1 files changed, 132 insertions, 0 deletions
diff --git a/contrib/llvm/lib/Transforms/Scalar/DCE.cpp b/contrib/llvm/lib/Transforms/Scalar/DCE.cpp
new file mode 100644
index 0000000..39940c3
--- /dev/null
+++ b/contrib/llvm/lib/Transforms/Scalar/DCE.cpp
@@ -0,0 +1,132 @@
+//===- DCE.cpp - Code to perform dead code elimination --------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements dead inst elimination and dead code elimination.
+//
+// Dead Inst Elimination performs a single pass over the function removing
+// instructions that are obviously dead.  Dead Code Elimination is similar, but
+// it rechecks instructions that were used by removed instructions to see if
+// they are newly dead.
+//
+//===----------------------------------------------------------------------===//
+
+#define DEBUG_TYPE "dce"
+#include "llvm/Transforms/Scalar.h"
+#include "llvm/Transforms/Utils/Local.h"
+#include "llvm/Instruction.h"
+#include "llvm/Pass.h"
+#include "llvm/Support/InstIterator.h"
+#include "llvm/ADT/Statistic.h"
+#include <set>
+using namespace llvm;
+
+STATISTIC(DIEEliminated, "Number of insts removed by DIE pass");
+STATISTIC(DCEEliminated, "Number of insts removed");
+
+namespace {
+  //===--------------------------------------------------------------------===//
+  // DeadInstElimination pass implementation
+  //
+  struct DeadInstElimination : public BasicBlockPass {
+    static char ID; // Pass identification, replacement for typeid
+    DeadInstElimination() : BasicBlockPass(&ID) {}
+    virtual bool runOnBasicBlock(BasicBlock &BB) {
+      bool Changed = false;
+      for (BasicBlock::iterator DI = BB.begin(); DI != BB.end(); ) {
+        Instruction *Inst = DI++;
+        if (isInstructionTriviallyDead(Inst)) {
+          Inst->eraseFromParent();
+          Changed = true;
+          ++DIEEliminated;
+        }
+      }
+      return Changed;
+    }
+
+    virtual void getAnalysisUsage(AnalysisUsage &AU) const {
+      AU.setPreservesCFG();
+    }
+  };
+}
+
+char DeadInstElimination::ID = 0;
+static RegisterPass<DeadInstElimination>
+X("die", "Dead Instruction Elimination");
+
+Pass *llvm::createDeadInstEliminationPass() {
+  return new DeadInstElimination();
+}
+
+
+namespace {
+  //===--------------------------------------------------------------------===//
+  // DeadCodeElimination pass implementation
+  //
+  struct DCE : public FunctionPass {
+    static char ID; // Pass identification, replacement for typeid
+    DCE() : FunctionPass(&ID) {}
+
+    virtual bool runOnFunction(Function &F);
+
+     virtual void getAnalysisUsage(AnalysisUsage &AU) const {
+      AU.setPreservesCFG();
+    }
+ };
+}
+
+char DCE::ID = 0;
+static RegisterPass<DCE> Y("dce", "Dead Code Elimination");
+
+bool DCE::runOnFunction(Function &F) {
+  // Start out with all of the instructions in the worklist...
+  std::vector<Instruction*> WorkList;
+  for (inst_iterator i = inst_begin(F), e = inst_end(F); i != e; ++i)
+    WorkList.push_back(&*i);
+
+  // Loop over the worklist finding instructions that are dead.  If they are
+  // dead make them drop all of their uses, making other instructions
+  // potentially dead, and work until the worklist is empty.
+  //
+  bool MadeChange = false;
+  while (!WorkList.empty()) {
+    Instruction *I = WorkList.back();
+    WorkList.pop_back();
+
+    if (isInstructionTriviallyDead(I)) {       // If the instruction is dead.
+      // Loop over all of the values that the instruction uses, if there are
+      // instructions being used, add them to the worklist, because they might
+      // go dead after this one is removed.
+      //
+      for (User::op_iterator OI = I->op_begin(), E = I->op_end(); OI != E; ++OI)
+        if (Instruction *Used = dyn_cast<Instruction>(*OI))
+          WorkList.push_back(Used);
+
+      // Remove the instruction.
+      I->eraseFromParent();
+
+      // Remove the instruction from the worklist if it still exists in it.
+      for (std::vector<Instruction*>::iterator WI = WorkList.begin();
+           WI != WorkList.end(); ) {
+        if (*WI == I)
+          WI = WorkList.erase(WI);
+        else
+          ++WI;
+      }
+
+      MadeChange = true;
+      ++DCEEliminated;
+    }
+  }
+  return MadeChange;
+}
+
+FunctionPass *llvm::createDeadCodeEliminationPass() {
+  return new DCE();
+}
+