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llvm-6502/lib/Transforms/IPO/SimplifyLibCalls.cpp

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//===- SimplifyLibCalls.cpp - Optimize specific well-known library calls --===//
//
// The LLVM Compiler Infrastructure
//
// This file was developed by Reid Spencer and is distributed under the
// University of Illinois Open Source License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements a module pass that applies a variety of small
// optimizations for calls to specific well-known function calls (e.g. runtime
// library functions). For example, a call to the function "exit(3)" that
// occurs within the main() function can be transformed into a simple "return 3"
// instruction. Any optimization that takes this form (replace call to library
// function with simpler code that provides the same result) belongs in this
// file.
//
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "simplify-libcalls"
#include "llvm/Constants.h"
#include "llvm/DerivedTypes.h"
#include "llvm/Instructions.h"
#include "llvm/Module.h"
#include "llvm/Pass.h"
#include "llvm/ADT/hash_map"
#include "llvm/ADT/Statistic.h"
#include "llvm/Config/config.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Support/Debug.h"
#include "llvm/Target/TargetData.h"
#include "llvm/Transforms/IPO.h"
using namespace llvm;
/// This statistic keeps track of the total number of library calls that have
/// been simplified regardless of which call it is.
STATISTIC(SimplifiedLibCalls, "Number of library calls simplified");
namespace {
// Forward declarations
class LibCallOptimization;
class SimplifyLibCalls;
/// This list is populated by the constructor for LibCallOptimization class.
/// Therefore all subclasses are registered here at static initialization time
/// and this list is what the SimplifyLibCalls pass uses to apply the individual
/// optimizations to the call sites.
/// @brief The list of optimizations deriving from LibCallOptimization
static LibCallOptimization *OptList = 0;
/// This class is the abstract base class for the set of optimizations that
/// corresponds to one library call. The SimplifyLibCalls pass will call the
/// ValidateCalledFunction method to ask the optimization if a given Function
/// is the kind that the optimization can handle. If the subclass returns true,
/// then SImplifyLibCalls will also call the OptimizeCall method to perform,
/// or attempt to perform, the optimization(s) for the library call. Otherwise,
/// OptimizeCall won't be called. Subclasses are responsible for providing the
/// name of the library call (strlen, strcpy, etc.) to the LibCallOptimization
/// constructor. This is used to efficiently select which call instructions to
/// optimize. The criteria for a "lib call" is "anything with well known
/// semantics", typically a library function that is defined by an international
/// standard. Because the semantics are well known, the optimizations can
/// generally short-circuit actually calling the function if there's a simpler
/// way (e.g. strlen(X) can be reduced to a constant if X is a constant global).
/// @brief Base class for library call optimizations
class VISIBILITY_HIDDEN LibCallOptimization {
LibCallOptimization **Prev, *Next;
const char *FunctionName; ///< Name of the library call we optimize
#ifndef NDEBUG
Statistic occurrences; ///< debug statistic (-debug-only=simplify-libcalls)
#endif
public:
/// The \p fname argument must be the name of the library function being
/// optimized by the subclass.
/// @brief Constructor that registers the optimization.
LibCallOptimization(const char *FName, const char *Description)
: FunctionName(FName) {
#ifndef NDEBUG
occurrences.construct("simplify-libcalls", Description);
#endif
// Register this optimizer in the list of optimizations.
Next = OptList;
OptList = this;
Prev = &OptList;
if (Next) Next->Prev = &Next;
}
/// getNext - All libcall optimizations are chained together into a list,
/// return the next one in the list.
LibCallOptimization *getNext() { return Next; }
/// @brief Deregister from the optlist
virtual ~LibCallOptimization() {
*Prev = Next;
if (Next) Next->Prev = Prev;
}
/// The implementation of this function in subclasses should determine if
/// \p F is suitable for the optimization. This method is called by
/// SimplifyLibCalls::runOnModule to short circuit visiting all the call
/// sites of such a function if that function is not suitable in the first
/// place. If the called function is suitabe, this method should return true;
/// false, otherwise. This function should also perform any lazy
/// initialization that the LibCallOptimization needs to do, if its to return
/// true. This avoids doing initialization until the optimizer is actually
/// going to be called upon to do some optimization.
/// @brief Determine if the function is suitable for optimization
virtual bool ValidateCalledFunction(
const Function* F, ///< The function that is the target of call sites
SimplifyLibCalls& SLC ///< The pass object invoking us
) = 0;
/// The implementations of this function in subclasses is the heart of the
/// SimplifyLibCalls algorithm. Sublcasses of this class implement
/// OptimizeCall to determine if (a) the conditions are right for optimizing
/// the call and (b) to perform the optimization. If an action is taken
/// against ci, the subclass is responsible for returning true and ensuring
/// that ci is erased from its parent.
/// @brief Optimize a call, if possible.
virtual bool OptimizeCall(
CallInst* ci, ///< The call instruction that should be optimized.
SimplifyLibCalls& SLC ///< The pass object invoking us
) = 0;
/// @brief Get the name of the library call being optimized
const char *getFunctionName() const { return FunctionName; }
bool ReplaceCallWith(CallInst *CI, Value *V) {
if (!CI->use_empty())
CI->replaceAllUsesWith(V);
CI->eraseFromParent();
return true;
}
/// @brief Called by SimplifyLibCalls to update the occurrences statistic.
void succeeded() {
#ifndef NDEBUG
DEBUG(++occurrences);
#endif
}
};
/// This class is an LLVM Pass that applies each of the LibCallOptimization
/// instances to all the call sites in a module, relatively efficiently. The
/// purpose of this pass is to provide optimizations for calls to well-known
/// functions with well-known semantics, such as those in the c library. The
/// class provides the basic infrastructure for handling runOnModule. Whenever
/// this pass finds a function call, it asks the appropriate optimizer to
/// validate the call (ValidateLibraryCall). If it is validated, then
/// the OptimizeCall method is also called.
/// @brief A ModulePass for optimizing well-known function calls.
class VISIBILITY_HIDDEN SimplifyLibCalls : public ModulePass {
public:
static char ID; // Pass identification, replacement for typeid
SimplifyLibCalls() : ModulePass((intptr_t)&ID) {}
/// We need some target data for accurate signature details that are
/// target dependent. So we require target data in our AnalysisUsage.
/// @brief Require TargetData from AnalysisUsage.
virtual void getAnalysisUsage(AnalysisUsage& Info) const {
// Ask that the TargetData analysis be performed before us so we can use
// the target data.
Info.addRequired<TargetData>();
}
/// For this pass, process all of the function calls in the module, calling
/// ValidateLibraryCall and OptimizeCall as appropriate.
/// @brief Run all the lib call optimizations on a Module.
virtual bool runOnModule(Module &M) {
reset(M);
bool result = false;
hash_map<std::string, LibCallOptimization*> OptznMap;
for (LibCallOptimization *Optzn = OptList; Optzn; Optzn = Optzn->getNext())
OptznMap[Optzn->getFunctionName()] = Optzn;
// The call optimizations can be recursive. That is, the optimization might
// generate a call to another function which can also be optimized. This way
// we make the LibCallOptimization instances very specific to the case they
// handle. It also means we need to keep running over the function calls in
// the module until we don't get any more optimizations possible.
bool found_optimization = false;
do {
found_optimization = false;
for (Module::iterator FI = M.begin(), FE = M.end(); FI != FE; ++FI) {
// All the "well-known" functions are external and have external linkage
// because they live in a runtime library somewhere and were (probably)
// not compiled by LLVM. So, we only act on external functions that
// have external or dllimport linkage and non-empty uses.
if (!FI->isDeclaration() ||
!(FI->hasExternalLinkage() || FI->hasDLLImportLinkage()) ||
FI->use_empty())
continue;
// Get the optimization class that pertains to this function
hash_map<std::string, LibCallOptimization*>::iterator OMI =
OptznMap.find(FI->getName());
if (OMI == OptznMap.end()) continue;
LibCallOptimization *CO = OMI->second;
// Make sure the called function is suitable for the optimization
if (!CO->ValidateCalledFunction(FI, *this))
continue;
// Loop over each of the uses of the function
for (Value::use_iterator UI = FI->use_begin(), UE = FI->use_end();
UI != UE ; ) {
// If the use of the function is a call instruction
if (CallInst* CI = dyn_cast<CallInst>(*UI++)) {
// Do the optimization on the LibCallOptimization.
if (CO->OptimizeCall(CI, *this)) {
++SimplifiedLibCalls;
found_optimization = result = true;
CO->succeeded();
}
}
}
}
} while (found_optimization);
return result;
}
/// @brief Return the *current* module we're working on.
Module* getModule() const { return M; }
/// @brief Return the *current* target data for the module we're working on.
