1 //===- SimplifyLibCalls.cpp - Optimize specific well-known library calls --===//
3 // The LLVM Compiler Infrastructure
5 // This file was developed by Reid Spencer and is distributed under the
6 // University of Illinois Open Source License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file implements a module pass that applies a variety of small
11 // optimizations for calls to specific well-known function calls (e.g. runtime
12 // library functions). For example, a call to the function "exit(3)" that
13 // occurs within the main() function can be transformed into a simple "return 3"
14 // instruction. Any optimization that takes this form (replace call to library
15 // function with simpler code that provides the same result) belongs in this
18 //===----------------------------------------------------------------------===//
20 #define DEBUG_TYPE "simplify-libcalls"
21 #include "llvm/Constants.h"
22 #include "llvm/DerivedTypes.h"
23 #include "llvm/Instructions.h"
24 #include "llvm/Module.h"
25 #include "llvm/Pass.h"
26 #include "llvm/ADT/hash_map"
27 #include "llvm/ADT/Statistic.h"
28 #include "llvm/Config/config.h"
29 #include "llvm/Support/Compiler.h"
30 #include "llvm/Support/Debug.h"
31 #include "llvm/Target/TargetData.h"
32 #include "llvm/Transforms/IPO.h"
35 /// This statistic keeps track of the total number of library calls that have
36 /// been simplified regardless of which call it is.
37 STATISTIC(SimplifiedLibCalls, "Number of library calls simplified");
40 // Forward declarations
41 class LibCallOptimization;
42 class SimplifyLibCalls;
44 /// This list is populated by the constructor for LibCallOptimization class.
45 /// Therefore all subclasses are registered here at static initialization time
46 /// and this list is what the SimplifyLibCalls pass uses to apply the individual
47 /// optimizations to the call sites.
48 /// @brief The list of optimizations deriving from LibCallOptimization
49 static LibCallOptimization *OptList = 0;
51 /// This class is the abstract base class for the set of optimizations that
52 /// corresponds to one library call. The SimplifyLibCalls pass will call the
53 /// ValidateCalledFunction method to ask the optimization if a given Function
54 /// is the kind that the optimization can handle. If the subclass returns true,
55 /// then SImplifyLibCalls will also call the OptimizeCall method to perform,
56 /// or attempt to perform, the optimization(s) for the library call. Otherwise,
57 /// OptimizeCall won't be called. Subclasses are responsible for providing the
58 /// name of the library call (strlen, strcpy, etc.) to the LibCallOptimization
59 /// constructor. This is used to efficiently select which call instructions to
60 /// optimize. The criteria for a "lib call" is "anything with well known
61 /// semantics", typically a library function that is defined by an international
62 /// standard. Because the semantics are well known, the optimizations can
63 /// generally short-circuit actually calling the function if there's a simpler
64 /// way (e.g. strlen(X) can be reduced to a constant if X is a constant global).
65 /// @brief Base class for library call optimizations
66 class VISIBILITY_HIDDEN LibCallOptimization {
67 LibCallOptimization **Prev, *Next;
68 const char *FunctionName; ///< Name of the library call we optimize
70 Statistic occurrences; ///< debug statistic (-debug-only=simplify-libcalls)
73 /// The \p fname argument must be the name of the library function being
74 /// optimized by the subclass.
75 /// @brief Constructor that registers the optimization.
76 LibCallOptimization(const char *FName, const char *Description)
77 : FunctionName(FName) {
80 occurrences.construct("simplify-libcalls", Description);
82 // Register this optimizer in the list of optimizations.
86 if (Next) Next->Prev = &Next;
89 /// getNext - All libcall optimizations are chained together into a list,
90 /// return the next one in the list.
91 LibCallOptimization *getNext() { return Next; }
93 /// @brief Deregister from the optlist
94 virtual ~LibCallOptimization() {
96 if (Next) Next->Prev = Prev;
99 /// The implementation of this function in subclasses should determine if
100 /// \p F is suitable for the optimization. This method is called by
101 /// SimplifyLibCalls::runOnModule to short circuit visiting all the call
102 /// sites of such a function if that function is not suitable in the first
103 /// place. If the called function is suitabe, this method should return true;
104 /// false, otherwise. This function should also perform any lazy
105 /// initialization that the LibCallOptimization needs to do, if its to return
106 /// true. This avoids doing initialization until the optimizer is actually
107 /// going to be called upon to do some optimization.
108 /// @brief Determine if the function is suitable for optimization
109 virtual bool ValidateCalledFunction(
110 const Function* F, ///< The function that is the target of call sites
111 SimplifyLibCalls& SLC ///< The pass object invoking us
114 /// The implementations of this function in subclasses is the heart of the
115 /// SimplifyLibCalls algorithm. Sublcasses of this class implement
116 /// OptimizeCall to determine if (a) the conditions are right for optimizing
117 /// the call and (b) to perform the optimization. If an action is taken
118 /// against ci, the subclass is responsible for returning true and ensuring
119 /// that ci is erased from its parent.
120 /// @brief Optimize a call, if possible.
121 virtual bool OptimizeCall(
122 CallInst* ci, ///< The call instruction that should be optimized.
123 SimplifyLibCalls& SLC ///< The pass object invoking us
126 /// @brief Get the name of the library call being optimized
127 const char *getFunctionName() const { return FunctionName; }
129 bool ReplaceCallWith(CallInst *CI, Value *V) {
130 if (!CI->use_empty())
131 CI->replaceAllUsesWith(V);
132 CI->eraseFromParent();
136 /// @brief Called by SimplifyLibCalls to update the occurrences statistic.
139 DEBUG(++occurrences);
144 /// This class is an LLVM Pass that applies each of the LibCallOptimization
145 /// instances to all the call sites in a module, relatively efficiently. The
146 /// purpose of this pass is to provide optimizations for calls to well-known
147 /// functions with well-known semantics, such as those in the c library. The
148 /// class provides the basic infrastructure for handling runOnModule. Whenever
149 /// this pass finds a function call, it asks the appropriate optimizer to
150 /// validate the call (ValidateLibraryCall). If it is validated, then
151 /// the OptimizeCall method is also called.
152 /// @brief A ModulePass for optimizing well-known function calls.
153 class VISIBILITY_HIDDEN SimplifyLibCalls : public ModulePass {
155 /// We need some target data for accurate signature details that are
156 /// target dependent. So we require target data in our AnalysisUsage.
157 /// @brief Require TargetData from AnalysisUsage.
158 virtual void getAnalysisUsage(AnalysisUsage& Info) const {
159 // Ask that the TargetData analysis be performed before us so we can use
161 Info.addRequired<TargetData>();
164 /// For this pass, process all of the function calls in the module, calling
165 /// ValidateLibraryCall and OptimizeCall as appropriate.
166 /// @brief Run all the lib call optimizations on a Module.
167 virtual bool runOnModule(Module &M) {
171 hash_map<std::string, LibCallOptimization*> OptznMap;
172 for (LibCallOptimization *Optzn = OptList; Optzn; Optzn = Optzn->getNext())
173 OptznMap[Optzn->getFunctionName()] = Optzn;
175 // The call optimizations can be recursive. That is, the optimization might
176 // generate a call to another function which can also be optimized. This way
177 // we make the LibCallOptimization instances very specific to the case they
178 // handle. It also means we need to keep running over the function calls in
179 // the module until we don't get any more optimizations possible.
180 bool found_optimization = false;
182 found_optimization = false;
183 for (Module::iterator FI = M.begin(), FE = M.end(); FI != FE; ++FI) {
184 // All the "well-known" functions are external and have external linkage
185 // because they live in a runtime library somewhere and were (probably)
186 // not compiled by LLVM. So, we only act on external functions that
187 // have external or dllimport linkage and non-empty uses.
188 if (!FI->isDeclaration() ||
189 !(FI->hasExternalLinkage() || FI->hasDLLImportLinkage()) ||
193 // Get the optimization class that pertains to this function
194 hash_map<std::string, LibCallOptimization*>::iterator OMI =
195 OptznMap.find(FI->getName());
196 if (OMI == OptznMap.end()) continue;
198 LibCallOptimization *CO = OMI->second;
200 // Make sure the called function is suitable for the optimization
201 if (!CO->ValidateCalledFunction(FI, *this))
204 // Loop over each of the uses of the function
205 for (Value::use_iterator UI = FI->use_begin(), UE = FI->use_end();
207 // If the use of the function is a call instruction
208 if (CallInst* CI = dyn_cast<CallInst>(*UI++)) {
209 // Do the optimization on the LibCallOptimization.
210 if (CO->OptimizeCall(CI, *this)) {
211 ++SimplifiedLibCalls;
212 found_optimization = result = true;
218 } while (found_optimization);
223 /// @brief Return the *current* module we're working on.
224 Module* getModule() const { return M; }
226 /// @brief Return the *current* target data for the module we're working on.
