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 fputs libcall
233 Function* get_fputs(const Type* FILEptr_type) {
235 fputs_func = M->getOrInsertFunction("fputs", Type::IntTy,
236 PointerType::get(Type::SByteTy),
241 /// @brief Return a Function* for the fwrite libcall
242 Function* get_fwrite(const Type* FILEptr_type) {
244 fwrite_func = M->getOrInsertFunction("fwrite", TD->getIntPtrType(),
245 PointerType::get(Type::SByteTy),
252 /// @brief Return a Function* for the sqrt libcall
253 Function* get_sqrt() {
255 sqrt_func = M->getOrInsertFunction("sqrt", Type::DoubleTy,
256 Type::DoubleTy, NULL);
260 /// @brief Return a Function* for the strlen libcall
261 Function* get_strcpy() {
263 strcpy_func = M->getOrInsertFunction("strcpy",
264 PointerType::get(Type::SByteTy),
265 PointerType::get(Type::SByteTy),
266 PointerType::get(Type::SByteTy),
271 /// @brief Return a Function* for the strlen libcall
272 Function* get_strlen() {
274 strlen_func = M->getOrInsertFunction("strlen", TD->getIntPtrType(),
275 PointerType::get(Type::SByteTy),
280 /// @brief Return a Function* for the memchr libcall
281 Function* get_memchr() {
283 memchr_func = M->getOrInsertFunction("memchr",
284 PointerType::get(Type::SByteTy),
285 PointerType::get(Type::SByteTy),
286 Type::IntTy, TD->getIntPtrType(),
291 /// @brief Return a Function* for the memcpy libcall
292 Function* get_memcpy() {
294 const Type *SBP = PointerType::get(Type::SByteTy);
295 const char *N = TD->getIntPtrType() == Type::UIntTy ?
296 "llvm.memcpy.i32" : "llvm.memcpy.i64";
297 memcpy_func = M->getOrInsertFunction(N, Type::VoidTy, SBP, SBP,
298 TD->getIntPtrType(), Type::UIntTy,
304 Function *getUnaryFloatFunction(const char *Name, Function *&Cache) {
306 Cache = M->getOrInsertFunction(Name, Type::FloatTy, Type::FloatTy, NULL);
310 Function *get_floorf() { return getUnaryFloatFunction("floorf", floorf_func);}
311 Function *get_ceilf() { return getUnaryFloatFunction( "ceilf", ceilf_func);}
312 Function *get_roundf() { return getUnaryFloatFunction("roundf", roundf_func);}
313 Function *get_rintf() { return getUnaryFloatFunction( "rintf", rintf_func);}
314 Function *get_nearbyintf() { return getUnaryFloatFunction("nearbyintf",
317 /// @brief Reset our cached data for a new Module
318 void reset(Module& mod) {
320 TD = &getAnalysis<TargetData>();
337 /// Caches for function pointers.
338 Function *fputc_func, *fputs_func, *fwrite_func;
339 Function *memcpy_func, *memchr_func;
341 Function *strcpy_func, *strlen_func;
342 Function *floorf_func, *ceilf_func, *roundf_func;
343 Function *rintf_func, *nearbyintf_func;
344 Module *M; ///< Cached Module
345 TargetData *TD; ///< Cached TargetData
349 RegisterOpt<SimplifyLibCalls>
350 X("simplify-libcalls","Simplify well-known library calls");
352 } // anonymous namespace
354 // The only public symbol in this file which just instantiates the pass object
355 ModulePass *llvm::createSimplifyLibCallsPass() {
356 return new SimplifyLibCalls();
359 // Classes below here, in the anonymous namespace, are all subclasses of the
360 // LibCallOptimization class, each implementing all optimizations possible for a
361 // single well-known library call. Each has a static singleton instance that
362 // auto registers it into the "optlist" global above.
365 // Forward declare utility functions.
366 bool getConstantStringLength(Value* V, uint64_t& len, ConstantArray** A = 0 );
367 Value *CastToCStr(Value *V, Instruction &IP);
369 /// This LibCallOptimization will find instances of a call to "exit" that occurs
370 /// within the "main" function and change it to a simple "ret" instruction with
371 /// the same value passed to the exit function. When this is done, it splits the
372 /// basic block at the exit(3) call and deletes the call instruction.
373 /// @brief Replace calls to exit in main with a simple return
374 struct ExitInMainOptimization : public LibCallOptimization {
375 ExitInMainOptimization() : LibCallOptimization("exit",
376 "Number of 'exit' calls simplified") {}
378 // Make sure the called function looks like exit (int argument, int return
379 // type, external linkage, not varargs).
380 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
381 return F->arg_size() >= 1 && F->arg_begin()->getType()->isInteger();
384 virtual bool OptimizeCall(CallInst* ci, SimplifyLibCalls& SLC) {
385 // To be careful, we check that the call to exit is coming from "main", that
386 // main has external linkage, and the return type of main and the argument
387 // to exit have the same type.
388 Function *from = ci->getParent()->getParent();
389 if (from->hasExternalLinkage())
390 if (from->getReturnType() == ci->getOperand(1)->getType())
391 if (from->getName() == "main") {
392 // Okay, time to actually do the optimization. First, get the basic
393 // block of the call instruction
394 BasicBlock* bb = ci->getParent();
396 // Create a return instruction that we'll replace the call with.
397 // Note that the argument of the return is the argument of the call
399 new ReturnInst(ci->getOperand(1), ci);
401 // Split the block at the call instruction which places it in a new
403 bb->splitBasicBlock(ci);
405 // The block split caused a branch instruction to be inserted into
406 // the end of the original block, right after the return instruction
407 // that we put there. That's not a valid block, so delete the branch
409 bb->getInstList().pop_back();
411 // Now we can finally get rid of the call instruction which now lives
412 // in the new basic block.
413 ci->eraseFromParent();
415 // Optimization succeeded, return true.
418 // We didn't pass the criteria for this optimization so return false
421 } ExitInMainOptimizer;
423 /// This LibCallOptimization will simplify a call to the strcat library
424 /// function. The simplification is possible only if the string being
425 /// concatenated is a constant array or a constant expression that results in
426 /// a constant string. In this case we can replace it with strlen + llvm.memcpy
427 /// of the constant string. Both of these calls are further reduced, if possible
428 /// on subsequent passes.
429 /// @brief Simplify the strcat library function.
430 struct StrCatOptimization : public LibCallOptimization {
432 /// @brief Default constructor
433 StrCatOptimization() : LibCallOptimization("strcat",
434 "Number of 'strcat' calls simplified") {}
438 /// @brief Make sure that the "strcat" function has the right prototype
439 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC){
440 if (f->getReturnType() == PointerType::get(Type::SByteTy))
441 if (f->arg_size() == 2)
443 Function::const_arg_iterator AI = f->arg_begin();
444 if (AI++->getType() == PointerType::get(Type::SByteTy))
445 if (AI->getType() == PointerType::get(Type::SByteTy))
447 // Indicate this is a suitable call type.
454 /// @brief Optimize the strcat library function
455 virtual bool OptimizeCall(CallInst* ci, SimplifyLibCalls& SLC) {
456 // Extract some information from the instruction
457 Value* dest = ci->getOperand(1);
458 Value* src = ci->getOperand(2);
460 // Extract the initializer (while making numerous checks) from the
461 // source operand of the call to strcat. If we get null back, one of
462 // a variety of checks in get_GVInitializer failed
464 if (!getConstantStringLength(src,len))
467 // Handle the simple, do-nothing case
469 ci->replaceAllUsesWith(dest);
470 ci->eraseFromParent();
474 // Increment the length because we actually want to memcpy the null
475 // terminator as well.
478 // We need to find the end of the destination string. That's where the
479 // memory is to be moved to. We just generate a call to strlen (further
480 // optimized in another pass). Note that the SLC.get_strlen() call
481 // caches the Function* for us.
482 CallInst* strlen_inst =
483 new CallInst(SLC.get_strlen(), dest, dest->getName()+".len",ci);
485 // Now that we have the destination's length, we must index into the
486 // destination's pointer to get the actual memcpy destination (end of
487 // the string .. we're concatenating).
488 std::vector<Value*> idx;
489 idx.push_back(strlen_inst);
490 GetElementPtrInst* gep =
491 new GetElementPtrInst(dest,idx,dest->getName()+".indexed",ci);
493 // We have enough information to now generate the memcpy call to
494 // do the concatenation for us.
