1 //===- SimplifyLibCalls.cpp - Optimize specific well-known library calls --===//
3 // The LLVM Compiler Infrastructure
5 // This file was developed by Reid Spencer and is distributed under the
6 // University of Illinois Open Source License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file implements a module pass that applies a variety of small
11 // optimizations for calls to specific well-known function calls (e.g. runtime
12 // library functions). For example, a call to the function "exit(3)" that
13 // occurs within the main() function can be transformed into a simple "return 3"
14 // instruction. Any optimization that takes this form (replace call to library
15 // function with simpler code that provides the same result) belongs in this
18 //===----------------------------------------------------------------------===//
20 #define DEBUG_TYPE "simplify-libcalls"
21 #include "llvm/Constants.h"
22 #include "llvm/DerivedTypes.h"
23 #include "llvm/Instructions.h"
24 #include "llvm/Module.h"
25 #include "llvm/Pass.h"
26 #include "llvm/ADT/hash_map"
27 #include "llvm/ADT/Statistic.h"
28 #include "llvm/Config/config.h"
29 #include "llvm/Support/Debug.h"
30 #include "llvm/Target/TargetData.h"
31 #include "llvm/Transforms/IPO.h"
36 /// This statistic keeps track of the total number of library calls that have
37 /// been simplified regardless of which call it is.
38 Statistic<> SimplifiedLibCalls("simplify-libcalls",
39 "Number of library calls simplified");
41 // Forward declarations
42 class LibCallOptimization;
43 class SimplifyLibCalls;
45 /// This list is populated by the constructor for LibCallOptimization class.
46 /// Therefore all subclasses are registered here at static initialization time
47 /// and this list is what the SimplifyLibCalls pass uses to apply the individual
48 /// optimizations to the call sites.
49 /// @brief The list of optimizations deriving from LibCallOptimization
50 static LibCallOptimization *OptList = 0;
52 /// This class is the abstract base class for the set of optimizations that
53 /// corresponds to one library call. The SimplifyLibCalls pass will call the
54 /// ValidateCalledFunction method to ask the optimization if a given Function
55 /// is the kind that the optimization can handle. If the subclass returns true,
56 /// then SImplifyLibCalls will also call the OptimizeCall method to perform,
57 /// or attempt to perform, the optimization(s) for the library call. Otherwise,
58 /// OptimizeCall won't be called. Subclasses are responsible for providing the
59 /// name of the library call (strlen, strcpy, etc.) to the LibCallOptimization
60 /// constructor. This is used to efficiently select which call instructions to
61 /// optimize. The criteria for a "lib call" is "anything with well known
62 /// semantics", typically a library function that is defined by an international
63 /// standard. Because the semantics are well known, the optimizations can
64 /// generally short-circuit actually calling the function if there's a simpler
65 /// way (e.g. strlen(X) can be reduced to a constant if X is a constant global).
66 /// @brief Base class for library call optimizations
67 class LibCallOptimization {
68 LibCallOptimization **Prev, *Next;
69 const char *FunctionName; ///< Name of the library call we optimize
71 Statistic<> occurrences; ///< debug statistic (-debug-only=simplify-libcalls)
74 /// The \p fname argument must be the name of the library function being
75 /// optimized by the subclass.
76 /// @brief Constructor that registers the optimization.
77 LibCallOptimization(const char *FName, const char *Description)
80 , occurrences("simplify-libcalls", Description)
83 // Register this optimizer in the list of optimizations.
87 if (Next) Next->Prev = &Next;
90 /// getNext - All libcall optimizations are chained together into a list,
91 /// return the next one in the list.
92 LibCallOptimization *getNext() { return Next; }
94 /// @brief Deregister from the optlist
95 virtual ~LibCallOptimization() {
97 if (Next) Next->Prev = Prev;
100 /// The implementation of this function in subclasses should determine if
101 /// \p F is suitable for the optimization. This method is called by
102 /// SimplifyLibCalls::runOnModule to short circuit visiting all the call
103 /// sites of such a function if that function is not suitable in the first
104 /// place. If the called function is suitabe, this method should return true;
105 /// false, otherwise. This function should also perform any lazy
106 /// initialization that the LibCallOptimization needs to do, if its to return
107 /// true. This avoids doing initialization until the optimizer is actually
108 /// going to be called upon to do some optimization.
109 /// @brief Determine if the function is suitable for optimization
110 virtual bool ValidateCalledFunction(
111 const Function* F, ///< The function that is the target of call sites
112 SimplifyLibCalls& SLC ///< The pass object invoking us
115 /// The implementations of this function in subclasses is the heart of the
116 /// SimplifyLibCalls algorithm. Sublcasses of this class implement
117 /// OptimizeCall to determine if (a) the conditions are right for optimizing
118 /// the call and (b) to perform the optimization. If an action is taken
119 /// against ci, the subclass is responsible for returning true and ensuring
120 /// that ci is erased from its parent.
121 /// @brief Optimize a call, if possible.
122 virtual bool OptimizeCall(
123 CallInst* ci, ///< The call instruction that should be optimized.
124 SimplifyLibCalls& SLC ///< The pass object invoking us
127 /// @brief Get the name of the library call being optimized
128 const char *getFunctionName() const { return FunctionName; }
130 /// @brief Called by SimplifyLibCalls to update the occurrences statistic.
133 DEBUG(++occurrences);
138 /// This class is an LLVM Pass that applies each of the LibCallOptimization
139 /// instances to all the call sites in a module, relatively efficiently. The
140 /// purpose of this pass is to provide optimizations for calls to well-known
141 /// functions with well-known semantics, such as those in the c library. The
142 /// class provides the basic infrastructure for handling runOnModule. Whenever
143 /// this pass finds a function call, it asks the appropriate optimizer to
144 /// validate the call (ValidateLibraryCall). If it is validated, then
145 /// the OptimizeCall method is also called.
