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/Debug.h"
30 #include "llvm/Target/TargetData.h"
31 #include "llvm/Transforms/IPO.h"
36 /// This statistic keeps track of the total number of library calls that have
37 /// been simplified regardless of which call it is.
38 Statistic<> SimplifiedLibCalls("simplify-libcalls",
39 "Number of library calls simplified");
41 // Forward declarations
42 class LibCallOptimization;
43 class SimplifyLibCalls;
45 /// This list is populated by the constructor for LibCallOptimization class.
46 /// Therefore all subclasses are registered here at static initialization time
47 /// and this list is what the SimplifyLibCalls pass uses to apply the individual
48 /// optimizations to the call sites.
49 /// @brief The list of optimizations deriving from LibCallOptimization
50 static LibCallOptimization *OptList = 0;
52 /// This class is the abstract base class for the set of optimizations that
53 /// corresponds to one library call. The SimplifyLibCalls pass will call the
54 /// ValidateCalledFunction method to ask the optimization if a given Function
55 /// is the kind that the optimization can handle. If the subclass returns true,
56 /// then SImplifyLibCalls will also call the OptimizeCall method to perform,
57 /// or attempt to perform, the optimization(s) for the library call. Otherwise,
58 /// OptimizeCall won't be called. Subclasses are responsible for providing the
59 /// name of the library call (strlen, strcpy, etc.) to the LibCallOptimization
60 /// constructor. This is used to efficiently select which call instructions to
61 /// optimize. The criteria for a "lib call" is "anything with well known
62 /// semantics", typically a library function that is defined by an international
63 /// standard. Because the semantics are well known, the optimizations can
64 /// generally short-circuit actually calling the function if there's a simpler
65 /// way (e.g. strlen(X) can be reduced to a constant if X is a constant global).
66 /// @brief Base class for library call optimizations
67 class LibCallOptimization {
68 LibCallOptimization **Prev, *Next;
69 const char *FunctionName; ///< Name of the library call we optimize
71 Statistic<> occurrences; ///< debug statistic (-debug-only=simplify-libcalls)
74 /// The \p fname argument must be the name of the library function being
75 /// optimized by the subclass.
76 /// @brief Constructor that registers the optimization.
77 LibCallOptimization(const char *FName, const char *Description)
80 , occurrences("simplify-libcalls", Description)
83 // Register this optimizer in the list of optimizations.
87 if (Next) Next->Prev = &Next;
90 /// getNext - All libcall optimizations are chained together into a list,
91 /// return the next one in the list.
92 LibCallOptimization *getNext() { return Next; }
94 /// @brief Deregister from the optlist
95 virtual ~LibCallOptimization() {
97 if (Next) Next->Prev = Prev;
100 /// The implementation of this function in subclasses should determine if
101 /// \p F is suitable for the optimization. This method is called by
102 /// SimplifyLibCalls::runOnModule to short circuit visiting all the call
103 /// sites of such a function if that function is not suitable in the first
104 /// place. If the called function is suitabe, this method should return true;
105 /// false, otherwise. This function should also perform any lazy
106 /// initialization that the LibCallOptimization needs to do, if its to return
107 /// true. This avoids doing initialization until the optimizer is actually
108 /// going to be called upon to do some optimization.
109 /// @brief Determine if the function is suitable for optimization
110 virtual bool ValidateCalledFunction(
111 const Function* F, ///< The function that is the target of call sites
112 SimplifyLibCalls& SLC ///< The pass object invoking us
115 /// The implementations of this function in subclasses is the heart of the
116 /// SimplifyLibCalls algorithm. Sublcasses of this class implement
117 /// OptimizeCall to determine if (a) the conditions are right for optimizing
118 /// the call and (b) to perform the optimization. If an action is taken
119 /// against ci, the subclass is responsible for returning true and ensuring
120 /// that ci is erased from its parent.
121 /// @brief Optimize a call, if possible.
122 virtual bool OptimizeCall(
123 CallInst* ci, ///< The call instruction that should be optimized.
124 SimplifyLibCalls& SLC ///< The pass object invoking us
127 /// @brief Get the name of the library call being optimized
128 const char *getFunctionName() const { return FunctionName; }
130 /// @brief Called by SimplifyLibCalls to update the occurrences statistic.
133 DEBUG(++occurrences);
138 /// This class is an LLVM Pass that applies each of the LibCallOptimization
139 /// instances to all the call sites in a module, relatively efficiently. The
140 /// purpose of this pass is to provide optimizations for calls to well-known
141 /// functions with well-known semantics, such as those in the c library. The
142 /// class provides the basic infrastructure for handling runOnModule. Whenever
143 /// this pass finds a function call, it asks the appropriate optimizer to
144 /// validate the call (ValidateLibraryCall). If it is validated, then
145 /// the OptimizeCall method is also called.
146 /// @brief A ModulePass for optimizing well-known function calls.
147 class SimplifyLibCalls : public ModulePass {
149 /// We need some target data for accurate signature details that are
150 /// target dependent. So we require target data in our AnalysisUsage.
151 /// @brief Require TargetData from AnalysisUsage.
152 virtual void getAnalysisUsage(AnalysisUsage& Info) const {
153 // Ask that the TargetData analysis be performed before us so we can use
155 Info.addRequired<TargetData>();
158 /// For this pass, process all of the function calls in the module, calling
159 /// ValidateLibraryCall and OptimizeCall as appropriate.
160 /// @brief Run all the lib call optimizations on a Module.
161 virtual bool runOnModule(Module &M) {
165 hash_map<std::string, LibCallOptimization*> OptznMap;
166 for (LibCallOptimization *Optzn = OptList; Optzn; Optzn = Optzn->getNext())
167 OptznMap[Optzn->getFunctionName()] = Optzn;
169 // The call optimizations can be recursive. That is, the optimization might
170 // generate a call to another function which can also be optimized. This way
171 // we make the LibCallOptimization instances very specific to the case they
172 // handle. It also means we need to keep running over the function calls in
173 // the module until we don't get any more optimizations possible.
174 bool found_optimization = false;
176 found_optimization = false;
177 for (Module::iterator FI = M.begin(), FE = M.end(); FI != FE; ++FI) {
178 // All the "well-known" functions are external and have external linkage
179 // because they live in a runtime library somewhere and were (probably)
180 // not compiled by LLVM. So, we only act on external functions that
181 // have external linkage and non-empty uses.
182 if (!FI->isExternal() || !FI->hasExternalLinkage() || FI->use_empty())
185 // Get the optimization class that pertains to this function
186 hash_map<std::string, LibCallOptimization*>::iterator OMI =
187 OptznMap.find(FI->getName());
188 if (OMI == OptznMap.end()) continue;
190 LibCallOptimization *CO = OMI->second;
192 // Make sure the called function is suitable for the optimization
193 if (!CO->ValidateCalledFunction(FI, *this))
196 // Loop over each of the uses of the function
197 for (Value::use_iterator UI = FI->use_begin(), UE = FI->use_end();
199 // If the use of the function is a call instruction
200 if (CallInst* CI = dyn_cast<CallInst>(*UI++)) {
201 // Do the optimization on the LibCallOptimization.
202 if (CO->OptimizeCall(CI, *this)) {
203 ++SimplifiedLibCalls;
204 found_optimization = result = true;
210 } while (found_optimization);
215 /// @brief Return the *current* module we're working on.
216 Module* getModule() const { return M; }
218 /// @brief Return the *current* target data for the module we're working on.
219 TargetData* getTargetData() const { return TD; }
221 /// @brief Return the size_t type -- syntactic shortcut
222 const Type* getIntPtrType() const { return TD->getIntPtrType(); }
224 /// @brief Return a Function* for the fputc libcall
225 Function* get_fputc(const Type* FILEptr_type) {
227 fputc_func = M->getOrInsertFunction("fputc", Type::IntTy, Type::IntTy,
232 /// @brief Return a Function* for the fwrite libcall
233 Function* get_fwrite(const Type* FILEptr_type) {
235 fwrite_func = M->getOrInsertFunction("fwrite", TD->getIntPtrType(),
236 PointerType::get(Type::SByteTy),
243 /// @brief Return a Function* for the sqrt libcall
244 Function* get_sqrt() {
246 sqrt_func = M->getOrInsertFunction("sqrt", Type::DoubleTy,
247 Type::DoubleTy, NULL);
251 /// @brief Return a Function* for the strlen libcall
252 Function* get_strcpy() {
254 strcpy_func = M->getOrInsertFunction("strcpy",
255 PointerType::get(Type::SByteTy),
256 PointerType::get(Type::SByteTy),
257 PointerType::get(Type::SByteTy),
262 /// @brief Return a Function* for the strlen libcall
263 Function* get_strlen() {
265 strlen_func = M->getOrInsertFunction("strlen", TD->getIntPtrType(),
266 PointerType::get(Type::SByteTy),
271 /// @brief Return a Function* for the memchr libcall
272 Function* get_memchr() {
274 memchr_func = M->getOrInsertFunction("memchr",
275 PointerType::get(Type::SByteTy),
276 PointerType::get(Type::SByteTy),
277 Type::IntTy, TD->getIntPtrType(),
282 /// @brief Return a Function* for the memcpy libcall
283 Function* get_memcpy() {
285 const Type *SBP = PointerType::get(Type::SByteTy);
286 memcpy_func = M->getOrInsertFunction("llvm.memcpy", Type::VoidTy,SBP, SBP,
287 TD->getIntPtrType(), Type::UIntTy, NULL);
292 Function *getUnaryFloatFunction(const char *Name, Function *&Cache) {
294 Cache = M->getOrInsertFunction(Name, Type::FloatTy, Type::FloatTy, NULL);
298 Function *get_floorf() { return getUnaryFloatFunction("floorf", floorf_func);}
299 Function *get_ceilf() { return getUnaryFloatFunction( "ceilf", ceilf_func);}
300 Function *get_roundf() { return getUnaryFloatFunction("roundf", roundf_func);}
301 Function *get_rintf() { return getUnaryFloatFunction( "rintf", rintf_func);}
302 Function *get_nearbyintf() { return getUnaryFloatFunction("nearbyintf",
305 /// @brief Reset our cached data for a new Module
306 void reset(Module& mod) {
308 TD = &getAnalysis<TargetData>();
324 /// Caches for function pointers.