TargetData* getTargetData() const { return TD; }
/// @brief Return the size_t type -- syntactic shortcut
const Type* getIntPtrType() const { return TD->getIntPtrType(); }
/// @brief Return a Function* for the putchar libcall
Constant *get_putchar() {
if (!putchar_func)
putchar_func =
M->getOrInsertFunction("putchar", Type::Int32Ty, Type::Int32Ty, NULL);
return putchar_func;
}
/// @brief Return a Function* for the puts libcall
Constant *get_puts() {
if (!puts_func)
puts_func = M->getOrInsertFunction("puts", Type::Int32Ty,
PointerType::getUnqual(Type::Int8Ty),
NULL);
return puts_func;
}
/// @brief Return a Function* for the fputc libcall
Constant *get_fputc(const Type* FILEptr_type) {
if (!fputc_func)
fputc_func = M->getOrInsertFunction("fputc", Type::Int32Ty, Type::Int32Ty,
FILEptr_type, NULL);
return fputc_func;
}
/// @brief Return a Function* for the fputs libcall
Constant *get_fputs(const Type* FILEptr_type) {
if (!fputs_func)
fputs_func = M->getOrInsertFunction("fputs", Type::Int32Ty,
PointerType::getUnqual(Type::Int8Ty),
FILEptr_type, NULL);
return fputs_func;
}
/// @brief Return a Function* for the fwrite libcall
Constant *get_fwrite(const Type* FILEptr_type) {
if (!fwrite_func)
fwrite_func = M->getOrInsertFunction("fwrite", TD->getIntPtrType(),
PointerType::getUnqual(Type::Int8Ty),
TD->getIntPtrType(),
TD->getIntPtrType(),
FILEptr_type, NULL);
return fwrite_func;
}
/// @brief Return a Function* for the sqrt libcall
Constant *get_sqrt() {
if (!sqrt_func)
sqrt_func = M->getOrInsertFunction("sqrt", Type::DoubleTy,
Type::DoubleTy, NULL);
return sqrt_func;
}
/// @brief Return a Function* for the strcpy libcall
Constant *get_strcpy() {
if (!strcpy_func)
strcpy_func = M->getOrInsertFunction("strcpy",
PointerType::getUnqual(Type::Int8Ty),
PointerType::getUnqual(Type::Int8Ty),
PointerType::getUnqual(Type::Int8Ty),
NULL);
return strcpy_func;
}
/// @brief Return a Function* for the strlen libcall
Constant *get_strlen() {
if (!strlen_func)
strlen_func = M->getOrInsertFunction("strlen", TD->getIntPtrType(),
PointerType::getUnqual(Type::Int8Ty),
NULL);
return strlen_func;
}
/// @brief Return a Function* for the memchr libcall
Constant *get_memchr() {
if (!memchr_func)
memchr_func = M->getOrInsertFunction("memchr",
PointerType::getUnqual(Type::Int8Ty),
PointerType::getUnqual(Type::Int8Ty),
Type::Int32Ty, TD->getIntPtrType(),
NULL);
return memchr_func;
}
/// @brief Return a Function* for the memcpy libcall
Constant *get_memcpy() {
if (!memcpy_func) {
const Type *SBP = PointerType::getUnqual(Type::Int8Ty);
const char *N = TD->getIntPtrType() == Type::Int32Ty ?
"llvm.memcpy.i32" : "llvm.memcpy.i64";
memcpy_func = M->getOrInsertFunction(N, Type::VoidTy, SBP, SBP,
TD->getIntPtrType(), Type::Int32Ty,
NULL);
}
return memcpy_func;
}
Constant *getUnaryFloatFunction(const char *Name, Constant *&Cache) {
if (!Cache)
Cache = M->getOrInsertFunction(Name, Type::FloatTy, Type::FloatTy, NULL);
return Cache;
}
Constant *get_floorf() { return getUnaryFloatFunction("floorf", floorf_func);}
Constant *get_ceilf() { return getUnaryFloatFunction( "ceilf", ceilf_func);}
Constant *get_roundf() { return getUnaryFloatFunction("roundf", roundf_func);}
Constant *get_rintf() { return getUnaryFloatFunction( "rintf", rintf_func);}
Constant *get_nearbyintf() { return getUnaryFloatFunction("nearbyintf",
nearbyintf_func); }
private:
/// @brief Reset our cached data for a new Module
void reset(Module& mod) {
M = &mod;
TD = &getAnalysis<TargetData>();
putchar_func = 0;
puts_func = 0;
fputc_func = 0;
fputs_func = 0;
fwrite_func = 0;
memcpy_func = 0;
memchr_func = 0;
sqrt_func = 0;
strcpy_func = 0;
strlen_func = 0;
floorf_func = 0;
ceilf_func = 0;
roundf_func = 0;
rintf_func = 0;
nearbyintf_func = 0;
}
private:
/// Caches for function pointers.
Constant *putchar_func, *puts_func;
Constant *fputc_func, *fputs_func, *fwrite_func;
Constant *memcpy_func, *memchr_func;
Constant *sqrt_func;
Constant *strcpy_func, *strlen_func;
Constant *floorf_func, *ceilf_func, *roundf_func;
Constant *rintf_func, *nearbyintf_func;
Module *M; ///< Cached Module
TargetData *TD; ///< Cached TargetData
};
char SimplifyLibCalls::ID = 0;
// Register the pass
RegisterPass<SimplifyLibCalls>
X("simplify-libcalls", "Simplify well-known library calls");
} // anonymous namespace
// The only public symbol in this file which just instantiates the pass object
ModulePass *llvm::createSimplifyLibCallsPass() {
return new SimplifyLibCalls();
}
// Classes below here, in the anonymous namespace, are all subclasses of the
// LibCallOptimization class, each implementing all optimizations possible for a
// single well-known library call. Each has a static singleton instance that
// auto registers it into the "optlist" global above.
namespace {
// Forward declare utility functions.
static bool GetConstantStringInfo(Value *V, std::string &Str);
static Value *CastToCStr(Value *V, Instruction *IP);
/// This LibCallOptimization will find instances of a call to "exit" that occurs
/// within the "main" function and change it to a simple "ret" instruction with
/// the same value passed to the exit function. When this is done, it splits the
/// basic block at the exit(3) call and deletes the call instruction.
/// @brief Replace calls to exit in main with a simple return
struct VISIBILITY_HIDDEN ExitInMainOptimization : public LibCallOptimization {
ExitInMainOptimization() : LibCallOptimization("exit",
"Number of 'exit' calls simplified") {}
// Make sure the called function looks like exit (int argument, int return
// type, external linkage, not varargs).
virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
return F->arg_size() >= 1 && F->arg_begin()->getType()->isInteger();
}
virtual bool OptimizeCall(CallInst* ci, SimplifyLibCalls& SLC) {
// To be careful, we check that the call to exit is coming from "main", that
// main has external linkage, and the return type of main and the argument
// to exit have the same type.
Function *from = ci->getParent()->getParent();
if (from->hasExternalLinkage())
if (from->getReturnType() == ci->getOperand(1)->getType())
if (from->getName() == "main") {
// Okay, time to actually do the optimization. First, get the basic
// block of the call instruction
BasicBlock* bb = ci->getParent();
// Create a return instruction that we'll replace the call with.
// Note that the argument of the return is the argument of the call
// instruction.
new ReturnInst(ci->getOperand(1), ci);
// Split the block at the call instruction which places it in a new
// basic block.
bb->splitBasicBlock(ci);
// The block split caused a branch instruction to be inserted into
// the end of the original block, right after the return instruction
// that we put there. That's not a valid block, so delete the branch
// instruction.
bb->getInstList().pop_back();
// Now we can finally get rid of the call instruction which now lives
// in the new basic block.
ci->eraseFromParent();
// Optimization succeeded, return true.
return true;
}
// We didn't pass the criteria for this optimization so return false
return false;
}
} ExitInMainOptimizer;
/// This LibCallOptimization will simplify a call to the strcat library
/// function. The simplification is possible only if the string being
/// concatenated is a constant array or a constant expression that results in
/// a constant string. In this case we can replace it with strlen + llvm.memcpy
/// of the constant string. Both of these calls are further reduced, if possible
/// on subsequent passes.
/// @brief Simplify the strcat library function.
struct VISIBILITY_HIDDEN StrCatOptimization : public LibCallOptimization {
public:
/// @brief Default constructor
StrCatOptimization() : LibCallOptimization("strcat",
"Number of 'strcat' calls simplified") {}
public:
/// @brief Make sure that the "strcat" function has the right prototype
virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
const FunctionType *FT = F->getFunctionType();
return FT->getNumParams() == 2 &&
FT->getReturnType() == PointerType::getUnqual(Type::Int8Ty) &&
FT->getParamType(0) == FT->getReturnType() &&
FT->getParamType(1) == FT->getReturnType();
}
/// @brief Optimize the strcat library function
virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
// Extract some information from the instruction
Value *Dst = CI->getOperand(1);
Value *Src = CI->getOperand(2);
// Extract the initializer (while making numerous checks) from the
// source operand of the call to strcat.
std::string SrcStr;
if (!GetConstantStringInfo(Src, SrcStr))
return false;
// Handle the simple, do-nothing case
if (SrcStr.empty())
return ReplaceCallWith(CI, Dst);
// We need to find the end of the destination string. That's where the
// memory is to be moved to. We just generate a call to strlen.
CallInst *DstLen = new CallInst(SLC.get_strlen(), Dst,
Dst->getName()+".len", CI);
// Now that we have the destination's length, we must index into the
// destination's pointer to get the actual memcpy destination (end of
// the string .. we're concatenating).
Dst = new GetElementPtrInst(Dst, DstLen, Dst->getName()+".indexed", CI);
// We have enough information to now generate the memcpy call to
// do the concatenation for us.
Value *Vals[] = {
Dst, Src,
ConstantInt::get(SLC.getIntPtrType(), SrcStr.size()+1), // copy nul byte.
ConstantInt::get(Type::Int32Ty, 1) // alignment
};
new CallInst(SLC.get_memcpy(), Vals, Vals + 4, "", CI);
return ReplaceCallWith(CI, Dst);
}
} StrCatOptimizer;
/// This LibCallOptimization will simplify a call to the strchr library
/// function. It optimizes out cases where the arguments are both constant
/// and the result can be determined statically.
