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"
34 /// This statistic keeps track of the total number of library calls that have
35 /// been simplified regardless of which call it is.
36 STATISTIC(SimplifiedLibCalls, "Number of library calls simplified");
39 // Forward declarations
40 class LibCallOptimization;
41 class SimplifyLibCalls;
43 /// This list is populated by the constructor for LibCallOptimization class.
44 /// Therefore all subclasses are registered here at static initialization time
45 /// and this list is what the SimplifyLibCalls pass uses to apply the individual
46 /// optimizations to the call sites.
47 /// @brief The list of optimizations deriving from LibCallOptimization
48 static LibCallOptimization *OptList = 0;
50 /// This class is the abstract base class for the set of optimizations that
51 /// corresponds to one library call. The SimplifyLibCalls pass will call the
52 /// ValidateCalledFunction method to ask the optimization if a given Function
53 /// is the kind that the optimization can handle. If the subclass returns true,
54 /// then SImplifyLibCalls will also call the OptimizeCall method to perform,
55 /// or attempt to perform, the optimization(s) for the library call. Otherwise,
56 /// OptimizeCall won't be called. Subclasses are responsible for providing the
57 /// name of the library call (strlen, strcpy, etc.) to the LibCallOptimization
58 /// constructor. This is used to efficiently select which call instructions to
59 /// optimize. The criteria for a "lib call" is "anything with well known
60 /// semantics", typically a library function that is defined by an international
61 /// standard. Because the semantics are well known, the optimizations can
62 /// generally short-circuit actually calling the function if there's a simpler
63 /// way (e.g. strlen(X) can be reduced to a constant if X is a constant global).
64 /// @brief Base class for library call optimizations
65 class LibCallOptimization {
66 LibCallOptimization **Prev, *Next;
67 const char *FunctionName; ///< Name of the library call we optimize
69 Statistic occurrences; ///< debug statistic (-debug-only=simplify-libcalls)
72 /// The \p fname argument must be the name of the library function being
73 /// optimized by the subclass.
74 /// @brief Constructor that registers the optimization.
75 LibCallOptimization(const char *FName, const char *Description)
76 : FunctionName(FName) {
79 occurrences.construct("simplify-libcalls", Description);
81 // Register this optimizer in the list of optimizations.
85 if (Next) Next->Prev = &Next;
88 /// getNext - All libcall optimizations are chained together into a list,
89 /// return the next one in the list.
90 LibCallOptimization *getNext() { return Next; }
92 /// @brief Deregister from the optlist
93 virtual ~LibCallOptimization() {
95 if (Next) Next->Prev = Prev;
98 /// The implementation of this function in subclasses should determine if
99 /// \p F is suitable for the optimization. This method is called by
100 /// SimplifyLibCalls::runOnModule to short circuit visiting all the call
101 /// sites of such a function if that function is not suitable in the first
102 /// place. If the called function is suitabe, this method should return true;
103 /// false, otherwise. This function should also perform any lazy
104 /// initialization that the LibCallOptimization needs to do, if its to return
105 /// true. This avoids doing initialization until the optimizer is actually
106 /// going to be called upon to do some optimization.
107 /// @brief Determine if the function is suitable for optimization
108 virtual bool ValidateCalledFunction(
109 const Function* F, ///< The function that is the target of call sites
110 SimplifyLibCalls& SLC ///< The pass object invoking us
113 /// The implementations of this function in subclasses is the heart of the
114 /// SimplifyLibCalls algorithm. Sublcasses of this class implement
115 /// OptimizeCall to determine if (a) the conditions are right for optimizing
116 /// the call and (b) to perform the optimization. If an action is taken
117 /// against ci, the subclass is responsible for returning true and ensuring
118 /// that ci is erased from its parent.
119 /// @brief Optimize a call, if possible.
120 virtual bool OptimizeCall(
121 CallInst* ci, ///< The call instruction that should be optimized.
122 SimplifyLibCalls& SLC ///< The pass object invoking us
125 /// @brief Get the name of the library call being optimized
126 const char *getFunctionName() const { return FunctionName; }
128 /// @brief Called by SimplifyLibCalls to update the occurrences statistic.
131 DEBUG(++occurrences);
136 /// This class is an LLVM Pass that applies each of the LibCallOptimization
137 /// instances to all the call sites in a module, relatively efficiently. The
138 /// purpose of this pass is to provide optimizations for calls to well-known
139 /// functions with well-known semantics, such as those in the c library. The
140 /// class provides the basic infrastructure for handling runOnModule. Whenever
141 /// this pass finds a function call, it asks the appropriate optimizer to
142 /// validate the call (ValidateLibraryCall). If it is validated, then
143 /// the OptimizeCall method is also called.
144 /// @brief A ModulePass for optimizing well-known function calls.
145 class SimplifyLibCalls : public ModulePass {
147 /// We need some target data for accurate signature details that are
148 /// target dependent. So we require target data in our AnalysisUsage.
149 /// @brief Require TargetData from AnalysisUsage.
150 virtual void getAnalysisUsage(AnalysisUsage& Info) const {
151 // Ask that the TargetData analysis be performed before us so we can use
153 Info.addRequired<TargetData>();
156 /// For this pass, process all of the function calls in the module, calling
157 /// ValidateLibraryCall and OptimizeCall as appropriate.
158 /// @brief Run all the lib call optimizations on a Module.
159 virtual bool runOnModule(Module &M) {
163 hash_map<std::string, LibCallOptimization*> OptznMap;
164 for (LibCallOptimization *Optzn = OptList; Optzn; Optzn = Optzn->getNext())
165 OptznMap[Optzn->getFunctionName()] = Optzn;
167 // The call optimizations can be recursive. That is, the optimization might
168 // generate a call to another function which can also be optimized. This way
169 // we make the LibCallOptimization instances very specific to the case they
170 // handle. It also means we need to keep running over the function calls in
171 // the module until we don't get any more optimizations possible.
172 bool found_optimization = false;
174 found_optimization = false;
175 for (Module::iterator FI = M.begin(), FE = M.end(); FI != FE; ++FI) {
176 // All the "well-known" functions are external and have external linkage
177 // because they live in a runtime library somewhere and were (probably)
178 // not compiled by LLVM. So, we only act on external functions that
179 // have external or dllimport linkage and non-empty uses.
180 if (!FI->isExternal() ||
181 !(FI->hasExternalLinkage() || FI->hasDLLImportLinkage()) ||
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 putchar libcall
225 Constant *get_putchar() {
228 M->getOrInsertFunction("putchar", Type::Int32Ty, Type::Int32Ty, NULL);
232 /// @brief Return a Function* for the puts libcall
233 Constant *get_puts() {
235 puts_func = M->getOrInsertFunction("puts", Type::Int32Ty,
236 PointerType::get(Type::Int8Ty),
241 /// @brief Return a Function* for the fputc libcall
242 Constant *get_fputc(const Type* FILEptr_type) {
244 fputc_func = M->getOrInsertFunction("fputc", Type::Int32Ty, Type::Int32Ty,
249 /// @brief Return a Function* for the fputs libcall
250 Constant *get_fputs(const Type* FILEptr_type) {
252 fputs_func = M->getOrInsertFunction("fputs", Type::Int32Ty,
253 PointerType::get(Type::Int8Ty),
258 /// @brief Return a Function* for the fwrite libcall
259 Constant *get_fwrite(const Type* FILEptr_type) {
261 fwrite_func = M->getOrInsertFunction("fwrite", TD->getIntPtrType(),
262 PointerType::get(Type::Int8Ty),
269 /// @brief Return a Function* for the sqrt libcall
270 Constant *get_sqrt() {
272 sqrt_func = M->getOrInsertFunction("sqrt", Type::DoubleTy,
273 Type::DoubleTy, NULL);
277 /// @brief Return a Function* for the strlen libcall
278 Constant *get_strcpy() {
280 strcpy_func = M->getOrInsertFunction("strcpy",
281 PointerType::get(Type::Int8Ty),
282 PointerType::get(Type::Int8Ty),
283 PointerType::get(Type::Int8Ty),
288 /// @brief Return a Function* for the strlen libcall
289 Constant *get_strlen() {
291 strlen_func = M->getOrInsertFunction("strlen", TD->getIntPtrType(),
292 PointerType::get(Type::Int8Ty),
297 /// @brief Return a Function* for the memchr libcall
298 Constant *get_memchr() {
300 memchr_func = M->getOrInsertFunction("memchr",
301 PointerType::get(Type::Int8Ty),
302 PointerType::get(Type::Int8Ty),
303 Type::Int32Ty, TD->getIntPtrType(),
308 /// @brief Return a Function* for the memcpy libcall
309 Constant *get_memcpy() {
311 const Type *SBP = PointerType::get(Type::Int8Ty);
312 const char *N = TD->getIntPtrType() == Type::Int32Ty ?
313 "llvm.memcpy.i32" : "llvm.memcpy.i64";
314 memcpy_func = M->getOrInsertFunction(N, Type::VoidTy, SBP, SBP,
315 TD->getIntPtrType(), Type::Int32Ty,
321 Constant *getUnaryFloatFunction(const char *Name, Constant *&Cache) {
323 Cache = M->getOrInsertFunction(Name, Type::FloatTy, Type::FloatTy, NULL);
327 Constant *get_floorf() { return getUnaryFloatFunction("floorf", floorf_func);}
328 Constant *get_ceilf() { return getUnaryFloatFunction( "ceilf", ceilf_func);}
329 Constant *get_roundf() { return getUnaryFloatFunction("roundf", roundf_func);}
330 Constant *get_rintf() { return getUnaryFloatFunction( "rintf", rintf_func);}
331 Constant *get_nearbyintf() { return getUnaryFloatFunction("nearbyintf",
334 /// @brief Reset our cached data for a new Module
335 void reset(Module& mod) {
337 TD = &getAnalysis<TargetData>();
356 /// Caches for function pointers.
