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8273021: C2: Improve Add and Xor ideal optimizations #5266

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8273021: C2: Improve Add and Xor ideal optimizations #5266

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159f3ca
2scomplement
y1yang0 Aug 24, 2021
2f6ceb3
test
y1yang0 Aug 26, 2021
ff3087a
constatn is ensured in the second operand due to commute; combine con…
y1yang0 Sep 8, 2021
7bfda74
more random
y1yang0 Sep 8, 2021
e8a930b
dontinline
y1yang0 Sep 8, 2021
aee3a8b
review from Tobias
y1yang0 Sep 10, 2021
cceb061
change
y1yang0 Sep 10, 2021
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45 changes: 44 additions & 1 deletion src/hotspot/share/opto/addnode.cpp
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Expand Up @@ -397,6 +397,13 @@ Node *AddINode::Ideal(PhaseGVN *phase, bool can_reshape) {
}
}

// Convert (~x+1) into -x. Note there isn't a bitwise not bytecode,
// "~x" would typically represented as "x^(-1)", so (~x+1) will
// be (x^(-1))+1.
if (op1 == Op_XorI && phase->type(in2) == TypeInt::ONE &&
phase->type(in1->in(2)) == TypeInt::MINUS_1) {
return new SubINode(phase->makecon(TypeInt::ZERO), in1->in(1));
}
return AddNode::Ideal(phase, can_reshape);
}

Expand Down Expand Up @@ -554,7 +561,13 @@ Node *AddLNode::Ideal(PhaseGVN *phase, bool can_reshape) {
}
}


// Convert (~x+1) into -x. Note there isn't a bitwise not bytecode,
// "~x" would typically represented as "x^(-1)", so (~x+1) will
// be (x^(-1))+1
if (op1 == Op_XorL && phase->type(in2) == TypeLong::ONE &&
phase->type(in1->in(2)) == TypeLong::MINUS_1) {
return new SubLNode(phase->makecon(TypeLong::ZERO), in1->in(1));
}
return AddNode::Ideal(phase, can_reshape);
}

Expand Down Expand Up @@ -967,6 +980,21 @@ const Type *OrLNode::add_ring( const Type *t0, const Type *t1 ) const {
}

//=============================================================================
//------------------------------Idealize---------------------------------------
Node* XorINode::Ideal(PhaseGVN* phase, bool can_reshape) {
Node* in1 = in(1);
Node* in2 = in(2);
int op1 = in1->Opcode();
// Convert ~(x-1) into -x. Note there isn't a bitwise not bytecode,
// "~x" would typically represented as "x^(-1)", and "x-c0" would
// convert into "x+ -c0" in SubXNode::Ideal. So ~(x-1) will eventually
// be (x+(-1))^-1.
if (op1 == Op_AddI && phase->type(in2) == TypeInt::MINUS_1 &&
phase->type(in1->in(2)) == TypeInt::MINUS_1) {
return new SubINode(phase->makecon(TypeInt::ZERO), in1->in(1));
}
return AddNode::Ideal(phase, can_reshape);
}

const Type* XorINode::Value(PhaseGVN* phase) const {
Node* in1 = in(1);
Expand Down Expand Up @@ -1032,6 +1060,21 @@ const Type *XorLNode::add_ring( const Type *t0, const Type *t1 ) const {
return TypeLong::make( r0->get_con() ^ r1->get_con() );
}

Node* XorLNode::Ideal(PhaseGVN* phase, bool can_reshape) {
Node* in1 = in(1);
Node* in2 = in(2);
int op1 = in1->Opcode();
// Convert ~(x-1) into -x. Note there isn't a bitwise not bytecode,
// "~x" would typically represented as "x^(-1)", and "x-c0" would
// convert into "x+ -c0" in SubXNode::Ideal. So ~(x-1) will eventually
// be (x+(-1))^-1.
if (op1 == Op_AddL && phase->type(in2) == TypeLong::MINUS_1 &&
phase->type(in1->in(2)) == TypeLong::MINUS_1) {
return new SubLNode(phase->makecon(TypeLong::ZERO), in1->in(1));
}
return AddNode::Ideal(phase, can_reshape);
}

