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 or dllimport linkage and non-empty uses.
182 if (!FI->isExternal() ||
183 !(FI->hasExternalLinkage() || FI->hasDLLImportLinkage()) ||
187 // Get the optimization class that pertains to this function
188 hash_map<std::string, LibCallOptimization*>::iterator OMI =
189 OptznMap.find(FI->getName());
190 if (OMI == OptznMap.end()) continue;
192 LibCallOptimization *CO = OMI->second;
194 // Make sure the called function is suitable for the optimization
195 if (!CO->ValidateCalledFunction(FI, *this))
198 // Loop over each of the uses of the function
199 for (Value::use_iterator UI = FI->use_begin(), UE = FI->use_end();
201 // If the use of the function is a call instruction
202 if (CallInst* CI = dyn_cast<CallInst>(*UI++)) {
203 // Do the optimization on the LibCallOptimization.
204 if (CO->OptimizeCall(CI, *this)) {
205 ++SimplifiedLibCalls;
206 found_optimization = result = true;
212 } while (found_optimization);
217 /// @brief Return the *current* module we're working on.
218 Module* getModule() const { return M; }
220 /// @brief Return the *current* target data for the module we're working on.
221 TargetData* getTargetData() const { return TD; }
223 /// @brief Return the size_t type -- syntactic shortcut
224 const Type* getIntPtrType() const { return TD->getIntPtrType(); }
226 /// @brief Return a Function* for the putchar libcall
227 Function* get_putchar() {
229 putchar_func = M->getOrInsertFunction("putchar", Type::IntTy, Type::IntTy,
234 /// @brief Return a Function* for the puts libcall
235 Function* get_puts() {
237 puts_func = M->getOrInsertFunction("puts", Type::IntTy,
238 PointerType::get(Type::SByteTy),
243 /// @brief Return a Function* for the fputc libcall
244 Function* get_fputc(const Type* FILEptr_type) {
246 fputc_func = M->getOrInsertFunction("fputc", Type::IntTy, Type::IntTy,
251 /// @brief Return a Function* for the fputs libcall
252 Function* get_fputs(const Type* FILEptr_type) {
254 fputs_func = M->getOrInsertFunction("fputs", Type::IntTy,
255 PointerType::get(Type::SByteTy),
260 /// @brief Return a Function* for the fwrite libcall
261 Function* get_fwrite(const Type* FILEptr_type) {
263 fwrite_func = M->getOrInsertFunction("fwrite", TD->getIntPtrType(),
264 PointerType::get(Type::SByteTy),
271 /// @brief Return a Function* for the sqrt libcall
272 Function* get_sqrt() {
274 sqrt_func = M->getOrInsertFunction("sqrt", Type::DoubleTy,
275 Type::DoubleTy, NULL);
279 /// @brief Return a Function* for the strlen libcall
280 Function* get_strcpy() {
282 strcpy_func = M->getOrInsertFunction("strcpy",
283 PointerType::get(Type::SByteTy),
284 PointerType::get(Type::SByteTy),
285 PointerType::get(Type::SByteTy),
290 /// @brief Return a Function* for the strlen libcall
291 Function* get_strlen() {
293 strlen_func = M->getOrInsertFunction("strlen", TD->getIntPtrType(),
294 PointerType::get(Type::SByteTy),
299 /// @brief Return a Function* for the memchr libcall
300 Function* get_memchr() {
302 memchr_func = M->getOrInsertFunction("memchr",
303 PointerType::get(Type::SByteTy),
304 PointerType::get(Type::SByteTy),
305 Type::IntTy, TD->getIntPtrType(),
310 /// @brief Return a Function* for the memcpy libcall
311 Function* get_memcpy() {
313 const Type *SBP = PointerType::get(Type::SByteTy);
314 const char *N = TD->getIntPtrType() == Type::UIntTy ?
315 "llvm.memcpy.i32" : "llvm.memcpy.i64";
316 memcpy_func = M->getOrInsertFunction(N, Type::VoidTy, SBP, SBP,
317 TD->getIntPtrType(), Type::UIntTy,
323 Function *getUnaryFloatFunction(const char *Name, Function *&Cache) {
325 Cache = M->getOrInsertFunction(Name, Type::FloatTy, Type::FloatTy, NULL);
329 Function *get_floorf() { return getUnaryFloatFunction("floorf", floorf_func);}
330 Function *get_ceilf() { return getUnaryFloatFunction( "ceilf", ceilf_func);}
331 Function *get_roundf() { return getUnaryFloatFunction("roundf", roundf_func);}
332 Function *get_rintf() { return getUnaryFloatFunction( "rintf", rintf_func);}
333 Function *get_nearbyintf() { return getUnaryFloatFunction("nearbyintf",
336 /// @brief Reset our cached data for a new Module
337 void reset(Module& mod) {
339 TD = &getAnalysis<TargetData>();
358 /// Caches for function pointers.
359 Function *putchar_func, *puts_func;
360 Function *fputc_func, *fputs_func, *fwrite_func;
361 Function *memcpy_func, *memchr_func;
363 Function *strcpy_func, *strlen_func;
364 Function *floorf_func, *ceilf_func, *roundf_func;
365 Function *rintf_func, *nearbyintf_func;
366 Module *M; ///< Cached Module
367 TargetData *TD; ///< Cached TargetData
371 RegisterPass<SimplifyLibCalls>
372 X("simplify-libcalls", "Simplify well-known library calls");
374 } // anonymous namespace
376 // The only public symbol in this file which just instantiates the pass object
377 ModulePass *llvm::createSimplifyLibCallsPass() {
378 return new SimplifyLibCalls();
381 // Classes below here, in the anonymous namespace, are all subclasses of the
382 // LibCallOptimization class, each implementing all optimizations possible for a
383 // single well-known library call. Each has a static singleton instance that
384 // auto registers it into the "optlist" global above.
387 // Forward declare utility functions.
388 bool getConstantStringLength(Value* V, uint64_t& len, ConstantArray** A = 0 );
389 Value *CastToCStr(Value *V, Instruction &IP);
391 /// This LibCallOptimization will find instances of a call to "exit" that occurs
392 /// within the "main" function and change it to a simple "ret" instruction with
393 /// the same value passed to the exit function. When this is done, it splits the
394 /// basic block at the exit(3) call and deletes the call instruction.
395 /// @brief Replace calls to exit in main with a simple return
396 struct ExitInMainOptimization : public LibCallOptimization {
397 ExitInMainOptimization() : LibCallOptimization("exit",
398 "Number of 'exit' calls simplified") {}
400 // Make sure the called function looks like exit (int argument, int return
401 // type, external linkage, not varargs).
402 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
403 return F->arg_size() >= 1 && F->arg_begin()->getType()->isInteger();
406 virtual bool OptimizeCall(CallInst* ci, SimplifyLibCalls& SLC) {
407 // To be careful, we check that the call to exit is coming from "main", that
408 // main has external linkage, and the return type of main and the argument
409 // to exit have the same type.
410 Function *from = ci->getParent()->getParent();
411 if (from->hasExternalLinkage())
412 if (from->getReturnType() == ci->getOperand(1)->getType())
413 if (from->getName() == "main") {
414 // Okay, time to actually do the optimization. First, get the basic
415 // block of the call instruction
416 BasicBlock* bb = ci->getParent();
418 // Create a return instruction that we'll replace the call with.
419 // Note that the argument of the return is the argument of the call
421 new ReturnInst(ci->getOperand(1), ci);
423 // Split the block at the call instruction which places it in a new
425 bb->splitBasicBlock(ci);
427 // The block split caused a branch instruction to be inserted into
428 // the end of the original block, right after the return instruction
429 // that we put there. That's not a valid block, so delete the branch
431 bb->getInstList().pop_back();
433 // Now we can finally get rid of the call instruction which now lives
434 // in the new basic block.
435 ci->eraseFromParent();
437 // Optimization succeeded, return true.
440 // We didn't pass the criteria for this optimization so return false
443 } ExitInMainOptimizer;
445 /// This LibCallOptimization will simplify a call to the strcat library
446 /// function. The simplification is possible only if the string being
447 /// concatenated is a constant array or a constant expression that results in
448 /// a constant string. In this case we can replace it with strlen + llvm.memcpy
449 /// of the constant string. Both of these calls are further reduced, if possible
450 /// on subsequent passes.
451 /// @brief Simplify the strcat library function.