357 Constant *putchar_func, *puts_func;
358 Constant *fputc_func, *fputs_func, *fwrite_func;
359 Constant *memcpy_func, *memchr_func;
361 Constant *strcpy_func, *strlen_func;
362 Constant *floorf_func, *ceilf_func, *roundf_func;
363 Constant *rintf_func, *nearbyintf_func;
364 Module *M; ///< Cached Module
365 TargetData *TD; ///< Cached TargetData
369 RegisterPass<SimplifyLibCalls>
370 X("simplify-libcalls", "Simplify well-known library calls");
372 } // anonymous namespace
374 // The only public symbol in this file which just instantiates the pass object
375 ModulePass *llvm::createSimplifyLibCallsPass() {
376 return new SimplifyLibCalls();
379 // Classes below here, in the anonymous namespace, are all subclasses of the
380 // LibCallOptimization class, each implementing all optimizations possible for a
381 // single well-known library call. Each has a static singleton instance that
382 // auto registers it into the "optlist" global above.
385 // Forward declare utility functions.
386 bool getConstantStringLength(Value* V, uint64_t& len, ConstantArray** A = 0 );
387 Value *CastToCStr(Value *V, Instruction &IP);
389 /// This LibCallOptimization will find instances of a call to "exit" that occurs
390 /// within the "main" function and change it to a simple "ret" instruction with
391 /// the same value passed to the exit function. When this is done, it splits the
392 /// basic block at the exit(3) call and deletes the call instruction.
393 /// @brief Replace calls to exit in main with a simple return
394 struct ExitInMainOptimization : public LibCallOptimization {
395 ExitInMainOptimization() : LibCallOptimization("exit",
396 "Number of 'exit' calls simplified") {}
398 // Make sure the called function looks like exit (int argument, int return
399 // type, external linkage, not varargs).
400 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
401 return F->arg_size() >= 1 && F->arg_begin()->getType()->isInteger();
404 virtual bool OptimizeCall(CallInst* ci, SimplifyLibCalls& SLC) {
405 // To be careful, we check that the call to exit is coming from "main", that
406 // main has external linkage, and the return type of main and the argument
407 // to exit have the same type.
408 Function *from = ci->getParent()->getParent();
409 if (from->hasExternalLinkage())
410 if (from->getReturnType() == ci->getOperand(1)->getType())
411 if (from->getName() == "main") {
412 // Okay, time to actually do the optimization. First, get the basic
413 // block of the call instruction
414 BasicBlock* bb = ci->getParent();
416 // Create a return instruction that we'll replace the call with.
417 // Note that the argument of the return is the argument of the call
419 new ReturnInst(ci->getOperand(1), ci);
421 // Split the block at the call instruction which places it in a new
423 bb->splitBasicBlock(ci);
425 // The block split caused a branch instruction to be inserted into
426 // the end of the original block, right after the return instruction
427 // that we put there. That's not a valid block, so delete the branch
429 bb->getInstList().pop_back();
431 // Now we can finally get rid of the call instruction which now lives
432 // in the new basic block.
433 ci->eraseFromParent();
435 // Optimization succeeded, return true.
438 // We didn't pass the criteria for this optimization so return false
441 } ExitInMainOptimizer;
443 /// This LibCallOptimization will simplify a call to the strcat library
444 /// function. The simplification is possible only if the string being
445 /// concatenated is a constant array or a constant expression that results in
446 /// a constant string. In this case we can replace it with strlen + llvm.memcpy
447 /// of the constant string. Both of these calls are further reduced, if possible
448 /// on subsequent passes.
449 /// @brief Simplify the strcat library function.
450 struct StrCatOptimization : public LibCallOptimization {
452 /// @brief Default constructor
453 StrCatOptimization() : LibCallOptimization("strcat",
454 "Number of 'strcat' calls simplified") {}
458 /// @brief Make sure that the "strcat" function has the right prototype
459 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC){
460 if (f->getReturnType() == PointerType::get(Type::Int8Ty))
461 if (f->arg_size() == 2)
463 Function::const_arg_iterator AI = f->arg_begin();
464 if (AI++->getType() == PointerType::get(Type::Int8Ty))
465 if (AI->getType() == PointerType::get(Type::Int8Ty))
467 // Indicate this is a suitable call type.
474 /// @brief Optimize the strcat library function
475 virtual bool OptimizeCall(CallInst* ci, SimplifyLibCalls& SLC) {
476 // Extract some information from the instruction
477 Value* dest = ci->getOperand(1);
478 Value* src = ci->getOperand(2);
480 // Extract the initializer (while making numerous checks) from the
481 // source operand of the call to strcat. If we get null back, one of
482 // a variety of checks in get_GVInitializer failed
484 if (!getConstantStringLength(src,len))
487 // Handle the simple, do-nothing case
489 ci->replaceAllUsesWith(dest);
490 ci->eraseFromParent();
494 // Increment the length because we actually want to memcpy the null
495 // terminator as well.
498 // We need to find the end of the destination string. That's where the
499 // memory is to be moved to. We just generate a call to strlen (further
500 // optimized in another pass). Note that the SLC.get_strlen() call
501 // caches the Function* for us.
502 CallInst* strlen_inst =
503 new CallInst(SLC.get_strlen(), dest, dest->getName()+".len",ci);
505 // Now that we have the destination's length, we must index into the
506 // destination's pointer to get the actual memcpy destination (end of
507 // the string .. we're concatenating).
508 std::vector<Value*> idx;
509 idx.push_back(strlen_inst);
510 GetElementPtrInst* gep =
511 new GetElementPtrInst(dest,idx,dest->getName()+".indexed",ci);
513 // We have enough information to now generate the memcpy call to
514 // do the concatenation for us.
515 std::vector<Value*> vals;
516 vals.push_back(gep); // destination
517 vals.push_back(ci->getOperand(2)); // source
518 vals.push_back(ConstantInt::get(SLC.getIntPtrType(),len)); // length
519 vals.push_back(ConstantInt::get(Type::Int32Ty,1)); // alignment
520 new CallInst(SLC.get_memcpy(), vals, "", ci);
522 // Finally, substitute the first operand of the strcat call for the
523 // strcat call itself since strcat returns its first operand; and,
524 // kill the strcat CallInst.
525 ci->replaceAllUsesWith(dest);
526 ci->eraseFromParent();
531 /// This LibCallOptimization will simplify a call to the strchr library
532 /// function. It optimizes out cases where the arguments are both constant
533 /// and the result can be determined statically.
534 /// @brief Simplify the strcmp library function.
535 struct StrChrOptimization : public LibCallOptimization {
537 StrChrOptimization() : LibCallOptimization("strchr",
538 "Number of 'strchr' calls simplified") {}
540 /// @brief Make sure that the "strchr" function has the right prototype
541 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC){
542 if (f->getReturnType() == PointerType::get(Type::Int8Ty) &&
548 /// @brief Perform the strchr optimizations
549 virtual bool OptimizeCall(CallInst *ci, SimplifyLibCalls &SLC) {
550 // If there aren't three operands, bail
551 if (ci->getNumOperands() != 3)
554 // Check that the first argument to strchr is a constant array of sbyte.
555 // If it is, get the length and data, otherwise return false.
557 ConstantArray* CA = 0;
558 if (!getConstantStringLength(ci->getOperand(1), len, &CA))
561 // Check that the second argument to strchr is a constant int. If it isn't
562 // a constant signed integer, we can try an alternate optimization
563 ConstantInt* CSI = dyn_cast<ConstantInt>(ci->getOperand(2));
565 // The second operand is not constant, or not signed. Just lower this to
566 // memchr since we know the length of the string since it is constant.
567 Constant *f = SLC.get_memchr();
568 std::vector<Value*> args;
569 args.push_back(ci->getOperand(1));
570 args.push_back(ci->getOperand(2));
571 args.push_back(ConstantInt::get(SLC.getIntPtrType(), len));
572 ci->replaceAllUsesWith(new CallInst(f, args, ci->getName(), ci));
573 ci->eraseFromParent();
577 // Get the character we're looking for
578 int64_t chr = CSI->getSExtValue();
580 // Compute the offset
582 bool char_found = false;
583 for (uint64_t i = 0; i < len; ++i) {
584 if (ConstantInt* CI = dyn_cast<ConstantInt>(CA->getOperand(i))) {
585 // Check for the null terminator
586 if (CI->isNullValue())
587 break; // we found end of string
588 else if (CI->getSExtValue() == chr) {
596 // strchr(s,c) -> offset_of_in(c,s)
597 // (if c is a constant integer and s is a constant string)
599 std::vector<Value*> indices;
600 indices.push_back(ConstantInt::get(Type::Int64Ty,offset));
601 GetElementPtrInst* GEP = new GetElementPtrInst(ci->getOperand(1),indices,
602 ci->getOperand(1)->getName()+".strchr",ci);
603 ci->replaceAllUsesWith(GEP);
605 ci->replaceAllUsesWith(
606 ConstantPointerNull::get(PointerType::get(Type::Int8Ty)));
608 ci->eraseFromParent();
613 /// This LibCallOptimization will simplify a call to the strcmp library
614 /// function. It optimizes out cases where one or both arguments are constant
615 /// and the result can be determined statically.
616 /// @brief Simplify the strcmp library function.
617 struct StrCmpOptimization : public LibCallOptimization {
619 StrCmpOptimization() : LibCallOptimization("strcmp",
620 "Number of 'strcmp' calls simplified") {}
622 /// @brief Make sure that the "strcmp" function has the right prototype
623 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
624 return F->getReturnType() == Type::Int32Ty && F->arg_size() == 2;
627 /// @brief Perform the strcmp optimization
628 virtual bool OptimizeCall(CallInst* ci, SimplifyLibCalls& SLC) {
629 // First, check to see if src and destination are the same. If they are,
630 // then the optimization is to replace the CallInst with a constant 0
631 // because the call is a no-op.
