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Export ConstantFoldTerminator, allow it to fold conditional branches to
the same label. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@107 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -120,28 +120,50 @@ ConstantFoldBinaryInst(Method *M, Method::inst_iterator &DI,
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return true;
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}
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inline static bool ConstantFoldTerminator(TerminatorInst *T) {
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// ConstantFoldTerminator - If a terminator instruction is predicated on a
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// constant value, convert it into an unconditional branch to the constant
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// destination.
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//
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bool ConstantFoldTerminator(TerminatorInst *T) {
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// Branch - See if we are conditional jumping on constant
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if (T->getInstType() == Instruction::Br) {
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BranchInst *BI = (BranchInst*)T;
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if (!BI->isUnconditional() && // Are we branching on constant?
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BI->getOperand(2)->isConstant()) {
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if (BI->isUnconditional()) return false; // Can't optimize uncond branch
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BasicBlock *Dest1 = BI->getOperand(0)->castBasicBlockAsserting();
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BasicBlock *Dest2 = BI->getOperand(1)->castBasicBlockAsserting();
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if (BI->getOperand(2)->isConstant()) { // Are we branching on constant?
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// YES. Change to unconditional branch...
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ConstPoolBool *Cond = (ConstPoolBool*)BI->getOperand(2);
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Value *Destination = BI->getOperand(Cond->getValue() ? 0 : 1);
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Value *OldDest = BI->getOperand(Cond->getValue() ? 1 : 0);
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BasicBlock *Destination = Cond->getValue() ? Dest1 : Dest2;
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BasicBlock *OldDest = Cond->getValue() ? Dest2 : Dest1;
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//cerr << "Method: " << T->getParent()->getParent() << "\nRemoving branch from " << T->getParent() << "\n\nTo: " << OldDest << endl;
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//cerr << "Method: " << T->getParent()->getParent()
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// << "\nRemoving branch from " << T->getParent()
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// << "\n\nTo: " << OldDest << endl;
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// Let the basic block know that we are letting go of it. Based on this,
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// it will adjust it's PHI nodes.
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assert(T->getParent() && "Terminator not inserted in block!");
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OldDest->castBasicBlockAsserting()->removePredecessor(T->getParent());
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assert(BI->getParent() && "Terminator not inserted in block!");
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OldDest->removePredecessor(BI->getParent());
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BI->setOperand(0, Destination); // Set the unconditional destination
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BI->setOperand(1, 0); // Clear the conditional destination
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BI->setOperand(2, 0); // Clear the condition...
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return true;
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} else if (Dest2 == Dest1) { // Conditional branch to same location?
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// This branch matches something like this:
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// br bool %cond, label %Dest, label %Dest
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// and changes it into: br label %Dest
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// Let the basic block know that we are letting go of one copy of it.
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assert(BI->getParent() && "Terminator not inserted in block!");
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Dest1->removePredecessor(BI->getParent());
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// Nuke the second destination, and the use of the condition variable
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BI->setOperand(1, 0); // Clear the conditional destination
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BI->setOperand(2, 0); // Clear the condition...
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return true;
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}
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}
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return false;
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