re PR tree-optimization/57361 (Remove self memory assignment)

2013-06-12  Marc Glisse  <marc.glisse@inria.fr>

	PR tree-optimization/57361
gcc/
	* tree-ssa-dse.c (dse_possible_dead_store_p): Handle self-assignment.

gcc/testsuite/
	* gcc.dg/tree-ssa/pr57361.c: New file.

From-SVN: r200034

gcc/ChangeLog

+2013-06-12  Marc Glisse  <marc.glisse@inria.fr>
+
+	PR tree-optimization/57361
+	* tree-ssa-dse.c (dse_possible_dead_store_p): Handle self-assignment.
+
 2013-06-12  Sofiane Naci  <sofiane.naci@arm.com>
 
 	* config/aarch64/aarch64-simd.md (aarch64_combine<mode>): convert to split.

gcc/testsuite/ChangeLog

+2013-06-12  Marc Glisse  <marc.glisse@inria.fr>
+
+	PR tree-optimization/57361
+	* gcc.dg/tree-ssa/pr57361.c: New file.
+
 2013-06-12  Ramana Radhakrishnan  <ramana.radhakrishnan@arm.com>
 
 	* gcc.target/arm/unaligned-memcpy-4.c (src, dst): Initialize

gcc/testsuite/gcc.dg/tree-ssa/pr57361.c

+/* { dg-do compile } */
+/* { dg-options "-O -fdump-tree-dse1-details" } */
+
+struct A { int x; double y; };
+void f (struct A *a) {
+  *a = *a;
+}
+
+/* { dg-final { scan-tree-dump "Deleted dead store" "dse1"} } */

gcc/tree-ssa-dse.c

@@ -84,6 +84,13 @@ dse_possible_dead_store_p (gimple stmt, gimple *use_stmt)
 
   *use_stmt = NULL;
 
+  /* Self-assignments are zombies.  */
+  if (operand_equal_p (gimple_assign_rhs1 (stmt), gimple_assign_lhs (stmt), 0))
+    {
+      *use_stmt = stmt;
+      return true;
+    }
+
   /* Find the first dominated statement that clobbers (part of) the
      memory stmt stores to with no intermediate statement that may use
      part of the memory stmt stores.  That is, find a store that may