Re: [patch tree-optimization]: Do bitwise operator optimizations for X op !X patterns

[Kai Tietz <ktietz70@googlemail.com>]

So updated patch (bootstrapped and tested for all standard languages
plus Ada and Obj-C++) on x86_64-pc-linux-gnu host.

Index: gcc-head/gcc/tree-ssa-forwprop.c
===================================================================
--- gcc-head.orig/gcc/tree-ssa-forwprop.c
+++ gcc-head/gcc/tree-ssa-forwprop.c
@@ -1602,6 +1602,156 @@ simplify_builtin_call (gimple_stmt_itera
   return false;
 }

+/* Checks if expression has type of one-bit precision, or is a known
+   truth-valued expression.  */
+static bool
+truth_valued_ssa_name (tree name)
+{
+  gimple def;
+  tree type = TREE_TYPE (name);
+
+  if (!INTEGRAL_TYPE_P (type))
+    return false;
+  /* Don't check here for BOOLEAN_TYPE as the precision isn't
+     necessarily one and so ~X is not equal to !X.  */
+  if (TYPE_PRECISION (type) == 1)
+    return true;
+  def = SSA_NAME_DEF_STMT (name);
+  if (is_gimple_assign (def))
+    return truth_value_p (gimple_assign_rhs_code (def));
+  return false;
+}
+
+/* Helper routine for simplify_bitwise_binary_1 function.
+   Return for the SSA name NAME the expression X if it mets condition
+   NAME = !X. Otherwise return NULL_TREE.
+   Detected patterns for NAME = !X are:
+     !X and X == 0 for X with integral type.
+     X ^ 1, X != 1,or ~X for X with integral type with precision of one.  */
+static tree
+lookup_logical_inverted_value (tree name)
+{
+  tree op1, op2;
+  enum tree_code code;
+  gimple def;
+
+  /* If name has none-intergal type, or isn't a SSA_NAME, then
+     return.  */
+  if (TREE_CODE (name) != SSA_NAME
+      || !INTEGRAL_TYPE_P (TREE_TYPE (name)))
+    return NULL_TREE;
+  def = SSA_NAME_DEF_STMT (name);
+  if (!is_gimple_assign (def))
+    return NULL_TREE;
+
+  code = gimple_assign_rhs_code (def);
+  op1 = gimple_assign_rhs1 (def);
+  op2 = NULL_TREE;
+
+  /* Get for EQ_EXPR or BIT_XOR_EXPR operation the second operand.
+     If CODE isn't an EQ_EXPR, BIT_XOR_EXPR, TRUTH_NOT_EXPR,
+     or BIT_NOT_EXPR, then return.  */
+  if (code == EQ_EXPR || code == NE_EXPR
+      || code == BIT_XOR_EXPR)
+    op2 = gimple_assign_rhs2 (def);
+
+  switch (code)
+    {
+    case TRUTH_NOT_EXPR:
+      return op1;
+    case BIT_NOT_EXPR:
+      if (truth_valued_ssa_name (name))
+	return op1;
+      break;
+    case EQ_EXPR:
+      /* Check if we have X == 0 and X has an integral type.  */
+      if (!INTEGRAL_TYPE_P (TREE_TYPE (op1)))
+	break;
+      if (integer_zerop (op2))
+	return op1;
+      break;
+    case NE_EXPR:
+      /* Check if we have X != 1 and X is a truth-valued.  */
+      if (!INTEGRAL_TYPE_P (TREE_TYPE (op1)))
+	break;
+      if (integer_onep (op2) && truth_valued_ssa_name (op1))
+	return op1;
+      break;
+    case BIT_XOR_EXPR:
+      /* Check if we have X ^ 1 and X is truth valued.  */
+      if (integer_onep (op2) && truth_valued_ssa_name (op1))
+	return op1;
+      break;
+    default:
+      break;
+    }
+
+  return NULL_TREE;
+}
+
+/* Try to optimize patterns X & !X -> zero, X | !X -> one, and
+   X ^ !X -> one, if type of X is valid for this.
+
+   See for list of detected logical-not patterns the
+   lookup_logical_inverted_value function.  */
+static tree
+simplify_bitwise_binary_1 (enum tree_code code, tree arg1,
+			   tree arg2)
+{
+  tree a1not, a2not;
+  tree op = NULL_TREE;
+
+  /* If CODE isn't a bitwise binary operation, return NULL_TREE.  */
+  if (code != BIT_AND_EXPR && code != BIT_IOR_EXPR
+      && code != BIT_XOR_EXPR)
+    return NULL_TREE;
+
+  /* First check if operands ARG1 and ARG2 are equal.  */
+  if (operand_equal_p (arg1, arg2, 0))
+    return NULL_TREE;
+  /* See if we have in arguments logical-not patterns.  */
+  a1not = lookup_logical_inverted_value (arg1);
+  a2not = lookup_logical_inverted_value (arg2);
+
+  /* If there are no logical-not in arguments,  return NULL_TREE. */
+  if (!a1not && !a2not)
+    return NULL_TREE;
+
+  /* If both arguments are logical-not patterns, then try to fold
+     them or return NULL_TREE.  */
+  if (a1not && a2not)
+    {
+      /* If logical-not operands of ARG1 and ARG2 are equal, then fold
+	 them..  */
+      if (operand_equal_p (a1not, a2not, 0))
+	{
+	  /* !X & !X -> !X, and !X | !X -> !X.  */
+	  if (code == BIT_AND_EXPR || code == BIT_IOR_EXPR)
+	    return arg1;
+	  /* !X ^ !X -> 0.  */
+	  return integer_zero_node;
+	}
+      return NULL_TREE;
+    }
+
+  if (a2not && operand_equal_p (arg1, a2not, 0))
+    op = arg1;
+  else if (a1not && operand_equal_p (arg2, a1not, 0))
+    op = arg2;
+  else
+    return NULL_TREE;
+
+  /* X & !X -> 0.  */
+  if (code == BIT_AND_EXPR)
+    return integer_zero_node;
+  /* X | !X -> 1 and X ^ !X -> 1, if X is truth-valued.  */
+  if (truth_valued_ssa_name (op))
+    return integer_one_node;
+
+  /* ??? Otherwise result is (X != 0 ? X : 1.  not handled.  */
+  return NULL_TREE;
+}
+
 /* Simplify bitwise binary operations.
    Return true if a transformation applied, otherwise return false.  */