452 struct StrCatOptimization : public LibCallOptimization {
454 /// @brief Default constructor
455 StrCatOptimization() : LibCallOptimization("strcat",
456 "Number of 'strcat' calls simplified") {}
460 /// @brief Make sure that the "strcat" function has the right prototype
461 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC){
462 if (f->getReturnType() == PointerType::get(Type::SByteTy))
463 if (f->arg_size() == 2)
465 Function::const_arg_iterator AI = f->arg_begin();
466 if (AI++->getType() == PointerType::get(Type::SByteTy))
467 if (AI->getType() == PointerType::get(Type::SByteTy))
469 // Indicate this is a suitable call type.
476 /// @brief Optimize the strcat library function
477 virtual bool OptimizeCall(CallInst* ci, SimplifyLibCalls& SLC) {
478 // Extract some information from the instruction
479 Value* dest = ci->getOperand(1);
480 Value* src = ci->getOperand(2);
482 // Extract the initializer (while making numerous checks) from the
483 // source operand of the call to strcat. If we get null back, one of
484 // a variety of checks in get_GVInitializer failed
486 if (!getConstantStringLength(src,len))
489 // Handle the simple, do-nothing case
491 ci->replaceAllUsesWith(dest);
492 ci->eraseFromParent();
496 // Increment the length because we actually want to memcpy the null
497 // terminator as well.
500 // We need to find the end of the destination string. That's where the
501 // memory is to be moved to. We just generate a call to strlen (further
502 // optimized in another pass). Note that the SLC.get_strlen() call
503 // caches the Function* for us.
504 CallInst* strlen_inst =
505 new CallInst(SLC.get_strlen(), dest, dest->getName()+".len",ci);
507 // Now that we have the destination's length, we must index into the
508 // destination's pointer to get the actual memcpy destination (end of
509 // the string .. we're concatenating).
510 std::vector<Value*> idx;
511 idx.push_back(strlen_inst);
512 GetElementPtrInst* gep =
513 new GetElementPtrInst(dest,idx,dest->getName()+".indexed",ci);
515 // We have enough information to now generate the memcpy call to
516 // do the concatenation for us.
517 std::vector<Value*> vals;
518 vals.push_back(gep); // destination
519 vals.push_back(ci->getOperand(2)); // source
520 vals.push_back(ConstantUInt::get(SLC.getIntPtrType(),len)); // length
521 vals.push_back(ConstantUInt::get(Type::UIntTy,1)); // alignment
522 new CallInst(SLC.get_memcpy(), vals, "", ci);
524 // Finally, substitute the first operand of the strcat call for the
525 // strcat call itself since strcat returns its first operand; and,
526 // kill the strcat CallInst.
527 ci->replaceAllUsesWith(dest);
528 ci->eraseFromParent();
533 /// This LibCallOptimization will simplify a call to the strchr library
534 /// function. It optimizes out cases where the arguments are both constant
535 /// and the result can be determined statically.
536 /// @brief Simplify the strcmp library function.
537 struct StrChrOptimization : public LibCallOptimization {
539 StrChrOptimization() : LibCallOptimization("strchr",
540 "Number of 'strchr' calls simplified") {}
542 /// @brief Make sure that the "strchr" function has the right prototype
543 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC){
544 if (f->getReturnType() == PointerType::get(Type::SByteTy) &&
550 /// @brief Perform the strchr optimizations
551 virtual bool OptimizeCall(CallInst *ci, SimplifyLibCalls &SLC) {
552 // If there aren't three operands, bail
553 if (ci->getNumOperands() != 3)
556 // Check that the first argument to strchr is a constant array of sbyte.
557 // If it is, get the length and data, otherwise return false.
560 if (!getConstantStringLength(ci->getOperand(1),len,&CA))
563 // Check that the second argument to strchr is a constant int, return false
565 ConstantSInt* CSI = dyn_cast<ConstantSInt>(ci->getOperand(2));
567 // Just lower this to memchr since we know the length of the string as
569 Function* f = SLC.get_memchr();
570 std::vector<Value*> args;
571 args.push_back(ci->getOperand(1));
572 args.push_back(ci->getOperand(2));
573 args.push_back(ConstantUInt::get(SLC.getIntPtrType(),len));
574 ci->replaceAllUsesWith( new CallInst(f,args,ci->getName(),ci));
575 ci->eraseFromParent();
579 // Get the character we're looking for
580 int64_t chr = CSI->getValue();
582 // Compute the offset
584 bool char_found = false;
585 for (uint64_t i = 0; i < len; ++i) {
586 if (ConstantSInt* CI = dyn_cast<ConstantSInt>(CA->getOperand(i))) {
587 // Check for the null terminator
588 if (CI->isNullValue())
589 break; // we found end of string
590 else if (CI->getValue() == chr) {
598 // strchr(s,c) -> offset_of_in(c,s)
599 // (if c is a constant integer and s is a constant string)
601 std::vector<Value*> indices;
602 indices.push_back(ConstantUInt::get(Type::ULongTy,offset));
603 GetElementPtrInst* GEP = new GetElementPtrInst(ci->getOperand(1),indices,
604 ci->getOperand(1)->getName()+".strchr",ci);
605 ci->replaceAllUsesWith(GEP);
607 ci->replaceAllUsesWith(
608 ConstantPointerNull::get(PointerType::get(Type::SByteTy)));
610 ci->eraseFromParent();
615 /// This LibCallOptimization will simplify a call to the strcmp library
616 /// function. It optimizes out cases where one or both arguments are constant
617 /// and the result can be determined statically.
618 /// @brief Simplify the strcmp library function.
619 struct StrCmpOptimization : public LibCallOptimization {
621 StrCmpOptimization() : LibCallOptimization("strcmp",
622 "Number of 'strcmp' calls simplified") {}
624 /// @brief Make sure that the "strcmp" function has the right prototype
625 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
626 return F->getReturnType() == Type::IntTy && F->arg_size() == 2;
629 /// @brief Perform the strcmp optimization
630 virtual bool OptimizeCall(CallInst* ci, SimplifyLibCalls& SLC) {
631 // First, check to see if src and destination are the same. If they are,
632 // then the optimization is to replace the CallInst with a constant 0
633 // because the call is a no-op.
634 Value* s1 = ci->getOperand(1);
635 Value* s2 = ci->getOperand(2);
638 ci->replaceAllUsesWith(ConstantInt::get(Type::IntTy,0));
639 ci->eraseFromParent();
643 bool isstr_1 = false;
646 if (getConstantStringLength(s1,len_1,&A1)) {
649 // strcmp("",x) -> *x
651 new LoadInst(CastToCStr(s2,*ci), ci->getName()+".load",ci);
653 new CastInst(load,Type::IntTy,ci->getName()+".int",ci);
654 ci->replaceAllUsesWith(cast);
655 ci->eraseFromParent();
660 bool isstr_2 = false;
663 if (getConstantStringLength(s2, len_2, &A2)) {
666 // strcmp(x,"") -> *x
668 new LoadInst(CastToCStr(s1,*ci),ci->getName()+".val",ci);
670 new CastInst(load,Type::IntTy,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(ConstantSInt::get(Type::IntTy,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::IntTy && 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::IntTy,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->getRawValue();
728 // strncmp(x,y,0) -> 0
729 ci->replaceAllUsesWith(ConstantInt::get(Type::IntTy,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 new CastInst(load,Type::IntTy,ci->getName()+".int",ci);
745 ci->replaceAllUsesWith(cast);
746 ci->eraseFromParent();
751 bool isstr_2 = false;
754 if (getConstantStringLength(s2,len_2,&A2)) {
757 // strncmp(x,"") -> *x
758 LoadInst* load = new LoadInst(s2,ci->getName()+".val",ci);
760 new CastInst(load,Type::IntTy,ci->getName()+".int",ci);
761 ci->replaceAllUsesWith(cast);
762 ci->eraseFromParent();
767 if (isstr_1 && isstr_2 && len_arg_is_const) {
768 // strncmp(x,y,const) -> constant
769 std::string str1 = A1->getAsString();
770 std::string str2 = A2->getAsString();
771 int result = strncmp(str1.c_str(), str2.c_str(), len_arg);
772 ci->replaceAllUsesWith(ConstantSInt::get(Type::IntTy,result));
773 ci->eraseFromParent();
780 /// This LibCallOptimization will simplify a call to the strcpy library
781 /// function. Two optimizations are possible:
782 /// (1) If src and dest are the same and not volatile, just return dest
783 /// (2) If the src is a constant then we can convert to llvm.memmove
784 /// @brief Simplify the strcpy library function.
