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https://github.com/c64scene-ar/llvm-6502.git
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isImmediate(), isRegister(), and friends, to avoid confusion about having two different names with the same meaning. I'm not attached to the longer names, and would be ok with changing to the shorter names if others prefer it. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@56189 91177308-0d34-0410-b5e6-96231b3b80d8
186 lines
6.1 KiB
C++
186 lines
6.1 KiB
C++
//===-- UnreachableBlockElim.cpp - Remove unreachable blocks for codegen --===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This pass is an extremely simple version of the SimplifyCFG pass. Its sole
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// job is to delete LLVM basic blocks that are not reachable from the entry
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// node. To do this, it performs a simple depth first traversal of the CFG,
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// then deletes any unvisited nodes.
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//
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// Note that this pass is really a hack. In particular, the instruction
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// selectors for various targets should just not generate code for unreachable
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// blocks. Until LLVM has a more systematic way of defining instruction
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// selectors, however, we cannot really expect them to handle additional
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// complexity.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/CodeGen/Passes.h"
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#include "llvm/Constant.h"
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#include "llvm/Instructions.h"
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#include "llvm/Function.h"
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#include "llvm/Pass.h"
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#include "llvm/Type.h"
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#include "llvm/CodeGen/MachineFunctionPass.h"
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#include "llvm/CodeGen/MachineRegisterInfo.h"
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#include "llvm/Support/CFG.h"
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#include "llvm/Support/Compiler.h"
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#include "llvm/Target/TargetInstrInfo.h"
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#include "llvm/ADT/DepthFirstIterator.h"
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#include "llvm/ADT/SmallPtrSet.h"
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using namespace llvm;
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namespace {
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class VISIBILITY_HIDDEN UnreachableBlockElim : public FunctionPass {
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virtual bool runOnFunction(Function &F);
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public:
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static char ID; // Pass identification, replacement for typeid
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UnreachableBlockElim() : FunctionPass(&ID) {}
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};
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}
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char UnreachableBlockElim::ID = 0;
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static RegisterPass<UnreachableBlockElim>
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X("unreachableblockelim", "Remove unreachable blocks from the CFG");
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FunctionPass *llvm::createUnreachableBlockEliminationPass() {
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return new UnreachableBlockElim();
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}
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bool UnreachableBlockElim::runOnFunction(Function &F) {
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SmallPtrSet<BasicBlock*, 8> Reachable;
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// Mark all reachable blocks.
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for (df_ext_iterator<Function*, SmallPtrSet<BasicBlock*, 8> > I =
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df_ext_begin(&F, Reachable), E = df_ext_end(&F, Reachable); I != E; ++I)
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/* Mark all reachable blocks */;
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// Loop over all dead blocks, remembering them and deleting all instructions
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// in them.
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std::vector<BasicBlock*> DeadBlocks;
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for (Function::iterator I = F.begin(), E = F.end(); I != E; ++I)
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if (!Reachable.count(I)) {
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BasicBlock *BB = I;
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DeadBlocks.push_back(BB);
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while (PHINode *PN = dyn_cast<PHINode>(BB->begin())) {
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PN->replaceAllUsesWith(Constant::getNullValue(PN->getType()));
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BB->getInstList().pop_front();
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}
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for (succ_iterator SI = succ_begin(BB), E = succ_end(BB); SI != E; ++SI)
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(*SI)->removePredecessor(BB);
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BB->dropAllReferences();
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}
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// Actually remove the blocks now.
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for (unsigned i = 0, e = DeadBlocks.size(); i != e; ++i)
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DeadBlocks[i]->eraseFromParent();
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return DeadBlocks.size();
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}
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namespace {
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class VISIBILITY_HIDDEN UnreachableMachineBlockElim :
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public MachineFunctionPass {
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virtual bool runOnMachineFunction(MachineFunction &F);
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public:
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static char ID; // Pass identification, replacement for typeid
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UnreachableMachineBlockElim() : MachineFunctionPass(&ID) {}
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};
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}
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char UnreachableMachineBlockElim::ID = 0;
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static RegisterPass<UnreachableMachineBlockElim>
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Y("unreachable-mbb-elimination",
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"Remove unreachable machine basic blocks");
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const PassInfo *const llvm::UnreachableMachineBlockElimID = &Y;
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bool UnreachableMachineBlockElim::runOnMachineFunction(MachineFunction &F) {
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SmallPtrSet<MachineBasicBlock*, 8> Reachable;
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// Mark all reachable blocks.
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for (df_ext_iterator<MachineFunction*, SmallPtrSet<MachineBasicBlock*, 8> >
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I = df_ext_begin(&F, Reachable), E = df_ext_end(&F, Reachable);
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I != E; ++I)
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/* Mark all reachable blocks */;
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// Loop over all dead blocks, remembering them and deleting all instructions
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// in them.
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std::vector<MachineBasicBlock*> DeadBlocks;
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for (MachineFunction::iterator I = F.begin(), E = F.end(); I != E; ++I) {
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MachineBasicBlock *BB = I;
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// Test for deadness.
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if (!Reachable.count(BB)) {
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DeadBlocks.push_back(BB);
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while (BB->succ_begin() != BB->succ_end()) {
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MachineBasicBlock* succ = *BB->succ_begin();
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MachineBasicBlock::iterator start = succ->begin();
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while (start != succ->end() &&
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start->getOpcode() == TargetInstrInfo::PHI) {
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for (unsigned i = start->getNumOperands() - 1; i >= 2; i-=2)
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if (start->getOperand(i).isMachineBasicBlock() &&
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start->getOperand(i).getMBB() == BB) {
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start->RemoveOperand(i);
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start->RemoveOperand(i-1);
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}
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start++;
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}
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BB->removeSuccessor(BB->succ_begin());
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}
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}
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}
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// Actually remove the blocks now.
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for (unsigned i = 0, e = DeadBlocks.size(); i != e; ++i)
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DeadBlocks[i]->eraseFromParent();
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// Cleanup PHI nodes.
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for (MachineFunction::iterator I = F.begin(), E = F.end(); I != E; ++I) {
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MachineBasicBlock *BB = I;
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// Prune unneeded PHI entries.
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SmallPtrSet<MachineBasicBlock*, 8> preds(BB->pred_begin(),
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BB->pred_end());
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MachineBasicBlock::iterator phi = BB->begin();
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while (phi != BB->end() &&
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phi->getOpcode() == TargetInstrInfo::PHI) {
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for (unsigned i = phi->getNumOperands() - 1; i >= 2; i-=2)
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if (!preds.count(phi->getOperand(i).getMBB())) {
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phi->RemoveOperand(i);
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phi->RemoveOperand(i-1);
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}
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if (phi->getNumOperands() == 3) {
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unsigned Input = phi->getOperand(1).getReg();
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unsigned Output = phi->getOperand(0).getReg();
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MachineInstr* temp = phi;
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++phi;
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temp->eraseFromParent();
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if (Input != Output)
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F.getRegInfo().replaceRegWith(Output, Input);
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continue;
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}
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++phi;
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}
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}
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F.RenumberBlocks();
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return DeadBlocks.size();
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}
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