g++ pointer tracking question

[Steve Ellcey <sje at cup dot hp dot com>]

I am looking at a problem here in our HP-UX IPF GCC compiler and I think
it is due to a bug in the shared code that could affect all platforms.
I am hoping someone could help me understand this and see if I am on the
right track.

Here is part of a C++ program:

  struct A {
     A(int arg) : ix(arg) {}
     int ix;
     int foo(int arg) { return arg + ix; }
  };
  int func(int A::*p1)
  {
     A obj(2);
     return ((&obj)->*p1);
  }

Now, when I look at the RTL generated on HP-UX IPF in 64 bit mode with
-O1 (should be the similar to Linux IPF and probably others) I see:

(insn 4 2 5 (set (reg/v/f:DI 341)
        (reg:DI 112 in0)) -1 (nil)
    (nil))

Now, I think the '/f' on register 341 means that frame_related is set
which is what is used to say that REG_POINTER is true.  I.e.  we are
claiming that 341 contains a pointer to memory.  In fact in0 and
register 341 actually just contain the offset of ix within the structure
A.  I think passing an offset (and not an address) as the argument is
the right thing to do but then we shouldn't be setting REG_POINTER to
TRUE, should we?  Can somone tell me if I passing an offset is in fact
right?  If so should REG_POINTER for reg 341 be set to TRUE?

I have no idea how to fix this but I would at least like to be sure
I understand the problem.  I can submit a GNAT if that would help and
I can continue to look into what to do but I am at a loss for how to
proceed right now.

Steve Ellcey
sje@cup.hp.com