325 Function *fputc_func, *fwrite_func;
326 Function *memcpy_func, *memchr_func;
328 Function *strcpy_func, *strlen_func;
329 Function *floorf_func, *ceilf_func, *roundf_func;
330 Function *rintf_func, *nearbyintf_func;
331 Module *M; ///< Cached Module
332 TargetData *TD; ///< Cached TargetData
336 RegisterOpt<SimplifyLibCalls>
337 X("simplify-libcalls","Simplify well-known library calls");
339 } // anonymous namespace
341 // The only public symbol in this file which just instantiates the pass object
342 ModulePass *llvm::createSimplifyLibCallsPass() {
343 return new SimplifyLibCalls();
346 // Classes below here, in the anonymous namespace, are all subclasses of the
347 // LibCallOptimization class, each implementing all optimizations possible for a
348 // single well-known library call. Each has a static singleton instance that
349 // auto registers it into the "optlist" global above.
352 // Forward declare utility functions.
353 bool getConstantStringLength(Value* V, uint64_t& len, ConstantArray** A = 0 );
354 Value *CastToCStr(Value *V, Instruction &IP);
356 /// This LibCallOptimization will find instances of a call to "exit" that occurs
357 /// within the "main" function and change it to a simple "ret" instruction with
358 /// the same value passed to the exit function. When this is done, it splits the
359 /// basic block at the exit(3) call and deletes the call instruction.
360 /// @brief Replace calls to exit in main with a simple return
361 struct ExitInMainOptimization : public LibCallOptimization {
362 ExitInMainOptimization() : LibCallOptimization("exit",
363 "Number of 'exit' calls simplified") {}
365 // Make sure the called function looks like exit (int argument, int return
366 // type, external linkage, not varargs).
367 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
368 return F->arg_size() >= 1 && F->arg_begin()->getType()->isInteger();
371 virtual bool OptimizeCall(CallInst* ci, SimplifyLibCalls& SLC) {
372 // To be careful, we check that the call to exit is coming from "main", that
373 // main has external linkage, and the return type of main and the argument
374 // to exit have the same type.
375 Function *from = ci->getParent()->getParent();
376 if (from->hasExternalLinkage())
377 if (from->getReturnType() == ci->getOperand(1)->getType())
378 if (from->getName() == "main") {
379 // Okay, time to actually do the optimization. First, get the basic
380 // block of the call instruction
381 BasicBlock* bb = ci->getParent();
383 // Create a return instruction that we'll replace the call with.
384 // Note that the argument of the return is the argument of the call
386 ReturnInst* ri = new ReturnInst(ci->getOperand(1), ci);
388 // Split the block at the call instruction which places it in a new
390 bb->splitBasicBlock(ci);
392 // The block split caused a branch instruction to be inserted into
393 // the end of the original block, right after the return instruction
394 // that we put there. That's not a valid block, so delete the branch
396 bb->getInstList().pop_back();
398 // Now we can finally get rid of the call instruction which now lives
399 // in the new basic block.
400 ci->eraseFromParent();
402 // Optimization succeeded, return true.
405 // We didn't pass the criteria for this optimization so return false
408 } ExitInMainOptimizer;
410 /// This LibCallOptimization will simplify a call to the strcat library
411 /// function. The simplification is possible only if the string being
412 /// concatenated is a constant array or a constant expression that results in
413 /// a constant string. In this case we can replace it with strlen + llvm.memcpy
414 /// of the constant string. Both of these calls are further reduced, if possible
415 /// on subsequent passes.
416 /// @brief Simplify the strcat library function.
417 struct StrCatOptimization : public LibCallOptimization {
419 /// @brief Default constructor
420 StrCatOptimization() : LibCallOptimization("strcat",
421 "Number of 'strcat' calls simplified") {}
425 /// @brief Make sure that the "strcat" function has the right prototype
426 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC){
427 if (f->getReturnType() == PointerType::get(Type::SByteTy))
428 if (f->arg_size() == 2)
430 Function::const_arg_iterator AI = f->arg_begin();
431 if (AI++->getType() == PointerType::get(Type::SByteTy))
432 if (AI->getType() == PointerType::get(Type::SByteTy))
434 // Indicate this is a suitable call type.
441 /// @brief Optimize the strcat library function
442 virtual bool OptimizeCall(CallInst* ci, SimplifyLibCalls& SLC) {
443 // Extract some information from the instruction
444 Module* M = ci->getParent()->getParent()->getParent();
445 Value* dest = ci->getOperand(1);
446 Value* src = ci->getOperand(2);
448 // Extract the initializer (while making numerous checks) from the
449 // source operand of the call to strcat. If we get null back, one of
450 // a variety of checks in get_GVInitializer failed
452 if (!getConstantStringLength(src,len))
455 // Handle the simple, do-nothing case
457 ci->replaceAllUsesWith(dest);
458 ci->eraseFromParent();
462 // Increment the length because we actually want to memcpy the null
463 // terminator as well.
466 // We need to find the end of the destination string. That's where the
467 // memory is to be moved to. We just generate a call to strlen (further
468 // optimized in another pass). Note that the SLC.get_strlen() call
469 // caches the Function* for us.
470 CallInst* strlen_inst =
471 new CallInst(SLC.get_strlen(), dest, dest->getName()+".len",ci);
473 // Now that we have the destination's length, we must index into the
474 // destination's pointer to get the actual memcpy destination (end of
475 // the string .. we're concatenating).
476 std::vector<Value*> idx;
477 idx.push_back(strlen_inst);
478 GetElementPtrInst* gep =
479 new GetElementPtrInst(dest,idx,dest->getName()+".indexed",ci);
481 // We have enough information to now generate the memcpy call to
482 // do the concatenation for us.
483 std::vector<Value*> vals;
484 vals.push_back(gep); // destination
485 vals.push_back(ci->getOperand(2)); // source
486 vals.push_back(ConstantUInt::get(SLC.getIntPtrType(),len)); // length
487 vals.push_back(ConstantUInt::get(Type::UIntTy,1)); // alignment
488 new CallInst(SLC.get_memcpy(), vals, "", ci);
490 // Finally, substitute the first operand of the strcat call for the
491 // strcat call itself since strcat returns its first operand; and,
492 // kill the strcat CallInst.
493 ci->replaceAllUsesWith(dest);
494 ci->eraseFromParent();
499 /// This LibCallOptimization will simplify a call to the strchr library
500 /// function. It optimizes out cases where the arguments are both constant
501 /// and the result can be determined statically.
502 /// @brief Simplify the strcmp library function.
503 struct StrChrOptimization : public LibCallOptimization {
505 StrChrOptimization() : LibCallOptimization("strchr",
506 "Number of 'strchr' calls simplified") {}
508 /// @brief Make sure that the "strchr" function has the right prototype
509 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC){
510 if (f->getReturnType() == PointerType::get(Type::SByteTy) &&
516 /// @brief Perform the strchr optimizations
517 virtual bool OptimizeCall(CallInst *ci, SimplifyLibCalls &SLC) {
518 // If there aren't three operands, bail
519 if (ci->getNumOperands() != 3)
522 // Check that the first argument to strchr is a constant array of sbyte.
523 // If it is, get the length and data, otherwise return false.
526 if (!getConstantStringLength(ci->getOperand(1),len,&CA))
529 // Check that the second argument to strchr is a constant int, return false
531 ConstantSInt* CSI = dyn_cast<ConstantSInt>(ci->getOperand(2));
533 // Just lower this to memchr since we know the length of the string as
535 Function* f = SLC.get_memchr();
536 std::vector<Value*> args;
537 args.push_back(ci->getOperand(1));
538 args.push_back(ci->getOperand(2));
539 args.push_back(ConstantUInt::get(SLC.getIntPtrType(),len));
540 ci->replaceAllUsesWith( new CallInst(f,args,ci->getName(),ci));
541 ci->eraseFromParent();
545 // Get the character we're looking for
546 int64_t chr = CSI->getValue();
548 // Compute the offset
550 bool char_found = false;
551 for (uint64_t i = 0; i < len; ++i) {
552 if (ConstantSInt* CI = dyn_cast<ConstantSInt>(CA->getOperand(i))) {
553 // Check for the null terminator
554 if (CI->isNullValue())
555 break; // we found end of string
556 else if (CI->getValue() == chr) {
564 // strchr(s,c) -> offset_of_in(c,s)
565 // (if c is a constant integer and s is a constant string)
567 std::vector<Value*> indices;
568 indices.push_back(ConstantUInt::get(Type::ULongTy,offset));
569 GetElementPtrInst* GEP = new GetElementPtrInst(ci->getOperand(1),indices,
570 ci->getOperand(1)->getName()+".strchr",ci);
571 ci->replaceAllUsesWith(GEP);
573 ci->replaceAllUsesWith(
574 ConstantPointerNull::get(PointerType::get(Type::SByteTy)));
576 ci->eraseFromParent();
581 /// This LibCallOptimization will simplify a call to the strcmp library
582 /// function. It optimizes out cases where one or both arguments are constant
583 /// and the result can be determined statically.
