AutoUpgrade.cpp   [plain text]

//===-- AutoUpgrade.cpp - Implement auto-upgrade helper functions ---------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements the auto-upgrade helper functions 
//
//===----------------------------------------------------------------------===//

#include "llvm/AutoUpgrade.h"
#include "llvm/Constants.h"
#include "llvm/Function.h"
#include "llvm/Instruction.h"
#include "llvm/LLVMContext.h"
#include "llvm/Module.h"
#include "llvm/IntrinsicInst.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/Support/CallSite.h"
#include "llvm/Support/CFG.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/IRBuilder.h"
#include <cstring>
using namespace llvm;


static bool UpgradeIntrinsicFunction1(Function *F, Function *&NewFn) {
  assert(F && "Illegal to upgrade a non-existent Function.");

  // Quickly eliminate it, if it's not a candidate.
  StringRef Name = F->getName();
  if (Name.size() <= 8 || !Name.startswith("llvm."))
    return false;
  Name = Name.substr(5); // Strip off "llvm."

  switch (Name[0]) {
  default: break;
  case 'c': {
    if (Name.startswith("ctlz.") && F->arg_size() == 1) {
      F->setName(Name + ".old");
      NewFn = Intrinsic::getDeclaration(F->getParent(), Intrinsic::ctlz,
                                        F->arg_begin()->getType());
      return true;
    }
    if (Name.startswith("cttz.") && F->arg_size() == 1) {
      F->setName(Name + ".old");
      NewFn = Intrinsic::getDeclaration(F->getParent(), Intrinsic::cttz,
                                        F->arg_begin()->getType());
      return true;
    }
    break;
  }
  case 'x': {
    if (Name.startswith("x86.sse2.pcmpeq.") ||
        Name.startswith("x86.sse2.pcmpgt.") ||
        Name.startswith("x86.avx2.pcmpeq.") ||
        Name.startswith("x86.avx2.pcmpgt.")) {
      NewFn = 0;
      return true;
    }
    break;
  }
  }

  //  This may not belong here. This function is effectively being overloaded 
  //  to both detect an intrinsic which needs upgrading, and to provide the 
  //  upgraded form of the intrinsic. We should perhaps have two separate 
  //  functions for this.
  return false;
}

bool llvm::UpgradeIntrinsicFunction(Function *F, Function *&NewFn) {
  NewFn = 0;
  bool Upgraded = UpgradeIntrinsicFunction1(F, NewFn);

  // Upgrade intrinsic attributes.  This does not change the function.
  if (NewFn)
    F = NewFn;
  if (unsigned id = F->getIntrinsicID())
    F->setAttributes(Intrinsic::getAttributes((Intrinsic::ID)id));
  return Upgraded;
}

bool llvm::UpgradeGlobalVariable(GlobalVariable *GV) {
  // Nothing to do yet.
  return false;
}

// UpgradeIntrinsicCall - Upgrade a call to an old intrinsic to be a call the 
// upgraded intrinsic. All argument and return casting must be provided in 
// order to seamlessly integrate with existing context.
void llvm::UpgradeIntrinsicCall(CallInst *CI, Function *NewFn) {
  Function *F = CI->getCalledFunction();
  LLVMContext &C = CI->getContext();
  IRBuilder<> Builder(C);
  Builder.SetInsertPoint(CI->getParent(), CI);

  assert(F && "Intrinsic call is not direct?");

  if (!NewFn) {
    // Get the Function's name.
    StringRef Name = F->getName();

    Value *Rep;
    // Upgrade packed integer vector compares intrinsics to compare instructions
    if (Name.startswith("llvm.x86.sse2.pcmpeq.") ||
        Name.startswith("llvm.x86.avx2.pcmpeq.")) {
      Rep = Builder.CreateICmpEQ(CI->getArgOperand(0), CI->getArgOperand(1),
                                 "pcmpeq");
      // need to sign extend since icmp returns vector of i1
      Rep = Builder.CreateSExt(Rep, CI->getType(), "");
    } else if (Name.startswith("llvm.x86.sse2.pcmpgt.") ||
               Name.startswith("llvm.x86.avx2.pcmpgt.")) {
      Rep = Builder.CreateICmpSGT(CI->getArgOperand(0), CI->getArgOperand(1),
                                  "pcmpgt");
      // need to sign extend since icmp returns vector of i1
      Rep = Builder.CreateSExt(Rep, CI->getType(), "");
    } else {
      llvm_unreachable("Unknown function for CallInst upgrade.");
    }

    CI->replaceAllUsesWith(Rep);
    CI->eraseFromParent();
    return;
  }

  switch (NewFn->getIntrinsicID()) {
  default:
    llvm_unreachable("Unknown function for CallInst upgrade.");

  case Intrinsic::ctlz:
  case Intrinsic::cttz:
    assert(CI->getNumArgOperands() == 1 &&
           "Mismatch between function args and call args");
    StringRef Name = CI->getName();
    CI->setName(Name + ".old");
    CI->replaceAllUsesWith(Builder.CreateCall2(NewFn, CI->getArgOperand(0),
                                               Builder.getFalse(), Name));
    CI->eraseFromParent();
    return;
  }
}

// This tests each Function to determine if it needs upgrading. When we find 
// one we are interested in, we then upgrade all calls to reflect the new 
// function.
void llvm::UpgradeCallsToIntrinsic(Function* F) {
  assert(F && "Illegal attempt to upgrade a non-existent intrinsic.");

  // Upgrade the function and check if it is a totaly new function.
  Function *NewFn;
  if (UpgradeIntrinsicFunction(F, NewFn)) {
    if (NewFn != F) {
      // Replace all uses to the old function with the new one if necessary.
      for (Value::use_iterator UI = F->use_begin(), UE = F->use_end();
           UI != UE; ) {
        if (CallInst *CI = dyn_cast<CallInst>(*UI++))
          UpgradeIntrinsicCall(CI, NewFn);
      }
      // Remove old function, no longer used, from the module.
      F->eraseFromParent();
    }
  }
}