632 Value* s1 = ci->getOperand(1);
633 Value* s2 = ci->getOperand(2);
636 ci->replaceAllUsesWith(ConstantInt::get(Type::Int32Ty,0));
637 ci->eraseFromParent();
641 bool isstr_1 = false;
644 if (getConstantStringLength(s1,len_1,&A1)) {
647 // strcmp("",x) -> *x
649 new LoadInst(CastToCStr(s2,*ci), ci->getName()+".load",ci);
651 CastInst::create(Instruction::SExt, load, Type::Int32Ty,
652 ci->getName()+".int", ci);
653 ci->replaceAllUsesWith(cast);
654 ci->eraseFromParent();
659 bool isstr_2 = false;
662 if (getConstantStringLength(s2, len_2, &A2)) {
665 // strcmp(x,"") -> *x
667 new LoadInst(CastToCStr(s1,*ci),ci->getName()+".val",ci);
669 CastInst::create(Instruction::SExt, load, Type::Int32Ty,
670 ci->getName()+".int", ci);
671 ci->replaceAllUsesWith(cast);
672 ci->eraseFromParent();
677 if (isstr_1 && isstr_2) {
678 // strcmp(x,y) -> cnst (if both x and y are constant strings)
679 std::string str1 = A1->getAsString();
680 std::string str2 = A2->getAsString();
681 int result = strcmp(str1.c_str(), str2.c_str());
682 ci->replaceAllUsesWith(ConstantInt::get(Type::Int32Ty,result));
683 ci->eraseFromParent();
690 /// This LibCallOptimization will simplify a call to the strncmp library
691 /// function. It optimizes out cases where one or both arguments are constant
692 /// and the result can be determined statically.
693 /// @brief Simplify the strncmp library function.
694 struct StrNCmpOptimization : public LibCallOptimization {
696 StrNCmpOptimization() : LibCallOptimization("strncmp",
697 "Number of 'strncmp' calls simplified") {}
699 /// @brief Make sure that the "strncmp" function has the right prototype
700 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC){
701 if (f->getReturnType() == Type::Int32Ty && f->arg_size() == 3)
706 /// @brief Perform the strncpy optimization
707 virtual bool OptimizeCall(CallInst *ci, SimplifyLibCalls &SLC) {
708 // First, check to see if src and destination are the same. If they are,
709 // then the optimization is to replace the CallInst with a constant 0
710 // because the call is a no-op.
711 Value* s1 = ci->getOperand(1);
712 Value* s2 = ci->getOperand(2);
714 // strncmp(x,x,l) -> 0
715 ci->replaceAllUsesWith(ConstantInt::get(Type::Int32Ty,0));
716 ci->eraseFromParent();
720 // Check the length argument, if it is Constant zero then the strings are
722 uint64_t len_arg = 0;
723 bool len_arg_is_const = false;
724 if (ConstantInt* len_CI = dyn_cast<ConstantInt>(ci->getOperand(3))) {
725 len_arg_is_const = true;
726 len_arg = len_CI->getZExtValue();
728 // strncmp(x,y,0) -> 0
729 ci->replaceAllUsesWith(ConstantInt::get(Type::Int32Ty,0));
730 ci->eraseFromParent();
735 bool isstr_1 = false;
738 if (getConstantStringLength(s1, len_1, &A1)) {
741 // strncmp("",x) -> *x
742 LoadInst* load = new LoadInst(s1,ci->getName()+".load",ci);
744 CastInst::create(Instruction::SExt, load, Type::Int32Ty,
745 ci->getName()+".int", ci);
746 ci->replaceAllUsesWith(cast);
747 ci->eraseFromParent();
752 bool isstr_2 = false;
755 if (getConstantStringLength(s2,len_2,&A2)) {
758 // strncmp(x,"") -> *x
759 LoadInst* load = new LoadInst(s2,ci->getName()+".val",ci);
761 CastInst::create(Instruction::SExt, load, Type::Int32Ty,
762 ci->getName()+".int", ci);
763 ci->replaceAllUsesWith(cast);
764 ci->eraseFromParent();
769 if (isstr_1 && isstr_2 && len_arg_is_const) {
770 // strncmp(x,y,const) -> constant
771 std::string str1 = A1->getAsString();
772 std::string str2 = A2->getAsString();
773 int result = strncmp(str1.c_str(), str2.c_str(), len_arg);
774 ci->replaceAllUsesWith(ConstantInt::get(Type::Int32Ty,result));
775 ci->eraseFromParent();
782 /// This LibCallOptimization will simplify a call to the strcpy library
783 /// function. Two optimizations are possible:
784 /// (1) If src and dest are the same and not volatile, just return dest
785 /// (2) If the src is a constant then we can convert to llvm.memmove
786 /// @brief Simplify the strcpy library function.
787 struct StrCpyOptimization : public LibCallOptimization {
789 StrCpyOptimization() : LibCallOptimization("strcpy",
790 "Number of 'strcpy' calls simplified") {}
792 /// @brief Make sure that the "strcpy" function has the right prototype
793 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC){
794 if (f->getReturnType() == PointerType::get(Type::Int8Ty))
795 if (f->arg_size() == 2) {
796 Function::const_arg_iterator AI = f->arg_begin();
797 if (AI++->getType() == PointerType::get(Type::Int8Ty))
798 if (AI->getType() == PointerType::get(Type::Int8Ty)) {
799 // Indicate this is a suitable call type.
806 /// @brief Perform the strcpy optimization
807 virtual bool OptimizeCall(CallInst* ci, SimplifyLibCalls& SLC) {
808 // First, check to see if src and destination are the same. If they are,
809 // then the optimization is to replace the CallInst with the destination
810 // because the call is a no-op. Note that this corresponds to the
811 // degenerate strcpy(X,X) case which should have "undefined" results
812 // according to the C specification. However, it occurs sometimes and
813 // we optimize it as a no-op.
814 Value* dest = ci->getOperand(1);
815 Value* src = ci->getOperand(2);
817 ci->replaceAllUsesWith(dest);
818 ci->eraseFromParent();
822 // Get the length of the constant string referenced by the second operand,
823 // the "src" parameter. Fail the optimization if we can't get the length
824 // (note that getConstantStringLength does lots of checks to make sure this
827 if (!getConstantStringLength(ci->getOperand(2),len))
830 // If the constant string's length is zero we can optimize this by just
831 // doing a store of 0 at the first byte of the destination
833 new StoreInst(ConstantInt::get(Type::Int8Ty,0),ci->getOperand(1),ci);
834 ci->replaceAllUsesWith(dest);
835 ci->eraseFromParent();
839 // Increment the length because we actually want to memcpy the null
840 // terminator as well.
843 // We have enough information to now generate the memcpy call to
844 // do the concatenation for us.
845 std::vector<Value*> vals;
846 vals.push_back(dest); // destination
847 vals.push_back(src); // source
848 vals.push_back(ConstantInt::get(SLC.getIntPtrType(),len)); // length
849 vals.push_back(ConstantInt::get(Type::Int32Ty,1)); // alignment
850 new CallInst(SLC.get_memcpy(), vals, "", ci);
852 // Finally, substitute the first operand of the strcat call for the
853 // strcat call itself since strcat returns its first operand; and,
854 // kill the strcat CallInst.
855 ci->replaceAllUsesWith(dest);
856 ci->eraseFromParent();
861 /// This LibCallOptimization will simplify a call to the strlen library
862 /// function by replacing it with a constant value if the string provided to
863 /// it is a constant array.
864 /// @brief Simplify the strlen library function.
865 struct StrLenOptimization : public LibCallOptimization {
866 StrLenOptimization() : LibCallOptimization("strlen",
867 "Number of 'strlen' calls simplified") {}
869 /// @brief Make sure that the "strlen" function has the right prototype
870 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC)
872 if (f->getReturnType() == SLC.getTargetData()->getIntPtrType())
873 if (f->arg_size() == 1)
874 if (Function::const_arg_iterator AI = f->arg_begin())
875 if (AI->getType() == PointerType::get(Type::Int8Ty))
880 /// @brief Perform the strlen optimization
881 virtual bool OptimizeCall(CallInst* ci, SimplifyLibCalls& SLC)
883 // Make sure we're dealing with an sbyte* here.
884 Value* str = ci->getOperand(1);
885 if (str->getType() != PointerType::get(Type::Int8Ty))
888 // Does the call to strlen have exactly one use?
890 // Is that single use a icmp operator?
891 if (ICmpInst* bop = dyn_cast<ICmpInst>(ci->use_back()))
892 // Is it compared against a constant integer?
893 if (ConstantInt* CI = dyn_cast<ConstantInt>(bop->getOperand(1)))
895 // Get the value the strlen result is compared to
896 uint64_t val = CI->getZExtValue();
898 // If its compared against length 0 with == or !=
900 (bop->getPredicate() == ICmpInst::ICMP_EQ ||
901 bop->getPredicate() == ICmpInst::ICMP_NE))
903 // strlen(x) != 0 -> *x != 0
904 // strlen(x) == 0 -> *x == 0
905 LoadInst* load = new LoadInst(str,str->getName()+".first",ci);
906 ICmpInst* rbop = new ICmpInst(bop->getPredicate(), load,
907 ConstantInt::get(Type::Int8Ty,0),
908 bop->getName()+".strlen", ci);
909 bop->replaceAllUsesWith(rbop);
910 bop->eraseFromParent();
911 ci->eraseFromParent();
916 // Get the length of the constant string operand
918 if (!getConstantStringLength(ci->getOperand(1),len))
921 // strlen("xyz") -> 3 (for example)
922 const Type *Ty = SLC.getTargetData()->getIntPtrType();
923 ci->replaceAllUsesWith(ConstantInt::get(Ty, len));
925 ci->eraseFromParent();
930 /// IsOnlyUsedInEqualsComparison - Return true if it only matters that the value
931 /// is equal or not-equal to zero.
