[15] RFR: 8242895: failed: sanity at src/hotspot/share/opto/escape.cpp:2361

[Jamsheed C M]

Hi all,

JBS:https://bugs.openjdk.java.net/browse/JDK-8242895

Request for review changes made to offset computation and field write 
detection for init captured stores due to phis addition between alloc 
and init. This happen if init node in different outer loop wrt to alloc 
node and there is a loop opt.  This was required as a result of 
enhancement [1].

Normally init are not associated with multiple alloc node during EA 
phase, but changes done for [1] caused the code shapes of the form [2]  
to generate inits associated with multiple alloc node.

This had implication in offset computation and field write detection 
related to initializing stores.

Attempt to fix in EA:

      webrev: http://cr.openjdk.java.net/~jcm/8242895/webrev_fix_EA/

Alternate fix:

      Minimize the scenario in compiler generated code by throwing only 
j.l.Error from slowpath(all exception async/sync are handled in runtime 
exit).

      Stub epilog doesn't poll or throw any exceptions. Disable full 
loop opt before EA for detectable patterns and bailout EA for late 
detected patterns.

      webrev: http://cr.openjdk.java.net/~jcm/8242895/webrev_deopt/

Please advice.

Testing : mach tier1-5 (logs in jbs)

Best regards,

Jamsheed


[1] JDK-8231291 <https://bugs.openjdk.java.net/browse/JDK-8231291>C2: 
loop opts before EA should maximally unroll loops

[2] that have its init node in different outer loop wrt to alloc node.


loop begin

    try{

    return new obj()/  throw new obj()/ uncommon trap after allocation, 
in a loop

    } catch(ex) {

    }

loop end

  42     public static IntA test(int n) {
   43         for (int i=0; i<2; i++) {
   44             try {
   45                   return new IntA(n + i);
   46             } catch (Exception e) {
   47             }
   48         }
   49