8278114: New addnode ideal optimization: converting "x + x" into "x << 1"

Reviewed-by: kvn, redestad

src/hotspot/share/opto/mulnode.cpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1997, 2021, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1997, 2022, Oracle and/or its affiliates. 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
@@ -789,16 +789,24 @@ Node *LShiftINode::Ideal(PhaseGVN *phase, bool can_reshape) {
     return NULL;
   }
 
-  // Left input is an add of a constant?
+  // Left input is an add?
   Node *add1 = in(1);
   int add1_op = add1->Opcode();
   if( add1_op == Op_AddI ) {    // Left input is an add?
     assert( add1 != add1->in(1), "dead loop in LShiftINode::Ideal" );
-    const TypeInt *t12 = phase->type(add1->in(2))->isa_int();
+
-    if( t12 && t12->is_con() ){ // Left input is an add of a con?
+    // Transform is legal, but check for profit.  Avoid breaking 'i2s'
-      // Transform is legal, but check for profit.  Avoid breaking 'i2s'
+    // and 'i2b' patterns which typically fold into 'StoreC/StoreB'.
-      // and 'i2b' patterns which typically fold into 'StoreC/StoreB'.
+    if( con < 16 ) {
-      if( con < 16 ) {
+      // Left input is an add of the same number?
+      if (add1->in(1) == add1->in(2)) {
+        // Convert "(x + x) << c0" into "x << (c0 + 1)"
+        return new LShiftINode(add1->in(1), phase->intcon(con + 1));
+      }
+
+      // Left input is an add of a constant?
+      const TypeInt *t12 = phase->type(add1->in(2))->isa_int();
+      if( t12 && t12->is_con() ){ // Left input is an add of a con?
         // Compute X << con0
         Node *lsh = phase->transform( new LShiftINode( add1->in(1), in(2) ) );
         // Compute X<<con0 + (con1<<con0)
@@ -902,12 +910,20 @@ Node *LShiftLNode::Ideal(PhaseGVN *phase, bool can_reshape) {
     return NULL;
   }
 
-  // Left input is an add of a constant?
+  // Left input is an add?
   Node *add1 = in(1);
   int add1_op = add1->Opcode();
   if( add1_op == Op_AddL ) {    // Left input is an add?
     // Avoid dead data cycles from dead loops
     assert( add1 != add1->in(1), "dead loop in LShiftLNode::Ideal" );
+
+    // Left input is an add of the same number?
+    if (add1->in(1) == add1->in(2)) {
+      // Convert "(x + x) << c0" into "x << (c0 + 1)"
+      return new LShiftLNode(add1->in(1), phase->intcon(con + 1));
+    }
+
+    // Left input is an add of a constant?
     const TypeLong *t12 = phase->type(add1->in(2))->isa_long();
     if( t12 && t12->is_con() ){ // Left input is an add of a con?
       // Compute X << con0

