-//===- ConstantProp.cpp - Code to perform Simple Constant Propogation -----===//
+//===- ConstantProp.cpp - Code to perform Simple Constant Propagation -----===//
//
-// This file implements constant propogation and merging:
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements constant propagation and merging:
//
// Specifically, this:
// * Converts instructions like "add int 1, 2" into 3
//
// Notice that:
// * This pass has a habit of making definitions be dead. It is a good idea
-// to to run a DIE pass sometime after running this pass.
+// to run a DIE pass sometime after running this pass.
//
//===----------------------------------------------------------------------===//
-#include "llvm/Transforms/Scalar/ConstantProp.h"
-#include "llvm/ConstantHandling.h"
-#include "llvm/Function.h"
-#include "llvm/BasicBlock.h"
-#include "llvm/iTerminators.h"
+#include "llvm/Transforms/Scalar.h"
+#include "llvm/ADT/Statistic.h"
+#include "llvm/Analysis/ConstantFolding.h"
+#include "llvm/IR/Constant.h"
+#include "llvm/IR/InstIterator.h"
+#include "llvm/IR/Instruction.h"
#include "llvm/Pass.h"
-#include "llvm/Support/InstIterator.h"
+#include "llvm/Analysis/TargetLibraryInfo.h"
#include <set>
+using namespace llvm;
-// FIXME: ConstantFoldInstruction & ConstantFoldTerminator should be moved out
-// to the Transformations library.
-
-// ConstantFoldInstruction - If an instruction references constants, try to fold
-// them together...
-//
-bool doConstantPropogation(BasicBlock *BB, BasicBlock::iterator &II) {
- Instruction *Inst = *II;
- if (Constant *C = ConstantFoldInstruction(Inst)) {
- // Replaces all of the uses of a variable with uses of the constant.
- Inst->replaceAllUsesWith(C);
-
- // Remove the instruction from the basic block...
- delete BB->getInstList().remove(II);
- return true;
- }
-
- return false;
-}
-
-// ConstantFoldTerminator - If a terminator instruction is predicated on a
-// constant value, convert it into an unconditional branch to the constant
-// destination.
-//
-bool ConstantFoldTerminator(BasicBlock *BB, BasicBlock::iterator &II,
- TerminatorInst *T) {
- // Branch - See if we are conditional jumping on constant
- if (BranchInst *BI = dyn_cast<BranchInst>(T)) {
- if (BI->isUnconditional()) return false; // Can't optimize uncond branch
- BasicBlock *Dest1 = cast<BasicBlock>(BI->getOperand(0));
- BasicBlock *Dest2 = cast<BasicBlock>(BI->getOperand(1));
-
- if (ConstantBool *Cond = dyn_cast<ConstantBool>(BI->getCondition())) {
- // Are we branching on constant?
- // YES. Change to unconditional branch...
- BasicBlock *Destination = Cond->getValue() ? Dest1 : Dest2;
- BasicBlock *OldDest = Cond->getValue() ? Dest2 : Dest1;
-
- //cerr << "Function: " << T->getParent()->getParent()
- // << "\nRemoving branch from " << T->getParent()
- // << "\n\nTo: " << OldDest << endl;
-
- // Let the basic block know that we are letting go of it. Based on this,
- // it will adjust it's PHI nodes.
- assert(BI->getParent() && "Terminator not inserted in block!");
- OldDest->removePredecessor(BI->getParent());
-
- // Set the unconditional destination, and change the insn to be an
- // unconditional branch.
- BI->setUnconditionalDest(Destination);
- II = BB->end()-1; // Update instruction iterator!
- return true;
- }
-#if 0
- // FIXME: TODO: This doesn't work if the destination has PHI nodes with
- // different incoming values on each branch!
- //
- else if (Dest2 == Dest1) { // Conditional branch to same location?
- // This branch matches something like this:
- // br bool %cond, label %Dest, label %Dest
- // and changes it into: br label %Dest
-
- // Let the basic block know that we are letting go of one copy of it.
- assert(BI->getParent() && "Terminator not inserted in block!");
- Dest1->removePredecessor(BI->getParent());
-
- // Change a conditional branch to unconditional.
- BI->setUnconditionalDest(Dest1);
- return true;
- }
-#endif
- }
- return false;
-}
-
+#define DEBUG_TYPE "constprop"
+STATISTIC(NumInstKilled, "Number of instructions killed");
namespace {
- struct ConstantPropogation : public FunctionPass {
- const char *getPassName() const { return "Simple Constant Propogation"; }
+ struct ConstantPropagation : public FunctionPass {
+ static char ID; // Pass identification, replacement for typeid
+ ConstantPropagation() : FunctionPass(ID) {
+ initializeConstantPropagationPass(*PassRegistry::getPassRegistry());
+ }
- inline bool runOnFunction(Function *F);
+ bool runOnFunction(Function &F) override;
- virtual void getAnalysisUsage(AnalysisUsage &AU) const {
- AU.preservesCFG();
+ void getAnalysisUsage(AnalysisUsage &AU) const override {
+ AU.setPreservesCFG();
+ AU.addRequired<TargetLibraryInfoWrapperPass>();
}
};
}
-Pass *createConstantPropogationPass() {
- return new ConstantPropogation();
-}
+char ConstantPropagation::ID = 0;
+INITIALIZE_PASS_BEGIN(ConstantPropagation, "constprop",
+ "Simple constant propagation", false, false)
+INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfoWrapperPass)
+INITIALIZE_PASS_END(ConstantPropagation, "constprop",
+ "Simple constant propagation", false, false)
+FunctionPass *llvm::createConstantPropagationPass() {
+ return new ConstantPropagation();
+}
-bool ConstantPropogation::runOnFunction(Function *F) {
+bool ConstantPropagation::runOnFunction(Function &F) {
// Initialize the worklist to all of the instructions ready to process...
- std::set<Instruction*> WorkList(inst_begin(F), inst_end(F));
+ std::set<Instruction*> WorkList;
+ for(inst_iterator i = inst_begin(F), e = inst_end(F); i != e; ++i) {
+ WorkList.insert(&*i);
+ }
bool Changed = false;
+ const DataLayout &DL = F.getParent()->getDataLayout();
+ TargetLibraryInfo *TLI =
+ &getAnalysis<TargetLibraryInfoWrapperPass>().getTLI();
while (!WorkList.empty()) {
Instruction *I = *WorkList.begin();
WorkList.erase(WorkList.begin()); // Get an element from the worklist...
if (!I->use_empty()) // Don't muck with dead instructions...
- if (Constant *C = ConstantFoldInstruction(I)) {
+ if (Constant *C = ConstantFoldInstruction(I, DL, TLI)) {
// Add all of the users of this instruction to the worklist, they might
- // be constant propogatable now...
- for (Value::use_iterator UI = I->use_begin(), UE = I->use_end();
- UI != UE; ++UI)
- WorkList.insert(cast<Instruction>(*UI));
-
+ // be constant propagatable now...
+ for (User *U : I->users())
+ WorkList.insert(cast<Instruction>(U));
+
// Replace all of the uses of a variable with uses of the constant.
I->replaceAllUsesWith(C);
-
+
+ // Remove the dead instruction.
+ WorkList.erase(I);
+ I->eraseFromParent();
+
// We made a change to the function...
Changed = true;
+ ++NumInstKilled;
}
}
return Changed;
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