932 static bool IsOnlyUsedInEqualsZeroComparison(Instruction *I) {
933 for (Value::use_iterator UI = I->use_begin(), E = I->use_end();
935 Instruction *User = cast<Instruction>(*UI);
936 if (ICmpInst *IC = dyn_cast<ICmpInst>(User)) {
937 if ((IC->getPredicate() == ICmpInst::ICMP_NE ||
938 IC->getPredicate() == ICmpInst::ICMP_EQ) &&
939 isa<Constant>(IC->getOperand(1)) &&
940 cast<Constant>(IC->getOperand(1))->isNullValue())
942 } else if (CastInst *CI = dyn_cast<CastInst>(User))
943 if (CI->getType() == Type::Int1Ty)
945 // Unknown instruction.
951 /// This memcmpOptimization will simplify a call to the memcmp library
953 struct memcmpOptimization : public LibCallOptimization {
954 /// @brief Default Constructor
956 : LibCallOptimization("memcmp", "Number of 'memcmp' calls simplified") {}
958 /// @brief Make sure that the "memcmp" function has the right prototype
959 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &TD) {
960 Function::const_arg_iterator AI = F->arg_begin();
961 if (F->arg_size() != 3 || !isa<PointerType>(AI->getType())) return false;
962 if (!isa<PointerType>((++AI)->getType())) return false;
963 if (!(++AI)->getType()->isInteger()) return false;
964 if (!F->getReturnType()->isInteger()) return false;
968 /// Because of alignment and instruction information that we don't have, we
969 /// leave the bulk of this to the code generators.
971 /// Note that we could do much more if we could force alignment on otherwise
972 /// small aligned allocas, or if we could indicate that loads have a small
974 virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &TD) {
975 Value *LHS = CI->getOperand(1), *RHS = CI->getOperand(2);
977 // If the two operands are the same, return zero.
979 // memcmp(s,s,x) -> 0
980 CI->replaceAllUsesWith(Constant::getNullValue(CI->getType()));
981 CI->eraseFromParent();
985 // Make sure we have a constant length.
986 ConstantInt *LenC = dyn_cast<ConstantInt>(CI->getOperand(3));
987 if (!LenC) return false;
988 uint64_t Len = LenC->getZExtValue();
990 // If the length is zero, this returns 0.
993 // memcmp(s1,s2,0) -> 0
994 CI->replaceAllUsesWith(Constant::getNullValue(CI->getType()));
995 CI->eraseFromParent();
998 // memcmp(S1,S2,1) -> *(ubyte*)S1 - *(ubyte*)S2
999 const Type *UCharPtr = PointerType::get(Type::Int8Ty);
1000 CastInst *Op1Cast = CastInst::create(
1001 Instruction::BitCast, LHS, UCharPtr, LHS->getName(), CI);
1002 CastInst *Op2Cast = CastInst::create(
1003 Instruction::BitCast, RHS, UCharPtr, RHS->getName(), CI);
1004 Value *S1V = new LoadInst(Op1Cast, LHS->getName()+".val", CI);
1005 Value *S2V = new LoadInst(Op2Cast, RHS->getName()+".val", CI);
1006 Value *RV = BinaryOperator::createSub(S1V, S2V, CI->getName()+".diff",CI);
1007 if (RV->getType() != CI->getType())
1008 RV = CastInst::createIntegerCast(RV, CI->getType(), false,
1010 CI->replaceAllUsesWith(RV);
1011 CI->eraseFromParent();
1015 if (IsOnlyUsedInEqualsZeroComparison(CI)) {
1016 // TODO: IF both are aligned, use a short load/compare.
1018 // memcmp(S1,S2,2) -> S1[0]-S2[0] | S1[1]-S2[1] iff only ==/!= 0 matters
1019 const Type *UCharPtr = PointerType::get(Type::Int8Ty);
1020 CastInst *Op1Cast = CastInst::create(
1021 Instruction::BitCast, LHS, UCharPtr, LHS->getName(), CI);
1022 CastInst *Op2Cast = CastInst::create(
1023 Instruction::BitCast, RHS, UCharPtr, RHS->getName(), CI);
1024 Value *S1V1 = new LoadInst(Op1Cast, LHS->getName()+".val1", CI);
1025 Value *S2V1 = new LoadInst(Op2Cast, RHS->getName()+".val1", CI);
1026 Value *D1 = BinaryOperator::createSub(S1V1, S2V1,
1027 CI->getName()+".d1", CI);
1028 Constant *One = ConstantInt::get(Type::Int32Ty, 1);
1029 Value *G1 = new GetElementPtrInst(Op1Cast, One, "next1v", CI);
1030 Value *G2 = new GetElementPtrInst(Op2Cast, One, "next2v", CI);
1031 Value *S1V2 = new LoadInst(G1, LHS->getName()+".val2", CI);
1032 Value *S2V2 = new LoadInst(G2, RHS->getName()+".val2", CI);
1033 Value *D2 = BinaryOperator::createSub(S1V2, S2V2,
1034 CI->getName()+".d1", CI);
1035 Value *Or = BinaryOperator::createOr(D1, D2, CI->getName()+".res", CI);
1036 if (Or->getType() != CI->getType())
1037 Or = CastInst::createIntegerCast(Or, CI->getType(), false /*ZExt*/,
1039 CI->replaceAllUsesWith(Or);
1040 CI->eraseFromParent();
1053 /// This LibCallOptimization will simplify a call to the memcpy library
1054 /// function by expanding it out to a single store of size 0, 1, 2, 4, or 8
1055 /// bytes depending on the length of the string and the alignment. Additional
1056 /// optimizations are possible in code generation (sequence of immediate store)
1057 /// @brief Simplify the memcpy library function.
1058 struct LLVMMemCpyMoveOptzn : public LibCallOptimization {
1059 LLVMMemCpyMoveOptzn(const char* fname, const char* desc)
1060 : LibCallOptimization(fname, desc) {}
1062 /// @brief Make sure that the "memcpy" function has the right prototype
1063 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& TD) {
1064 // Just make sure this has 4 arguments per LLVM spec.
1065 return (f->arg_size() == 4);
1068 /// Because of alignment and instruction information that we don't have, we
1069 /// leave the bulk of this to the code generators. The optimization here just
1070 /// deals with a few degenerate cases where the length of the string and the
1071 /// alignment match the sizes of our intrinsic types so we can do a load and
1072 /// store instead of the memcpy call.
1073 /// @brief Perform the memcpy optimization.
1074 virtual bool OptimizeCall(CallInst* ci, SimplifyLibCalls& TD) {
1075 // Make sure we have constant int values to work with
1076 ConstantInt* LEN = dyn_cast<ConstantInt>(ci->getOperand(3));
1079 ConstantInt* ALIGN = dyn_cast<ConstantInt>(ci->getOperand(4));
1083 // If the length is larger than the alignment, we can't optimize
1084 uint64_t len = LEN->getZExtValue();
1085 uint64_t alignment = ALIGN->getZExtValue();
1087 alignment = 1; // Alignment 0 is identity for alignment 1
1088 if (len > alignment)
1091 // Get the type we will cast to, based on size of the string
1092 Value* dest = ci->getOperand(1);
1093 Value* src = ci->getOperand(2);
1094 const Type* castType = 0;
1098 // memcpy(d,s,0,a) -> noop
1099 ci->eraseFromParent();
1101 case 1: castType = Type::Int8Ty; break;
1102 case 2: castType = Type::Int16Ty; break;
1103 case 4: castType = Type::Int32Ty; break;
1104 case 8: castType = Type::Int64Ty; break;
1109 // Cast source and dest to the right sized primitive and then load/store
1110 CastInst* SrcCast = CastInst::create(Instruction::BitCast,
1111 src, PointerType::get(castType), src->getName()+".cast", ci);
1112 CastInst* DestCast = CastInst::create(Instruction::BitCast,
1113 dest, PointerType::get(castType),dest->getName()+".cast", ci);
1114 LoadInst* LI = new LoadInst(SrcCast,SrcCast->getName()+".val",ci);
1115 new StoreInst(LI, DestCast, ci);
1116 ci->eraseFromParent();
1121 /// This LibCallOptimization will simplify a call to the memcpy/memmove library
1123 LLVMMemCpyMoveOptzn LLVMMemCpyOptimizer32("llvm.memcpy.i32",
1124 "Number of 'llvm.memcpy' calls simplified");
1125 LLVMMemCpyMoveOptzn LLVMMemCpyOptimizer64("llvm.memcpy.i64",
1126 "Number of 'llvm.memcpy' calls simplified");
1127 LLVMMemCpyMoveOptzn LLVMMemMoveOptimizer32("llvm.memmove.i32",
1128 "Number of 'llvm.memmove' calls simplified");
1129 LLVMMemCpyMoveOptzn LLVMMemMoveOptimizer64("llvm.memmove.i64",
1130 "Number of 'llvm.memmove' calls simplified");
1132 /// This LibCallOptimization will simplify a call to the memset library
1133 /// function by expanding it out to a single store of size 0, 1, 2, 4, or 8
1134 /// bytes depending on the length argument.
1135 struct LLVMMemSetOptimization : public LibCallOptimization {
1136 /// @brief Default Constructor
1137 LLVMMemSetOptimization(const char *Name) : LibCallOptimization(Name,
1138 "Number of 'llvm.memset' calls simplified") {}
1140 /// @brief Make sure that the "memset" function has the right prototype
1141 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &TD) {
1142 // Just make sure this has 3 arguments per LLVM spec.
1143 return F->arg_size() == 4;
1146 /// Because of alignment and instruction information that we don't have, we
1147 /// leave the bulk of this to the code generators. The optimization here just
1148 /// deals with a few degenerate cases where the length parameter is constant
1149 /// and the alignment matches the sizes of our intrinsic types so we can do
1150 /// store instead of the memcpy call. Other calls are transformed into the
1151 /// llvm.memset intrinsic.