495 std::vector<Value*> vals;
496 vals.push_back(gep); // destination
497 vals.push_back(ci->getOperand(2)); // source
498 vals.push_back(ConstantUInt::get(SLC.getIntPtrType(),len)); // length
499 vals.push_back(ConstantUInt::get(Type::UIntTy,1)); // alignment
500 new CallInst(SLC.get_memcpy(), vals, "", ci);
502 // Finally, substitute the first operand of the strcat call for the
503 // strcat call itself since strcat returns its first operand; and,
504 // kill the strcat CallInst.
505 ci->replaceAllUsesWith(dest);
506 ci->eraseFromParent();
511 /// This LibCallOptimization will simplify a call to the strchr library
512 /// function. It optimizes out cases where the arguments are both constant
513 /// and the result can be determined statically.
514 /// @brief Simplify the strcmp library function.
515 struct StrChrOptimization : public LibCallOptimization {
517 StrChrOptimization() : LibCallOptimization("strchr",
518 "Number of 'strchr' calls simplified") {}
520 /// @brief Make sure that the "strchr" function has the right prototype
521 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC){
522 if (f->getReturnType() == PointerType::get(Type::SByteTy) &&
528 /// @brief Perform the strchr optimizations
529 virtual bool OptimizeCall(CallInst *ci, SimplifyLibCalls &SLC) {
530 // If there aren't three operands, bail
531 if (ci->getNumOperands() != 3)
534 // Check that the first argument to strchr is a constant array of sbyte.
535 // If it is, get the length and data, otherwise return false.
538 if (!getConstantStringLength(ci->getOperand(1),len,&CA))
541 // Check that the second argument to strchr is a constant int, return false
543 ConstantSInt* CSI = dyn_cast<ConstantSInt>(ci->getOperand(2));
545 // Just lower this to memchr since we know the length of the string as
547 Function* f = SLC.get_memchr();
548 std::vector<Value*> args;
549 args.push_back(ci->getOperand(1));
550 args.push_back(ci->getOperand(2));
551 args.push_back(ConstantUInt::get(SLC.getIntPtrType(),len));
552 ci->replaceAllUsesWith( new CallInst(f,args,ci->getName(),ci));
553 ci->eraseFromParent();
557 // Get the character we're looking for
558 int64_t chr = CSI->getValue();
560 // Compute the offset
562 bool char_found = false;
563 for (uint64_t i = 0; i < len; ++i) {
564 if (ConstantSInt* CI = dyn_cast<ConstantSInt>(CA->getOperand(i))) {
565 // Check for the null terminator
566 if (CI->isNullValue())
567 break; // we found end of string
568 else if (CI->getValue() == chr) {
576 // strchr(s,c) -> offset_of_in(c,s)
577 // (if c is a constant integer and s is a constant string)
579 std::vector<Value*> indices;
580 indices.push_back(ConstantUInt::get(Type::ULongTy,offset));
581 GetElementPtrInst* GEP = new GetElementPtrInst(ci->getOperand(1),indices,
582 ci->getOperand(1)->getName()+".strchr",ci);
583 ci->replaceAllUsesWith(GEP);
585 ci->replaceAllUsesWith(
586 ConstantPointerNull::get(PointerType::get(Type::SByteTy)));
588 ci->eraseFromParent();
593 /// This LibCallOptimization will simplify a call to the strcmp library
594 /// function. It optimizes out cases where one or both arguments are constant
595 /// and the result can be determined statically.
596 /// @brief Simplify the strcmp library function.
597 struct StrCmpOptimization : public LibCallOptimization {
599 StrCmpOptimization() : LibCallOptimization("strcmp",
600 "Number of 'strcmp' calls simplified") {}
602 /// @brief Make sure that the "strcmp" function has the right prototype
603 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
604 return F->getReturnType() == Type::IntTy && F->arg_size() == 2;
607 /// @brief Perform the strcmp optimization
608 virtual bool OptimizeCall(CallInst* ci, SimplifyLibCalls& SLC) {
609 // First, check to see if src and destination are the same. If they are,
610 // then the optimization is to replace the CallInst with a constant 0
611 // because the call is a no-op.
612 Value* s1 = ci->getOperand(1);
613 Value* s2 = ci->getOperand(2);
616 ci->replaceAllUsesWith(ConstantInt::get(Type::IntTy,0));
617 ci->eraseFromParent();
621 bool isstr_1 = false;
624 if (getConstantStringLength(s1,len_1,&A1)) {
627 // strcmp("",x) -> *x
629 new LoadInst(CastToCStr(s2,*ci), ci->getName()+".load",ci);
631 new CastInst(load,Type::IntTy,ci->getName()+".int",ci);
632 ci->replaceAllUsesWith(cast);
633 ci->eraseFromParent();
638 bool isstr_2 = false;
641 if (getConstantStringLength(s2, len_2, &A2)) {
644 // strcmp(x,"") -> *x
646 new LoadInst(CastToCStr(s1,*ci),ci->getName()+".val",ci);
648 new CastInst(load,Type::IntTy,ci->getName()+".int",ci);
649 ci->replaceAllUsesWith(cast);
650 ci->eraseFromParent();
655 if (isstr_1 && isstr_2) {
656 // strcmp(x,y) -> cnst (if both x and y are constant strings)
657 std::string str1 = A1->getAsString();
658 std::string str2 = A2->getAsString();
659 int result = strcmp(str1.c_str(), str2.c_str());
660 ci->replaceAllUsesWith(ConstantSInt::get(Type::IntTy,result));
661 ci->eraseFromParent();
668 /// This LibCallOptimization will simplify a call to the strncmp library
669 /// function. It optimizes out cases where one or both arguments are constant
670 /// and the result can be determined statically.
671 /// @brief Simplify the strncmp library function.
672 struct StrNCmpOptimization : public LibCallOptimization {
674 StrNCmpOptimization() : LibCallOptimization("strncmp",
675 "Number of 'strncmp' calls simplified") {}
677 /// @brief Make sure that the "strncmp" function has the right prototype
678 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC){
679 if (f->getReturnType() == Type::IntTy && f->arg_size() == 3)
684 /// @brief Perform the strncpy optimization
685 virtual bool OptimizeCall(CallInst *ci, SimplifyLibCalls &SLC) {
686 // First, check to see if src and destination are the same. If they are,
687 // then the optimization is to replace the CallInst with a constant 0
688 // because the call is a no-op.
689 Value* s1 = ci->getOperand(1);
690 Value* s2 = ci->getOperand(2);
692 // strncmp(x,x,l) -> 0
693 ci->replaceAllUsesWith(ConstantInt::get(Type::IntTy,0));
694 ci->eraseFromParent();
698 // Check the length argument, if it is Constant zero then the strings are
700 uint64_t len_arg = 0;
701 bool len_arg_is_const = false;
702 if (ConstantInt* len_CI = dyn_cast<ConstantInt>(ci->getOperand(3))) {
703 len_arg_is_const = true;
704 len_arg = len_CI->getRawValue();
706 // strncmp(x,y,0) -> 0
707 ci->replaceAllUsesWith(ConstantInt::get(Type::IntTy,0));
708 ci->eraseFromParent();
713 bool isstr_1 = false;
716 if (getConstantStringLength(s1, len_1, &A1)) {
719 // strncmp("",x) -> *x
720 LoadInst* load = new LoadInst(s1,ci->getName()+".load",ci);
722 new CastInst(load,Type::IntTy,ci->getName()+".int",ci);
723 ci->replaceAllUsesWith(cast);
724 ci->eraseFromParent();
729 bool isstr_2 = false;
732 if (getConstantStringLength(s2,len_2,&A2)) {
735 // strncmp(x,"") -> *x
736 LoadInst* load = new LoadInst(s2,ci->getName()+".val",ci);
738 new CastInst(load,Type::IntTy,ci->getName()+".int",ci);
739 ci->replaceAllUsesWith(cast);
740 ci->eraseFromParent();
745 if (isstr_1 && isstr_2 && len_arg_is_const) {
746 // strncmp(x,y,const) -> constant
747 std::string str1 = A1->getAsString();
748 std::string str2 = A2->getAsString();
749 int result = strncmp(str1.c_str(), str2.c_str(), len_arg);
750 ci->replaceAllUsesWith(ConstantSInt::get(Type::IntTy,result));
751 ci->eraseFromParent();
758 /// This LibCallOptimization will simplify a call to the strcpy library
759 /// function. Two optimizations are possible:
760 /// (1) If src and dest are the same and not volatile, just return dest
761 /// (2) If the src is a constant then we can convert to llvm.memmove
762 /// @brief Simplify the strcpy library function.
