ExceptionRegion modeling issues and proposed improvements

[Adam Sotona]

I would rather describe actual situation on examples:

1. The simplest example seamlessly matching current model:
try { // enter the top region
    try { // enter the nested region

    }  // leave the nested region
    catch { // handler implicitly a part of the top region
        // here is the nested handler code
    }
} // leave the top region
catch { // handler outside of any regions
// here is the top handler code
}

2. Example with split (the same as above, just with added gap in the middle)
try { // enter the top region part 1
    try { // enter the nested region part 1

    } catch { // handler implicitly a part of the top region part 1
              // we need to leave the top region part 1
              // and we cannot jump to the handler in the other top region part
              // so we jump to a synthetic isolated nested region exception handler
   }
} // split - leave the top region part 1
catch { // handler outside of any regions
    // jump to common top region handler
}

... gap in the regions (may be a single instruction excluded from the exception regions)

try { // enter the top region part 2
    try { // enter the nested region part 2

    }  // leave the nested region part 2
    catch { // handler implicitly a part of the top region part 2
            // we need to leave the top region part 2
            // and jump to a synthetic isolated nested region exception handler
    }
} // leave the top region part 2
catch { // handler outside of any regions
    // jump to common top region handler
}

// synthetic nested region handler
try { // enter the top region part 3
    // here is the nested handler code
 } // leave the top region part 3
catch { // common top region handler outside of any regions
// here is the common top handler code
}

3. And now add third level, jumps between the region fragments and jumps out of the regions (for example break or continue)... ;)



From: Maurizio Cimadamore <maurizio.cimadamore at oracle.com>
Date: Wednesday, 9 October 2024 at 15:55
To: Adam Sotona <adam.sotona at oracle.com>, babylon-dev at openjdk.org <babylon-dev at openjdk.org>
Subject: Re: ExceptionRegion modeling issues and proposed improvements


On 09/10/2024 14:16, Adam Sotona wrote:

If we wanted to exit the region from block 27, then we'd also need to split, as we might need to exit either %1 or %5 from there, no?

block 27 is the exception handler of the outer try region(s), so no need to exit it (them)

Maybe this is the bit I'm missing: don't we need to exit exception regions explicitly, even inside catch handlers?

Maurizio
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