SimplifyLibCalls.cpp

        CI->use_empty()) {
      EmitPutS(CI->getOperand(2), B);
      return CI;
    }
    return 0;
  }
};

//===---------------------------------------===//
// 'sprintf' Optimizations

struct VISIBILITY_HIDDEN SPrintFOpt : public LibCallOptimization {
  virtual Value *CallOptimizer(Function *Callee, CallInst *CI, IRBuilder<> &B) {
    // Require two fixed pointer arguments and an integer result.
    const FunctionType *FT = Callee->getFunctionType();
    if (FT->getNumParams() != 2 || !isa<PointerType>(FT->getParamType(0)) ||
        !isa<PointerType>(FT->getParamType(1)) ||
        !isa<IntegerType>(FT->getReturnType()))
      return 0;

    // Check for a fixed format string.
    std::string FormatStr;
    if (!GetConstantStringInfo(CI->getOperand(2), FormatStr))
      return 0;
    
    // If we just have a format string (nothing else crazy) transform it.
    if (CI->getNumOperands() == 3) {
      // Make sure there's no % in the constant array.  We could try to handle
      // %% -> % in the future if we cared.
      for (unsigned i = 0, e = FormatStr.size(); i != e; ++i)
        if (FormatStr[i] == '%')
          return 0; // we found a format specifier, bail out.
      
      // sprintf(str, fmt) -> llvm.memcpy(str, fmt, strlen(fmt)+1, 1)
      EmitMemCpy(CI->getOperand(1), CI->getOperand(2), // Copy the nul byte.
                 ConstantInt::get(TD->getIntPtrType(), FormatStr.size()+1),1,B);
      return ConstantInt::get(CI->getType(), FormatStr.size());
    }
    
    // The remaining optimizations require the format string to be "%s" or "%c"
    // and have an extra operand.
    if (FormatStr.size() != 2 || FormatStr[0] != '%' || CI->getNumOperands() <4)
      return 0;
    
    // Decode the second character of the format string.
    if (FormatStr[1] == 'c') {
      // sprintf(dst, "%c", chr) --> *(i8*)dst = chr; *((i8*)dst+1) = 0
      if (!isa<IntegerType>(CI->getOperand(3)->getType())) return 0;
      Value *V = B.CreateTrunc(CI->getOperand(3), Type::Int8Ty, "char");
      Value *Ptr = CastToCStr(CI->getOperand(1), B);
      B.CreateStore(V, Ptr);
      Ptr = B.CreateGEP(Ptr, ConstantInt::get(Type::Int32Ty, 1), "nul");
      B.CreateStore(Constant::getNullValue(Type::Int8Ty), Ptr);
      
      return ConstantInt::get(CI->getType(), 1);
    }
    
    if (FormatStr[1] == 's') {
      // sprintf(dest, "%s", str) -> llvm.memcpy(dest, str, strlen(str)+1, 1)
      if (!isa<PointerType>(CI->getOperand(3)->getType())) return 0;

      Value *Len = EmitStrLen(CI->getOperand(3), B);
      Value *IncLen = B.CreateAdd(Len, ConstantInt::get(Len->getType(), 1),
                                  "leninc");
      EmitMemCpy(CI->getOperand(1), CI->getOperand(3), IncLen, 1, B);
      
      // The sprintf result is the unincremented number of bytes in the string.
      return B.CreateIntCast(Len, CI->getType(), false);
    }
    return 0;
  }
};

//===---------------------------------------===//
// 'fwrite' Optimizations

struct VISIBILITY_HIDDEN FWriteOpt : public LibCallOptimization {
  virtual Value *CallOptimizer(Function *Callee, CallInst *CI, IRBuilder<> &B) {
    // Require a pointer, an integer, an integer, a pointer, returning integer.
    const FunctionType *FT = Callee->getFunctionType();
    if (FT->getNumParams() != 4 || !isa<PointerType>(FT->getParamType(0)) ||
        !isa<IntegerType>(FT->getParamType(1)) ||
        !isa<IntegerType>(FT->getParamType(2)) ||
        !isa<PointerType>(FT->getParamType(3)) ||
        !isa<IntegerType>(FT->getReturnType()))
      return 0;
    
    // Get the element size and count.
    ConstantInt *SizeC = dyn_cast<ConstantInt>(CI->getOperand(2));
    ConstantInt *CountC = dyn_cast<ConstantInt>(CI->getOperand(3));
    if (!SizeC || !CountC) return 0;
    uint64_t Bytes = SizeC->getZExtValue()*CountC->getZExtValue();
    
