Rebased PNaCl localmods in LLVM to 223109

lib/Transforms/NaCl/GlobalizeConstantVectors.cpp

+//===- GlobalizeConstantVectors.cpp - Globalize constant vector -----------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This pass replaces all constant vector operands by loads of the same
+// vector value from a constant global. After this pass functions don't
+// rely on ConstantVector and ConstantDataVector.
+//
+// The FlattenGlobals pass can be used to further simplify the globals
+// that this pass creates.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/ADT/DenseMap.h"
+#include "llvm/ADT/SmallPtrSet.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/DataLayout.h"
+#include "llvm/IR/InstIterator.h"
+#include "llvm/IR/Instructions.h"
+#include "llvm/IR/Module.h"
+#include "llvm/Pass.h"
+#include "llvm/Transforms/NaCl.h"
+#include <utility>
+#include <vector>
+
+using namespace llvm;
+
+namespace {
+// Must be a ModulePass since it adds globals.
+class GlobalizeConstantVectors : public ModulePass {
+public:
+  static char ID; // Pass identification, replacement for typeid
+  GlobalizeConstantVectors() : ModulePass(ID), DL(0) {
+    initializeGlobalizeConstantVectorsPass(*PassRegistry::getPassRegistry());
+  }
+  virtual void getAnalysisUsage(AnalysisUsage &AU) const {
+    AU.setPreservesCFG();
+    AU.addRequired<DataLayoutPass>();
+  }
+  virtual bool runOnModule(Module &M);
+
+private:
+  typedef SmallPtrSet<Constant *, 64> Constants;
+  typedef std::pair<Function *, Constants> FunctionConstants;
+  typedef std::vector<FunctionConstants> FunctionConstantList;
+  typedef DenseMap<Constant *, GlobalVariable *> GlobalizedConstants;
+  const DataLayout *DL;
+
+  void findConstantVectors(const Function &F, Constants &Cs) const;
+  void createGlobalConstantVectors(Module &M, const FunctionConstantList &FCs,
+                                   GlobalizedConstants &GCs) const;
+  void materializeConstantVectors(Function &F, const Constants &Cs,
+                                  const GlobalizedConstants &GCs) const;
+};
+
+const char Name[] = "constant_vector";
+} // anonymous namespace
+
+char GlobalizeConstantVectors::ID = 0;
+INITIALIZE_PASS(GlobalizeConstantVectors, "globalize-constant-vectors",
+                "Replace constant vector operands with equivalent loads", false,
+                false)
+
+void GlobalizeConstantVectors::findConstantVectors(const Function &F,
+                                                   Constants &Cs) const {
+  for (const_inst_iterator II = inst_begin(F), IE = inst_end(F); II != IE;
+       ++II) {
+    for (User::const_op_iterator OI = II->op_begin(), OE = II->op_end();
+         OI != OE; ++OI) {
+      Value *V = OI->get();
+      if (isa<ConstantVector>(V) || isa<ConstantDataVector>(V) ||
+          isa<ConstantAggregateZero>(V))
+        Cs.insert(cast<Constant>(V));
+    }
+  }
+}
+
+void GlobalizeConstantVectors::createGlobalConstantVectors(
+    Module &M, const FunctionConstantList &FCs,
+    GlobalizedConstants &GCs) const {
+  for (FunctionConstantList::const_iterator FCI = FCs.begin(), FCE = FCs.end();
+       FCI != FCE; ++FCI) {
+    const Constants &Cs = FCI->second;
+
+    for (Constants::const_iterator CI = Cs.begin(), CE = Cs.end(); CI != CE;
+         ++CI) {
+      Constant *C = *CI;
+      if (GCs.find(C) != GCs.end())
+        continue; // The vector has already been globalized.
+      GlobalVariable *GV =
+          new GlobalVariable(M, C->getType(), /* isConstant= */ true,
+                             GlobalValue::InternalLinkage, C, Name);
+      GV->setAlignment(DL->getPrefTypeAlignment(C->getType()));
+      GV->setUnnamedAddr(true); // The content is significant, not the address.
+      GCs[C] = GV;
+    }
+  }
+}
+
+void GlobalizeConstantVectors::materializeConstantVectors(
+    Function &F, const Constants &Cs, const GlobalizedConstants &GCs) const {
+  // The first instruction in a function dominates all others, it is therefore a
+  // safe insertion point.
+  Instruction *FirstInst = F.getEntryBlock().getFirstNonPHI();
+
+  for (Constants::const_iterator CI = Cs.begin(), CE = Cs.end(); CI != CE;
+       ++CI) {
+    Constant *C = *CI;
+    GlobalizedConstants::const_iterator GVI = GCs.find(C);
+    assert(GVI != GCs.end());
+    GlobalVariable *GV = GVI->second;
+    LoadInst *MaterializedGV = new LoadInst(GV, Name, /* isVolatile= */ false,
+                                            GV->getAlignment(), FirstInst);
+
+    // Find users of the constant vector.
+    typedef SmallVector<User *, 64> UserList;
+    UserList CVUsers;
+    for (auto U : C->users()) {
+      if (Instruction *I = dyn_cast<Instruction>(U))
+        if (I->getParent()->getParent() != &F)
+          // Skip uses of the constant vector in other functions: we need to
+          // materialize it in every function which has a use.
+          continue;
+      if (isa<Constant>(U))
+        // Don't replace global uses of the constant vector: we just created a
+        // new one. This avoid recursive references.
+        // Also, it's not legal to replace a constant's operand with
+        // a non-constant (the load instruction).
+        continue;
+      CVUsers.push_back(U);
+    }
+
+    // Replace these Users. Must be done separately to avoid invalidating the
+    // User iterator.
+    for (UserList::iterator UI = CVUsers.begin(), UE = CVUsers.end(); UI != UE;
+         ++UI) {
+      User *U = *UI;
+      for (User::op_iterator OI = U->op_begin(), OE = U->op_end(); OI != OE;
+           ++OI)
+        if (dyn_cast<Constant>(*OI) == C)
+          // The current operand is a use of the constant vector, replace it
+          // with the materialized one.
+          *OI = MaterializedGV;
+    }
+  }
+}
+
+bool GlobalizeConstantVectors::runOnModule(Module &M) {
+  DL = &getAnalysis<DataLayoutPass>().getDataLayout();
+
+  FunctionConstantList FCs;
+  FCs.reserve(M.size());
+  for (Module::iterator FI = M.begin(), FE = M.end(); FI != FE; ++FI) {
+    Constants Cs;
+    findConstantVectors(*FI, Cs);
+    if (!Cs.empty())
+      FCs.push_back(std::make_pair(&*FI, Cs));
+  }
+
+  GlobalizedConstants GCs;
+  createGlobalConstantVectors(M, FCs, GCs);
+
+  for (FunctionConstantList::const_iterator FCI = FCs.begin(), FCE = FCs.end();
+       FCI != FCE; ++FCI)
+    materializeConstantVectors(*FCI->first, FCI->second, GCs);
+
+  return FCs.empty();
+}
+
+ModulePass *llvm::createGlobalizeConstantVectorsPass() {
+  return new GlobalizeConstantVectors();
+}