227 TargetData* getTargetData() const { return TD; }
229 /// @brief Return the size_t type -- syntactic shortcut
230 const Type* getIntPtrType() const { return TD->getIntPtrType(); }
232 /// @brief Return a Function* for the putchar libcall
233 Constant *get_putchar() {
236 M->getOrInsertFunction("putchar", Type::Int32Ty, Type::Int32Ty, NULL);
240 /// @brief Return a Function* for the puts libcall
241 Constant *get_puts() {
243 puts_func = M->getOrInsertFunction("puts", Type::Int32Ty,
244 PointerType::get(Type::Int8Ty),
249 /// @brief Return a Function* for the fputc libcall
250 Constant *get_fputc(const Type* FILEptr_type) {
252 fputc_func = M->getOrInsertFunction("fputc", Type::Int32Ty, Type::Int32Ty,
257 /// @brief Return a Function* for the fputs libcall
258 Constant *get_fputs(const Type* FILEptr_type) {
260 fputs_func = M->getOrInsertFunction("fputs", Type::Int32Ty,
261 PointerType::get(Type::Int8Ty),
266 /// @brief Return a Function* for the fwrite libcall
267 Constant *get_fwrite(const Type* FILEptr_type) {
269 fwrite_func = M->getOrInsertFunction("fwrite", TD->getIntPtrType(),
270 PointerType::get(Type::Int8Ty),
277 /// @brief Return a Function* for the sqrt libcall
278 Constant *get_sqrt() {
280 sqrt_func = M->getOrInsertFunction("sqrt", Type::DoubleTy,
281 Type::DoubleTy, NULL);
285 /// @brief Return a Function* for the strcpy libcall
286 Constant *get_strcpy() {
288 strcpy_func = M->getOrInsertFunction("strcpy",
289 PointerType::get(Type::Int8Ty),
290 PointerType::get(Type::Int8Ty),
291 PointerType::get(Type::Int8Ty),
296 /// @brief Return a Function* for the strlen libcall
297 Constant *get_strlen() {
299 strlen_func = M->getOrInsertFunction("strlen", TD->getIntPtrType(),
300 PointerType::get(Type::Int8Ty),
305 /// @brief Return a Function* for the memchr libcall
306 Constant *get_memchr() {
308 memchr_func = M->getOrInsertFunction("memchr",
309 PointerType::get(Type::Int8Ty),
310 PointerType::get(Type::Int8Ty),
311 Type::Int32Ty, TD->getIntPtrType(),
316 /// @brief Return a Function* for the memcpy libcall
317 Constant *get_memcpy() {
319 const Type *SBP = PointerType::get(Type::Int8Ty);
320 const char *N = TD->getIntPtrType() == Type::Int32Ty ?
321 "llvm.memcpy.i32" : "llvm.memcpy.i64";
322 memcpy_func = M->getOrInsertFunction(N, Type::VoidTy, SBP, SBP,
323 TD->getIntPtrType(), Type::Int32Ty,
329 Constant *getUnaryFloatFunction(const char *Name, Constant *&Cache) {
331 Cache = M->getOrInsertFunction(Name, Type::FloatTy, Type::FloatTy, NULL);
335 Constant *get_floorf() { return getUnaryFloatFunction("floorf", floorf_func);}
336 Constant *get_ceilf() { return getUnaryFloatFunction( "ceilf", ceilf_func);}
337 Constant *get_roundf() { return getUnaryFloatFunction("roundf", roundf_func);}
338 Constant *get_rintf() { return getUnaryFloatFunction( "rintf", rintf_func);}
339 Constant *get_nearbyintf() { return getUnaryFloatFunction("nearbyintf",
342 /// @brief Reset our cached data for a new Module
343 void reset(Module& mod) {
345 TD = &getAnalysis<TargetData>();
364 /// Caches for function pointers.
365 Constant *putchar_func, *puts_func;
366 Constant *fputc_func, *fputs_func, *fwrite_func;
367 Constant *memcpy_func, *memchr_func;
369 Constant *strcpy_func, *strlen_func;
370 Constant *floorf_func, *ceilf_func, *roundf_func;
371 Constant *rintf_func, *nearbyintf_func;
372 Module *M; ///< Cached Module
373 TargetData *TD; ///< Cached TargetData
377 RegisterPass<SimplifyLibCalls>
378 X("simplify-libcalls", "Simplify well-known library calls");
380 } // anonymous namespace
382 // The only public symbol in this file which just instantiates the pass object
383 ModulePass *llvm::createSimplifyLibCallsPass() {
384 return new SimplifyLibCalls();
387 // Classes below here, in the anonymous namespace, are all subclasses of the
388 // LibCallOptimization class, each implementing all optimizations possible for a
389 // single well-known library call. Each has a static singleton instance that
390 // auto registers it into the "optlist" global above.
393 // Forward declare utility functions.
394 static bool GetConstantStringInfo(Value *V, ConstantArray *&Array,
395 uint64_t &Length, uint64_t &StartIdx);
396 static Value *CastToCStr(Value *V, Instruction &IP);
398 /// This LibCallOptimization will find instances of a call to "exit" that occurs
399 /// within the "main" function and change it to a simple "ret" instruction with
400 /// the same value passed to the exit function. When this is done, it splits the
401 /// basic block at the exit(3) call and deletes the call instruction.
402 /// @brief Replace calls to exit in main with a simple return
403 struct VISIBILITY_HIDDEN ExitInMainOptimization : public LibCallOptimization {
404 ExitInMainOptimization() : LibCallOptimization("exit",
405 "Number of 'exit' calls simplified") {}
407 // Make sure the called function looks like exit (int argument, int return
408 // type, external linkage, not varargs).
409 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
410 return F->arg_size() >= 1 && F->arg_begin()->getType()->isInteger();
413 virtual bool OptimizeCall(CallInst* ci, SimplifyLibCalls& SLC) {
414 // To be careful, we check that the call to exit is coming from "main", that
415 // main has external linkage, and the return type of main and the argument
416 // to exit have the same type.
417 Function *from = ci->getParent()->getParent();
418 if (from->hasExternalLinkage())
419 if (from->getReturnType() == ci->getOperand(1)->getType())
420 if (from->getName() == "main") {
421 // Okay, time to actually do the optimization. First, get the basic
422 // block of the call instruction
423 BasicBlock* bb = ci->getParent();
425 // Create a return instruction that we'll replace the call with.
426 // Note that the argument of the return is the argument of the call
428 new ReturnInst(ci->getOperand(1), ci);
430 // Split the block at the call instruction which places it in a new
432 bb->splitBasicBlock(ci);
434 // The block split caused a branch instruction to be inserted into
435 // the end of the original block, right after the return instruction
436 // that we put there. That's not a valid block, so delete the branch
438 bb->getInstList().pop_back();
440 // Now we can finally get rid of the call instruction which now lives
441 // in the new basic block.
442 ci->eraseFromParent();
444 // Optimization succeeded, return true.
447 // We didn't pass the criteria for this optimization so return false
450 } ExitInMainOptimizer;
452 /// This LibCallOptimization will simplify a call to the strcat library
453 /// function. The simplification is possible only if the string being
454 /// concatenated is a constant array or a constant expression that results in
455 /// a constant string. In this case we can replace it with strlen + llvm.memcpy
456 /// of the constant string. Both of these calls are further reduced, if possible
457 /// on subsequent passes.
458 /// @brief Simplify the strcat library function.
459 struct VISIBILITY_HIDDEN StrCatOptimization : public LibCallOptimization {
461 /// @brief Default constructor
462 StrCatOptimization() : LibCallOptimization("strcat",
463 "Number of 'strcat' calls simplified") {}
467 /// @brief Make sure that the "strcat" function has the right prototype
468 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC){
469 if (f->getReturnType() == PointerType::get(Type::Int8Ty))
470 if (f->arg_size() == 2)
472 Function::const_arg_iterator AI = f->arg_begin();
473 if (AI++->getType() == PointerType::get(Type::Int8Ty))
474 if (AI->getType() == PointerType::get(Type::Int8Ty))
476 // Indicate this is a suitable call type.
483 /// @brief Optimize the strcat library function
484 virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
485 // Extract some information from the instruction
486 Value *Dst = CI->getOperand(1);
487 Value *Src = CI->getOperand(2);
489 // Extract the initializer (while making numerous checks) from the
490 // source operand of the call to strcat.
491 uint64_t SrcLength, StartIdx;
493 if (!GetConstantStringInfo(Src, Arr, SrcLength, StartIdx))
496 // Handle the simple, do-nothing case
498 return ReplaceCallWith(CI, Dst);
500 // We need to find the end of the destination string. That's where the
501 // memory is to be moved to. We just generate a call to strlen (further
502 // optimized in another pass).
503 CallInst *DstLen = new CallInst(SLC.get_strlen(), Dst,
504 Dst->getName()+".len", CI);
506 // Now that we have the destination's length, we must index into the
507 // destination's pointer to get the actual memcpy destination (end of
508 // the string .. we're concatenating).
509 Dst = new GetElementPtrInst(Dst, DstLen, Dst->getName()+".indexed", CI);
511 // We have enough information to now generate the memcpy call to
512 // do the concatenation for us.
515 ConstantInt::get(SLC.getIntPtrType(), SrcLength+1), // copy nul term.
516 ConstantInt::get(Type::Int32Ty, 1) // alignment
518 new CallInst(SLC.get_memcpy(), Vals, 4, "", CI);
520 return ReplaceCallWith(CI, Dst);
524 /// This LibCallOptimization will simplify a call to the strchr library
525 /// function. It optimizes out cases where the arguments are both constant
526 /// and the result can be determined statically.
527 /// @brief Simplify the strcmp library function.
528 struct VISIBILITY_HIDDEN StrChrOptimization : public LibCallOptimization {
530 StrChrOptimization() : LibCallOptimization("strchr",
531 "Number of 'strchr' calls simplified") {}
533 /// @brief Make sure that the "strchr" function has the right prototype
534 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
535 const FunctionType *FT = F->getFunctionType();
536 return FT->getNumParams() == 2 &&
537 FT->getReturnType() == PointerType::get(Type::Int8Ty) &&
538 FT->getParamType(0) == FT->getReturnType() &&
539 isa<IntegerType>(FT->getParamType(1));
542 /// @brief Perform the strchr optimizations
543 virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
544 // Check that the first argument to strchr is a constant array of sbyte.
545 // If it is, get the length and data, otherwise return false.
546 uint64_t StrLength, StartIdx;
547 ConstantArray *CA = 0;
548 if (!GetConstantStringInfo(CI->getOperand(1), CA, StrLength, StartIdx))
551 // If the second operand is not constant, just lower this to memchr since we
552 // know the length of the input string.
553 ConstantInt *CSI = dyn_cast<ConstantInt>(CI->getOperand(2));
558 ConstantInt::get(SLC.getIntPtrType(), StrLength+1)
560 return ReplaceCallWith(CI, new CallInst(SLC.get_memchr(), Args, 3,
564 // Get the character we're looking for
565 int64_t CharValue = CSI->getSExtValue();
567 if (StrLength == 0) {
568 // If the length of the string is zero, and we are searching for zero,
569 // return the input pointer.
