[Bug tree-optimization/103121] [12 Regression] Warnings in cp/optimize.c causing build failure

["amacleod at redhat dot com" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103121

--- Comment #14 from Andrew Macleod <amacleod at redhat dot com> ---
As near as I can tell, you are calling debug_ranger () to see what ranger could
produce. That routine creates a new ranger and populates it, dumps out the
results, kills the ranger  and returns.

When I put a breakpoint in the code:

2181      tree tlen = build_int_cst (size_type_node, len);
(gdb) c
Continuing.

Breakpoint 1, strlen_pass::maybe_warn_overflow (this=0x7fffffffcec0,
stmt=0x7fffe9f63910, call_lhs=true, len=0x7fffe9f4ed50, si=0x0, plus_one=false,
rawmem=false) at /gcc/master/gcc/gcc/tree-ssa-strlen.c:1998
1998      if (!len || warning_suppressed_p (stmt, OPT_Wstringop_overflow_))
(gdb) p print_gimple_stmt (stderr, stmt, 0 ,0)
*grp_name_25 = 0;
$8 = void
(gdb) enable 2
(gdb) c
Continuing.

Breakpoint 2, vr_values::range_of_expr (this=0x7fffffffcee0, r=...,
expr=0x7fffe9f5d0d8, stmt=0x7fffe9f5b240) at
/gcc/master/gcc/gcc/vr-values.c:182
182       if (!gimple_range_ssa_p (expr))
(gdb) p print_generic_expr (stderr, expr, 0)
_2$9 = void
(gdb) p print_gimple_stmt (stderr, stmt, 0, 0)
grp_name_25 = __builtin_alloca (_2);
$10 = void

So yes, you are asking for the range of _2 at that statement.... but note the
traceback shows you are invoking:
   Breakpoint 2, vr_values::range_of_expr
Which means you aren't using ranger... that callback is into vr_values... which
is the old EVRP engine.

Have you called enable_ranger() to turn it on for your pass?  You should be
seeing gimple-ranger::range_of_expr() in that traceback.
That also explains why when I range --param=ranger-debug=trace I wasn't seeing
any calls in your listing.

Looking deeper, the place where this is called from in get_size_range:

 if (!query)
    query = get_range_query (cfun);

  if (integral)
    {
      value_range vr;

      query->range_of_expr (vr, exp, stmt);


p get_range_query (cfun)
$11 = (range_query *) 0x40d9a80 <global_ranges>
So if you didn't have a range query, it would have picked up global ranges.. 
Looking down the call chain:

#0  vr_values::range_of_expr (this=0x7fffffffcee0, r=..., expr=0x7fffe9f5d0d8,
stmt=0x7fffe9f5b240) at /gcc/master/gcc/gcc/vr-values.c:182
#1  0x000000000163c58c in get_size_range (query=0x7fffffffcee0,
exp=0x7fffe9f5d0d8, stmt=0x7fffe9f5b240, range=0x7fffffffb840, flags=3) at
/gcc/master/gcc/gcc/pointer-query.cc:320
#2  0x000000000163d724 in gimple_call_alloc_size (stmt=0x7fffe9f5b240,
rng1=0x7fffffffbb20, qry=0x7fffffffcee0) at
/gcc/master/gcc/gcc/pointer-query.cc:506
#3  0x0000000001643501 in compute_objsize_r (ptr=0x7fffe9f5d870,
stmt=0x7fffe9f5b240, ostype=1, pref=0x7fffffffc7f0, snlim=...,
qry=0x7fffffffcfb8) at /gcc/master/gcc/gcc/pointer-query.cc:1970
#4  0x000000000164224c in handle_mem_ref (mref=0x7fffe9f6d230,
stmt=0x7fffe9f63910, ostype=1, pref=0x7fffffffc7f0, snlim=...,
qry=0x7fffffffcfb8) at /gcc/master/gcc/gcc/pointer-query.cc:1702
#5  0x0000000001642d63 in compute_objsize_r (ptr=0x7fffe9f6d230,
stmt=0x7fffe9f63910, ostype=1, pref=0x7fffffffc7f0, snlim=...,
qry=0x7fffffffcfb8) at /gcc/master/gcc/gcc/pointer-query.cc:1865
#6  0x00000000016441a9 in compute_objsize (ptr=0x7fffe9f6d230,
stmt=0x7fffe9f63910, ostype=1, pref=0x7fffffffc7f0, ptr_qry=0x7fffffffcfb8) at
/gcc/master/gcc/gcc/pointer-query.cc:2154
#7  0x0000000001a71634 in strlen_pass::maybe_warn_overflow
(this=0x7fffffffcec0, stmt=0x7fffe9f63910, call_lhs=true, len=0x7fffe9f4ed50,
si=0x0, plus_one=false, rawmem=false)
    at /gcc/master/gcc/gcc/tree-ssa-strlen.c:2038

I see you are passing this range_query down the call chain from the
maybe_warn_overflow.  I am not sure where you picked up a vr-values range
query...   but if you had simply called enable_ranger() at the start of the
pass, and let cfun->get_range_query() get the query object in get_size_range(),
I would expect you to see rangers results.  As it is, I don't know what you are
looking at, nor where it came from.