584 /// @brief Simplify the strcmp library function.
585 struct StrCmpOptimization : public LibCallOptimization {
587 StrCmpOptimization() : LibCallOptimization("strcmp",
588 "Number of 'strcmp' calls simplified") {}
590 /// @brief Make sure that the "strcmp" function has the right prototype
591 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
592 return F->getReturnType() == Type::IntTy && F->arg_size() == 2;
595 /// @brief Perform the strcmp optimization
596 virtual bool OptimizeCall(CallInst* ci, SimplifyLibCalls& SLC) {
597 // First, check to see if src and destination are the same. If they are,
598 // then the optimization is to replace the CallInst with a constant 0
599 // because the call is a no-op.
600 Value* s1 = ci->getOperand(1);
601 Value* s2 = ci->getOperand(2);
604 ci->replaceAllUsesWith(ConstantInt::get(Type::IntTy,0));
605 ci->eraseFromParent();
609 bool isstr_1 = false;
612 if (getConstantStringLength(s1,len_1,&A1)) {
615 // strcmp("",x) -> *x
617 new LoadInst(CastToCStr(s2,*ci), ci->getName()+".load",ci);
619 new CastInst(load,Type::IntTy,ci->getName()+".int",ci);
620 ci->replaceAllUsesWith(cast);
621 ci->eraseFromParent();
626 bool isstr_2 = false;
629 if (getConstantStringLength(s2, len_2, &A2)) {
632 // strcmp(x,"") -> *x
634 new LoadInst(CastToCStr(s1,*ci),ci->getName()+".val",ci);
636 new CastInst(load,Type::IntTy,ci->getName()+".int",ci);
637 ci->replaceAllUsesWith(cast);
638 ci->eraseFromParent();
643 if (isstr_1 && isstr_2) {
644 // strcmp(x,y) -> cnst (if both x and y are constant strings)
645 std::string str1 = A1->getAsString();
646 std::string str2 = A2->getAsString();
647 int result = strcmp(str1.c_str(), str2.c_str());
648 ci->replaceAllUsesWith(ConstantSInt::get(Type::IntTy,result));
649 ci->eraseFromParent();
656 /// This LibCallOptimization will simplify a call to the strncmp library
657 /// function. It optimizes out cases where one or both arguments are constant
658 /// and the result can be determined statically.
659 /// @brief Simplify the strncmp library function.
660 struct StrNCmpOptimization : public LibCallOptimization {
662 StrNCmpOptimization() : LibCallOptimization("strncmp",
663 "Number of 'strncmp' calls simplified") {}
665 /// @brief Make sure that the "strncmp" function has the right prototype
666 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC){
667 if (f->getReturnType() == Type::IntTy && f->arg_size() == 3)
672 /// @brief Perform the strncpy optimization
673 virtual bool OptimizeCall(CallInst *ci, SimplifyLibCalls &SLC) {
674 // First, check to see if src and destination are the same. If they are,
675 // then the optimization is to replace the CallInst with a constant 0
676 // because the call is a no-op.
677 Value* s1 = ci->getOperand(1);
678 Value* s2 = ci->getOperand(2);
680 // strncmp(x,x,l) -> 0
681 ci->replaceAllUsesWith(ConstantInt::get(Type::IntTy,0));
682 ci->eraseFromParent();
686 // Check the length argument, if it is Constant zero then the strings are
688 uint64_t len_arg = 0;
689 bool len_arg_is_const = false;
690 if (ConstantInt* len_CI = dyn_cast<ConstantInt>(ci->getOperand(3))) {
691 len_arg_is_const = true;
692 len_arg = len_CI->getRawValue();
694 // strncmp(x,y,0) -> 0
695 ci->replaceAllUsesWith(ConstantInt::get(Type::IntTy,0));
696 ci->eraseFromParent();
701 bool isstr_1 = false;
704 if (getConstantStringLength(s1, len_1, &A1)) {
707 // strncmp("",x) -> *x
708 LoadInst* load = new LoadInst(s1,ci->getName()+".load",ci);
710 new CastInst(load,Type::IntTy,ci->getName()+".int",ci);
711 ci->replaceAllUsesWith(cast);
712 ci->eraseFromParent();
717 bool isstr_2 = false;
720 if (getConstantStringLength(s2,len_2,&A2)) {
723 // strncmp(x,"") -> *x
724 LoadInst* load = new LoadInst(s2,ci->getName()+".val",ci);
726 new CastInst(load,Type::IntTy,ci->getName()+".int",ci);
727 ci->replaceAllUsesWith(cast);
728 ci->eraseFromParent();
733 if (isstr_1 && isstr_2 && len_arg_is_const) {
734 // strncmp(x,y,const) -> constant
735 std::string str1 = A1->getAsString();
736 std::string str2 = A2->getAsString();
737 int result = strncmp(str1.c_str(), str2.c_str(), len_arg);
738 ci->replaceAllUsesWith(ConstantSInt::get(Type::IntTy,result));
739 ci->eraseFromParent();
746 /// This LibCallOptimization will simplify a call to the strcpy library
747 /// function. Two optimizations are possible:
748 /// (1) If src and dest are the same and not volatile, just return dest
749 /// (2) If the src is a constant then we can convert to llvm.memmove
750 /// @brief Simplify the strcpy library function.
751 struct StrCpyOptimization : public LibCallOptimization {
753 StrCpyOptimization() : LibCallOptimization("strcpy",
754 "Number of 'strcpy' calls simplified") {}
756 /// @brief Make sure that the "strcpy" function has the right prototype
757 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC){
758 if (f->getReturnType() == PointerType::get(Type::SByteTy))
759 if (f->arg_size() == 2) {
760 Function::const_arg_iterator AI = f->arg_begin();
761 if (AI++->getType() == PointerType::get(Type::SByteTy))
762 if (AI->getType() == PointerType::get(Type::SByteTy)) {
763 // Indicate this is a suitable call type.
770 /// @brief Perform the strcpy optimization
771 virtual bool OptimizeCall(CallInst* ci, SimplifyLibCalls& SLC) {
772 // First, check to see if src and destination are the same. If they are,
773 // then the optimization is to replace the CallInst with the destination
774 // because the call is a no-op. Note that this corresponds to the
775 // degenerate strcpy(X,X) case which should have "undefined" results
776 // according to the C specification. However, it occurs sometimes and
777 // we optimize it as a no-op.
778 Value* dest = ci->getOperand(1);
779 Value* src = ci->getOperand(2);
781 ci->replaceAllUsesWith(dest);
782 ci->eraseFromParent();
786 // Get the length of the constant string referenced by the second operand,
787 // the "src" parameter. Fail the optimization if we can't get the length
788 // (note that getConstantStringLength does lots of checks to make sure this
791 if (!getConstantStringLength(ci->getOperand(2),len))
794 // If the constant string's length is zero we can optimize this by just
795 // doing a store of 0 at the first byte of the destination
797 new StoreInst(ConstantInt::get(Type::SByteTy,0),ci->getOperand(1),ci);
798 ci->replaceAllUsesWith(dest);
799 ci->eraseFromParent();
803 // Increment the length because we actually want to memcpy the null
804 // terminator as well.
807 // Extract some information from the instruction
808 Module* M = ci->getParent()->getParent()->getParent();
810 // We have enough information to now generate the memcpy call to
811 // do the concatenation for us.
812 std::vector<Value*> vals;
813 vals.push_back(dest); // destination
814 vals.push_back(src); // source
815 vals.push_back(ConstantUInt::get(SLC.getIntPtrType(),len)); // length
816 vals.push_back(ConstantUInt::get(Type::UIntTy,1)); // alignment
817 new CallInst(SLC.get_memcpy(), vals, "", ci);
819 // Finally, substitute the first operand of the strcat call for the
820 // strcat call itself since strcat returns its first operand; and,
821 // kill the strcat CallInst.
822 ci->replaceAllUsesWith(dest);
823 ci->eraseFromParent();
828 /// This LibCallOptimization will simplify a call to the strlen library
829 /// function by replacing it with a constant value if the string provided to
830 /// it is a constant array.
831 /// @brief Simplify the strlen library function.
832 struct StrLenOptimization : public LibCallOptimization {
833 StrLenOptimization() : LibCallOptimization("strlen",
834 "Number of 'strlen' calls simplified") {}
836 /// @brief Make sure that the "strlen" function has the right prototype
837 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC)
839 if (f->getReturnType() == SLC.getTargetData()->getIntPtrType())
840 if (f->arg_size() == 1)
841 if (Function::const_arg_iterator AI = f->arg_begin())
842 if (AI->getType() == PointerType::get(Type::SByteTy))
847 /// @brief Perform the strlen optimization
848 virtual bool OptimizeCall(CallInst* ci, SimplifyLibCalls& SLC)
850 // Make sure we're dealing with an sbyte* here.
851 Value* str = ci->getOperand(1);
852 if (str->getType() != PointerType::get(Type::SByteTy))
855 // Does the call to strlen have exactly one use?
857 // Is that single use a binary operator?