146 /// @brief A ModulePass for optimizing well-known function calls.
147 class SimplifyLibCalls : public ModulePass {
149 /// We need some target data for accurate signature details that are
150 /// target dependent. So we require target data in our AnalysisUsage.
151 /// @brief Require TargetData from AnalysisUsage.
152 virtual void getAnalysisUsage(AnalysisUsage& Info) const {
153 // Ask that the TargetData analysis be performed before us so we can use
155 Info.addRequired<TargetData>();
158 /// For this pass, process all of the function calls in the module, calling
159 /// ValidateLibraryCall and OptimizeCall as appropriate.
160 /// @brief Run all the lib call optimizations on a Module.
161 virtual bool runOnModule(Module &M) {
165 hash_map<std::string, LibCallOptimization*> OptznMap;
166 for (LibCallOptimization *Optzn = OptList; Optzn; Optzn = Optzn->getNext())
167 OptznMap[Optzn->getFunctionName()] = Optzn;
169 // The call optimizations can be recursive. That is, the optimization might
170 // generate a call to another function which can also be optimized. This way
171 // we make the LibCallOptimization instances very specific to the case they
172 // handle. It also means we need to keep running over the function calls in
173 // the module until we don't get any more optimizations possible.
174 bool found_optimization = false;
176 found_optimization = false;
177 for (Module::iterator FI = M.begin(), FE = M.end(); FI != FE; ++FI) {
178 // All the "well-known" functions are external and have external linkage
179 // because they live in a runtime library somewhere and were (probably)
180 // not compiled by LLVM. So, we only act on external functions that
181 // have external linkage and non-empty uses.
182 if (!FI->isExternal() || !FI->hasExternalLinkage() || FI->use_empty())
185 // Get the optimization class that pertains to this function
186 hash_map<std::string, LibCallOptimization*>::iterator OMI =
187 OptznMap.find(FI->getName());
188 if (OMI == OptznMap.end()) continue;
190 LibCallOptimization *CO = OMI->second;
192 // Make sure the called function is suitable for the optimization
193 if (!CO->ValidateCalledFunction(FI, *this))
196 // Loop over each of the uses of the function
197 for (Value::use_iterator UI = FI->use_begin(), UE = FI->use_end();
199 // If the use of the function is a call instruction
200 if (CallInst* CI = dyn_cast<CallInst>(*UI++)) {
201 // Do the optimization on the LibCallOptimization.
202 if (CO->OptimizeCall(CI, *this)) {
203 ++SimplifiedLibCalls;
204 found_optimization = result = true;
210 } while (found_optimization);
215 /// @brief Return the *current* module we're working on.
216 Module* getModule() const { return M; }
218 /// @brief Return the *current* target data for the module we're working on.
219 TargetData* getTargetData() const { return TD; }
221 /// @brief Return the size_t type -- syntactic shortcut
222 const Type* getIntPtrType() const { return TD->getIntPtrType(); }
224 /// @brief Return a Function* for the fputc libcall
225 Function* get_fputc(const Type* FILEptr_type) {
227 fputc_func = M->getOrInsertFunction("fputc", Type::IntTy, Type::IntTy,
232 /// @brief Return a Function* for the fwrite libcall
233 Function* get_fwrite(const Type* FILEptr_type) {
235 fwrite_func = M->getOrInsertFunction("fwrite", TD->getIntPtrType(),
236 PointerType::get(Type::SByteTy),
243 /// @brief Return a Function* for the sqrt libcall
244 Function* get_sqrt() {
246 sqrt_func = M->getOrInsertFunction("sqrt", Type::DoubleTy,
247 Type::DoubleTy, NULL);
251 /// @brief Return a Function* for the strlen libcall
252 Function* get_strcpy() {
254 strcpy_func = M->getOrInsertFunction("strcpy",
255 PointerType::get(Type::SByteTy),
256 PointerType::get(Type::SByteTy),
257 PointerType::get(Type::SByteTy),
262 /// @brief Return a Function* for the strlen libcall
263 Function* get_strlen() {
265 strlen_func = M->getOrInsertFunction("strlen", TD->getIntPtrType(),
266 PointerType::get(Type::SByteTy),
271 /// @brief Return a Function* for the memchr libcall
272 Function* get_memchr() {
274 memchr_func = M->getOrInsertFunction("memchr",
275 PointerType::get(Type::SByteTy),
276 PointerType::get(Type::SByteTy),
277 Type::IntTy, TD->getIntPtrType(),
282 /// @brief Return a Function* for the memcpy libcall
283 Function* get_memcpy() {
285 const Type *SBP = PointerType::get(Type::SByteTy);
286 memcpy_func = M->getOrInsertFunction("llvm.memcpy", Type::VoidTy,SBP, SBP,
287 Type::UIntTy, Type::UIntTy, NULL);
292 Function* get_floorf() {
294 floorf_func = M->getOrInsertFunction("floorf", Type::FloatTy,
295 Type::FloatTy, NULL);
300 /// @brief Reset our cached data for a new Module
301 void reset(Module& mod) {
303 TD = &getAnalysis<TargetData>();
315 Function* fputc_func; ///< Cached fputc function
316 Function* fwrite_func; ///< Cached fwrite function
317 Function* memcpy_func; ///< Cached llvm.memcpy function
318 Function* memchr_func; ///< Cached memchr function
319 Function* sqrt_func; ///< Cached sqrt function
320 Function* strcpy_func; ///< Cached strcpy function
321 Function* strlen_func; ///< Cached strlen function
322 Function* floorf_func; ///< Cached floorf function
323 Module* M; ///< Cached Module
324 TargetData* TD; ///< Cached TargetData
328 RegisterOpt<SimplifyLibCalls>
329 X("simplify-libcalls","Simplify well-known library calls");
331 } // anonymous namespace
333 // The only public symbol in this file which just instantiates the pass object
334 ModulePass *llvm::createSimplifyLibCallsPass() {
335 return new SimplifyLibCalls();
338 // Classes below here, in the anonymous namespace, are all subclasses of the
339 // LibCallOptimization class, each implementing all optimizations possible for a
340 // single well-known library call. Each has a static singleton instance that
341 // auto registers it into the "optlist" global above.
