8276673: Optimize abs operations in C2 compiler

src/hotspot/share/opto/subnode.cpp

@@ -1839,6 +1839,72 @@ bool BoolNode::is_counted_loop_exit_test() {
   return false;
 }
 
+//=============================================================================
+//------------------------------Value------------------------------------------
+const Type* AbsNode::Value(PhaseGVN* phase) const {
+  const Type* t1 = phase->type(in(1));
+  if (t1 == Type::TOP) return Type::TOP;
+
+  switch (t1->base()) {
+  case Type::Int: {
+    const TypeInt* ti = t1->is_int();
+    if (ti->is_con()) {
+      // Special case for min_jint: Math.abs(min_jint) = min_jint.
+      // Do not use C++ abs() for min_jint to avoid undefined behavior.
+      return (ti->is_con(min_jint)) ? TypeInt::MIN : TypeInt::make(abs(ti->get_con()));
+    }
+    break;
+  }
+  case Type::Long: {
+    const TypeLong* tl = t1->is_long();
+    if (tl->is_con()) {
+      // Special case for min_jlong: Math.abs(min_jlong) = min_jlong.
+      // Do not use C++ abs() for min_jlong to avoid undefined behavior.
+      return (tl->is_con(min_jlong)) ? TypeLong::MIN : TypeLong::make(abs(tl->get_con()));
+    }
+    break;
+  }
+  case Type::FloatCon:
+    return TypeF::make(abs(t1->getf()));
+  case Type::DoubleCon:
+    return TypeD::make(abs(t1->getd()));
+  default:
+    break;
+  }
+
+  return bottom_type();
+}
+
+//------------------------------Identity----------------------------------------
+Node* AbsNode::Identity(PhaseGVN* phase) {
+  Node* in1 = in(1);
+  // No need to do abs for non-negative values
+  if (phase->type(in1)->higher_equal(TypeInt::POS) ||
+      phase->type(in1)->higher_equal(TypeLong::POS)) {
+    return in1;
+  }
+  // Convert "abs(abs(x))" into "abs(x)"
+  if (in1->Opcode() == Opcode()) {
+    return in1;
+  }
+  return this;
+}
+
+//------------------------------Ideal------------------------------------------
+Node* AbsNode::Ideal(PhaseGVN* phase, bool can_reshape) {
+  Node* in1 = in(1);
+  // Convert "abs(0-x)" into "abs(x)"
+  if (in1->is_Sub() && phase->type(in1->in(1))->is_zero_type()) {
+    set_req(1, in1->in(2));
+    PhaseIterGVN* igvn = phase->is_IterGVN();
+    if (igvn) {
+      igvn->_worklist.push(in1);
+    }
+    return this;
+  }
+  return NULL;
+}
+
 //=============================================================================
 //------------------------------Value------------------------------------------
 // Compute sqrt

src/hotspot/share/opto/subnode.hpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1997, 2019, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1997, 2021, 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
@@ -347,6 +347,9 @@ class BoolNode : public Node {
 class AbsNode : public Node {
 public:
   AbsNode( Node *value ) : Node(0,value) {}
+  virtual Node* Identity(PhaseGVN* phase);
+  virtual Node* Ideal(PhaseGVN* phase, bool can_reshape);
+  virtual const Type* Value(PhaseGVN* phase) const;
 };
 
 //------------------------------AbsINode---------------------------------------

src/hotspot/share/opto/type.hpp

@@ -593,7 +593,7 @@ class TypeInt : public TypeInteger {
 
   // Check for single integer
   bool is_con() const { return _lo==_hi; }
-  bool is_con(int i) const { return is_con() && _lo == i; }
+  bool is_con(jint i) const { return is_con() && _lo == i; }
   jint get_con() const { assert(is_con(), "" );  return _lo; }
 
   virtual bool        is_finite() const;  // Has a finite value
@@ -661,7 +661,7 @@ class TypeLong : public TypeInteger {
 
   // Check for single integer
   bool is_con() const { return _lo==_hi; }
-  bool is_con(int i) const { return is_con() && _lo == i; }
+  bool is_con(jlong i) const { return is_con() && _lo == i; }
   jlong get_con() const { assert(is_con(), "" ); return _lo; }
 