1152 /// @brief Perform the memset optimization.
1153 virtual bool OptimizeCall(CallInst *ci, SimplifyLibCalls &TD) {
1154 // Make sure we have constant int values to work with
1155 ConstantInt* LEN = dyn_cast<ConstantInt>(ci->getOperand(3));
1158 ConstantInt* ALIGN = dyn_cast<ConstantInt>(ci->getOperand(4));
1162 // Extract the length and alignment
1163 uint64_t len = LEN->getZExtValue();
1164 uint64_t alignment = ALIGN->getZExtValue();
1166 // Alignment 0 is identity for alignment 1
1170 // If the length is zero, this is a no-op
1172 // memset(d,c,0,a) -> noop
1173 ci->eraseFromParent();
1177 // If the length is larger than the alignment, we can't optimize
1178 if (len > alignment)
1181 // Make sure we have a constant ubyte to work with so we can extract
1182 // the value to be filled.
1183 ConstantInt* FILL = dyn_cast<ConstantInt>(ci->getOperand(2));
1186 if (FILL->getType() != Type::Int8Ty)
1189 // memset(s,c,n) -> store s, c (for n=1,2,4,8)
1191 // Extract the fill character
1192 uint64_t fill_char = FILL->getZExtValue();
1193 uint64_t fill_value = fill_char;
1195 // Get the type we will cast to, based on size of memory area to fill, and
1196 // and the value we will store there.
1197 Value* dest = ci->getOperand(1);
1198 const Type* castType = 0;
1201 castType = Type::Int8Ty;
1204 castType = Type::Int16Ty;
1205 fill_value |= fill_char << 8;
1208 castType = Type::Int32Ty;
1209 fill_value |= fill_char << 8 | fill_char << 16 | fill_char << 24;
1212 castType = Type::Int64Ty;
1213 fill_value |= fill_char << 8 | fill_char << 16 | fill_char << 24;
1214 fill_value |= fill_char << 32 | fill_char << 40 | fill_char << 48;
1215 fill_value |= fill_char << 56;
1221 // Cast dest to the right sized primitive and then load/store
1222 CastInst* DestCast = new BitCastInst(dest, PointerType::get(castType),
1223 dest->getName()+".cast", ci);
1224 new StoreInst(ConstantInt::get(castType,fill_value),DestCast, ci);
1225 ci->eraseFromParent();
1230 LLVMMemSetOptimization MemSet32Optimizer("llvm.memset.i32");
1231 LLVMMemSetOptimization MemSet64Optimizer("llvm.memset.i64");
1234 /// This LibCallOptimization will simplify calls to the "pow" library
1235 /// function. It looks for cases where the result of pow is well known and
1236 /// substitutes the appropriate value.
1237 /// @brief Simplify the pow library function.
1238 struct PowOptimization : public LibCallOptimization {
1240 /// @brief Default Constructor
1241 PowOptimization() : LibCallOptimization("pow",
1242 "Number of 'pow' calls simplified") {}
1244 /// @brief Make sure that the "pow" function has the right prototype
1245 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC){
1246 // Just make sure this has 2 arguments
1247 return (f->arg_size() == 2);
1250 /// @brief Perform the pow optimization.
1251 virtual bool OptimizeCall(CallInst *ci, SimplifyLibCalls &SLC) {
1252 const Type *Ty = cast<Function>(ci->getOperand(0))->getReturnType();
1253 Value* base = ci->getOperand(1);
1254 Value* expn = ci->getOperand(2);
1255 if (ConstantFP *Op1 = dyn_cast<ConstantFP>(base)) {
1256 double Op1V = Op1->getValue();
1258 // pow(1.0,x) -> 1.0
1259 ci->replaceAllUsesWith(ConstantFP::get(Ty,1.0));
1260 ci->eraseFromParent();
1263 } else if (ConstantFP* Op2 = dyn_cast<ConstantFP>(expn)) {
1264 double Op2V = Op2->getValue();
1266 // pow(x,0.0) -> 1.0
1267 ci->replaceAllUsesWith(ConstantFP::get(Ty,1.0));
1268 ci->eraseFromParent();
1270 } else if (Op2V == 0.5) {
1271 // pow(x,0.5) -> sqrt(x)
1272 CallInst* sqrt_inst = new CallInst(SLC.get_sqrt(), base,
1273 ci->getName()+".pow",ci);
1274 ci->replaceAllUsesWith(sqrt_inst);
1275 ci->eraseFromParent();
1277 } else if (Op2V == 1.0) {
1279 ci->replaceAllUsesWith(base);
1280 ci->eraseFromParent();
1282 } else if (Op2V == -1.0) {
1283 // pow(x,-1.0) -> 1.0/x
1284 BinaryOperator* div_inst= BinaryOperator::createFDiv(
1285 ConstantFP::get(Ty,1.0), base, ci->getName()+".pow", ci);
1286 ci->replaceAllUsesWith(div_inst);
1287 ci->eraseFromParent();
1291 return false; // opt failed
1295 /// This LibCallOptimization will simplify calls to the "printf" library
1296 /// function. It looks for cases where the result of printf is not used and the
1297 /// operation can be reduced to something simpler.
1298 /// @brief Simplify the printf library function.
1299 struct PrintfOptimization : public LibCallOptimization {
1301 /// @brief Default Constructor
1302 PrintfOptimization() : LibCallOptimization("printf",
1303 "Number of 'printf' calls simplified") {}
1305 /// @brief Make sure that the "printf" function has the right prototype
1306 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC){
1307 // Just make sure this has at least 1 arguments
1308 return (f->arg_size() >= 1);
1311 /// @brief Perform the printf optimization.
1312 virtual bool OptimizeCall(CallInst* ci, SimplifyLibCalls& SLC) {
1313 // If the call has more than 2 operands, we can't optimize it
1314 if (ci->getNumOperands() > 3 || ci->getNumOperands() <= 2)
1317 // If the result of the printf call is used, none of these optimizations
1319 if (!ci->use_empty())
1322 // All the optimizations depend on the length of the first argument and the
1323 // fact that it is a constant string array. Check that now
1325 ConstantArray* CA = 0;
1326 if (!getConstantStringLength(ci->getOperand(1), len, &CA))
1329 if (len != 2 && len != 3)
1332 // The first character has to be a %
1333 if (ConstantInt* CI = dyn_cast<ConstantInt>(CA->getOperand(0)))
1334 if (CI->getZExtValue() != '%')
1337 // Get the second character and switch on its value
1338 ConstantInt* CI = dyn_cast<ConstantInt>(CA->getOperand(1));
1339 switch (CI->getZExtValue()) {
1343 dyn_cast<ConstantInt>(CA->getOperand(2))->getZExtValue() != '\n')
1346 // printf("%s\n",str) -> puts(str)
1347 std::vector<Value*> args;
1348 new CallInst(SLC.get_puts(), CastToCStr(ci->getOperand(2), *ci),
1350 ci->replaceAllUsesWith(ConstantInt::get(Type::Int32Ty, len));
1355 // printf("%c",c) -> putchar(c)
1359 CastInst *Char = CastInst::createSExtOrBitCast(
1360 ci->getOperand(2), Type::Int32Ty, CI->getName()+".int", ci);
1361 new CallInst(SLC.get_putchar(), Char, "", ci);
1362 ci->replaceAllUsesWith(ConstantInt::get(Type::Int32Ty, 1));
1368 ci->eraseFromParent();
1373 /// This LibCallOptimization will simplify calls to the "fprintf" library
1374 /// function. It looks for cases where the result of fprintf is not used and the
1375 /// operation can be reduced to something simpler.
1376 /// @brief Simplify the fprintf library function.
1377 struct FPrintFOptimization : public LibCallOptimization {
1379 /// @brief Default Constructor
1380 FPrintFOptimization() : LibCallOptimization("fprintf",
1381 "Number of 'fprintf' calls simplified") {}
1383 /// @brief Make sure that the "fprintf" function has the right prototype
1384 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC){
1385 // Just make sure this has at least 2 arguments
1386 return (f->arg_size() >= 2);
1389 /// @brief Perform the fprintf optimization.
1390 virtual bool OptimizeCall(CallInst* ci, SimplifyLibCalls& SLC) {
1391 // If the call has more than 3 operands, we can't optimize it
1392 if (ci->getNumOperands() > 4 || ci->getNumOperands() <= 2)
1395 // If the result of the fprintf call is used, none of these optimizations
1397 if (!ci->use_empty())
1400 // All the optimizations depend on the length of the second argument and the
1401 // fact that it is a constant string array. Check that now
1403 ConstantArray* CA = 0;
1404 if (!getConstantStringLength(ci->getOperand(2), len, &CA))
1407 if (ci->getNumOperands() == 3) {
1408 // Make sure there's no % in the constant array
1409 for (unsigned i = 0; i < len; ++i) {
1410 if (ConstantInt* CI = dyn_cast<ConstantInt>(CA->getOperand(i))) {
1411 // Check for the null terminator
1412 if (CI->getZExtValue() == '%')
1413 return false; // we found end of string
1419 // fprintf(file,fmt) -> fwrite(fmt,strlen(fmt),file)
1420 const Type* FILEptr_type = ci->getOperand(1)->getType();
1422 // Make sure that the fprintf() and fwrite() functions both take the
1423 // same type of char pointer.