858 if (BinaryOperator* bop = dyn_cast<BinaryOperator>(ci->use_back()))
859 // Is it compared against a constant integer?
860 if (ConstantInt* CI = dyn_cast<ConstantInt>(bop->getOperand(1)))
862 // Get the value the strlen result is compared to
863 uint64_t val = CI->getRawValue();
865 // If its compared against length 0 with == or !=
867 (bop->getOpcode() == Instruction::SetEQ ||
868 bop->getOpcode() == Instruction::SetNE))
870 // strlen(x) != 0 -> *x != 0
871 // strlen(x) == 0 -> *x == 0
872 LoadInst* load = new LoadInst(str,str->getName()+".first",ci);
873 BinaryOperator* rbop = BinaryOperator::create(bop->getOpcode(),
874 load, ConstantSInt::get(Type::SByteTy,0),
875 bop->getName()+".strlen", ci);
876 bop->replaceAllUsesWith(rbop);
877 bop->eraseFromParent();
878 ci->eraseFromParent();
883 // Get the length of the constant string operand
885 if (!getConstantStringLength(ci->getOperand(1),len))
888 // strlen("xyz") -> 3 (for example)
889 const Type *Ty = SLC.getTargetData()->getIntPtrType();
891 ci->replaceAllUsesWith(ConstantSInt::get(Ty, len));
893 ci->replaceAllUsesWith(ConstantUInt::get(Ty, len));
895 ci->eraseFromParent();
900 /// IsOnlyUsedInEqualsComparison - Return true if it only matters that the value
901 /// is equal or not-equal to zero.
902 static bool IsOnlyUsedInEqualsZeroComparison(Instruction *I) {
903 for (Value::use_iterator UI = I->use_begin(), E = I->use_end();
905 Instruction *User = cast<Instruction>(*UI);
906 if (User->getOpcode() == Instruction::SetNE ||
907 User->getOpcode() == Instruction::SetEQ) {
908 if (isa<Constant>(User->getOperand(1)) &&
909 cast<Constant>(User->getOperand(1))->isNullValue())
911 } else if (CastInst *CI = dyn_cast<CastInst>(User))
912 if (CI->getType() == Type::BoolTy)
914 // Unknown instruction.
920 /// This memcmpOptimization will simplify a call to the memcmp library
922 struct memcmpOptimization : public LibCallOptimization {
923 /// @brief Default Constructor
925 : LibCallOptimization("memcmp", "Number of 'memcmp' calls simplified") {}
927 /// @brief Make sure that the "memcmp" function has the right prototype
928 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &TD) {
929 Function::const_arg_iterator AI = F->arg_begin();
930 if (F->arg_size() != 3 || !isa<PointerType>(AI->getType())) return false;
931 if (!isa<PointerType>((++AI)->getType())) return false;
932 if (!(++AI)->getType()->isInteger()) return false;
933 if (!F->getReturnType()->isInteger()) return false;
937 /// Because of alignment and instruction information that we don't have, we
938 /// leave the bulk of this to the code generators.
940 /// Note that we could do much more if we could force alignment on otherwise
941 /// small aligned allocas, or if we could indicate that loads have a small
943 virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &TD) {
944 Value *LHS = CI->getOperand(1), *RHS = CI->getOperand(2);
946 // If the two operands are the same, return zero.
948 // memcmp(s,s,x) -> 0
949 CI->replaceAllUsesWith(Constant::getNullValue(CI->getType()));
950 CI->eraseFromParent();
954 // Make sure we have a constant length.
955 ConstantInt *LenC = dyn_cast<ConstantInt>(CI->getOperand(3));
956 if (!LenC) return false;
957 uint64_t Len = LenC->getRawValue();
959 // If the length is zero, this returns 0.
962 // memcmp(s1,s2,0) -> 0
963 CI->replaceAllUsesWith(Constant::getNullValue(CI->getType()));
964 CI->eraseFromParent();
967 // memcmp(S1,S2,1) -> *(ubyte*)S1 - *(ubyte*)S2
968 const Type *UCharPtr = PointerType::get(Type::UByteTy);
969 CastInst *Op1Cast = new CastInst(LHS, UCharPtr, LHS->getName(), CI);
970 CastInst *Op2Cast = new CastInst(RHS, UCharPtr, RHS->getName(), CI);
971 Value *S1V = new LoadInst(Op1Cast, LHS->getName()+".val", CI);
972 Value *S2V = new LoadInst(Op2Cast, RHS->getName()+".val", CI);
973 Value *RV = BinaryOperator::createSub(S1V, S2V, CI->getName()+".diff",CI);
974 if (RV->getType() != CI->getType())
975 RV = new CastInst(RV, CI->getType(), RV->getName(), CI);
976 CI->replaceAllUsesWith(RV);
977 CI->eraseFromParent();
981 if (IsOnlyUsedInEqualsZeroComparison(CI)) {
982 // TODO: IF both are aligned, use a short load/compare.
984 // memcmp(S1,S2,2) -> S1[0]-S2[0] | S1[1]-S2[1] iff only ==/!= 0 matters
985 const Type *UCharPtr = PointerType::get(Type::UByteTy);
986 CastInst *Op1Cast = new CastInst(LHS, UCharPtr, LHS->getName(), CI);
987 CastInst *Op2Cast = new CastInst(RHS, UCharPtr, RHS->getName(), CI);
988 Value *S1V1 = new LoadInst(Op1Cast, LHS->getName()+".val1", CI);
989 Value *S2V1 = new LoadInst(Op2Cast, RHS->getName()+".val1", CI);
990 Value *D1 = BinaryOperator::createSub(S1V1, S2V1,
991 CI->getName()+".d1", CI);
992 Constant *One = ConstantInt::get(Type::IntTy, 1);
993 Value *G1 = new GetElementPtrInst(Op1Cast, One, "next1v", CI);
994 Value *G2 = new GetElementPtrInst(Op2Cast, One, "next2v", CI);
995 Value *S1V2 = new LoadInst(G1, LHS->getName()+".val2", CI);
996 Value *S2V2 = new LoadInst(G1, RHS->getName()+".val2", CI);
997 Value *D2 = BinaryOperator::createSub(S1V2, S2V2,
998 CI->getName()+".d1", CI);
999 Value *Or = BinaryOperator::createOr(D1, D2, CI->getName()+".res", CI);
1000 if (Or->getType() != CI->getType())
1001 Or = new CastInst(Or, CI->getType(), Or->getName(), CI);
1002 CI->replaceAllUsesWith(Or);
1003 CI->eraseFromParent();
1016 /// This LibCallOptimization will simplify a call to the memcpy library
1017 /// function by expanding it out to a single store of size 0, 1, 2, 4, or 8
1018 /// bytes depending on the length of the string and the alignment. Additional
1019 /// optimizations are possible in code generation (sequence of immediate store)
1020 /// @brief Simplify the memcpy library function.
1021 struct LLVMMemCpyOptimization : public LibCallOptimization {
1022 /// @brief Default Constructor
1023 LLVMMemCpyOptimization() : LibCallOptimization("llvm.memcpy",
1024 "Number of 'llvm.memcpy' calls simplified") {}
1027 /// @brief Subclass Constructor
1028 LLVMMemCpyOptimization(const char* fname, const char* desc)
1029 : LibCallOptimization(fname, desc) {}
1032 /// @brief Make sure that the "memcpy" function has the right prototype
1033 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& TD) {
1034 // Just make sure this has 4 arguments per LLVM spec.
1035 return (f->arg_size() == 4);
1038 /// Because of alignment and instruction information that we don't have, we
1039 /// leave the bulk of this to the code generators. The optimization here just
1040 /// deals with a few degenerate cases where the length of the string and the
1041 /// alignment match the sizes of our intrinsic types so we can do a load and
1042 /// store instead of the memcpy call.
1043 /// @brief Perform the memcpy optimization.
1044 virtual bool OptimizeCall(CallInst* ci, SimplifyLibCalls& TD) {
1045 // Make sure we have constant int values to work with
1046 ConstantInt* LEN = dyn_cast<ConstantInt>(ci->getOperand(3));
1049 ConstantInt* ALIGN = dyn_cast<ConstantInt>(ci->getOperand(4));
1053 // If the length is larger than the alignment, we can't optimize
1054 uint64_t len = LEN->getRawValue();
1055 uint64_t alignment = ALIGN->getRawValue();
1057 alignment = 1; // Alignment 0 is identity for alignment 1
1058 if (len > alignment)
1061 // Get the type we will cast to, based on size of the string
1062 Value* dest = ci->getOperand(1);
1063 Value* src = ci->getOperand(2);
1068 // memcpy(d,s,0,a) -> noop
1069 ci->eraseFromParent();
1071 case 1: castType = Type::SByteTy; break;
1072 case 2: castType = Type::ShortTy; break;
1073 case 4: castType = Type::IntTy; break;
1074 case 8: castType = Type::LongTy; break;
1079 // Cast source and dest to the right sized primitive and then load/store
1081 new CastInst(src,PointerType::get(castType),src->getName()+".cast",ci);
1082 CastInst* DestCast =
1083 new CastInst(dest,PointerType::get(castType),dest->getName()+".cast",ci);
1084 LoadInst* LI = new LoadInst(SrcCast,SrcCast->getName()+".val",ci);
1085 StoreInst* SI = new StoreInst(LI, DestCast, ci);
1086 ci->eraseFromParent();
1089 } LLVMMemCpyOptimizer;
1091 /// This LibCallOptimization will simplify a call to the memmove library
1092 /// function. It is identical to MemCopyOptimization except for the name of
1094 /// @brief Simplify the memmove library function.