/// @brief Simplify the strcmp library function.
struct VISIBILITY_HIDDEN StrChrOptimization : public LibCallOptimization {
public:
StrChrOptimization() : LibCallOptimization("strchr",
"Number of 'strchr' calls simplified") {}
/// @brief Make sure that the "strchr" function has the right prototype
virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
const FunctionType *FT = F->getFunctionType();
return FT->getNumParams() == 2 &&
FT->getReturnType() == PointerType::getUnqual(Type::Int8Ty) &&
FT->getParamType(0) == FT->getReturnType() &&
isa<IntegerType>(FT->getParamType(1));
}
/// @brief Perform the strchr optimizations
virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
// Check that the first argument to strchr is a constant array of sbyte.
std::string Str;
if (!GetConstantStringInfo(CI->getOperand(1), Str))
return false;
// If the second operand is not constant, just lower this to memchr since we
// know the length of the input string.
ConstantInt *CSI = dyn_cast<ConstantInt>(CI->getOperand(2));
if (!CSI) {
Value *Args[3] = {
CI->getOperand(1),
CI->getOperand(2),
ConstantInt::get(SLC.getIntPtrType(), Str.size()+1)
};
return ReplaceCallWith(CI, new CallInst(SLC.get_memchr(), Args, Args + 3,
CI->getName(), CI));
}
// strchr can find the nul character.
Str += '\0';
// Get the character we're looking for
char CharValue = CSI->getSExtValue();
// Compute the offset
uint64_t i = 0;
while (1) {
if (i == Str.size()) // Didn't find the char. strchr returns null.
return ReplaceCallWith(CI, Constant::getNullValue(CI->getType()));
// Did we find our match?
if (Str[i] == CharValue)
break;
++i;
}
// strchr(s+n,c) -> gep(s+n+i,c)
// (if c is a constant integer and s is a constant string)
Value *Idx = ConstantInt::get(Type::Int64Ty, i);
Value *GEP = new GetElementPtrInst(CI->getOperand(1), Idx,
CI->getOperand(1)->getName() +
".strchr", CI);
return ReplaceCallWith(CI, GEP);
}
} StrChrOptimizer;
/// This LibCallOptimization will simplify a call to the strcmp library
/// function. It optimizes out cases where one or both arguments are constant
/// and the result can be determined statically.
/// @brief Simplify the strcmp library function.
struct VISIBILITY_HIDDEN StrCmpOptimization : public LibCallOptimization {
public:
StrCmpOptimization() : LibCallOptimization("strcmp",
"Number of 'strcmp' calls simplified") {}
/// @brief Make sure that the "strcmp" function has the right prototype
virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
const FunctionType *FT = F->getFunctionType();
return FT->getReturnType() == Type::Int32Ty && FT->getNumParams() == 2 &&
FT->getParamType(0) == FT->getParamType(1) &&
FT->getParamType(0) == PointerType::getUnqual(Type::Int8Ty);
}
/// @brief Perform the strcmp optimization
virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
// First, check to see if src and destination are the same. If they are,
// then the optimization is to replace the CallInst with a constant 0
// because the call is a no-op.
Value *Str1P = CI->getOperand(1);
Value *Str2P = CI->getOperand(2);
if (Str1P == Str2P) // strcmp(x,x) -> 0
return ReplaceCallWith(CI, ConstantInt::get(CI->getType(), 0));
std::string Str1;
if (!GetConstantStringInfo(Str1P, Str1))
return false;
if (Str1.empty()) {
// strcmp("", x) -> *x
Value *V = new LoadInst(Str2P, CI->getName()+".load", CI);
V = new ZExtInst(V, CI->getType(), CI->getName()+".int", CI);
return ReplaceCallWith(CI, V);
}
std::string Str2;
if (!GetConstantStringInfo(Str2P, Str2))
return false;
if (Str2.empty()) {
// strcmp(x,"") -> *x
Value *V = new LoadInst(Str1P, CI->getName()+".load", CI);
V = new ZExtInst(V, CI->getType(), CI->getName()+".int", CI);
return ReplaceCallWith(CI, V);
}
// strcmp(x, y) -> cnst (if both x and y are constant strings)
int R = strcmp(Str1.c_str(), Str2.c_str());
return ReplaceCallWith(CI, ConstantInt::get(CI->getType(), R));
}
} StrCmpOptimizer;
/// This LibCallOptimization will simplify a call to the strncmp library
/// function. It optimizes out cases where one or both arguments are constant
/// and the result can be determined statically.
/// @brief Simplify the strncmp library function.
struct VISIBILITY_HIDDEN StrNCmpOptimization : public LibCallOptimization {
public:
StrNCmpOptimization() : LibCallOptimization("strncmp",
"Number of 'strncmp' calls simplified") {}
/// @brief Make sure that the "strncmp" function has the right prototype
virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
const FunctionType *FT = F->getFunctionType();
return FT->getReturnType() == Type::Int32Ty && FT->getNumParams() == 3 &&
FT->getParamType(0) == FT->getParamType(1) &&
FT->getParamType(0) == PointerType::getUnqual(Type::Int8Ty) &&
isa<IntegerType>(FT->getParamType(2));
return false;
}
/// @brief Perform the strncmp optimization
virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
// First, check to see if src and destination are the same. If they are,
// then the optimization is to replace the CallInst with a constant 0
// because the call is a no-op.
Value *Str1P = CI->getOperand(1);
Value *Str2P = CI->getOperand(2);
if (Str1P == Str2P) // strncmp(x,x, n) -> 0
return ReplaceCallWith(CI, ConstantInt::get(CI->getType(), 0));
// Check the length argument, if it is Constant zero then the strings are
// considered equal.
uint64_t Length;
if (ConstantInt *LengthArg = dyn_cast<ConstantInt>(CI->getOperand(3)))
Length = LengthArg->getZExtValue();
else
return false;
if (Length == 0) // strncmp(x,y,0) -> 0
return ReplaceCallWith(CI, ConstantInt::get(CI->getType(), 0));
std::string Str1;
if (!GetConstantStringInfo(Str1P, Str1))
return false;
if (Str1.empty()) {
// strncmp("", x, n) -> *x
Value *V = new LoadInst(Str2P, CI->getName()+".load", CI);
V = new ZExtInst(V, CI->getType(), CI->getName()+".int", CI);
return ReplaceCallWith(CI, V);
}
std::string Str2;
if (!GetConstantStringInfo(Str2P, Str2))
return false;
if (Str2.empty()) {
// strncmp(x, "", n) -> *x
Value *V = new LoadInst(Str1P, CI->getName()+".load", CI);
V = new ZExtInst(V, CI->getType(), CI->getName()+".int", CI);
return ReplaceCallWith(CI, V);
}
// strncmp(x, y, n) -> cnst (if both x and y are constant strings)
int R = strncmp(Str1.c_str(), Str2.c_str(), Length);
return ReplaceCallWith(CI, ConstantInt::get(CI->getType(), R));
}
} StrNCmpOptimizer;
/// This LibCallOptimization will simplify a call to the strcpy library
/// function. Two optimizations are possible:
/// (1) If src and dest are the same and not volatile, just return dest
/// (2) If the src is a constant then we can convert to llvm.memmove
/// @brief Simplify the strcpy library function.
struct VISIBILITY_HIDDEN StrCpyOptimization : public LibCallOptimization {
public:
StrCpyOptimization() : LibCallOptimization("strcpy",
"Number of 'strcpy' calls simplified") {}
/// @brief Make sure that the "strcpy" function has the right prototype
virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
const FunctionType *FT = F->getFunctionType();
return FT->getNumParams() == 2 &&
FT->getParamType(0) == FT->getParamType(1) &&
FT->getReturnType() == FT->getParamType(0) &&
FT->getParamType(0) == PointerType::getUnqual(Type::Int8Ty);
}
/// @brief Perform the strcpy optimization
virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
// First, check to see if src and destination are the same. If they are,
// then the optimization is to replace the CallInst with the destination
// because the call is a no-op. Note that this corresponds to the
// degenerate strcpy(X,X) case which should have "undefined" results
// according to the C specification. However, it occurs sometimes and
// we optimize it as a no-op.
Value *Dst = CI->getOperand(1);
Value *Src = CI->getOperand(2);
if (Dst == Src) {
// strcpy(x, x) -> x
return ReplaceCallWith(CI, Dst);
}
// Get the length of the constant string referenced by the Src operand.
std::string SrcStr;
if (!GetConstantStringInfo(Src, SrcStr))
return false;
// If the constant string's length is zero we can optimize this by just
// doing a store of 0 at the first byte of the destination
if (SrcStr.size() == 0) {
new StoreInst(ConstantInt::get(Type::Int8Ty, 0), Dst, CI);
return ReplaceCallWith(CI, Dst);
}
// We have enough information to now generate the memcpy call to
// do the concatenation for us.
Value *MemcpyOps[] = {
Dst, Src, // Pass length including nul byte.
ConstantInt::get(SLC.getIntPtrType(), SrcStr.size()+1),
ConstantInt::get(Type::Int32Ty, 1) // alignment
};
new CallInst(SLC.get_memcpy(), MemcpyOps, MemcpyOps + 4, "", CI);
return ReplaceCallWith(CI, Dst);
}
} StrCpyOptimizer;
/// This LibCallOptimization will simplify a call to the strlen library
/// function by replacing it with a constant value if the string provided to
/// it is a constant array.