   // Check for positive 32-bit value.

test/hotspot/jtreg/compiler/c2/TestAbs.java

@@ -21,17 +21,151 @@
  * questions.
  */
 
-package compiler.c2;
-
 /*
  * @test
- * @bug 8248445
- * @summary Use of AbsI / AbsL nodes should be limited to supported platforms
+ * @bug 8248445 8276673
+ * @summary Abs nodes detection and optimization in C2
+ * @library /test/lib
  * @requires vm.debug == true
  *
  * @run main/othervm -XX:-TieredCompilation -Xbatch -XX:CompileOnly=java.lang.Math::abs compiler.c2.TestAbs
+ * @run main/othervm -XX:-TieredCompilation compiler.c2.TestAbs
  */
+
+package compiler.c2;
+import jdk.test.lib.Asserts;
+
 public class TestAbs {
+    private static int SIZE = 500;
+
+    public static char [] cspecial = {
+        0, 42, 128, 256, 1024, 4096, 65535
+    };
+
+    public static int [] ispecial = {
+        0, Integer.MAX_VALUE, Integer.MIN_VALUE, -42, 42, -1, 1
+    };
+
+    public static long [] lspecial = {
+        0, Long.MAX_VALUE, Long.MIN_VALUE, -42, 42, -1, 1
+    };
+
+    public static float [] fspecial = {
+        0.0f,
+        -0.0f,
+        Float.MAX_VALUE,
+        Float.MIN_VALUE,
+        -Float.MAX_VALUE,
+        -Float.MIN_VALUE,
+        Float.NaN,
+        Float.POSITIVE_INFINITY,
+        Float.NEGATIVE_INFINITY,
+        Integer.MAX_VALUE,
+        Integer.MIN_VALUE,
+        Long.MAX_VALUE,
+        Long.MIN_VALUE,
+        -1.0f,
+        1.0f,
+        -42.0f,
+        42.0f
+    };
+
+    public static double [] dspecial = {
+        0.0,
+        -0.0,
+        Double.MAX_VALUE,
+        Double.MIN_VALUE,
+        -Double.MAX_VALUE,
+        -Double.MIN_VALUE,
+        Double.NaN,
+        Double.POSITIVE_INFINITY,
+        Double.NEGATIVE_INFINITY,
+        Integer.MAX_VALUE,
+        Integer.MIN_VALUE,
+        Long.MIN_VALUE,
+        Long.MAX_VALUE,
+        -1,
+        1,
+        42,
+        -42,
+        Math.PI,
+        Math.E,
+        Float.MAX_VALUE,
+        Float.MIN_VALUE,
+        -Float.MAX_VALUE,
+        -Float.MIN_VALUE,
+        Float.NaN,
+        Float.POSITIVE_INFINITY,
+        Float.NEGATIVE_INFINITY
+    };
+
+    public static void testAbsConstant() {
+        // Test abs(constant) optimization for int
+        Asserts.assertEquals(Integer.MAX_VALUE, Math.abs(Integer.MAX_VALUE));
+        Asserts.assertEquals(Integer.MIN_VALUE, Math.abs(Integer.MIN_VALUE));
+        Asserts.assertEquals(Integer.MAX_VALUE, Math.abs(-Integer.MAX_VALUE));
+
+        // Test abs(constant) optimization for long
+        Asserts.assertEquals(Long.MAX_VALUE, Math.abs(Long.MAX_VALUE));
+        Asserts.assertEquals(Long.MIN_VALUE, Math.abs(Long.MIN_VALUE));
+        Asserts.assertEquals(Long.MAX_VALUE, Math.abs(-Long.MAX_VALUE));
+
+        // Test abs(constant) optimization for float
+        Asserts.assertEquals(Float.NaN, Math.abs(Float.NaN));
+        Asserts.assertEquals(Float.POSITIVE_INFINITY, Math.abs(Float.NEGATIVE_INFINITY));
+        Asserts.assertEquals(Float.POSITIVE_INFINITY, Math.abs(Float.POSITIVE_INFINITY));
+        Asserts.assertEquals(0.0f, Math.abs(0.0f));
+        Asserts.assertEquals(0.0f, Math.abs(-0.0f));
+        Asserts.assertEquals(Float.MAX_VALUE, Math.abs(Float.MAX_VALUE));
+        Asserts.assertEquals(Float.MIN_VALUE, Math.abs(Float.MIN_VALUE));
