On Wed, 10 Feb 2016, Bernd Schmidt wrote:
> On 02/10/2016 02:50 PM, Richard Biener wrote:
> > On Wed, 10 Feb 2016, Bernd Schmidt wrote:
> >
> > > On 02/10/2016 02:35 PM, Richard Biener wrote:
> > >
> > > > Index: gcc/ifcvt.c
> > > > ===================================================================
> > > > --- gcc/ifcvt.c (revision 233262)
> > > > +++ gcc/ifcvt.c (working copy)
> > > > @@ -1274,7 +1274,8 @@ noce_try_store_flag_constants (struct no
> > > > && CONST_INT_P (XEXP (a, 1))
> > > > && CONST_INT_P (XEXP (b, 1))
> > > > && rtx_equal_p (XEXP (a, 0), XEXP (b, 0))
> > > > - && noce_operand_ok (XEXP (a, 0))
> > > > + && (REG_P (XEXP (a, 0))
> > > > + || ! reg_mentioned_p (if_info->x, XEXP (a, 0)))
> > >
> > > I guess that would also work. Could maybe use a brief comment.
> >
> > Ok. I'm testing that. I wonder if we need to use reg_overlap_mentioned_p
> > here (hard-reg pairs?) or if reg_mentioned_p is safe.
>
> Let's go with reg_overlap_mentioned_p. I kind of forgot about that once I
> thought of possible issues with emitting a move :-(
Ok, the following is in testing now.
Ok?
Thanks,
Richard.
2016-02-10 Richard Biener <rguent...@suse.de>
PR rtl-optimization/69291
* ifcvt.c (noce_try_store_flag_constants): Do not allow
subexpressions affected by changing the result.
Index: gcc/ifcvt.c
===================================================================
--- gcc/ifcvt.c (revision 233262)
+++ gcc/ifcvt.c (working copy)
@@ -1274,7 +1274,10 @@ noce_try_store_flag_constants (struct no
&& CONST_INT_P (XEXP (a, 1))
&& CONST_INT_P (XEXP (b, 1))
&& rtx_equal_p (XEXP (a, 0), XEXP (b, 0))
- && noce_operand_ok (XEXP (a, 0))
+ /* Allow expressions that are not using the result or plain
+ registers where we handle overlap below. */
+ && (REG_P (XEXP (a, 0))
+ || ! reg_overlap_mentioned_p (if_info->x, XEXP (a, 0)))
&& if_info->branch_cost >= 2)
{
common = XEXP (a, 0);