785 struct StrCpyOptimization : public LibCallOptimization {
787 StrCpyOptimization() : LibCallOptimization("strcpy",
788 "Number of 'strcpy' calls simplified") {}
790 /// @brief Make sure that the "strcpy" function has the right prototype
791 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC){
792 if (f->getReturnType() == PointerType::get(Type::SByteTy))
793 if (f->arg_size() == 2) {
794 Function::const_arg_iterator AI = f->arg_begin();
795 if (AI++->getType() == PointerType::get(Type::SByteTy))
796 if (AI->getType() == PointerType::get(Type::SByteTy)) {
797 // Indicate this is a suitable call type.
804 /// @brief Perform the strcpy optimization
805 virtual bool OptimizeCall(CallInst* ci, SimplifyLibCalls& SLC) {
806 // First, check to see if src and destination are the same. If they are,
807 // then the optimization is to replace the CallInst with the destination
808 // because the call is a no-op. Note that this corresponds to the
809 // degenerate strcpy(X,X) case which should have "undefined" results
810 // according to the C specification. However, it occurs sometimes and
811 // we optimize it as a no-op.
812 Value* dest = ci->getOperand(1);
813 Value* src = ci->getOperand(2);
815 ci->replaceAllUsesWith(dest);
816 ci->eraseFromParent();
820 // Get the length of the constant string referenced by the second operand,
821 // the "src" parameter. Fail the optimization if we can't get the length
822 // (note that getConstantStringLength does lots of checks to make sure this
825 if (!getConstantStringLength(ci->getOperand(2),len))
828 // If the constant string's length is zero we can optimize this by just
829 // doing a store of 0 at the first byte of the destination
831 new StoreInst(ConstantInt::get(Type::SByteTy,0),ci->getOperand(1),ci);
832 ci->replaceAllUsesWith(dest);
833 ci->eraseFromParent();
837 // Increment the length because we actually want to memcpy the null
838 // terminator as well.
841 // We have enough information to now generate the memcpy call to
842 // do the concatenation for us.
843 std::vector<Value*> vals;
844 vals.push_back(dest); // destination
845 vals.push_back(src); // source
846 vals.push_back(ConstantUInt::get(SLC.getIntPtrType(),len)); // length
847 vals.push_back(ConstantUInt::get(Type::UIntTy,1)); // alignment
848 new CallInst(SLC.get_memcpy(), vals, "", ci);
850 // Finally, substitute the first operand of the strcat call for the
851 // strcat call itself since strcat returns its first operand; and,
852 // kill the strcat CallInst.
853 ci->replaceAllUsesWith(dest);
854 ci->eraseFromParent();
859 /// This LibCallOptimization will simplify a call to the strlen library
860 /// function by replacing it with a constant value if the string provided to
861 /// it is a constant array.
862 /// @brief Simplify the strlen library function.
863 struct StrLenOptimization : public LibCallOptimization {
864 StrLenOptimization() : LibCallOptimization("strlen",
865 "Number of 'strlen' calls simplified") {}
867 /// @brief Make sure that the "strlen" function has the right prototype
868 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC)
870 if (f->getReturnType() == SLC.getTargetData()->getIntPtrType())
871 if (f->arg_size() == 1)
872 if (Function::const_arg_iterator AI = f->arg_begin())
873 if (AI->getType() == PointerType::get(Type::SByteTy))
878 /// @brief Perform the strlen optimization
879 virtual bool OptimizeCall(CallInst* ci, SimplifyLibCalls& SLC)
881 // Make sure we're dealing with an sbyte* here.
882 Value* str = ci->getOperand(1);
883 if (str->getType() != PointerType::get(Type::SByteTy))
886 // Does the call to strlen have exactly one use?
888 // Is that single use a binary operator?
889 if (BinaryOperator* bop = dyn_cast<BinaryOperator>(ci->use_back()))
890 // Is it compared against a constant integer?
891 if (ConstantInt* CI = dyn_cast<ConstantInt>(bop->getOperand(1)))
893 // Get the value the strlen result is compared to
894 uint64_t val = CI->getRawValue();
896 // If its compared against length 0 with == or !=
898 (bop->getOpcode() == Instruction::SetEQ ||
899 bop->getOpcode() == Instruction::SetNE))
901 // strlen(x) != 0 -> *x != 0
902 // strlen(x) == 0 -> *x == 0
903 LoadInst* load = new LoadInst(str,str->getName()+".first",ci);
904 BinaryOperator* rbop = BinaryOperator::create(bop->getOpcode(),
905 load, ConstantSInt::get(Type::SByteTy,0),
906 bop->getName()+".strlen", ci);
907 bop->replaceAllUsesWith(rbop);
908 bop->eraseFromParent();
909 ci->eraseFromParent();
914 // Get the length of the constant string operand
916 if (!getConstantStringLength(ci->getOperand(1),len))
919 // strlen("xyz") -> 3 (for example)
920 const Type *Ty = SLC.getTargetData()->getIntPtrType();
922 ci->replaceAllUsesWith(ConstantSInt::get(Ty, len));
924 ci->replaceAllUsesWith(ConstantUInt::get(Ty, len));
926 ci->eraseFromParent();
931 /// IsOnlyUsedInEqualsComparison - Return true if it only matters that the value
932 /// is equal or not-equal to zero.
933 static bool IsOnlyUsedInEqualsZeroComparison(Instruction *I) {
934 for (Value::use_iterator UI = I->use_begin(), E = I->use_end();
936 Instruction *User = cast<Instruction>(*UI);
937 if (User->getOpcode() == Instruction::SetNE ||
938 User->getOpcode() == Instruction::SetEQ) {
939 if (isa<Constant>(User->getOperand(1)) &&
940 cast<Constant>(User->getOperand(1))->isNullValue())
942 } else if (CastInst *CI = dyn_cast<CastInst>(User))
943 if (CI->getType() == Type::BoolTy)
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->getRawValue();
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::UByteTy);
1000 CastInst *Op1Cast = new CastInst(LHS, UCharPtr, LHS->getName(), CI);
1001 CastInst *Op2Cast = new CastInst(RHS, UCharPtr, RHS->getName(), CI);
1002 Value *S1V = new LoadInst(Op1Cast, LHS->getName()+".val", CI);
1003 Value *S2V = new LoadInst(Op2Cast, RHS->getName()+".val", CI);
1004 Value *RV = BinaryOperator::createSub(S1V, S2V, CI->getName()+".diff",CI);
1005 if (RV->getType() != CI->getType())
1006 RV = new CastInst(RV, CI->getType(), RV->getName(), CI);
1007 CI->replaceAllUsesWith(RV);
1008 CI->eraseFromParent();
1012 if (IsOnlyUsedInEqualsZeroComparison(CI)) {
1013 // TODO: IF both are aligned, use a short load/compare.
1015 // memcmp(S1,S2,2) -> S1[0]-S2[0] | S1[1]-S2[1] iff only ==/!= 0 matters
1016 const Type *UCharPtr = PointerType::get(Type::UByteTy);
1017 CastInst *Op1Cast = new CastInst(LHS, UCharPtr, LHS->getName(), CI);
1018 CastInst *Op2Cast = new CastInst(RHS, UCharPtr, RHS->getName(), CI);
1019 Value *S1V1 = new LoadInst(Op1Cast, LHS->getName()+".val1", CI);
1020 Value *S2V1 = new LoadInst(Op2Cast, RHS->getName()+".val1", CI);
1021 Value *D1 = BinaryOperator::createSub(S1V1, S2V1,
1022 CI->getName()+".d1", CI);
1023 Constant *One = ConstantInt::get(Type::IntTy, 1);
1024 Value *G1 = new GetElementPtrInst(Op1Cast, One, "next1v", CI);
1025 Value *G2 = new GetElementPtrInst(Op2Cast, One, "next2v", CI);
1026 Value *S1V2 = new LoadInst(G1, LHS->getName()+".val2", CI);
1027 Value *S2V2 = new LoadInst(G2, RHS->getName()+".val2", CI);
1028 Value *D2 = BinaryOperator::createSub(S1V2, S2V2,
1029 CI->getName()+".d1", CI);
1030 Value *Or = BinaryOperator::createOr(D1, D2, CI->getName()+".res", CI);
1031 if (Or->getType() != CI->getType())
1032 Or = new CastInst(Or, CI->getType(), Or->getName(), CI);
1033 CI->replaceAllUsesWith(Or);
1034 CI->eraseFromParent();
1047 /// This LibCallOptimization will simplify a call to the memcpy library
1048 /// function by expanding it out to a single store of size 0, 1, 2, 4, or 8
1049 /// bytes depending on the length of the string and the alignment. Additional
1050 /// optimizations are possible in code generation (sequence of immediate store)
1051 /// @brief Simplify the memcpy library function.