@@ -1768,7 +1918,31 @@ simplify_bitwise_binary (gimple_stmt_ite
       update_stmt (stmt);
       return true;
     }
+  /* Try simple folding for X op !X, and X op X.  */
+  res = simplify_bitwise_binary_1 (code, arg1, arg2);
+  if (res != NULL_TREE && TREE_CODE (res) == INTEGER_CST)
+    {
+      res = fold_convert_loc (gimple_location (stmt),
+			      TREE_TYPE (arg1), res);
+      gimple_assign_set_rhs_from_tree (gsi, res);
+      update_stmt (gsi_stmt (*gsi));
+      return true;
+    }
+  else if (res)
+    {
+      if (!useless_type_conversion_p (TREE_TYPE (arg1), TREE_TYPE (res)))
+	{
+	  res = force_gimple_operand_gsi (gsi, res, true, NULL_TREE, true,
+					  GSI_SAME_STMT);

+	  gimple_assign_set_rhs_with_ops_1 (gsi, NOP_EXPR,
+					    res, NULL_TREE, NULL_TREE);
+	}
+      else
+	gimple_assign_set_rhs_from_tree (gsi, res);
+      update_stmt (gsi_stmt (*gsi));
+      return true;
+    }
   return false;
 }

Index: gcc-head/gcc/testsuite/gcc.dg/binop-notand1a.c
===================================================================
--- /dev/null
+++ gcc-head/gcc/testsuite/gcc.dg/binop-notand1a.c
@@ -0,0 +1,13 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-optimized" } */
+
+int
+foo (char a, unsigned short b)
+{
+  return (a & !a) | (b & !b);
+}
+
+/* As long as comparisons aren't boolified and casts from boolean-types
+   aren't preserved, the folding of  X & !X to zero fails.  */
+/* { dg-final { scan-tree-dump-times "return 0" 1 "optimized" { xfail
*-*-* } } } */
+/* { dg-final { cleanup-tree-dump "optimized" } } */
Index: gcc-head/gcc/testsuite/gcc.dg/binop-notand2a.c
===================================================================
--- /dev/null
+++ gcc-head/gcc/testsuite/gcc.dg/binop-notand2a.c
@@ -0,0 +1,11 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-optimized" } */
+
+int
+foo (int a)
+{
+  return (!a & 1) != (a == 0);
+}
+
+/* { dg-final { scan-tree-dump-times "return 0" 1 "optimized" } } */
+/* { dg-final { cleanup-tree-dump "optimized" } } */
Index: gcc-head/gcc/testsuite/gcc.dg/binop-notand3a.c
===================================================================
--- /dev/null
+++ gcc-head/gcc/testsuite/gcc.dg/binop-notand3a.c
@@ -0,0 +1,11 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-optimized" } */
+
+int
+foo (short a)
+{
+  return (!a & 1) != ((a == 0) & 1);
+}
+
+/* { dg-final { scan-tree-dump-times "return 0" 1 "optimized" } } */
+/* { dg-final { cleanup-tree-dump "optimized" } } */
Index: gcc-head/gcc/testsuite/gcc.dg/binop-notand4a.c
===================================================================
--- /dev/null
+++ gcc-head/gcc/testsuite/gcc.dg/binop-notand4a.c
@@ -0,0 +1,13 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-optimized" } */
+
+int
+foo (unsigned char a, _Bool b)
+{
+  return (!a & a) | (b & !b);
+}
+
+/* As long as comparisons aren't boolified and casts from boolean-types
+   aren't preserved, the folding of  X & !X to zero fails.  */