344 // Forward declare utility functions.
345 bool getConstantStringLength(Value* V, uint64_t& len, ConstantArray** A = 0 );
346 Value *CastToCStr(Value *V, Instruction &IP);
348 /// This LibCallOptimization will find instances of a call to "exit" that occurs
349 /// within the "main" function and change it to a simple "ret" instruction with
350 /// the same value passed to the exit function. When this is done, it splits the
351 /// basic block at the exit(3) call and deletes the call instruction.
352 /// @brief Replace calls to exit in main with a simple return
353 struct ExitInMainOptimization : public LibCallOptimization {
354 ExitInMainOptimization() : LibCallOptimization("exit",
355 "Number of 'exit' calls simplified") {}
357 // Make sure the called function looks like exit (int argument, int return
358 // type, external linkage, not varargs).
359 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
360 return F->arg_size() >= 1 && F->arg_begin()->getType()->isInteger();
363 virtual bool OptimizeCall(CallInst* ci, SimplifyLibCalls& SLC) {
364 // To be careful, we check that the call to exit is coming from "main", that
365 // main has external linkage, and the return type of main and the argument
366 // to exit have the same type.
367 Function *from = ci->getParent()->getParent();
368 if (from->hasExternalLinkage())
369 if (from->getReturnType() == ci->getOperand(1)->getType())
370 if (from->getName() == "main") {
371 // Okay, time to actually do the optimization. First, get the basic
372 // block of the call instruction
373 BasicBlock* bb = ci->getParent();
375 // Create a return instruction that we'll replace the call with.
376 // Note that the argument of the return is the argument of the call
378 ReturnInst* ri = new ReturnInst(ci->getOperand(1), ci);
380 // Split the block at the call instruction which places it in a new
382 bb->splitBasicBlock(ci);
384 // The block split caused a branch instruction to be inserted into
385 // the end of the original block, right after the return instruction
386 // that we put there. That's not a valid block, so delete the branch
388 bb->getInstList().pop_back();
390 // Now we can finally get rid of the call instruction which now lives
391 // in the new basic block.
392 ci->eraseFromParent();
394 // Optimization succeeded, return true.
397 // We didn't pass the criteria for this optimization so return false
400 } ExitInMainOptimizer;
402 /// This LibCallOptimization will simplify a call to the strcat library
403 /// function. The simplification is possible only if the string being
404 /// concatenated is a constant array or a constant expression that results in
405 /// a constant string. In this case we can replace it with strlen + llvm.memcpy
406 /// of the constant string. Both of these calls are further reduced, if possible
407 /// on subsequent passes.
408 /// @brief Simplify the strcat library function.
409 struct StrCatOptimization : public LibCallOptimization {
411 /// @brief Default constructor
412 StrCatOptimization() : LibCallOptimization("strcat",
413 "Number of 'strcat' calls simplified") {}
417 /// @brief Make sure that the "strcat" function has the right prototype
418 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC){
419 if (f->getReturnType() == PointerType::get(Type::SByteTy))
420 if (f->arg_size() == 2)
422 Function::const_arg_iterator AI = f->arg_begin();
423 if (AI++->getType() == PointerType::get(Type::SByteTy))
424 if (AI->getType() == PointerType::get(Type::SByteTy))
426 // Indicate this is a suitable call type.
433 /// @brief Optimize the strcat library function
434 virtual bool OptimizeCall(CallInst* ci, SimplifyLibCalls& SLC) {
435 // Extract some information from the instruction
436 Module* M = ci->getParent()->getParent()->getParent();
437 Value* dest = ci->getOperand(1);
438 Value* src = ci->getOperand(2);
440 // Extract the initializer (while making numerous checks) from the
441 // source operand of the call to strcat. If we get null back, one of
442 // a variety of checks in get_GVInitializer failed
444 if (!getConstantStringLength(src,len))
447 // Handle the simple, do-nothing case
449 ci->replaceAllUsesWith(dest);
450 ci->eraseFromParent();
454 // Increment the length because we actually want to memcpy the null
455 // terminator as well.
458 // We need to find the end of the destination string. That's where the
459 // memory is to be moved to. We just generate a call to strlen (further
460 // optimized in another pass). Note that the SLC.get_strlen() call
461 // caches the Function* for us.
462 CallInst* strlen_inst =
463 new CallInst(SLC.get_strlen(), dest, dest->getName()+".len",ci);
465 // Now that we have the destination's length, we must index into the
466 // destination's pointer to get the actual memcpy destination (end of
467 // the string .. we're concatenating).
468 std::vector<Value*> idx;
469 idx.push_back(strlen_inst);
470 GetElementPtrInst* gep =
471 new GetElementPtrInst(dest,idx,dest->getName()+".indexed",ci);
473 // We have enough information to now generate the memcpy call to
474 // do the concatenation for us.
