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https://github.com/c64scene-ar/llvm-6502.git
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Make RewriteLoopExitValues far less nested by using continue in the loop
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@34891 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner
parent
a9569f10de
commit
c9838f25d5
@ -322,102 +322,105 @@ void IndVarSimplify::RewriteLoopExitValues(Loop *L) {
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std::set<Instruction*> InstructionsToDelete;
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for (unsigned i = 0, e = L->getBlocks().size(); i != e; ++i)
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if (LI->getLoopFor(L->getBlocks()[i]) == L) { // Not in a subloop...
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BasicBlock *BB = L->getBlocks()[i];
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for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E;) {
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if (I->getType()->isInteger()) { // Is an integer instruction
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SCEVHandle SH = SE->getSCEV(I);
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if (SH->hasComputableLoopEvolution(L) || // Varies predictably
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HasConstantItCount) {
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// Find out if this predictably varying value is actually used
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// outside of the loop. "extra" as opposed to "intra".
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std::vector<Instruction*> ExtraLoopUsers;
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for (Value::use_iterator UI = I->use_begin(), E = I->use_end();
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UI != E; ++UI) {
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Instruction *User = cast<Instruction>(*UI);
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if (!L->contains(User->getParent())) {
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// If this is a PHI node in the exit block and we're inserting,
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// into the exit block, it must have a single entry. In this
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// case, we can't insert the code after the PHI and have the PHI
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// still use it. Instead, don't insert the the PHI.
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if (PHINode *PN = dyn_cast<PHINode>(User)) {
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// FIXME: This is a case where LCSSA pessimizes code, this
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// should be fixed better.
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if (PN->getNumOperands() == 2 &&
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PN->getParent() == BlockToInsertInto)
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continue;
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}
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ExtraLoopUsers.push_back(User);
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}
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}
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if (!ExtraLoopUsers.empty()) {
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// Okay, this instruction has a user outside of the current loop
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// and varies predictably in this loop. Evaluate the value it
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// contains when the loop exits, and insert code for it.
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SCEVHandle ExitValue = SE->getSCEVAtScope(I, L->getParentLoop());
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if (!isa<SCEVCouldNotCompute>(ExitValue)) {
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Changed = true;
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++NumReplaced;
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// Remember the next instruction. The rewriter can move code
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// around in some cases.
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BasicBlock::iterator NextI = I; ++NextI;
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Value *NewVal = Rewriter.expandCodeFor(ExitValue, InsertPt,
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I->getType());
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DOUT << "INDVARS: RLEV: AfterLoopVal = " << *NewVal
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<< " LoopVal = " << *I << "\n";
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// Rewrite any users of the computed value outside of the loop
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// with the newly computed value.
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for (unsigned i = 0, e = ExtraLoopUsers.size(); i != e; ++i) {
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PHINode* PN = dyn_cast<PHINode>(ExtraLoopUsers[i]);
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if (PN && PN->getNumOperands() == 2 &&
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!L->contains(PN->getParent())) {
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// We're dealing with an LCSSA Phi. Handle it specially.
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Instruction* LCSSAInsertPt = BlockToInsertInto->begin();
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Instruction* NewInstr = dyn_cast<Instruction>(NewVal);
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if (NewInstr && !isa<PHINode>(NewInstr) &&
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!L->contains(NewInstr->getParent()))
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for (unsigned j = 0; j < NewInstr->getNumOperands(); ++j){
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Instruction* PredI =
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dyn_cast<Instruction>(NewInstr->getOperand(j));
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if (PredI && L->contains(PredI->getParent())) {
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PHINode* NewLCSSA = new PHINode(PredI->getType(),
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PredI->getName() + ".lcssa",
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LCSSAInsertPt);
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NewLCSSA->addIncoming(PredI,
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BlockToInsertInto->getSinglePredecessor());
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NewInstr->replaceUsesOfWith(PredI, NewLCSSA);
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}
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}
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PN->replaceAllUsesWith(NewVal);
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PN->eraseFromParent();
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} else {
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ExtraLoopUsers[i]->replaceUsesOfWith(I, NewVal);
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}
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}
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// If this instruction is dead now, schedule it to be removed.
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if (I->use_empty())
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InstructionsToDelete.insert(I);
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I = NextI;
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continue; // Skip the ++I
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}
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}
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}
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}
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// Next instruction. Continue instruction skips this.