571 return ReplaceCallWith(CI, CI->getOperand(1));
572 // Otherwise, char wasn't found.
573 return ReplaceCallWith(CI, Constant::getNullValue(CI->getType()));
576 // Compute the offset
579 assert(i <= StrLength && "Didn't find null terminator?");
580 if (ConstantInt *C = dyn_cast<ConstantInt>(CA->getOperand(i+StartIdx))) {
581 // Did we find our match?
582 if (C->getSExtValue() == CharValue)
584 if (C->isZero()) // We found the end of the string. strchr returns null.
585 return ReplaceCallWith(CI, Constant::getNullValue(CI->getType()));
590 // strchr(s+n,c) -> gep(s+n+i,c)
591 // (if c is a constant integer and s is a constant string)
592 Value *Idx = ConstantInt::get(Type::Int64Ty, i);
593 Value *GEP = new GetElementPtrInst(CI->getOperand(1), Idx,
594 CI->getOperand(1)->getName() +
596 return ReplaceCallWith(CI, GEP);
600 /// This LibCallOptimization will simplify a call to the strcmp library
601 /// function. It optimizes out cases where one or both arguments are constant
602 /// and the result can be determined statically.
603 /// @brief Simplify the strcmp library function.
604 struct VISIBILITY_HIDDEN StrCmpOptimization : public LibCallOptimization {
606 StrCmpOptimization() : LibCallOptimization("strcmp",
607 "Number of 'strcmp' calls simplified") {}
609 /// @brief Make sure that the "strcmp" function has the right prototype
610 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
611 const FunctionType *FT = F->getFunctionType();
612 return FT->getReturnType() == Type::Int32Ty && FT->getNumParams() == 2 &&
613 FT->getParamType(0) == FT->getParamType(1) &&
614 FT->getParamType(0) == PointerType::get(Type::Int8Ty);
617 /// @brief Perform the strcmp optimization
618 virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
619 // First, check to see if src and destination are the same. If they are,
620 // then the optimization is to replace the CallInst with a constant 0
621 // because the call is a no-op.
622 Value *Str1P = CI->getOperand(1);
623 Value *Str2P = CI->getOperand(2);
624 if (Str1P == Str2P) // strcmp(x,x) -> 0
625 return ReplaceCallWith(CI, ConstantInt::get(CI->getType(), 0));
627 uint64_t Str1Len, Str1StartIdx;
629 bool Str1IsCst = GetConstantStringInfo(Str1P, A1, Str1Len, Str1StartIdx);
630 if (Str1IsCst && Str1Len == 0) {
631 // strcmp("", x) -> *x
632 Value *V = new LoadInst(Str2P, CI->getName()+".load", CI);
633 V = new ZExtInst(V, CI->getType(), CI->getName()+".int", CI);
634 return ReplaceCallWith(CI, V);
637 uint64_t Str2Len, Str2StartIdx;
639 bool Str2IsCst = GetConstantStringInfo(Str2P, A2, Str2Len, Str2StartIdx);
640 if (Str2IsCst && Str2Len == 0) {
641 // strcmp(x,"") -> *x
642 Value *V = new LoadInst(Str1P, CI->getName()+".load", CI);
643 V = new ZExtInst(V, CI->getType(), CI->getName()+".int", CI);
644 return ReplaceCallWith(CI, V);
647 if (Str1IsCst && Str2IsCst && A1->isCString() && A2->isCString()) {
648 // strcmp(x, y) -> cnst (if both x and y are constant strings)
649 std::string S1 = A1->getAsString();
650 std::string S2 = A2->getAsString();
651 int R = strcmp(S1.c_str()+Str1StartIdx, S2.c_str()+Str2StartIdx);
652 return ReplaceCallWith(CI, ConstantInt::get(CI->getType(), R));
658 /// This LibCallOptimization will simplify a call to the strncmp library
659 /// function. It optimizes out cases where one or both arguments are constant
660 /// and the result can be determined statically.
661 /// @brief Simplify the strncmp library function.
662 struct VISIBILITY_HIDDEN StrNCmpOptimization : public LibCallOptimization {
664 StrNCmpOptimization() : LibCallOptimization("strncmp",
665 "Number of 'strncmp' calls simplified") {}
667 /// @brief Make sure that the "strncmp" function has the right prototype
668 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
669 const FunctionType *FT = F->getFunctionType();
670 return FT->getReturnType() == Type::Int32Ty && FT->getNumParams() == 3 &&
671 FT->getParamType(0) == FT->getParamType(1) &&
672 FT->getParamType(0) == PointerType::get(Type::Int8Ty) &&
673 isa<IntegerType>(FT->getParamType(2));
677 /// @brief Perform the strncmp optimization
678 virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
679 // First, check to see if src and destination are the same. If they are,
680 // then the optimization is to replace the CallInst with a constant 0
681 // because the call is a no-op.
682 Value *Str1P = CI->getOperand(1);
683 Value *Str2P = CI->getOperand(2);
684 if (Str1P == Str2P) // strncmp(x,x) -> 0
685 return ReplaceCallWith(CI, ConstantInt::get(CI->getType(), 0));
687 // Check the length argument, if it is Constant zero then the strings are
690 if (ConstantInt *LengthArg = dyn_cast<ConstantInt>(CI->getOperand(3)))
691 Length = LengthArg->getZExtValue();
696 // strncmp(x,y,0) -> 0
697 return ReplaceCallWith(CI, ConstantInt::get(CI->getType(), 0));
700 uint64_t Str1Len, Str1StartIdx;
702 bool Str1IsCst = GetConstantStringInfo(Str1P, A1, Str1Len, Str1StartIdx);
703 if (Str1IsCst && Str1Len == 0) {
704 // strncmp("", x) -> *x
705 Value *V = new LoadInst(Str2P, CI->getName()+".load", CI);
706 V = new ZExtInst(V, CI->getType(), CI->getName()+".int", CI);
707 return ReplaceCallWith(CI, V);
710 uint64_t Str2Len, Str2StartIdx;
712 bool Str2IsCst = GetConstantStringInfo(Str2P, A2, Str2Len, Str2StartIdx);
713 if (Str2IsCst && Str2Len == 0) {
714 // strncmp(x,"") -> *x
715 Value *V = new LoadInst(Str1P, CI->getName()+".load", CI);
716 V = new ZExtInst(V, CI->getType(), CI->getName()+".int", CI);
717 return ReplaceCallWith(CI, V);
720 if (Str1IsCst && Str2IsCst && A1->isCString() &&
722 // strncmp(x, y) -> cnst (if both x and y are constant strings)
723 std::string S1 = A1->getAsString();
724 std::string S2 = A2->getAsString();
725 int R = strncmp(S1.c_str()+Str1StartIdx, S2.c_str()+Str2StartIdx, Length);
726 return ReplaceCallWith(CI, ConstantInt::get(CI->getType(), R));
732 /// This LibCallOptimization will simplify a call to the strcpy library
733 /// function. Two optimizations are possible:
734 /// (1) If src and dest are the same and not volatile, just return dest
735 /// (2) If the src is a constant then we can convert to llvm.memmove
736 /// @brief Simplify the strcpy library function.
737 struct VISIBILITY_HIDDEN StrCpyOptimization : public LibCallOptimization {
739 StrCpyOptimization() : LibCallOptimization("strcpy",
740 "Number of 'strcpy' calls simplified") {}
742 /// @brief Make sure that the "strcpy" function has the right prototype
743 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
744 const FunctionType *FT = F->getFunctionType();
745 return FT->getNumParams() == 2 &&
746 FT->getParamType(0) == FT->getParamType(1) &&
747 FT->getReturnType() == FT->getParamType(0) &&
748 FT->getParamType(0) == PointerType::get(Type::Int8Ty);
751 /// @brief Perform the strcpy optimization
752 virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
753 // First, check to see if src and destination are the same. If they are,
754 // then the optimization is to replace the CallInst with the destination
755 // because the call is a no-op. Note that this corresponds to the
756 // degenerate strcpy(X,X) case which should have "undefined" results
757 // according to the C specification. However, it occurs sometimes and
758 // we optimize it as a no-op.
759 Value *Dst = CI->getOperand(1);
760 Value *Src = CI->getOperand(2);
763 return ReplaceCallWith(CI, Dst);
766 // Get the length of the constant string referenced by the Src operand.
767 uint64_t SrcLen, SrcStartIdx;
768 ConstantArray *SrcArr;
769 if (!GetConstantStringInfo(Src, SrcArr, SrcLen, SrcStartIdx))
772 // If the constant string's length is zero we can optimize this by just
773 // doing a store of 0 at the first byte of the destination
775 new StoreInst(ConstantInt::get(Type::Int8Ty, 0), Dst, CI);
776 return ReplaceCallWith(CI, Dst);
779 // We have enough information to now generate the memcpy call to
780 // do the concatenation for us.
781 Value *MemcpyOps[] = {
783 ConstantInt::get(SLC.getIntPtrType(), SrcLen), // length including nul.
784 ConstantInt::get(Type::Int32Ty, 1) // alignment
786 new CallInst(SLC.get_memcpy(), MemcpyOps, 4, "", CI);
788 return ReplaceCallWith(CI, Dst);
792 /// This LibCallOptimization will simplify a call to the strlen library
793 /// function by replacing it with a constant value if the string provided to
794 /// it is a constant array.
795 /// @brief Simplify the strlen library function.
796 struct VISIBILITY_HIDDEN StrLenOptimization : public LibCallOptimization {
797 StrLenOptimization() : LibCallOptimization("strlen",
798 "Number of 'strlen' calls simplified") {}
800 /// @brief Make sure that the "strlen" function has the right prototype
801 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
802 if (F->getReturnType() == SLC.getTargetData()->getIntPtrType())
803 if (F->arg_size() == 1)
804 if (Function::const_arg_iterator AI = F->arg_begin())
805 if (AI->getType() == PointerType::get(Type::Int8Ty))
810 /// @brief Perform the strlen optimization
811 virtual bool OptimizeCall(CallInst* ci, SimplifyLibCalls& SLC)
813 // Make sure we're dealing with an sbyte* here.