475 std::vector<Value*> vals;
476 vals.push_back(gep); // destination
477 vals.push_back(ci->getOperand(2)); // source
478 vals.push_back(ConstantUInt::get(Type::UIntTy,len)); // length
479 vals.push_back(ConstantUInt::get(Type::UIntTy,1)); // alignment
480 new CallInst(SLC.get_memcpy(), vals, "", ci);
482 // Finally, substitute the first operand of the strcat call for the
483 // strcat call itself since strcat returns its first operand; and,
484 // kill the strcat CallInst.
485 ci->replaceAllUsesWith(dest);
486 ci->eraseFromParent();
491 /// This LibCallOptimization will simplify a call to the strchr library
492 /// function. It optimizes out cases where the arguments are both constant
493 /// and the result can be determined statically.
494 /// @brief Simplify the strcmp library function.
495 struct StrChrOptimization : public LibCallOptimization {
497 StrChrOptimization() : LibCallOptimization("strchr",
498 "Number of 'strchr' calls simplified") {}
500 /// @brief Make sure that the "strchr" function has the right prototype
501 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC){
502 if (f->getReturnType() == PointerType::get(Type::SByteTy) &&
508 /// @brief Perform the strchr optimizations
509 virtual bool OptimizeCall(CallInst *ci, SimplifyLibCalls &SLC) {
510 // If there aren't three operands, bail
511 if (ci->getNumOperands() != 3)
514 // Check that the first argument to strchr is a constant array of sbyte.
515 // If it is, get the length and data, otherwise return false.
518 if (!getConstantStringLength(ci->getOperand(1),len,&CA))
521 // Check that the second argument to strchr is a constant int, return false
523 ConstantSInt* CSI = dyn_cast<ConstantSInt>(ci->getOperand(2));
525 // Just lower this to memchr since we know the length of the string as
527 Function* f = SLC.get_memchr();
528 std::vector<Value*> args;
529 args.push_back(ci->getOperand(1));
530 args.push_back(ci->getOperand(2));
531 args.push_back(ConstantUInt::get(SLC.getIntPtrType(),len));
532 ci->replaceAllUsesWith( new CallInst(f,args,ci->getName(),ci));
533 ci->eraseFromParent();
537 // Get the character we're looking for
538 int64_t chr = CSI->getValue();
540 // Compute the offset
542 bool char_found = false;
543 for (uint64_t i = 0; i < len; ++i) {
544 if (ConstantSInt* CI = dyn_cast<ConstantSInt>(CA->getOperand(i))) {
545 // Check for the null terminator
546 if (CI->isNullValue())
547 break; // we found end of string
548 else if (CI->getValue() == chr) {
556 // strchr(s,c) -> offset_of_in(c,s)
557 // (if c is a constant integer and s is a constant string)
559 std::vector<Value*> indices;
560 indices.push_back(ConstantUInt::get(Type::ULongTy,offset));
561 GetElementPtrInst* GEP = new GetElementPtrInst(ci->getOperand(1),indices,
562 ci->getOperand(1)->getName()+".strchr",ci);
563 ci->replaceAllUsesWith(GEP);
565 ci->replaceAllUsesWith(
566 ConstantPointerNull::get(PointerType::get(Type::SByteTy)));
568 ci->eraseFromParent();
573 /// This LibCallOptimization will simplify a call to the strcmp library
574 /// function. It optimizes out cases where one or both arguments are constant
575 /// and the result can be determined statically.
576 /// @brief Simplify the strcmp library function.
577 struct StrCmpOptimization : public LibCallOptimization {
579 StrCmpOptimization() : LibCallOptimization("strcmp",
580 "Number of 'strcmp' calls simplified") {}
582 /// @brief Make sure that the "strcmp" function has the right prototype
583 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
584 return F->getReturnType() == Type::IntTy && F->arg_size() == 2;
587 /// @brief Perform the strcmp optimization
588 virtual bool OptimizeCall(CallInst* ci, SimplifyLibCalls& SLC) {
589 // First, check to see if src and destination are the same. If they are,
590 // then the optimization is to replace the CallInst with a constant 0
591 // because the call is a no-op.
592 Value* s1 = ci->getOperand(1);
593 Value* s2 = ci->getOperand(2);
596 ci->replaceAllUsesWith(ConstantInt::get(Type::IntTy,0));
597 ci->eraseFromParent();
601 bool isstr_1 = false;
604 if (getConstantStringLength(s1,len_1,&A1)) {
607 // strcmp("",x) -> *x
609 new LoadInst(CastToCStr(s2,*ci), ci->getName()+".load",ci);
611 new CastInst(load,Type::IntTy,ci->getName()+".int",ci);
612 ci->replaceAllUsesWith(cast);
613 ci->eraseFromParent();
618 bool isstr_2 = false;
621 if (getConstantStringLength(s2, len_2, &A2)) {
624 // strcmp(x,"") -> *x
626 new LoadInst(CastToCStr(s1,*ci),ci->getName()+".val",ci);
628 new CastInst(load,Type::IntTy,ci->getName()+".int",ci);
629 ci->replaceAllUsesWith(cast);
630 ci->eraseFromParent();
635 if (isstr_1 && isstr_2) {
636 // strcmp(x,y) -> cnst (if both x and y are constant strings)
637 std::string str1 = A1->getAsString();
638 std::string str2 = A2->getAsString();
639 int result = strcmp(str1.c_str(), str2.c_str());
640 ci->replaceAllUsesWith(ConstantSInt::get(Type::IntTy,result));
641 ci->eraseFromParent();
648 /// This LibCallOptimization will simplify a call to the strncmp library
649 /// function. It optimizes out cases where one or both arguments are constant
650 /// and the result can be determined statically.
