//
// The LLVM Compiler Infrastructure
//
-// This file was developed by the LLVM research group and is distributed under
-// the University of Illinois Open Source License. See LICENSE.TXT for details.
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
//===----------------------------------------------------------------------===//
#include "llvm/CodeGen/Passes.h"
-#include "llvm/Constant.h"
-#include "llvm/Instructions.h"
-#include "llvm/Function.h"
-#include "llvm/Pass.h"
-#include "llvm/Type.h"
-#include "llvm/Support/CFG.h"
-#include "llvm/Support/Compiler.h"
#include "llvm/ADT/DepthFirstIterator.h"
+#include "llvm/ADT/SmallPtrSet.h"
+#include "llvm/CodeGen/MachineDominators.h"
+#include "llvm/CodeGen/MachineFunctionPass.h"
+#include "llvm/CodeGen/MachineLoopInfo.h"
+#include "llvm/CodeGen/MachineModuleInfo.h"
+#include "llvm/CodeGen/MachineRegisterInfo.h"
+#include "llvm/IR/CFG.h"
+#include "llvm/IR/Constant.h"
+#include "llvm/IR/Dominators.h"
+#include "llvm/IR/Function.h"
+#include "llvm/IR/Instructions.h"
+#include "llvm/IR/Type.h"
+#include "llvm/Pass.h"
+#include "llvm/Target/TargetInstrInfo.h"
using namespace llvm;
namespace {
- class VISIBILITY_HIDDEN UnreachableBlockElim : public FunctionPass {
- virtual bool runOnFunction(Function &F);
+ class UnreachableBlockElim : public FunctionPass {
+ bool runOnFunction(Function &F) override;
+ public:
+ static char ID; // Pass identification, replacement for typeid
+ UnreachableBlockElim() : FunctionPass(ID) {
+ initializeUnreachableBlockElimPass(*PassRegistry::getPassRegistry());
+ }
+
+ void getAnalysisUsage(AnalysisUsage &AU) const override {
+ AU.addPreserved<DominatorTreeWrapperPass>();
+ }
};
- RegisterOpt<UnreachableBlockElim>
- X("unreachableblockelim", "Remove unreachable blocks from the CFG");
}
+char UnreachableBlockElim::ID = 0;
+INITIALIZE_PASS(UnreachableBlockElim, "unreachableblockelim",
+ "Remove unreachable blocks from the CFG", false, false)
FunctionPass *llvm::createUnreachableBlockEliminationPass() {
return new UnreachableBlockElim();
}
bool UnreachableBlockElim::runOnFunction(Function &F) {
- std::set<BasicBlock*> Reachable;
+ SmallPtrSet<BasicBlock*, 8> Reachable;
// Mark all reachable blocks.
- for (df_ext_iterator<Function*> I = df_ext_begin(&F, Reachable),
- E = df_ext_end(&F, Reachable); I != E; ++I)
- /* Mark all reachable blocks */;
+ for (BasicBlock *BB : depth_first_ext(&F, Reachable))
+ (void)BB/* Mark all reachable blocks */;
// Loop over all dead blocks, remembering them and deleting all instructions
// in them.
std::vector<BasicBlock*> DeadBlocks;
for (Function::iterator I = F.begin(), E = F.end(); I != E; ++I)
- if (!Reachable.count(I)) {
- BasicBlock *BB = I;
+ if (!Reachable.count(&*I)) {
+ BasicBlock *BB = &*I;
DeadBlocks.push_back(BB);
while (PHINode *PN = dyn_cast<PHINode>(BB->begin())) {
PN->replaceAllUsesWith(Constant::getNullValue(PN->getType()));
BB->dropAllReferences();
}
- if (DeadBlocks.empty()) return false;
+ // Actually remove the blocks now.