1424 if (ci->getOperand(2)->getType() != PointerType::get(Type::Int8Ty))
1427 std::vector<Value*> args;
1428 args.push_back(ci->getOperand(2));
1429 args.push_back(ConstantInt::get(SLC.getIntPtrType(),len));
1430 args.push_back(ConstantInt::get(SLC.getIntPtrType(),1));
1431 args.push_back(ci->getOperand(1));
1432 new CallInst(SLC.get_fwrite(FILEptr_type), args, ci->getName(), ci);
1433 ci->replaceAllUsesWith(ConstantInt::get(Type::Int32Ty,len));
1434 ci->eraseFromParent();
1438 // The remaining optimizations require the format string to be length 2
1443 // The first character has to be a %
1444 if (ConstantInt* CI = dyn_cast<ConstantInt>(CA->getOperand(0)))
1445 if (CI->getZExtValue() != '%')
1448 // Get the second character and switch on its value
1449 ConstantInt* CI = dyn_cast<ConstantInt>(CA->getOperand(1));
1450 switch (CI->getZExtValue()) {
1454 ConstantArray* CA = 0;
1455 if (getConstantStringLength(ci->getOperand(3), len, &CA)) {
1456 // fprintf(file,"%s",str) -> fwrite(str,strlen(str),1,file)
1457 const Type* FILEptr_type = ci->getOperand(1)->getType();
1458 std::vector<Value*> args;
1459 args.push_back(CastToCStr(ci->getOperand(3), *ci));
1460 args.push_back(ConstantInt::get(SLC.getIntPtrType(), len));
1461 args.push_back(ConstantInt::get(SLC.getIntPtrType(), 1));
1462 args.push_back(ci->getOperand(1));
1463 new CallInst(SLC.get_fwrite(FILEptr_type), args, ci->getName(), ci);
1464 ci->replaceAllUsesWith(ConstantInt::get(Type::Int32Ty, len));
1466 // fprintf(file,"%s",str) -> fputs(str,file)
1467 const Type* FILEptr_type = ci->getOperand(1)->getType();
1468 new CallInst(SLC.get_fputs(FILEptr_type),
1469 CastToCStr(ci->getOperand(3), *ci),
1470 ci->getOperand(1), ci->getName(),ci);
1471 ci->replaceAllUsesWith(ConstantInt::get(Type::Int32Ty,len));
1477 // fprintf(file,"%c",c) -> fputc(c,file)
1478 const Type* FILEptr_type = ci->getOperand(1)->getType();
1479 CastInst* cast = CastInst::createSExtOrBitCast(
1480 ci->getOperand(3), Type::Int32Ty, CI->getName()+".int", ci);
1481 new CallInst(SLC.get_fputc(FILEptr_type), cast,ci->getOperand(1),"",ci);
1482 ci->replaceAllUsesWith(ConstantInt::get(Type::Int32Ty,1));
1488 ci->eraseFromParent();
1493 /// This LibCallOptimization will simplify calls to the "sprintf" library
1494 /// function. It looks for cases where the result of sprintf is not used and the
1495 /// operation can be reduced to something simpler.
1496 /// @brief Simplify the sprintf library function.
1497 struct SPrintFOptimization : public LibCallOptimization {
1499 /// @brief Default Constructor
1500 SPrintFOptimization() : LibCallOptimization("sprintf",
1501 "Number of 'sprintf' calls simplified") {}
1503 /// @brief Make sure that the "fprintf" function has the right prototype
1504 virtual bool ValidateCalledFunction(const Function *f, SimplifyLibCalls &SLC){
1505 // Just make sure this has at least 2 arguments
1506 return (f->getReturnType() == Type::Int32Ty && f->arg_size() >= 2);
1509 /// @brief Perform the sprintf optimization.
1510 virtual bool OptimizeCall(CallInst *ci, SimplifyLibCalls &SLC) {
1511 // If the call has more than 3 operands, we can't optimize it
1512 if (ci->getNumOperands() > 4 || ci->getNumOperands() < 3)
1515 // All the optimizations depend on the length of the second argument and the
1516 // fact that it is a constant string array. Check that now
1518 ConstantArray* CA = 0;
1519 if (!getConstantStringLength(ci->getOperand(2), len, &CA))
1522 if (ci->getNumOperands() == 3) {
1524 // If the length is 0, we just need to store a null byte
1525 new StoreInst(ConstantInt::get(Type::Int8Ty,0),ci->getOperand(1),ci);
1526 ci->replaceAllUsesWith(ConstantInt::get(Type::Int32Ty,0));
1527 ci->eraseFromParent();
1531 // Make sure there's no % in the constant array
1532 for (unsigned i = 0; i < len; ++i) {
1533 if (ConstantInt* CI = dyn_cast<ConstantInt>(CA->getOperand(i))) {
1534 // Check for the null terminator
1535 if (CI->getZExtValue() == '%')
1536 return false; // we found a %, can't optimize
1538 return false; // initializer is not constant int, can't optimize
1542 // Increment length because we want to copy the null byte too
1545 // sprintf(str,fmt) -> llvm.memcpy(str,fmt,strlen(fmt),1)
1546 std::vector<Value*> args;
1547 args.push_back(ci->getOperand(1));
1548 args.push_back(ci->getOperand(2));
1549 args.push_back(ConstantInt::get(SLC.getIntPtrType(),len));
1550 args.push_back(ConstantInt::get(Type::Int32Ty,1));
1551 new CallInst(SLC.get_memcpy(), args, "", ci);
1552 ci->replaceAllUsesWith(ConstantInt::get(Type::Int32Ty,len));
1553 ci->eraseFromParent();
1557 // The remaining optimizations require the format string to be length 2
1562 // The first character has to be a %
1563 if (ConstantInt* CI = dyn_cast<ConstantInt>(CA->getOperand(0)))
1564 if (CI->getZExtValue() != '%')
1567 // Get the second character and switch on its value
1568 ConstantInt* CI = dyn_cast<ConstantInt>(CA->getOperand(1));
1569 switch (CI->getZExtValue()) {
1571 // sprintf(dest,"%s",str) -> llvm.memcpy(dest, str, strlen(str)+1, 1)
1572 Value *Len = new CallInst(SLC.get_strlen(),
1573 CastToCStr(ci->getOperand(3), *ci),
1574 ci->getOperand(3)->getName()+".len", ci);
1575 Value *Len1 = BinaryOperator::createAdd(Len,
1576 ConstantInt::get(Len->getType(), 1),
1577 Len->getName()+"1", ci);
1578 if (Len1->getType() != SLC.getIntPtrType())
1579 Len1 = CastInst::createIntegerCast(Len1, SLC.getIntPtrType(), false,
1580 Len1->getName(), ci);
1581 std::vector<Value*> args;
1582 args.push_back(CastToCStr(ci->getOperand(1), *ci));
1583 args.push_back(CastToCStr(ci->getOperand(3), *ci));
1584 args.push_back(Len1);
1585 args.push_back(ConstantInt::get(Type::Int32Ty,1));
1586 new CallInst(SLC.get_memcpy(), args, "", ci);
1588 // The strlen result is the unincremented number of bytes in the string.
1589 if (!ci->use_empty()) {
1590 if (Len->getType() != ci->getType())
1591 Len = CastInst::createIntegerCast(Len, ci->getType(), false,
1592 Len->getName(), ci);
1593 ci->replaceAllUsesWith(Len);
1595 ci->eraseFromParent();
1599 // sprintf(dest,"%c",chr) -> store chr, dest
1600 CastInst* cast = CastInst::createTruncOrBitCast(
1601 ci->getOperand(3), Type::Int8Ty, "char", ci);
1602 new StoreInst(cast, ci->getOperand(1), ci);
1603 GetElementPtrInst* gep = new GetElementPtrInst(ci->getOperand(1),
1604 ConstantInt::get(Type::Int32Ty,1),ci->getOperand(1)->getName()+".end",
1606 new StoreInst(ConstantInt::get(Type::Int8Ty,0),gep,ci);
1607 ci->replaceAllUsesWith(ConstantInt::get(Type::Int32Ty,1));
1608 ci->eraseFromParent();
1616 /// This LibCallOptimization will simplify calls to the "fputs" library
1617 /// function. It looks for cases where the result of fputs is not used and the
1618 /// operation can be reduced to something simpler.
1619 /// @brief Simplify the puts library function.
1620 struct PutsOptimization : public LibCallOptimization {
1622 /// @brief Default Constructor
1623 PutsOptimization() : LibCallOptimization("fputs",
1624 "Number of 'fputs' calls simplified") {}
1626 /// @brief Make sure that the "fputs" function has the right prototype
1627 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
1628 // Just make sure this has 2 arguments
1629 return F->arg_size() == 2;
1632 /// @brief Perform the fputs optimization.
1633 virtual bool OptimizeCall(CallInst* ci, SimplifyLibCalls& SLC) {
1634 // If the result is used, none of these optimizations work
1635 if (!ci->use_empty())
1638 // All the optimizations depend on the length of the first argument and the
1639 // fact that it is a constant string array. Check that now
1641 if (!getConstantStringLength(ci->getOperand(1), len))
1646 // fputs("",F) -> noop
1650 // fputs(s,F) -> fputc(s[0],F) (if s is constant and strlen(s) == 1)
1651 const Type* FILEptr_type = ci->getOperand(2)->getType();
1652 LoadInst* loadi = new LoadInst(ci->getOperand(1),
1653 ci->getOperand(1)->getName()+".byte",ci);
1654 CastInst* casti = new SExtInst(loadi, Type::Int32Ty,
1655 loadi->getName()+".int", ci);
1656 new CallInst(SLC.get_fputc(FILEptr_type), casti,
1657 ci->getOperand(2), "", ci);
1662 // fputs(s,F) -> fwrite(s,1,len,F) (if s is constant and strlen(s) > 1)
1663 const Type* FILEptr_type = ci->getOperand(2)->getType();
1664 std::vector<Value*> parms;
1665 parms.push_back(ci->getOperand(1));
1666 parms.push_back(ConstantInt::get(SLC.getIntPtrType(),len));
1667 parms.push_back(ConstantInt::get(SLC.getIntPtrType(),1));
1668 parms.push_back(ci->getOperand(2));
1669 new CallInst(SLC.get_fwrite(FILEptr_type), parms, "", ci);
1673 ci->eraseFromParent();
1674 return true; // success
1678 /// This LibCallOptimization will simplify calls to the "isdigit" library
1679 /// function. It simply does range checks the parameter explicitly.