test/hotspot/jtreg/compiler/c2/irTests/TestIRLShiftIdeal_XPlusX_LShiftC.java

@@ -0,0 +1,151 @@
+/*
+ * Copyright (c) 2022, Oracle and/or its affiliates. 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.
+ */
+
+package compiler.c2.irTests;
+
+import jdk.test.lib.Asserts;
+import compiler.lib.ir_framework.*;
+
+/*
+ * @test
+ * @bug 8278114
+ * @summary Test that transformation from (x + x) >> c to x >> (c + 1) works as intended.
+ * @library /test/lib /
+ * @run driver compiler.c2.irTests.TestIRLShiftIdeal_XPlusX_LShiftC
+ */
+public class TestIRLShiftIdeal_XPlusX_LShiftC {
+
+    private static final int[] INT_IN = {
+        -10, -2, -1, 0, 1, 2, 10,
+        0x8000_0000, 0x7FFF_FFFF, 0x5678_1234,
+    };
+
+    private static final int[][] INT_OUT = {
+        // Do testInt0(x) for each x in INT_IN
+        {
+            -160, -32, -16, 0, 16, 32, 160,
+            0x0000_0000, 0xFFFF_FFF0, 0x6781_2340,
+        },
+
+        // Do testInt1(x) for each x in INT_IN
+        {
+            -10485760, -2097152, -1048576, 0, 1048576, 2097152, 10485760,
+            0x0000_0000, 0xFFF0_0000, 0x2340_0000,
+        },
+    };
+
+    private static final long[] LONG_IN = {
+        -10L, -2L, -1L, 0L, 1L, 2L, 10L,
+        0x8000_0000_0000_0000L, 0x7FFF_FFFF_FFFF_FFFFL, 0x5678_1234_4321_8765L,
+    };
+
+    private static final long[][] LONG_OUT = {
+        // Do testLong0(x) for each x in LONG_IN
+        {
+            -160L, -32L, -16L, 0L, 16L, 32L, 160L,
+            0x0000_0000_0000_0000L, 0xFFFF_FFFF_FFFF_FFF0L, 0x6781_2344_3218_7650L,
+        },
+
+        // Do testLong1(x) for each x in LONG_IN
+        {
+            -687194767360L, -137438953472L, -68719476736L, 0L, 68719476736L, 137438953472L, 687194767360L,
+            0x0000_0000_0000_0000L, 0xFFFF_FFF0_0000_0000L, 0x3218_7650_0000_0000L,
+        },
+    };
+
+    public static void main(String[] args) {
+        TestFramework.run();
+    }
+
+    @Test
+    @IR(failOn = {IRNode.ADD_I, IRNode.MUL_I})
+    @IR(counts = {IRNode.LSHIFT_I, "1"})
+    public int testInt0(int x) {
+        return (x + x) << 3; // transformed to x << 4
+    }
+
+    @Run(test = "testInt0")
+    public void checkTestInt0(RunInfo info) {
+        assertC2Compiled(info);
+        for (int i = 0; i < INT_IN.length; i++) {
+            Asserts.assertEquals(INT_OUT[0][i], testInt0(INT_IN[i]));
+        }
+    }
+
+    @Test
+    @IR(failOn = {IRNode.MUL_I})
+    @IR(counts = {IRNode.LSHIFT_I, "1",
+                  IRNode.ADD_I, "1"})
+    public int testInt1(int x) {
+        return (x + x) << 19; // no transformation because 19 is
+                              // greater than 16 (see implementation
+                              // in LShiftINode::Ideal)
+    }
+
+    @Run(test = "testInt1")
+    public void checkTestInt1(RunInfo info) {
+        assertC2Compiled(info);
+        for (int i = 0; i < INT_IN.length; i++) {
+            Asserts.assertEquals(INT_OUT[1][i], testInt1(INT_IN[i]));
+        }
+    }
+
+    @Test
+    @IR(failOn = {IRNode.ADD_L, IRNode.MUL_L})
+    @IR(counts = {IRNode.LSHIFT_L, "1"})
+    public long testLong0(long x) {
+        return (x + x) << 3; // transformed to x << 4
+    }
+
+    @Run(test = "testLong0")
+    public void checkTestLong0(RunInfo info) {
+        assertC2Compiled(info);
+        for (int i = 0; i < LONG_IN.length; i++) {
+            Asserts.assertEquals(LONG_OUT[0][i], testLong0(LONG_IN[i]));
+        }
+    }
+
+    @Test
+    @IR(failOn = {IRNode.ADD_L, IRNode.MUL_L})
+    @IR(counts = {IRNode.LSHIFT_L, "1"})
+    public long testLong1(long x) {
+        return (x + x) << 35; // transformed to x << 36
+    }
+
+    @Run(test = "testLong1")
+    public void checkTestLong1(RunInfo info) {
+        assertC2Compiled(info);
+        for (int i = 0; i < LONG_IN.length; i++) {
+            Asserts.assertEquals(LONG_OUT[1][i], testLong1(LONG_IN[i]));
+        }
+    }
+
+    private void assertC2Compiled(RunInfo info) {
+        // Test VM allows C2 to work
+        Asserts.assertTrue(info.isC2CompilationEnabled());
+        if (!info.isWarmUp()) {
+            // C2 compilation happens
+            Asserts.assertTrue(info.isTestC2Compiled());
+        }
+    }
+}