763 struct StrCpyOptimization : public LibCallOptimization {
765 StrCpyOptimization() : LibCallOptimization("strcpy",
766 "Number of 'strcpy' calls simplified") {}
768 /// @brief Make sure that the "strcpy" function has the right prototype
769 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC){
770 if (f->getReturnType() == PointerType::get(Type::SByteTy))
771 if (f->arg_size() == 2) {
772 Function::const_arg_iterator AI = f->arg_begin();
773 if (AI++->getType() == PointerType::get(Type::SByteTy))
774 if (AI->getType() == PointerType::get(Type::SByteTy)) {
775 // Indicate this is a suitable call type.
782 /// @brief Perform the strcpy optimization
783 virtual bool OptimizeCall(CallInst* ci, SimplifyLibCalls& SLC) {
784 // First, check to see if src and destination are the same. If they are,
785 // then the optimization is to replace the CallInst with the destination
786 // because the call is a no-op. Note that this corresponds to the
787 // degenerate strcpy(X,X) case which should have "undefined" results
788 // according to the C specification. However, it occurs sometimes and
789 // we optimize it as a no-op.
790 Value* dest = ci->getOperand(1);
791 Value* src = ci->getOperand(2);
793 ci->replaceAllUsesWith(dest);
794 ci->eraseFromParent();
798 // Get the length of the constant string referenced by the second operand,
799 // the "src" parameter. Fail the optimization if we can't get the length
800 // (note that getConstantStringLength does lots of checks to make sure this
803 if (!getConstantStringLength(ci->getOperand(2),len))
806 // If the constant string's length is zero we can optimize this by just
807 // doing a store of 0 at the first byte of the destination
809 new StoreInst(ConstantInt::get(Type::SByteTy,0),ci->getOperand(1),ci);
810 ci->replaceAllUsesWith(dest);
811 ci->eraseFromParent();
815 // Increment the length because we actually want to memcpy the null
816 // terminator as well.
819 // We have enough information to now generate the memcpy call to
820 // do the concatenation for us.
821 std::vector<Value*> vals;
822 vals.push_back(dest); // destination
823 vals.push_back(src); // source
824 vals.push_back(ConstantUInt::get(SLC.getIntPtrType(),len)); // length
825 vals.push_back(ConstantUInt::get(Type::UIntTy,1)); // alignment
826 new CallInst(SLC.get_memcpy(), vals, "", ci);
828 // Finally, substitute the first operand of the strcat call for the
829 // strcat call itself since strcat returns its first operand; and,
830 // kill the strcat CallInst.
831 ci->replaceAllUsesWith(dest);
832 ci->eraseFromParent();
837 /// This LibCallOptimization will simplify a call to the strlen library
838 /// function by replacing it with a constant value if the string provided to
839 /// it is a constant array.
840 /// @brief Simplify the strlen library function.
841 struct StrLenOptimization : public LibCallOptimization {
842 StrLenOptimization() : LibCallOptimization("strlen",
843 "Number of 'strlen' calls simplified") {}
845 /// @brief Make sure that the "strlen" function has the right prototype
846 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC)
848 if (f->getReturnType() == SLC.getTargetData()->getIntPtrType())
849 if (f->arg_size() == 1)
850 if (Function::const_arg_iterator AI = f->arg_begin())
851 if (AI->getType() == PointerType::get(Type::SByteTy))
856 /// @brief Perform the strlen optimization
857 virtual bool OptimizeCall(CallInst* ci, SimplifyLibCalls& SLC)
859 // Make sure we're dealing with an sbyte* here.
860 Value* str = ci->getOperand(1);
861 if (str->getType() != PointerType::get(Type::SByteTy))
864 // Does the call to strlen have exactly one use?
866 // Is that single use a binary operator?
867 if (BinaryOperator* bop = dyn_cast<BinaryOperator>(ci->use_back()))
868 // Is it compared against a constant integer?
869 if (ConstantInt* CI = dyn_cast<ConstantInt>(bop->getOperand(1)))
871 // Get the value the strlen result is compared to
872 uint64_t val = CI->getRawValue();
874 // If its compared against length 0 with == or !=
876 (bop->getOpcode() == Instruction::SetEQ ||
877 bop->getOpcode() == Instruction::SetNE))
879 // strlen(x) != 0 -> *x != 0
880 // strlen(x) == 0 -> *x == 0
881 LoadInst* load = new LoadInst(str,str->getName()+".first",ci);
882 BinaryOperator* rbop = BinaryOperator::create(bop->getOpcode(),
883 load, ConstantSInt::get(Type::SByteTy,0),
884 bop->getName()+".strlen", ci);
885 bop->replaceAllUsesWith(rbop);
886 bop->eraseFromParent();
887 ci->eraseFromParent();
892 // Get the length of the constant string operand
894 if (!getConstantStringLength(ci->getOperand(1),len))
897 // strlen("xyz") -> 3 (for example)
898 const Type *Ty = SLC.getTargetData()->getIntPtrType();
900 ci->replaceAllUsesWith(ConstantSInt::get(Ty, len));
902 ci->replaceAllUsesWith(ConstantUInt::get(Ty, len));
904 ci->eraseFromParent();
909 /// IsOnlyUsedInEqualsComparison - Return true if it only matters that the value
910 /// is equal or not-equal to zero.
911 static bool IsOnlyUsedInEqualsZeroComparison(Instruction *I) {
912 for (Value::use_iterator UI = I->use_begin(), E = I->use_end();
914 Instruction *User = cast<Instruction>(*UI);
915 if (User->getOpcode() == Instruction::SetNE ||
916 User->getOpcode() == Instruction::SetEQ) {
917 if (isa<Constant>(User->getOperand(1)) &&
918 cast<Constant>(User->getOperand(1))->isNullValue())
920 } else if (CastInst *CI = dyn_cast<CastInst>(User))
921 if (CI->getType() == Type::BoolTy)
923 // Unknown instruction.
929 /// This memcmpOptimization will simplify a call to the memcmp library
931 struct memcmpOptimization : public LibCallOptimization {
932 /// @brief Default Constructor
934 : LibCallOptimization("memcmp", "Number of 'memcmp' calls simplified") {}
936 /// @brief Make sure that the "memcmp" function has the right prototype
937 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &TD) {
938 Function::const_arg_iterator AI = F->arg_begin();
939 if (F->arg_size() != 3 || !isa<PointerType>(AI->getType())) return false;
940 if (!isa<PointerType>((++AI)->getType())) return false;
941 if (!(++AI)->getType()->isInteger()) return false;
942 if (!F->getReturnType()->isInteger()) return false;
946 /// Because of alignment and instruction information that we don't have, we
947 /// leave the bulk of this to the code generators.
949 /// Note that we could do much more if we could force alignment on otherwise
950 /// small aligned allocas, or if we could indicate that loads have a small
952 virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &TD) {
953 Value *LHS = CI->getOperand(1), *RHS = CI->getOperand(2);
955 // If the two operands are the same, return zero.
957 // memcmp(s,s,x) -> 0
958 CI->replaceAllUsesWith(Constant::getNullValue(CI->getType()));
959 CI->eraseFromParent();
963 // Make sure we have a constant length.
964 ConstantInt *LenC = dyn_cast<ConstantInt>(CI->getOperand(3));
965 if (!LenC) return false;
966 uint64_t Len = LenC->getRawValue();
968 // If the length is zero, this returns 0.
971 // memcmp(s1,s2,0) -> 0
972 CI->replaceAllUsesWith(Constant::getNullValue(CI->getType()));
973 CI->eraseFromParent();
976 // memcmp(S1,S2,1) -> *(ubyte*)S1 - *(ubyte*)S2
977 const Type *UCharPtr = PointerType::get(Type::UByteTy);
978 CastInst *Op1Cast = new CastInst(LHS, UCharPtr, LHS->getName(), CI);
979 CastInst *Op2Cast = new CastInst(RHS, UCharPtr, RHS->getName(), CI);
980 Value *S1V = new LoadInst(Op1Cast, LHS->getName()+".val", CI);
981 Value *S2V = new LoadInst(Op2Cast, RHS->getName()+".val", CI);
982 Value *RV = BinaryOperator::createSub(S1V, S2V, CI->getName()+".diff",CI);
983 if (RV->getType() != CI->getType())
984 RV = new CastInst(RV, CI->getType(), RV->getName(), CI);
985 CI->replaceAllUsesWith(RV);
986 CI->eraseFromParent();
990 if (IsOnlyUsedInEqualsZeroComparison(CI)) {
991 // TODO: IF both are aligned, use a short load/compare.
