[webkit-dev] MIPS port problem - cti_op_put_by_id slow case problem

Toshiyasu Morita tm_webkit at yahoo.com
Tue Jun 16 16:53:48 PDT 2009

I've gotten the MIPS port up to where it can compile and execute through about 9 functions of a testcase before it crashes.

The reason for the crash appears to be related to op_put_by_id. When this opcode is compiled, the JIT executes:

void JIT::compilePutByIdSlowCase(int baseVReg, Identifier* ident, int, Vector<SlowCaseEntry>::iterator& iter, unsigned propertyAccessInstructionIndex)
    linkSlowCaseIfNotJSCell(iter, baseVReg);

    emitPutJITStubArgConstant(ident, 2);
    emitPutJITStubArg(regT0, 1);
    emitPutJITStubArg(regT1, 3);
    Call call = emitCTICall(JITStubs::cti_op_put_by_id);

    // Track the location of the call; this will be used to recover patch information.
    m_propertyAccessCompilationInfo[propertyAccessInstructionIndex].callReturnLocation = call;

When the code is initially generated, it generates a call to address 0x6a2294 (JIT::cti_op_put_by_id) which is correct. Later on, something modifies the instruction to call address 0x6a26dc instead, which causes an infinite loop.

What is the purpose of dynamically modifying this call instruction?


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