1095 struct LLVMMemMoveOptimization : public LLVMMemCpyOptimization {
1096 /// @brief Default Constructor
1097 LLVMMemMoveOptimization() : LLVMMemCpyOptimization("llvm.memmove",
1098 "Number of 'llvm.memmove' calls simplified") {}
1100 } LLVMMemMoveOptimizer;
1102 /// This LibCallOptimization will simplify a call to the memset library
1103 /// function by expanding it out to a single store of size 0, 1, 2, 4, or 8
1104 /// bytes depending on the length argument.
1105 struct LLVMMemSetOptimization : public LibCallOptimization {
1106 /// @brief Default Constructor
1107 LLVMMemSetOptimization() : LibCallOptimization("llvm.memset",
1108 "Number of 'llvm.memset' calls simplified") {}
1111 /// @brief Make sure that the "memset" function has the right prototype
1112 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &TD) {
1113 // Just make sure this has 3 arguments per LLVM spec.
1114 return F->arg_size() == 4;
1117 /// Because of alignment and instruction information that we don't have, we
1118 /// leave the bulk of this to the code generators. The optimization here just
1119 /// deals with a few degenerate cases where the length parameter is constant
1120 /// and the alignment matches the sizes of our intrinsic types so we can do
1121 /// store instead of the memcpy call. Other calls are transformed into the
1122 /// llvm.memset intrinsic.
1123 /// @brief Perform the memset optimization.
1124 virtual bool OptimizeCall(CallInst *ci, SimplifyLibCalls &TD) {
1125 // Make sure we have constant int values to work with
1126 ConstantInt* LEN = dyn_cast<ConstantInt>(ci->getOperand(3));
1129 ConstantInt* ALIGN = dyn_cast<ConstantInt>(ci->getOperand(4));
1133 // Extract the length and alignment
1134 uint64_t len = LEN->getRawValue();
1135 uint64_t alignment = ALIGN->getRawValue();
1137 // Alignment 0 is identity for alignment 1
1141 // If the length is zero, this is a no-op
1143 // memset(d,c,0,a) -> noop
1144 ci->eraseFromParent();
1148 // If the length is larger than the alignment, we can't optimize
1149 if (len > alignment)
1152 // Make sure we have a constant ubyte to work with so we can extract
1153 // the value to be filled.
1154 ConstantUInt* FILL = dyn_cast<ConstantUInt>(ci->getOperand(2));
1157 if (FILL->getType() != Type::UByteTy)
1160 // memset(s,c,n) -> store s, c (for n=1,2,4,8)
1162 // Extract the fill character
1163 uint64_t fill_char = FILL->getValue();
1164 uint64_t fill_value = fill_char;
1166 // Get the type we will cast to, based on size of memory area to fill, and
1167 // and the value we will store there.
1168 Value* dest = ci->getOperand(1);
1172 castType = Type::UByteTy;
1175 castType = Type::UShortTy;
1176 fill_value |= fill_char << 8;
1179 castType = Type::UIntTy;
1180 fill_value |= fill_char << 8 | fill_char << 16 | fill_char << 24;
1183 castType = Type::ULongTy;
1184 fill_value |= fill_char << 8 | fill_char << 16 | fill_char << 24;
1185 fill_value |= fill_char << 32 | fill_char << 40 | fill_char << 48;
1186 fill_value |= fill_char << 56;
1192 // Cast dest to the right sized primitive and then load/store
1193 CastInst* DestCast =
1194 new CastInst(dest,PointerType::get(castType),dest->getName()+".cast",ci);
1195 new StoreInst(ConstantUInt::get(castType,fill_value),DestCast, ci);
1196 ci->eraseFromParent();
1199 } LLVMMemSetOptimizer;
1201 /// This LibCallOptimization will simplify calls to the "pow" library
1202 /// function. It looks for cases where the result of pow is well known and
1203 /// substitutes the appropriate value.
1204 /// @brief Simplify the pow library function.
1205 struct PowOptimization : public LibCallOptimization {
1207 /// @brief Default Constructor
1208 PowOptimization() : LibCallOptimization("pow",
1209 "Number of 'pow' calls simplified") {}
1211 /// @brief Make sure that the "pow" function has the right prototype
1212 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC){
1213 // Just make sure this has 2 arguments
1214 return (f->arg_size() == 2);
1217 /// @brief Perform the pow optimization.
1218 virtual bool OptimizeCall(CallInst *ci, SimplifyLibCalls &SLC) {
1219 const Type *Ty = cast<Function>(ci->getOperand(0))->getReturnType();
1220 Value* base = ci->getOperand(1);
1221 Value* expn = ci->getOperand(2);
1222 if (ConstantFP *Op1 = dyn_cast<ConstantFP>(base)) {
1223 double Op1V = Op1->getValue();
1225 // pow(1.0,x) -> 1.0
1226 ci->replaceAllUsesWith(ConstantFP::get(Ty,1.0));
1227 ci->eraseFromParent();
1230 } else if (ConstantFP* Op2 = dyn_cast<ConstantFP>(expn)) {
1231 double Op2V = Op2->getValue();
1233 // pow(x,0.0) -> 1.0
1234 ci->replaceAllUsesWith(ConstantFP::get(Ty,1.0));
1235 ci->eraseFromParent();
1237 } else if (Op2V == 0.5) {
1238 // pow(x,0.5) -> sqrt(x)
1239 CallInst* sqrt_inst = new CallInst(SLC.get_sqrt(), base,
1240 ci->getName()+".pow",ci);
1241 ci->replaceAllUsesWith(sqrt_inst);
1242 ci->eraseFromParent();
1244 } else if (Op2V == 1.0) {
1246 ci->replaceAllUsesWith(base);
1247 ci->eraseFromParent();
1249 } else if (Op2V == -1.0) {
1250 // pow(x,-1.0) -> 1.0/x
1251 BinaryOperator* div_inst= BinaryOperator::createDiv(
1252 ConstantFP::get(Ty,1.0), base, ci->getName()+".pow", ci);
1253 ci->replaceAllUsesWith(div_inst);
1254 ci->eraseFromParent();
1258 return false; // opt failed
1262 /// This LibCallOptimization will simplify calls to the "fprintf" library
1263 /// function. It looks for cases where the result of fprintf is not used and the
1264 /// operation can be reduced to something simpler.
1265 /// @brief Simplify the pow library function.
1266 struct FPrintFOptimization : public LibCallOptimization {
1268 /// @brief Default Constructor
1269 FPrintFOptimization() : LibCallOptimization("fprintf",
1270 "Number of 'fprintf' calls simplified") {}
1272 /// @brief Make sure that the "fprintf" function has the right prototype
1273 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC){
1274 // Just make sure this has at least 2 arguments
1275 return (f->arg_size() >= 2);
1278 /// @brief Perform the fprintf optimization.
1279 virtual bool OptimizeCall(CallInst* ci, SimplifyLibCalls& SLC) {
1280 // If the call has more than 3 operands, we can't optimize it
1281 if (ci->getNumOperands() > 4 || ci->getNumOperands() <= 2)
1284 // If the result of the fprintf call is used, none of these optimizations
1286 if (!ci->use_empty())
1289 // All the optimizations depend on the length of the second argument and the
1290 // fact that it is a constant string array. Check that now
1292 ConstantArray* CA = 0;
1293 if (!getConstantStringLength(ci->getOperand(2), len, &CA))
1296 if (ci->getNumOperands() == 3) {
1297 // Make sure there's no % in the constant array
1298 for (unsigned i = 0; i < len; ++i) {
1299 if (ConstantInt* CI = dyn_cast<ConstantInt>(CA->getOperand(i))) {
1300 // Check for the null terminator
1301 if (CI->getRawValue() == '%')
1302 return false; // we found end of string
1308 // fprintf(file,fmt) -> fwrite(fmt,strlen(fmt),file)
1309 const Type* FILEptr_type = ci->getOperand(1)->getType();
1310 Function* fwrite_func = SLC.get_fwrite(FILEptr_type);
1314 // Make sure that the fprintf() and fwrite() functions both take the
1315 // same type of char pointer.
