C++ PBB::getPrevStmt方法代码示例

//.........这里部分代码省略.........
				// modifications. This is necessary because we do several passes of this algorithm to sort out the
				// memory expressions
				Stacks[a->clone()].push(S);
				// Replace definition of a with definition of a_i in S (we don't do this)
			}
			// FIXME: MVE: do we need this awful hack?
			if (a->getOper() == opLocal) {
				Exp *a1 = S->getProc()->expFromSymbol(((Const*)a->getSubExp1())->getStr());
				assert(a1);
				a = a1;
				// Stacks already has a definition for a (as just the bare local)
				if (suitable) {
					Stacks[a->clone()].push(S);
				}
			}
		}
		// Special processing for define-alls (presently, only childless calls).
// But note that only everythings at the current memory level are defined!
		if (S->isCall() && ((CallStatement*)S)->isChildless() && !Boomerang::get()->assumeABI) {
			// S is a childless call (and we're not assuming ABI compliance)
			Stacks[defineAll];										// Ensure that there is an entry for defineAll
			std::map<Exp*, std::stack<Statement*>, lessExpStar>::iterator dd;
			for (dd = Stacks.begin(); dd != Stacks.end(); ++dd) {
// if (dd->first->isMemDepth(memDepth))
					dd->second.push(S);								// Add a definition for all vars
			}
		}
	}

	// For each successor Y of block n
	std::vector<PBB>& outEdges = bb->getOutEdges();
	unsigned numSucc = outEdges.size();
	for (unsigned succ = 0; succ < numSucc; succ++) {
		PBB Ybb = outEdges[succ];
		// Suppose n is the jth predecessor of Y
		int j = Ybb->whichPred(bb);
		// For each phi-function in Y
		Statement* S;
		for (S = Ybb->getFirstStmt(rit, sit); S; S = Ybb->getNextStmt(rit, sit)) {
			PhiAssign* pa = dynamic_cast<PhiAssign*>(S);
			// if S is not a phi function, then quit the loop (no more phi's)
			// Wrong: do not quit the loop: there's an optimisation that turns a PhiAssign into an ordinary Assign.
			// So continue, not break.
			if (!pa) continue;
			// Suppose the jth operand of the phi is a
			// For now, just get the LHS
			Exp* a = pa->getLeft();
			// Only consider variables that can be renamed
			if (!canRename(a, proc)) continue;
			Statement* def;
			if (STACKS_EMPTY(a))
				def = NULL;				// No reaching definition
			else
				def = Stacks[a].top();
			// "Replace jth operand with a_i"
			pa->putAt(j, def, a);
		}
	}

	// For each child X of n
	// Note: linear search!
	unsigned numBB = proc->getCFG()->getNumBBs();
	for (unsigned X=0; X < numBB; X++) {
		if (idom[X] == n)
			renameBlockVars(proc, X);
	}

	// For each statement S in block n
	// NOTE: Because of the need to pop childless calls from the Stacks, it is important in my algorithm to process the
	// statments in the BB *backwards*. (It is not important in Appel's algorithm, since he always pushes a definition
	// for every variable defined on the Stacks).
	BasicBlock::rtlrit rrit; StatementList::reverse_iterator srit;
	for (S = bb->getLastStmt(rrit, srit); S; S = bb->getPrevStmt(rrit, srit)) {
		// For each definition of some variable a in S
		LocationSet defs;
		S->getDefinitions(defs);
		LocationSet::iterator dd;
		for (dd = defs.begin(); dd != defs.end(); dd++) {
			if (canRename(*dd, proc)) {
				// if ((*dd)->getMemDepth() == memDepth)
				std::map<Exp*, std::stack<Statement*>, lessExpStar>::iterator ss = Stacks.find(*dd);
				if (ss == Stacks.end()) {
					std::cerr << "Tried to pop " << *dd << " from Stacks; does not exist\n";
 					assert(0);
				}
					ss->second.pop();
			}
		}
		// Pop all defs due to childless calls
		if (S->isCall() && ((CallStatement*)S)->isChildless()) {
			std::map<Exp*, std::stack<Statement*>, lessExpStar>::iterator sss;
			for (sss = Stacks.begin(); sss != Stacks.end(); ++sss) {
				if (!sss->second.empty() && sss->second.top() == S) {
					sss->second.pop();
				}
			}
		}
	}
	return changed;
}