/// @brief Simplify the strlen library function.
struct VISIBILITY_HIDDEN StrLenOptimization : public LibCallOptimization {
StrLenOptimization() : LibCallOptimization("strlen",
"Number of 'strlen' calls simplified") {}
/// @brief Make sure that the "strlen" function has the right prototype
virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
const FunctionType *FT = F->getFunctionType();
return FT->getNumParams() == 1 &&
FT->getParamType(0) == PointerType::getUnqual(Type::Int8Ty) &&
isa<IntegerType>(FT->getReturnType());
}
/// @brief Perform the strlen optimization
virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
// Make sure we're dealing with an sbyte* here.
Value *Src = CI->getOperand(1);
// Does the call to strlen have exactly one use?
if (CI->hasOneUse()) {
// Is that single use a icmp operator?
if (ICmpInst *Cmp = dyn_cast<ICmpInst>(CI->use_back()))
// Is it compared against a constant integer?
if (ConstantInt *Cst = dyn_cast<ConstantInt>(Cmp->getOperand(1))) {
// If its compared against length 0 with == or !=
if (Cst->getZExtValue() == 0 && Cmp->isEquality()) {
// strlen(x) != 0 -> *x != 0
// strlen(x) == 0 -> *x == 0
Value *V = new LoadInst(Src, Src->getName()+".first", CI);
V = new ICmpInst(Cmp->getPredicate(), V,
ConstantInt::get(Type::Int8Ty, 0),
Cmp->getName()+".strlen", CI);
Cmp->replaceAllUsesWith(V);
Cmp->eraseFromParent();
return ReplaceCallWith(CI, 0); // no uses.
}
}
}
// Get the length of the constant string operand
std::string Str;
if (!GetConstantStringInfo(Src, Str))
return false;
// strlen("xyz") -> 3 (for example)
return ReplaceCallWith(CI, ConstantInt::get(CI->getType(), Str.size()));
}
} StrLenOptimizer;
/// IsOnlyUsedInEqualsComparison - Return true if it only matters that the value
/// is equal or not-equal to zero.
static bool IsOnlyUsedInEqualsZeroComparison(Instruction *I) {
for (Value::use_iterator UI = I->use_begin(), E = I->use_end();
UI != E; ++UI) {
if (ICmpInst *IC = dyn_cast<ICmpInst>(*UI))
if (IC->isEquality())
if (Constant *C = dyn_cast<Constant>(IC->getOperand(1)))
if (C->isNullValue())
continue;
// Unknown instruction.
return false;
}
return true;
}
/// This memcmpOptimization will simplify a call to the memcmp library
/// function.
struct VISIBILITY_HIDDEN memcmpOptimization : public LibCallOptimization {
/// @brief Default Constructor
memcmpOptimization()
: LibCallOptimization("memcmp", "Number of 'memcmp' calls simplified") {}
/// @brief Make sure that the "memcmp" function has the right prototype
virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &TD) {
Function::const_arg_iterator AI = F->arg_begin();
if (F->arg_size() != 3 || !isa<PointerType>(AI->getType())) return false;
if (!isa<PointerType>((++AI)->getType())) return false;
if (!(++AI)->getType()->isInteger()) return false;
if (!F->getReturnType()->isInteger()) return false;
return true;
}
/// Because of alignment and instruction information that we don't have, we
/// leave the bulk of this to the code generators.
///
/// Note that we could do much more if we could force alignment on otherwise
/// small aligned allocas, or if we could indicate that loads have a small
/// alignment.
virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &TD) {
Value *LHS = CI->getOperand(1), *RHS = CI->getOperand(2);
// If the two operands are the same, return zero.
if (LHS == RHS) {
// memcmp(s,s,x) -> 0
return ReplaceCallWith(CI, Constant::getNullValue(CI->getType()));
}
// Make sure we have a constant length.
ConstantInt *LenC = dyn_cast<ConstantInt>(CI->getOperand(3));
if (!LenC) return false;
uint64_t Len = LenC->getZExtValue();
// If the length is zero, this returns 0.
switch (Len) {
case 0:
// memcmp(s1,s2,0) -> 0
return ReplaceCallWith(CI, Constant::getNullValue(CI->getType()));
case 1: {
// memcmp(S1,S2,1) -> *(ubyte*)S1 - *(ubyte*)S2
const Type *UCharPtr = PointerType::getUnqual(Type::Int8Ty);
CastInst *Op1Cast = CastInst::create(
Instruction::BitCast, LHS, UCharPtr, LHS->getName(), CI);
CastInst *Op2Cast = CastInst::create(
Instruction::BitCast, RHS, UCharPtr, RHS->getName(), CI);
Value *S1V = new LoadInst(Op1Cast, LHS->getName()+".val", CI);
Value *S2V = new LoadInst(Op2Cast, RHS->getName()+".val", CI);
Value *RV = BinaryOperator::createSub(S1V, S2V, CI->getName()+".diff",CI);
if (RV->getType() != CI->getType())
RV = CastInst::createIntegerCast(RV, CI->getType(), false,
RV->getName(), CI);
return ReplaceCallWith(CI, RV);
}
case 2:
if (IsOnlyUsedInEqualsZeroComparison(CI)) {
// TODO: IF both are aligned, use a short load/compare.
// memcmp(S1,S2,2) -> S1[0]-S2[0] | S1[1]-S2[1] iff only ==/!= 0 matters
const Type *UCharPtr = PointerType::getUnqual(Type::Int8Ty);
CastInst *Op1Cast = CastInst::create(
Instruction::BitCast, LHS, UCharPtr, LHS->getName(), CI);
CastInst *Op2Cast = CastInst::create(
Instruction::BitCast, RHS, UCharPtr, RHS->getName(), CI);
Value *S1V1 = new LoadInst(Op1Cast, LHS->getName()+".val1", CI);
Value *S2V1 = new LoadInst(Op2Cast, RHS->getName()+".val1", CI);
Value *D1 = BinaryOperator::createSub(S1V1, S2V1,
CI->getName()+".d1", CI);
Constant *One = ConstantInt::get(Type::Int32Ty, 1);
Value *G1 = new GetElementPtrInst(Op1Cast, One, "next1v", CI);
Value *G2 = new GetElementPtrInst(Op2Cast, One, "next2v", CI);
Value *S1V2 = new LoadInst(G1, LHS->getName()+".val2", CI);
Value *S2V2 = new LoadInst(G2, RHS->getName()+".val2", CI);
Value *D2 = BinaryOperator::createSub(S1V2, S2V2,
CI->getName()+".d1", CI);
Value *Or = BinaryOperator::createOr(D1, D2, CI->getName()+".res", CI);
if (Or->getType() != CI->getType())
Or = CastInst::createIntegerCast(Or, CI->getType(), false /*ZExt*/,
Or->getName(), CI);
return ReplaceCallWith(CI, Or);
}
break;
default:
break;
}
return false;
}
} memcmpOptimizer;
/// This LibCallOptimization will simplify a call to the memcpy library
/// function by expanding it out to a single store of size 0, 1, 2, 4, or 8
/// bytes depending on the length of the string and the alignment. Additional
/// optimizations are possible in code generation (sequence of immediate store)
/// @brief Simplify the memcpy library function.
struct VISIBILITY_HIDDEN LLVMMemCpyMoveOptzn : public LibCallOptimization {
LLVMMemCpyMoveOptzn(const char* fname, const char* desc)
: LibCallOptimization(fname, desc) {}
/// @brief Make sure that the "memcpy" function has the right prototype
virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& TD) {
// Just make sure this has 4 arguments per LLVM spec.
return (f->arg_size() == 4);
}
/// Because of alignment and instruction information that we don't have, we
/// leave the bulk of this to the code generators. The optimization here just
/// deals with a few degenerate cases where the length of the string and the
/// alignment match the sizes of our intrinsic types so we can do a load and
/// store instead of the memcpy call.
/// @brief Perform the memcpy optimization.
virtual bool OptimizeCall(CallInst* ci, SimplifyLibCalls& TD) {
// Make sure we have constant int values to work with
ConstantInt* LEN = dyn_cast<ConstantInt>(ci->getOperand(3));
if (!LEN)
return false;
ConstantInt* ALIGN = dyn_cast<ConstantInt>(ci->getOperand(4));
if (!ALIGN)
return false;
// If the length is larger than the alignment, we can't optimize
uint64_t len = LEN->getZExtValue();
uint64_t alignment = ALIGN->getZExtValue();
if (alignment == 0)
alignment = 1; // Alignment 0 is identity for alignment 1
if (len > alignment)
return false;
// Get the type we will cast to, based on size of the string
Value* dest = ci->getOperand(1);
Value* src = ci->getOperand(2);
const Type* castType = 0;
switch (len) {
case 0:
// memcpy(d,s,0,a) -> d
return ReplaceCallWith(ci, 0);
case 1: castType = Type::Int8Ty; break;
case 2: castType = Type::Int16Ty; break;
case 4: castType = Type::Int32Ty; break;
case 8: castType = Type::Int64Ty; break;
default:
return false;
}
// Cast source and dest to the right sized primitive and then load/store
CastInst* SrcCast = CastInst::create(Instruction::BitCast,
src, PointerType::getUnqual(castType), src->getName()+".cast", ci);
CastInst* DestCast = CastInst::create(Instruction::BitCast,
dest, PointerType::getUnqual(castType),dest->getName()+".cast", ci);
LoadInst* LI = new LoadInst(SrcCast,SrcCast->getName()+".val",ci);
new StoreInst(LI, DestCast, ci);
return ReplaceCallWith(ci, 0);
}
};
/// This LibCallOptimization will simplify a call to the memcpy/memmove library
/// functions.