1316 if (ci->getOperand(2)->getType() !=
1317 fwrite_func->getFunctionType()->getParamType(0))
1320 std::vector<Value*> args;
1321 args.push_back(ci->getOperand(2));
1322 args.push_back(ConstantUInt::get(SLC.getIntPtrType(),len));
1323 args.push_back(ConstantUInt::get(SLC.getIntPtrType(),1));
1324 args.push_back(ci->getOperand(1));
1325 new CallInst(fwrite_func,args,ci->getName(),ci);
1326 ci->replaceAllUsesWith(ConstantSInt::get(Type::IntTy,len));
1327 ci->eraseFromParent();
1331 // The remaining optimizations require the format string to be length 2
1336 // The first character has to be a %
1337 if (ConstantInt* CI = dyn_cast<ConstantInt>(CA->getOperand(0)))
1338 if (CI->getRawValue() != '%')
1341 // Get the second character and switch on its value
1342 ConstantInt* CI = dyn_cast<ConstantInt>(CA->getOperand(1));
1343 switch (CI->getRawValue()) {
1347 ConstantArray* CA = 0;
1348 if (!getConstantStringLength(ci->getOperand(3), len, &CA))
1351 // fprintf(file,"%s",str) -> fwrite(fmt,strlen(fmt),1,file)
1352 const Type* FILEptr_type = ci->getOperand(1)->getType();
1353 Function* fwrite_func = SLC.get_fwrite(FILEptr_type);
1356 std::vector<Value*> args;
1357 args.push_back(CastToCStr(ci->getOperand(3), *ci));
1358 args.push_back(ConstantUInt::get(SLC.getIntPtrType(),len));
1359 args.push_back(ConstantUInt::get(SLC.getIntPtrType(),1));
1360 args.push_back(ci->getOperand(1));
1361 new CallInst(fwrite_func,args,ci->getName(),ci);
1362 ci->replaceAllUsesWith(ConstantSInt::get(Type::IntTy,len));
1367 ConstantInt* CI = dyn_cast<ConstantInt>(ci->getOperand(3));
1371 const Type* FILEptr_type = ci->getOperand(1)->getType();
1372 Function* fputc_func = SLC.get_fputc(FILEptr_type);
1375 CastInst* cast = new CastInst(CI,Type::IntTy,CI->getName()+".int",ci);
1376 new CallInst(fputc_func,cast,ci->getOperand(1),"",ci);
1377 ci->replaceAllUsesWith(ConstantSInt::get(Type::IntTy,1));
1383 ci->eraseFromParent();
1388 /// This LibCallOptimization will simplify calls to the "sprintf" library
1389 /// function. It looks for cases where the result of sprintf is not used and the
1390 /// operation can be reduced to something simpler.
1391 /// @brief Simplify the pow library function.
1392 struct SPrintFOptimization : public LibCallOptimization {
1394 /// @brief Default Constructor
1395 SPrintFOptimization() : LibCallOptimization("sprintf",
1396 "Number of 'sprintf' calls simplified") {}
1398 /// @brief Make sure that the "fprintf" function has the right prototype
1399 virtual bool ValidateCalledFunction(const Function *f, SimplifyLibCalls &SLC){
1400 // Just make sure this has at least 2 arguments
1401 return (f->getReturnType() == Type::IntTy && f->arg_size() >= 2);
1404 /// @brief Perform the sprintf optimization.
1405 virtual bool OptimizeCall(CallInst *ci, SimplifyLibCalls &SLC) {
1406 // If the call has more than 3 operands, we can't optimize it
1407 if (ci->getNumOperands() > 4 || ci->getNumOperands() < 3)
1410 // All the optimizations depend on the length of the second argument and the
1411 // fact that it is a constant string array. Check that now
1413 ConstantArray* CA = 0;
1414 if (!getConstantStringLength(ci->getOperand(2), len, &CA))
1417 if (ci->getNumOperands() == 3) {
1419 // If the length is 0, we just need to store a null byte
1420 new StoreInst(ConstantInt::get(Type::SByteTy,0),ci->getOperand(1),ci);
1421 ci->replaceAllUsesWith(ConstantSInt::get(Type::IntTy,0));
1422 ci->eraseFromParent();
1426 // Make sure there's no % in the constant array
1427 for (unsigned i = 0; i < len; ++i) {
1428 if (ConstantInt* CI = dyn_cast<ConstantInt>(CA->getOperand(i))) {
1429 // Check for the null terminator
1430 if (CI->getRawValue() == '%')
1431 return false; // we found a %, can't optimize
1433 return false; // initializer is not constant int, can't optimize
1437 // Increment length because we want to copy the null byte too
1440 // sprintf(str,fmt) -> llvm.memcpy(str,fmt,strlen(fmt),1)
1441 Function* memcpy_func = SLC.get_memcpy();
1444 std::vector<Value*> args;
1445 args.push_back(ci->getOperand(1));
1446 args.push_back(ci->getOperand(2));
1447 args.push_back(ConstantUInt::get(SLC.getIntPtrType(),len));
1448 args.push_back(ConstantUInt::get(Type::UIntTy,1));
1449 new CallInst(memcpy_func,args,"",ci);
1450 ci->replaceAllUsesWith(ConstantSInt::get(Type::IntTy,len));
1451 ci->eraseFromParent();
1455 // The remaining optimizations require the format string to be length 2
1460 // The first character has to be a %
1461 if (ConstantInt* CI = dyn_cast<ConstantInt>(CA->getOperand(0)))
1462 if (CI->getRawValue() != '%')
1465 // Get the second character and switch on its value
1466 ConstantInt* CI = dyn_cast<ConstantInt>(CA->getOperand(1));
1467 switch (CI->getRawValue()) {
1469 // sprintf(dest,"%s",str) -> llvm.memcpy(dest, str, strlen(str)+1, 1)
1470 Function* strlen_func = SLC.get_strlen();
1471 Function* memcpy_func = SLC.get_memcpy();
1472 if (!strlen_func || !memcpy_func)
1475 Value *Len = new CallInst(strlen_func, CastToCStr(ci->getOperand(3), *ci),
1476 ci->getOperand(3)->getName()+".len", ci);
1477 Value *Len1 = BinaryOperator::createAdd(Len,
1478 ConstantInt::get(Len->getType(), 1),
1479 Len->getName()+"1", ci);
1480 if (Len1->getType() != SLC.getIntPtrType())
1481 Len1 = new CastInst(Len1, SLC.getIntPtrType(), Len1->getName(), ci);
1482 std::vector<Value*> args;
1483 args.push_back(CastToCStr(ci->getOperand(1), *ci));
1484 args.push_back(CastToCStr(ci->getOperand(3), *ci));
1485 args.push_back(Len1);
1486 args.push_back(ConstantUInt::get(Type::UIntTy,1));
1487 new CallInst(memcpy_func, args, "", ci);
1489 // The strlen result is the unincremented number of bytes in the string.
1490 if (!ci->use_empty()) {
1491 if (Len->getType() != ci->getType())
1492 Len = new CastInst(Len, ci->getType(), Len->getName(), ci);
1493 ci->replaceAllUsesWith(Len);
1495 ci->eraseFromParent();
1499 // sprintf(dest,"%c",chr) -> store chr, dest
1500 CastInst* cast = new CastInst(ci->getOperand(3),Type::SByteTy,"char",ci);
1501 new StoreInst(cast, ci->getOperand(1), ci);
1502 GetElementPtrInst* gep = new GetElementPtrInst(ci->getOperand(1),
1503 ConstantUInt::get(Type::UIntTy,1),ci->getOperand(1)->getName()+".end",
1505 new StoreInst(ConstantInt::get(Type::SByteTy,0),gep,ci);
1506 ci->replaceAllUsesWith(ConstantSInt::get(Type::IntTy,1));
1507 ci->eraseFromParent();
1515 /// This LibCallOptimization will simplify calls to the "fputs" library
1516 /// function. It looks for cases where the result of fputs is not used and the
1517 /// operation can be reduced to something simpler.
1518 /// @brief Simplify the pow library function.
1519 struct PutsOptimization : public LibCallOptimization {
1521 /// @brief Default Constructor
1522 PutsOptimization() : LibCallOptimization("fputs",
1523 "Number of 'fputs' calls simplified") {}
1525 /// @brief Make sure that the "fputs" function has the right prototype
1526 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
1527 // Just make sure this has 2 arguments
1528 return F->arg_size() == 2;
1531 /// @brief Perform the fputs optimization.
1532 virtual bool OptimizeCall(CallInst* ci, SimplifyLibCalls& SLC) {
1533 // If the result is used, none of these optimizations work
1534 if (!ci->use_empty())
1537 // All the optimizations depend on the length of the first argument and the
1538 // fact that it is a constant string array. Check that now
1540 if (!getConstantStringLength(ci->getOperand(1), len))
1545 // fputs("",F) -> noop
1549 // fputs(s,F) -> fputc(s[0],F) (if s is constant and strlen(s) == 1)
1550 const Type* FILEptr_type = ci->getOperand(2)->getType();
1551 Function* fputc_func = SLC.get_fputc(FILEptr_type);
1554 LoadInst* loadi = new LoadInst(ci->getOperand(1),
1555 ci->getOperand(1)->getName()+".byte",ci);
1556 CastInst* casti = new CastInst(loadi,Type::IntTy,
1557 loadi->getName()+".int",ci);
1558 new CallInst(fputc_func,casti,ci->getOperand(2),"",ci);
1563 // fputs(s,F) -> fwrite(s,1,len,F) (if s is constant and strlen(s) > 1)
1564 const Type* FILEptr_type = ci->getOperand(2)->getType();
1565 Function* fwrite_func = SLC.get_fwrite(FILEptr_type);
1568 std::vector<Value*> parms;
1569 parms.push_back(ci->getOperand(1));
1570 parms.push_back(ConstantUInt::get(SLC.getIntPtrType(),len));
1571 parms.push_back(ConstantUInt::get(SLC.getIntPtrType(),1));
1572 parms.push_back(ci->getOperand(2));
1573 new CallInst(fwrite_func,parms,"",ci);
1577 ci->eraseFromParent();
1578 return true; // success
1582 /// This LibCallOptimization will simplify calls to the "isdigit" library
1583 /// function. It simply does range checks the parameter explicitly.
1584 /// @brief Simplify the isdigit library function.
1585 struct isdigitOptimization : public LibCallOptimization {
1587 isdigitOptimization() : LibCallOptimization("isdigit",
1588 "Number of 'isdigit' calls simplified") {}
1590 /// @brief Make sure that the "isdigit" function has the right prototype
1591 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC){
1592 // Just make sure this has 1 argument
1593 return (f->arg_size() == 1);
1596 /// @brief Perform the toascii optimization.