1052 struct LLVMMemCpyMoveOptzn : public LibCallOptimization {
1053 LLVMMemCpyMoveOptzn(const char* fname, const char* desc)
1054 : LibCallOptimization(fname, desc) {}
1056 /// @brief Make sure that the "memcpy" function has the right prototype
1057 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& TD) {
1058 // Just make sure this has 4 arguments per LLVM spec.
1059 return (f->arg_size() == 4);
1062 /// Because of alignment and instruction information that we don't have, we
1063 /// leave the bulk of this to the code generators. The optimization here just
1064 /// deals with a few degenerate cases where the length of the string and the
1065 /// alignment match the sizes of our intrinsic types so we can do a load and
1066 /// store instead of the memcpy call.
1067 /// @brief Perform the memcpy optimization.
1068 virtual bool OptimizeCall(CallInst* ci, SimplifyLibCalls& TD) {
1069 // Make sure we have constant int values to work with
1070 ConstantInt* LEN = dyn_cast<ConstantInt>(ci->getOperand(3));
1073 ConstantInt* ALIGN = dyn_cast<ConstantInt>(ci->getOperand(4));
1077 // If the length is larger than the alignment, we can't optimize
1078 uint64_t len = LEN->getRawValue();
1079 uint64_t alignment = ALIGN->getRawValue();
1081 alignment = 1; // Alignment 0 is identity for alignment 1
1082 if (len > alignment)
1085 // Get the type we will cast to, based on size of the string
1086 Value* dest = ci->getOperand(1);
1087 Value* src = ci->getOperand(2);
1092 // memcpy(d,s,0,a) -> noop
1093 ci->eraseFromParent();
1095 case 1: castType = Type::SByteTy; break;
1096 case 2: castType = Type::ShortTy; break;
1097 case 4: castType = Type::IntTy; break;
1098 case 8: castType = Type::LongTy; break;
1103 // Cast source and dest to the right sized primitive and then load/store
1105 new CastInst(src,PointerType::get(castType),src->getName()+".cast",ci);
1106 CastInst* DestCast =
1107 new CastInst(dest,PointerType::get(castType),dest->getName()+".cast",ci);
1108 LoadInst* LI = new LoadInst(SrcCast,SrcCast->getName()+".val",ci);
1109 StoreInst* SI = new StoreInst(LI, DestCast, ci);
1110 ci->eraseFromParent();
1115 /// This LibCallOptimization will simplify a call to the memcpy/memmove library
1117 LLVMMemCpyMoveOptzn LLVMMemCpyOptimizer32("llvm.memcpy.i32",
1118 "Number of 'llvm.memcpy' calls simplified");
1119 LLVMMemCpyMoveOptzn LLVMMemCpyOptimizer64("llvm.memcpy.i64",
1120 "Number of 'llvm.memcpy' calls simplified");
1121 LLVMMemCpyMoveOptzn LLVMMemMoveOptimizer32("llvm.memmove.i32",
1122 "Number of 'llvm.memmove' calls simplified");
1123 LLVMMemCpyMoveOptzn LLVMMemMoveOptimizer64("llvm.memmove.i64",
1124 "Number of 'llvm.memmove' calls simplified");
1126 /// This LibCallOptimization will simplify a call to the memset library
1127 /// function by expanding it out to a single store of size 0, 1, 2, 4, or 8
1128 /// bytes depending on the length argument.
1129 struct LLVMMemSetOptimization : public LibCallOptimization {
1130 /// @brief Default Constructor
1131 LLVMMemSetOptimization(const char *Name) : LibCallOptimization(Name,
1132 "Number of 'llvm.memset' calls simplified") {}
1134 /// @brief Make sure that the "memset" function has the right prototype
1135 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &TD) {
1136 // Just make sure this has 3 arguments per LLVM spec.
1137 return F->arg_size() == 4;
1140 /// Because of alignment and instruction information that we don't have, we
1141 /// leave the bulk of this to the code generators. The optimization here just
1142 /// deals with a few degenerate cases where the length parameter is constant
1143 /// and the alignment matches the sizes of our intrinsic types so we can do
1144 /// store instead of the memcpy call. Other calls are transformed into the
1145 /// llvm.memset intrinsic.
1146 /// @brief Perform the memset optimization.
1147 virtual bool OptimizeCall(CallInst *ci, SimplifyLibCalls &TD) {
1148 // Make sure we have constant int values to work with
1149 ConstantInt* LEN = dyn_cast<ConstantInt>(ci->getOperand(3));
1152 ConstantInt* ALIGN = dyn_cast<ConstantInt>(ci->getOperand(4));
1156 // Extract the length and alignment
1157 uint64_t len = LEN->getRawValue();
1158 uint64_t alignment = ALIGN->getRawValue();
1160 // Alignment 0 is identity for alignment 1
1164 // If the length is zero, this is a no-op
1166 // memset(d,c,0,a) -> noop
1167 ci->eraseFromParent();
1171 // If the length is larger than the alignment, we can't optimize
1172 if (len > alignment)
1175 // Make sure we have a constant ubyte to work with so we can extract
1176 // the value to be filled.
1177 ConstantUInt* FILL = dyn_cast<ConstantUInt>(ci->getOperand(2));
1180 if (FILL->getType() != Type::UByteTy)
1183 // memset(s,c,n) -> store s, c (for n=1,2,4,8)
1185 // Extract the fill character
1186 uint64_t fill_char = FILL->getValue();
1187 uint64_t fill_value = fill_char;
1189 // Get the type we will cast to, based on size of memory area to fill, and
1190 // and the value we will store there.
1191 Value* dest = ci->getOperand(1);
1195 castType = Type::UByteTy;
1198 castType = Type::UShortTy;
1199 fill_value |= fill_char << 8;
1202 castType = Type::UIntTy;
1203 fill_value |= fill_char << 8 | fill_char << 16 | fill_char << 24;
1206 castType = Type::ULongTy;
1207 fill_value |= fill_char << 8 | fill_char << 16 | fill_char << 24;
1208 fill_value |= fill_char << 32 | fill_char << 40 | fill_char << 48;
1209 fill_value |= fill_char << 56;
1215 // Cast dest to the right sized primitive and then load/store
1216 CastInst* DestCast =
1217 new CastInst(dest,PointerType::get(castType),dest->getName()+".cast",ci);
1218 new StoreInst(ConstantUInt::get(castType,fill_value),DestCast, ci);
1219 ci->eraseFromParent();
1224 LLVMMemSetOptimization MemSet32Optimizer("llvm.memset.i32");
1225 LLVMMemSetOptimization MemSet64Optimizer("llvm.memset.i64");
1228 /// This LibCallOptimization will simplify calls to the "pow" library
1229 /// function. It looks for cases where the result of pow is well known and
1230 /// substitutes the appropriate value.
1231 /// @brief Simplify the pow library function.
1232 struct PowOptimization : public LibCallOptimization {
1234 /// @brief Default Constructor
1235 PowOptimization() : LibCallOptimization("pow",
1236 "Number of 'pow' calls simplified") {}
1238 /// @brief Make sure that the "pow" function has the right prototype
1239 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC){
1240 // Just make sure this has 2 arguments
1241 return (f->arg_size() == 2);
1244 /// @brief Perform the pow optimization.
