[PATCH, PR 52939] Gracefully deal with fold_ctor_reference returning NULL during devirtualization

[Martin Jambor]

Hi,

On Fri, Apr 13, 2012 at 04:13:13PM +0200, Richard Guenther wrote:
> On Fri, 13 Apr 2012, Martin Jambor wrote:
> 
> > Hi,
> > 
> > currently we ICE when attempting to devirtualize a call to a virtual
> > method introduced in a descendant but with a base which is an ancestor
> > which does not have it.  This is because fold_ctor_reference returns
> > constant zero when it cannot find the particular value in the provided
> > constructor which is something gimple_get_virt_method_for_binfo cannot
> > cope with.  The patch below avoids it by simply testing for that
> > value and bailing out.
> > 
> > Bootstrapped and tested on x86_64-linux, OK for trunk?
> 
> Ok.

I forgot to ask permission also to commit it to the 4.7 branch but I
suppose that I can do that too and will go ahead with the same patch
soon (after bootstrap and testing on the branch).

Thanks,

Martin


> 
> Thanks,
> Richard.
> 
> > Thanks,
> > 
> > Martin
> > 
> > 
> > 2012-04-12  Martin Jambor  <mjambor@suse.cz>
> > 
> > 	PR middle-end/52939
> > 	* gimple-fold.c (gimple_get_virt_method_for_binfo): Bail out if
> > 	fold_ctor_reference returns a zero constant.
> > 
> > 	* testsuite/g++.dg/ipa/pr52939.C: New test.
> > 
> > Index: src/gcc/gimple-fold.c
> > ===================================================================
> > --- src.orig/gcc/gimple-fold.c
> > +++ src/gcc/gimple-fold.c
> > @@ -3087,7 +3087,7 @@ gimple_get_virt_method_for_binfo (HOST_W
> >    offset += token * size;
> >    fn = fold_ctor_reference (TREE_TYPE (TREE_TYPE (v)), DECL_INITIAL (v),
> >  			    offset, size);
> > -  if (!fn)
> > +  if (!fn || integer_zerop (fn))
> >      return NULL_TREE;
> >    gcc_assert (TREE_CODE (fn) == ADDR_EXPR
> >  	      || TREE_CODE (fn) == FDESC_EXPR);
> > Index: src/gcc/testsuite/g++.dg/ipa/pr52939.C
> > ===================================================================
> > --- /dev/null
> > +++ src/gcc/testsuite/g++.dg/ipa/pr52939.C
> > @@ -0,0 +1,58 @@
> > +/* Verify that we do not ICE on invalid devirtualizations (which might
> > +   be OK at run-time because never executed).  */
> > +/* { dg-do run } */
> > +/* { dg-options "-O3 -fno-early-inlining -fno-inline"  } */
> > +
> > +extern "C" void abort (void);
> > +
> > +class A
> > +{
> > +public:
> > +  int data;
> > +  virtual int foo (int i);
> > +};
> > +
> > +class B : public A
> > +{
> > +public:
> > +  virtual int foo (int i);
> > +  virtual int bar (int i);
> > +};
> > +
> > +int A::foo (int i)
> > +{
> > +  return i + 1;
> > +}
> > +
> > +int B::foo (int i)
> > +{
> > +  return i + 2;
> > +}
> > +
> > +int B::bar (int i)
> > +{
> > +  return i + 3;
> > +}
> > +
> > +static int middleman (class A *obj, int i)
> > +{
> > +  class B *b = (class B *) obj;
> > +
> > +  if (i != 1)
> > +    return b->bar (i);
> > +  else
> > +    return i;
> > +}
> > +
> > +int __attribute__ ((noinline,noclone)) get_input(void)
> > +{
> > +  return 1;
> > +}
> > +
> > +int main (int argc, char *argv[])
> > +{
> > +  class A o;
> > +  if (middleman (&o, get_input ()) != 1)
> > +    abort ();
> > +  return 0;
> > +}
> > 
> > 
> 
> -- 
> Richard Guenther <rguenther@suse.de>
> SUSE / SUSE Labs
> SUSE LINUX Products GmbH - Nuernberg - AG Nuernberg - HRB 16746
> GF: Jeff Hawn, Jennifer Guild, Felix Imendörffer