# HG changeset patch
# User redestad
# Date 1554919387 -7200
# Node ID 9d0ae9508d5337b0dc7cc4684be42888c4023755
# Parent  a805bf992bf186108bece8573d41aeb7effccf21
8222029: Optimize Math.floorMod
Reviewed-by: aph, darcy

diff -r a805bf992bf1 -r 9d0ae9508d53 src/java.base/share/classes/java/lang/Math.java
--- a/src/java.base/share/classes/java/lang/Math.java	Wed Apr 10 05:15:50 2019 -0700
+++ b/src/java.base/share/classes/java/lang/Math.java	Wed Apr 10 20:03:07 2019 +0200
@@ -1274,7 +1274,12 @@
      * @since 1.8
      */
     public static int floorMod(int x, int y) {
-        return x - floorDiv(x, y) * y;
+        int mod = x % y;
+        // if the signs are different and modulo not zero, adjust result
+        if ((mod ^ y) < 0 && mod != 0) {
+            mod += y;
+        }
+        return mod;
     }
 
     /**
@@ -1301,7 +1306,7 @@
      */
     public static int floorMod(long x, int y) {
         // Result cannot overflow the range of int.
-        return (int)(x - floorDiv(x, y) * y);
+        return (int)floorMod(x, (long)y);
     }
 
     /**
@@ -1327,7 +1332,12 @@
      * @since 1.8
      */
     public static long floorMod(long x, long y) {
-        return x - floorDiv(x, y) * y;
+        long mod = x % y;
+        // if the signs are different and modulo not zero, adjust result
+        if ((x ^ y) < 0 && mod != 0) {
+            mod += y;
+        }
+        return mod;
     }
 