1245 virtual bool OptimizeCall(CallInst *ci, SimplifyLibCalls &SLC) {
1246 const Type *Ty = cast<Function>(ci->getOperand(0))->getReturnType();
1247 Value* base = ci->getOperand(1);
1248 Value* expn = ci->getOperand(2);
1249 if (ConstantFP *Op1 = dyn_cast<ConstantFP>(base)) {
1250 double Op1V = Op1->getValue();
1252 // pow(1.0,x) -> 1.0
1253 ci->replaceAllUsesWith(ConstantFP::get(Ty,1.0));
1254 ci->eraseFromParent();
1257 } else if (ConstantFP* Op2 = dyn_cast<ConstantFP>(expn)) {
1258 double Op2V = Op2->getValue();
1260 // pow(x,0.0) -> 1.0
1261 ci->replaceAllUsesWith(ConstantFP::get(Ty,1.0));
1262 ci->eraseFromParent();
1264 } else if (Op2V == 0.5) {
1265 // pow(x,0.5) -> sqrt(x)
1266 CallInst* sqrt_inst = new CallInst(SLC.get_sqrt(), base,
1267 ci->getName()+".pow",ci);
1268 ci->replaceAllUsesWith(sqrt_inst);
1269 ci->eraseFromParent();
1271 } else if (Op2V == 1.0) {
1273 ci->replaceAllUsesWith(base);
1274 ci->eraseFromParent();
1276 } else if (Op2V == -1.0) {
1277 // pow(x,-1.0) -> 1.0/x
1278 BinaryOperator* div_inst= BinaryOperator::createDiv(
1279 ConstantFP::get(Ty,1.0), base, ci->getName()+".pow", ci);
1280 ci->replaceAllUsesWith(div_inst);
1281 ci->eraseFromParent();
1285 return false; // opt failed
1289 /// This LibCallOptimization will simplify calls to the "printf" library
1290 /// function. It looks for cases where the result of printf is not used and the
1291 /// operation can be reduced to something simpler.
1292 /// @brief Simplify the printf library function.
1293 struct PrintfOptimization : public LibCallOptimization {
1295 /// @brief Default Constructor
1296 PrintfOptimization() : LibCallOptimization("printf",
1297 "Number of 'printf' calls simplified") {}
1299 /// @brief Make sure that the "printf" function has the right prototype
1300 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC){
1301 // Just make sure this has at least 1 arguments
1302 return (f->arg_size() >= 1);
1305 /// @brief Perform the printf optimization.
1306 virtual bool OptimizeCall(CallInst* ci, SimplifyLibCalls& SLC) {
1307 // If the call has more than 2 operands, we can't optimize it
1308 if (ci->getNumOperands() > 3 || ci->getNumOperands() <= 2)
1311 // If the result of the printf call is used, none of these optimizations
1313 if (!ci->use_empty())
1316 // All the optimizations depend on the length of the first argument and the
1317 // fact that it is a constant string array. Check that now
1319 ConstantArray* CA = 0;
1320 if (!getConstantStringLength(ci->getOperand(1), len, &CA))
1323 if (len != 2 && len != 3)
1326 // The first character has to be a %
1327 if (ConstantInt* CI = dyn_cast<ConstantInt>(CA->getOperand(0)))
1328 if (CI->getRawValue() != '%')
1331 // Get the second character and switch on its value
1332 ConstantInt* CI = dyn_cast<ConstantInt>(CA->getOperand(1));
1333 switch (CI->getRawValue()) {
1337 dyn_cast<ConstantInt>(CA->getOperand(2))->getRawValue() != '\n')
1340 // printf("%s\n",str) -> puts(str)
1341 Function* puts_func = SLC.get_puts();
1344 std::vector<Value*> args;
1345 args.push_back(CastToCStr(ci->getOperand(2), *ci));
1346 new CallInst(puts_func,args,ci->getName(),ci);
1347 ci->replaceAllUsesWith(ConstantSInt::get(Type::IntTy,len));
1352 // printf("%c",c) -> putchar(c)
1356 Function* putchar_func = SLC.get_putchar();
1359 CastInst* cast = new CastInst(ci->getOperand(2), Type::IntTy,
1360 CI->getName()+".int", ci);
1361 new CallInst(putchar_func, cast, "", ci);
1362 ci->replaceAllUsesWith(ConstantSInt::get(Type::IntTy, 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->getRawValue() == '%')
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();
1421 Function* fwrite_func = SLC.get_fwrite(FILEptr_type);
1425 // Make sure that the fprintf() and fwrite() functions both take the
1426 // same type of char pointer.
1427 if (ci->getOperand(2)->getType() !=
1428 fwrite_func->getFunctionType()->getParamType(0))
1431 std::vector<Value*> args;
1432 args.push_back(ci->getOperand(2));
1433 args.push_back(ConstantUInt::get(SLC.getIntPtrType(),len));
1434 args.push_back(ConstantUInt::get(SLC.getIntPtrType(),1));
1435 args.push_back(ci->getOperand(1));
1436 new CallInst(fwrite_func,args,ci->getName(),ci);
1437 ci->replaceAllUsesWith(ConstantSInt::get(Type::IntTy,len));
1438 ci->eraseFromParent();
1442 // The remaining optimizations require the format string to be length 2
1447 // The first character has to be a %
1448 if (ConstantInt* CI = dyn_cast<ConstantInt>(CA->getOperand(0)))
1449 if (CI->getRawValue() != '%')
1452 // Get the second character and switch on its value
1453 ConstantInt* CI = dyn_cast<ConstantInt>(CA->getOperand(1));
1454 switch (CI->getRawValue()) {
1458 ConstantArray* CA = 0;
1459 if (getConstantStringLength(ci->getOperand(3), len, &CA)) {
1460 // fprintf(file,"%s",str) -> fwrite(str,strlen(str),1,file)
1461 const Type* FILEptr_type = ci->getOperand(1)->getType();
1462 Function* fwrite_func = SLC.get_fwrite(FILEptr_type);
1465 std::vector<Value*> args;
1466 args.push_back(CastToCStr(ci->getOperand(3), *ci));
1467 args.push_back(ConstantUInt::get(SLC.getIntPtrType(),len));
1468 args.push_back(ConstantUInt::get(SLC.getIntPtrType(),1));
1469 args.push_back(ci->getOperand(1));
1470 new CallInst(fwrite_func,args,ci->getName(),ci);
1471 ci->replaceAllUsesWith(ConstantSInt::get(Type::IntTy,len));
1473 // fprintf(file,"%s",str) -> fputs(str,file)
1474 const Type* FILEptr_type = ci->getOperand(1)->getType();
1475 Function* fputs_func = SLC.get_fputs(FILEptr_type);
1478 std::vector<Value*> args;
1479 args.push_back(CastToCStr(ci->getOperand(3), *ci));
1480 args.push_back(ci->getOperand(1));
1481 new CallInst(fputs_func,args,ci->getName(),ci);
1482 ci->replaceAllUsesWith(ConstantSInt::get(Type::IntTy,len));
1488 // fprintf(file,"%c",c) -> fputc(c,file)
1489 const Type* FILEptr_type = ci->getOperand(1)->getType();
1490 Function* fputc_func = SLC.get_fputc(FILEptr_type);
1493 CastInst* cast = new CastInst(ci->getOperand(3), Type::IntTy,
1494 CI->getName()+".int", ci);
1495 new CallInst(fputc_func,cast,ci->getOperand(1),"",ci);
1496 ci->replaceAllUsesWith(ConstantSInt::get(Type::IntTy,1));
1502 ci->eraseFromParent();
1507 /// This LibCallOptimization will simplify calls to the "sprintf" library
1508 /// function. It looks for cases where the result of sprintf is not used and the
1509 /// operation can be reduced to something simpler.
1510 /// @brief Simplify the sprintf library function.
1511 struct SPrintFOptimization : public LibCallOptimization {
1513 /// @brief Default Constructor
1514 SPrintFOptimization() : LibCallOptimization("sprintf",
1515 "Number of 'sprintf' calls simplified") {}
1517 /// @brief Make sure that the "fprintf" function has the right prototype
1518 virtual bool ValidateCalledFunction(const Function *f, SimplifyLibCalls &SLC){
1519 // Just make sure this has at least 2 arguments
1520 return (f->getReturnType() == Type::IntTy && f->arg_size() >= 2);
1523 /// @brief Perform the sprintf optimization.
