[PATCH] Fix PR80275

[Richard Biener]

On Tue, 4 Apr 2017, Marc Glisse wrote:

> On Tue, 4 Apr 2017, Markus Trippelsdorf wrote:
> 
> > On 2017.04.03 at 11:16 +0200, Richard Biener wrote:
> > > 
> > > The following extends split_address_to_core_and_offset to handle
> > > POINTER_PLUS_EXPR to be able to simplify
> > > (unsigned long) &MEM[(void *)&D.15512 + 12B] - (unsigned long) ((const int
> > > *) &D.15512 + 4) which appears during niter analysis.
> > > 
> > > We seem to have various copies of similar code but refactoring didn't
> > > seem appropriate at this stage so I went for the minimal fix.
> > > 
> > > Bootstrap and regtest running on x86_64-unknown-linux-gnu.
> > > 
> > > Richard.
> > > 
> > > 2017-04-03  Richard Biener  <rguenther@suse.de>
> > > 
> > > 	PR tree-optimization/80275
> > > 	* fold-const.c (split_address_to_core_and_offset): Handle
> > > 	POINTER_PLUS_EXPR.
> > > 
> > > 	* g++.dg/opt/pr80275.C: New testcase.
> > > 
> > > Index: gcc/fold-const.c
> > > ===================================================================
> > > --- gcc/fold-const.c	(revision 246642)
> > > +++ gcc/fold-const.c	(working copy)
> > > @@ -14341,6 +14341,24 @@ split_address_to_core_and_offset (tree e
> > >  				  &volatilep);
> > >        core = build_fold_addr_expr_loc (loc, core);
> > >      }
> > > +  else if (TREE_CODE (exp) == POINTER_PLUS_EXPR)
> > > +    {
> > > +      core = TREE_OPERAND (exp, 0);
> > > +      STRIP_NOPS (core);
> > > +      *pbitpos = 0;
> > > +      *poffset = TREE_OPERAND (exp, 1);
> > > +      if (TREE_CODE (*poffset) == INTEGER_CST)
> > > +	{
> > > +	  offset_int tem = wi::sext (wi::to_offset (*poffset),
> > > +				     TYPE_PRECISION (TREE_TYPE (*poffset)));
> > > +	  tem <<= LOG2_BITS_PER_UNIT;
> > > +	  if (wi::fits_shwi_p (tem))
> > > +	    {
> > > +	      *pbitpos = tem.to_shwi ();
> > > +	      *poffset = NULL_TREE;
> > > +	    }
> > > +	}
> > > +    }
> > >    else
> > >      {
> > >        core = exp;
> > > Index: gcc/testsuite/g++.dg/opt/pr80275.C
> > > ===================================================================
> > > --- gcc/testsuite/g++.dg/opt/pr80275.C	(nonexistent)
> > > +++ gcc/testsuite/g++.dg/opt/pr80275.C	(working copy)
> > > @@ -0,0 +1,16 @@
> > > +// { dg-do compile { target c++14 } }
> > > +// { dg-options "-O2 -fdump-tree-optimized" }
> > > +
> > > +#include <algorithm>
> > > +
> > > +int g()
> > > +{
> > > +      return 1234;
> > > +}
> > > +
> > > +int f2()
> > > +{
> > > +      return std::min({1, g(), 4});
> > > +}
> > > +
> > > +// { dg-final { scan-tree-dump "return 1;" "optimized" } }
> > 
> > The testcase fails with -fpic, e.g.:
> > https://gcc.gnu.org/ml/gcc-regression/2017-04/msg00002.html
> > 
> > So perhaps:
> > 
> > diff --git a/gcc/testsuite/g++.dg/opt/pr80275.C
> > b/gcc/testsuite/g++.dg/opt/pr80275.C
> > index 7296a07fb2dd..7d625f2c7757 100644
> > --- a/gcc/testsuite/g++.dg/opt/pr80275.C
> > +++ b/gcc/testsuite/g++.dg/opt/pr80275.C
> > @@ -1,4 +1,4 @@
> > -// { dg-do compile { target c++14 } }
> > +// { dg-do compile { target c++14 && nonpic } }
> > // { dg-options "-O2 -fdump-tree-optimized" }
> > 
> > #include <algorithm>
> 
> Making g static should work even with PIC.

Tested on x86_64-unknown-linux-gnu, applied.

Richard.

2017-04-04  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/80275
	* g++.dg/opt/pr80275.C: Make g static.

Index: gcc/testsuite/g++.dg/opt/pr80275.C
===================================================================
--- gcc/testsuite/g++.dg/opt/pr80275.C	(revision 246670)
+++ gcc/testsuite/g++.dg/opt/pr80275.C	(working copy)
@@ -3,7 +3,7 @@
 
 #include <algorithm>
 
-int g()
+static int g()
 {
       return 1234;
 }