814 Value* str = ci->getOperand(1);
815 if (str->getType() != PointerType::get(Type::Int8Ty))
818 // Does the call to strlen have exactly one use?
820 // Is that single use a icmp operator?
821 if (ICmpInst* bop = dyn_cast<ICmpInst>(ci->use_back()))
822 // Is it compared against a constant integer?
823 if (ConstantInt* CI = dyn_cast<ConstantInt>(bop->getOperand(1)))
825 // Get the value the strlen result is compared to
826 uint64_t val = CI->getZExtValue();
828 // If its compared against length 0 with == or !=
830 (bop->getPredicate() == ICmpInst::ICMP_EQ ||
831 bop->getPredicate() == ICmpInst::ICMP_NE))
833 // strlen(x) != 0 -> *x != 0
834 // strlen(x) == 0 -> *x == 0
835 LoadInst* load = new LoadInst(str,str->getName()+".first",ci);
836 ICmpInst* rbop = new ICmpInst(bop->getPredicate(), load,
837 ConstantInt::get(Type::Int8Ty,0),
838 bop->getName()+".strlen", ci);
839 bop->replaceAllUsesWith(rbop);
840 bop->eraseFromParent();
841 ci->eraseFromParent();
846 // Get the length of the constant string operand
847 uint64_t len = 0, StartIdx;
849 if (!GetConstantStringInfo(ci->getOperand(1), A, len, StartIdx))
852 // strlen("xyz") -> 3 (for example)
853 const Type *Ty = SLC.getTargetData()->getIntPtrType();
854 return ReplaceCallWith(ci, ConstantInt::get(Ty, len));
858 /// IsOnlyUsedInEqualsComparison - Return true if it only matters that the value
859 /// is equal or not-equal to zero.
860 static bool IsOnlyUsedInEqualsZeroComparison(Instruction *I) {
861 for (Value::use_iterator UI = I->use_begin(), E = I->use_end();
863 Instruction *User = cast<Instruction>(*UI);
864 if (ICmpInst *IC = dyn_cast<ICmpInst>(User)) {
865 if ((IC->getPredicate() == ICmpInst::ICMP_NE ||
866 IC->getPredicate() == ICmpInst::ICMP_EQ) &&
867 isa<Constant>(IC->getOperand(1)) &&
868 cast<Constant>(IC->getOperand(1))->isNullValue())
870 } else if (CastInst *CI = dyn_cast<CastInst>(User))
871 if (CI->getType() == Type::Int1Ty)
873 // Unknown instruction.
879 /// This memcmpOptimization will simplify a call to the memcmp library
881 struct VISIBILITY_HIDDEN memcmpOptimization : public LibCallOptimization {
882 /// @brief Default Constructor
884 : LibCallOptimization("memcmp", "Number of 'memcmp' calls simplified") {}
886 /// @brief Make sure that the "memcmp" function has the right prototype
887 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &TD) {
888 Function::const_arg_iterator AI = F->arg_begin();
889 if (F->arg_size() != 3 || !isa<PointerType>(AI->getType())) return false;
890 if (!isa<PointerType>((++AI)->getType())) return false;
891 if (!(++AI)->getType()->isInteger()) return false;
892 if (!F->getReturnType()->isInteger()) return false;
896 /// Because of alignment and instruction information that we don't have, we
897 /// leave the bulk of this to the code generators.
899 /// Note that we could do much more if we could force alignment on otherwise
900 /// small aligned allocas, or if we could indicate that loads have a small
902 virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &TD) {
903 Value *LHS = CI->getOperand(1), *RHS = CI->getOperand(2);
905 // If the two operands are the same, return zero.
907 // memcmp(s,s,x) -> 0
908 return ReplaceCallWith(CI, Constant::getNullValue(CI->getType()));
911 // Make sure we have a constant length.
912 ConstantInt *LenC = dyn_cast<ConstantInt>(CI->getOperand(3));
913 if (!LenC) return false;
914 uint64_t Len = LenC->getZExtValue();
916 // If the length is zero, this returns 0.
919 // memcmp(s1,s2,0) -> 0
920 return ReplaceCallWith(CI, Constant::getNullValue(CI->getType()));
922 // memcmp(S1,S2,1) -> *(ubyte*)S1 - *(ubyte*)S2
923 const Type *UCharPtr = PointerType::get(Type::Int8Ty);
924 CastInst *Op1Cast = CastInst::create(
925 Instruction::BitCast, LHS, UCharPtr, LHS->getName(), CI);
926 CastInst *Op2Cast = CastInst::create(
927 Instruction::BitCast, RHS, UCharPtr, RHS->getName(), CI);
928 Value *S1V = new LoadInst(Op1Cast, LHS->getName()+".val", CI);
929 Value *S2V = new LoadInst(Op2Cast, RHS->getName()+".val", CI);
930 Value *RV = BinaryOperator::createSub(S1V, S2V, CI->getName()+".diff",CI);
931 if (RV->getType() != CI->getType())
932 RV = CastInst::createIntegerCast(RV, CI->getType(), false,
934 return ReplaceCallWith(CI, RV);
937 if (IsOnlyUsedInEqualsZeroComparison(CI)) {
938 // TODO: IF both are aligned, use a short load/compare.
940 // memcmp(S1,S2,2) -> S1[0]-S2[0] | S1[1]-S2[1] iff only ==/!= 0 matters
941 const Type *UCharPtr = PointerType::get(Type::Int8Ty);
942 CastInst *Op1Cast = CastInst::create(
943 Instruction::BitCast, LHS, UCharPtr, LHS->getName(), CI);
944 CastInst *Op2Cast = CastInst::create(
945 Instruction::BitCast, RHS, UCharPtr, RHS->getName(), CI);
946 Value *S1V1 = new LoadInst(Op1Cast, LHS->getName()+".val1", CI);
947 Value *S2V1 = new LoadInst(Op2Cast, RHS->getName()+".val1", CI);
948 Value *D1 = BinaryOperator::createSub(S1V1, S2V1,
949 CI->getName()+".d1", CI);
950 Constant *One = ConstantInt::get(Type::Int32Ty, 1);
951 Value *G1 = new GetElementPtrInst(Op1Cast, One, "next1v", CI);
952 Value *G2 = new GetElementPtrInst(Op2Cast, One, "next2v", CI);
953 Value *S1V2 = new LoadInst(G1, LHS->getName()+".val2", CI);
954 Value *S2V2 = new LoadInst(G2, RHS->getName()+".val2", CI);
955 Value *D2 = BinaryOperator::createSub(S1V2, S2V2,
956 CI->getName()+".d1", CI);
957 Value *Or = BinaryOperator::createOr(D1, D2, CI->getName()+".res", CI);
958 if (Or->getType() != CI->getType())
959 Or = CastInst::createIntegerCast(Or, CI->getType(), false /*ZExt*/,
961 return ReplaceCallWith(CI, Or);
973 /// This LibCallOptimization will simplify a call to the memcpy library
974 /// function by expanding it out to a single store of size 0, 1, 2, 4, or 8
975 /// bytes depending on the length of the string and the alignment. Additional
976 /// optimizations are possible in code generation (sequence of immediate store)
977 /// @brief Simplify the memcpy library function.
978 struct VISIBILITY_HIDDEN LLVMMemCpyMoveOptzn : public LibCallOptimization {
979 LLVMMemCpyMoveOptzn(const char* fname, const char* desc)
980 : LibCallOptimization(fname, desc) {}
982 /// @brief Make sure that the "memcpy" function has the right prototype
983 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& TD) {
984 // Just make sure this has 4 arguments per LLVM spec.
985 return (f->arg_size() == 4);
988 /// Because of alignment and instruction information that we don't have, we
989 /// leave the bulk of this to the code generators. The optimization here just
990 /// deals with a few degenerate cases where the length of the string and the
991 /// alignment match the sizes of our intrinsic types so we can do a load and
992 /// store instead of the memcpy call.
993 /// @brief Perform the memcpy optimization.
994 virtual bool OptimizeCall(CallInst* ci, SimplifyLibCalls& TD) {
995 // Make sure we have constant int values to work with
996 ConstantInt* LEN = dyn_cast<ConstantInt>(ci->getOperand(3));
999 ConstantInt* ALIGN = dyn_cast<ConstantInt>(ci->getOperand(4));
1003 // If the length is larger than the alignment, we can't optimize
1004 uint64_t len = LEN->getZExtValue();
1005 uint64_t alignment = ALIGN->getZExtValue();
1007 alignment = 1; // Alignment 0 is identity for alignment 1
1008 if (len > alignment)
1011 // Get the type we will cast to, based on size of the string
1012 Value* dest = ci->getOperand(1);
1013 Value* src = ci->getOperand(2);
1014 const Type* castType = 0;
1017 // memcpy(d,s,0,a) -> d
1018 return ReplaceCallWith(ci, 0);
1019 case 1: castType = Type::Int8Ty; break;
1020 case 2: castType = Type::Int16Ty; break;
1021 case 4: castType = Type::Int32Ty; break;
1022 case 8: castType = Type::Int64Ty; break;
1027 // Cast source and dest to the right sized primitive and then load/store
1028 CastInst* SrcCast = CastInst::create(Instruction::BitCast,
1029 src, PointerType::get(castType), src->getName()+".cast", ci);
1030 CastInst* DestCast = CastInst::create(Instruction::BitCast,
1031 dest, PointerType::get(castType),dest->getName()+".cast", ci);
1032 LoadInst* LI = new LoadInst(SrcCast,SrcCast->getName()+".val",ci);
1033 new StoreInst(LI, DestCast, ci);
1034 return ReplaceCallWith(ci, 0);
1038 /// This LibCallOptimization will simplify a call to the memcpy/memmove library
1040 LLVMMemCpyMoveOptzn LLVMMemCpyOptimizer32("llvm.memcpy.i32",
1041 "Number of 'llvm.memcpy' calls simplified");
1042 LLVMMemCpyMoveOptzn LLVMMemCpyOptimizer64("llvm.memcpy.i64",
1043 "Number of 'llvm.memcpy' calls simplified");
1044 LLVMMemCpyMoveOptzn LLVMMemMoveOptimizer32("llvm.memmove.i32",
1045 "Number of 'llvm.memmove' calls simplified");
1046 LLVMMemCpyMoveOptzn LLVMMemMoveOptimizer64("llvm.memmove.i64",
1047 "Number of 'llvm.memmove' calls simplified");
1049 /// This LibCallOptimization will simplify a call to the memset library
1050 /// function by expanding it out to a single store of size 0, 1, 2, 4, or 8
1051 /// bytes depending on the length argument.