    // If this is writing zero records, remove the call (it's a noop).
    if (Bytes == 0)
      return ConstantInt::get(CI->getType(), 0);
    
    // If this is writing one byte, turn it into fputc.
    if (Bytes == 1) {  // fwrite(S,1,1,F) -> fputc(S[0],F)
      Value *Char = B.CreateLoad(CastToCStr(CI->getOperand(1), B), "char");
      EmitFPutC(Char, CI->getOperand(4), B);
      return ConstantInt::get(CI->getType(), 1);
    }

    return 0;
  }
};

//===---------------------------------------===//
// 'fputs' Optimizations

struct VISIBILITY_HIDDEN FPutsOpt : public LibCallOptimization {
  virtual Value *CallOptimizer(Function *Callee, CallInst *CI, IRBuilder<> &B) {
    // Require two pointers.  Also, we can't optimize if return value is used.
    const FunctionType *FT = Callee->getFunctionType();
    if (FT->getNumParams() != 2 || !isa<PointerType>(FT->getParamType(0)) ||
        !isa<PointerType>(FT->getParamType(1)) ||
        !CI->use_empty())
      return 0;
    
    // fputs(s,F) --> fwrite(s,1,strlen(s),F)
    uint64_t Len = GetStringLength(CI->getOperand(1));
    if (!Len) return 0;
    EmitFWrite(CI->getOperand(1), ConstantInt::get(TD->getIntPtrType(), Len-1),
               CI->getOperand(2), B);
    return CI;  // Known to have no uses (see above).
  }
};

//===---------------------------------------===//
// 'fprintf' Optimizations

struct VISIBILITY_HIDDEN FPrintFOpt : public LibCallOptimization {
  virtual Value *CallOptimizer(Function *Callee, CallInst *CI, IRBuilder<> &B) {
    // Require two fixed paramters as pointers and integer result.
    const FunctionType *FT = Callee->getFunctionType();
    if (FT->getNumParams() != 2 || !isa<PointerType>(FT->getParamType(0)) ||
        !isa<PointerType>(FT->getParamType(1)) ||
        !isa<IntegerType>(FT->getReturnType()))
      return 0;
    
    // All the optimizations depend on the format string.
    std::string FormatStr;
    if (!GetConstantStringInfo(CI->getOperand(2), FormatStr))
      return 0;

    // fprintf(F, "foo") --> fwrite("foo", 3, 1, F)
    if (CI->getNumOperands() == 3) {
      for (unsigned i = 0, e = FormatStr.size(); i != e; ++i)
        if (FormatStr[i] == '%')  // Could handle %% -> % if we cared.
          return 0; // We found a format specifier.
      
      EmitFWrite(CI->getOperand(2), ConstantInt::get(TD->getIntPtrType(),
                                                     FormatStr.size()),
                 CI->getOperand(1), B);
      return ConstantInt::get(CI->getType(), FormatStr.size());
    }
    
    // The remaining optimizations require the format string to be "%s" or "%c"
    // and have an extra operand.
    if (FormatStr.size() != 2 || FormatStr[0] != '%' || CI->getNumOperands() <4)
      return 0;
    
    // Decode the second character of the format string.
    if (FormatStr[1] == 'c') {
      // fprintf(F, "%c", chr) --> *(i8*)dst = chr
      if (!isa<IntegerType>(CI->getOperand(3)->getType())) return 0;
      EmitFPutC(CI->getOperand(3), CI->getOperand(1), B);
      return ConstantInt::get(CI->getType(), 1);
    }
    
    if (FormatStr[1] == 's') {
      // fprintf(F, "%s", str) -> fputs(str, F)
      if (!isa<PointerType>(CI->getOperand(3)->getType()) || !CI->use_empty())
        return 0;
      EmitFPutS(CI->getOperand(3), CI->getOperand(1), B);
      return CI;
    }
    return 0;
  }
};

} // end anonymous namespace.

//===----------------------------------------------------------------------===//
// SimplifyLibCalls Pass Implementation
//===----------------------------------------------------------------------===//