LLVMMemCpyMoveOptzn LLVMMemCpyOptimizer32("llvm.memcpy.i32",
"Number of 'llvm.memcpy' calls simplified");
LLVMMemCpyMoveOptzn LLVMMemCpyOptimizer64("llvm.memcpy.i64",
"Number of 'llvm.memcpy' calls simplified");
LLVMMemCpyMoveOptzn LLVMMemMoveOptimizer32("llvm.memmove.i32",
"Number of 'llvm.memmove' calls simplified");
LLVMMemCpyMoveOptzn LLVMMemMoveOptimizer64("llvm.memmove.i64",
"Number of 'llvm.memmove' calls simplified");
/// This LibCallOptimization will simplify a call to the memset library
/// function by expanding it out to a single store of size 0, 1, 2, 4, or 8
/// bytes depending on the length argument.
struct VISIBILITY_HIDDEN LLVMMemSetOptimization : public LibCallOptimization {
/// @brief Default Constructor
LLVMMemSetOptimization(const char *Name) : LibCallOptimization(Name,
"Number of 'llvm.memset' calls simplified") {}
/// @brief Make sure that the "memset" function has the right prototype
virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &TD) {
// Just make sure this has 3 arguments per LLVM spec.
return F->arg_size() == 4;
}
/// Because of alignment and instruction information that we don't have, we
/// leave the bulk of this to the code generators. The optimization here just
/// deals with a few degenerate cases where the length parameter is constant
/// and the alignment matches the sizes of our intrinsic types so we can do
/// store instead of the memcpy call. Other calls are transformed into the
/// llvm.memset intrinsic.
/// @brief Perform the memset optimization.
virtual bool OptimizeCall(CallInst *ci, SimplifyLibCalls &TD) {
// Make sure we have constant int values to work with
ConstantInt* LEN = dyn_cast<ConstantInt>(ci->getOperand(3));
if (!LEN)
return false;
ConstantInt* ALIGN = dyn_cast<ConstantInt>(ci->getOperand(4));
if (!ALIGN)
return false;
// Extract the length and alignment
uint64_t len = LEN->getZExtValue();
uint64_t alignment = ALIGN->getZExtValue();
// Alignment 0 is identity for alignment 1
if (alignment == 0)
alignment = 1;
// If the length is zero, this is a no-op
if (len == 0) {
// memset(d,c,0,a) -> noop
return ReplaceCallWith(ci, 0);
}
// If the length is larger than the alignment, we can't optimize
if (len > alignment)
return false;
// Make sure we have a constant ubyte to work with so we can extract
// the value to be filled.
ConstantInt* FILL = dyn_cast<ConstantInt>(ci->getOperand(2));
if (!FILL)
return false;
if (FILL->getType() != Type::Int8Ty)
return false;
// memset(s,c,n) -> store s, c (for n=1,2,4,8)
// Extract the fill character
uint64_t fill_char = FILL->getZExtValue();
uint64_t fill_value = fill_char;
// Get the type we will cast to, based on size of memory area to fill, and
// and the value we will store there.
Value* dest = ci->getOperand(1);
const Type* castType = 0;
switch (len) {
case 1:
castType = Type::Int8Ty;
break;
case 2:
castType = Type::Int16Ty;
fill_value |= fill_char << 8;
break;
case 4:
castType = Type::Int32Ty;
fill_value |= fill_char << 8 | fill_char << 16 | fill_char << 24;
break;
case 8:
castType = Type::Int64Ty;
fill_value |= fill_char << 8 | fill_char << 16 | fill_char << 24;
fill_value |= fill_char << 32 | fill_char << 40 | fill_char << 48;
fill_value |= fill_char << 56;
break;
default:
return false;
}
// Cast dest to the right sized primitive and then load/store
CastInst* DestCast = new BitCastInst(dest, PointerType::getUnqual(castType),
dest->getName()+".cast", ci);
new StoreInst(ConstantInt::get(castType,fill_value),DestCast, ci);
return ReplaceCallWith(ci, 0);
}
};
LLVMMemSetOptimization MemSet32Optimizer("llvm.memset.i32");
LLVMMemSetOptimization MemSet64Optimizer("llvm.memset.i64");
/// This LibCallOptimization will simplify calls to the "pow" library
/// function. It looks for cases where the result of pow is well known and
/// substitutes the appropriate value.
/// @brief Simplify the pow library function.
struct VISIBILITY_HIDDEN PowOptimization : public LibCallOptimization {
public:
/// @brief Default Constructor
PowOptimization() : LibCallOptimization("pow",
"Number of 'pow' calls simplified") {}
/// @brief Make sure that the "pow" function has the right prototype
virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC){
// Just make sure this has 2 arguments
return (f->arg_size() == 2);
}
/// @brief Perform the pow optimization.
virtual bool OptimizeCall(CallInst *ci, SimplifyLibCalls &SLC) {
const Type *Ty = cast<Function>(ci->getOperand(0))->getReturnType();
if (Ty!=Type::FloatTy && Ty!=Type::DoubleTy)
return false; // FIXME long double not yet supported
Value* base = ci->getOperand(1);
Value* expn = ci->getOperand(2);
if (ConstantFP *Op1 = dyn_cast<ConstantFP>(base)) {
if (Op1->isExactlyValue(1.0)) // pow(1.0,x) -> 1.0
return ReplaceCallWith(ci, ConstantFP::get(Ty,
Ty==Type::FloatTy ? APFloat(1.0f) : APFloat(1.0)));
} else if (ConstantFP* Op2 = dyn_cast<ConstantFP>(expn)) {
if (Op2->getValueAPF().isZero()) {
// pow(x,0.0) -> 1.0
return ReplaceCallWith(ci, ConstantFP::get(Ty,
Ty==Type::FloatTy ? APFloat(1.0f) : APFloat(1.0)));
} else if (Op2->isExactlyValue(0.5)) {
// pow(x,0.5) -> sqrt(x)
CallInst* sqrt_inst = new CallInst(SLC.get_sqrt(), base,
ci->getName()+".pow",ci);
return ReplaceCallWith(ci, sqrt_inst);
} else if (Op2->isExactlyValue(1.0)) {
// pow(x,1.0) -> x
return ReplaceCallWith(ci, base);
} else if (Op2->isExactlyValue(-1.0)) {
// pow(x,-1.0) -> 1.0/x
Value *div_inst =
BinaryOperator::createFDiv(ConstantFP::get(Ty,
Ty==Type::FloatTy ? APFloat(1.0f) : APFloat(1.0)),
base, ci->getName()+".pow", ci);
return ReplaceCallWith(ci, div_inst);
}
}
return false; // opt failed
}
} PowOptimizer;
/// This LibCallOptimization will simplify calls to the "printf" library
/// function. It looks for cases where the result of printf is not used and the
/// operation can be reduced to something simpler.
/// @brief Simplify the printf library function.
struct VISIBILITY_HIDDEN PrintfOptimization : public LibCallOptimization {
public:
/// @brief Default Constructor
PrintfOptimization() : LibCallOptimization("printf",
"Number of 'printf' calls simplified") {}
/// @brief Make sure that the "printf" function has the right prototype
virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
// Just make sure this has at least 1 argument and returns an integer or
// void type.
const FunctionType *FT = F->getFunctionType();
return FT->getNumParams() >= 1 &&
(isa<IntegerType>(FT->getReturnType()) ||
FT->getReturnType() == Type::VoidTy);
}
/// @brief Perform the printf optimization.
virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
// All the optimizations depend on the length of the first argument and the
// fact that it is a constant string array. Check that now
std::string FormatStr;
if (!GetConstantStringInfo(CI->getOperand(1), FormatStr))
return false;
// If this is a simple constant string with no format specifiers that ends
// with a \n, turn it into a puts call.
if (FormatStr.empty()) {
// Tolerate printf's declared void.
if (CI->use_empty()) return ReplaceCallWith(CI, 0);
return ReplaceCallWith(CI, ConstantInt::get(CI->getType(), 0));
}
if (FormatStr.size() == 1) {
// Turn this into a putchar call, even if it is a %.
Value *V = ConstantInt::get(Type::Int32Ty, FormatStr[0]);
new CallInst(SLC.get_putchar(), V, "", CI);
if (CI->use_empty()) return ReplaceCallWith(CI, 0);
return ReplaceCallWith(CI, ConstantInt::get(CI->getType(), 1));
}
// Check to see if the format str is something like "foo\n", in which case
// we convert it to a puts call. We don't allow it to contain any format
// characters.
if (FormatStr[FormatStr.size()-1] == '\n' &&
FormatStr.find('%') == std::string::npos) {
// Create a string literal with no \n on it. We expect the constant merge
// pass to be run after this pass, to merge duplicate strings.
FormatStr.erase(FormatStr.end()-1);
Constant *Init = ConstantArray::get(FormatStr, true);
Constant *GV = new GlobalVariable(Init->getType(), true,
GlobalVariable::InternalLinkage,
Init, "str",
CI->getParent()->getParent()->getParent());
// Cast GV to be a pointer to char.
