jdk-24/test/hotspot/jtreg/compiler/loopopts/superword/TestGeneralizedReductions.java

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/**
 * @test
 * @bug 8287087
 * @summary Test reduction vectorizations that are enabled by performing SLP
 *          reduction analysis on unrolled loops.
 * @library /test/lib /
 * @run driver compiler.loopopts.superword.TestGeneralizedReductions
 */

package compiler.loopopts.superword;

import compiler.lib.ir_framework.*;
import jdk.test.lib.Asserts;

public class TestGeneralizedReductions {

    private static int acc = 0;

    public static void main(String[] args) throws Exception {
        // Fix maximum number of unrolls for test stability.
        TestFramework.runWithFlags("-XX:+IgnoreUnrecognizedVMOptions", "-XX:LoopMaxUnroll=16");
    }

    @Run(test = {"testReductionOnGlobalAccumulator",
                 "testReductionOnPartiallyUnrolledLoop",
                 "testReductionOnLargePartiallyUnrolledLoop",
                 "testReductionOnPartiallyUnrolledLoopWithSwappedInputs",
                 "testMapReductionOnGlobalAccumulator"})
    void run() {
        long[] array = new long[128];
        long result;

        initArray(array);
        result = testReductionOnGlobalAccumulator(array);
        Asserts.assertEQ(result, 8128L, "unexpected result");

        initArray(array);
        result = testReductionOnPartiallyUnrolledLoop(array);
        Asserts.assertEQ(result, 8128L, "unexpected result");

        initArray(array);
        result = testReductionOnLargePartiallyUnrolledLoop(array);
        Asserts.assertEQ(result, 8128L, "unexpected result");

        initArray(array);
        result = testReductionOnPartiallyUnrolledLoopWithSwappedInputs(array);
        Asserts.assertEQ(result, 8128L, "unexpected result");

        initArray(array);
        result = testMapReductionOnGlobalAccumulator(array);
        Asserts.assertEQ(result, 448L, "unexpected result");
    }

    private static void initArray(long[] array) {
        for (int i = 0; i < array.length; i++) {
            array[i] = i;
        }
    }

    @Test
    @IR(applyIfCPUFeature = {"avx2", "true"},
        applyIf = {"SuperWordReductions", "true"},
        applyIfPlatform = {"64-bit", "true"},
        counts = {IRNode.ADD_REDUCTION_VI, ">= 1"})
    private static long testReductionOnGlobalAccumulator(long[] array) {
        acc = 0;
        for (int i = 0; i < array.length; i++) {
            acc += array[i];
        }
        return acc;
    }

    @Test
    @IR(applyIfCPUFeature = {"avx2", "true"},
        applyIf = {"SuperWordReductions", "true"},
        applyIfPlatform = {"64-bit", "true"},
        counts = {IRNode.ADD_REDUCTION_VI, ">= 1"})
    private static long testReductionOnPartiallyUnrolledLoop(long[] array) {
        int sum = 0;
        for (int i = 0; i < array.length / 2; i++) {
            sum += array[2*i];
            sum += array[2*i + 1];
        }
        return sum;
    }

    @Test
    @IR(applyIfCPUFeature = {"avx2", "true"},
        applyIf = {"SuperWordReductions", "true"},
        applyIfPlatform = {"64-bit", "true"},
        counts = {IRNode.ADD_REDUCTION_VI, ">= 1"})
    private static long testReductionOnLargePartiallyUnrolledLoop(long[] array) {
        int sum = 0;
        for (int i = 0; i < array.length / 8; i++) {
            sum += array[8*i];
            sum += array[8*i + 1];
            sum += array[8*i + 2];
            sum += array[8*i + 3];
            sum += array[8*i + 4];
            sum += array[8*i + 5];
            sum += array[8*i + 6];
            sum += array[8*i + 7];
        }
        return sum;
    }

    // This test illustrates a limitation of the current reduction analysis: it
    // fails to detect reduction cycles where nodes are connected via different
    // input indices (except if the differences result from C2 edge swapping).
    // If this limitation is overcome in the future, the test case should be
    // turned into a positive one.
    @Test
    @IR(applyIfCPUFeature = {"avx2", "true"},
        applyIf = {"SuperWordReductions", "true"},
        applyIfPlatform = {"64-bit", "true"},
        failOn = {IRNode.ADD_REDUCTION_VI})
    private static long testReductionOnPartiallyUnrolledLoopWithSwappedInputs(long[] array) {
        int sum = 0;
        for (int i = 0; i < array.length / 2; i++) {
            sum = sum + (int)array[2*i];
            sum = (int)array[2*i + 1] + sum;
        }
        return sum;
    }

    @Test
    @IR(applyIfCPUFeature = {"avx2", "true"},
        applyIfAnd = {"SuperWordReductions", "true","UsePopCountInstruction", "true"},
        applyIfPlatform = {"64-bit", "true"},
        counts = {IRNode.ADD_REDUCTION_VI, ">= 1",
                  IRNode.POPCOUNT_VL, ">= 1"})
    @IR(applyIfPlatform = {"riscv64", "true"},
        applyIfCPUFeature = {"zvbb", "true"},
        applyIfAnd = {"SuperWordReductions", "true","UsePopCountInstruction", "true"},
        counts = {IRNode.ADD_REDUCTION_VI, ">= 1",
                  IRNode.POPCOUNT_VL, ">= 1"})
    private static long testMapReductionOnGlobalAccumulator(long[] array) {
        acc = 0;
        for (int i = 0; i < array.length; i++) {
            acc += Long.bitCount(array[i]);
        }
        return acc;
    }
}