1597 virtual bool OptimizeCall(CallInst *ci, SimplifyLibCalls &SLC) {
1598 if (ConstantInt* CI = dyn_cast<ConstantInt>(ci->getOperand(1))) {
1599 // isdigit(c) -> 0 or 1, if 'c' is constant
1600 uint64_t val = CI->getRawValue();
1601 if (val >= '0' && val <='9')
1602 ci->replaceAllUsesWith(ConstantSInt::get(Type::IntTy,1));
1604 ci->replaceAllUsesWith(ConstantSInt::get(Type::IntTy,0));
1605 ci->eraseFromParent();
1609 // isdigit(c) -> (unsigned)c - '0' <= 9
1611 new CastInst(ci->getOperand(1),Type::UIntTy,
1612 ci->getOperand(1)->getName()+".uint",ci);
1613 BinaryOperator* sub_inst = BinaryOperator::createSub(cast,
1614 ConstantUInt::get(Type::UIntTy,0x30),
1615 ci->getOperand(1)->getName()+".sub",ci);
1616 SetCondInst* setcond_inst = new SetCondInst(Instruction::SetLE,sub_inst,
1617 ConstantUInt::get(Type::UIntTy,9),
1618 ci->getOperand(1)->getName()+".cmp",ci);
1620 new CastInst(setcond_inst,Type::IntTy,
1621 ci->getOperand(1)->getName()+".isdigit",ci);
1622 ci->replaceAllUsesWith(c2);
1623 ci->eraseFromParent();
1628 struct isasciiOptimization : public LibCallOptimization {
1630 isasciiOptimization()
1631 : LibCallOptimization("isascii", "Number of 'isascii' calls simplified") {}
1633 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
1634 return F->arg_size() == 1 && F->arg_begin()->getType()->isInteger() &&
1635 F->getReturnType()->isInteger();
1638 /// @brief Perform the isascii optimization.
1639 virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
1640 // isascii(c) -> (unsigned)c < 128
1641 Value *V = CI->getOperand(1);
1642 if (V->getType()->isSigned())
1643 V = new CastInst(V, V->getType()->getUnsignedVersion(), V->getName(), CI);
1644 Value *Cmp = BinaryOperator::createSetLT(V, ConstantUInt::get(V->getType(),
1646 V->getName()+".isascii", CI);
1647 if (Cmp->getType() != CI->getType())
1648 Cmp = new CastInst(Cmp, CI->getType(), Cmp->getName(), CI);
1649 CI->replaceAllUsesWith(Cmp);
1650 CI->eraseFromParent();
1656 /// This LibCallOptimization will simplify calls to the "toascii" library
1657 /// function. It simply does the corresponding and operation to restrict the
1658 /// range of values to the ASCII character set (0-127).
1659 /// @brief Simplify the toascii library function.
1660 struct ToAsciiOptimization : public LibCallOptimization {
1662 /// @brief Default Constructor
1663 ToAsciiOptimization() : LibCallOptimization("toascii",
1664 "Number of 'toascii' calls simplified") {}
1666 /// @brief Make sure that the "fputs" function has the right prototype
1667 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC){
1668 // Just make sure this has 2 arguments
1669 return (f->arg_size() == 1);
1672 /// @brief Perform the toascii optimization.
1673 virtual bool OptimizeCall(CallInst *ci, SimplifyLibCalls &SLC) {
1674 // toascii(c) -> (c & 0x7f)
1675 Value* chr = ci->getOperand(1);
1676 BinaryOperator* and_inst = BinaryOperator::createAnd(chr,
1677 ConstantInt::get(chr->getType(),0x7F),ci->getName()+".toascii",ci);
1678 ci->replaceAllUsesWith(and_inst);
1679 ci->eraseFromParent();
1684 /// This LibCallOptimization will simplify calls to the "ffs" library
1685 /// calls which find the first set bit in an int, long, or long long. The
1686 /// optimization is to compute the result at compile time if the argument is
1688 /// @brief Simplify the ffs library function.
1689 struct FFSOptimization : public LibCallOptimization {
1691 /// @brief Subclass Constructor
1692 FFSOptimization(const char* funcName, const char* description)
1693 : LibCallOptimization(funcName, description) {}
1696 /// @brief Default Constructor
1697 FFSOptimization() : LibCallOptimization("ffs",
1698 "Number of 'ffs' calls simplified") {}
1700 /// @brief Make sure that the "ffs" function has the right prototype
1701 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
1702 // Just make sure this has 2 arguments
1703 return F->arg_size() == 1 && F->getReturnType() == Type::IntTy;
1706 /// @brief Perform the ffs optimization.
1707 virtual bool OptimizeCall(CallInst *TheCall, SimplifyLibCalls &SLC) {
1708 if (ConstantInt *CI = dyn_cast<ConstantInt>(TheCall->getOperand(1))) {
1709 // ffs(cnst) -> bit#
1710 // ffsl(cnst) -> bit#
1711 // ffsll(cnst) -> bit#
1712 uint64_t val = CI->getRawValue();
1716 while ((val & 1) == 0) {
1721 TheCall->replaceAllUsesWith(ConstantSInt::get(Type::IntTy, result));
1722 TheCall->eraseFromParent();
1726 // ffs(x) -> x == 0 ? 0 : llvm.cttz(x)+1
1727 // ffsl(x) -> x == 0 ? 0 : llvm.cttz(x)+1
1728 // ffsll(x) -> x == 0 ? 0 : llvm.cttz(x)+1
1729 const Type *ArgType = TheCall->getOperand(1)->getType();
1730 ArgType = ArgType->getUnsignedVersion();
1731 const char *CTTZName;
1732 switch (ArgType->getTypeID()) {
1733 default: assert(0 && "Unknown unsigned type!");
1734 case Type::UByteTyID : CTTZName = "llvm.cttz.i8" ; break;
1735 case Type::UShortTyID: CTTZName = "llvm.cttz.i16"; break;
1736 case Type::UIntTyID : CTTZName = "llvm.cttz.i32"; break;
1737 case Type::ULongTyID : CTTZName = "llvm.cttz.i64"; break;
1740 Function *F = SLC.getModule()->getOrInsertFunction(CTTZName, ArgType,
1742 Value *V = new CastInst(TheCall->getOperand(1), ArgType, "tmp", TheCall);
1743 Value *V2 = new CallInst(F, V, "tmp", TheCall);
1744 V2 = new CastInst(V2, Type::IntTy, "tmp", TheCall);
1745 V2 = BinaryOperator::createAdd(V2, ConstantSInt::get(Type::IntTy, 1),
1748 BinaryOperator::createSetEQ(V, Constant::getNullValue(V->getType()),
1750 V2 = new SelectInst(Cond, ConstantInt::get(Type::IntTy, 0), V2,
1751 TheCall->getName(), TheCall);
1752 TheCall->replaceAllUsesWith(V2);
1753 TheCall->eraseFromParent();
1758 /// This LibCallOptimization will simplify calls to the "ffsl" library
1759 /// calls. It simply uses FFSOptimization for which the transformation is
1761 /// @brief Simplify the ffsl library function.
1762 struct FFSLOptimization : public FFSOptimization {
1764 /// @brief Default Constructor
1765 FFSLOptimization() : FFSOptimization("ffsl",
1766 "Number of 'ffsl' calls simplified") {}
1770 /// This LibCallOptimization will simplify calls to the "ffsll" library
1771 /// calls. It simply uses FFSOptimization for which the transformation is
1773 /// @brief Simplify the ffsl library function.
1774 struct FFSLLOptimization : public FFSOptimization {
1776 /// @brief Default Constructor
1777 FFSLLOptimization() : FFSOptimization("ffsll",
1778 "Number of 'ffsll' calls simplified") {}
1782 /// This optimizes unary functions that take and return doubles.
1783 struct UnaryDoubleFPOptimizer : public LibCallOptimization {
1784 UnaryDoubleFPOptimizer(const char *Fn, const char *Desc)
1785 : LibCallOptimization(Fn, Desc) {}
1787 // Make sure that this function has the right prototype
1788 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
1789 return F->arg_size() == 1 && F->arg_begin()->getType() == Type::DoubleTy &&
1790 F->getReturnType() == Type::DoubleTy;
1793 /// ShrinkFunctionToFloatVersion - If the input to this function is really a
1794 /// float, strength reduce this to a float version of the function,
1795 /// e.g. floor((double)FLT) -> (double)floorf(FLT). This can only be called
1796 /// when the target supports the destination function and where there can be
1797 /// no precision loss.
1798 static bool ShrinkFunctionToFloatVersion(CallInst *CI, SimplifyLibCalls &SLC,
1799 Function *(SimplifyLibCalls::*FP)()){
1800 if (CastInst *Cast = dyn_cast<CastInst>(CI->getOperand(1)))
1801 if (Cast->getOperand(0)->getType() == Type::FloatTy) {
1802 Value *New = new CallInst((SLC.*FP)(), Cast->getOperand(0),
1804 New = new CastInst(New, Type::DoubleTy, CI->getName(), CI);
1805 CI->replaceAllUsesWith(New);
1806 CI->eraseFromParent();
1807 if (Cast->use_empty())
1808 Cast->eraseFromParent();
1816 struct FloorOptimization : public UnaryDoubleFPOptimizer {
1818 : UnaryDoubleFPOptimizer("floor", "Number of 'floor' calls simplified") {}
1820 virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
1822 // If this is a float argument passed in, convert to floorf.
