Re: [PATCH] Fix PR optimization/6086

[Franz Sirl <Franz dot Sirl-kernel at lauterbach dot com>]

On Saturday 30 March 2002 00:05, Jakub Jelinek wrote:
> Hi!
>
> It looks like Jan deleted too much code from combine_simplify_rtx in
> 2001-05-17 patch. Specifically, old code used to
> return CLOBBER and not the original SUBREG in some cases (like
> mode dependent or volatile MEM).
> Ok to commit if testing succeeds?
> I've simplified the original testcase to:
>
> struct A
> {
>   A (int x, int y);
>   int a, b;
>   int foo () { return a; }
>   int bar () { return b; }
> };
>
> struct B
> {
>   virtual ~B ();
>   virtual A baz () const;
> };
>
> struct C
> {
>   A foo () const;
>   B *c;
> };
>
> A C::foo () const
> {
>   int x, y;
>   x = c->baz ().foo ();
>   y = c->baz ().bar ();
>   return A (x, y);
> }
>
> at -O+, where proper code generation can be checked e.g. in -da dumps,
> but without a real ppc I'm afraid I cannot easily cook up an
> executable testcase which will fail if compiled by gcc 3.1 without
> this patch and succeed with gcc 3.0 or gcc 3.1 with this patch.
> Franz, could you try to write something (IMHO this
> is a problem which deserves a testcase)?

Jakub,

Daniel Jacobowitz changed the testcase into an executable one and I verified 
that it fails without your patch and passes with your patch on 
powerpc-linux-gnu.

Franz.

#include <stdlib.h>

struct A
{
  A (int x, int y);
  int a, b;
  int foo () { return a; }
  int bar () { return b; }
};

struct B
{
  virtual ~B ();
  virtual A baz () const;
};

struct C
{
  A foo () const;
  B *c;
};

A C::foo () const
{
  int x, y;
  x = c->baz ().foo ();
  y = c->baz ().bar ();
  return A (x, y);
}

A B::baz () const
{
  return A (4, 8);
}

A::A (int x, int y)
{
  a = x;
  b = y;
}

B::~B ()
{
}

int
main ()
{
  C the_c;
  B the_b;
  the_c.c = &the_b;
  if (the_c.foo().a != 4)
    abort ();
  return 0;
}