1680 /// @brief Simplify the isdigit library function.
1681 struct isdigitOptimization : public LibCallOptimization {
1683 isdigitOptimization() : LibCallOptimization("isdigit",
1684 "Number of 'isdigit' calls simplified") {}
1686 /// @brief Make sure that the "isdigit" function has the right prototype
1687 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC){
1688 // Just make sure this has 1 argument
1689 return (f->arg_size() == 1);
1692 /// @brief Perform the toascii optimization.
1693 virtual bool OptimizeCall(CallInst *ci, SimplifyLibCalls &SLC) {
1694 if (ConstantInt* CI = dyn_cast<ConstantInt>(ci->getOperand(1))) {
1695 // isdigit(c) -> 0 or 1, if 'c' is constant
1696 uint64_t val = CI->getZExtValue();
1697 if (val >= '0' && val <='9')
1698 ci->replaceAllUsesWith(ConstantInt::get(Type::Int32Ty,1));
1700 ci->replaceAllUsesWith(ConstantInt::get(Type::Int32Ty,0));
1701 ci->eraseFromParent();
1705 // isdigit(c) -> (unsigned)c - '0' <= 9
1706 CastInst* cast = CastInst::createIntegerCast(ci->getOperand(1),
1707 Type::Int32Ty, false/*ZExt*/, ci->getOperand(1)->getName()+".uint", ci);
1708 BinaryOperator* sub_inst = BinaryOperator::createSub(cast,
1709 ConstantInt::get(Type::Int32Ty,0x30),
1710 ci->getOperand(1)->getName()+".sub",ci);
1711 ICmpInst* setcond_inst = new ICmpInst(ICmpInst::ICMP_ULE,sub_inst,
1712 ConstantInt::get(Type::Int32Ty,9),
1713 ci->getOperand(1)->getName()+".cmp",ci);
1714 CastInst* c2 = new ZExtInst(setcond_inst, Type::Int32Ty,
1715 ci->getOperand(1)->getName()+".isdigit", ci);
1716 ci->replaceAllUsesWith(c2);
1717 ci->eraseFromParent();
1722 struct isasciiOptimization : public LibCallOptimization {
1724 isasciiOptimization()
1725 : LibCallOptimization("isascii", "Number of 'isascii' calls simplified") {}
1727 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
1728 return F->arg_size() == 1 && F->arg_begin()->getType()->isInteger() &&
1729 F->getReturnType()->isInteger();
1732 /// @brief Perform the isascii optimization.
1733 virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
1734 // isascii(c) -> (unsigned)c < 128
1735 Value *V = CI->getOperand(1);
1736 Value *Cmp = new ICmpInst(ICmpInst::ICMP_ULT, V,
1737 ConstantInt::get(V->getType(), 128),
1738 V->getName()+".isascii", CI);
1739 if (Cmp->getType() != CI->getType())
1740 Cmp = new BitCastInst(Cmp, CI->getType(), Cmp->getName(), CI);
1741 CI->replaceAllUsesWith(Cmp);
1742 CI->eraseFromParent();
1748 /// This LibCallOptimization will simplify calls to the "toascii" library
1749 /// function. It simply does the corresponding and operation to restrict the
1750 /// range of values to the ASCII character set (0-127).
1751 /// @brief Simplify the toascii library function.
1752 struct ToAsciiOptimization : public LibCallOptimization {
1754 /// @brief Default Constructor
1755 ToAsciiOptimization() : LibCallOptimization("toascii",
1756 "Number of 'toascii' calls simplified") {}
1758 /// @brief Make sure that the "fputs" function has the right prototype
1759 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC){
1760 // Just make sure this has 2 arguments
1761 return (f->arg_size() == 1);
1764 /// @brief Perform the toascii optimization.
1765 virtual bool OptimizeCall(CallInst *ci, SimplifyLibCalls &SLC) {
1766 // toascii(c) -> (c & 0x7f)
1767 Value* chr = ci->getOperand(1);
1768 BinaryOperator* and_inst = BinaryOperator::createAnd(chr,
1769 ConstantInt::get(chr->getType(),0x7F),ci->getName()+".toascii",ci);
1770 ci->replaceAllUsesWith(and_inst);
1771 ci->eraseFromParent();
1776 /// This LibCallOptimization will simplify calls to the "ffs" library
1777 /// calls which find the first set bit in an int, long, or long long. The
1778 /// optimization is to compute the result at compile time if the argument is
1780 /// @brief Simplify the ffs library function.
1781 struct FFSOptimization : public LibCallOptimization {
1783 /// @brief Subclass Constructor
1784 FFSOptimization(const char* funcName, const char* description)
1785 : LibCallOptimization(funcName, description) {}
1788 /// @brief Default Constructor
1789 FFSOptimization() : LibCallOptimization("ffs",
1790 "Number of 'ffs' calls simplified") {}
1792 /// @brief Make sure that the "ffs" function has the right prototype
1793 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
1794 // Just make sure this has 2 arguments
1795 return F->arg_size() == 1 && F->getReturnType() == Type::Int32Ty;
1798 /// @brief Perform the ffs optimization.
1799 virtual bool OptimizeCall(CallInst *TheCall, SimplifyLibCalls &SLC) {
1800 if (ConstantInt *CI = dyn_cast<ConstantInt>(TheCall->getOperand(1))) {
1801 // ffs(cnst) -> bit#
1802 // ffsl(cnst) -> bit#
1803 // ffsll(cnst) -> bit#
1804 uint64_t val = CI->getZExtValue();
1808 while ((val & 1) == 0) {
1813 TheCall->replaceAllUsesWith(ConstantInt::get(Type::Int32Ty, result));
1814 TheCall->eraseFromParent();
1818 // ffs(x) -> x == 0 ? 0 : llvm.cttz(x)+1
1819 // ffsl(x) -> x == 0 ? 0 : llvm.cttz(x)+1
1820 // ffsll(x) -> x == 0 ? 0 : llvm.cttz(x)+1
1821 const Type *ArgType = TheCall->getOperand(1)->getType();
1822 const char *CTTZName;
1823 assert(ArgType->getTypeID() == Type::IntegerTyID &&
1824 "llvm.cttz argument is not an integer?");
1825 unsigned BitWidth = cast<IntegerType>(ArgType)->getBitWidth();
1827 CTTZName = "llvm.cttz.i8";
1828 else if (BitWidth == 16)
1829 CTTZName = "llvm.cttz.i16";
1830 else if (BitWidth == 32)
1831 CTTZName = "llvm.cttz.i32";
1833 assert(BitWidth == 64 && "Unknown bitwidth");
1834 CTTZName = "llvm.cttz.i64";
1837 Constant *F = SLC.getModule()->getOrInsertFunction(CTTZName, ArgType,
1839 Value *V = CastInst::createIntegerCast(TheCall->getOperand(1), ArgType,
1840 false/*ZExt*/, "tmp", TheCall);
1841 Value *V2 = new CallInst(F, V, "tmp", TheCall);
1842 V2 = CastInst::createIntegerCast(V2, Type::Int32Ty, false/*ZExt*/,
1844 V2 = BinaryOperator::createAdd(V2, ConstantInt::get(Type::Int32Ty, 1),
1846 Value *Cond = new ICmpInst(ICmpInst::ICMP_EQ, V,
1847 Constant::getNullValue(V->getType()), "tmp",
1849 V2 = new SelectInst(Cond, ConstantInt::get(Type::Int32Ty, 0), V2,
1850 TheCall->getName(), TheCall);
1851 TheCall->replaceAllUsesWith(V2);
1852 TheCall->eraseFromParent();
1857 /// This LibCallOptimization will simplify calls to the "ffsl" library
1858 /// calls. It simply uses FFSOptimization for which the transformation is
1860 /// @brief Simplify the ffsl library function.
1861 struct FFSLOptimization : public FFSOptimization {
1863 /// @brief Default Constructor
1864 FFSLOptimization() : FFSOptimization("ffsl",
1865 "Number of 'ffsl' calls simplified") {}
1869 /// This LibCallOptimization will simplify calls to the "ffsll" library
1870 /// calls. It simply uses FFSOptimization for which the transformation is
1872 /// @brief Simplify the ffsl library function.
1873 struct FFSLLOptimization : public FFSOptimization {
1875 /// @brief Default Constructor
1876 FFSLLOptimization() : FFSOptimization("ffsll",
1877 "Number of 'ffsll' calls simplified") {}
1881 /// This optimizes unary functions that take and return doubles.
1882 struct UnaryDoubleFPOptimizer : public LibCallOptimization {
1883 UnaryDoubleFPOptimizer(const char *Fn, const char *Desc)
1884 : LibCallOptimization(Fn, Desc) {}
1886 // Make sure that this function has the right prototype
1887 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
1888 return F->arg_size() == 1 && F->arg_begin()->getType() == Type::DoubleTy &&
1889 F->getReturnType() == Type::DoubleTy;
1892 /// ShrinkFunctionToFloatVersion - If the input to this function is really a
1893 /// float, strength reduce this to a float version of the function,
1894 /// e.g. floor((double)FLT) -> (double)floorf(FLT). This can only be called
1895 /// when the target supports the destination function and where there can be
1896 /// no precision loss.
1897 static bool ShrinkFunctionToFloatVersion(CallInst *CI, SimplifyLibCalls &SLC,
1898 Constant *(SimplifyLibCalls::*FP)()){
1899 if (CastInst *Cast = dyn_cast<CastInst>(CI->getOperand(1)))
1900 if (Cast->getOperand(0)->getType() == Type::FloatTy) {
1901 Value *New = new CallInst((SLC.*FP)(), Cast->getOperand(0),
1903 New = new FPExtInst(New, Type::DoubleTy, CI->getName(), CI);
1904 CI->replaceAllUsesWith(New);
1905 CI->eraseFromParent();
1906 if (Cast->use_empty())
1907 Cast->eraseFromParent();
1915 struct FloorOptimization : public UnaryDoubleFPOptimizer {
1917 : UnaryDoubleFPOptimizer("floor", "Number of 'floor' calls simplified") {}
1919 virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
1921 // If this is a float argument passed in, convert to floorf.