const Type* XorLNode::Value(PhaseGVN* phase) const {
Node* in1 = in(1);
Node* in2 = in(2);
Expand Down
2 changes: 2 additions & 0 deletions src/hotspot/share/opto/addnode.hpp
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Expand Up @@ -227,6 +227,7 @@ class XorINode : public AddNode {
public:
XorINode( Node *in1, Node *in2 ) : AddNode(in1,in2) {}
virtual int Opcode() const;
virtual Node *Ideal(PhaseGVN *phase, bool can_reshape);
virtual const Type *add_ring( const Type *, const Type * ) const;
virtual const Type *add_id() const { return TypeInt::ZERO; }
virtual const Type *bottom_type() const { return TypeInt::INT; }
Expand All @@ -242,6 +243,7 @@ class XorLNode : public AddNode {
public:
XorLNode( Node *in1, Node *in2 ) : AddNode(in1,in2) {}
virtual int Opcode() const;
virtual Node *Ideal(PhaseGVN *phase, bool can_reshape);
virtual const Type *add_ring( const Type *, const Type * ) const;
virtual const Type *add_id() const { return TypeLong::ZERO; }
virtual const Type *bottom_type() const { return TypeLong::LONG; }
Expand Down
97 changes: 97 additions & 0 deletions test/hotspot/jtreg/compiler/c2/TestAddXorIdeal.java
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@@ -0,0 +1,97 @@
/*
* Copyright (c) 2021, Alibaba Group Holding Limited. All Rights Reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*
*/

/*
* @test
* @bug 8273021
* @summary C2: Improve Add and Xor ideal optimizations
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The test needs * @key randomness

* @library /test/lib
* @run main/othervm -XX:-TieredCompilation -XX:TieredStopAtLevel=4
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TieredStopAtLevel has no effect if Tiered Compilation is turned off. You can remove it.

* -XX:CompileCommand=dontinline,compiler.c2.TestAddXorIdeal::test*
* compiler.c2.TestAddXorIdeal
*/
package compiler.c2;

import java.util.Random;

import jdk.test.lib.Asserts;

public class TestAddXorIdeal {

public static int test1(int x) {
return ~x + 1;
}

public static int test2(int x) {
return ~(x - 1);
}

public static long test3(long x) {
return ~x + 1L;
}

public static long test4(long x) {
return ~(x - 1L);
}

public static int test5(int x) {
return 1 + ~x;
}

public static int test6(int x) {
return ~(-1 + x);
}

public static long test7(long x) {
return 1L + ~x;
}

public static long test8(long x) {
return ~(-1L + x);
}

public static void main(String... args) {
Random random = new Random();
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You should use Utils.getRandomInstance() from import jdk.test.lib.Utils to ensure that the seed is printed for reproducibility. You can check other tests for an example.

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That does make sense. Changed.

int n = 0;
long n1 = 0;
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Should be declared in the loop.

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Do you mean declared within loop body? I've changed but it looks like a perference problem.

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Yes, in Java, local variables should be declared as close as possible to the point they are first used at (see, for example, Google's Java Style Guide). The declaration does not affect performance.

Here's how I would write the loop to improve readability:

for (int j = 0; j < 50_000; j++) {
  int i = random.nextInt();
  long l = random.nextLong();
  Asserts.assertTrue(test1(i) == -i);
  Asserts.assertTrue(test2(i) == -i);
  Asserts.assertTrue(test3(l) == -l);
  ...

Summary: No need to use negative initial value for loop induction variable (as it is not even used), increase number of iterations to ensure C2 compilation (you are running without -Xbatch), use same random numbers per loop iteration, use more intuitive variable names.

But these are just code style details, feel free to ignore.

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Thanks for patient. I agree with your comment that using 0 as initial value and increasing iterations. :)

I try to use a and b as variable names since long l looks like long 1

for (int i = -5_000; i < 5_000; i++) {
n = random.nextInt();
Asserts.assertTrue(test1(i + n) == -(i + n));
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Now that you are using random numbers, can't you simply check Asserts.assertTrue(test1(n) == -n)? And just loop for a fixed number of iterations.

n = random.nextInt();
Asserts.assertTrue(test2(i - n) == -(i - n));
n1 = random.nextLong();
Asserts.assertTrue(test3(i + n1) == -(i + n1));
n1 = random.nextLong();
Asserts.assertTrue(test4(i - n1) == -(i - n1));
n = random.nextInt();
Asserts.assertTrue(test5(i + n) == -(i + n));
n = random.nextInt();
Asserts.assertTrue(test6(i - n) == -(i - n));
n1 = random.nextLong();
Asserts.assertTrue(test7(i + n1) == -(i + n1));
n1 = random.nextLong();
Asserts.assertTrue(test8(i - n1) == -(i - n1));
}
}
}