651 /// @brief Simplify the strncmp library function.
652 struct StrNCmpOptimization : public LibCallOptimization {
654 StrNCmpOptimization() : LibCallOptimization("strncmp",
655 "Number of 'strncmp' calls simplified") {}
657 /// @brief Make sure that the "strncmp" function has the right prototype
658 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC){
659 if (f->getReturnType() == Type::IntTy && f->arg_size() == 3)
664 /// @brief Perform the strncpy optimization
665 virtual bool OptimizeCall(CallInst *ci, SimplifyLibCalls &SLC) {
666 // First, check to see if src and destination are the same. If they are,
667 // then the optimization is to replace the CallInst with a constant 0
668 // because the call is a no-op.
669 Value* s1 = ci->getOperand(1);
670 Value* s2 = ci->getOperand(2);
672 // strncmp(x,x,l) -> 0
673 ci->replaceAllUsesWith(ConstantInt::get(Type::IntTy,0));
674 ci->eraseFromParent();
678 // Check the length argument, if it is Constant zero then the strings are
680 uint64_t len_arg = 0;
681 bool len_arg_is_const = false;
682 if (ConstantInt* len_CI = dyn_cast<ConstantInt>(ci->getOperand(3))) {
683 len_arg_is_const = true;
684 len_arg = len_CI->getRawValue();
686 // strncmp(x,y,0) -> 0
687 ci->replaceAllUsesWith(ConstantInt::get(Type::IntTy,0));
688 ci->eraseFromParent();
693 bool isstr_1 = false;
696 if (getConstantStringLength(s1, len_1, &A1)) {
699 // strncmp("",x) -> *x
700 LoadInst* load = new LoadInst(s1,ci->getName()+".load",ci);
702 new CastInst(load,Type::IntTy,ci->getName()+".int",ci);
703 ci->replaceAllUsesWith(cast);
704 ci->eraseFromParent();
709 bool isstr_2 = false;
712 if (getConstantStringLength(s2,len_2,&A2)) {
715 // strncmp(x,"") -> *x
716 LoadInst* load = new LoadInst(s2,ci->getName()+".val",ci);
718 new CastInst(load,Type::IntTy,ci->getName()+".int",ci);
719 ci->replaceAllUsesWith(cast);
720 ci->eraseFromParent();
725 if (isstr_1 && isstr_2 && len_arg_is_const) {
726 // strncmp(x,y,const) -> constant
727 std::string str1 = A1->getAsString();
728 std::string str2 = A2->getAsString();
729 int result = strncmp(str1.c_str(), str2.c_str(), len_arg);
730 ci->replaceAllUsesWith(ConstantSInt::get(Type::IntTy,result));
731 ci->eraseFromParent();
738 /// This LibCallOptimization will simplify a call to the strcpy library
739 /// function. Two optimizations are possible:
740 /// (1) If src and dest are the same and not volatile, just return dest
741 /// (2) If the src is a constant then we can convert to llvm.memmove
742 /// @brief Simplify the strcpy library function.
743 struct StrCpyOptimization : public LibCallOptimization {
745 StrCpyOptimization() : LibCallOptimization("strcpy",
746 "Number of 'strcpy' calls simplified") {}
748 /// @brief Make sure that the "strcpy" function has the right prototype
749 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC){
750 if (f->getReturnType() == PointerType::get(Type::SByteTy))
751 if (f->arg_size() == 2) {
752 Function::const_arg_iterator AI = f->arg_begin();
753 if (AI++->getType() == PointerType::get(Type::SByteTy))
754 if (AI->getType() == PointerType::get(Type::SByteTy)) {
755 // Indicate this is a suitable call type.
762 /// @brief Perform the strcpy optimization
763 virtual bool OptimizeCall(CallInst* ci, SimplifyLibCalls& SLC) {
764 // First, check to see if src and destination are the same. If they are,
765 // then the optimization is to replace the CallInst with the destination
766 // because the call is a no-op. Note that this corresponds to the
767 // degenerate strcpy(X,X) case which should have "undefined" results
768 // according to the C specification. However, it occurs sometimes and
769 // we optimize it as a no-op.
770 Value* dest = ci->getOperand(1);
771 Value* src = ci->getOperand(2);
773 ci->replaceAllUsesWith(dest);
774 ci->eraseFromParent();
778 // Get the length of the constant string referenced by the second operand,
779 // the "src" parameter. Fail the optimization if we can't get the length
780 // (note that getConstantStringLength does lots of checks to make sure this
783 if (!getConstantStringLength(ci->getOperand(2),len))
786 // If the constant string's length is zero we can optimize this by just
787 // doing a store of 0 at the first byte of the destination
789 new StoreInst(ConstantInt::get(Type::SByteTy,0),ci->getOperand(1),ci);
790 ci->replaceAllUsesWith(dest);
791 ci->eraseFromParent();
795 // Increment the length because we actually want to memcpy the null
796 // terminator as well.
799 // Extract some information from the instruction
800 Module* M = ci->getParent()->getParent()->getParent();
802 // We have enough information to now generate the memcpy call to
803 // do the concatenation for us.
804 std::vector<Value*> vals;
805 vals.push_back(dest); // destination
806 vals.push_back(src); // source
807 vals.push_back(ConstantUInt::get(Type::UIntTy,len)); // length
808 vals.push_back(ConstantUInt::get(Type::UIntTy,1)); // alignment
809 new CallInst(SLC.get_memcpy(), vals, "", ci);
811 // Finally, substitute the first operand of the strcat call for the
812 // strcat call itself since strcat returns its first operand; and,
813 // kill the strcat CallInst.