1052 struct VISIBILITY_HIDDEN LLVMMemSetOptimization : public LibCallOptimization {
1053 /// @brief Default Constructor
1054 LLVMMemSetOptimization(const char *Name) : LibCallOptimization(Name,
1055 "Number of 'llvm.memset' calls simplified") {}
1057 /// @brief Make sure that the "memset" function has the right prototype
1058 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &TD) {
1059 // Just make sure this has 3 arguments per LLVM spec.
1060 return F->arg_size() == 4;
1063 /// Because of alignment and instruction information that we don't have, we
1064 /// leave the bulk of this to the code generators. The optimization here just
1065 /// deals with a few degenerate cases where the length parameter is constant
1066 /// and the alignment matches the sizes of our intrinsic types so we can do
1067 /// store instead of the memcpy call. Other calls are transformed into the
1068 /// llvm.memset intrinsic.
1069 /// @brief Perform the memset optimization.
1070 virtual bool OptimizeCall(CallInst *ci, SimplifyLibCalls &TD) {
1071 // Make sure we have constant int values to work with
1072 ConstantInt* LEN = dyn_cast<ConstantInt>(ci->getOperand(3));
1075 ConstantInt* ALIGN = dyn_cast<ConstantInt>(ci->getOperand(4));
1079 // Extract the length and alignment
1080 uint64_t len = LEN->getZExtValue();
1081 uint64_t alignment = ALIGN->getZExtValue();
1083 // Alignment 0 is identity for alignment 1
1087 // If the length is zero, this is a no-op
1089 // memset(d,c,0,a) -> noop
1090 return ReplaceCallWith(ci, 0);
1093 // If the length is larger than the alignment, we can't optimize
1094 if (len > alignment)
1097 // Make sure we have a constant ubyte to work with so we can extract
1098 // the value to be filled.
1099 ConstantInt* FILL = dyn_cast<ConstantInt>(ci->getOperand(2));
1102 if (FILL->getType() != Type::Int8Ty)
1105 // memset(s,c,n) -> store s, c (for n=1,2,4,8)
1107 // Extract the fill character
1108 uint64_t fill_char = FILL->getZExtValue();
1109 uint64_t fill_value = fill_char;
1111 // Get the type we will cast to, based on size of memory area to fill, and
1112 // and the value we will store there.
1113 Value* dest = ci->getOperand(1);
1114 const Type* castType = 0;
1117 castType = Type::Int8Ty;
1120 castType = Type::Int16Ty;
1121 fill_value |= fill_char << 8;
1124 castType = Type::Int32Ty;
1125 fill_value |= fill_char << 8 | fill_char << 16 | fill_char << 24;
1128 castType = Type::Int64Ty;
1129 fill_value |= fill_char << 8 | fill_char << 16 | fill_char << 24;
1130 fill_value |= fill_char << 32 | fill_char << 40 | fill_char << 48;
1131 fill_value |= fill_char << 56;
1137 // Cast dest to the right sized primitive and then load/store
1138 CastInst* DestCast = new BitCastInst(dest, PointerType::get(castType),
1139 dest->getName()+".cast", ci);
1140 new StoreInst(ConstantInt::get(castType,fill_value),DestCast, ci);
1141 return ReplaceCallWith(ci, 0);
1145 LLVMMemSetOptimization MemSet32Optimizer("llvm.memset.i32");
1146 LLVMMemSetOptimization MemSet64Optimizer("llvm.memset.i64");
1149 /// This LibCallOptimization will simplify calls to the "pow" library
1150 /// function. It looks for cases where the result of pow is well known and
1151 /// substitutes the appropriate value.
1152 /// @brief Simplify the pow library function.
1153 struct VISIBILITY_HIDDEN PowOptimization : public LibCallOptimization {
1155 /// @brief Default Constructor
1156 PowOptimization() : LibCallOptimization("pow",
1157 "Number of 'pow' calls simplified") {}
1159 /// @brief Make sure that the "pow" function has the right prototype
1160 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC){
1161 // Just make sure this has 2 arguments
1162 return (f->arg_size() == 2);
1165 /// @brief Perform the pow optimization.
1166 virtual bool OptimizeCall(CallInst *ci, SimplifyLibCalls &SLC) {
1167 const Type *Ty = cast<Function>(ci->getOperand(0))->getReturnType();
1168 Value* base = ci->getOperand(1);
1169 Value* expn = ci->getOperand(2);
1170 if (ConstantFP *Op1 = dyn_cast<ConstantFP>(base)) {
1171 double Op1V = Op1->getValue();
1172 if (Op1V == 1.0) // pow(1.0,x) -> 1.0
1173 return ReplaceCallWith(ci, ConstantFP::get(Ty, 1.0));
1174 } else if (ConstantFP* Op2 = dyn_cast<ConstantFP>(expn)) {
1175 double Op2V = Op2->getValue();
1177 // pow(x,0.0) -> 1.0
1178 return ReplaceCallWith(ci, ConstantFP::get(Ty,1.0));
1179 } else if (Op2V == 0.5) {
1180 // pow(x,0.5) -> sqrt(x)
1181 CallInst* sqrt_inst = new CallInst(SLC.get_sqrt(), base,
1182 ci->getName()+".pow",ci);
1183 return ReplaceCallWith(ci, sqrt_inst);
1184 } else if (Op2V == 1.0) {
1186 return ReplaceCallWith(ci, base);
1187 } else if (Op2V == -1.0) {
1188 // pow(x,-1.0) -> 1.0/x
1190 BinaryOperator::createFDiv(ConstantFP::get(Ty, 1.0), base,
1191 ci->getName()+".pow", ci);
1192 return ReplaceCallWith(ci, div_inst);
1195 return false; // opt failed
1199 /// This LibCallOptimization will simplify calls to the "printf" library
1200 /// function. It looks for cases where the result of printf is not used and the
1201 /// operation can be reduced to something simpler.
1202 /// @brief Simplify the printf library function.
1203 struct VISIBILITY_HIDDEN PrintfOptimization : public LibCallOptimization {
1205 /// @brief Default Constructor
1206 PrintfOptimization() : LibCallOptimization("printf",
1207 "Number of 'printf' calls simplified") {}
1209 /// @brief Make sure that the "printf" function has the right prototype
1210 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC){
1211 // Just make sure this has at least 1 arguments
1212 return (f->arg_size() >= 1);
1215 /// @brief Perform the printf optimization.
1216 virtual bool OptimizeCall(CallInst* ci, SimplifyLibCalls& SLC) {
1217 // If the call has more than 2 operands, we can't optimize it
1218 if (ci->getNumOperands() > 3 || ci->getNumOperands() <= 2)
1221 // If the result of the printf call is used, none of these optimizations
1223 if (!ci->use_empty())
1226 // All the optimizations depend on the length of the first argument and the
1227 // fact that it is a constant string array. Check that now
1228 uint64_t len, StartIdx;
1229 ConstantArray* CA = 0;
1230 if (!GetConstantStringInfo(ci->getOperand(1), CA, len, StartIdx))
1233 if (len != 2 && len != 3)
1236 // The first character has to be a %
1237 if (ConstantInt* CI = dyn_cast<ConstantInt>(CA->getOperand(0)))
1238 if (CI->getZExtValue() != '%')
1241 // Get the second character and switch on its value
1242 ConstantInt* CI = dyn_cast<ConstantInt>(CA->getOperand(1));
1243 switch (CI->getZExtValue()) {
1247 dyn_cast<ConstantInt>(CA->getOperand(2))->getZExtValue() != '\n')
1250 // printf("%s\n",str) -> puts(str)
1251 std::vector<Value*> args;
1252 new CallInst(SLC.get_puts(), CastToCStr(ci->getOperand(2), *ci),
1254 return ReplaceCallWith(ci, ConstantInt::get(Type::Int32Ty, len));
1258 // printf("%c",c) -> putchar(c)
1262 CastInst *Char = CastInst::createSExtOrBitCast(
1263 ci->getOperand(2), Type::Int32Ty, CI->getName()+".int", ci);
1264 new CallInst(SLC.get_putchar(), Char, "", ci);
1265 return ReplaceCallWith(ci, ConstantInt::get(Type::Int32Ty, 1));
1274 /// This LibCallOptimization will simplify calls to the "fprintf" library
1275 /// function. It looks for cases where the result of fprintf is not used and the
1276 /// operation can be reduced to something simpler.
1277 /// @brief Simplify the fprintf library function.
1278 struct VISIBILITY_HIDDEN FPrintFOptimization : public LibCallOptimization {
1280 /// @brief Default Constructor
1281 FPrintFOptimization() : LibCallOptimization("fprintf",
1282 "Number of 'fprintf' calls simplified") {}
1284 /// @brief Make sure that the "fprintf" function has the right prototype
1285 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC){
1286 // Just make sure this has at least 2 arguments
1287 return (f->arg_size() >= 2);
1290 /// @brief Perform the fprintf optimization.
