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* [gcc r12-6558] Add relation to unsigned right shift.
@ 2022-01-13 18:52 Andrew Macleod
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From: Andrew Macleod @ 2022-01-13 18:52 UTC (permalink / raw)
To: gcc-cvs
https://gcc.gnu.org/g:27e4260166950b784fe270ba4f0cae9a66faf1c4
commit r12-6558-g27e4260166950b784fe270ba4f0cae9a66faf1c4
Author: Andrew MacLeod <amacleod@redhat.com>
Date: Wed Jan 12 13:28:55 2022 -0500
Add relation to unsigned right shift.
If the first operand and the shift value of a right shift operation are both
>= 0, then we know the LHS of the operation is <= the first operand.
PR tree-optimization/96707
gcc/
* range-op.cc (operator_rshift::lhs_op1_relation): New.
gcc/testsuite/
* g++.dg/pr96707.C: New.
Diff:
---
gcc/range-op.cc | 16 ++++++++++++++++
gcc/testsuite/g++.dg/pr96707.C | 10 ++++++++++
2 files changed, 26 insertions(+)
diff --git a/gcc/range-op.cc b/gcc/range-op.cc
index a4f6e9eba29..19bdf30911a 100644
--- a/gcc/range-op.cc
+++ b/gcc/range-op.cc
@@ -1941,9 +1941,25 @@ public:
const irange &lhs,
const irange &op2,
relation_kind rel = VREL_NONE) const;
+ virtual enum tree_code lhs_op1_relation (const irange &lhs,
+ const irange &op1,
+ const irange &op2) const;
} op_rshift;
+enum tree_code
+operator_rshift::lhs_op1_relation (const irange &lhs ATTRIBUTE_UNUSED,
+ const irange &op1,
+ const irange &op2) const
+{
+ // If both operands range are >= 0, then the LHS <= op1.
+ if (!op1.undefined_p () && !op2.undefined_p ()
+ && wi::ge_p (op1.lower_bound (), 0, TYPE_SIGN (op1.type ()))
+ && wi::ge_p (op2.lower_bound (), 0, TYPE_SIGN (op2.type ())))
+ return LE_EXPR;
+ return VREL_NONE;
+}
+
bool
operator_lshift::fold_range (irange &r, tree type,
const irange &op1,
diff --git a/gcc/testsuite/g++.dg/pr96707.C b/gcc/testsuite/g++.dg/pr96707.C
new file mode 100644
index 00000000000..2653fe3d043
--- /dev/null
+++ b/gcc/testsuite/g++.dg/pr96707.C
@@ -0,0 +1,10 @@
+/* { dg-do compile} */
+/* { dg-options "-O2 -fdump-tree-evrp" } */
+
+bool f(unsigned x, unsigned y)
+{
+ return (x >> y) <= x;
+}
+
+/* { dg-final { scan-tree-dump "return 1" "evrp" } } */
+
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