* [PATCH] tree-optimization/96707 - Add relation to unsigned right shift.
@ 2022-01-13 13:57 Andrew MacLeod
2022-01-13 15:11 ` Richard Biener
0 siblings, 1 reply; 2+ messages in thread
From: Andrew MacLeod @ 2022-01-13 13:57 UTC (permalink / raw)
To: gcc-patches
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A quick addition to range ops for
LHS = OP1 >> OP2
if OP1 and OP2 are both >= 0, then we can register the relation LHS
<= OP1 and all the expected good things happen.
Bootstrapped on x86_64-pc-linux-gnu with no regressions.
OK for trunk?
Andrew
[-- Attachment #2: 0001-Add-relation-to-unsigned-right-shift.patch --]
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From c34dab537d6f54b66b430f5980cde278fa033904 Mon Sep 17 00:00:00 2001
From: Andrew MacLeod <amacleod@redhat.com>
Date: Wed, 12 Jan 2022 13:28:55 -0500
Subject: [PATCH 1/2] 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.c (operator_rshift::lhs_op1_relation): New.
gcc/testtsuite/
* g++.dg/pr96707.C: New.
---
gcc/range-op.cc | 16 ++++++++++++++++
gcc/testsuite/g++.dg/pr96707.C | 10 ++++++++++
2 files changed, 26 insertions(+)
create mode 100644 gcc/testsuite/g++.dg/pr96707.C
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" } } */
+
--
2.17.2
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: [PATCH] tree-optimization/96707 - Add relation to unsigned right shift.
2022-01-13 13:57 [PATCH] tree-optimization/96707 - Add relation to unsigned right shift Andrew MacLeod
@ 2022-01-13 15:11 ` Richard Biener
0 siblings, 0 replies; 2+ messages in thread
From: Richard Biener @ 2022-01-13 15:11 UTC (permalink / raw)
To: Andrew MacLeod; +Cc: gcc-patches
On Thu, Jan 13, 2022 at 2:58 PM Andrew MacLeod via Gcc-patches
<gcc-patches@gcc.gnu.org> wrote:
>
> A quick addition to range ops for
>
> LHS = OP1 >> OP2
>
> if OP1 and OP2 are both >= 0, then we can register the relation LHS
> <= OP1 and all the expected good things happen.
>
> Bootstrapped on x86_64-pc-linux-gnu with no regressions.
>
> OK for trunk?
OK.
>
> Andrew
^ permalink raw reply [flat|nested] 2+ messages in thread
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