814 ci->replaceAllUsesWith(dest);
815 ci->eraseFromParent();
820 /// This LibCallOptimization will simplify a call to the strlen library
821 /// function by replacing it with a constant value if the string provided to
822 /// it is a constant array.
823 /// @brief Simplify the strlen library function.
824 struct StrLenOptimization : public LibCallOptimization {
825 StrLenOptimization() : LibCallOptimization("strlen",
826 "Number of 'strlen' calls simplified") {}
828 /// @brief Make sure that the "strlen" function has the right prototype
829 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC)
831 if (f->getReturnType() == SLC.getTargetData()->getIntPtrType())
832 if (f->arg_size() == 1)
833 if (Function::const_arg_iterator AI = f->arg_begin())
834 if (AI->getType() == PointerType::get(Type::SByteTy))
839 /// @brief Perform the strlen optimization
840 virtual bool OptimizeCall(CallInst* ci, SimplifyLibCalls& SLC)
842 // Make sure we're dealing with an sbyte* here.
843 Value* str = ci->getOperand(1);
844 if (str->getType() != PointerType::get(Type::SByteTy))
847 // Does the call to strlen have exactly one use?
849 // Is that single use a binary operator?
850 if (BinaryOperator* bop = dyn_cast<BinaryOperator>(ci->use_back()))
851 // Is it compared against a constant integer?
852 if (ConstantInt* CI = dyn_cast<ConstantInt>(bop->getOperand(1)))
854 // Get the value the strlen result is compared to
855 uint64_t val = CI->getRawValue();
857 // If its compared against length 0 with == or !=
859 (bop->getOpcode() == Instruction::SetEQ ||
860 bop->getOpcode() == Instruction::SetNE))
862 // strlen(x) != 0 -> *x != 0
863 // strlen(x) == 0 -> *x == 0
864 LoadInst* load = new LoadInst(str,str->getName()+".first",ci);
865 BinaryOperator* rbop = BinaryOperator::create(bop->getOpcode(),
866 load, ConstantSInt::get(Type::SByteTy,0),
867 bop->getName()+".strlen", ci);
868 bop->replaceAllUsesWith(rbop);
869 bop->eraseFromParent();
870 ci->eraseFromParent();
875 // Get the length of the constant string operand
877 if (!getConstantStringLength(ci->getOperand(1),len))
880 // strlen("xyz") -> 3 (for example)
881 const Type *Ty = SLC.getTargetData()->getIntPtrType();
883 ci->replaceAllUsesWith(ConstantSInt::get(Ty, len));
885 ci->replaceAllUsesWith(ConstantUInt::get(Ty, len));
887 ci->eraseFromParent();
892 /// IsOnlyUsedInEqualsComparison - Return true if it only matters that the value
893 /// is equal or not-equal to zero.
894 static bool IsOnlyUsedInEqualsZeroComparison(Instruction *I) {
895 for (Value::use_iterator UI = I->use_begin(), E = I->use_end();
897 Instruction *User = cast<Instruction>(*UI);
898 if (User->getOpcode() == Instruction::SetNE ||
899 User->getOpcode() == Instruction::SetEQ) {
900 if (isa<Constant>(User->getOperand(1)) &&
901 cast<Constant>(User->getOperand(1))->isNullValue())
903 } else if (CastInst *CI = dyn_cast<CastInst>(User))
904 if (CI->getType() == Type::BoolTy)
906 // Unknown instruction.
912 /// This memcmpOptimization will simplify a call to the memcmp library
914 struct memcmpOptimization : public LibCallOptimization {
915 /// @brief Default Constructor
917 : LibCallOptimization("memcmp", "Number of 'memcmp' calls simplified") {}
919 /// @brief Make sure that the "memcmp" function has the right prototype
920 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &TD) {
921 Function::const_arg_iterator AI = F->arg_begin();
922 if (F->arg_size() != 3 || !isa<PointerType>(AI->getType())) return false;
923 if (!isa<PointerType>((++AI)->getType())) return false;
924 if (!(++AI)->getType()->isInteger()) return false;
925 if (!F->getReturnType()->isInteger()) return false;
929 /// Because of alignment and instruction information that we don't have, we
930 /// leave the bulk of this to the code generators.
932 /// Note that we could do much more if we could force alignment on otherwise
933 /// small aligned allocas, or if we could indicate that loads have a small
935 virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &TD) {
936 Value *LHS = CI->getOperand(1), *RHS = CI->getOperand(2);
938 // If the two operands are the same, return zero.
940 // memcmp(s,s,x) -> 0
941 CI->replaceAllUsesWith(Constant::getNullValue(CI->getType()));
942 CI->eraseFromParent();
946 // Make sure we have a constant length.
947 ConstantInt *LenC = dyn_cast<ConstantInt>(CI->getOperand(3));
948 if (!LenC) return false;
949 uint64_t Len = LenC->getRawValue();
951 // If the length is zero, this returns 0.
