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From "Cheng, BuQi (JIRA)" <j...@apache.org>
Subject [jira] Created: (HARMONY-5996) [HARMONY][JIT][OPTIMIZER] Assumption in array base address load asscoiated symbolic analysis of dabce caused bug
Date Sat, 11 Oct 2008 18:51:44 GMT
[HARMONY][JIT][OPTIMIZER] Assumption in array base address load asscoiated symbolic analysis
of dabce caused bug
----------------------------------------------------------------------------------------------------------------

                 Key: HARMONY-5996
                 URL: https://issues.apache.org/jira/browse/HARMONY-5996
             Project: Harmony
          Issue Type: Bug
         Environment: Windows
            Reporter: Cheng, BuQi
            Priority: Critical


In function code:
void DynamicABCE::fillTemplate(ArrayAccessTemplate* arrayAccess, Inst* checkInst) {
....
    Node* node = checkInst->getNode()->getUnconditionalEdgeTarget();
    for (Inst* inst = (Inst*)node->getFirstInst(); inst != NULL; inst = inst->getNextInst())
{
...
        } else if (opcode == Op_AddScaledIndex &&
            arrayAccess->index == inst->getSrc(1) && arrayAccess->array ==
NULL) {
            assert(ldBaseInst == NULL);
            ldBaseInst = inst->getSrc(0)->asSsaOpnd()->getInst();
            assert(ldBaseInst->getOpcode() == Op_LdArrayBaseAddr);
            arrayAccess->array = ldBaseInst->getSrc(0)->asSsaOpnd();
            break;
        }
    }
...
}

The code "assert(ldBaseInst->getOpcode() == Op_LdArrayBaseAddr);" assumes that after bound
checking, the direct target block will access array immediately, and  the array access instruction
in it will use "Op_LdArrayBaseAddr" instruction to access the array base. However, this kind
assumption is very tender.

In server: scimark.sor.small. 
After loop peeling,  phi instruction is generated for LDBASE instruction, this time LDVAR
instruction will be used to get the variable from Phi. The assertion will fail and bug will
happen. 

There may be two kind solutions:
1.  In IR building, record the array access information. 
2.  Or more accurate symbolic is used to find the array base load instruction.


Thanks!

Buqi



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