993 // memcmp(S1,S2,2) -> S1[0]-S2[0] | S1[1]-S2[1] iff only ==/!= 0 matters
994 const Type *UCharPtr = PointerType::get(Type::UByteTy);
995 CastInst *Op1Cast = new CastInst(LHS, UCharPtr, LHS->getName(), CI);
996 CastInst *Op2Cast = new CastInst(RHS, UCharPtr, RHS->getName(), CI);
997 Value *S1V1 = new LoadInst(Op1Cast, LHS->getName()+".val1", CI);
998 Value *S2V1 = new LoadInst(Op2Cast, RHS->getName()+".val1", CI);
999 Value *D1 = BinaryOperator::createSub(S1V1, S2V1,
1000 CI->getName()+".d1", CI);
1001 Constant *One = ConstantInt::get(Type::IntTy, 1);
1002 Value *G1 = new GetElementPtrInst(Op1Cast, One, "next1v", CI);
1003 Value *G2 = new GetElementPtrInst(Op2Cast, One, "next2v", CI);
1004 Value *S1V2 = new LoadInst(G1, LHS->getName()+".val2", CI);
1005 Value *S2V2 = new LoadInst(G2, RHS->getName()+".val2", CI);
1006 Value *D2 = BinaryOperator::createSub(S1V2, S2V2,
1007 CI->getName()+".d1", CI);
1008 Value *Or = BinaryOperator::createOr(D1, D2, CI->getName()+".res", CI);
1009 if (Or->getType() != CI->getType())
1010 Or = new CastInst(Or, CI->getType(), Or->getName(), CI);
1011 CI->replaceAllUsesWith(Or);
1012 CI->eraseFromParent();
1025 /// This LibCallOptimization will simplify a call to the memcpy library
1026 /// function by expanding it out to a single store of size 0, 1, 2, 4, or 8
1027 /// bytes depending on the length of the string and the alignment. Additional
1028 /// optimizations are possible in code generation (sequence of immediate store)
1029 /// @brief Simplify the memcpy library function.
1030 struct LLVMMemCpyMoveOptzn : public LibCallOptimization {
1031 LLVMMemCpyMoveOptzn(const char* fname, const char* desc)
1032 : LibCallOptimization(fname, desc) {}
1034 /// @brief Make sure that the "memcpy" function has the right prototype
1035 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& TD) {
1036 // Just make sure this has 4 arguments per LLVM spec.
1037 return (f->arg_size() == 4);
1040 /// Because of alignment and instruction information that we don't have, we
1041 /// leave the bulk of this to the code generators. The optimization here just
1042 /// deals with a few degenerate cases where the length of the string and the
1043 /// alignment match the sizes of our intrinsic types so we can do a load and
1044 /// store instead of the memcpy call.
1045 /// @brief Perform the memcpy optimization.
1046 virtual bool OptimizeCall(CallInst* ci, SimplifyLibCalls& TD) {
1047 // Make sure we have constant int values to work with
1048 ConstantInt* LEN = dyn_cast<ConstantInt>(ci->getOperand(3));
1051 ConstantInt* ALIGN = dyn_cast<ConstantInt>(ci->getOperand(4));
1055 // If the length is larger than the alignment, we can't optimize
1056 uint64_t len = LEN->getRawValue();
1057 uint64_t alignment = ALIGN->getRawValue();
1059 alignment = 1; // Alignment 0 is identity for alignment 1
1060 if (len > alignment)
1063 // Get the type we will cast to, based on size of the string
1064 Value* dest = ci->getOperand(1);
1065 Value* src = ci->getOperand(2);
1070 // memcpy(d,s,0,a) -> noop
1071 ci->eraseFromParent();
1073 case 1: castType = Type::SByteTy; break;
1074 case 2: castType = Type::ShortTy; break;
1075 case 4: castType = Type::IntTy; break;
1076 case 8: castType = Type::LongTy; break;
1081 // Cast source and dest to the right sized primitive and then load/store
1083 new CastInst(src,PointerType::get(castType),src->getName()+".cast",ci);
1084 CastInst* DestCast =
1085 new CastInst(dest,PointerType::get(castType),dest->getName()+".cast",ci);
1086 LoadInst* LI = new LoadInst(SrcCast,SrcCast->getName()+".val",ci);
1087 StoreInst* SI = new StoreInst(LI, DestCast, ci);
1088 ci->eraseFromParent();
1093 /// This LibCallOptimization will simplify a call to the memcpy/memmove library
1095 LLVMMemCpyMoveOptzn LLVMMemCpyOptimizer32("llvm.memcpy.i32",
1096 "Number of 'llvm.memcpy' calls simplified");
1097 LLVMMemCpyMoveOptzn LLVMMemCpyOptimizer64("llvm.memcpy.i64",
1098 "Number of 'llvm.memcpy' calls simplified");
1099 LLVMMemCpyMoveOptzn LLVMMemMoveOptimizer32("llvm.memmove.i32",
1100 "Number of 'llvm.memmove' calls simplified");
1101 LLVMMemCpyMoveOptzn LLVMMemMoveOptimizer64("llvm.memmove.i64",
1102 "Number of 'llvm.memmove' calls simplified");
1104 /// This LibCallOptimization will simplify a call to the memset library
1105 /// function by expanding it out to a single store of size 0, 1, 2, 4, or 8
1106 /// bytes depending on the length argument.
1107 struct LLVMMemSetOptimization : public LibCallOptimization {
1108 /// @brief Default Constructor
1109 LLVMMemSetOptimization(const char *Name) : LibCallOptimization(Name,
1110 "Number of 'llvm.memset' calls simplified") {}
1112 /// @brief Make sure that the "memset" function has the right prototype
1113 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &TD) {
1114 // Just make sure this has 3 arguments per LLVM spec.
1115 return F->arg_size() == 4;
1118 /// Because of alignment and instruction information that we don't have, we
1119 /// leave the bulk of this to the code generators. The optimization here just
1120 /// deals with a few degenerate cases where the length parameter is constant
1121 /// and the alignment matches the sizes of our intrinsic types so we can do
1122 /// store instead of the memcpy call. Other calls are transformed into the
1123 /// llvm.memset intrinsic.
1124 /// @brief Perform the memset optimization.
1125 virtual bool OptimizeCall(CallInst *ci, SimplifyLibCalls &TD) {
1126 // Make sure we have constant int values to work with
1127 ConstantInt* LEN = dyn_cast<ConstantInt>(ci->getOperand(3));
1130 ConstantInt* ALIGN = dyn_cast<ConstantInt>(ci->getOperand(4));
1134 // Extract the length and alignment
1135 uint64_t len = LEN->getRawValue();
1136 uint64_t alignment = ALIGN->getRawValue();
1138 // Alignment 0 is identity for alignment 1
1142 // If the length is zero, this is a no-op
1144 // memset(d,c,0,a) -> noop
1145 ci->eraseFromParent();
1149 // If the length is larger than the alignment, we can't optimize
1150 if (len > alignment)
1153 // Make sure we have a constant ubyte to work with so we can extract
1154 // the value to be filled.
1155 ConstantUInt* FILL = dyn_cast<ConstantUInt>(ci->getOperand(2));
1158 if (FILL->getType() != Type::UByteTy)
1161 // memset(s,c,n) -> store s, c (for n=1,2,4,8)
1163 // Extract the fill character
1164 uint64_t fill_char = FILL->getValue();
1165 uint64_t fill_value = fill_char;
1167 // Get the type we will cast to, based on size of memory area to fill, and
1168 // and the value we will store there.
1169 Value* dest = ci->getOperand(1);
1173 castType = Type::UByteTy;
1176 castType = Type::UShortTy;
1177 fill_value |= fill_char << 8;
1180 castType = Type::UIntTy;
1181 fill_value |= fill_char << 8 | fill_char << 16 | fill_char << 24;
1184 castType = Type::ULongTy;
1185 fill_value |= fill_char << 8 | fill_char << 16 | fill_char << 24;
1186 fill_value |= fill_char << 32 | fill_char << 40 | fill_char << 48;
1187 fill_value |= fill_char << 56;
1193 // Cast dest to the right sized primitive and then load/store
1194 CastInst* DestCast =
1195 new CastInst(dest,PointerType::get(castType),dest->getName()+".cast",ci);
1196 new StoreInst(ConstantUInt::get(castType,fill_value),DestCast, ci);
1197 ci->eraseFromParent();
1202 LLVMMemSetOptimization MemSet32Optimizer("llvm.memset.i32");
1203 LLVMMemSetOptimization MemSet64Optimizer("llvm.memset.i64");
1206 /// This LibCallOptimization will simplify calls to the "pow" library
1207 /// function. It looks for cases where the result of pow is well known and
1208 /// substitutes the appropriate value.
1209 /// @brief Simplify the pow library function.