+        Asserts.assertEquals(Float.MAX_VALUE, Math.abs(-Float.MAX_VALUE));
+        Asserts.assertEquals(Float.MIN_VALUE, Math.abs(-Float.MIN_VALUE));
+
+        // Test abs(constant) optimization for double
+        Asserts.assertEquals(Double.NaN, Math.abs(Double.NaN));
+        Asserts.assertEquals(Double.POSITIVE_INFINITY, Math.abs(Double.NEGATIVE_INFINITY));
+        Asserts.assertEquals(Double.POSITIVE_INFINITY, Math.abs(Double.POSITIVE_INFINITY));
+        Asserts.assertEquals(0.0, Math.abs(0.0));
+        Asserts.assertEquals(0.0, Math.abs(-0.0));
+        Asserts.assertEquals(Double.MAX_VALUE, Math.abs(Double.MAX_VALUE));
+        Asserts.assertEquals(Double.MIN_VALUE, Math.abs(Double.MIN_VALUE));
+        Asserts.assertEquals(Double.MAX_VALUE, Math.abs(-Double.MAX_VALUE));
+        Asserts.assertEquals(Double.MIN_VALUE, Math.abs(-Double.MIN_VALUE));
+    }
+
+    private static void testAbsTransformInt(int[] a) {
+        for (int i = 0; i < a.length; i++) {
+            Asserts.assertEquals(Math.abs(Math.abs(a[i])), Math.abs(a[i]));
+            Asserts.assertEquals(Math.abs(0 - a[i]), Math.abs(a[i]));
+        }
+    }
+
+    private static void testAbsTransformLong(long[] a) {
+        for (int i = 0; i < a.length; i++) {
+            Asserts.assertEquals(Math.abs(Math.abs(a[i])), Math.abs(a[i]));
+            Asserts.assertEquals(Math.abs(0 - a[i]), Math.abs(a[i]));
+        }
+    }
+
+    private static void testAbsTransformFloat(float[] a) {
+        for (int i = 0; i < a.length; i++) {
+            Asserts.assertEquals(Math.abs(Math.abs(a[i])), Math.abs(a[i]));
+            Asserts.assertEquals(Math.abs(0 - a[i]), Math.abs(a[i]));
+        }
+    }
+
+    private static void testAbsTransformDouble(double[] a) {
+        for (int i = 0; i < a.length; i++) {
+            Asserts.assertEquals(Math.abs(Math.abs(a[i])), Math.abs(a[i]));
+            Asserts.assertEquals(Math.abs(0 - a[i]), Math.abs(a[i]));
+        }
+    }
+
+    private static void testAbsOptChar(char[] a) {
+        for (int i = 0; i < a.length; i++) {
+            Asserts.assertEquals(a[i], (char) Math.abs(a[i]));
+        }
+    }
 
     public static void test() {
         // java.lang.Math.abs() collapses into AbsI/AbsL nodes on platforms that support the correspondent nodes
@@ -45,7 +179,20 @@ public static void test() {
     public static void main(String args[]) {
         for (int i = 0; i < 20_000; i++) {
             test();
+
+            testAbsConstant();
+
+            // Verify abs(abs(x)) = abs(x) for all types
+            // Verify abs(0-x) = abs(x) for all types
+            testAbsTransformInt(ispecial);
+            testAbsTransformLong(lspecial);
+            testAbsTransformFloat(fspecial);
+            testAbsTransformDouble(dspecial);
+
+            // Verify abs(non-negative_value) = non-negative_value
+            testAbsOptChar(cspecial);
         }
+
     }
 }
 

test/micro/org/openjdk/bench/java/lang/MathBench.java

@@ -101,6 +101,11 @@ public long  absLong() {
         return  Math.abs(long13);
     }
 
+    @Benchmark
+    public int absConstantInt() {
+        return Math.abs(-3);
+    }
+
     @Benchmark
     public double  acosDouble() {
         return  Math.acos(double1);