tree-ssa-sccvn.c (vn_reference_lookup_3): Valueize RHS when comparing against a…

tree-ssa-sccvn.c (vn_reference_lookup_3): Valueize RHS when comparing against a store with possibly the same value.

2019-07-05  Richard Biener  <rguenther@suse.de>

	* tree-ssa-sccvn.c (vn_reference_lookup_3): Valueize RHS
	when comparing against a store with possibly the same value.

	* gcc.dg/tree-ssa/ssa-fre-77.c: New testcase.

From-SVN: r273136

gcc/ChangeLog

 2019-07-05  Richard Biener  <rguenther@suse.de>
 
+	* tree-ssa-sccvn.c (vn_reference_lookup_3): Valueize RHS
+	when comparing against a store with possibly the same value.
+
+2019-07-05  Richard Biener  <rguenther@suse.de>
+
 	PR tree-optimization/91091
 	* tree-ssa-alias.h (get_continuation_for_phi): Add tbaa_p parameter.
 	(walk_non_aliased_vuses): Likewise.

gcc/testsuite/ChangeLog

 2019-07-05  Richard Biener  <rguenther@suse.de>
 
+	* gcc.dg/tree-ssa/ssa-fre-77.c: New testcase.
+
+2019-07-05  Richard Biener  <rguenther@suse.de>
+
 	PR tree-optimization/91091
 	* gcc.dg/tree-ssa/pr91091-2.c: New testcase.
 	* gcc.dg/tree-ssa/ssa-fre-70.c: Likewise.

gcc/testsuite/gcc.dg/tree-ssa/ssa-fre-77.c

+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-fre1" } */
+
+int foo (int *p, int *q)
+{
+  int x;
+  *p = 1;
+  x = *p;
+  *q = x;
+  return *p;
+}
+
+/* { dg-final { scan-tree-dump "return 1;" "fre1" } } */

gcc/tree-ssa-sccvn.c

@@ -2047,9 +2047,11 @@ vn_reference_lookup_3 (ao_ref *ref, tree vuse, void *data_,
 	  if (res && res != (void *)-1)
 	    {
 	      vn_reference_t vnresult = (vn_reference_t) res;
+	      tree rhs = gimple_assign_rhs1 (def_stmt);
+	      if (TREE_CODE (rhs) == SSA_NAME)
+		rhs = SSA_VAL (rhs);
 	      if (vnresult->result
-		  && operand_equal_p (vnresult->result,
-				      gimple_assign_rhs1 (def_stmt), 0))
+		  && operand_equal_p (vnresult->result, rhs, 0))
 		return res;
 	    }
 	}