test/hotspot/jtreg/compiler/lib/ir_framework/IRNode.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2021, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2022, Oracle and/or its affiliates. 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
@@ -141,6 +141,8 @@ public class IRNode {
     public static final String ADD_L = START + "AddL" + MID + END;
     public static final String SUB_I = START + "SubI" + MID + END;
     public static final String SUB_L = START + "SubL" + MID + END;
+    public static final String MUL_I = START + "MulI" + MID + END;
+    public static final String MUL_L = START + "MulL" + MID + END;
     public static final String CONV_I2L = START + "ConvI2L" + MID + END;
 
     public static final String VECTOR_CAST_B2X = START + "VectorCastB2X" + MID + END;

test/micro/org/openjdk/bench/vm/compiler/LShiftIdeal_XPlusX_LShiftC.java

@@ -0,0 +1,94 @@
+/*
+ * Copyright (c) 2022, Oracle and/or its affiliates. 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.
+ */
+
+package org.openjdk.bench.vm.compiler;
+
+import org.openjdk.jmh.annotations.Benchmark;
+import org.openjdk.jmh.annotations.BenchmarkMode;
+import org.openjdk.jmh.annotations.CompilerControl;
+import org.openjdk.jmh.annotations.Fork;
+import org.openjdk.jmh.annotations.Measurement;
+import org.openjdk.jmh.annotations.Mode;
+import org.openjdk.jmh.annotations.Scope;
+import org.openjdk.jmh.annotations.Setup;
+import org.openjdk.jmh.annotations.State;
+import org.openjdk.jmh.annotations.OutputTimeUnit;
+import org.openjdk.jmh.annotations.Warmup;
+import org.openjdk.jmh.infra.Blackhole;
+
+import java.util.concurrent.TimeUnit;
+
+/**
+ * Tests transformation from "(x + x) << c" to "x << (c + 1)".
+ * <p>
+ * This benchmark needs to be run with {@code
+ * JAVA_OPTIONS=-Djmh.blackhole.mode=COMPILER} to force using compiler
+ * mode blackhole, which is enabled by default and thus not necessary
+ * since JMH 1.34.
+ */
+@BenchmarkMode(Mode.AverageTime)
+@OutputTimeUnit(TimeUnit.NANOSECONDS)
+@State(Scope.Thread)
+@Warmup(iterations = 20, time = 1, timeUnit = TimeUnit.SECONDS)
+@Measurement(iterations = 20, time = 1, timeUnit = TimeUnit.SECONDS)
+@Fork(value = 3)
+public class LShiftIdeal_XPlusX_LShiftC {
+
+    private int iFld = 4711;
+
+    private long lFld = 4711 * 4711 * 4711;
+
+    private final int SIZE = 10;
+
+    @Benchmark
+    public void baselineInt(Blackhole bh) {
+        for (int i = 0; i < SIZE; i++) {
+            bh.consume(iFld);
+        }
+    }
+
+    @Benchmark
+    public void baselineLong(Blackhole bh) {
+        for (int i = 0; i < SIZE; i++) {
+            bh.consume(lFld);
+        }
+    }
+
+    // Convert "(x + x) << 10" into "x << 11" for int.
+    // (x << 11) >>> 11 is then further converted into zero-extends.
+    @Benchmark
+    public void testInt(Blackhole bh) {
+        for (int i = 0; i < SIZE; i++) {
+            bh.consume(((iFld + iFld) << 10) >>> 11);
+        }
+    }
+
+    // Convert "(x + x) << 40" into "x << 41" for long.
+    // (x << 41) >>> 41 is then further converted into zero-extends.
+    @Benchmark
+    public void testLong(Blackhole bh) {
+        for (int i = 0; i < SIZE; i++) {
+            bh.consume(((lFld + lFld) << 40) >>> 41);
+        }
+    }
+}