Add some advice

llvm-svn: 29324

1 files changed, 0 insertions, 237 deletions

diff --git a/llvm/lib/Transforms/Scalar/LowerSwitch.cpp b/llvm/lib/Transforms/Scalar/LowerSwitch.cpp
deleted file mode 100644
index 396b507bbd1..00000000000
--- a/llvm/lib/Transforms/Scalar/LowerSwitch.cpp
+++ /dev/null
@@ -1,237 +0,0 @@
-//===- LowerSwitch.cpp - Eliminate Switch instructions --------------------===//
-//
-//                     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.
-//
-//===----------------------------------------------------------------------===//
-//
-// The LowerSwitch transformation rewrites switch statements with a sequence of
-// branches, which allows targets to get away with not implementing the switch
-// statement until it is convenient.
-//
-//===----------------------------------------------------------------------===//
-
-#include "llvm/Transforms/Scalar.h"
-#include "llvm/Transforms/Utils/UnifyFunctionExitNodes.h"
-#include "llvm/Constants.h"
-#include "llvm/Function.h"
-#include "llvm/Instructions.h"
-#include "llvm/Pass.h"
-#include "llvm/Support/Debug.h"
-#include "llvm/Support/Visibility.h"
-#include "llvm/ADT/Statistic.h"
-#include <algorithm>
-#include <iostream>
-using namespace llvm;
-
-namespace {
-  Statistic<> NumLowered("lowerswitch", "Number of SwitchInst's replaced");
-
-  /// LowerSwitch Pass - Replace all SwitchInst instructions with chained branch
-  /// instructions.  Note that this cannot be a BasicBlock pass because it
-  /// modifies the CFG!
-  class VISIBILITY_HIDDEN LowerSwitch : public FunctionPass {
-  public:
-    virtual bool runOnFunction(Function &F);
-    
-    virtual void getAnalysisUsage(AnalysisUsage &AU) const {
-      // This is a cluster of orthogonal Transforms	
-      AU.addPreserved<UnifyFunctionExitNodes>();
-      AU.addPreservedID(PromoteMemoryToRegisterID);
-      AU.addPreservedID(LowerSelectID);
-      AU.addPreservedID(LowerInvokePassID);
-      AU.addPreservedID(LowerAllocationsID);
-    }
-        
-    typedef std::pair<Constant*, BasicBlock*> Case;
-    typedef std::vector<Case>::iterator       CaseItr;
-  private:
-    void processSwitchInst(SwitchInst *SI);
-
-    BasicBlock* switchConvert(CaseItr Begin, CaseItr End, Value* Val,
-                              BasicBlock* OrigBlock, BasicBlock* Default);
-    BasicBlock* newLeafBlock(Case& Leaf, Value* Val,
-                             BasicBlock* OrigBlock, BasicBlock* Default);
-  };
-
-  /// The comparison function for sorting the switch case values in the vector.
-  struct CaseCmp {
-    bool operator () (const LowerSwitch::Case& C1,
-                      const LowerSwitch::Case& C2) {
-      if (const ConstantUInt* U1 = dyn_cast<const ConstantUInt>(C1.first))
-        return U1->getValue() < cast<const ConstantUInt>(C2.first)->getValue();
-
-      const ConstantSInt* S1 = dyn_cast<const ConstantSInt>(C1.first);
-      return S1->getValue() < cast<const ConstantSInt>(C2.first)->getValue();
-    }
-  };
-
-  RegisterOpt<LowerSwitch>
-  X("lowerswitch", "Lower SwitchInst's to branches");
-}
-
-// Publically exposed interface to pass...
-const PassInfo *llvm::LowerSwitchID = X.getPassInfo();
-// createLowerSwitchPass - Interface to this file...
-FunctionPass *llvm::createLowerSwitchPass() {
-  return new LowerSwitch();
-}
-
-bool LowerSwitch::runOnFunction(Function &F) {
-  bool Changed = false;
-
-  for (Function::iterator I = F.begin(), E = F.end(); I != E; ) {
-    BasicBlock *Cur = I++; // Advance over block so we don't traverse new blocks
-
-    if (SwitchInst *SI = dyn_cast<SwitchInst>(Cur->getTerminator())) {
-      Changed = true;
-      processSwitchInst(SI);
-    }
-  }
-
-  return Changed;
-}
-
-// operator<< - Used for debugging purposes.
-//
-std::ostream& operator<<(std::ostream &O,
-                         const std::vector<LowerSwitch::Case> &C) {
-  O << "[";
-
-  for (std::vector<LowerSwitch::Case>::const_iterator B = C.begin(),
-         E = C.end(); B != E; ) {
-    O << *B->first;
-    if (++B != E) O << ", ";
-  }
-
-  return O << "]";
-}
-
-// switchConvert - Convert the switch statement into a binary lookup of
-// the case values. The function recursively builds this tree.
-//
-BasicBlock* LowerSwitch::switchConvert(CaseItr Begin, CaseItr End,
-                                       Value* Val, BasicBlock* OrigBlock,
-                                       BasicBlock* Default)
-{
-  unsigned Size = End - Begin;
-
-  if (Size == 1)
-    return newLeafBlock(*Begin, Val, OrigBlock, Default);
-
-  unsigned Mid = Size / 2;
-  std::vector<Case> LHS(Begin, Begin + Mid);