1210 struct PowOptimization : public LibCallOptimization {
1212 /// @brief Default Constructor
1213 PowOptimization() : LibCallOptimization("pow",
1214 "Number of 'pow' calls simplified") {}
1216 /// @brief Make sure that the "pow" function has the right prototype
1217 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC){
1218 // Just make sure this has 2 arguments
1219 return (f->arg_size() == 2);
1222 /// @brief Perform the pow optimization.
1223 virtual bool OptimizeCall(CallInst *ci, SimplifyLibCalls &SLC) {
1224 const Type *Ty = cast<Function>(ci->getOperand(0))->getReturnType();
1225 Value* base = ci->getOperand(1);
1226 Value* expn = ci->getOperand(2);
1227 if (ConstantFP *Op1 = dyn_cast<ConstantFP>(base)) {
1228 double Op1V = Op1->getValue();
1230 // pow(1.0,x) -> 1.0
1231 ci->replaceAllUsesWith(ConstantFP::get(Ty,1.0));
1232 ci->eraseFromParent();
1235 } else if (ConstantFP* Op2 = dyn_cast<ConstantFP>(expn)) {
1236 double Op2V = Op2->getValue();
1238 // pow(x,0.0) -> 1.0
1239 ci->replaceAllUsesWith(ConstantFP::get(Ty,1.0));
1240 ci->eraseFromParent();
1242 } else if (Op2V == 0.5) {
1243 // pow(x,0.5) -> sqrt(x)
1244 CallInst* sqrt_inst = new CallInst(SLC.get_sqrt(), base,
1245 ci->getName()+".pow",ci);
1246 ci->replaceAllUsesWith(sqrt_inst);
1247 ci->eraseFromParent();
1249 } else if (Op2V == 1.0) {
1251 ci->replaceAllUsesWith(base);
1252 ci->eraseFromParent();
1254 } else if (Op2V == -1.0) {
1255 // pow(x,-1.0) -> 1.0/x
1256 BinaryOperator* div_inst= BinaryOperator::createDiv(
1257 ConstantFP::get(Ty,1.0), base, ci->getName()+".pow", ci);
1258 ci->replaceAllUsesWith(div_inst);
1259 ci->eraseFromParent();
1263 return false; // opt failed
1267 /// This LibCallOptimization will simplify calls to the "fprintf" library
1268 /// function. It looks for cases where the result of fprintf is not used and the
1269 /// operation can be reduced to something simpler.
1270 /// @brief Simplify the pow library function.
1271 struct FPrintFOptimization : public LibCallOptimization {
1273 /// @brief Default Constructor
1274 FPrintFOptimization() : LibCallOptimization("fprintf",
1275 "Number of 'fprintf' calls simplified") {}
1277 /// @brief Make sure that the "fprintf" function has the right prototype
1278 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC){
1279 // Just make sure this has at least 2 arguments
1280 return (f->arg_size() >= 2);
1283 /// @brief Perform the fprintf optimization.
1284 virtual bool OptimizeCall(CallInst* ci, SimplifyLibCalls& SLC) {
1285 // If the call has more than 3 operands, we can't optimize it
1286 if (ci->getNumOperands() > 4 || ci->getNumOperands() <= 2)
1289 // If the result of the fprintf call is used, none of these optimizations
1291 if (!ci->use_empty())
1294 // All the optimizations depend on the length of the second argument and the
1295 // fact that it is a constant string array. Check that now
1297 ConstantArray* CA = 0;
1298 if (!getConstantStringLength(ci->getOperand(2), len, &CA))
1301 if (ci->getNumOperands() == 3) {
1302 // Make sure there's no % in the constant array
1303 for (unsigned i = 0; i < len; ++i) {
1304 if (ConstantInt* CI = dyn_cast<ConstantInt>(CA->getOperand(i))) {
1305 // Check for the null terminator
1306 if (CI->getRawValue() == '%')
1307 return false; // we found end of string
1313 // fprintf(file,fmt) -> fwrite(fmt,strlen(fmt),file)
1314 const Type* FILEptr_type = ci->getOperand(1)->getType();
1315 Function* fwrite_func = SLC.get_fwrite(FILEptr_type);
1319 // Make sure that the fprintf() and fwrite() functions both take the
1320 // same type of char pointer.
1321 if (ci->getOperand(2)->getType() !=
1322 fwrite_func->getFunctionType()->getParamType(0))
1325 std::vector<Value*> args;
1326 args.push_back(ci->getOperand(2));
1327 args.push_back(ConstantUInt::get(SLC.getIntPtrType(),len));
1328 args.push_back(ConstantUInt::get(SLC.getIntPtrType(),1));
1329 args.push_back(ci->getOperand(1));
1330 new CallInst(fwrite_func,args,ci->getName(),ci);
1331 ci->replaceAllUsesWith(ConstantSInt::get(Type::IntTy,len));
1332 ci->eraseFromParent();
1336 // The remaining optimizations require the format string to be length 2
1341 // The first character has to be a %
1342 if (ConstantInt* CI = dyn_cast<ConstantInt>(CA->getOperand(0)))
1343 if (CI->getRawValue() != '%')
1346 // Get the second character and switch on its value
1347 ConstantInt* CI = dyn_cast<ConstantInt>(CA->getOperand(1));
1348 switch (CI->getRawValue()) {
1352 ConstantArray* CA = 0;
1353 if (getConstantStringLength(ci->getOperand(3), len, &CA)) {
1354 // fprintf(file,"%s",str) -> fwrite(str,strlen(str),1,file)
1355 const Type* FILEptr_type = ci->getOperand(1)->getType();
1356 Function* fwrite_func = SLC.get_fwrite(FILEptr_type);
1359 std::vector<Value*> args;
1360 args.push_back(CastToCStr(ci->getOperand(3), *ci));
1361 args.push_back(ConstantUInt::get(SLC.getIntPtrType(),len));
1362 args.push_back(ConstantUInt::get(SLC.getIntPtrType(),1));
1363 args.push_back(ci->getOperand(1));
1364 new CallInst(fwrite_func,args,ci->getName(),ci);
1365 ci->replaceAllUsesWith(ConstantSInt::get(Type::IntTy,len));
1367 // fprintf(file,"%s",str) -> fputs(str,file)
1368 const Type* FILEptr_type = ci->getOperand(1)->getType();
1369 Function* fputs_func = SLC.get_fputs(FILEptr_type);
1372 std::vector<Value*> args;
1373 args.push_back(ci->getOperand(3));
1374 args.push_back(ci->getOperand(1));
1375 new CallInst(fputs_func,args,ci->getName(),ci);
1376 ci->replaceAllUsesWith(ConstantSInt::get(Type::IntTy,len));
1382 ConstantInt* CI = dyn_cast<ConstantInt>(ci->getOperand(3));
1386 const Type* FILEptr_type = ci->getOperand(1)->getType();
1387 Function* fputc_func = SLC.get_fputc(FILEptr_type);
1390 CastInst* cast = new CastInst(CI,Type::IntTy,CI->getName()+".int",ci);
1391 new CallInst(fputc_func,cast,ci->getOperand(1),"",ci);
1392 ci->replaceAllUsesWith(ConstantSInt::get(Type::IntTy,1));
1398 ci->eraseFromParent();
1403 /// This LibCallOptimization will simplify calls to the "sprintf" library
1404 /// function. It looks for cases where the result of sprintf is not used and the
1405 /// operation can be reduced to something simpler.
1406 /// @brief Simplify the pow library function.
1407 struct SPrintFOptimization : public LibCallOptimization {
1409 /// @brief Default Constructor
1410 SPrintFOptimization() : LibCallOptimization("sprintf",
1411 "Number of 'sprintf' calls simplified") {}
1413 /// @brief Make sure that the "fprintf" function has the right prototype
1414 virtual bool ValidateCalledFunction(const Function *f, SimplifyLibCalls &SLC){
1415 // Just make sure this has at least 2 arguments
1416 return (f->getReturnType() == Type::IntTy && f->arg_size() >= 2);
1419 /// @brief Perform the sprintf optimization.