1823 if (ShrinkFunctionToFloatVersion(CI, SLC, &SimplifyLibCalls::get_floorf))
1826 return false; // opt failed
1830 struct CeilOptimization : public UnaryDoubleFPOptimizer {
1832 : UnaryDoubleFPOptimizer("ceil", "Number of 'ceil' calls simplified") {}
1834 virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
1836 // If this is a float argument passed in, convert to ceilf.
1837 if (ShrinkFunctionToFloatVersion(CI, SLC, &SimplifyLibCalls::get_ceilf))
1840 return false; // opt failed
1844 struct RoundOptimization : public UnaryDoubleFPOptimizer {
1846 : UnaryDoubleFPOptimizer("round", "Number of 'round' calls simplified") {}
1848 virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
1850 // If this is a float argument passed in, convert to roundf.
1851 if (ShrinkFunctionToFloatVersion(CI, SLC, &SimplifyLibCalls::get_roundf))
1854 return false; // opt failed
1858 struct RintOptimization : public UnaryDoubleFPOptimizer {
1860 : UnaryDoubleFPOptimizer("rint", "Number of 'rint' calls simplified") {}
1862 virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
1864 // If this is a float argument passed in, convert to rintf.
1865 if (ShrinkFunctionToFloatVersion(CI, SLC, &SimplifyLibCalls::get_rintf))
1868 return false; // opt failed
1872 struct NearByIntOptimization : public UnaryDoubleFPOptimizer {
1873 NearByIntOptimization()
1874 : UnaryDoubleFPOptimizer("nearbyint",
1875 "Number of 'nearbyint' calls simplified") {}
1877 virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
1878 #ifdef HAVE_NEARBYINTF
1879 // If this is a float argument passed in, convert to nearbyintf.
1880 if (ShrinkFunctionToFloatVersion(CI, SLC,&SimplifyLibCalls::get_nearbyintf))
1883 return false; // opt failed
1885 } NearByIntOptimizer;
1887 /// A function to compute the length of a null-terminated constant array of
1888 /// integers. This function can't rely on the size of the constant array
1889 /// because there could be a null terminator in the middle of the array.
1890 /// We also have to bail out if we find a non-integer constant initializer
1891 /// of one of the elements or if there is no null-terminator. The logic
1892 /// below checks each of these conditions and will return true only if all
1893 /// conditions are met. In that case, the \p len parameter is set to the length
1894 /// of the null-terminated string. If false is returned, the conditions were
1895 /// not met and len is set to 0.
1896 /// @brief Get the length of a constant string (null-terminated array).
1897 bool getConstantStringLength(Value *V, uint64_t &len, ConstantArray **CA) {
1898 assert(V != 0 && "Invalid args to getConstantStringLength");
1899 len = 0; // make sure we initialize this
1901 // If the value is not a GEP instruction nor a constant expression with a
1902 // GEP instruction, then return false because ConstantArray can't occur
1904 if (GetElementPtrInst* GEPI = dyn_cast<GetElementPtrInst>(V))
1906 else if (ConstantExpr* CE = dyn_cast<ConstantExpr>(V))
1907 if (CE->getOpcode() == Instruction::GetElementPtr)
1914 // Make sure the GEP has exactly three arguments.
1915 if (GEP->getNumOperands() != 3)
1918 // Check to make sure that the first operand of the GEP is an integer and
1919 // has value 0 so that we are sure we're indexing into the initializer.
1920 if (ConstantInt* op1 = dyn_cast<ConstantInt>(GEP->getOperand(1))) {
1921 if (!op1->isNullValue())
1926 // Ensure that the second operand is a ConstantInt. If it isn't then this
1927 // GEP is wonky and we're not really sure what were referencing into and
1928 // better of not optimizing it. While we're at it, get the second index
1929 // value. We'll need this later for indexing the ConstantArray.
1930 uint64_t start_idx = 0;
1931 if (ConstantInt* CI = dyn_cast<ConstantInt>(GEP->getOperand(2)))
1932 start_idx = CI->getRawValue();
1936 // The GEP instruction, constant or instruction, must reference a global
1937 // variable that is a constant and is initialized. The referenced constant
1938 // initializer is the array that we'll use for optimization.
1939 GlobalVariable* GV = dyn_cast<GlobalVariable>(GEP->getOperand(0));
1940 if (!GV || !GV->isConstant() || !GV->hasInitializer())
1943 // Get the initializer.
1944 Constant* INTLZR = GV->getInitializer();
1946 // Handle the ConstantAggregateZero case
1947 if (ConstantAggregateZero *CAZ = dyn_cast<ConstantAggregateZero>(INTLZR)) {
1948 // This is a degenerate case. The initializer is constant zero so the
1949 // length of the string must be zero.
1954 // Must be a Constant Array
1955 ConstantArray* A = dyn_cast<ConstantArray>(INTLZR);
1959 // Get the number of elements in the array
1960 uint64_t max_elems = A->getType()->getNumElements();
1962 // Traverse the constant array from start_idx (derived above) which is
1963 // the place the GEP refers to in the array.
1964 for (len = start_idx; len < max_elems; len++) {
1965 if (ConstantInt *CI = dyn_cast<ConstantInt>(A->getOperand(len))) {
1966 // Check for the null terminator
1967 if (CI->isNullValue())
1968 break; // we found end of string
1970 return false; // This array isn't suitable, non-int initializer
1973 if (len >= max_elems)
1974 return false; // This array isn't null terminated
1976 // Subtract out the initial value from the length
1980 return true; // success!
1983 /// CastToCStr - Return V if it is an sbyte*, otherwise cast it to sbyte*,
1984 /// inserting the cast before IP, and return the cast.
1985 /// @brief Cast a value to a "C" string.
1986 Value *CastToCStr(Value *V, Instruction &IP) {
1987 const Type *SBPTy = PointerType::get(Type::SByteTy);
1988 if (V->getType() != SBPTy)
1989 return new CastInst(V, SBPTy, V->getName(), &IP);
1994 // Additional cases that we need to add to this file:
1997 // * cbrt(expN(X)) -> expN(x/3)
1998 // * cbrt(sqrt(x)) -> pow(x,1/6)
1999 // * cbrt(sqrt(x)) -> pow(x,1/9)
2002 // * cos(-x) -> cos(x)
2005 // * exp(log(x)) -> x
2008 // * log(exp(x)) -> x
2009 // * log(x**y) -> y*log(x)
2010 // * log(exp(y)) -> y*log(e)
2011 // * log(exp2(y)) -> y*log(2)
2012 // * log(exp10(y)) -> y*log(10)
2013 // * log(sqrt(x)) -> 0.5*log(x)
2014 // * log(pow(x,y)) -> y*log(x)
2016 // lround, lroundf, lroundl:
2017 // * lround(cnst) -> cnst'
2020 // * memcmp(x,y,l) -> cnst
2021 // (if all arguments are constant and strlen(x) <= l and strlen(y) <= l)
2024 // * memmove(d,s,l,a) -> memcpy(d,s,l,a)
2025 // (if s is a global constant array)
2028 // * pow(exp(x),y) -> exp(x*y)
2029 // * pow(sqrt(x),y) -> pow(x,y*0.5)
2030 // * pow(pow(x,y),z)-> pow(x,y*z)
2033 // * puts("") -> fputc("\n",stdout) (how do we get "stdout"?)
2035 // round, roundf, roundl:
2036 // * round(cnst) -> cnst'
2039 // * signbit(cnst) -> cnst'
2040 // * signbit(nncst) -> 0 (if pstv is a non-negative constant)
2042 // sqrt, sqrtf, sqrtl:
2043 // * sqrt(expN(x)) -> expN(x*0.5)
2044 // * sqrt(Nroot(x)) -> pow(x,1/(2*N))
2045 // * sqrt(pow(x,y)) -> pow(|x|,y*0.5)
2048 // * stpcpy(str, "literal") ->
2049 // llvm.memcpy(str,"literal",strlen("literal")+1,1)
2051 // * strrchr(s,c) -> reverse_offset_of_in(c,s)
2052 // (if c is a constant integer and s is a constant string)
2053 // * strrchr(s1,0) -> strchr(s1,0)
2056 // * strncat(x,y,0) -> x
2057 // * strncat(x,y,0) -> x (if strlen(y) = 0)
2058 // * strncat(x,y,l) -> strcat(x,y) (if y and l are constants an l > strlen(y))
2061 // * strncpy(d,s,0) -> d
2062 // * strncpy(d,s,l) -> memcpy(d,s,l,1)
2063 // (if s and l are constants)
2066 // * strpbrk(s,a) -> offset_in_for(s,a)
2067 // (if s and a are both constant strings)
2068 // * strpbrk(s,"") -> 0
2069 // * strpbrk(s,a) -> strchr(s,a[0]) (if a is constant string of length 1)
2072 // * strspn(s,a) -> const_int (if both args are constant)
2073 // * strspn("",a) -> 0
2074 // * strspn(s,"") -> 0
2075 // * strcspn(s,a) -> const_int (if both args are constant)
2076 // * strcspn("",a) -> 0
2077 // * strcspn(s,"") -> strlen(a)
2080 // * strstr(x,x) -> x
2081 // * strstr(s1,s2) -> offset_of_s2_in(s1)
2082 // (if s1 and s2 are constant strings)
2085 // * tan(atan(x)) -> x
2087 // trunc, truncf, truncl:
2088 // * trunc(cnst) -> cnst'