Fix bogus store_merging_x.c failures for avr.

Store merging isn't profitable for the avr. Add a new
effective target keyword "store_merge", and turn it on
only if non_strict_align *and* int32plus, as targets with
smallish word sizes are unlikely to profit from this optimization.

gcc/testsuite/ChangeLog

2016-11-03  Senthil Kumar Selvaraj  <senthil_kumar.selvaraj@atmel.com>

	* gcc.dg/store_merging_1.c: Require store_merge.
	* gcc.dg/store_merging_2.c: Likewise.
	* gcc.dg/store_merging_4.c: Likewise.
	* gcc.dg/store_merging_5.c: Likewise. 
	* gcc.dg/store_merging_6.c: Likewise.
	* gcc.dg/store_merging_7.c: Likewise.
	* gcc.dg/store_merging_8.c: Likewise.
	* lib/target-supports.exp (check_effective_target_store_merge): New.

From-SVN: r241953

gcc/testsuite/ChangeLog

+2016-11-08  Senthil Kumar Selvaraj  <senthil_kumar.selvaraj@atmel.com>
+
+	* gcc.dg/store_merging_1.c: Require store_merge.
+	* gcc.dg/store_merging_2.c: Likewise.
+	* gcc.dg/store_merging_4.c: Likewise.
+	* gcc.dg/store_merging_5.c: Likewise. 
+	* gcc.dg/store_merging_6.c: Likewise.
+	* gcc.dg/store_merging_7.c: Likewise.
+	* gcc.dg/store_merging_8.c: Likewise.
+	* lib/target-supports.exp (check_effective_target_store_merge): New.
+
 2016-11-07  David Edelsohn  <dje.gcc@gmail.com>
 
 	* gcc.target/powerpc/fold-vec-add-1.c: Add dg-options -maltivec.

gcc/testsuite/gcc.dg/store_merging_1.c

 /* { dg-do compile } */
-/* { dg-require-effective-target non_strict_align } */
+/* { dg-require-effective-target store_merge } */
 /* { dg-options "-O2 -fdump-tree-store-merging" } */
 
 struct bar {

gcc/testsuite/gcc.dg/store_merging_2.c

 /* { dg-do run } */
-/* { dg-require-effective-target non_strict_align } */
+/* { dg-require-effective-target store_merge } */
 /* { dg-options "-O2 -fdump-tree-store-merging" } */
 
 struct bar

gcc/testsuite/gcc.dg/store_merging_4.c

 /* { dg-do compile } */
-/* { dg-require-effective-target non_strict_align } */
+/* { dg-require-effective-target store_merge } */
 /* { dg-options "-O2 -fdump-tree-store-merging" } */
 
 /* Check that we can merge interleaving stores that are guaranteed

gcc/testsuite/gcc.dg/store_merging_5.c

 /* { dg-do compile } */
-/* { dg-require-effective-target non_strict_align } */
+/* { dg-require-effective-target store_merge } */
 /* { dg-options "-O2 -fdump-tree-store-merging" } */
 
 /* Make sure that non-aliasing non-constant interspersed stores do not

gcc/testsuite/gcc.dg/store_merging_6.c

 /* { dg-do run } */
-/* { dg-require-effective-target non_strict_align } */
+/* { dg-require-effective-target store_merge } */
 /* { dg-options "-O2 -fdump-tree-store-merging" } */
 
 /* Check that we can widen accesses to bitfields.  */

gcc/testsuite/gcc.dg/store_merging_7.c

 /* { dg-do compile } */
-/* { dg-require-effective-target non_strict_align } */
+/* { dg-require-effective-target store_merge } */
 /* { dg-options "-O2 -fdump-tree-store-merging" } */
 
 /* Check that we can merge consecutive array members through the pointer.

gcc/testsuite/gcc.dg/store_merging_8.c

 /* { dg-do compile } */
-/* { dg-require-effective-target non_strict_align } */
+/* { dg-require-effective-target store_merge } */
 /* { dg-options "-O2 -fdump-tree-store-merging" } */
 
 struct baz {

gcc/testsuite/lib/target-supports.exp

@@ -8107,3 +8107,17 @@ proc check_effective_target_divmod_simode { } {
 
     return [check_effective_target_divmod]
 }
+
+# Return 1 if store merging optimization is applicable for target.
+# Store merging is not profitable for targets like the avr which
+# can load/store only one byte at a time. Use int size as a proxy
+# for the number of bytes the target can write, and skip for targets
+# with a smallish (< 32) size.
+
+proc check_effective_target_store_merge { } {
+    if { [is-effective-target non_strict_align ] && [is-effective-target int32plus] } {
+	return 1
+    }
+
+    return 0
+}