namespace {
  /// This pass optimizes well known library functions from libc and libm.
  ///
  class VISIBILITY_HIDDEN SimplifyLibCalls : public FunctionPass {
    StringMap<LibCallOptimization*> Optimizations;
    // Miscellaneous LibCall Optimizations
    ExitOpt Exit; 
    // String and Memory LibCall Optimizations
    StrCatOpt StrCat; StrChrOpt StrChr; StrCmpOpt StrCmp; StrNCmpOpt StrNCmp;
    StrCpyOpt StrCpy; StrLenOpt StrLen; MemCmpOpt MemCmp; MemCpyOpt  MemCpy;
    // Math Library Optimizations
    PowOpt Pow; Exp2Opt Exp2; UnaryDoubleFPOpt UnaryDoubleFP;
    // Integer Optimizations
    FFSOpt FFS; AbsOpt Abs; IsDigitOpt IsDigit; IsAsciiOpt IsAscii;
    ToAsciiOpt ToAscii;
    // Formatting and IO Optimizations
    SPrintFOpt SPrintF; PrintFOpt PrintF;
    FWriteOpt FWrite; FPutsOpt FPuts; FPrintFOpt FPrintF;
  public:
    static char ID; // Pass identification
    SimplifyLibCalls() : FunctionPass(&ID) {}

    void InitOptimizations();
    bool runOnFunction(Function &F);

    virtual void getAnalysisUsage(AnalysisUsage &AU) const {
      AU.addRequired<TargetData>();
    }
  };
  char SimplifyLibCalls::ID = 0;
} // end anonymous namespace.

static RegisterPass<SimplifyLibCalls>
X("simplify-libcalls", "Simplify well-known library calls");

// Public interface to the Simplify LibCalls pass.
FunctionPass *llvm::createSimplifyLibCallsPass() {
  return new SimplifyLibCalls(); 
}

/// Optimizations - Populate the Optimizations map with all the optimizations
/// we know.
void SimplifyLibCalls::InitOptimizations() {
  // Miscellaneous LibCall Optimizations
  Optimizations["exit"] = &Exit;
  
  // String and Memory LibCall Optimizations
  Optimizations["strcat"] = &StrCat;
  Optimizations["strchr"] = &StrChr;
  Optimizations["strcmp"] = &StrCmp;
  Optimizations["strncmp"] = &StrNCmp;
  Optimizations["strcpy"] = &StrCpy;
  Optimizations["strlen"] = &StrLen;
  Optimizations["memcmp"] = &MemCmp;
  Optimizations["memcpy"] = &MemCpy;
  
  // Math Library Optimizations
  Optimizations["powf"] = &Pow;
  Optimizations["pow"] = &Pow;
  Optimizations["powl"] = &Pow;
  Optimizations["exp2l"] = &Exp2;
  Optimizations["exp2"] = &Exp2;
  Optimizations["exp2f"] = &Exp2;
  
#ifdef HAVE_FLOORF
  Optimizations["floor"] = &UnaryDoubleFP;
#endif
#ifdef HAVE_CEILF
  Optimizations["ceil"] = &UnaryDoubleFP;
#endif
#ifdef HAVE_ROUNDF
  Optimizations["round"] = &UnaryDoubleFP;
#endif
#ifdef HAVE_RINTF
  Optimizations["rint"] = &UnaryDoubleFP;
#endif
#ifdef HAVE_NEARBYINTF
  Optimizations["nearbyint"] = &UnaryDoubleFP;
#endif
  
  // Integer Optimizations
  Optimizations["ffs"] = &FFS;
  Optimizations["ffsl"] = &FFS;
  Optimizations["ffsll"] = &FFS;
  Optimizations["abs"] = &Abs;
  Optimizations["labs"] = &Abs;
  Optimizations["llabs"] = &Abs;
  Optimizations["isdigit"] = &IsDigit;
  Optimizations["isascii"] = &IsAscii;
  Optimizations["toascii"] = &ToAscii;
  
  // Formatting and IO Optimizations
  Optimizations["sprintf"] = &SPrintF;
  Optimizations["printf"] = &PrintF;
  Optimizations["fwrite"] = &FWrite;
  Optimizations["fputs"] = &FPuts;
  Optimizations["fprintf"] = &FPrintF;
}


/// runOnFunction - Top level algorithm.
///
bool SimplifyLibCalls::runOnFunction(Function &F) {
  if (Optimizations.empty())
    InitOptimizations();
  
  const TargetData &TD = getAnalysis<TargetData>();
  
  IRBuilder<> Builder;

  bool Changed = false;
  for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB) {
    for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ) {
      // Ignore non-calls.
      CallInst *CI = dyn_cast<CallInst>(I++);
      if (!CI) continue;
      
      // Ignore indirect calls and calls to non-external functions.
      Function *Callee = CI->getCalledFunction();
      if (Callee == 0 || !Callee->isDeclaration() ||
          !(Callee->hasExternalLinkage() || Callee->hasDLLImportLinkage()))
        continue;
      
      // Ignore unknown calls.
      const char *CalleeName = Callee->getNameStart();
      StringMap<LibCallOptimization*>::iterator OMI =
        Optimizations.find(CalleeName, CalleeName+Callee->getNameLen());
      if (OMI == Optimizations.end()) continue;
      
