From: Aldy Hernandez <aldyh@redhat.com>
To: GCC patches <gcc-patches@gcc.gnu.org>
Cc: Andrew MacLeod <amacleod@redhat.com>, Aldy Hernandez <aldyh@redhat.com>
Subject: [COMMITTED] Optimize [0 = x & MASK] in range-ops.
Date: Mon, 26 Sep 2022 19:24:41 +0200 [thread overview]
Message-ID: <20220926172441.3219466-1-aldyh@redhat.com> (raw)
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.
Tested on x86-64 Linux.
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.
---
gcc/range-op.cc | 18 ++++++++++++++++++
1 file changed, 18 insertions(+)
diff --git a/gcc/range-op.cc b/gcc/range-op.cc
index 072ebd32109..fc930f4d613 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);
--
2.37.1
next reply other threads:[~2022-09-26 17:24 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-26 17:24 Aldy Hernandez [this message]
2022-09-26 23:27 ` Jeff Law
2022-09-27 9:26 ` Mikael Morin
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