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[PATCH] Fix PR68502


This restores a check I removed when adding strided group accesses
together with a better explanation and a FIXME comment how to recover
the missed optimizations (not appropriate at this stage).

I've added a realistic testcase from 179.art as well as an
artificial one that also fails on x86_64.

Bootstrap and regtest is running on x86_64-unknwon-linux-gnu.

Richard.

2015-11-24  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/68502
	* tree-vect-data-refs.c (vect_analyze_group_access_1): Restore
	check that the step is a multiple of the type size.

	* gcc.dg/vect/pr68502-1.c: New testcase.
	* gcc.dg/vect/pr68502-2.c: Likewise.

Index: gcc/tree-vect-data-refs.c
===================================================================
*** gcc/tree-vect-data-refs.c	(revision 230793)
--- gcc/tree-vect-data-refs.c	(working copy)
*************** vect_analyze_group_access_1 (struct data
*** 2176,2181 ****
--- 2198,2224 ----
    if (tree_fits_shwi_p (step))
      {
        dr_step = tree_to_shwi (step);
+       /* Check that STEP is a multiple of type size.  Otherwise there is
+          a non-element-sized gap at the end of the group which we
+ 	 cannot represent in GROUP_GAP or GROUP_SIZE.
+ 	 ???  As we can handle non-constant step fine here we should
+ 	 simply remove uses of GROUP_GAP between the last and first
+ 	 element and instead rely on DR_STEP.  GROUP_SIZE then would
+ 	 simply not include that gap.  */
+       if ((dr_step % type_size) != 0)
+ 	{
+ 	  if (dump_enabled_p ())
+ 	    {
+ 	      dump_printf_loc (MSG_NOTE, vect_location,
+ 	                       "Step ");
+ 	      dump_generic_expr (MSG_NOTE, TDF_SLIM, step);
+ 	      dump_printf (MSG_NOTE,
+ 			   " is not a multiple of the element size for ");
+ 	      dump_generic_expr (MSG_NOTE, TDF_SLIM, DR_REF (dr));
+ 	      dump_printf (MSG_NOTE, "\n");
+ 	    }
+ 	  return false;
+ 	}
        groupsize = absu_hwi (dr_step) / type_size;
      }
    else
Index: gcc/testsuite/gcc.dg/vect/pr68502-1.c
===================================================================
*** gcc/testsuite/gcc.dg/vect/pr68502-1.c	(revision 0)
--- gcc/testsuite/gcc.dg/vect/pr68502-1.c	(working copy)
***************
*** 0 ****
--- 1,48 ----
+ #include <stdlib.h>
+ #include "tree-vect.h"
+ 
+ typedef struct {
+     double *I;
+     double W;
+     double X;
+     double V;
+     double U;
+     double P;
+     double Q;
+     double R;
+ } f1_neuron;
+ 
+ f1_neuron *f1_layer;
+ 
+ int numf1s = 1000;
+ 
+ void __attribute__((noinline,noclone))
+ reset_nodes() 
+ {
+   int i;
+ 
+   for (i=0;i<numf1s;i++)
+     {
+       f1_layer[i].W = 0.0;
+       f1_layer[i].X = 0.0;
+       f1_layer[i].V = 0.0;
+       f1_layer[i].U = 0.0;
+       f1_layer[i].P = 0.0;
+       f1_layer[i].Q = 0.0;
+       f1_layer[i].R = 0.0;
+     }
+ }
+ 
+ int main ()
+ {
+   int i;
+   check_vect ();
+   f1_layer = (f1_neuron *)malloc (numf1s * sizeof (f1_neuron));
+   for (i = 0; i < numf1s; i++)
+     f1_layer[i].I = (double *)-1;
+   reset_nodes ();
+   for (i = 0; i < numf1s; i++)
+     if (f1_layer[i].I != (double *)-1)
+       abort ();
+   return 0; 
+ }
Index: gcc/testsuite/gcc.dg/vect/pr68502-2.c
===================================================================
*** gcc/testsuite/gcc.dg/vect/pr68502-2.c	(revision 0)
--- gcc/testsuite/gcc.dg/vect/pr68502-2.c	(working copy)
***************
*** 0 ****
--- 1,48 ----
+ #include <stdlib.h>
+ #include "tree-vect.h"
+ 
+ typedef struct {
+     short I;
+     int W;
+     int X;
+     int V;
+     int U;
+     int P;
+     int Q;
+     int R;
+ } __attribute__((packed)) f1_neuron;
+ 
+ f1_neuron *f1_layer;
+ 
+ int numf1s = 1000;
+ 
+ void __attribute__((noinline,noclone))
+ reset_nodes() 
+ {
+   int i;
+ 
+   for (i=0;i<numf1s;i++)
+     {
+       f1_layer[i].W = 0;
+       f1_layer[i].X = 0;
+       f1_layer[i].V = 0;
+       f1_layer[i].U = 0;
+       f1_layer[i].P = 0;
+       f1_layer[i].Q = 0;
+       f1_layer[i].R = 0;
+     }
+ }
+ 
+ int main ()
+ {
+   int i;
+   check_vect ();
+   f1_layer = (f1_neuron *)malloc (numf1s * sizeof (f1_neuron));
+   for (i = 0; i < numf1s; i++)
+     f1_layer[i].I = -1;
+   reset_nodes ();
+   for (i = 0; i < numf1s; i++)
+     if (f1_layer[i].I != -1)
+       abort ();
+   return 0; 
+ }


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