GV = ConstantExpr::getBitCast(GV, PointerType::getUnqual(Type::Int8Ty));
new CallInst(SLC.get_puts(), GV, "", CI);
if (CI->use_empty()) return ReplaceCallWith(CI, 0);
// The return value from printf includes the \n we just removed, so +1.
return ReplaceCallWith(CI,
ConstantInt::get(CI->getType(),
FormatStr.size()+1));
}
// Only support %c or "%s\n" for now.
if (FormatStr.size() < 2 || FormatStr[0] != '%')
return false;
// Get the second character and switch on its value
switch (FormatStr[1]) {
default: return false;
case 's':
if (FormatStr != "%s\n" || CI->getNumOperands() < 3 ||
// TODO: could insert strlen call to compute string length.
!CI->use_empty())
return false;
// printf("%s\n",str) -> puts(str)
new CallInst(SLC.get_puts(), CastToCStr(CI->getOperand(2), CI),
CI->getName(), CI);
return ReplaceCallWith(CI, 0);
case 'c': {
// printf("%c",c) -> putchar(c)
if (FormatStr.size() != 2 || CI->getNumOperands() < 3)
return false;
Value *V = CI->getOperand(2);
if (!isa<IntegerType>(V->getType()) ||
cast<IntegerType>(V->getType())->getBitWidth() > 32)
return false;
V = CastInst::createZExtOrBitCast(V, Type::Int32Ty, CI->getName()+".int",
CI);
new CallInst(SLC.get_putchar(), V, "", CI);
return ReplaceCallWith(CI, ConstantInt::get(CI->getType(), 1));
}
}
}
} PrintfOptimizer;
/// This LibCallOptimization will simplify calls to the "fprintf" library
/// function. It looks for cases where the result of fprintf is not used and the
/// operation can be reduced to something simpler.
/// @brief Simplify the fprintf library function.
struct VISIBILITY_HIDDEN FPrintFOptimization : public LibCallOptimization {
public:
/// @brief Default Constructor
FPrintFOptimization() : LibCallOptimization("fprintf",
"Number of 'fprintf' calls simplified") {}
/// @brief Make sure that the "fprintf" function has the right prototype
virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
const FunctionType *FT = F->getFunctionType();
return FT->getNumParams() == 2 && // two fixed arguments.
FT->getParamType(1) == PointerType::getUnqual(Type::Int8Ty) &&
isa<PointerType>(FT->getParamType(0)) &&
isa<IntegerType>(FT->getReturnType());
}
/// @brief Perform the fprintf optimization.
virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
// If the call has more than 3 operands, we can't optimize it
if (CI->getNumOperands() != 3 && CI->getNumOperands() != 4)
return false;
// All the optimizations depend on the format string.
std::string FormatStr;
if (!GetConstantStringInfo(CI->getOperand(2), FormatStr))
return false;
// If this is just a format string, turn it into fwrite.
if (CI->getNumOperands() == 3) {
for (unsigned i = 0, e = FormatStr.size(); i != e; ++i)
if (FormatStr[i] == '%')
return false; // we found a format specifier
// fprintf(file,fmt) -> fwrite(fmt,strlen(fmt),file)
const Type *FILEty = CI->getOperand(1)->getType();
Value *FWriteArgs[] = {
CI->getOperand(2),
ConstantInt::get(SLC.getIntPtrType(), FormatStr.size()),
ConstantInt::get(SLC.getIntPtrType(), 1),
CI->getOperand(1)
};
new CallInst(SLC.get_fwrite(FILEty), FWriteArgs, FWriteArgs + 4, CI->getName(), CI);
return ReplaceCallWith(CI, ConstantInt::get(CI->getType(),
FormatStr.size()));
}
// The remaining optimizations require the format string to be length 2:
// "%s" or "%c".
if (FormatStr.size() != 2 || FormatStr[0] != '%')
return false;
// Get the second character and switch on its value
switch (FormatStr[1]) {
case 'c': {
// fprintf(file,"%c",c) -> fputc(c,file)
const Type *FILETy = CI->getOperand(1)->getType();
Value *C = CastInst::createZExtOrBitCast(CI->getOperand(3), Type::Int32Ty,
CI->getName()+".int", CI);
SmallVector<Value *, 2> Args;
Args.push_back(C);
Args.push_back(CI->getOperand(1));
new CallInst(SLC.get_fputc(FILETy), Args.begin(), Args.end(), "", CI);
return ReplaceCallWith(CI, ConstantInt::get(CI->getType(), 1));
}
case 's': {
const Type *FILETy = CI->getOperand(1)->getType();
// If the result of the fprintf call is used, we can't do this.
// TODO: we should insert a strlen call.
if (!CI->use_empty())
return false;
// fprintf(file,"%s",str) -> fputs(str,file)
SmallVector<Value *, 2> Args;
Args.push_back(CastToCStr(CI->getOperand(3), CI));
Args.push_back(CI->getOperand(1));
new CallInst(SLC.get_fputs(FILETy), Args.begin(),
Args.end(), CI->getName(), CI);
return ReplaceCallWith(CI, 0);
}
default:
return false;
}
}
} FPrintFOptimizer;
/// This LibCallOptimization will simplify calls to the "sprintf" library
/// function. It looks for cases where the result of sprintf is not used and the
/// operation can be reduced to something simpler.
/// @brief Simplify the sprintf library function.
struct VISIBILITY_HIDDEN SPrintFOptimization : public LibCallOptimization {
public:
/// @brief Default Constructor
SPrintFOptimization() : LibCallOptimization("sprintf",
"Number of 'sprintf' calls simplified") {}
/// @brief Make sure that the "sprintf" function has the right prototype
virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
const FunctionType *FT = F->getFunctionType();
return FT->getNumParams() == 2 && // two fixed arguments.
FT->getParamType(1) == PointerType::getUnqual(Type::Int8Ty) &&
FT->getParamType(0) == FT->getParamType(1) &&
isa<IntegerType>(FT->getReturnType());
}
/// @brief Perform the sprintf optimization.
virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
// If the call has more than 3 operands, we can't optimize it
if (CI->getNumOperands() != 3 && CI->getNumOperands() != 4)
return false;
std::string FormatStr;
if (!GetConstantStringInfo(CI->getOperand(2), FormatStr))
return false;
if (CI->getNumOperands() == 3) {
// Make sure there's no % in the constant array
for (unsigned i = 0, e = FormatStr.size(); i != e; ++i)
if (FormatStr[i] == '%')
return false; // we found a format specifier
// sprintf(str,fmt) -> llvm.memcpy(str,fmt,strlen(fmt),1)
Value *MemCpyArgs[] = {
CI->getOperand(1), CI->getOperand(2),
ConstantInt::get(SLC.getIntPtrType(),
FormatStr.size()+1), // Copy the nul byte.
ConstantInt::get(Type::Int32Ty, 1)
};
new CallInst(SLC.get_memcpy(), MemCpyArgs, MemCpyArgs + 4, "", CI);
return ReplaceCallWith(CI, ConstantInt::get(CI->getType(),
FormatStr.size()));
}
// The remaining optimizations require the format string to be "%s" or "%c".
if (FormatStr.size() != 2 || FormatStr[0] != '%')
return false;
// Get the second character and switch on its value
switch (FormatStr[1]) {
case 'c': {
// sprintf(dest,"%c",chr) -> store chr, dest
Value *V = CastInst::createTruncOrBitCast(CI->getOperand(3),
Type::Int8Ty, "char", CI);
new StoreInst(V, CI->getOperand(1), CI);
Value *Ptr = new GetElementPtrInst(CI->getOperand(1),
ConstantInt::get(Type::Int32Ty, 1),
CI->getOperand(1)->getName()+".end",
CI);
new StoreInst(ConstantInt::get(Type::Int8Ty,0), Ptr, CI);
return ReplaceCallWith(CI, ConstantInt::get(Type::Int32Ty, 1));
}
case 's': {
// sprintf(dest,"%s",str) -> llvm.memcpy(dest, str, strlen(str)+1, 1)
Value *Len = new CallInst(SLC.get_strlen(),
CastToCStr(CI->getOperand(3), CI),
CI->getOperand(3)->getName()+".len", CI);
Value *UnincLen = Len;
Len = BinaryOperator::createAdd(Len, ConstantInt::get(Len->getType(), 1),
Len->getName()+"1", CI);
Value *MemcpyArgs[4] = {
CI->getOperand(1),
CastToCStr(CI->getOperand(3), CI),
Len,
ConstantInt::get(Type::Int32Ty, 1)
};
new CallInst(SLC.get_memcpy(), MemcpyArgs, MemcpyArgs + 4, "", CI);
// The strlen result is the unincremented number of bytes in the string.
if (!CI->use_empty()) {
if (UnincLen->getType() != CI->getType())
UnincLen = CastInst::createIntegerCast(UnincLen, CI->getType(), false,
Len->getName(), CI);
CI->replaceAllUsesWith(UnincLen);
}
return ReplaceCallWith(CI, 0);
}
}
return false;
}
} SPrintFOptimizer;
/// This LibCallOptimization will simplify calls to the "fputs" library
/// function. It looks for cases where the result of fputs is not used and the
/// operation can be reduced to something simpler.