954 // memcmp(s1,s2,0) -> 0
955 CI->replaceAllUsesWith(Constant::getNullValue(CI->getType()));
956 CI->eraseFromParent();
959 // memcmp(S1,S2,1) -> *(ubyte*)S1 - *(ubyte*)S2
960 const Type *UCharPtr = PointerType::get(Type::UByteTy);
961 CastInst *Op1Cast = new CastInst(LHS, UCharPtr, LHS->getName(), CI);
962 CastInst *Op2Cast = new CastInst(RHS, UCharPtr, RHS->getName(), CI);
963 Value *S1V = new LoadInst(Op1Cast, LHS->getName()+".val", CI);
964 Value *S2V = new LoadInst(Op2Cast, RHS->getName()+".val", CI);
965 Value *RV = BinaryOperator::createSub(S1V, S2V, CI->getName()+".diff",CI);
966 if (RV->getType() != CI->getType())
967 RV = new CastInst(RV, CI->getType(), RV->getName(), CI);
968 CI->replaceAllUsesWith(RV);
969 CI->eraseFromParent();
973 if (IsOnlyUsedInEqualsZeroComparison(CI)) {
974 // TODO: IF both are aligned, use a short load/compare.
976 // memcmp(S1,S2,2) -> S1[0]-S2[0] | S1[1]-S2[1] iff only ==/!= 0 matters
977 const Type *UCharPtr = PointerType::get(Type::UByteTy);
978 CastInst *Op1Cast = new CastInst(LHS, UCharPtr, LHS->getName(), CI);
979 CastInst *Op2Cast = new CastInst(RHS, UCharPtr, RHS->getName(), CI);
980 Value *S1V1 = new LoadInst(Op1Cast, LHS->getName()+".val1", CI);
981 Value *S2V1 = new LoadInst(Op2Cast, RHS->getName()+".val1", CI);
982 Value *D1 = BinaryOperator::createSub(S1V1, S2V1,
983 CI->getName()+".d1", CI);
984 Constant *One = ConstantInt::get(Type::IntTy, 1);
985 Value *G1 = new GetElementPtrInst(Op1Cast, One, "next1v", CI);
986 Value *G2 = new GetElementPtrInst(Op2Cast, One, "next2v", CI);
987 Value *S1V2 = new LoadInst(G1, LHS->getName()+".val2", CI);
988 Value *S2V2 = new LoadInst(G1, RHS->getName()+".val2", CI);
989 Value *D2 = BinaryOperator::createSub(S1V2, S2V2,
990 CI->getName()+".d1", CI);
991 Value *Or = BinaryOperator::createOr(D1, D2, CI->getName()+".res", CI);
992 if (Or->getType() != CI->getType())
993 Or = new CastInst(Or, CI->getType(), Or->getName(), CI);
994 CI->replaceAllUsesWith(Or);
995 CI->eraseFromParent();
1008 /// This LibCallOptimization will simplify a call to the memcpy library
1009 /// function by expanding it out to a single store of size 0, 1, 2, 4, or 8
1010 /// bytes depending on the length of the string and the alignment. Additional
1011 /// optimizations are possible in code generation (sequence of immediate store)
1012 /// @brief Simplify the memcpy library function.
1013 struct LLVMMemCpyOptimization : public LibCallOptimization {
1014 /// @brief Default Constructor
1015 LLVMMemCpyOptimization() : LibCallOptimization("llvm.memcpy",
1016 "Number of 'llvm.memcpy' calls simplified") {}
1019 /// @brief Subclass Constructor
1020 LLVMMemCpyOptimization(const char* fname, const char* desc)
1021 : LibCallOptimization(fname, desc) {}
1024 /// @brief Make sure that the "memcpy" function has the right prototype
1025 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& TD) {
1026 // Just make sure this has 4 arguments per LLVM spec.
1027 return (f->arg_size() == 4);
1030 /// Because of alignment and instruction information that we don't have, we
1031 /// leave the bulk of this to the code generators. The optimization here just
1032 /// deals with a few degenerate cases where the length of the string and the
1033 /// alignment match the sizes of our intrinsic types so we can do a load and
1034 /// store instead of the memcpy call.
1035 /// @brief Perform the memcpy optimization.
1036 virtual bool OptimizeCall(CallInst* ci, SimplifyLibCalls& TD) {
1037 // Make sure we have constant int values to work with
1038 ConstantInt* LEN = dyn_cast<ConstantInt>(ci->getOperand(3));
1041 ConstantInt* ALIGN = dyn_cast<ConstantInt>(ci->getOperand(4));
1045 // If the length is larger than the alignment, we can't optimize
1046 uint64_t len = LEN->getRawValue();
1047 uint64_t alignment = ALIGN->getRawValue();
1049 alignment = 1; // Alignment 0 is identity for alignment 1
1050 if (len > alignment)
1053 // Get the type we will cast to, based on size of the string
1054 Value* dest = ci->getOperand(1);
1055 Value* src = ci->getOperand(2);
1060 // memcpy(d,s,0,a) -> noop
1061 ci->eraseFromParent();
1063 case 1: castType = Type::SByteTy; break;
1064 case 2: castType = Type::ShortTy; break;
1065 case 4: castType = Type::IntTy; break;
1066 case 8: castType = Type::LongTy; break;
1071 // Cast source and dest to the right sized primitive and then load/store
1073 new CastInst(src,PointerType::get(castType),src->getName()+".cast",ci);
1074 CastInst* DestCast =
1075 new CastInst(dest,PointerType::get(castType),dest->getName()+".cast",ci);
1076 LoadInst* LI = new LoadInst(SrcCast,SrcCast->getName()+".val",ci);
1077 StoreInst* SI = new StoreInst(LI, DestCast, ci);
1078 ci->eraseFromParent();
1081 } LLVMMemCpyOptimizer;
1083 /// This LibCallOptimization will simplify a call to the memmove library
1084 /// function. It is identical to MemCopyOptimization except for the name of
1086 /// @brief Simplify the memmove library function.
