From: Andrew MacLeod <amacleod@redhat.com>
Date: Wed, 25 Oct 2023 13:46:50 +0000 (-0400)
Subject: Adjust operators equal and not_equal to check bitmasks against constants
X-Git-Tag: basepoints/gcc-15~5029
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=7ab79a40b546a1470abaf76bec74c63e9990fe47;p=thirdparty%2Fgcc.git

Adjust operators equal and not_equal to check bitmasks against constants

Check to see if a comparison to a constant can be determined to always
be not-equal based on the bitmask.

	PR tree-optimization/111766
	gcc/
	* range-op.cc (operator_equal::fold_range): Check constants
	against the bitmask.
	(operator_not_equal::fold_range): Ditto.
	* value-range.h (irange_bitmask::member_p): New.

	gcc/testsuite/
	* gcc.dg/pr111766.c: New.
---

diff --git a/gcc/range-op.cc b/gcc/range-op.cc
index 33b193be7d09..6137f2aeed37 100644
--- a/gcc/range-op.cc
+++ b/gcc/range-op.cc
@@ -931,8 +931,9 @@ operator_equal::fold_range (irange &r, tree type,
 
   // We can be sure the values are always equal or not if both ranges
   // consist of a single value, and then compare them.
-  if (wi::eq_p (op1.lower_bound (), op1.upper_bound ())
-      && wi::eq_p (op2.lower_bound (), op2.upper_bound ()))
+  bool op1_const = wi::eq_p (op1.lower_bound (), op1.upper_bound ());
+  bool op2_const = wi::eq_p (op2.lower_bound (), op2.upper_bound ());
+  if (op1_const && op2_const)
     {
       if (wi::eq_p (op1.lower_bound (), op2.upper_bound()))
 	r = range_true (type);
@@ -947,6 +948,11 @@ operator_equal::fold_range (irange &r, tree type,
       tmp.intersect (op2);
       if (tmp.undefined_p ())
 	r = range_false (type);
+      // Check if a constant cannot satisfy the bitmask requirements.
+      else if (op2_const && !op1.get_bitmask ().member_p (op2.lower_bound ()))
+	 r = range_false (type);
+      else if (op1_const && !op2.get_bitmask ().member_p (op1.lower_bound ()))
+	 r = range_false (type);
       else
 	r = range_true_and_false (type);
     }
@@ -1033,8 +1039,9 @@ operator_not_equal::fold_range (irange &r, tree type,
 
   // We can be sure the values are always equal or not if both ranges
   // consist of a single value, and then compare them.
-  if (wi::eq_p (op1.lower_bound (), op1.upper_bound ())
-      && wi::eq_p (op2.lower_bound (), op2.upper_bound ()))
+  bool op1_const = wi::eq_p (op1.lower_bound (), op1.upper_bound ());
+  bool op2_const = wi::eq_p (op2.lower_bound (), op2.upper_bound ());
+  if (op1_const && op2_const)
     {
       if (wi::ne_p (op1.lower_bound (), op2.upper_bound()))
 	r = range_true (type);
@@ -1049,6 +1056,11 @@ operator_not_equal::fold_range (irange &r, tree type,
       tmp.intersect (op2);
       if (tmp.undefined_p ())
 	r = range_true (type);
+      // Check if a constant cannot satisfy the bitmask requirements.
+      else if (op2_const && !op1.get_bitmask ().member_p (op2.lower_bound ()))
+	 r = range_true (type);
+      else if (op1_const && !op2.get_bitmask ().member_p (op1.lower_bound ()))
+	 r = range_true (type);
       else
 	r = range_true_and_false (type);
     }
diff --git a/gcc/testsuite/gcc.dg/pr111766.c b/gcc/testsuite/gcc.dg/pr111766.c
new file mode 100644
index 000000000000..c27a029c772c
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr111766.c
@@ -0,0 +1,13 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-evrp" } */
+
+int
+foo3n(int c, int bb)
+{
+  if ((bb & ~3)!=0) __builtin_unreachable(); // bb = [0,3]
+  if ((bb & 1)==0) __builtin_unreachable(); // bb&1 == 0 // [0],[3]
+  if(bb == 2) __builtin_trap();
+  return bb;
+}
+
+/* { dg-final { scan-tree-dump-not "trap" "evrp" } } */
diff --git a/gcc/value-range.h b/gcc/value-range.h
index 84f65ffb5910..330e6f70c6b6 100644
--- a/gcc/value-range.h
+++ b/gcc/value-range.h
@@ -139,6 +139,7 @@ public:
   void verify_mask () const;
   void dump (FILE *) const;
 
+  bool member_p (const wide_int &val) const;
   void adjust_range (irange &r) const;
 
   // Convenience functions for nonzero bitmask compatibility.
@@ -202,6 +203,19 @@ irange_bitmask::set_nonzero_bits (const wide_int &bits)
     verify_mask ();
 }
 
+// Return TRUE if val could be a valid value with this bitmask.
+
+inline bool
+irange_bitmask::member_p (const wide_int &val) const
+{
+  if (unknown_p ())
+    return true;
+  wide_int res = m_mask & val;
+  if (m_value != 0)
+    res |= ~m_mask & m_value;
+  return res == val;
+}
+
 inline bool
 irange_bitmask::operator== (const irange_bitmask &src) const
 {