/// @brief Simplify the fputs library function.
struct VISIBILITY_HIDDEN FPutsOptimization : public LibCallOptimization {
public:
/// @brief Default Constructor
FPutsOptimization() : LibCallOptimization("fputs",
"Number of 'fputs' calls simplified") {}
/// @brief Make sure that the "fputs" function has the right prototype
virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
// Just make sure this has 2 arguments
return F->arg_size() == 2;
}
/// @brief Perform the fputs optimization.
virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
// If the result is used, none of these optimizations work.
if (!CI->use_empty())
return false;
// All the optimizations depend on the length of the first argument and the
// fact that it is a constant string array. Check that now
std::string Str;
if (!GetConstantStringInfo(CI->getOperand(1), Str))
return false;
const Type *FILETy = CI->getOperand(2)->getType();
// fputs(s,F) -> fwrite(s,1,len,F) (if s is constant and strlen(s) > 1)
Value *FWriteParms[4] = {
CI->getOperand(1),
ConstantInt::get(SLC.getIntPtrType(), Str.size()),
ConstantInt::get(SLC.getIntPtrType(), 1),
CI->getOperand(2)
};
new CallInst(SLC.get_fwrite(FILETy), FWriteParms, FWriteParms + 4, "", CI);
return ReplaceCallWith(CI, 0); // Known to have no uses (see above).
}
} FPutsOptimizer;
/// This LibCallOptimization will simplify calls to the "fwrite" function.
struct VISIBILITY_HIDDEN FWriteOptimization : public LibCallOptimization {
public:
/// @brief Default Constructor
FWriteOptimization() : LibCallOptimization("fwrite",
"Number of 'fwrite' calls simplified") {}
/// @brief Make sure that the "fputs" function has the right prototype
virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
const FunctionType *FT = F->getFunctionType();
return FT->getNumParams() == 4 &&
FT->getParamType(0) == PointerType::getUnqual(Type::Int8Ty) &&
FT->getParamType(1) == FT->getParamType(2) &&
isa<IntegerType>(FT->getParamType(1)) &&
isa<PointerType>(FT->getParamType(3)) &&
isa<IntegerType>(FT->getReturnType());
}
virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
// Get the element size and count.
uint64_t EltSize, EltCount;
if (ConstantInt *C = dyn_cast<ConstantInt>(CI->getOperand(2)))
EltSize = C->getZExtValue();
else
return false;
if (ConstantInt *C = dyn_cast<ConstantInt>(CI->getOperand(3)))
EltCount = C->getZExtValue();
else
return false;
// If this is writing zero records, remove the call (it's a noop).
if (EltSize * EltCount == 0)
return ReplaceCallWith(CI, ConstantInt::get(CI->getType(), 0));
// If this is writing one byte, turn it into fputc.
if (EltSize == 1 && EltCount == 1) {
SmallVector<Value *, 2> Args;
// fwrite(s,1,1,F) -> fputc(s[0],F)
Value *Ptr = CI->getOperand(1);
Value *Val = new LoadInst(Ptr, Ptr->getName()+".byte", CI);
Args.push_back(new ZExtInst(Val, Type::Int32Ty, Val->getName()+".int", CI));
Args.push_back(CI->getOperand(4));
const Type *FILETy = CI->getOperand(4)->getType();
new CallInst(SLC.get_fputc(FILETy), Args.begin(), Args.end(), "", CI);
return ReplaceCallWith(CI, ConstantInt::get(CI->getType(), 1));
}
return false;
}
} FWriteOptimizer;
/// This LibCallOptimization will simplify calls to the "isdigit" library
/// function. It simply does range checks the parameter explicitly.
/// @brief Simplify the isdigit library function.
struct VISIBILITY_HIDDEN isdigitOptimization : public LibCallOptimization {
public:
isdigitOptimization() : LibCallOptimization("isdigit",
"Number of 'isdigit' calls simplified") {}
/// @brief Make sure that the "isdigit" function has the right prototype
virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC){
// Just make sure this has 1 argument
return (f->arg_size() == 1);
}
/// @brief Perform the toascii optimization.
virtual bool OptimizeCall(CallInst *ci, SimplifyLibCalls &SLC) {
if (ConstantInt* CI = dyn_cast<ConstantInt>(ci->getOperand(1))) {
// isdigit(c) -> 0 or 1, if 'c' is constant
uint64_t val = CI->getZExtValue();
if (val >= '0' && val <= '9')
return ReplaceCallWith(ci, ConstantInt::get(Type::Int32Ty, 1));
else
return ReplaceCallWith(ci, ConstantInt::get(Type::Int32Ty, 0));
}
// isdigit(c) -> (unsigned)c - '0' <= 9
CastInst* cast = CastInst::createIntegerCast(ci->getOperand(1),
Type::Int32Ty, false/*ZExt*/, ci->getOperand(1)->getName()+".uint", ci);
BinaryOperator* sub_inst = BinaryOperator::createSub(cast,
ConstantInt::get(Type::Int32Ty,0x30),
ci->getOperand(1)->getName()+".sub",ci);
ICmpInst* setcond_inst = new ICmpInst(ICmpInst::ICMP_ULE,sub_inst,
ConstantInt::get(Type::Int32Ty,9),
ci->getOperand(1)->getName()+".cmp",ci);
CastInst* c2 = new ZExtInst(setcond_inst, Type::Int32Ty,
ci->getOperand(1)->getName()+".isdigit", ci);
return ReplaceCallWith(ci, c2);
}
} isdigitOptimizer;
struct VISIBILITY_HIDDEN isasciiOptimization : public LibCallOptimization {
public:
isasciiOptimization()
: LibCallOptimization("isascii", "Number of 'isascii' calls simplified") {}
virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
return F->arg_size() == 1 && F->arg_begin()->getType()->isInteger() &&
F->getReturnType()->isInteger();
}
/// @brief Perform the isascii optimization.
virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
// isascii(c) -> (unsigned)c < 128
Value *V = CI->getOperand(1);
Value *Cmp = new ICmpInst(ICmpInst::ICMP_ULT, V,
ConstantInt::get(V->getType(), 128),
V->getName()+".isascii", CI);
if (Cmp->getType() != CI->getType())
Cmp = new ZExtInst(Cmp, CI->getType(), Cmp->getName(), CI);
return ReplaceCallWith(CI, Cmp);
}
} isasciiOptimizer;
/// This LibCallOptimization will simplify calls to the "toascii" library
/// function. It simply does the corresponding and operation to restrict the
/// range of values to the ASCII character set (0-127).
/// @brief Simplify the toascii library function.
struct VISIBILITY_HIDDEN ToAsciiOptimization : public LibCallOptimization {
public:
/// @brief Default Constructor
ToAsciiOptimization() : LibCallOptimization("toascii",
"Number of 'toascii' calls simplified") {}
/// @brief Make sure that the "fputs" function has the right prototype
virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC){
// Just make sure this has 2 arguments
return (f->arg_size() == 1);
}
/// @brief Perform the toascii optimization.
virtual bool OptimizeCall(CallInst *ci, SimplifyLibCalls &SLC) {
// toascii(c) -> (c & 0x7f)
Value *chr = ci->getOperand(1);
Value *and_inst = BinaryOperator::createAnd(chr,
ConstantInt::get(chr->getType(),0x7F),ci->getName()+".toascii",ci);
return ReplaceCallWith(ci, and_inst);
}
} ToAsciiOptimizer;
/// This LibCallOptimization will simplify calls to the "ffs" library
/// calls which find the first set bit in an int, long, or long long. The
/// optimization is to compute the result at compile time if the argument is
/// a constant.
/// @brief Simplify the ffs library function.
struct VISIBILITY_HIDDEN FFSOptimization : public LibCallOptimization {
protected:
/// @brief Subclass Constructor
FFSOptimization(const char* funcName, const char* description)
: LibCallOptimization(funcName, description) {}
public:
/// @brief Default Constructor
FFSOptimization() : LibCallOptimization("ffs",
"Number of 'ffs' calls simplified") {}
/// @brief Make sure that the "ffs" function has the right prototype
virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
// Just make sure this has 2 arguments
return F->arg_size() == 1 && F->getReturnType() == Type::Int32Ty;
}
/// @brief Perform the ffs optimization.
virtual bool OptimizeCall(CallInst *TheCall, SimplifyLibCalls &SLC) {
if (ConstantInt *CI = dyn_cast<ConstantInt>(TheCall->getOperand(1))) {
// ffs(cnst) -> bit#
// ffsl(cnst) -> bit#
// ffsll(cnst) -> bit#
uint64_t val = CI->getZExtValue();
int result = 0;
if (val) {
++result;
while ((val & 1) == 0) {
++result;
val >>= 1;
}
}
return ReplaceCallWith(TheCall, ConstantInt::get(Type::Int32Ty, result));
}
// ffs(x) -> x == 0 ? 0 : llvm.cttz(x)+1
// ffsl(x) -> x == 0 ? 0 : llvm.cttz(x)+1
// ffsll(x) -> x == 0 ? 0 : llvm.cttz(x)+1
const Type *ArgType = TheCall->getOperand(1)->getType();
const char *CTTZName;
assert(ArgType->getTypeID() == Type::IntegerTyID &&
"llvm.cttz argument is not an integer?");
unsigned BitWidth = cast<IntegerType>(ArgType)->getBitWidth();
if (BitWidth == 8)
CTTZName = "llvm.cttz.i8";
else if (BitWidth == 16)
CTTZName = "llvm.cttz.i16";
else if (BitWidth == 32)
CTTZName = "llvm.cttz.i32";
else {
assert(BitWidth == 64 && "Unknown bitwidth");
CTTZName = "llvm.cttz.i64";
}
Constant *F = SLC.getModule()->getOrInsertFunction(CTTZName, ArgType,
ArgType, NULL);
Value *V = CastInst::createIntegerCast(TheCall->getOperand(1), ArgType,
false/*ZExt*/, "tmp", TheCall);
Value *V2 = new CallInst(F, V, "tmp", TheCall);
V2 = CastInst::createIntegerCast(V2, Type::Int32Ty, false/*ZExt*/,
"tmp", TheCall);
V2 = BinaryOperator::createAdd(V2, ConstantInt::get(Type::Int32Ty, 1),
"tmp", TheCall);
Value *Cond = new ICmpInst(ICmpInst::ICMP_EQ, V,
Constant::getNullValue(V->getType()), "tmp",
TheCall);
V2 = new SelectInst(Cond, ConstantInt::get(Type::Int32Ty, 0), V2,
TheCall->getName(), TheCall);
return ReplaceCallWith(TheCall, V2);
}
} FFSOptimizer;
/// This LibCallOptimization will simplify calls to the "ffsl" library
/// calls. It simply uses FFSOptimization for which the transformation is
/// identical.