1291 virtual bool OptimizeCall(CallInst* ci, SimplifyLibCalls& SLC) {
1292 // If the call has more than 3 operands, we can't optimize it
1293 if (ci->getNumOperands() > 4 || ci->getNumOperands() <= 2)
1296 // If the result of the fprintf call is used, none of these optimizations
1298 if (!ci->use_empty())
1301 // All the optimizations depend on the length of the second argument and the
1302 // fact that it is a constant string array. Check that now
1303 uint64_t len, StartIdx;
1304 ConstantArray* CA = 0;
1305 if (!GetConstantStringInfo(ci->getOperand(2), CA, len, StartIdx))
1308 if (ci->getNumOperands() == 3) {
1309 // Make sure there's no % in the constant array
1310 for (unsigned i = 0; i < len; ++i) {
1311 if (ConstantInt* CI = dyn_cast<ConstantInt>(CA->getOperand(i))) {
1312 // Check for the null terminator
1313 if (CI->getZExtValue() == '%')
1314 return false; // we found end of string
1320 // fprintf(file,fmt) -> fwrite(fmt,strlen(fmt),file)
1321 const Type* FILEptr_type = ci->getOperand(1)->getType();
1323 // Make sure that the fprintf() and fwrite() functions both take the
1324 // same type of char pointer.
1325 if (ci->getOperand(2)->getType() != PointerType::get(Type::Int8Ty))
1330 ConstantInt::get(SLC.getIntPtrType(),len),
1331 ConstantInt::get(SLC.getIntPtrType(),1),
1334 new CallInst(SLC.get_fwrite(FILEptr_type), args, 4, ci->getName(), ci);
1335 return ReplaceCallWith(ci, ConstantInt::get(Type::Int32Ty,len));
1338 // The remaining optimizations require the format string to be length 2
1343 // The first character has to be a %
1344 if (ConstantInt* CI = dyn_cast<ConstantInt>(CA->getOperand(0)))
1345 if (CI->getZExtValue() != '%')
1348 // Get the second character and switch on its value
1349 ConstantInt* CI = dyn_cast<ConstantInt>(CA->getOperand(1));
1350 switch (CI->getZExtValue()) {
1352 uint64_t len, StartIdx;
1353 ConstantArray* CA = 0;
1354 if (GetConstantStringInfo(ci->getOperand(3), CA, len, StartIdx)) {
1355 // fprintf(file,"%s",str) -> fwrite(str,strlen(str),1,file)
1356 const Type* FILEptr_type = ci->getOperand(1)->getType();
1358 CastToCStr(ci->getOperand(3), *ci),
1359 ConstantInt::get(SLC.getIntPtrType(), len),
1360 ConstantInt::get(SLC.getIntPtrType(), 1),
1363 new CallInst(SLC.get_fwrite(FILEptr_type), args, 4,ci->getName(), ci);
1364 return ReplaceCallWith(ci, ConstantInt::get(Type::Int32Ty, len));
1366 // fprintf(file,"%s",str) -> fputs(str,file)
1367 const Type* FILEptr_type = ci->getOperand(1)->getType();
1368 new CallInst(SLC.get_fputs(FILEptr_type),
1369 CastToCStr(ci->getOperand(3), *ci),
1370 ci->getOperand(1), ci->getName(),ci);
1371 return ReplaceCallWith(ci, ConstantInt::get(Type::Int32Ty,len));
1374 // fprintf(file,"%c",c) -> fputc(c,file)
1375 const Type* FILEptr_type = ci->getOperand(1)->getType();
1376 CastInst* cast = CastInst::createSExtOrBitCast(
1377 ci->getOperand(3), Type::Int32Ty, CI->getName()+".int", ci);
1378 new CallInst(SLC.get_fputc(FILEptr_type), cast,ci->getOperand(1),"",ci);
1379 return ReplaceCallWith(ci, ConstantInt::get(Type::Int32Ty,1));
1387 /// This LibCallOptimization will simplify calls to the "sprintf" library
1388 /// function. It looks for cases where the result of sprintf is not used and the
1389 /// operation can be reduced to something simpler.
1390 /// @brief Simplify the sprintf library function.
1391 struct VISIBILITY_HIDDEN SPrintFOptimization : public LibCallOptimization {
1393 /// @brief Default Constructor
1394 SPrintFOptimization() : LibCallOptimization("sprintf",
1395 "Number of 'sprintf' calls simplified") {}
1397 /// @brief Make sure that the "fprintf" function has the right prototype
1398 virtual bool ValidateCalledFunction(const Function *f, SimplifyLibCalls &SLC){
1399 // Just make sure this has at least 2 arguments
1400 return (f->getReturnType() == Type::Int32Ty && f->arg_size() >= 2);
1403 /// @brief Perform the sprintf optimization.
1404 virtual bool OptimizeCall(CallInst *ci, SimplifyLibCalls &SLC) {
1405 // If the call has more than 3 operands, we can't optimize it
1406 if (ci->getNumOperands() > 4 || ci->getNumOperands() < 3)
1409 // All the optimizations depend on the length of the second argument and the
1410 // fact that it is a constant string array. Check that now
1411 uint64_t len, StartIdx;
1412 ConstantArray* CA = 0;
1413 if (!GetConstantStringInfo(ci->getOperand(2), CA, len, StartIdx))
1416 if (ci->getNumOperands() == 3) {
1418 // If the length is 0, we just need to store a null byte
1419 new StoreInst(ConstantInt::get(Type::Int8Ty,0),ci->getOperand(1),ci);
1420 return ReplaceCallWith(ci, ConstantInt::get(Type::Int32Ty,0));
1423 // Make sure there's no % in the constant array
1424 for (unsigned i = 0; i < len; ++i) {
1425 if (ConstantInt* CI = dyn_cast<ConstantInt>(CA->getOperand(i))) {
1426 // Check for the null terminator
1427 if (CI->getZExtValue() == '%')
1428 return false; // we found a %, can't optimize
1430 return false; // initializer is not constant int, can't optimize
1434 // Increment length because we want to copy the null byte too
1437 // sprintf(str,fmt) -> llvm.memcpy(str,fmt,strlen(fmt),1)
1441 ConstantInt::get(SLC.getIntPtrType(),len),
1442 ConstantInt::get(Type::Int32Ty, 1)
1444 new CallInst(SLC.get_memcpy(), args, 4, "", ci);
1445 return ReplaceCallWith(ci, ConstantInt::get(Type::Int32Ty,len));
1448 // The remaining optimizations require the format string to be length 2
1453 // The first character has to be a %
1454 if (ConstantInt* CI = dyn_cast<ConstantInt>(CA->getOperand(0)))
1455 if (CI->getZExtValue() != '%')
1458 // Get the second character and switch on its value
1459 ConstantInt* CI = dyn_cast<ConstantInt>(CA->getOperand(1));
1460 switch (CI->getZExtValue()) {
1462 // sprintf(dest,"%s",str) -> llvm.memcpy(dest, str, strlen(str)+1, 1)
1463 Value *Len = new CallInst(SLC.get_strlen(),
1464 CastToCStr(ci->getOperand(3), *ci),
1465 ci->getOperand(3)->getName()+".len", ci);
1466 Value *Len1 = BinaryOperator::createAdd(Len,
1467 ConstantInt::get(Len->getType(), 1),
1468 Len->getName()+"1", ci);
1469 if (Len1->getType() != SLC.getIntPtrType())
1470 Len1 = CastInst::createIntegerCast(Len1, SLC.getIntPtrType(), false,
1471 Len1->getName(), ci);
1473 CastToCStr(ci->getOperand(1), *ci),
1474 CastToCStr(ci->getOperand(3), *ci),
1476 ConstantInt::get(Type::Int32Ty,1)
1478 new CallInst(SLC.get_memcpy(), args, 4, "", ci);
1480 // The strlen result is the unincremented number of bytes in the string.
1481 if (!ci->use_empty()) {
1482 if (Len->getType() != ci->getType())
1483 Len = CastInst::createIntegerCast(Len, ci->getType(), false,
1484 Len->getName(), ci);
1485 ci->replaceAllUsesWith(Len);
1487 return ReplaceCallWith(ci, 0);
1490 // sprintf(dest,"%c",chr) -> store chr, dest
1491 CastInst* cast = CastInst::createTruncOrBitCast(
1492 ci->getOperand(3), Type::Int8Ty, "char", ci);
1493 new StoreInst(cast, ci->getOperand(1), ci);
1494 GetElementPtrInst* gep = new GetElementPtrInst(ci->getOperand(1),
1495 ConstantInt::get(Type::Int32Ty,1),ci->getOperand(1)->getName()+".end",
1497 new StoreInst(ConstantInt::get(Type::Int8Ty,0),gep,ci);
1498 return ReplaceCallWith(ci, ConstantInt::get(Type::Int32Ty, 1));
1505 /// This LibCallOptimization will simplify calls to the "fputs" library
1506 /// function. It looks for cases where the result of fputs is not used and the
1507 /// operation can be reduced to something simpler.
1508 /// @brief Simplify the puts library function.
1509 struct VISIBILITY_HIDDEN PutsOptimization : public LibCallOptimization {
1511 /// @brief Default Constructor
1512 PutsOptimization() : LibCallOptimization("fputs",
1513 "Number of 'fputs' calls simplified") {}
1515 /// @brief Make sure that the "fputs" function has the right prototype
1516 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
1517 // Just make sure this has 2 arguments
1518 return F->arg_size() == 2;
1521 /// @brief Perform the fputs optimization.
1522 virtual bool OptimizeCall(CallInst* ci, SimplifyLibCalls& SLC) {
1523 // If the result is used, none of these optimizations work
1524 if (!ci->use_empty())
1527 // All the optimizations depend on the length of the first argument and the
1528 // fact that it is a constant string array. Check that now
1529 uint64_t len, StartIdx;
1531 if (!GetConstantStringInfo(ci->getOperand(1), CA, len, StartIdx))
1536 // fputs("",F) -> noop
1540 // fputs(s,F) -> fputc(s[0],F) (if s is constant and strlen(s) == 1)
1541 const Type* FILEptr_type = ci->getOperand(2)->getType();
1542 LoadInst* loadi = new LoadInst(ci->getOperand(1),
1543 ci->getOperand(1)->getName()+".byte",ci);
1544 CastInst* casti = new SExtInst(loadi, Type::Int32Ty,
1545 loadi->getName()+".int", ci);
1546 new CallInst(SLC.get_fputc(FILEptr_type), casti,
1547 ci->getOperand(2), "", ci);
1552 // fputs(s,F) -> fwrite(s,1,len,F) (if s is constant and strlen(s) > 1)
1553 const Type* FILEptr_type = ci->getOperand(2)->getType();
1556 ConstantInt::get(SLC.getIntPtrType(),len),
1557 ConstantInt::get(SLC.getIntPtrType(),1),
1560 new CallInst(SLC.get_fwrite(FILEptr_type), parms, 4, "", ci);
1564 return ReplaceCallWith(ci, 0); // Known to have no uses (see above).
