Examples with StackInstruction org.apache.bcel.generic.StackInstruction used on opensource projects

Example 1 with StackInstruction

use of org.apache.bcel.generic.StackInstruction in project jop by jop-devel.

the class SimpleInliner method analyzeInvokee.

/**
 * @param cs the callstring from the invoker to the invoke to inline (if recursive). Used to check DFA results.
 * @param invokee the invoked method to analyze
 * @param inlineData the map to populate with the parameters and the instructions to inline.
 * @return true if inlining is possible
 */
private boolean analyzeInvokee(CallString cs, MethodInfo invokee, InlineData inlineData) {
    // we allow loading of parameters, loading of constants, some instruction, and a return
    ValueMapAnalysis values = new ValueMapAnalysis(invokee);
    values.loadParameters();
    InstructionList il = invokee.getCode().getInstructionList(true, false);
    InstructionHandle ih = il.getStart();
    // we should at least have a return instruction, so even for empty methods we should fall through
    // generate the parameter mapping
    int count = 0;
    while (true) {
        Instruction instruction = ih.getInstruction();
        if (instruction instanceof PushInstruction || instruction instanceof NOP) {
            values.transfer(instruction);
            ih = ih.getNext();
            count++;
        } else {
            break;
        }
    }
    // store the mapping
    for (ValueInfo value : values.getValueTable().getStack()) {
        inlineData.addParam(value);
    }
    inlineData.setInlineStart(count);
    // if we do not need an NP check, we can also inline code which does not throw an exception in the same way
    boolean needsNPCheck = helper.needsNullpointerCheck(cs, invokee, false);
    boolean hasNPCheck = false;
    // we allow up to 5 instructions and one return before assuming that the resulting code will be too large
    for (int i = 0; i < 6; i++) {
        // now lets see what we have here as non-push instructions
        Instruction instruction = ih.getInstruction();
        if (instruction instanceof InvokeInstruction) {
            if (inlineData.getInvokeSite() != null) {
                // only inline at most one invoke
                return false;
            }
            InvokeSite is = invokee.getCode().getInvokeSite(ih);
            inlineData.setInvokeSite(is);
            hasNPCheck |= !is.isInvokeStatic();
        } else if (instruction instanceof FieldInstruction) {
            if (instruction instanceof GETFIELD) {
                hasNPCheck |= values.getValueTable().top().isThisReference();
            }
            if (instruction instanceof PUTFIELD) {
                int down = values.getValueTable().top().isContinued() ? 2 : 1;
                hasNPCheck |= values.getValueTable().top(down).isThisReference();
            }
        } else if (instruction instanceof ArithmeticInstruction || instruction instanceof ConversionInstruction || instruction instanceof StackInstruction || instruction instanceof LDC || instruction instanceof LDC2_W || instruction instanceof ARRAYLENGTH || instruction instanceof CHECKCAST || instruction instanceof NOP) {
        // nothing to do, just copy them
        } else if (instruction instanceof ReturnInstruction) {
            if (needsNPCheck && !hasNPCheck) {
                // We were nearly finished.. but NP check test failed
                this.requiresNPCheck++;
                if (logger.isTraceEnabled()) {
                    logger.trace("Not inlining " + invokee + " because it requires a NP check.");
                }
                return false;
            }
            // else we need to add pop instructions
            if (instruction instanceof RETURN) {
                // we do not return anything, so we must empty the stack
                while (values.getValueTable().getStackSize() > 0) {
                    Instruction pop;
                    if (values.getValueTable().top().isContinued()) {
                        pop = new POP2();
                    } else {
                        pop = new POP();
                    }
                    inlineData.addEpilogue(pop);
                    values.transfer(pop);
                }
                return true;
            } else {
                Type type = ((ReturnInstruction) instruction).getType();
                // javac anyway)
                return values.getValueTable().getStackSize() == type.getSize();
            }
        } else {
            // if we encounter an instruction which we do not handle, we do not inline
            unhandledInstructions++;
            if (logger.isTraceEnabled()) {
                logger.trace("Not inlining " + invokee + " because of unhandled instruction " + instruction.toString(invokee.getClassInfo().getConstantPoolGen().getConstantPool()));
            }
            return false;
        }
        // update the stack map since we need it to handle RETURN
        values.transfer(instruction);
        ih = ih.getNext();
    }
    // too many instructions, do not inline
    return false;
}