X-Git-Url: http://plrg.eecs.uci.edu/git/?a=blobdiff_plain;ds=sidebyside;f=lib%2FCodeGen%2FUnreachableBlockElim.cpp;h=7824f92185755e9c7241b545c1d9b9e879cd4f4e;hb=b78fd035a230c05e5cb6a7e0afdd3cbf7b3e9239;hp=f66a7713d7f97798dfba2dfe76fd8b95bef1f550;hpb=794fd75c67a2cdc128d67342c6d88a504d186896;p=oota-llvm.git

diff --git a/lib/CodeGen/UnreachableBlockElim.cpp b/lib/CodeGen/UnreachableBlockElim.cpp
index f66a7713d7f..7824f921857 100644
--- a/lib/CodeGen/UnreachableBlockElim.cpp
+++ b/lib/CodeGen/UnreachableBlockElim.cpp
@@ -2,8 +2,8 @@
 //
 //                     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.
 //
 //===----------------------------------------------------------------------===//
 //
@@ -21,39 +21,51 @@
 //===----------------------------------------------------------------------===//
 
 #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 const int ID; // Pass identifcation, replacement for typeid
-    UnreachableBlockElim() : FunctionPass((intptr_t)&ID) {}
+    static char ID; // Pass identification, replacement for typeid
+    UnreachableBlockElim() : FunctionPass(ID) {
+      initializeUnreachableBlockElimPass(*PassRegistry::getPassRegistry());
+    }
+
+    void getAnalysisUsage(AnalysisUsage &AU) const override {
+      AU.addPreserved<DominatorTreeWrapperPass>();
+    }
   };
-  const int UnreachableBlockElim::ID = 0;
-  RegisterPass<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.
@@ -71,11 +83,126 @@ bool UnreachableBlockElim::runOnFunction(Function &F) {
       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.size();
+}
+
+
+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.size() || ModifiedPHI);
 }