1420 virtual bool OptimizeCall(CallInst *ci, SimplifyLibCalls &SLC) {
1421 // If the call has more than 3 operands, we can't optimize it
1422 if (ci->getNumOperands() > 4 || ci->getNumOperands() < 3)
1425 // All the optimizations depend on the length of the second argument and the
1426 // fact that it is a constant string array. Check that now
1428 ConstantArray* CA = 0;
1429 if (!getConstantStringLength(ci->getOperand(2), len, &CA))
1432 if (ci->getNumOperands() == 3) {
1434 // If the length is 0, we just need to store a null byte
1435 new StoreInst(ConstantInt::get(Type::SByteTy,0),ci->getOperand(1),ci);
1436 ci->replaceAllUsesWith(ConstantSInt::get(Type::IntTy,0));
1437 ci->eraseFromParent();
1441 // Make sure there's no % in the constant array
1442 for (unsigned i = 0; i < len; ++i) {
1443 if (ConstantInt* CI = dyn_cast<ConstantInt>(CA->getOperand(i))) {
1444 // Check for the null terminator
1445 if (CI->getRawValue() == '%')
1446 return false; // we found a %, can't optimize
1448 return false; // initializer is not constant int, can't optimize
1452 // Increment length because we want to copy the null byte too
1455 // sprintf(str,fmt) -> llvm.memcpy(str,fmt,strlen(fmt),1)
1456 Function* memcpy_func = SLC.get_memcpy();
1459 std::vector<Value*> args;
1460 args.push_back(ci->getOperand(1));
1461 args.push_back(ci->getOperand(2));
1462 args.push_back(ConstantUInt::get(SLC.getIntPtrType(),len));
1463 args.push_back(ConstantUInt::get(Type::UIntTy,1));
1464 new CallInst(memcpy_func,args,"",ci);
1465 ci->replaceAllUsesWith(ConstantSInt::get(Type::IntTy,len));
1466 ci->eraseFromParent();
1470 // The remaining optimizations require the format string to be length 2
1475 // The first character has to be a %
1476 if (ConstantInt* CI = dyn_cast<ConstantInt>(CA->getOperand(0)))
1477 if (CI->getRawValue() != '%')
1480 // Get the second character and switch on its value
1481 ConstantInt* CI = dyn_cast<ConstantInt>(CA->getOperand(1));
1482 switch (CI->getRawValue()) {
1484 // sprintf(dest,"%s",str) -> llvm.memcpy(dest, str, strlen(str)+1, 1)
1485 Function* strlen_func = SLC.get_strlen();
1486 Function* memcpy_func = SLC.get_memcpy();
1487 if (!strlen_func || !memcpy_func)
1490 Value *Len = new CallInst(strlen_func, CastToCStr(ci->getOperand(3), *ci),
1491 ci->getOperand(3)->getName()+".len", ci);
1492 Value *Len1 = BinaryOperator::createAdd(Len,
1493 ConstantInt::get(Len->getType(), 1),
1494 Len->getName()+"1", ci);
1495 if (Len1->getType() != SLC.getIntPtrType())
1496 Len1 = new CastInst(Len1, SLC.getIntPtrType(), Len1->getName(), ci);
1497 std::vector<Value*> args;
1498 args.push_back(CastToCStr(ci->getOperand(1), *ci));
1499 args.push_back(CastToCStr(ci->getOperand(3), *ci));
1500 args.push_back(Len1);
1501 args.push_back(ConstantUInt::get(Type::UIntTy,1));
1502 new CallInst(memcpy_func, args, "", ci);
1504 // The strlen result is the unincremented number of bytes in the string.
1505 if (!ci->use_empty()) {
1506 if (Len->getType() != ci->getType())
1507 Len = new CastInst(Len, ci->getType(), Len->getName(), ci);
1508 ci->replaceAllUsesWith(Len);
1510 ci->eraseFromParent();
1514 // sprintf(dest,"%c",chr) -> store chr, dest
1515 CastInst* cast = new CastInst(ci->getOperand(3),Type::SByteTy,"char",ci);
1516 new StoreInst(cast, ci->getOperand(1), ci);
1517 GetElementPtrInst* gep = new GetElementPtrInst(ci->getOperand(1),
1518 ConstantUInt::get(Type::UIntTy,1),ci->getOperand(1)->getName()+".end",
1520 new StoreInst(ConstantInt::get(Type::SByteTy,0),gep,ci);
1521 ci->replaceAllUsesWith(ConstantSInt::get(Type::IntTy,1));
1522 ci->eraseFromParent();
1530 /// This LibCallOptimization will simplify calls to the "fputs" library
1531 /// function. It looks for cases where the result of fputs is not used and the
1532 /// operation can be reduced to something simpler.
1533 /// @brief Simplify the pow library function.
1534 struct PutsOptimization : public LibCallOptimization {
1536 /// @brief Default Constructor
1537 PutsOptimization() : LibCallOptimization("fputs",
1538 "Number of 'fputs' calls simplified") {}
1540 /// @brief Make sure that the "fputs" function has the right prototype
1541 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
1542 // Just make sure this has 2 arguments
1543 return F->arg_size() == 2;
1546 /// @brief Perform the fputs optimization.
1547 virtual bool OptimizeCall(CallInst* ci, SimplifyLibCalls& SLC) {
1548 // If the result is used, none of these optimizations work
1549 if (!ci->use_empty())
1552 // All the optimizations depend on the length of the first argument and the
1553 // fact that it is a constant string array. Check that now
1555 if (!getConstantStringLength(ci->getOperand(1), len))
1560 // fputs("",F) -> noop
1564 // fputs(s,F) -> fputc(s[0],F) (if s is constant and strlen(s) == 1)
1565 const Type* FILEptr_type = ci->getOperand(2)->getType();
1566 Function* fputc_func = SLC.get_fputc(FILEptr_type);
1569 LoadInst* loadi = new LoadInst(ci->getOperand(1),
1570 ci->getOperand(1)->getName()+".byte",ci);
1571 CastInst* casti = new CastInst(loadi,Type::IntTy,
1572 loadi->getName()+".int",ci);
1573 new CallInst(fputc_func,casti,ci->getOperand(2),"",ci);
1578 // fputs(s,F) -> fwrite(s,1,len,F) (if s is constant and strlen(s) > 1)
1579 const Type* FILEptr_type = ci->getOperand(2)->getType();
1580 Function* fwrite_func = SLC.get_fwrite(FILEptr_type);
1583 std::vector<Value*> parms;
1584 parms.push_back(ci->getOperand(1));
1585 parms.push_back(ConstantUInt::get(SLC.getIntPtrType(),len));
1586 parms.push_back(ConstantUInt::get(SLC.getIntPtrType(),1));
1587 parms.push_back(ci->getOperand(2));
1588 new CallInst(fwrite_func,parms,"",ci);
1592 ci->eraseFromParent();
1593 return true; // success
1597 /// This LibCallOptimization will simplify calls to the "isdigit" library
1598 /// function. It simply does range checks the parameter explicitly.
1599 /// @brief Simplify the isdigit library function.
1600 struct isdigitOptimization : public LibCallOptimization {
1602 isdigitOptimization() : LibCallOptimization("isdigit",
1603 "Number of 'isdigit' calls simplified") {}
1605 /// @brief Make sure that the "isdigit" function has the right prototype
1606 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC){
1607 // Just make sure this has 1 argument
1608 return (f->arg_size() == 1);
1611 /// @brief Perform the toascii optimization.
1612 virtual bool OptimizeCall(CallInst *ci, SimplifyLibCalls &SLC) {
1613 if (ConstantInt* CI = dyn_cast<ConstantInt>(ci->getOperand(1))) {
1614 // isdigit(c) -> 0 or 1, if 'c' is constant
1615 uint64_t val = CI->getRawValue();
1616 if (val >= '0' && val <='9')
1617 ci->replaceAllUsesWith(ConstantSInt::get(Type::IntTy,1));
1619 ci->replaceAllUsesWith(ConstantSInt::get(Type::IntTy,0));
1620 ci->eraseFromParent();
1624 // isdigit(c) -> (unsigned)c - '0' <= 9
1626 new CastInst(ci->getOperand(1),Type::UIntTy,
1627 ci->getOperand(1)->getName()+".uint",ci);
1628 BinaryOperator* sub_inst = BinaryOperator::createSub(cast,
1629 ConstantUInt::get(Type::UIntTy,0x30),
1630 ci->getOperand(1)->getName()+".sub",ci);
1631 SetCondInst* setcond_inst = new SetCondInst(Instruction::SetLE,sub_inst,
1632 ConstantUInt::get(Type::UIntTy,9),
1633 ci->getOperand(1)->getName()+".cmp",ci);
1635 new CastInst(setcond_inst,Type::IntTy,
1636 ci->getOperand(1)->getName()+".isdigit",ci);
1637 ci->replaceAllUsesWith(c2);
1638 ci->eraseFromParent();
1643 struct isasciiOptimization : public LibCallOptimization {
1645 isasciiOptimization()
1646 : LibCallOptimization("isascii", "Number of 'isascii' calls simplified") {}
1648 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
1649 return F->arg_size() == 1 && F->arg_begin()->getType()->isInteger() &&
1650 F->getReturnType()->isInteger();
1653 /// @brief Perform the isascii optimization.
