[PATCH] gimple-fold: Don't replace `{true/false} != false` with `true/false` inside GIMPLE_COND

[Andrew Pinski]

This is like the patch where we don't want to replace `bool_name != 0`
with `bool_name` but for instead for INTEGER_CST. The only thing
difference is there are a few different forms for always true/always
false; only handle it if it was in the canonical form. A few new helpers are
added for the canonical form detection.

This also replaces the previous version of the patch which did an early
exit from fold_stmt_1 instead so we can change the non-canonical form
into a canonical in the end.

gcc/ChangeLog:

        * gimple.h (gimple_cond_true_canonical_p): New function.
        (gimple_cond_false_canonical_p): New function.
        * gimple-fold.cc (replace_stmt_with_simplification): Return
        false if replacing the operands of GIMPLE_COND with an INTEGER_CST
        and already in canonical form.

Signed-off-by: Andrew Pinski <quic_apin...@quicinc.com>
---
 gcc/gimple-fold.cc | 15 +++++++++++++--
 gcc/gimple.h       | 30 ++++++++++++++++++++++++++++++
 2 files changed, 43 insertions(+), 2 deletions(-)

diff --git a/gcc/gimple-fold.cc b/gcc/gimple-fold.cc
index f801e8b6d41..e63fd6f2f2f 100644
--- a/gcc/gimple-fold.cc
+++ b/gcc/gimple-fold.cc
@@ -6258,10 +6258,21 @@ replace_stmt_with_simplification (gimple_stmt_iterator 
*gsi,
        }
       else if (code == INTEGER_CST)
        {
+         /* Make into the canonical form `1 != 0` and `0 != 0`.
+            If already in the canonical form return false
+            saying nothing has been done.  */
          if (integer_zerop (ops[0]))
-           gimple_cond_make_false (cond_stmt);
+           {
+             if (gimple_cond_false_canonical_p (cond_stmt))
+               return false;
+             gimple_cond_make_false (cond_stmt);
+           }
          else
-           gimple_cond_make_true (cond_stmt);
+           {
+             if (gimple_cond_true_canonical_p (cond_stmt))
+               return false;
+             gimple_cond_make_true (cond_stmt);
+           }
        }
       else if (!inplace)
        {
diff --git a/gcc/gimple.h b/gcc/gimple.h
index 032365f3da2..977ff1c923c 100644
--- a/gcc/gimple.h
+++ b/gcc/gimple.h
@@ -3875,6 +3875,21 @@ gimple_cond_true_p (const gcond *gs)
   return false;
 }
 
+/* Check if conditional statement GS is in the caonical form of 'if (1 != 0)'. 
*/
+
+inline bool
+gimple_cond_true_canonical_p (const gcond *gs)
+{
+  tree lhs = gimple_cond_lhs (gs);
+  tree rhs = gimple_cond_rhs (gs);
+  tree_code code = gimple_cond_code (gs);
+  if (code == NE_EXPR
+      && lhs == boolean_true_node
+      && rhs == boolean_false_node)
+    return true;
+  return false;
+}
+
 /* Check if conditional statement GS is of the form 'if (1 != 1)',
    'if (0 != 0)', 'if (1 == 0)' or 'if (0 == 1)' */
 
@@ -3900,6 +3915,21 @@ gimple_cond_false_p (const gcond *gs)
   return false;
 }
 
+/* Check if conditional statement GS is in the caonical form of 'if (0 != 0)'. 
*/
+
+inline bool
+gimple_cond_false_canonical_p (const gcond *gs)
+{
+  tree lhs = gimple_cond_lhs (gs);
+  tree rhs = gimple_cond_rhs (gs);
+  tree_code code = gimple_cond_code (gs);
+  if (code == NE_EXPR
+      && lhs == boolean_false_node
+      && rhs == boolean_false_node)
+    return true;
+  return false;
+}
+
 /* Set the code, LHS and RHS of GIMPLE_COND STMT from CODE, LHS and RHS.  */
 
 inline void
-- 
2.43.0