

The original sequence for most of the pipeline is based on a cast and multiplication

  # RANGE [irange] long unsigned int [0, 2147483647][18446744071562067968, +INF]
  _14 = (long unsigned intD.11) decMultiplyOp_iacc.2_13;
  # RANGE [irange] long unsigned int [0, 8589934588][18446744065119617024, 18446744073709551612] NONZERO 0xfffffffffffffffc
  _15 = _14 * 4;

But things like widening multiply are quite common, so some ISAs have it on scalars as well, not just vectors.
So there's a pass widening_mul that runs late for these targets.  This replaces the above with

  # RANGE [irange] long unsigned int [0, 8589934588][18446744065119617024, 18446744073709551612] NONZERO 0xfffffffffffffffc
  _15 = decMultiplyOp_iacc.2_13 w* 4;

And copies over the final range from the original expression.

After that there are passes like the warning passes that try to requery ranged to see if any optimization  has changed them.
Before my attempt to support *w this would just return VARYING and it would only use the old range.

Now however, without taking care to sign extend when appropriate the MIN range changes from a negative value to a large
positive one when we increase the precision.  So passes that re-query late get the wrong range.  That's why for instance in this case
we get an incorrect warning generated.

Thanks for the help!

Tamar

> 
> I cant imagine it being a linkage thing between the 2 files since the operator is
> defined in another file and the address taken in this one?
> that should work, but strange that cant make the call...
> 
> Andrew