1568 /// This LibCallOptimization will simplify calls to the "isdigit" library
1569 /// function. It simply does range checks the parameter explicitly.
1570 /// @brief Simplify the isdigit library function.
1571 struct VISIBILITY_HIDDEN isdigitOptimization : public LibCallOptimization {
1573 isdigitOptimization() : LibCallOptimization("isdigit",
1574 "Number of 'isdigit' calls simplified") {}
1576 /// @brief Make sure that the "isdigit" function has the right prototype
1577 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC){
1578 // Just make sure this has 1 argument
1579 return (f->arg_size() == 1);
1582 /// @brief Perform the toascii optimization.
1583 virtual bool OptimizeCall(CallInst *ci, SimplifyLibCalls &SLC) {
1584 if (ConstantInt* CI = dyn_cast<ConstantInt>(ci->getOperand(1))) {
1585 // isdigit(c) -> 0 or 1, if 'c' is constant
1586 uint64_t val = CI->getZExtValue();
1587 if (val >= '0' && val <= '9')
1588 return ReplaceCallWith(ci, ConstantInt::get(Type::Int32Ty, 1));
1590 return ReplaceCallWith(ci, ConstantInt::get(Type::Int32Ty, 0));
1593 // isdigit(c) -> (unsigned)c - '0' <= 9
1594 CastInst* cast = CastInst::createIntegerCast(ci->getOperand(1),
1595 Type::Int32Ty, false/*ZExt*/, ci->getOperand(1)->getName()+".uint", ci);
1596 BinaryOperator* sub_inst = BinaryOperator::createSub(cast,
1597 ConstantInt::get(Type::Int32Ty,0x30),
1598 ci->getOperand(1)->getName()+".sub",ci);
1599 ICmpInst* setcond_inst = new ICmpInst(ICmpInst::ICMP_ULE,sub_inst,
1600 ConstantInt::get(Type::Int32Ty,9),
1601 ci->getOperand(1)->getName()+".cmp",ci);
1602 CastInst* c2 = new ZExtInst(setcond_inst, Type::Int32Ty,
1603 ci->getOperand(1)->getName()+".isdigit", ci);
1604 return ReplaceCallWith(ci, c2);
1608 struct VISIBILITY_HIDDEN isasciiOptimization : public LibCallOptimization {
1610 isasciiOptimization()
1611 : LibCallOptimization("isascii", "Number of 'isascii' calls simplified") {}
1613 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
1614 return F->arg_size() == 1 && F->arg_begin()->getType()->isInteger() &&
1615 F->getReturnType()->isInteger();
1618 /// @brief Perform the isascii optimization.
1619 virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
1620 // isascii(c) -> (unsigned)c < 128
1621 Value *V = CI->getOperand(1);
1622 Value *Cmp = new ICmpInst(ICmpInst::ICMP_ULT, V,
1623 ConstantInt::get(V->getType(), 128),
1624 V->getName()+".isascii", CI);
1625 if (Cmp->getType() != CI->getType())
1626 Cmp = new BitCastInst(Cmp, CI->getType(), Cmp->getName(), CI);
1627 return ReplaceCallWith(CI, Cmp);
1632 /// This LibCallOptimization will simplify calls to the "toascii" library
1633 /// function. It simply does the corresponding and operation to restrict the
1634 /// range of values to the ASCII character set (0-127).
1635 /// @brief Simplify the toascii library function.
1636 struct VISIBILITY_HIDDEN ToAsciiOptimization : public LibCallOptimization {
1638 /// @brief Default Constructor
1639 ToAsciiOptimization() : LibCallOptimization("toascii",
1640 "Number of 'toascii' calls simplified") {}
1642 /// @brief Make sure that the "fputs" function has the right prototype
1643 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC){
1644 // Just make sure this has 2 arguments
1645 return (f->arg_size() == 1);
1648 /// @brief Perform the toascii optimization.
1649 virtual bool OptimizeCall(CallInst *ci, SimplifyLibCalls &SLC) {
1650 // toascii(c) -> (c & 0x7f)
1651 Value *chr = ci->getOperand(1);
1652 Value *and_inst = BinaryOperator::createAnd(chr,
1653 ConstantInt::get(chr->getType(),0x7F),ci->getName()+".toascii",ci);
1654 return ReplaceCallWith(ci, and_inst);
1658 /// This LibCallOptimization will simplify calls to the "ffs" library
1659 /// calls which find the first set bit in an int, long, or long long. The
1660 /// optimization is to compute the result at compile time if the argument is
1662 /// @brief Simplify the ffs library function.
1663 struct VISIBILITY_HIDDEN FFSOptimization : public LibCallOptimization {
1665 /// @brief Subclass Constructor
1666 FFSOptimization(const char* funcName, const char* description)
1667 : LibCallOptimization(funcName, description) {}
1670 /// @brief Default Constructor
1671 FFSOptimization() : LibCallOptimization("ffs",
1672 "Number of 'ffs' calls simplified") {}
1674 /// @brief Make sure that the "ffs" function has the right prototype
1675 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
1676 // Just make sure this has 2 arguments
1677 return F->arg_size() == 1 && F->getReturnType() == Type::Int32Ty;
1680 /// @brief Perform the ffs optimization.
1681 virtual bool OptimizeCall(CallInst *TheCall, SimplifyLibCalls &SLC) {
1682 if (ConstantInt *CI = dyn_cast<ConstantInt>(TheCall->getOperand(1))) {
1683 // ffs(cnst) -> bit#
1684 // ffsl(cnst) -> bit#
1685 // ffsll(cnst) -> bit#
1686 uint64_t val = CI->getZExtValue();
1690 while ((val & 1) == 0) {
1695 return ReplaceCallWith(TheCall, ConstantInt::get(Type::Int32Ty, result));
1698 // ffs(x) -> x == 0 ? 0 : llvm.cttz(x)+1
1699 // ffsl(x) -> x == 0 ? 0 : llvm.cttz(x)+1
1700 // ffsll(x) -> x == 0 ? 0 : llvm.cttz(x)+1
1701 const Type *ArgType = TheCall->getOperand(1)->getType();
1702 const char *CTTZName;
1703 assert(ArgType->getTypeID() == Type::IntegerTyID &&
1704 "llvm.cttz argument is not an integer?");
1705 unsigned BitWidth = cast<IntegerType>(ArgType)->getBitWidth();
1707 CTTZName = "llvm.cttz.i8";
1708 else if (BitWidth == 16)
1709 CTTZName = "llvm.cttz.i16";
1710 else if (BitWidth == 32)
1711 CTTZName = "llvm.cttz.i32";
1713 assert(BitWidth == 64 && "Unknown bitwidth");
1714 CTTZName = "llvm.cttz.i64";
1717 Constant *F = SLC.getModule()->getOrInsertFunction(CTTZName, ArgType,
1719 Value *V = CastInst::createIntegerCast(TheCall->getOperand(1), ArgType,
1720 false/*ZExt*/, "tmp", TheCall);
1721 Value *V2 = new CallInst(F, V, "tmp", TheCall);
1722 V2 = CastInst::createIntegerCast(V2, Type::Int32Ty, false/*ZExt*/,
1724 V2 = BinaryOperator::createAdd(V2, ConstantInt::get(Type::Int32Ty, 1),
1726 Value *Cond = new ICmpInst(ICmpInst::ICMP_EQ, V,
1727 Constant::getNullValue(V->getType()), "tmp",
1729 V2 = new SelectInst(Cond, ConstantInt::get(Type::Int32Ty, 0), V2,
1730 TheCall->getName(), TheCall);
1731 return ReplaceCallWith(TheCall, V2);
1735 /// This LibCallOptimization will simplify calls to the "ffsl" library
1736 /// calls. It simply uses FFSOptimization for which the transformation is
1738 /// @brief Simplify the ffsl library function.
1739 struct VISIBILITY_HIDDEN FFSLOptimization : public FFSOptimization {
1741 /// @brief Default Constructor
1742 FFSLOptimization() : FFSOptimization("ffsl",
1743 "Number of 'ffsl' calls simplified") {}
1747 /// This LibCallOptimization will simplify calls to the "ffsll" library
1748 /// calls. It simply uses FFSOptimization for which the transformation is
1750 /// @brief Simplify the ffsl library function.
1751 struct VISIBILITY_HIDDEN FFSLLOptimization : public FFSOptimization {
1753 /// @brief Default Constructor
1754 FFSLLOptimization() : FFSOptimization("ffsll",
1755 "Number of 'ffsll' calls simplified") {}
1759 /// This optimizes unary functions that take and return doubles.
1760 struct UnaryDoubleFPOptimizer : public LibCallOptimization {
1761 UnaryDoubleFPOptimizer(const char *Fn, const char *Desc)
1762 : LibCallOptimization(Fn, Desc) {}
1764 // Make sure that this function has the right prototype
1765 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
1766 return F->arg_size() == 1 && F->arg_begin()->getType() == Type::DoubleTy &&
1767 F->getReturnType() == Type::DoubleTy;
1770 /// ShrinkFunctionToFloatVersion - If the input to this function is really a
1771 /// float, strength reduce this to a float version of the function,
1772 /// e.g. floor((double)FLT) -> (double)floorf(FLT). This can only be called
1773 /// when the target supports the destination function and where there can be
1774 /// no precision loss.