+/* { dg-final { scan-tree-dump-times "return 0" 1 "optimized" { xfail
*-*-* } } } */
+/* { dg-final { cleanup-tree-dump "optimized" } } */
Index: gcc-head/gcc/testsuite/gcc.dg/binop-notand5a.c
===================================================================
--- /dev/null
+++ gcc-head/gcc/testsuite/gcc.dg/binop-notand5a.c
@@ -0,0 +1,11 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-optimized" } */
+
+int
+foo (long a, unsigned long b)
+{
+  return (a & (a == 0)) | (b & !b);
+}
+
+/* { dg-final { scan-tree-dump-times "return 0" 1 "optimized" } } */
+/* { dg-final { cleanup-tree-dump "optimized" } } */
Index: gcc-head/gcc/testsuite/gcc.dg/binop-notand6a.c
===================================================================
--- /dev/null
+++ gcc-head/gcc/testsuite/gcc.dg/binop-notand6a.c
@@ -0,0 +1,11 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-optimized" } */
+
+int
+foo (unsigned long a, long b)
+{
+  return (a & !a) | (b & (b == 0));
+}
+
+/* { dg-final { scan-tree-dump-times "return 0" 1 "optimized" } } */
+/* { dg-final { cleanup-tree-dump "optimized" } } */
Index: gcc-head/gcc/testsuite/gcc.dg/binop-notor1.c
===================================================================
--- /dev/null
+++ gcc-head/gcc/testsuite/gcc.dg/binop-notor1.c
@@ -0,0 +1,11 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-optimized" } */
+
+int
+foo (_Bool a, _Bool b)
+{
+  return (a | !a) | (!b | b);
+}
+
+/* { dg-final { scan-tree-dump-times "return 1" 1 "optimized" } } */
+/* { dg-final { cleanup-tree-dump "optimized" } } */
Index: gcc-head/gcc/testsuite/gcc.dg/binop-notor2.c
===================================================================
--- /dev/null
+++ gcc-head/gcc/testsuite/gcc.dg/binop-notor2.c
@@ -0,0 +1,11 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-optimized" } */
+
+int
+foo (_Bool a, _Bool b)
+{
+  return (a | (a == 0)) | ((b ^ 1) | b);
+}
+
+/* { dg-final { scan-tree-dump-times "return 1" 1 "optimized" } } */
+/* { dg-final { cleanup-tree-dump "optimized" } } */
Index: gcc-head/gcc/testsuite/gcc.dg/binop-notxor1.c
===================================================================
--- /dev/null
+++ gcc-head/gcc/testsuite/gcc.dg/binop-notxor1.c
@@ -0,0 +1,11 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-optimized" } */
+
+int
+foo (_Bool a, _Bool b)
+{
+  return (a ^ !a) | (!b ^ b);
+}
+
+/* { dg-final { scan-tree-dump-times "return 1" 1 "optimized" } } */
+/* { dg-final { cleanup-tree-dump "optimized" } } */
Index: gcc-head/gcc/testsuite/gcc.dg/binop-notxor2.c
===================================================================
--- /dev/null
+++ gcc-head/gcc/testsuite/gcc.dg/binop-notxor2.c
@@ -0,0 +1,11 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-optimized" } */
+
+int
+foo (_Bool a, _Bool b)
+{
+  return (a ^ (a == 0)) | ((b == 0) ^ b);
+}
+
+/* { dg-final { scan-tree-dump-times "return 1" 1 "optimized" } } */
+/* { dg-final { cleanup-tree-dump "optimized" } } */