+ for (unsigned i = 0, e = DeadBlocks.size(); i != e; ++i) {
+ DeadBlocks[i]->eraseFromParent();
+ }
+
+ return !DeadBlocks.empty();
+}
+
+
+namespace {
+ class UnreachableMachineBlockElim : public MachineFunctionPass {
+ bool runOnMachineFunction(MachineFunction &F) override;
+ void getAnalysisUsage(AnalysisUsage &AU) const override;
+ MachineModuleInfo *MMI;
+ public:
+ static char ID; // Pass identification, replacement for typeid
+ UnreachableMachineBlockElim() : MachineFunctionPass(ID) {}
+ };
+}
+char UnreachableMachineBlockElim::ID = 0;
+
+INITIALIZE_PASS(UnreachableMachineBlockElim, "unreachable-mbb-elimination",
+ "Remove unreachable machine basic blocks", false, false)
+
+char &llvm::UnreachableMachineBlockElimID = UnreachableMachineBlockElim::ID;
+
+void UnreachableMachineBlockElim::getAnalysisUsage(AnalysisUsage &AU) const {
+ AU.addPreserved<MachineLoopInfo>();
+ AU.addPreserved<MachineDominatorTree>();
+ MachineFunctionPass::getAnalysisUsage(AU);
+}
+
+bool UnreachableMachineBlockElim::runOnMachineFunction(MachineFunction &F) {
+ SmallPtrSet<MachineBasicBlock*, 8> Reachable;
+ bool ModifiedPHI = false;
+
+ MMI = getAnalysisIfAvailable<MachineModuleInfo>();
+ MachineDominatorTree *MDT = getAnalysisIfAvailable<MachineDominatorTree>();
+ MachineLoopInfo *MLI = getAnalysisIfAvailable<MachineLoopInfo>();
+
+ // Mark all reachable blocks.
+ for (MachineBasicBlock *BB : depth_first_ext(&F, Reachable))
+ (void)BB/* Mark all reachable blocks */;
+
+ // Loop over all dead blocks, remembering them and deleting all instructions
+ // in them.
+ std::vector<MachineBasicBlock*> DeadBlocks;
+ for (MachineFunction::iterator I = F.begin(), E = F.end(); I != E; ++I) {
+ MachineBasicBlock *BB = &*I;
+
+ // Test for deadness.
+ if (!Reachable.count(BB)) {
+ DeadBlocks.push_back(BB);
+
+ // Update dominator and loop info.
+ if (MLI) MLI->removeBlock(BB);
+ if (MDT && MDT->getNode(BB)) MDT->eraseNode(BB);
+
+ while (BB->succ_begin() != BB->succ_end()) {
+ MachineBasicBlock* succ = *BB->succ_begin();
+
+ MachineBasicBlock::iterator start = succ->begin();
+ while (start != succ->end() && start->isPHI()) {
+ for (unsigned i = start->getNumOperands() - 1; i >= 2; i-=2)
+ if (start->getOperand(i).isMBB() &&
+ start->getOperand(i).getMBB() == BB) {
+ start->RemoveOperand(i);
+ start->RemoveOperand(i-1);
+ }
+
+ start++;
+ }
+
+ BB->removeSuccessor(BB->succ_begin());
+ }
+ }
+ }
// Actually remove the blocks now.
for (unsigned i = 0, e = DeadBlocks.size(); i != e; ++i)
- F.getBasicBlockList().erase(DeadBlocks[i]);
+ DeadBlocks[i]->eraseFromParent();
+
+ // Cleanup PHI nodes.
+ for (MachineFunction::iterator I = F.begin(), E = F.end(); I != E; ++I) {
+ MachineBasicBlock *BB = &*I;
+ // Prune unneeded PHI entries.
+ SmallPtrSet<MachineBasicBlock*, 8> preds(BB->pred_begin(),
+ BB->pred_end());
+ MachineBasicBlock::iterator phi = BB->begin();
+ while (phi != BB->end() && phi->isPHI()) {
+ for (unsigned i = phi->getNumOperands() - 1; i >= 2; i-=2)
+ if (!preds.count(phi->getOperand(i).getMBB())) {
+ phi->RemoveOperand(i);
+ phi->RemoveOperand(i-1);
+ ModifiedPHI = true;
+ }
+
+ if (phi->getNumOperands() == 3) {
+ unsigned Input = phi->getOperand(1).getReg();
+ unsigned Output = phi->getOperand(0).getReg();
+
+ MachineInstr* temp = phi;
+ ++phi;
+ temp->eraseFromParent();
+ ModifiedPHI = true;
+
+ if (Input != Output) {
+ MachineRegisterInfo &MRI = F.getRegInfo();
+ MRI.constrainRegClass(Input, MRI.getRegClass(Output));
+ MRI.replaceRegWith(Output, Input);
+ }
+
+ continue;
+ }
+
+ ++phi;
+ }
+ }
+
+ F.RenumberBlocks();
- return true;
+ return (!DeadBlocks.empty() || ModifiedPHI);
}
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