-  DEBUG(std::cerr << "LHS: " << LHS << "\n");
-  std::vector<Case> RHS(Begin + Mid, End);
-  DEBUG(std::cerr << "RHS: " << RHS << "\n");
-
-  Case& Pivot = *(Begin + Mid);
-  DEBUG(std::cerr << "Pivot ==> "
-                  << (int64_t)cast<ConstantInt>(Pivot.first)->getRawValue()
-                  << "\n");
-
-  BasicBlock* LBranch = switchConvert(LHS.begin(), LHS.end(), Val,
-                                      OrigBlock, Default);
-  BasicBlock* RBranch = switchConvert(RHS.begin(), RHS.end(), Val,
-                                      OrigBlock, Default);
-
-  // Create a new node that checks if the value is < pivot. Go to the
-  // left branch if it is and right branch if not.
-  Function* F = OrigBlock->getParent();
-  BasicBlock* NewNode = new BasicBlock("NodeBlock");
-  F->getBasicBlockList().insert(OrigBlock->getNext(), NewNode);
-
-  SetCondInst* Comp = new SetCondInst(Instruction::SetLT, Val, Pivot.first,
-                                      "Pivot");
-  NewNode->getInstList().push_back(Comp);
-  new BranchInst(LBranch, RBranch, Comp, NewNode);
-  return NewNode;
-}
-
-// newLeafBlock - Create a new leaf block for the binary lookup tree. It
-// checks if the switch's value == the case's value. If not, then it
-// jumps to the default branch. At this point in the tree, the value
-// can't be another valid case value, so the jump to the "default" branch
-// is warranted.
-//
-BasicBlock* LowerSwitch::newLeafBlock(Case& Leaf, Value* Val,
-                                      BasicBlock* OrigBlock,
-                                      BasicBlock* Default)
-{
-  Function* F = OrigBlock->getParent();
-  BasicBlock* NewLeaf = new BasicBlock("LeafBlock");
-  F->getBasicBlockList().insert(OrigBlock->getNext(), NewLeaf);
-
-  // Make the seteq instruction...
-  SetCondInst* Comp = new SetCondInst(Instruction::SetEQ, Val,
-                                      Leaf.first, "SwitchLeaf");
-  NewLeaf->getInstList().push_back(Comp);
-
-  // Make the conditional branch...
-  BasicBlock* Succ = Leaf.second;
-  new BranchInst(Succ, Default, Comp, NewLeaf);
-
-  // If there were any PHI nodes in this successor, rewrite one entry
-  // from OrigBlock to come from NewLeaf.
-  for (BasicBlock::iterator I = Succ->begin(); isa<PHINode>(I); ++I) {
-    PHINode* PN = cast<PHINode>(I);
-    int BlockIdx = PN->getBasicBlockIndex(OrigBlock);
-    assert(BlockIdx != -1 && "Switch didn't go to this successor??");
-    PN->setIncomingBlock((unsigned)BlockIdx, NewLeaf);
-  }
-
-  return NewLeaf;
-}
-
-// processSwitchInst - Replace the specified switch instruction with a sequence
-// of chained if-then insts in a balanced binary search.
-//
-void LowerSwitch::processSwitchInst(SwitchInst *SI) {
-  BasicBlock *CurBlock = SI->getParent();
-  BasicBlock *OrigBlock = CurBlock;
-  Function *F = CurBlock->getParent();
-  Value *Val = SI->getOperand(0);  // The value we are switching on...
-  BasicBlock* Default = SI->getDefaultDest();
-
-  // If there is only the default destination, don't bother with the code below.
-  if (SI->getNumOperands() == 2) {
-    new BranchInst(SI->getDefaultDest(), CurBlock);
-    CurBlock->getInstList().erase(SI);
-    return;
-  }
-
-  // Create a new, empty default block so that the new hierarchy of
-  // if-then statements go to this and the PHI nodes are happy.
-  BasicBlock* NewDefault = new BasicBlock("NewDefault");
-  F->getBasicBlockList().insert(Default, NewDefault);
-
-  new BranchInst(Default, NewDefault);
-
-  // If there is an entry in any PHI nodes for the default edge, make sure
-  // to update them as well.
-  for (BasicBlock::iterator I = Default->begin(); isa<PHINode>(I); ++I) {
-    PHINode *PN = cast<PHINode>(I);
-    int BlockIdx = PN->getBasicBlockIndex(OrigBlock);
-    assert(BlockIdx != -1 && "Switch didn't go to this successor??");
-    PN->setIncomingBlock((unsigned)BlockIdx, NewDefault);
-  }
-
-  std::vector<Case> Cases;
-
-  // Expand comparisons for all of the non-default cases...
-  for (unsigned i = 1; i < SI->getNumSuccessors(); ++i)
-    Cases.push_back(Case(SI->getSuccessorValue(i), SI->getSuccessor(i)));
-
-  std::sort(Cases.begin(), Cases.end(), CaseCmp());
-  DEBUG(std::cerr << "Cases: " << Cases << "\n");
-  BasicBlock* SwitchBlock = switchConvert(Cases.begin(), Cases.end(), Val,
-                                          OrigBlock, NewDefault);
-
-  // Branch to our shiny new if-then stuff...
-  new BranchInst(SwitchBlock, OrigBlock);
-
-  // We are now done with the switch instruction, delete it.
-  CurBlock->getInstList().erase(SI);
-}