Somewhat belatedly following Aldy's lead on finishing
the conversion to Ranger, the attached patch modifies
gimple-ssa-warn-access and other passes that use
the pointer_query machinery to provide Ranger with
the statement it's being called to determine ranges for.
The changes are almost completely mechanical, involving
passing a GIMPLE statement around (and a range_query
pointer) all the way into the bowels of the pointer_query
class to make them available when range info is being
determined.

There might be some overlap with Aldy's tree-ssa-strlen.c
changes to do the same there.  I'll deal with any conflicts
when it comes time to commit the work.

The changes trigger a couple of -Wstringop-overread instances
in libstdc++ tests.  The warnings look valid for the IL but
the code they're in is unreachable.  One of the tests already
suppresses -Wstringop-overflow so also suppressing
-Wstringop-overread doesn't seem out of line.

Tested on x86_64-linux.

Martin

PS The warning for the u8path-char8_t.cc test is this:

/ssd/test/build/gcc-test/x86_64-pc-linux-gnu/libstdc++-v3/include/bits/char_traits.h:355: 
warning: 'void* __builtin_memcpy(void*, const void*, long unsigned int)' 
reading between 16 and 4611686018427387903 bytes from a region of size 
10 [-Wstringop-overread]

The IL for it is below.  The loop iN BB 3 exits with __i_22 equal
to 10 so BBs 5, 6 and 7 are unreachable.  It's surprising to me
that the loop isn't optimized into something better (like a MEM
array assignment or memcpy).

   <bb 2> [local count: 1073741824]:
   MEM[(struct basic_string *)&s1] ={v} {CLOBBER};
   MEM[(struct _Alloc_hider *)&s1] ={v} {CLOBBER};
   MEM[(struct _Alloc_hider *)&s1]._M_p = &s1.D.30357._M_local_buf;

   <bb 3> [local count: 8687547547]:
   # __i_109 = PHI <__i_22(3), 0(2)>
   __i_22 = __i_109 + 1;
   _24 = MEM[(const char_type &)"filename2" + __i_22 * 1];
   if (_24 != 0)
     goto <bb 3>; [89.00%]
   else
     goto <bb 4>; [11.00%]

   <bb 4> [local count: 1073741824]:   <<< __i_22 == 10 here
   if (__i_22 > 15)
     goto <bb 5>; [33.00%]
   else
     goto <bb 8>; [67.00%]

   <bb 5> [local count: 354334802]:
   if (__i_22 > 4611686018427387903)
     goto <bb 6>; [0.04%]
   else
     goto <bb 7>; [99.96%]   >>> __i_22 in [16, 4611686018427387903]

   <bb 6> [local count: 141736]:
   std::__throw_length_error ("basic_string::_M_create");

   <bb 7> [local count: 354193066]:
   _85 = __i_109 + 2;
   _42 = operator new (_85);
   s1._M_dataplus._M_p = _42;
   s1.D.30357._M_allocated_capacity = __i_22;
   __builtin_memcpy (_42, "filename2", __i_22);   << -Wstringop-overread