1775 static bool ShrinkFunctionToFloatVersion(CallInst *CI, SimplifyLibCalls &SLC,
1776 Constant *(SimplifyLibCalls::*FP)()){
1777 if (FPExtInst *Cast = dyn_cast<FPExtInst>(CI->getOperand(1)))
1778 if (Cast->getOperand(0)->getType() == Type::FloatTy) {
1779 Value *New = new CallInst((SLC.*FP)(), Cast->getOperand(0),
1781 New = new FPExtInst(New, Type::DoubleTy, CI->getName(), CI);
1782 CI->replaceAllUsesWith(New);
1783 CI->eraseFromParent();
1784 if (Cast->use_empty())
1785 Cast->eraseFromParent();
1793 struct VISIBILITY_HIDDEN FloorOptimization : public UnaryDoubleFPOptimizer {
1795 : UnaryDoubleFPOptimizer("floor", "Number of 'floor' calls simplified") {}
1797 virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
1799 // If this is a float argument passed in, convert to floorf.
1800 if (ShrinkFunctionToFloatVersion(CI, SLC, &SimplifyLibCalls::get_floorf))
1803 return false; // opt failed
1807 struct VISIBILITY_HIDDEN CeilOptimization : public UnaryDoubleFPOptimizer {
1809 : UnaryDoubleFPOptimizer("ceil", "Number of 'ceil' calls simplified") {}
1811 virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
1813 // If this is a float argument passed in, convert to ceilf.
1814 if (ShrinkFunctionToFloatVersion(CI, SLC, &SimplifyLibCalls::get_ceilf))
1817 return false; // opt failed
1821 struct VISIBILITY_HIDDEN RoundOptimization : public UnaryDoubleFPOptimizer {
1823 : UnaryDoubleFPOptimizer("round", "Number of 'round' calls simplified") {}
1825 virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
1827 // If this is a float argument passed in, convert to roundf.
1828 if (ShrinkFunctionToFloatVersion(CI, SLC, &SimplifyLibCalls::get_roundf))
1831 return false; // opt failed
1835 struct VISIBILITY_HIDDEN RintOptimization : public UnaryDoubleFPOptimizer {
1837 : UnaryDoubleFPOptimizer("rint", "Number of 'rint' calls simplified") {}
1839 virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
1841 // If this is a float argument passed in, convert to rintf.
1842 if (ShrinkFunctionToFloatVersion(CI, SLC, &SimplifyLibCalls::get_rintf))
1845 return false; // opt failed
1849 struct VISIBILITY_HIDDEN NearByIntOptimization : public UnaryDoubleFPOptimizer {
1850 NearByIntOptimization()
1851 : UnaryDoubleFPOptimizer("nearbyint",
1852 "Number of 'nearbyint' calls simplified") {}
1854 virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
1855 #ifdef HAVE_NEARBYINTF
1856 // If this is a float argument passed in, convert to nearbyintf.
1857 if (ShrinkFunctionToFloatVersion(CI, SLC,&SimplifyLibCalls::get_nearbyintf))
1860 return false; // opt failed
1862 } NearByIntOptimizer;
1864 /// GetConstantStringInfo - This function computes the length of a
1865 /// null-terminated constant array of integers. This function can't rely on the
1866 /// size of the constant array because there could be a null terminator in the
1867 /// middle of the array.
1869 /// We also have to bail out if we find a non-integer constant initializer
1870 /// of one of the elements or if there is no null-terminator. The logic
1871 /// below checks each of these conditions and will return true only if all
1872 /// conditions are met. If the conditions aren't met, this returns false.
1874 /// If successful, the \p Array param is set to the constant array being
1875 /// indexed, the \p Length parameter is set to the length of the null-terminated
1876 /// string pointed to by V, the \p StartIdx value is set to the first
1877 /// element of the Array that V points to, and true is returned.
1878 static bool GetConstantStringInfo(Value *V, ConstantArray *&Array,
1879 uint64_t &Length, uint64_t &StartIdx) {
1880 assert(V != 0 && "Invalid args to GetConstantStringInfo");
1881 // Initialize results.
1887 // If the value is not a GEP instruction nor a constant expression with a
1888 // GEP instruction, then return false because ConstantArray can't occur
1890 if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(V)) {
1892 } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) {
1893 if (CE->getOpcode() != Instruction::GetElementPtr)
1900 // Make sure the GEP has exactly three arguments.
1901 if (GEP->getNumOperands() != 3)
1904 // Check to make sure that the first operand of the GEP is an integer and
1905 // has value 0 so that we are sure we're indexing into the initializer.
1906 if (ConstantInt* op1 = dyn_cast<ConstantInt>(GEP->getOperand(1))) {
1912 // If the second index isn't a ConstantInt, then this is a variable index
1913 // into the array. If this occurs, we can't say anything meaningful about
1916 if (ConstantInt *CI = dyn_cast<ConstantInt>(GEP->getOperand(2)))
1917 StartIdx = CI->getZExtValue();
1921 // The GEP instruction, constant or instruction, must reference a global
1922 // variable that is a constant and is initialized. The referenced constant
1923 // initializer is the array that we'll use for optimization.
1924 GlobalVariable* GV = dyn_cast<GlobalVariable>(GEP->getOperand(0));
1925 if (!GV || !GV->isConstant() || !GV->hasInitializer())
1927 Constant *GlobalInit = GV->getInitializer();
1929 // Handle the ConstantAggregateZero case
1930 if (isa<ConstantAggregateZero>(GlobalInit)) {
1931 // This is a degenerate case. The initializer is constant zero so the
1932 // length of the string must be zero.
1937 // Must be a Constant Array
1938 Array = dyn_cast<ConstantArray>(GlobalInit);
1939 if (!Array) return false;
1941 // Get the number of elements in the array
1942 uint64_t NumElts = Array->getType()->getNumElements();
1944 // Traverse the constant array from start_idx (derived above) which is
1945 // the place the GEP refers to in the array.
1948 if (Length >= NumElts)
1949 return false; // The array isn't null terminated.
1951 Constant *Elt = Array->getOperand(Length);
1952 if (ConstantInt *CI = dyn_cast<ConstantInt>(Elt)) {
1953 // Check for the null terminator.
1955 break; // we found end of string
1957 return false; // This array isn't suitable, non-int initializer
1961 // Subtract out the initial value from the length
1963 return true; // success!
1966 /// CastToCStr - Return V if it is an sbyte*, otherwise cast it to sbyte*,
1967 /// inserting the cast before IP, and return the cast.
1968 /// @brief Cast a value to a "C" string.
1969 static Value *CastToCStr(Value *V, Instruction &IP) {
1970 assert(isa<PointerType>(V->getType()) &&
1971 "Can't cast non-pointer type to C string type");
1972 const Type *SBPTy = PointerType::get(Type::Int8Ty);
1973 if (V->getType() != SBPTy)
1974 return new BitCastInst(V, SBPTy, V->getName(), &IP);
1979 // Additional cases that we need to add to this file:
1982 // * cbrt(expN(X)) -> expN(x/3)
1983 // * cbrt(sqrt(x)) -> pow(x,1/6)
1984 // * cbrt(sqrt(x)) -> pow(x,1/9)
1987 // * cos(-x) -> cos(x)
1990 // * exp(log(x)) -> x
1993 // * log(exp(x)) -> x
1994 // * log(x**y) -> y*log(x)
1995 // * log(exp(y)) -> y*log(e)
1996 // * log(exp2(y)) -> y*log(2)
1997 // * log(exp10(y)) -> y*log(10)
1998 // * log(sqrt(x)) -> 0.5*log(x)
1999 // * log(pow(x,y)) -> y*log(x)
2001 // lround, lroundf, lroundl:
2002 // * lround(cnst) -> cnst'
2005 // * memcmp(x,y,l) -> cnst
2006 // (if all arguments are constant and strlen(x) <= l and strlen(y) <= l)
2009 // * memmove(d,s,l,a) -> memcpy(d,s,l,a)
2010 // (if s is a global constant array)
2013 // * pow(exp(x),y) -> exp(x*y)
2014 // * pow(sqrt(x),y) -> pow(x,y*0.5)
2015 // * pow(pow(x,y),z)-> pow(x,y*z)
2018 // * puts("") -> fputc("\n",stdout) (how do we get "stdout"?)
2020 // round, roundf, roundl:
2021 // * round(cnst) -> cnst'
2024 // * signbit(cnst) -> cnst'
2025 // * signbit(nncst) -> 0 (if pstv is a non-negative constant)
2027 // sqrt, sqrtf, sqrtl:
2028 // * sqrt(expN(x)) -> expN(x*0.5)
2029 // * sqrt(Nroot(x)) -> pow(x,1/(2*N))
2030 // * sqrt(pow(x,y)) -> pow(|x|,y*0.5)
2033 // * stpcpy(str, "literal") ->
2034 // llvm.memcpy(str,"literal",strlen("literal")+1,1)
2036 // * strrchr(s,c) -> reverse_offset_of_in(c,s)
2037 // (if c is a constant integer and s is a constant string)
2038 // * strrchr(s1,0) -> strchr(s1,0)
2041 // * strncat(x,y,0) -> x
2042 // * strncat(x,y,0) -> x (if strlen(y) = 0)
2043 // * strncat(x,y,l) -> strcat(x,y) (if y and l are constants an l > strlen(y))
2046 // * strncpy(d,s,0) -> d
2047 // * strncpy(d,s,l) -> memcpy(d,s,l,1)
2048 // (if s and l are constants)
2051 // * strpbrk(s,a) -> offset_in_for(s,a)
2052 // (if s and a are both constant strings)
2053 // * strpbrk(s,"") -> 0
2054 // * strpbrk(s,a) -> strchr(s,a[0]) (if a is constant string of length 1)
2057 // * strspn(s,a) -> const_int (if both args are constant)
2058 // * strspn("",a) -> 0
2059 // * strspn(s,"") -> 0
2060 // * strcspn(s,a) -> const_int (if both args are constant)
2061 // * strcspn("",a) -> 0
2062 // * strcspn(s,"") -> strlen(a)
2065 // * strstr(x,x) -> x
2066 // * strstr(s1,s2) -> offset_of_s2_in(s1)
2067 // (if s1 and s2 are constant strings)
2070 // * tan(atan(x)) -> x
2072 // trunc, truncf, truncl:
2073 // * trunc(cnst) -> cnst'