1654 virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
1655 // isascii(c) -> (unsigned)c < 128
1656 Value *V = CI->getOperand(1);
1657 if (V->getType()->isSigned())
1658 V = new CastInst(V, V->getType()->getUnsignedVersion(), V->getName(), CI);
1659 Value *Cmp = BinaryOperator::createSetLT(V, ConstantUInt::get(V->getType(),
1661 V->getName()+".isascii", CI);
1662 if (Cmp->getType() != CI->getType())
1663 Cmp = new CastInst(Cmp, CI->getType(), Cmp->getName(), CI);
1664 CI->replaceAllUsesWith(Cmp);
1665 CI->eraseFromParent();
1671 /// This LibCallOptimization will simplify calls to the "toascii" library
1672 /// function. It simply does the corresponding and operation to restrict the
1673 /// range of values to the ASCII character set (0-127).
1674 /// @brief Simplify the toascii library function.
1675 struct ToAsciiOptimization : public LibCallOptimization {
1677 /// @brief Default Constructor
1678 ToAsciiOptimization() : LibCallOptimization("toascii",
1679 "Number of 'toascii' calls simplified") {}
1681 /// @brief Make sure that the "fputs" function has the right prototype
1682 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC){
1683 // Just make sure this has 2 arguments
1684 return (f->arg_size() == 1);
1687 /// @brief Perform the toascii optimization.
1688 virtual bool OptimizeCall(CallInst *ci, SimplifyLibCalls &SLC) {
1689 // toascii(c) -> (c & 0x7f)
1690 Value* chr = ci->getOperand(1);
1691 BinaryOperator* and_inst = BinaryOperator::createAnd(chr,
1692 ConstantInt::get(chr->getType(),0x7F),ci->getName()+".toascii",ci);
1693 ci->replaceAllUsesWith(and_inst);
1694 ci->eraseFromParent();
1699 /// This LibCallOptimization will simplify calls to the "ffs" library
1700 /// calls which find the first set bit in an int, long, or long long. The
1701 /// optimization is to compute the result at compile time if the argument is
1703 /// @brief Simplify the ffs library function.
1704 struct FFSOptimization : public LibCallOptimization {
1706 /// @brief Subclass Constructor
1707 FFSOptimization(const char* funcName, const char* description)
1708 : LibCallOptimization(funcName, description) {}
1711 /// @brief Default Constructor
1712 FFSOptimization() : LibCallOptimization("ffs",
1713 "Number of 'ffs' calls simplified") {}
1715 /// @brief Make sure that the "ffs" function has the right prototype
1716 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
1717 // Just make sure this has 2 arguments
1718 return F->arg_size() == 1 && F->getReturnType() == Type::IntTy;
1721 /// @brief Perform the ffs optimization.
1722 virtual bool OptimizeCall(CallInst *TheCall, SimplifyLibCalls &SLC) {
1723 if (ConstantInt *CI = dyn_cast<ConstantInt>(TheCall->getOperand(1))) {
1724 // ffs(cnst) -> bit#
1725 // ffsl(cnst) -> bit#
1726 // ffsll(cnst) -> bit#
1727 uint64_t val = CI->getRawValue();
1731 while ((val & 1) == 0) {
1736 TheCall->replaceAllUsesWith(ConstantSInt::get(Type::IntTy, result));
1737 TheCall->eraseFromParent();
1741 // ffs(x) -> x == 0 ? 0 : llvm.cttz(x)+1
1742 // ffsl(x) -> x == 0 ? 0 : llvm.cttz(x)+1
1743 // ffsll(x) -> x == 0 ? 0 : llvm.cttz(x)+1
1744 const Type *ArgType = TheCall->getOperand(1)->getType();
1745 ArgType = ArgType->getUnsignedVersion();
1746 const char *CTTZName;
1747 switch (ArgType->getTypeID()) {
1748 default: assert(0 && "Unknown unsigned type!");
1749 case Type::UByteTyID : CTTZName = "llvm.cttz.i8" ; break;
1750 case Type::UShortTyID: CTTZName = "llvm.cttz.i16"; break;
1751 case Type::UIntTyID : CTTZName = "llvm.cttz.i32"; break;
1752 case Type::ULongTyID : CTTZName = "llvm.cttz.i64"; break;
1755 Function *F = SLC.getModule()->getOrInsertFunction(CTTZName, ArgType,
1757 Value *V = new CastInst(TheCall->getOperand(1), ArgType, "tmp", TheCall);
1758 Value *V2 = new CallInst(F, V, "tmp", TheCall);
1759 V2 = new CastInst(V2, Type::IntTy, "tmp", TheCall);
1760 V2 = BinaryOperator::createAdd(V2, ConstantSInt::get(Type::IntTy, 1),
1763 BinaryOperator::createSetEQ(V, Constant::getNullValue(V->getType()),
1765 V2 = new SelectInst(Cond, ConstantInt::get(Type::IntTy, 0), V2,
1766 TheCall->getName(), TheCall);
1767 TheCall->replaceAllUsesWith(V2);
1768 TheCall->eraseFromParent();
1773 /// This LibCallOptimization will simplify calls to the "ffsl" library
1774 /// calls. It simply uses FFSOptimization for which the transformation is
1776 /// @brief Simplify the ffsl library function.
1777 struct FFSLOptimization : public FFSOptimization {
1779 /// @brief Default Constructor
1780 FFSLOptimization() : FFSOptimization("ffsl",
1781 "Number of 'ffsl' calls simplified") {}
1785 /// This LibCallOptimization will simplify calls to the "ffsll" library
1786 /// calls. It simply uses FFSOptimization for which the transformation is
1788 /// @brief Simplify the ffsl library function.
1789 struct FFSLLOptimization : public FFSOptimization {
1791 /// @brief Default Constructor
1792 FFSLLOptimization() : FFSOptimization("ffsll",
1793 "Number of 'ffsll' calls simplified") {}
1797 /// This optimizes unary functions that take and return doubles.
1798 struct UnaryDoubleFPOptimizer : public LibCallOptimization {
1799 UnaryDoubleFPOptimizer(const char *Fn, const char *Desc)
1800 : LibCallOptimization(Fn, Desc) {}
1802 // Make sure that this function has the right prototype
1803 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
1804 return F->arg_size() == 1 && F->arg_begin()->getType() == Type::DoubleTy &&
1805 F->getReturnType() == Type::DoubleTy;
1808 /// ShrinkFunctionToFloatVersion - If the input to this function is really a
1809 /// float, strength reduce this to a float version of the function,
1810 /// e.g. floor((double)FLT) -> (double)floorf(FLT). This can only be called
1811 /// when the target supports the destination function and where there can be
1812 /// no precision loss.
1813 static bool ShrinkFunctionToFloatVersion(CallInst *CI, SimplifyLibCalls &SLC,
1814 Function *(SimplifyLibCalls::*FP)()){
1815 if (CastInst *Cast = dyn_cast<CastInst>(CI->getOperand(1)))
1816 if (Cast->getOperand(0)->getType() == Type::FloatTy) {
1817 Value *New = new CallInst((SLC.*FP)(), Cast->getOperand(0),
1819 New = new CastInst(New, Type::DoubleTy, CI->getName(), CI);
1820 CI->replaceAllUsesWith(New);
1821 CI->eraseFromParent();
1822 if (Cast->use_empty())
1823 Cast->eraseFromParent();
1831 struct FloorOptimization : public UnaryDoubleFPOptimizer {
1833 : UnaryDoubleFPOptimizer("floor", "Number of 'floor' calls simplified") {}
1835 virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
1837 // If this is a float argument passed in, convert to floorf.
1838 if (ShrinkFunctionToFloatVersion(CI, SLC, &SimplifyLibCalls::get_floorf))
1841 return false; // opt failed
1845 struct CeilOptimization : public UnaryDoubleFPOptimizer {
1847 : UnaryDoubleFPOptimizer("ceil", "Number of 'ceil' calls simplified") {}
1849 virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
1851 // If this is a float argument passed in, convert to ceilf.
1852 if (ShrinkFunctionToFloatVersion(CI, SLC, &SimplifyLibCalls::get_ceilf))
1855 return false; // opt failed
1859 struct RoundOptimization : public UnaryDoubleFPOptimizer {
1861 : UnaryDoubleFPOptimizer("round", "Number of 'round' calls simplified") {}
1863 virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
1865 // If this is a float argument passed in, convert to roundf.