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++I;
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// Loop over all of the integer-valued instructions in this loop, but that are
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// not in a subloop.
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for (unsigned i = 0, e = L->getBlocks().size(); i != e; ++i) {
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if (LI->getLoopFor(L->getBlocks()[i]) != L)
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continue; // The Block is in a subloop, skip it.
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BasicBlock *BB = L->getBlocks()[i];
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for (BasicBlock::iterator II = BB->begin(), E = BB->end(); II != E; ) {
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Instruction *I = II++;
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if (!I->getType()->isInteger())
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continue; // SCEV only supports integer expressions for now.
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SCEVHandle SH = SE->getSCEV(I);
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if (!HasConstantItCount &&
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!SH->hasComputableLoopEvolution(L)) { // Varies predictably
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continue; // Cannot exit evolution for the loop value.
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}
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}
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// Find out if this predictably varying value is actually used
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// outside of the loop. "Extra" is as opposed to "intra".
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std::vector<Instruction*> ExtraLoopUsers;
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for (Value::use_iterator UI = I->use_begin(), E = I->use_end();
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UI != E; ++UI) {
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Instruction *User = cast<Instruction>(*UI);
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if (!L->contains(User->getParent())) {
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// If this is a PHI node in the exit block and we're inserting,
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// into the exit block, it must have a single entry. In this
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// case, we can't insert the code after the PHI and have the PHI
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// still use it. Instead, don't insert the the PHI.
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if (PHINode *PN = dyn_cast<PHINode>(User)) {
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// FIXME: This is a case where LCSSA pessimizes code, this
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// should be fixed better.
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if (PN->getNumOperands() == 2 &&
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PN->getParent() == BlockToInsertInto)
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continue;
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}
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ExtraLoopUsers.push_back(User);
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}
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}
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// If nothing outside the loop uses this value, don't rewrite it.
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if (ExtraLoopUsers.empty())
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continue;
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// Okay, this instruction has a user outside of the current loop
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// and varies predictably *inside* the loop. Evaluate the value it
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// contains when the loop exits if possible.
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SCEVHandle ExitValue = SE->getSCEVAtScope(I, L->getParentLoop());
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if (isa<SCEVCouldNotCompute>(ExitValue))
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continue;
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Changed = true;
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++NumReplaced;
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Value *NewVal = Rewriter.expandCodeFor(ExitValue, InsertPt,
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I->getType());
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DOUT << "INDVARS: RLEV: AfterLoopVal = " << *NewVal
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<< " LoopVal = " << *I << "\n";
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// Rewrite any users of the computed value outside of the loop
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// with the newly computed value.
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for (unsigned i = 0, e = ExtraLoopUsers.size(); i != e; ++i) {
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PHINode* PN = dyn_cast<PHINode>(ExtraLoopUsers[i]);
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if (PN && PN->getNumOperands() == 2 &&
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!L->contains(PN->getParent())) {
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// We're dealing with an LCSSA Phi. Handle it specially.
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Instruction* LCSSAInsertPt = BlockToInsertInto->begin();
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Instruction* NewInstr = dyn_cast<Instruction>(NewVal);
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if (NewInstr && !isa<PHINode>(NewInstr) &&
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!L->contains(NewInstr->getParent()))
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for (unsigned j = 0; j != NewInstr->getNumOperands(); ++j) {
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Instruction* PredI =
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dyn_cast<Instruction>(NewInstr->getOperand(j));
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if (PredI && L->contains(PredI->getParent())) {
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PHINode* NewLCSSA = new PHINode(PredI->getType(),
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PredI->getName() + ".lcssa",
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LCSSAInsertPt);
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NewLCSSA->addIncoming(PredI,
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BlockToInsertInto->getSinglePredecessor());
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NewInstr->replaceUsesOfWith(PredI, NewLCSSA);
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}
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}
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PN->replaceAllUsesWith(NewVal);
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PN->eraseFromParent();
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} else {
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ExtraLoopUsers[i]->replaceUsesOfWith(I, NewVal);
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}
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}
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// If this instruction is dead now, schedule it to be removed.
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if (I->use_empty())
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InstructionsToDelete.insert(I);
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}
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}
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DeleteTriviallyDeadInstructions(InstructionsToDelete);
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}
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