jdk/test/hotspot/jtreg/compiler/loopopts/TestLoopLimitOverflowDuringSplitThruPhi.java

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/*
 * @test
 * @bug 8335747
 * @summary Integer overflow in LoopLimit::Value during PhaseIdealLoop::split_thru_phi
 * @run main/othervm -Xbatch -XX:CompileCommand=compileonly,TestLoopLimitOverflowDuringSplitThruPhi::test
 *                   compiler.loopopts.TestLoopLimitOverflowDuringSplitThruPhi
 * @run driver compiler.loopopts.TestLoopLimitOverflowDuringSplitThruPhi
 */

package compiler.loopopts;

public class TestLoopLimitOverflowDuringSplitThruPhi {
    public static void main(String[] args) {
        int[] a = new int[1005];
        for (int i = 0; i < 20_000; i++) {
            test(i % 2 == 0, a);
        }
    }

    static void test(boolean flag, int[] a) {
        int x = flag ? 1000 : 2147483647;
        // Creates a Phi(1000, 2147483647)

        // We do loop-predication, and add a
        //   LoopLimitNode(init=0, limit=x, stride=4)
        //
        // Later, we find try to PhaseIdealLoop::split_thru_phi
        // the LoopLimitNode, through the Phi(1000, 2147483647).
        //
        // This creates a temporary
        //   LoopLimitNode(init=0, limit=2147483647, stride=4)
        //
        // And then we get this:
        //   init_con 0
        //   limit_con 2147483647
        //   stride_con 4
        //   trip_count 536870912
        //   final_int -2147483648
        //   final_con 2147483648
        //
        for (int i = 0; i < x; i+=4 /* works for at least 2..64 */) {
            // Break before going out of bounds
            // but with quadratic check to not affect limit.
            if (i * i > 1000_000) { return; }
            a[i] = 34;
        }
    }
}