     /**
diff -r a805bf992bf1 -r 9d0ae9508d53 test/jdk/java/lang/Math/DivModTests.java
--- a/test/jdk/java/lang/Math/DivModTests.java	Wed Apr 10 05:15:50 2019 -0700
+++ b/test/jdk/java/lang/Math/DivModTests.java	Wed Apr 10 20:03:07 2019 +0200
@@ -91,6 +91,10 @@
         testIntFloorDivMod(Integer.MIN_VALUE, 3, -715827883, 1);
         testIntFloorDivMod(Integer.MIN_VALUE + 1, 3, -715827883, 2);
         testIntFloorDivMod(Integer.MIN_VALUE + 1, -1, Integer.MAX_VALUE, 0);
+        testIntFloorDivMod(Integer.MAX_VALUE, Integer.MAX_VALUE, 1, 0);
+        testIntFloorDivMod(Integer.MAX_VALUE, Integer.MIN_VALUE, -1, -1);
+        testIntFloorDivMod(Integer.MIN_VALUE, Integer.MIN_VALUE, 1, 0);
+        testIntFloorDivMod(Integer.MIN_VALUE, Integer.MAX_VALUE, -2, 2147483646);
         // Special case of integer overflow
         testIntFloorDivMod(Integer.MIN_VALUE, -1, Integer.MIN_VALUE, 0);
     }
@@ -179,6 +183,10 @@
         testLongFloorDivMod(Long.MIN_VALUE, 3L, Long.MIN_VALUE / 3L - 1L, 1L);
         testLongFloorDivMod(Long.MIN_VALUE + 1L, 3L, Long.MIN_VALUE / 3L - 1L, 2L);
         testLongFloorDivMod(Long.MIN_VALUE + 1, -1, Long.MAX_VALUE, 0L);
+        testLongFloorDivMod(Long.MAX_VALUE, Long.MAX_VALUE, 1L, 0L);
+        testLongFloorDivMod(Long.MAX_VALUE, Long.MIN_VALUE, -1L, -1L);
+        testLongFloorDivMod(Long.MIN_VALUE, Long.MIN_VALUE, 1L, 0L);
+        testLongFloorDivMod(Long.MIN_VALUE, Long.MAX_VALUE, -2L, 9223372036854775806L);
         // Special case of integer overflow
         testLongFloorDivMod(Long.MIN_VALUE, -1, Long.MIN_VALUE, 0L);
     }
@@ -283,6 +291,10 @@
         testLongIntFloorDivMod(Long.MIN_VALUE, 3, Long.MIN_VALUE / 3L - 1L, 1L);
         testLongIntFloorDivMod(Long.MIN_VALUE + 1L, 3, Long.MIN_VALUE / 3L - 1L, 2L);
         testLongIntFloorDivMod(Long.MIN_VALUE + 1, -1, Long.MAX_VALUE, 0L);
+        testLongIntFloorDivMod(Long.MAX_VALUE, Integer.MAX_VALUE, 4294967298L, 1);
+        testLongIntFloorDivMod(Long.MAX_VALUE, Integer.MIN_VALUE, -4294967296L, -1);
+        testLongIntFloorDivMod(Long.MIN_VALUE, Integer.MIN_VALUE, 4294967296L, 0);
+        testLongIntFloorDivMod(Long.MIN_VALUE, Integer.MAX_VALUE, -4294967299L, 2147483645);
         // Special case of integer overflow
         testLongIntFloorDivMod(Long.MIN_VALUE, -1, Long.MIN_VALUE, 0L);
     }
diff -r a805bf992bf1 -r 9d0ae9508d53 test/micro/org/openjdk/bench/java/lang/MathBench.java
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/test/micro/org/openjdk/bench/java/lang/MathBench.java	Wed Apr 10 20:03:07 2019 +0200
@@ -0,0 +1,95 @@
+/*
+ * Copyright (c) 2014 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.java.lang;
+
+import org.openjdk.jmh.annotations.Benchmark;
+import org.openjdk.jmh.annotations.BenchmarkMode;
+import org.openjdk.jmh.annotations.CompilerControl;
+import org.openjdk.jmh.annotations.Mode;
+import org.openjdk.jmh.annotations.OutputTimeUnit;
+import org.openjdk.jmh.annotations.Param;
+import org.openjdk.jmh.annotations.Scope;
+import org.openjdk.jmh.annotations.Setup;
+import org.openjdk.jmh.annotations.State;
+import org.openjdk.jmh.annotations.Threads;
+
+import java.util.Random;
+import java.util.concurrent.TimeUnit;
+
+@BenchmarkMode(Mode.AverageTime)
+@OutputTimeUnit(TimeUnit.NANOSECONDS)
+@State(Scope.Thread)
+public class MathBench {
+
+    @Param("0")
+    public long seed;
+
+    public int dividend;
+    public int divisor;
+
+    public long longDividend;
+    public long longDivisor;
+
+    @Setup
+    public void setupValues() {
+        Random random = new Random(seed);
+        dividend = Math.abs(random.nextInt() + 4711);
+        divisor  = Math.abs(random.nextInt(dividend) + 17);
+        longDividend = Math.abs(random.nextLong() + 4711L);
+        longDivisor  = Math.abs(random.nextLong() + longDividend);
+    }
+
+    @Benchmark
+    @CompilerControl(CompilerControl.Mode.DONT_INLINE)
+    public int floorModIntIntPositive() {
+        return Math.floorMod(dividend, divisor);
+    }
+
+    @Benchmark
+    @CompilerControl(CompilerControl.Mode.DONT_INLINE)
+    public int floorModIntInt() {
+        return Math.floorMod( dividend,  divisor) +
+               Math.floorMod( dividend, -divisor) +
+               Math.floorMod(-dividend,  divisor) +
+               Math.floorMod(-dividend, -divisor);
+    }
+
+    @Benchmark
+    @CompilerControl(CompilerControl.Mode.DONT_INLINE)
+    public int floorModLongInt() {
+        return Math.floorMod( longDividend,  divisor) +
+               Math.floorMod( longDividend, -divisor) +
+               Math.floorMod(-longDividend,  divisor) +
+               Math.floorMod(-longDividend, -divisor);
+    }
+
+    @Benchmark
+    @CompilerControl(CompilerControl.Mode.DONT_INLINE)
+    public long floorModLongLong() {
+        return Math.floorMod( longDividend,  longDivisor) +
+               Math.floorMod( longDividend, -longDivisor) +
+               Math.floorMod(-longDividend,  longDivisor) +
+               Math.floorMod(-longDividend, -longDivisor);
+    }
+
+}