1524 virtual bool OptimizeCall(CallInst *ci, SimplifyLibCalls &SLC) {
1525 // If the call has more than 3 operands, we can't optimize it
1526 if (ci->getNumOperands() > 4 || ci->getNumOperands() < 3)
1529 // All the optimizations depend on the length of the second argument and the
1530 // fact that it is a constant string array. Check that now
1532 ConstantArray* CA = 0;
1533 if (!getConstantStringLength(ci->getOperand(2), len, &CA))
1536 if (ci->getNumOperands() == 3) {
1538 // If the length is 0, we just need to store a null byte
1539 new StoreInst(ConstantInt::get(Type::SByteTy,0),ci->getOperand(1),ci);
1540 ci->replaceAllUsesWith(ConstantSInt::get(Type::IntTy,0));
1541 ci->eraseFromParent();
1545 // Make sure there's no % in the constant array
1546 for (unsigned i = 0; i < len; ++i) {
1547 if (ConstantInt* CI = dyn_cast<ConstantInt>(CA->getOperand(i))) {
1548 // Check for the null terminator
1549 if (CI->getRawValue() == '%')
1550 return false; // we found a %, can't optimize
1552 return false; // initializer is not constant int, can't optimize
1556 // Increment length because we want to copy the null byte too
1559 // sprintf(str,fmt) -> llvm.memcpy(str,fmt,strlen(fmt),1)
1560 Function* memcpy_func = SLC.get_memcpy();
1563 std::vector<Value*> args;
1564 args.push_back(ci->getOperand(1));
1565 args.push_back(ci->getOperand(2));
1566 args.push_back(ConstantUInt::get(SLC.getIntPtrType(),len));
1567 args.push_back(ConstantUInt::get(Type::UIntTy,1));
1568 new CallInst(memcpy_func,args,"",ci);
1569 ci->replaceAllUsesWith(ConstantSInt::get(Type::IntTy,len));
1570 ci->eraseFromParent();
1574 // The remaining optimizations require the format string to be length 2
1579 // The first character has to be a %
1580 if (ConstantInt* CI = dyn_cast<ConstantInt>(CA->getOperand(0)))
1581 if (CI->getRawValue() != '%')
1584 // Get the second character and switch on its value
1585 ConstantInt* CI = dyn_cast<ConstantInt>(CA->getOperand(1));
1586 switch (CI->getRawValue()) {
1588 // sprintf(dest,"%s",str) -> llvm.memcpy(dest, str, strlen(str)+1, 1)
1589 Function* strlen_func = SLC.get_strlen();
1590 Function* memcpy_func = SLC.get_memcpy();
1591 if (!strlen_func || !memcpy_func)
1594 Value *Len = new CallInst(strlen_func, CastToCStr(ci->getOperand(3), *ci),
1595 ci->getOperand(3)->getName()+".len", ci);
1596 Value *Len1 = BinaryOperator::createAdd(Len,
1597 ConstantInt::get(Len->getType(), 1),
1598 Len->getName()+"1", ci);
1599 if (Len1->getType() != SLC.getIntPtrType())
1600 Len1 = new CastInst(Len1, SLC.getIntPtrType(), Len1->getName(), ci);
1601 std::vector<Value*> args;
1602 args.push_back(CastToCStr(ci->getOperand(1), *ci));
1603 args.push_back(CastToCStr(ci->getOperand(3), *ci));
1604 args.push_back(Len1);
1605 args.push_back(ConstantUInt::get(Type::UIntTy,1));
1606 new CallInst(memcpy_func, args, "", ci);
1608 // The strlen result is the unincremented number of bytes in the string.
1609 if (!ci->use_empty()) {
1610 if (Len->getType() != ci->getType())
1611 Len = new CastInst(Len, ci->getType(), Len->getName(), ci);
1612 ci->replaceAllUsesWith(Len);
1614 ci->eraseFromParent();
1618 // sprintf(dest,"%c",chr) -> store chr, dest
1619 CastInst* cast = new CastInst(ci->getOperand(3),Type::SByteTy,"char",ci);
1620 new StoreInst(cast, ci->getOperand(1), ci);
1621 GetElementPtrInst* gep = new GetElementPtrInst(ci->getOperand(1),
1622 ConstantUInt::get(Type::UIntTy,1),ci->getOperand(1)->getName()+".end",
1624 new StoreInst(ConstantInt::get(Type::SByteTy,0),gep,ci);
1625 ci->replaceAllUsesWith(ConstantSInt::get(Type::IntTy,1));
1626 ci->eraseFromParent();
1634 /// This LibCallOptimization will simplify calls to the "fputs" library
1635 /// function. It looks for cases where the result of fputs is not used and the
1636 /// operation can be reduced to something simpler.
1637 /// @brief Simplify the puts library function.
1638 struct PutsOptimization : public LibCallOptimization {
1640 /// @brief Default Constructor
1641 PutsOptimization() : LibCallOptimization("fputs",
1642 "Number of 'fputs' calls simplified") {}
1644 /// @brief Make sure that the "fputs" function has the right prototype
1645 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
1646 // Just make sure this has 2 arguments
1647 return F->arg_size() == 2;
1650 /// @brief Perform the fputs optimization.
1651 virtual bool OptimizeCall(CallInst* ci, SimplifyLibCalls& SLC) {
1652 // If the result is used, none of these optimizations work
1653 if (!ci->use_empty())
1656 // All the optimizations depend on the length of the first argument and the
1657 // fact that it is a constant string array. Check that now
1659 if (!getConstantStringLength(ci->getOperand(1), len))
1664 // fputs("",F) -> noop
1668 // fputs(s,F) -> fputc(s[0],F) (if s is constant and strlen(s) == 1)
1669 const Type* FILEptr_type = ci->getOperand(2)->getType();
1670 Function* fputc_func = SLC.get_fputc(FILEptr_type);
1673 LoadInst* loadi = new LoadInst(ci->getOperand(1),
1674 ci->getOperand(1)->getName()+".byte",ci);
1675 CastInst* casti = new CastInst(loadi,Type::IntTy,
1676 loadi->getName()+".int",ci);
1677 new CallInst(fputc_func,casti,ci->getOperand(2),"",ci);
1682 // fputs(s,F) -> fwrite(s,1,len,F) (if s is constant and strlen(s) > 1)
1683 const Type* FILEptr_type = ci->getOperand(2)->getType();
1684 Function* fwrite_func = SLC.get_fwrite(FILEptr_type);
1687 std::vector<Value*> parms;
1688 parms.push_back(ci->getOperand(1));
1689 parms.push_back(ConstantUInt::get(SLC.getIntPtrType(),len));
1690 parms.push_back(ConstantUInt::get(SLC.getIntPtrType(),1));
1691 parms.push_back(ci->getOperand(2));
1692 new CallInst(fwrite_func,parms,"",ci);
1696 ci->eraseFromParent();
1697 return true; // success
1701 /// This LibCallOptimization will simplify calls to the "isdigit" library
1702 /// function. It simply does range checks the parameter explicitly.
1703 /// @brief Simplify the isdigit library function.
1704 struct isdigitOptimization : public LibCallOptimization {
1706 isdigitOptimization() : LibCallOptimization("isdigit",
1707 "Number of 'isdigit' calls simplified") {}
1709 /// @brief Make sure that the "isdigit" function has the right prototype
1710 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC){
1711 // Just make sure this has 1 argument
1712 return (f->arg_size() == 1);
1715 /// @brief Perform the toascii optimization.
1716 virtual bool OptimizeCall(CallInst *ci, SimplifyLibCalls &SLC) {
1717 if (ConstantInt* CI = dyn_cast<ConstantInt>(ci->getOperand(1))) {
1718 // isdigit(c) -> 0 or 1, if 'c' is constant
1719 uint64_t val = CI->getRawValue();
1720 if (val >= '0' && val <='9')
1721 ci->replaceAllUsesWith(ConstantSInt::get(Type::IntTy,1));
1723 ci->replaceAllUsesWith(ConstantSInt::get(Type::IntTy,0));
1724 ci->eraseFromParent();
1728 // isdigit(c) -> (unsigned)c - '0' <= 9
1730 new CastInst(ci->getOperand(1),Type::UIntTy,
1731 ci->getOperand(1)->getName()+".uint",ci);
1732 BinaryOperator* sub_inst = BinaryOperator::createSub(cast,
1733 ConstantUInt::get(Type::UIntTy,0x30),
1734 ci->getOperand(1)->getName()+".sub",ci);
1735 SetCondInst* setcond_inst = new SetCondInst(Instruction::SetLE,sub_inst,
1736 ConstantUInt::get(Type::UIntTy,9),
1737 ci->getOperand(1)->getName()+".cmp",ci);
1739 new CastInst(setcond_inst,Type::IntTy,
1740 ci->getOperand(1)->getName()+".isdigit",ci);
1741 ci->replaceAllUsesWith(c2);
1742 ci->eraseFromParent();
1747 struct isasciiOptimization : public LibCallOptimization {
1749 isasciiOptimization()
1750 : LibCallOptimization("isascii", "Number of 'isascii' calls simplified") {}
1752 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
1753 return F->arg_size() == 1 && F->arg_begin()->getType()->isInteger() &&
1754 F->getReturnType()->isInteger();
1757 /// @brief Perform the isascii optimization.