1922 if (ShrinkFunctionToFloatVersion(CI, SLC, &SimplifyLibCalls::get_floorf))
1925 return false; // opt failed
1929 struct CeilOptimization : public UnaryDoubleFPOptimizer {
1931 : UnaryDoubleFPOptimizer("ceil", "Number of 'ceil' calls simplified") {}
1933 virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
1935 // If this is a float argument passed in, convert to ceilf.
1936 if (ShrinkFunctionToFloatVersion(CI, SLC, &SimplifyLibCalls::get_ceilf))
1939 return false; // opt failed
1943 struct RoundOptimization : public UnaryDoubleFPOptimizer {
1945 : UnaryDoubleFPOptimizer("round", "Number of 'round' calls simplified") {}
1947 virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
1949 // If this is a float argument passed in, convert to roundf.
1950 if (ShrinkFunctionToFloatVersion(CI, SLC, &SimplifyLibCalls::get_roundf))
1953 return false; // opt failed
1957 struct RintOptimization : public UnaryDoubleFPOptimizer {
1959 : UnaryDoubleFPOptimizer("rint", "Number of 'rint' calls simplified") {}
1961 virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
1963 // If this is a float argument passed in, convert to rintf.
1964 if (ShrinkFunctionToFloatVersion(CI, SLC, &SimplifyLibCalls::get_rintf))
1967 return false; // opt failed
1971 struct NearByIntOptimization : public UnaryDoubleFPOptimizer {
1972 NearByIntOptimization()
1973 : UnaryDoubleFPOptimizer("nearbyint",
1974 "Number of 'nearbyint' calls simplified") {}
1976 virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
1977 #ifdef HAVE_NEARBYINTF
1978 // If this is a float argument passed in, convert to nearbyintf.
1979 if (ShrinkFunctionToFloatVersion(CI, SLC,&SimplifyLibCalls::get_nearbyintf))
1982 return false; // opt failed
1984 } NearByIntOptimizer;
1986 /// A function to compute the length of a null-terminated constant array of
1987 /// integers. This function can't rely on the size of the constant array
1988 /// because there could be a null terminator in the middle of the array.
1989 /// We also have to bail out if we find a non-integer constant initializer
1990 /// of one of the elements or if there is no null-terminator. The logic
1991 /// below checks each of these conditions and will return true only if all
1992 /// conditions are met. In that case, the \p len parameter is set to the length
1993 /// of the null-terminated string. If false is returned, the conditions were
1994 /// not met and len is set to 0.
1995 /// @brief Get the length of a constant string (null-terminated array).
1996 bool getConstantStringLength(Value *V, uint64_t &len, ConstantArray **CA) {
1997 assert(V != 0 && "Invalid args to getConstantStringLength");
1998 len = 0; // make sure we initialize this
2000 // If the value is not a GEP instruction nor a constant expression with a
2001 // GEP instruction, then return false because ConstantArray can't occur
2003 if (GetElementPtrInst* GEPI = dyn_cast<GetElementPtrInst>(V))
2005 else if (ConstantExpr* CE = dyn_cast<ConstantExpr>(V))
2006 if (CE->getOpcode() == Instruction::GetElementPtr)
2013 // Make sure the GEP has exactly three arguments.
2014 if (GEP->getNumOperands() != 3)
2017 // Check to make sure that the first operand of the GEP is an integer and
2018 // has value 0 so that we are sure we're indexing into the initializer.
2019 if (ConstantInt* op1 = dyn_cast<ConstantInt>(GEP->getOperand(1))) {
2020 if (!op1->isNullValue())
2025 // Ensure that the second operand is a ConstantInt. If it isn't then this
2026 // GEP is wonky and we're not really sure what were referencing into and
2027 // better of not optimizing it. While we're at it, get the second index
2028 // value. We'll need this later for indexing the ConstantArray.
2029 uint64_t start_idx = 0;
2030 if (ConstantInt* CI = dyn_cast<ConstantInt>(GEP->getOperand(2)))
2031 start_idx = CI->getZExtValue();
2035 // The GEP instruction, constant or instruction, must reference a global
2036 // variable that is a constant and is initialized. The referenced constant
2037 // initializer is the array that we'll use for optimization.
2038 GlobalVariable* GV = dyn_cast<GlobalVariable>(GEP->getOperand(0));
2039 if (!GV || !GV->isConstant() || !GV->hasInitializer())
2042 // Get the initializer.
2043 Constant* INTLZR = GV->getInitializer();
2045 // Handle the ConstantAggregateZero case
2046 if (isa<ConstantAggregateZero>(INTLZR)) {
2047 // This is a degenerate case. The initializer is constant zero so the
2048 // length of the string must be zero.
2053 // Must be a Constant Array
2054 ConstantArray* A = dyn_cast<ConstantArray>(INTLZR);
2058 // Get the number of elements in the array
2059 uint64_t max_elems = A->getType()->getNumElements();
2061 // Traverse the constant array from start_idx (derived above) which is
2062 // the place the GEP refers to in the array.
2063 for (len = start_idx; len < max_elems; len++) {
2064 if (ConstantInt *CI = dyn_cast<ConstantInt>(A->getOperand(len))) {
2065 // Check for the null terminator
2066 if (CI->isNullValue())
2067 break; // we found end of string
2069 return false; // This array isn't suitable, non-int initializer
2072 if (len >= max_elems)
2073 return false; // This array isn't null terminated
2075 // Subtract out the initial value from the length
2079 return true; // success!
2082 /// CastToCStr - Return V if it is an sbyte*, otherwise cast it to sbyte*,
2083 /// inserting the cast before IP, and return the cast.
2084 /// @brief Cast a value to a "C" string.
2085 Value *CastToCStr(Value *V, Instruction &IP) {
2086 assert(isa<PointerType>(V->getType()) &&
2087 "Can't cast non-pointer type to C string type");
2088 const Type *SBPTy = PointerType::get(Type::Int8Ty);
2089 if (V->getType() != SBPTy)
2090 return new BitCastInst(V, SBPTy, V->getName(), &IP);
2095 // Additional cases that we need to add to this file:
2098 // * cbrt(expN(X)) -> expN(x/3)
2099 // * cbrt(sqrt(x)) -> pow(x,1/6)
2100 // * cbrt(sqrt(x)) -> pow(x,1/9)
2103 // * cos(-x) -> cos(x)
2106 // * exp(log(x)) -> x
2109 // * log(exp(x)) -> x
2110 // * log(x**y) -> y*log(x)
2111 // * log(exp(y)) -> y*log(e)
2112 // * log(exp2(y)) -> y*log(2)
2113 // * log(exp10(y)) -> y*log(10)
2114 // * log(sqrt(x)) -> 0.5*log(x)
2115 // * log(pow(x,y)) -> y*log(x)
2117 // lround, lroundf, lroundl:
2118 // * lround(cnst) -> cnst'
2121 // * memcmp(x,y,l) -> cnst
2122 // (if all arguments are constant and strlen(x) <= l and strlen(y) <= l)
2125 // * memmove(d,s,l,a) -> memcpy(d,s,l,a)
2126 // (if s is a global constant array)
2129 // * pow(exp(x),y) -> exp(x*y)
2130 // * pow(sqrt(x),y) -> pow(x,y*0.5)
2131 // * pow(pow(x,y),z)-> pow(x,y*z)
2134 // * puts("") -> fputc("\n",stdout) (how do we get "stdout"?)
2136 // round, roundf, roundl:
2137 // * round(cnst) -> cnst'
2140 // * signbit(cnst) -> cnst'
2141 // * signbit(nncst) -> 0 (if pstv is a non-negative constant)
2143 // sqrt, sqrtf, sqrtl:
2144 // * sqrt(expN(x)) -> expN(x*0.5)
2145 // * sqrt(Nroot(x)) -> pow(x,1/(2*N))
2146 // * sqrt(pow(x,y)) -> pow(|x|,y*0.5)
2149 // * stpcpy(str, "literal") ->
2150 // llvm.memcpy(str,"literal",strlen("literal")+1,1)
2152 // * strrchr(s,c) -> reverse_offset_of_in(c,s)
2153 // (if c is a constant integer and s is a constant string)
2154 // * strrchr(s1,0) -> strchr(s1,0)
2157 // * strncat(x,y,0) -> x
2158 // * strncat(x,y,0) -> x (if strlen(y) = 0)
2159 // * strncat(x,y,l) -> strcat(x,y) (if y and l are constants an l > strlen(y))
2162 // * strncpy(d,s,0) -> d
2163 // * strncpy(d,s,l) -> memcpy(d,s,l,1)
2164 // (if s and l are constants)
2167 // * strpbrk(s,a) -> offset_in_for(s,a)
2168 // (if s and a are both constant strings)
2169 // * strpbrk(s,"") -> 0
2170 // * strpbrk(s,a) -> strchr(s,a[0]) (if a is constant string of length 1)
2173 // * strspn(s,a) -> const_int (if both args are constant)
2174 // * strspn("",a) -> 0
2175 // * strspn(s,"") -> 0
2176 // * strcspn(s,a) -> const_int (if both args are constant)
2177 // * strcspn("",a) -> 0
2178 // * strcspn(s,"") -> strlen(a)
2181 // * strstr(x,x) -> x
2182 // * strstr(s1,s2) -> offset_of_s2_in(s1)
2183 // (if s1 and s2 are constant strings)
2186 // * tan(atan(x)) -> x
2188 // trunc, truncf, truncl:
2189 // * trunc(cnst) -> cnst'