tree-ssa-sccvn.c (visit_use): Also constant-fold calls.

2014-05-16  Richard Biener  <rguenther@suse.de>

	* tree-ssa-sccvn.c (visit_use): Also constant-fold calls.

	* gcc.dg/tree-ssa/ssa-fre-41.c: New testcase.

From-SVN: r210491

4 files changed, 77 insertions, 15 deletions

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 5a29ded..3df0bb4 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,7 @@
+2014-05-16  Richard Biener  <rguenther@suse.de>
+
+	* tree-ssa-sccvn.c (visit_use): Also constant-fold calls.
+
 2014-05-15  Peter Bergner  <bergner@vnet.ibm.com>
 
 	PR target/61193
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 96b6303..8c52f8c 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,7 @@
+2014-05-16  Richard Biener  <rguenther@suse.de>
+
+	* gcc.dg/tree-ssa/ssa-fre-41.c: New testcase.
+
 2014-05-15  Martin Jambor  <mjambor@suse.cz>
 
 	PR ipa/61085
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/ssa-fre-41.c b/gcc/testsuite/gcc.dg/tree-ssa/ssa-fre-41.c
new file mode 100644
index 0000000..82ca746
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/ssa-fre-41.c
@@ -0,0 +1,12 @@
+/* { dg-do compile } */
+/* { dg-options "-O -fdump-tree-fre1" } */
+
+int x;
+int foo (void)
+{
+  x = 1;
+  return __builtin_ffs (x);
+}
+
+/* { dg-final { scan-tree-dump-not "ffs" "fre1" } } */
+/* { dg-final { cleanup-tree-dump "fre1" } } */
diff --git a/gcc/tree-ssa-sccvn.c b/gcc/tree-ssa-sccvn.c
index 07b9bd2..93a7e30 100644
--- a/gcc/tree-ssa-sccvn.c
+++ b/gcc/tree-ssa-sccvn.c
@@ -3566,28 +3566,70 @@ visit_use (tree use)
       else if (is_gimple_call (stmt))
 	{
 	  tree lhs = gimple_call_lhs (stmt);
-
-	  /* ???  We could try to simplify calls.  */
-
 	  if (lhs && TREE_CODE (lhs) == SSA_NAME)
 	    {
-	      if (stmt_has_constants (stmt))
-		VN_INFO (lhs)->has_constants = true;
-	      else
+	      /* Try constant folding based on our current lattice.  */
+	      tree simplified = gimple_fold_stmt_to_constant_1 (stmt,
+								vn_valueize);
+	      if (simplified)
+		{
+		  if (dump_file && (dump_flags & TDF_DETAILS))
+		    {
+		      fprintf (dump_file, "call ");
+		      print_gimple_expr (dump_file, stmt, 0, 0);
+		      fprintf (dump_file, " simplified to ");
+		      print_generic_expr (dump_file, simplified, 0);
+		      if (TREE_CODE (lhs) == SSA_NAME)
+			fprintf (dump_file, " has constants %d\n",
+				 expr_has_constants (simplified));
+		      else
+			fprintf (dump_file, "\n");
+		    }
+		}
+	      /* Setting value numbers to constants will occasionally
+		 screw up phi congruence because constants are not
+		 uniquely associated with a single ssa name that can be
+		 looked up.  */
+	      if (simplified
+		  && is_gimple_min_invariant (simplified))
 		{
-		  /* We reset expr and constantness here because we may
-		     have been value numbering optimistically, and
-		     iterating.  They may become non-constant in this case,
-		     even if they were optimistically constant.  */
-		  VN_INFO (lhs)->has_constants = false;
-		  VN_INFO (lhs)->expr = NULL_TREE;
+		  VN_INFO (lhs)->expr = simplified;
+		  VN_INFO (lhs)->has_constants = true;
+		  changed = set_ssa_val_to (lhs, simplified);
+		  if (gimple_vdef (stmt))
+		    changed |= set_ssa_val_to (gimple_vdef (stmt),
+					       gimple_vuse (stmt));
+		  goto done;
 		}
-
-	      if (SSA_NAME_OCCURS_IN_ABNORMAL_PHI (lhs))
+	      else if (simplified
+		       && TREE_CODE (simplified) == SSA_NAME)
 		{
-		  changed = defs_to_varying (stmt);
+		  changed = visit_copy (lhs, simplified);
+		  if (gimple_vdef (stmt))
+		    changed |= set_ssa_val_to (gimple_vdef (stmt),
+					       gimple_vuse (stmt));
 		  goto done;
 		}
+	      else
+		{
+		  if (stmt_has_constants (stmt))
+		    VN_INFO (lhs)->has_constants = true;
+		  else
+		    {
+		      /* We reset expr and constantness here because we may
+			 have been value numbering optimistically, and
+			 iterating.  They may become non-constant in this case,
+			 even if they were optimistically constant.  */
+		      VN_INFO (lhs)->has_constants = false;
+		      VN_INFO (lhs)->expr = NULL_TREE;
+		    }
+
+		  if (SSA_NAME_OCCURS_IN_ABNORMAL_PHI (lhs))
+		    {
+		      changed = defs_to_varying (stmt);
+		      goto done;
+		    }
+		}
 	    }
 
 	  if (!gimple_call_internal_p (stmt)