1866 if (ShrinkFunctionToFloatVersion(CI, SLC, &SimplifyLibCalls::get_roundf))
1869 return false; // opt failed
1873 struct RintOptimization : public UnaryDoubleFPOptimizer {
1875 : UnaryDoubleFPOptimizer("rint", "Number of 'rint' calls simplified") {}
1877 virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
1879 // If this is a float argument passed in, convert to rintf.
1880 if (ShrinkFunctionToFloatVersion(CI, SLC, &SimplifyLibCalls::get_rintf))
1883 return false; // opt failed
1887 struct NearByIntOptimization : public UnaryDoubleFPOptimizer {
1888 NearByIntOptimization()
1889 : UnaryDoubleFPOptimizer("nearbyint",
1890 "Number of 'nearbyint' calls simplified") {}
1892 virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
1893 #ifdef HAVE_NEARBYINTF
1894 // If this is a float argument passed in, convert to nearbyintf.
1895 if (ShrinkFunctionToFloatVersion(CI, SLC,&SimplifyLibCalls::get_nearbyintf))
1898 return false; // opt failed
1900 } NearByIntOptimizer;
1902 /// A function to compute the length of a null-terminated constant array of
1903 /// integers. This function can't rely on the size of the constant array
1904 /// because there could be a null terminator in the middle of the array.
1905 /// We also have to bail out if we find a non-integer constant initializer
1906 /// of one of the elements or if there is no null-terminator. The logic
1907 /// below checks each of these conditions and will return true only if all
1908 /// conditions are met. In that case, the \p len parameter is set to the length
1909 /// of the null-terminated string. If false is returned, the conditions were
1910 /// not met and len is set to 0.
1911 /// @brief Get the length of a constant string (null-terminated array).
1912 bool getConstantStringLength(Value *V, uint64_t &len, ConstantArray **CA) {
1913 assert(V != 0 && "Invalid args to getConstantStringLength");
1914 len = 0; // make sure we initialize this
1916 // If the value is not a GEP instruction nor a constant expression with a
1917 // GEP instruction, then return false because ConstantArray can't occur
1919 if (GetElementPtrInst* GEPI = dyn_cast<GetElementPtrInst>(V))
1921 else if (ConstantExpr* CE = dyn_cast<ConstantExpr>(V))
1922 if (CE->getOpcode() == Instruction::GetElementPtr)
1929 // Make sure the GEP has exactly three arguments.
1930 if (GEP->getNumOperands() != 3)
1933 // Check to make sure that the first operand of the GEP is an integer and
1934 // has value 0 so that we are sure we're indexing into the initializer.
1935 if (ConstantInt* op1 = dyn_cast<ConstantInt>(GEP->getOperand(1))) {
1936 if (!op1->isNullValue())
1941 // Ensure that the second operand is a ConstantInt. If it isn't then this
1942 // GEP is wonky and we're not really sure what were referencing into and
1943 // better of not optimizing it. While we're at it, get the second index
1944 // value. We'll need this later for indexing the ConstantArray.
1945 uint64_t start_idx = 0;
1946 if (ConstantInt* CI = dyn_cast<ConstantInt>(GEP->getOperand(2)))
1947 start_idx = CI->getRawValue();
1951 // The GEP instruction, constant or instruction, must reference a global
1952 // variable that is a constant and is initialized. The referenced constant
1953 // initializer is the array that we'll use for optimization.
1954 GlobalVariable* GV = dyn_cast<GlobalVariable>(GEP->getOperand(0));
1955 if (!GV || !GV->isConstant() || !GV->hasInitializer())
1958 // Get the initializer.
1959 Constant* INTLZR = GV->getInitializer();
1961 // Handle the ConstantAggregateZero case
1962 if (ConstantAggregateZero *CAZ = dyn_cast<ConstantAggregateZero>(INTLZR)) {
1963 // This is a degenerate case. The initializer is constant zero so the
1964 // length of the string must be zero.
1969 // Must be a Constant Array
1970 ConstantArray* A = dyn_cast<ConstantArray>(INTLZR);
1974 // Get the number of elements in the array
1975 uint64_t max_elems = A->getType()->getNumElements();
1977 // Traverse the constant array from start_idx (derived above) which is
1978 // the place the GEP refers to in the array.
1979 for (len = start_idx; len < max_elems; len++) {
1980 if (ConstantInt *CI = dyn_cast<ConstantInt>(A->getOperand(len))) {
1981 // Check for the null terminator
1982 if (CI->isNullValue())
1983 break; // we found end of string
1985 return false; // This array isn't suitable, non-int initializer
1988 if (len >= max_elems)
1989 return false; // This array isn't null terminated
1991 // Subtract out the initial value from the length
1995 return true; // success!
1998 /// CastToCStr - Return V if it is an sbyte*, otherwise cast it to sbyte*,
1999 /// inserting the cast before IP, and return the cast.
2000 /// @brief Cast a value to a "C" string.
2001 Value *CastToCStr(Value *V, Instruction &IP) {
2002 const Type *SBPTy = PointerType::get(Type::SByteTy);
2003 if (V->getType() != SBPTy)
2004 return new CastInst(V, SBPTy, V->getName(), &IP);
2009 // Additional cases that we need to add to this file:
2012 // * cbrt(expN(X)) -> expN(x/3)
2013 // * cbrt(sqrt(x)) -> pow(x,1/6)
2014 // * cbrt(sqrt(x)) -> pow(x,1/9)
2017 // * cos(-x) -> cos(x)
2020 // * exp(log(x)) -> x
2023 // * log(exp(x)) -> x
2024 // * log(x**y) -> y*log(x)
2025 // * log(exp(y)) -> y*log(e)
2026 // * log(exp2(y)) -> y*log(2)
2027 // * log(exp10(y)) -> y*log(10)
2028 // * log(sqrt(x)) -> 0.5*log(x)
2029 // * log(pow(x,y)) -> y*log(x)
2031 // lround, lroundf, lroundl:
2032 // * lround(cnst) -> cnst'
2035 // * memcmp(x,y,l) -> cnst
2036 // (if all arguments are constant and strlen(x) <= l and strlen(y) <= l)
2039 // * memmove(d,s,l,a) -> memcpy(d,s,l,a)
2040 // (if s is a global constant array)
2043 // * pow(exp(x),y) -> exp(x*y)
2044 // * pow(sqrt(x),y) -> pow(x,y*0.5)
2045 // * pow(pow(x,y),z)-> pow(x,y*z)
2048 // * puts("") -> fputc("\n",stdout) (how do we get "stdout"?)
2050 // round, roundf, roundl:
2051 // * round(cnst) -> cnst'
2054 // * signbit(cnst) -> cnst'
2055 // * signbit(nncst) -> 0 (if pstv is a non-negative constant)
2057 // sqrt, sqrtf, sqrtl:
2058 // * sqrt(expN(x)) -> expN(x*0.5)
2059 // * sqrt(Nroot(x)) -> pow(x,1/(2*N))
2060 // * sqrt(pow(x,y)) -> pow(|x|,y*0.5)
2063 // * stpcpy(str, "literal") ->
2064 // llvm.memcpy(str,"literal",strlen("literal")+1,1)
2066 // * strrchr(s,c) -> reverse_offset_of_in(c,s)
2067 // (if c is a constant integer and s is a constant string)
2068 // * strrchr(s1,0) -> strchr(s1,0)
2071 // * strncat(x,y,0) -> x
2072 // * strncat(x,y,0) -> x (if strlen(y) = 0)
2073 // * strncat(x,y,l) -> strcat(x,y) (if y and l are constants an l > strlen(y))
2076 // * strncpy(d,s,0) -> d
2077 // * strncpy(d,s,l) -> memcpy(d,s,l,1)
2078 // (if s and l are constants)
2081 // * strpbrk(s,a) -> offset_in_for(s,a)
2082 // (if s and a are both constant strings)
2083 // * strpbrk(s,"") -> 0
2084 // * strpbrk(s,a) -> strchr(s,a[0]) (if a is constant string of length 1)
2087 // * strspn(s,a) -> const_int (if both args are constant)
2088 // * strspn("",a) -> 0
2089 // * strspn(s,"") -> 0
2090 // * strcspn(s,a) -> const_int (if both args are constant)
2091 // * strcspn("",a) -> 0
2092 // * strcspn(s,"") -> strlen(a)
2095 // * strstr(x,x) -> x
2096 // * strstr(s1,s2) -> offset_of_s2_in(s1)
2097 // (if s1 and s2 are constant strings)
2100 // * tan(atan(x)) -> x
2102 // trunc, truncf, truncl:
2103 // * trunc(cnst) -> cnst'