From: Aldy Hernandez <aldyh@redhat.com>
Date: Fri, 23 Sep 2022 17:47:19 +0000 (+0200)
Subject: Optimize [0 = x & MASK] in range-ops.
X-Git-Tag: basepoints/gcc-14~4327
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=5e77d4082fa845f1182641a93cfbae71984244d2;p=thirdparty%2Fgcc.git

Optimize [0 = x & MASK] in range-ops.

For [0 = x & MASK], we can determine that x is ~MASK.  This is
something we're picking up in DOM thanks to maybe_set_nonzero_bits,
but is something we should handle natively.

This is a good example of how much easier to maintain the range-ops
entries are versus the ad-hoc pattern matching stuff we had to do
before.  For the curious, compare the changes to range-op here,
versus maybe_set_nonzero_bits.

I'm leaving the call to maybe_set_nonzero_bits until I can properly
audit it to make sure we're catching it all in range-ops.  It won't
hurt, since both set_range_info() and set_nonzero_bits() are
intersect operations, so we'll never lose information if we do both.

	PR tree-optimization/107009

gcc/ChangeLog:

	* range-op.cc (operator_bitwise_and::op1_range): Optimize 0 = x & MASK.
	(range_op_bitwise_and_tests): New test.
---

diff --git a/gcc/range-op.cc b/gcc/range-op.cc
index 072ebd321090..fc930f4d6130 100644
--- a/gcc/range-op.cc
+++ b/gcc/range-op.cc
@@ -2951,6 +2951,15 @@ operator_bitwise_and::op1_range (irange &r, tree type,
     }
   if (r.undefined_p ())
     set_nonzero_range_from_mask (r, type, lhs);
+
+  // For 0 = op1 & MASK, op1 is ~MASK.
+  if (lhs.zero_p () && op2.singleton_p ())
+    {
+      wide_int nz = wi::bit_not (op2.get_nonzero_bits ());
+      int_range<2> tmp (type);
+      tmp.set_nonzero_bits (nz);
+      r.intersect (tmp);
+    }
   return true;
 }
 
@@ -4612,6 +4621,15 @@ range_op_bitwise_and_tests ()
   op_bitwise_and.op1_range (res, integer_type_node, i1, i2);
   ASSERT_TRUE (res == int_range<1> (integer_type_node));
 
+  // For 0 = x & MASK, x is ~MASK.
+  {
+    int_range<2> zero (integer_zero_node, integer_zero_node);
+    int_range<2> mask = int_range<2> (INT (7), INT (7));
+    op_bitwise_and.op1_range (res, integer_type_node, zero, mask);
+    wide_int inv = wi::shwi (~7U, TYPE_PRECISION (integer_type_node));
+    ASSERT_TRUE (res.get_nonzero_bits () == inv);
+  }
+
   // (NONZERO | X) is nonzero.
   i1.set_nonzero (integer_type_node);
   i2.set_varying (integer_type_node);