      // Set the builder to the instruction after the call.
      Builder.SetInsertPoint(BB, I);
      
      // Try to optimize this call.
      Value *Result = OMI->second->OptimizeCall(CI, TD, Builder);
      if (Result == 0) continue;

      DEBUG(DOUT << "SimplifyLibCalls simplified: " << *CI;
            DOUT << "  into: " << *Result << "\n");
      
      // Something changed!
      Changed = true;
      ++NumSimplified;
      
      // Inspect the instruction after the call (which was potentially just
      // added) next.
      I = CI; ++I;
      
      if (CI != Result && !CI->use_empty()) {
        CI->replaceAllUsesWith(Result);
        if (!Result->hasName())
          Result->takeName(CI);
      }
      CI->eraseFromParent();
    }
  }
  return Changed;
}


// TODO:
//   Additional cases that we need to add to this file:
//
// cbrt:
//   * cbrt(expN(X))  -> expN(x/3)
//   * cbrt(sqrt(x))  -> pow(x,1/6)
//   * cbrt(sqrt(x))  -> pow(x,1/9)
//
// cos, cosf, cosl:
//   * cos(-x)  -> cos(x)
//
// exp, expf, expl:
//   * exp(log(x))  -> x
//
// log, logf, logl:
//   * log(exp(x))   -> x
//   * log(x**y)     -> y*log(x)
//   * log(exp(y))   -> y*log(e)
//   * log(exp2(y))  -> y*log(2)
//   * log(exp10(y)) -> y*log(10)
//   * log(sqrt(x))  -> 0.5*log(x)
//   * log(pow(x,y)) -> y*log(x)
//
// lround, lroundf, lroundl:
//   * lround(cnst) -> cnst'
//
// memcmp:
//   * memcmp(x,y,l)   -> cnst
//      (if all arguments are constant and strlen(x) <= l and strlen(y) <= l)
//
// memmove:
//   * memmove(d,s,l,a) -> memcpy(d,s,l,a)
//       (if s is a global constant array)
//
// pow, powf, powl:
//   * pow(exp(x),y)  -> exp(x*y)
//   * pow(sqrt(x),y) -> pow(x,y*0.5)
//   * pow(pow(x,y),z)-> pow(x,y*z)
//
// puts:
//   * puts("") -> putchar("\n")
//
// round, roundf, roundl:
//   * round(cnst) -> cnst'
//
// signbit:
//   * signbit(cnst) -> cnst'
//   * signbit(nncst) -> 0 (if pstv is a non-negative constant)
//
// sqrt, sqrtf, sqrtl:
//   * sqrt(expN(x))  -> expN(x*0.5)
//   * sqrt(Nroot(x)) -> pow(x,1/(2*N))
//   * sqrt(pow(x,y)) -> pow(|x|,y*0.5)
//
// stpcpy:
//   * stpcpy(str, "literal") ->
//           llvm.memcpy(str,"literal",strlen("literal")+1,1)
// strrchr:
//   * strrchr(s,c) -> reverse_offset_of_in(c,s)
//      (if c is a constant integer and s is a constant string)
//   * strrchr(s1,0) -> strchr(s1,0)
//
// strncat:
//   * strncat(x,y,0) -> x
//   * strncat(x,y,0) -> x (if strlen(y) = 0)
//   * strncat(x,y,l) -> strcat(x,y) (if y and l are constants an l > strlen(y))
//
// strncpy:
//   * strncpy(d,s,0) -> d
//   * strncpy(d,s,l) -> memcpy(d,s,l,1)
//      (if s and l are constants)
//
// strpbrk:
//   * strpbrk(s,a) -> offset_in_for(s,a)
//      (if s and a are both constant strings)
//   * strpbrk(s,"") -> 0
//   * strpbrk(s,a) -> strchr(s,a[0]) (if a is constant string of length 1)
//
// strspn, strcspn:
//   * strspn(s,a)   -> const_int (if both args are constant)
//   * strspn("",a)  -> 0
//   * strspn(s,"")  -> 0
//   * strcspn(s,a)  -> const_int (if both args are constant)
//   * strcspn("",a) -> 0
//   * strcspn(s,"") -> strlen(a)
//
// strstr:
//   * strstr(x,x)  -> x
//   * strstr(s1,s2) -> offset_of_s2_in(s1)
//       (if s1 and s2 are constant strings)
//
// tan, tanf, tanl:
//   * tan(atan(x)) -> x
//
// trunc, truncf, truncl:
//   * trunc(cnst) -> cnst'
//
//