1758 virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
1759 // isascii(c) -> (unsigned)c < 128
1760 Value *V = CI->getOperand(1);
1761 if (V->getType()->isSigned())
1762 V = new CastInst(V, V->getType()->getUnsignedVersion(), V->getName(), CI);
1763 Value *Cmp = BinaryOperator::createSetLT(V, ConstantUInt::get(V->getType(),
1765 V->getName()+".isascii", CI);
1766 if (Cmp->getType() != CI->getType())
1767 Cmp = new CastInst(Cmp, CI->getType(), Cmp->getName(), CI);
1768 CI->replaceAllUsesWith(Cmp);
1769 CI->eraseFromParent();
1775 /// This LibCallOptimization will simplify calls to the "toascii" library
1776 /// function. It simply does the corresponding and operation to restrict the
1777 /// range of values to the ASCII character set (0-127).
1778 /// @brief Simplify the toascii library function.
1779 struct ToAsciiOptimization : public LibCallOptimization {
1781 /// @brief Default Constructor
1782 ToAsciiOptimization() : LibCallOptimization("toascii",
1783 "Number of 'toascii' calls simplified") {}
1785 /// @brief Make sure that the "fputs" function has the right prototype
1786 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC){
1787 // Just make sure this has 2 arguments
1788 return (f->arg_size() == 1);
1791 /// @brief Perform the toascii optimization.
1792 virtual bool OptimizeCall(CallInst *ci, SimplifyLibCalls &SLC) {
1793 // toascii(c) -> (c & 0x7f)
1794 Value* chr = ci->getOperand(1);
1795 BinaryOperator* and_inst = BinaryOperator::createAnd(chr,
1796 ConstantInt::get(chr->getType(),0x7F),ci->getName()+".toascii",ci);
1797 ci->replaceAllUsesWith(and_inst);
1798 ci->eraseFromParent();
1803 /// This LibCallOptimization will simplify calls to the "ffs" library
1804 /// calls which find the first set bit in an int, long, or long long. The
1805 /// optimization is to compute the result at compile time if the argument is
1807 /// @brief Simplify the ffs library function.
1808 struct FFSOptimization : public LibCallOptimization {
1810 /// @brief Subclass Constructor
1811 FFSOptimization(const char* funcName, const char* description)
1812 : LibCallOptimization(funcName, description) {}
1815 /// @brief Default Constructor
1816 FFSOptimization() : LibCallOptimization("ffs",
1817 "Number of 'ffs' calls simplified") {}
1819 /// @brief Make sure that the "ffs" function has the right prototype
1820 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
1821 // Just make sure this has 2 arguments
1822 return F->arg_size() == 1 && F->getReturnType() == Type::IntTy;
1825 /// @brief Perform the ffs optimization.
1826 virtual bool OptimizeCall(CallInst *TheCall, SimplifyLibCalls &SLC) {
1827 if (ConstantInt *CI = dyn_cast<ConstantInt>(TheCall->getOperand(1))) {
1828 // ffs(cnst) -> bit#
1829 // ffsl(cnst) -> bit#
1830 // ffsll(cnst) -> bit#
1831 uint64_t val = CI->getRawValue();
1835 while ((val & 1) == 0) {
1840 TheCall->replaceAllUsesWith(ConstantSInt::get(Type::IntTy, result));
1841 TheCall->eraseFromParent();
1845 // ffs(x) -> x == 0 ? 0 : llvm.cttz(x)+1
1846 // ffsl(x) -> x == 0 ? 0 : llvm.cttz(x)+1
1847 // ffsll(x) -> x == 0 ? 0 : llvm.cttz(x)+1
1848 const Type *ArgType = TheCall->getOperand(1)->getType();
1849 ArgType = ArgType->getUnsignedVersion();
1850 const char *CTTZName;
1851 switch (ArgType->getTypeID()) {
1852 default: assert(0 && "Unknown unsigned type!");
1853 case Type::UByteTyID : CTTZName = "llvm.cttz.i8" ; break;
1854 case Type::UShortTyID: CTTZName = "llvm.cttz.i16"; break;
1855 case Type::UIntTyID : CTTZName = "llvm.cttz.i32"; break;
1856 case Type::ULongTyID : CTTZName = "llvm.cttz.i64"; break;
1859 Function *F = SLC.getModule()->getOrInsertFunction(CTTZName, ArgType,
1861 Value *V = new CastInst(TheCall->getOperand(1), ArgType, "tmp", TheCall);
1862 Value *V2 = new CallInst(F, V, "tmp", TheCall);
1863 V2 = new CastInst(V2, Type::IntTy, "tmp", TheCall);
1864 V2 = BinaryOperator::createAdd(V2, ConstantSInt::get(Type::IntTy, 1),
1867 BinaryOperator::createSetEQ(V, Constant::getNullValue(V->getType()),
1869 V2 = new SelectInst(Cond, ConstantInt::get(Type::IntTy, 0), V2,
1870 TheCall->getName(), TheCall);
1871 TheCall->replaceAllUsesWith(V2);
1872 TheCall->eraseFromParent();
1877 /// This LibCallOptimization will simplify calls to the "ffsl" library
1878 /// calls. It simply uses FFSOptimization for which the transformation is
1880 /// @brief Simplify the ffsl library function.
1881 struct FFSLOptimization : public FFSOptimization {
1883 /// @brief Default Constructor
1884 FFSLOptimization() : FFSOptimization("ffsl",
1885 "Number of 'ffsl' calls simplified") {}
1889 /// This LibCallOptimization will simplify calls to the "ffsll" library
1890 /// calls. It simply uses FFSOptimization for which the transformation is
1892 /// @brief Simplify the ffsl library function.
1893 struct FFSLLOptimization : public FFSOptimization {
1895 /// @brief Default Constructor
1896 FFSLLOptimization() : FFSOptimization("ffsll",
1897 "Number of 'ffsll' calls simplified") {}
1901 /// This optimizes unary functions that take and return doubles.
1902 struct UnaryDoubleFPOptimizer : public LibCallOptimization {
1903 UnaryDoubleFPOptimizer(const char *Fn, const char *Desc)
1904 : LibCallOptimization(Fn, Desc) {}
1906 // Make sure that this function has the right prototype
1907 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
1908 return F->arg_size() == 1 && F->arg_begin()->getType() == Type::DoubleTy &&
1909 F->getReturnType() == Type::DoubleTy;
1912 /// ShrinkFunctionToFloatVersion - If the input to this function is really a
1913 /// float, strength reduce this to a float version of the function,
1914 /// e.g. floor((double)FLT) -> (double)floorf(FLT). This can only be called
1915 /// when the target supports the destination function and where there can be
1916 /// no precision loss.
1917 static bool ShrinkFunctionToFloatVersion(CallInst *CI, SimplifyLibCalls &SLC,
1918 Function *(SimplifyLibCalls::*FP)()){
1919 if (CastInst *Cast = dyn_cast<CastInst>(CI->getOperand(1)))
1920 if (Cast->getOperand(0)->getType() == Type::FloatTy) {
1921 Value *New = new CallInst((SLC.*FP)(), Cast->getOperand(0),
1923 New = new CastInst(New, Type::DoubleTy, CI->getName(), CI);
1924 CI->replaceAllUsesWith(New);
1925 CI->eraseFromParent();
1926 if (Cast->use_empty())
1927 Cast->eraseFromParent();
1935 struct FloorOptimization : public UnaryDoubleFPOptimizer {
1937 : UnaryDoubleFPOptimizer("floor", "Number of 'floor' calls simplified") {}
1939 virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
1941 // If this is a float argument passed in, convert to floorf.
1942 if (ShrinkFunctionToFloatVersion(CI, SLC, &SimplifyLibCalls::get_floorf))
1945 return false; // opt failed
1949 struct CeilOptimization : public UnaryDoubleFPOptimizer {
1951 : UnaryDoubleFPOptimizer("ceil", "Number of 'ceil' calls simplified") {}
1953 virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
1955 // If this is a float argument passed in, convert to ceilf.
1956 if (ShrinkFunctionToFloatVersion(CI, SLC, &SimplifyLibCalls::get_ceilf))
1959 return false; // opt failed
1963 struct RoundOptimization : public UnaryDoubleFPOptimizer {
1965 : UnaryDoubleFPOptimizer("round", "Number of 'round' calls simplified") {}
1967 virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
1969 // If this is a float argument passed in, convert to roundf.
