VN: Handle `(A CMP B) !=/== 0` for predicates [PR117414]

After the last patch, we also want to record `(A CMP B) != 0`
as `(A CMP B)` and `(A CMP B) == 0` as `(A CMP B)` with the
true/false edges swapped.

This shows up more due to the new handling of
`(A | B) ==/!= 0` in insert_predicates_for_cond
as now we can notice these comparisons which were not seen before.

This is enough to fix the original issue in `gcc.dg/tree-ssa/pr111456-1.c`
and make sure we don't regress it when enhancing ifcombine.

This adds that predicate and allows us to optimize f
in fre-predicated-3.c.

Changes since v1:
* v2:  Use vn_valueize.

Bootstrapped and tested on x86_64-linux-gnu.

	PR tree-optimization/117414

gcc/ChangeLog:

	* tree-ssa-sccvn.cc (insert_predicates_for_cond): Handle `(A CMP B) !=/== 0`.

gcc/testsuite/ChangeLog:

	* gcc.dg/tree-ssa/fre-predicated-3.c: New test.

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

2 files changed, 60 insertions, 0 deletions

diff --git a/gcc/testsuite/gcc.dg/tree-ssa/fre-predicated-3.c b/gcc/testsuite/gcc.dg/tree-ssa/fre-predicated-3.c
new file mode 100644
index 0000000..4a89372
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/fre-predicated-3.c
@@ -0,0 +1,46 @@
+/* { 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 f(int *aaa, int j, int t)
+{
+  int b = *aaa;
+  int c = b == 0;
+  int d = t != 1;
+  if (c | d)
+    return 0;
+
+  for(int i = 0; i < j; i++)
+  {
+    if (*aaa)
+      ;
+    else
+      foo();
+  }
+  return 0;
+}
+
+int f1(int *aaa, int j, int t)
+{
+  int b = *aaa;
+  if (b == 0)
+    return 0;
+  if (t != 1)
+    return 0;
+  for(int i = 0; i < j; i++)
+  {
+    if (*aaa)
+      ;
+    else
+      foo();
+  }
+  return 0;
+}
+
+/* { dg-final { scan-tree-dump-not "foo " "optimized" } } */
+/* { dg-final { scan-tree-dump "return 0;" "optimized" } } */
diff --git a/gcc/tree-ssa-sccvn.cc b/gcc/tree-ssa-sccvn.cc
index c6dddd0..67ed2cd 100644
--- a/gcc/tree-ssa-sccvn.cc
+++ b/gcc/tree-ssa-sccvn.cc
@@ -7948,6 +7948,20 @@ insert_predicates_for_cond (tree_code code, tree lhs, tree rhs,
       && (code == NE_EXPR || code == EQ_EXPR))
     {
       gimple *def_stmt = SSA_NAME_DEF_STMT (lhs);
+      /* (A CMP B) != 0 is the same as (A CMP B).
+	 (A CMP B) == 0 is just (A CMP B) with the edges swapped.  */
+      if (is_gimple_assign (def_stmt)
+	  && TREE_CODE_CLASS (gimple_assign_rhs_code (def_stmt)) == tcc_comparison)
+	  {
+	    tree_code nc = gimple_assign_rhs_code (def_stmt);
+	    tree nlhs = vn_valueize (gimple_assign_rhs1 (def_stmt));
+	    tree nrhs = vn_valueize (gimple_assign_rhs2 (def_stmt));
+	    edge nt = true_e;
+	    edge nf = false_e;
+	    if (code == EQ_EXPR)
+	      std::swap (nt, nf);
+	    insert_predicates_for_cond (nc, nlhs, nrhs, nt, nf);
+	  }
       /* (a | b) == 0 ->
 	    on true edge assert: a == 0 & b == 0. */
       /* (a | b) != 0 ->