/// @brief Simplify the ffsl library function.
struct VISIBILITY_HIDDEN FFSLOptimization : public FFSOptimization {
public:
/// @brief Default Constructor
FFSLOptimization() : FFSOptimization("ffsl",
"Number of 'ffsl' calls simplified") {}
} FFSLOptimizer;
/// This LibCallOptimization will simplify calls to the "ffsll" library
/// calls. It simply uses FFSOptimization for which the transformation is
/// identical.
/// @brief Simplify the ffsl library function.
struct VISIBILITY_HIDDEN FFSLLOptimization : public FFSOptimization {
public:
/// @brief Default Constructor
FFSLLOptimization() : FFSOptimization("ffsll",
"Number of 'ffsll' calls simplified") {}
} FFSLLOptimizer;
/// This optimizes unary functions that take and return doubles.
struct UnaryDoubleFPOptimizer : public LibCallOptimization {
UnaryDoubleFPOptimizer(const char *Fn, const char *Desc)
: LibCallOptimization(Fn, Desc) {}
// Make sure that this function has the right prototype
virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
return F->arg_size() == 1 && F->arg_begin()->getType() == Type::DoubleTy &&
F->getReturnType() == Type::DoubleTy;
}
/// ShrinkFunctionToFloatVersion - If the input to this function is really a
/// float, strength reduce this to a float version of the function,
/// e.g. floor((double)FLT) -> (double)floorf(FLT). This can only be called
/// when the target supports the destination function and where there can be
/// no precision loss.
static bool ShrinkFunctionToFloatVersion(CallInst *CI, SimplifyLibCalls &SLC,
Constant *(SimplifyLibCalls::*FP)()){
if (FPExtInst *Cast = dyn_cast<FPExtInst>(CI->getOperand(1)))
if (Cast->getOperand(0)->getType() == Type::FloatTy) {
Value *New = new CallInst((SLC.*FP)(), Cast->getOperand(0),
CI->getName(), CI);
New = new FPExtInst(New, Type::DoubleTy, CI->getName(), CI);
CI->replaceAllUsesWith(New);
CI->eraseFromParent();
if (Cast->use_empty())
Cast->eraseFromParent();
return true;
}
return false;
}
};
struct VISIBILITY_HIDDEN FloorOptimization : public UnaryDoubleFPOptimizer {
FloorOptimization()
: UnaryDoubleFPOptimizer("floor", "Number of 'floor' calls simplified") {}
virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
#ifdef HAVE_FLOORF
// If this is a float argument passed in, convert to floorf.
if (ShrinkFunctionToFloatVersion(CI, SLC, &SimplifyLibCalls::get_floorf))
return true;
#endif
return false; // opt failed
}
} FloorOptimizer;
struct VISIBILITY_HIDDEN CeilOptimization : public UnaryDoubleFPOptimizer {
CeilOptimization()
: UnaryDoubleFPOptimizer("ceil", "Number of 'ceil' calls simplified") {}
virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
#ifdef HAVE_CEILF
// If this is a float argument passed in, convert to ceilf.
if (ShrinkFunctionToFloatVersion(CI, SLC, &SimplifyLibCalls::get_ceilf))
return true;
#endif
return false; // opt failed
}
} CeilOptimizer;
struct VISIBILITY_HIDDEN RoundOptimization : public UnaryDoubleFPOptimizer {
RoundOptimization()
: UnaryDoubleFPOptimizer("round", "Number of 'round' calls simplified") {}
virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
#ifdef HAVE_ROUNDF
// If this is a float argument passed in, convert to roundf.
if (ShrinkFunctionToFloatVersion(CI, SLC, &SimplifyLibCalls::get_roundf))
return true;
#endif
return false; // opt failed
}
} RoundOptimizer;
struct VISIBILITY_HIDDEN RintOptimization : public UnaryDoubleFPOptimizer {
RintOptimization()
: UnaryDoubleFPOptimizer("rint", "Number of 'rint' calls simplified") {}
virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
#ifdef HAVE_RINTF
// If this is a float argument passed in, convert to rintf.
if (ShrinkFunctionToFloatVersion(CI, SLC, &SimplifyLibCalls::get_rintf))
return true;
#endif
return false; // opt failed
}
} RintOptimizer;
struct VISIBILITY_HIDDEN NearByIntOptimization : public UnaryDoubleFPOptimizer {
NearByIntOptimization()
: UnaryDoubleFPOptimizer("nearbyint",
"Number of 'nearbyint' calls simplified") {}
virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
#ifdef HAVE_NEARBYINTF
// If this is a float argument passed in, convert to nearbyintf.
if (ShrinkFunctionToFloatVersion(CI, SLC,&SimplifyLibCalls::get_nearbyintf))
return true;
#endif
return false; // opt failed
}
} NearByIntOptimizer;
/// GetConstantStringInfo - This function computes the length of a
/// null-terminated constant array of integers. This function can't rely on the
/// size of the constant array because there could be a null terminator in the
/// middle of the array.
///
/// We also have to bail out if we find a non-integer constant initializer
/// of one of the elements or if there is no null-terminator. The logic
/// below checks each of these conditions and will return true only if all
/// conditions are met. If the conditions aren't met, this returns false.
///
/// If successful, the \p Array param is set to the constant array being
/// indexed, the \p Length parameter is set to the length of the null-terminated
/// string pointed to by V, the \p StartIdx value is set to the first
/// element of the Array that V points to, and true is returned.
static bool GetConstantStringInfo(Value *V, std::string &Str) {
// Look through noop bitcast instructions.
if (BitCastInst *BCI = dyn_cast<BitCastInst>(V)) {
if (BCI->getType() == BCI->getOperand(0)->getType())
return GetConstantStringInfo(BCI->getOperand(0), Str);
return false;
}
// If the value is not a GEP instruction nor a constant expression with a
// GEP instruction, then return false because ConstantArray can't occur
// any other way
User *GEP = 0;
if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(V)) {
GEP = GEPI;
} else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) {
if (CE->getOpcode() != Instruction::GetElementPtr)
return false;
GEP = CE;
} else {
return false;
}
// Make sure the GEP has exactly three arguments.
if (GEP->getNumOperands() != 3)
return false;
// Check to make sure that the first operand of the GEP is an integer and
// has value 0 so that we are sure we're indexing into the initializer.
if (ConstantInt *Idx = dyn_cast<ConstantInt>(GEP->getOperand(1))) {
if (!Idx->isZero())
return false;
} else
return false;
// If the second index isn't a ConstantInt, then this is a variable index
// into the array. If this occurs, we can't say anything meaningful about
// the string.
uint64_t StartIdx = 0;
if (ConstantInt *CI = dyn_cast<ConstantInt>(GEP->getOperand(2)))
StartIdx = CI->getZExtValue();
else
return false;
// The GEP instruction, constant or instruction, must reference a global
// variable that is a constant and is initialized. The referenced constant
// initializer is the array that we'll use for optimization.
GlobalVariable* GV = dyn_cast<GlobalVariable>(GEP->getOperand(0));
if (!GV || !GV->isConstant() || !GV->hasInitializer())
return false;
Constant *GlobalInit = GV->getInitializer();
// Handle the ConstantAggregateZero case
if (isa<ConstantAggregateZero>(GlobalInit)) {
// This is a degenerate case. The initializer is constant zero so the
// length of the string must be zero.
Str.clear();
return true;
}
// Must be a Constant Array
ConstantArray *Array = dyn_cast<ConstantArray>(GlobalInit);
if (!Array) return false;
// Get the number of elements in the array
uint64_t NumElts = Array->getType()->getNumElements();
// Traverse the constant array from StartIdx (derived above) which is
// the place the GEP refers to in the array.
for (unsigned i = StartIdx; i < NumElts; ++i) {
Constant *Elt = Array->getOperand(i);
ConstantInt *CI = dyn_cast<ConstantInt>(Elt);
if (!CI) // This array isn't suitable, non-int initializer.
return false;
if (CI->isZero())
return true; // we found end of string, success!
Str += (char)CI->getZExtValue();
}
return false; // The array isn't null terminated.
}
/// CastToCStr - Return V if it is an sbyte*, otherwise cast it to sbyte*,
/// inserting the cast before IP, and return the cast.
/// @brief Cast a value to a "C" string.
static Value *CastToCStr(Value *V, Instruction *IP) {
assert(isa<PointerType>(V->getType()) &&
"Can't cast non-pointer type to C string type");
const Type *SBPTy = PointerType::getUnqual(Type::Int8Ty);
if (V->getType() != SBPTy)
return new BitCastInst(V, SBPTy, V->getName(), IP);
return V;
}
// 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'
//
//
}
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