1970 if (ShrinkFunctionToFloatVersion(CI, SLC, &SimplifyLibCalls::get_roundf))
1973 return false; // opt failed
1977 struct RintOptimization : public UnaryDoubleFPOptimizer {
1979 : UnaryDoubleFPOptimizer("rint", "Number of 'rint' calls simplified") {}
1981 virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
1983 // If this is a float argument passed in, convert to rintf.
1984 if (ShrinkFunctionToFloatVersion(CI, SLC, &SimplifyLibCalls::get_rintf))
1987 return false; // opt failed
1991 struct NearByIntOptimization : public UnaryDoubleFPOptimizer {
1992 NearByIntOptimization()
1993 : UnaryDoubleFPOptimizer("nearbyint",
1994 "Number of 'nearbyint' calls simplified") {}
1996 virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
1997 #ifdef HAVE_NEARBYINTF
1998 // If this is a float argument passed in, convert to nearbyintf.
1999 if (ShrinkFunctionToFloatVersion(CI, SLC,&SimplifyLibCalls::get_nearbyintf))
2002 return false; // opt failed
2004 } NearByIntOptimizer;
2006 /// A function to compute the length of a null-terminated constant array of
2007 /// integers. This function can't rely on the size of the constant array
2008 /// because there could be a null terminator in the middle of the array.
2009 /// We also have to bail out if we find a non-integer constant initializer
2010 /// of one of the elements or if there is no null-terminator. The logic
2011 /// below checks each of these conditions and will return true only if all
2012 /// conditions are met. In that case, the \p len parameter is set to the length
2013 /// of the null-terminated string. If false is returned, the conditions were
2014 /// not met and len is set to 0.
2015 /// @brief Get the length of a constant string (null-terminated array).
2016 bool getConstantStringLength(Value *V, uint64_t &len, ConstantArray **CA) {
2017 assert(V != 0 && "Invalid args to getConstantStringLength");
2018 len = 0; // make sure we initialize this
2020 // If the value is not a GEP instruction nor a constant expression with a
2021 // GEP instruction, then return false because ConstantArray can't occur
2023 if (GetElementPtrInst* GEPI = dyn_cast<GetElementPtrInst>(V))
2025 else if (ConstantExpr* CE = dyn_cast<ConstantExpr>(V))
2026 if (CE->getOpcode() == Instruction::GetElementPtr)
2033 // Make sure the GEP has exactly three arguments.
2034 if (GEP->getNumOperands() != 3)
2037 // Check to make sure that the first operand of the GEP is an integer and
2038 // has value 0 so that we are sure we're indexing into the initializer.
2039 if (ConstantInt* op1 = dyn_cast<ConstantInt>(GEP->getOperand(1))) {
2040 if (!op1->isNullValue())
2045 // Ensure that the second operand is a ConstantInt. If it isn't then this
2046 // GEP is wonky and we're not really sure what were referencing into and
2047 // better of not optimizing it. While we're at it, get the second index
2048 // value. We'll need this later for indexing the ConstantArray.
2049 uint64_t start_idx = 0;
2050 if (ConstantInt* CI = dyn_cast<ConstantInt>(GEP->getOperand(2)))
2051 start_idx = CI->getRawValue();
2055 // The GEP instruction, constant or instruction, must reference a global
2056 // variable that is a constant and is initialized. The referenced constant
2057 // initializer is the array that we'll use for optimization.
2058 GlobalVariable* GV = dyn_cast<GlobalVariable>(GEP->getOperand(0));
2059 if (!GV || !GV->isConstant() || !GV->hasInitializer())
2062 // Get the initializer.
2063 Constant* INTLZR = GV->getInitializer();
2065 // Handle the ConstantAggregateZero case
2066 if (ConstantAggregateZero *CAZ = dyn_cast<ConstantAggregateZero>(INTLZR)) {
2067 // This is a degenerate case. The initializer is constant zero so the
2068 // length of the string must be zero.
2073 // Must be a Constant Array
2074 ConstantArray* A = dyn_cast<ConstantArray>(INTLZR);
2078 // Get the number of elements in the array
2079 uint64_t max_elems = A->getType()->getNumElements();
2081 // Traverse the constant array from start_idx (derived above) which is
2082 // the place the GEP refers to in the array.
2083 for (len = start_idx; len < max_elems; len++) {
2084 if (ConstantInt *CI = dyn_cast<ConstantInt>(A->getOperand(len))) {
2085 // Check for the null terminator
2086 if (CI->isNullValue())
2087 break; // we found end of string
2089 return false; // This array isn't suitable, non-int initializer
2092 if (len >= max_elems)
2093 return false; // This array isn't null terminated
2095 // Subtract out the initial value from the length
2099 return true; // success!
2102 /// CastToCStr - Return V if it is an sbyte*, otherwise cast it to sbyte*,
2103 /// inserting the cast before IP, and return the cast.
2104 /// @brief Cast a value to a "C" string.
2105 Value *CastToCStr(Value *V, Instruction &IP) {
2106 const Type *SBPTy = PointerType::get(Type::SByteTy);
2107 if (V->getType() != SBPTy)
2108 return new CastInst(V, SBPTy, V->getName(), &IP);
2113 // Additional cases that we need to add to this file:
2116 // * cbrt(expN(X)) -> expN(x/3)
2117 // * cbrt(sqrt(x)) -> pow(x,1/6)
2118 // * cbrt(sqrt(x)) -> pow(x,1/9)
2121 // * cos(-x) -> cos(x)
2124 // * exp(log(x)) -> x
2127 // * log(exp(x)) -> x
2128 // * log(x**y) -> y*log(x)
2129 // * log(exp(y)) -> y*log(e)
2130 // * log(exp2(y)) -> y*log(2)
2131 // * log(exp10(y)) -> y*log(10)
2132 // * log(sqrt(x)) -> 0.5*log(x)
2133 // * log(pow(x,y)) -> y*log(x)
2135 // lround, lroundf, lroundl:
2136 // * lround(cnst) -> cnst'
2139 // * memcmp(x,y,l) -> cnst
2140 // (if all arguments are constant and strlen(x) <= l and strlen(y) <= l)
2143 // * memmove(d,s,l,a) -> memcpy(d,s,l,a)
2144 // (if s is a global constant array)
2147 // * pow(exp(x),y) -> exp(x*y)
2148 // * pow(sqrt(x),y) -> pow(x,y*0.5)
2149 // * pow(pow(x,y),z)-> pow(x,y*z)
2152 // * puts("") -> fputc("\n",stdout) (how do we get "stdout"?)
2154 // round, roundf, roundl:
2155 // * round(cnst) -> cnst'
2158 // * signbit(cnst) -> cnst'
2159 // * signbit(nncst) -> 0 (if pstv is a non-negative constant)
2161 // sqrt, sqrtf, sqrtl:
2162 // * sqrt(expN(x)) -> expN(x*0.5)
2163 // * sqrt(Nroot(x)) -> pow(x,1/(2*N))
2164 // * sqrt(pow(x,y)) -> pow(|x|,y*0.5)
2167 // * stpcpy(str, "literal") ->
2168 // llvm.memcpy(str,"literal",strlen("literal")+1,1)
2170 // * strrchr(s,c) -> reverse_offset_of_in(c,s)
2171 // (if c is a constant integer and s is a constant string)
2172 // * strrchr(s1,0) -> strchr(s1,0)
2175 // * strncat(x,y,0) -> x
2176 // * strncat(x,y,0) -> x (if strlen(y) = 0)
2177 // * strncat(x,y,l) -> strcat(x,y) (if y and l are constants an l > strlen(y))
2180 // * strncpy(d,s,0) -> d
2181 // * strncpy(d,s,l) -> memcpy(d,s,l,1)
2182 // (if s and l are constants)
2185 // * strpbrk(s,a) -> offset_in_for(s,a)
2186 // (if s and a are both constant strings)
2187 // * strpbrk(s,"") -> 0
2188 // * strpbrk(s,a) -> strchr(s,a[0]) (if a is constant string of length 1)
2191 // * strspn(s,a) -> const_int (if both args are constant)
2192 // * strspn("",a) -> 0
2193 // * strspn(s,"") -> 0
2194 // * strcspn(s,a) -> const_int (if both args are constant)
2195 // * strcspn("",a) -> 0
2196 // * strcspn(s,"") -> strlen(a)
2199 // * strstr(x,x) -> x
2200 // * strstr(s1,s2) -> offset_of_s2_in(s1)
2201 // (if s1 and s2 are constant strings)
2204 // * tan(atan(x)) -> x
2206 // trunc, truncf, truncl:
2207 // * trunc(cnst) -> cnst'