Compilation Fails even from noOpt Level

[connglli]

Java -version output

openjdk version "11.0.16-internal" 2022-07-19
OpenJDK Runtime Environment (build 11.0.16-internal+0-adhoc..openj9-openjdk-jdk11)
Eclipse OpenJ9 VM (build master-4ca209b54, JRE 11 Linux amd64-64-Bit Compressed References 20220615_000000 (JIT enabled, AOT enabled)
OpenJ9   - 4ca209b54
OMR      - 26b89f9f9
JCL      - 231dcc9eeb based on jdk-11.0.16+6)


openjdk version "1.8.0_342-internal"
OpenJDK Runtime Environment (build 1.8.0_342-internal-_2022_06_10_15_18-b00)
Eclipse OpenJ9 VM (build master-3d06b2f9c, JRE 1.8.0 Linux amd64-64-Bit Compressed References 20220610_000000 (JIT enabled, AOT enabled)
OpenJ9   - 3d06b2f9c
OMR      - cf8ddbd1a
JCL      - 2bb179375a based on jdk8u342-b05)

Summary of problem

Looks like the test fails from noOpt level, so it should be different from #15306 and #15347. This affects both JDK11 and JDK8.

class Test {
  int N = 256;

  void mainTest(String[] strArr1) {
    int i26, i28, i32;
    byte[] byArr = new byte[N];
    for (i26 = 12; i26 < 222; ++i26) {
      for (i28 = 24; i28 > 1; i28 -= 3) for (i32 = 1; i32 < 4; i32 += 2) byArr[i28] -= i32;
      for (int ax$14 = 3005; ax$14 < 6948; ax$14 += 1) {
        boolean[] ax$11 = new boolean[576];
      }
    }
    long ccc = checkSum(byArr);
    System.out.println(ccc);
  }

  public static void main(String[] strArr) {
    Test _instance = new Test();
    _instance.mainTest(strArr);
  }

  public static long checkSum(byte[] a) {
    long sum = 0;
    for (int j = 0; j < a.length; j++) {
      sum += (byte) (a[j] / (j + 1) + a[j] % (j + 1));
    }
    return sum;
  }
}

Results of OpenJ9:

$ ./OpenJ9/jdk11/java Test
0

Results of OpenJ9-Xint (HotSpot/ART also give the same result):

$ ./OpenJ9/jdk11/java -Xint Test
-114

Diagnosis

If you exclude Test.mainTest() from compilation, then it gives the same result as HotSpot/ART/OpenJ9-Xint

$ ./OpenJ9/jdk11/bin/java '-Xjit:exclude={Test.mainTest(*)*}' Test        
-114

But if you compile Test.mainTest() even from noOpt level, it gives 0 again

$ ./OpenJ9/jdk11/bin/java '-Xjit:{Test.mainTest(*)*}(optlevel=noOpt)' Test
0

So I reckon this to be different from 15306 (scorching) and 15347 (hot). (So is JDK8.)

[pshipton]

@0xdaryl fyi

[pshipton]

No problem reproducing this.

[BradleyWood]

I will take a look at this

[0xdaryl]

This is not a regression in 0.33. Reproducible on JDK8 back to at least 0.29.

[BradleyWood]

This looks like a DTL issue. I duplicated the call to mainTest() a number of times. The result was zero only on the first iteration. Disabling DLT achieved the correct result in all cases.

[BradleyWood]

Looks like the type information is not preserved for the DLT compile where byArr is stored.
byte[] byArr = new byte[N];

During IL-Gen all stores into byArr are assumed to be storing to a boolean array. BoolArrayStoreTransformer truncates the store to 1-bit with iand (n163n)

n87n      bstorei  <array-shadow>[#226  Shadow] [flags 0x80000601 0x0 ]                    
n86n        aladd (internalPtr sharedMemory )                                              
n64n          ==>aload
n85n          ladd                                                                         
n84n            i2l (X>=0 )                                                                
n65n              ==>iload
n83n            lconst 16                                                                  
n164n       i2b                                                                            
n163n         iand                                                                         
n162n           b2i                                                                        
n79n              i2b                                                                      
n78n                b2i                                                                    
n77n                  i2b                                                                  
n76n                    isub                                                               
n74n                      b2i                                                              
n73n                        bloadi  <array-shadow>[#226  Shadow] [flags 0x80000601 0x0 ]   
n72n                          aladd (internalPtr sharedMemory )                            
n64n                            ==>aload
n71n                            ladd                                                       
n70n                              i2l (X>=0 )                                              
n65n                                ==>iload
n69n                              lconst 16                                                
n75n                      iload  <auto slot 4>[#392  Auto] [flags 0x3 0x0 ]                
n161n           iconst 1                                                                   

[0xdaryl]

The fix won't have enough soaking time before I am confident to commit it to 0.33 at this stage. This is not a regression, so moving this out to 0.34. @pshipton