VN: Handle (a | b) !=/== 0 for predicates [PR117414]

For `(a | b) == 0`, we can "assert" on the true edge that
both `a == 0` and `b == 0` but nothing on the false edge.
For `(a | b) != 0`, we can "assert" on the false edge that
both `a == 0` and `b == 0` but nothing on the true edge.
This adds that predicate and allows us to optimize f0, f1,
and f2 in fre-predicated-[12].c.

Changes since v1:
* v2: Use vn_valueize. Also canonicalize the comparison
      at the begining of insert_predicates_for_cond for
      constants to be on the rhs. Return early for
      non-ssa names on the lhs (after canonicalization).

Bootstrapped and tested on x86_64-linux-gnu.

	PR tree-optimization/117414

gcc/ChangeLog:

	* tree-ssa-sccvn.cc (insert_predicates_for_cond): Canonicalize the comparison.
	Don't insert anything if lhs is not a SSA_NAME. Handle `(a | b) !=/== 0`.

gcc/testsuite/ChangeLog:

	* gcc.dg/tree-ssa/fre-predicated-1.c: New test.
	* gcc.dg/tree-ssa/fre-predicated-2.c: New test.

Signed-off-by: Andrew Pinski <quic_apinski@quicinc.com>

gcc/testsuite/gcc.dg/tree-ssa/fre-predicated-1.c

@@ -0,0 +1,53 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-optimized" } */
+
+/* PR tree-optimization/117414 */
+
+/* Fre1 should figure out that `*aaa != 0`
+   For f0, f1, and f2. */
+
+
+void foo();
+int f0(int *aaa, int j, int t)
+{
+  int b = *aaa;
+  int c = b != 0;
+  int d = t !=  0;
+  if (d | c)
+    return 0;
+  for(int i = 0; i < j; i++)
+  {
+    if (*aaa) foo();
+  }
+  return 0;
+}
+
+int f1(int *aaa, int j, int t)
+{
+  int b = *aaa;
+  if (b != 0 || t != 0)
+    return 0;
+  for(int i = 0; i < j; i++)
+  {
+    if (*aaa) foo();
+  }
+  return 0;
+}
+
+
+int f2(int *aaa, int j, int t)
+{
+  int b = *aaa;
+  if (b != 0)
+    return 0;
+  if (t != 0)
+    return 0;
+  for(int i = 0; i < j; i++)
+  {
+    if (*aaa) foo();
+  }
+   return 0;
+}
+
+/* { dg-final { scan-tree-dump-not "foo " "optimized" } } */
+/* { dg-final { scan-tree-dump "return 0;" "optimized" } } */

gcc/testsuite/gcc.dg/tree-ssa/fre-predicated-2.c

@@ -0,0 +1,27 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-optimized" } */
+
+/* PR tree-optimization/117414 */
+
+/* Fre1 should figure out that `*aaa != 0`
+   For f0, f1, and f2. */
+
+
+void foo();
+int f0(int *aaa, int j, int t)
+{
+  int b = *aaa;
+  int d = b | t;
+  if (d == 0)
+    ;
+  else
+    return 0;
+  for(int i = 0; i < j; i++)
+  {
+    if (*aaa) foo();
+  }
+  return 0;
+}
+
+/* { dg-final { scan-tree-dump-not "foo " "optimized" } } */
+/* { dg-final { scan-tree-dump "return 0;" "optimized" } } */

gcc/tree-ssa-sccvn.cc

@@ -7901,6 +7901,21 @@ static void
 insert_predicates_for_cond (tree_code code, tree lhs, tree rhs,
 			    edge true_e, edge false_e)
 {
+  /* If both edges are null, then there is nothing to be done. */
+  if (!true_e && !false_e)
+    return;
+
+  /* Canonicalize the comparison so the rhs are constants.  */
+  if (CONSTANT_CLASS_P (lhs))
+    {
+      std::swap (lhs, rhs);
+      code = swap_tree_comparison (code);
+    }
+
+  /* If the lhs is not a ssa name, don't record anything. */
+  if (TREE_CODE (lhs) != SSA_NAME)
+    return;
+
   tree_code icode = invert_tree_comparison (code, HONOR_NANS (lhs));
   tree ops[2];
   ops[0] = lhs;
@@ -7929,6 +7944,27 @@ insert_predicates_for_cond (tree_code code, tree lhs, tree rhs,
       if (false_e)
 	insert_related_predicates_on_edge (icode, ops, false_e);
   }
+  if (integer_zerop (rhs)
+      && (code == NE_EXPR || code == EQ_EXPR))
+    {
+      gimple *def_stmt = SSA_NAME_DEF_STMT (lhs);
+      /* (a | b) == 0 ->
+	    on true edge assert: a == 0 & b == 0. */
+      /* (a | b) != 0 ->
+	    on false edge assert: a == 0 & b == 0. */
+      if (is_gimple_assign (def_stmt)
+	  && gimple_assign_rhs_code (def_stmt) == BIT_IOR_EXPR)
+	{
+	  edge e = code == EQ_EXPR ? true_e : false_e;
+	  tree nlhs;
+
+	  nlhs = vn_valueize (gimple_assign_rhs1 (def_stmt));
+	  insert_predicates_for_cond (EQ_EXPR, nlhs, rhs, e, nullptr);
+
+	  nlhs = vn_valueize (gimple_assign_rhs2 (def_stmt));
+	  insert_predicates_for_cond (EQ_EXPR, nlhs, rhs, e, nullptr);
+	}
+    }
 }
 
 /* Main stmt worker for RPO VN, process BB.  */