1087 struct LLVMMemMoveOptimization : public LLVMMemCpyOptimization {
1088 /// @brief Default Constructor
1089 LLVMMemMoveOptimization() : LLVMMemCpyOptimization("llvm.memmove",
1090 "Number of 'llvm.memmove' calls simplified") {}
1092 } LLVMMemMoveOptimizer;
1094 /// This LibCallOptimization will simplify a call to the memset library
1095 /// function by expanding it out to a single store of size 0, 1, 2, 4, or 8
1096 /// bytes depending on the length argument.
1097 struct LLVMMemSetOptimization : public LibCallOptimization {
1098 /// @brief Default Constructor
1099 LLVMMemSetOptimization() : LibCallOptimization("llvm.memset",
1100 "Number of 'llvm.memset' calls simplified") {}
1103 /// @brief Make sure that the "memset" function has the right prototype
1104 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &TD) {
1105 // Just make sure this has 3 arguments per LLVM spec.
1106 return F->arg_size() == 4;
1109 /// Because of alignment and instruction information that we don't have, we
1110 /// leave the bulk of this to the code generators. The optimization here just
1111 /// deals with a few degenerate cases where the length parameter is constant
1112 /// and the alignment matches the sizes of our intrinsic types so we can do
1113 /// store instead of the memcpy call. Other calls are transformed into the
1114 /// llvm.memset intrinsic.
1115 /// @brief Perform the memset optimization.
1116 virtual bool OptimizeCall(CallInst *ci, SimplifyLibCalls &TD) {
1117 // Make sure we have constant int values to work with
1118 ConstantInt* LEN = dyn_cast<ConstantInt>(ci->getOperand(3));
1121 ConstantInt* ALIGN = dyn_cast<ConstantInt>(ci->getOperand(4));
1125 // Extract the length and alignment
1126 uint64_t len = LEN->getRawValue();
1127 uint64_t alignment = ALIGN->getRawValue();
1129 // Alignment 0 is identity for alignment 1
1133 // If the length is zero, this is a no-op
1135 // memset(d,c,0,a) -> noop
1136 ci->eraseFromParent();
1140 // If the length is larger than the alignment, we can't optimize
1141 if (len > alignment)
1144 // Make sure we have a constant ubyte to work with so we can extract
1145 // the value to be filled.
1146 ConstantUInt* FILL = dyn_cast<ConstantUInt>(ci->getOperand(2));
1149 if (FILL->getType() != Type::UByteTy)
1152 // memset(s,c,n) -> store s, c (for n=1,2,4,8)
1154 // Extract the fill character
1155 uint64_t fill_char = FILL->getValue();
1156 uint64_t fill_value = fill_char;
1158 // Get the type we will cast to, based on size of memory area to fill, and
1159 // and the value we will store there.
1160 Value* dest = ci->getOperand(1);
1164 castType = Type::UByteTy;
1167 castType = Type::UShortTy;
1168 fill_value |= fill_char << 8;
1171 castType = Type::UIntTy;
1172 fill_value |= fill_char << 8 | fill_char << 16 | fill_char << 24;
1175 castType = Type::ULongTy;
1176 fill_value |= fill_char << 8 | fill_char << 16 | fill_char << 24;
1177 fill_value |= fill_char << 32 | fill_char << 40 | fill_char << 48;
1178 fill_value |= fill_char << 56;
1184 // Cast dest to the right sized primitive and then load/store
1185 CastInst* DestCast =
1186 new CastInst(dest,PointerType::get(castType),dest->getName()+".cast",ci);
1187 new StoreInst(ConstantUInt::get(castType,fill_value),DestCast, ci);
1188 ci->eraseFromParent();
1191 } LLVMMemSetOptimizer;
1193 /// This LibCallOptimization will simplify calls to the "pow" library
1194 /// function. It looks for cases where the result of pow is well known and
1195 /// substitutes the appropriate value.
1196 /// @brief Simplify the pow library function.
1197 struct PowOptimization : public LibCallOptimization {
1199 /// @brief Default Constructor
1200 PowOptimization() : LibCallOptimization("pow",
1201 "Number of 'pow' calls simplified") {}
1203 /// @brief Make sure that the "pow" function has the right prototype
1204 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC){
1205 // Just make sure this has 2 arguments
1206 return (f->arg_size() == 2);
1209 /// @brief Perform the pow optimization.
1210 virtual bool OptimizeCall(CallInst *ci, SimplifyLibCalls &SLC) {
1211 const Type *Ty = cast<Function>(ci->getOperand(0))->getReturnType();
1212 Value* base = ci->getOperand(1);
1213 Value* expn = ci->getOperand(2);
1214 if (ConstantFP *Op1 = dyn_cast<ConstantFP>(base)) {
1215 double Op1V = Op1->getValue();
1217 // pow(1.0,x) -> 1.0
1218 ci->replaceAllUsesWith(ConstantFP::get(Ty,1.0));
1219 ci->eraseFromParent();
1222 } else if (ConstantFP* Op2 = dyn_cast<ConstantFP>(expn)) {
1223 double Op2V = Op2->getValue();
1225 // pow(x,0.0) -> 1.0
1226 ci->replaceAllUsesWith(ConstantFP::get(Ty,1.0));
1227 ci->eraseFromParent();
1229 } else if (Op2V == 0.5) {
1230 // pow(x,0.5) -> sqrt(x)
1231 CallInst* sqrt_inst = new CallInst(SLC.get_sqrt(), base,
1232 ci->getName()+".pow",ci);
1233 ci->replaceAllUsesWith(sqrt_inst);
1234 ci->eraseFromParent();
1236 } else if (Op2V == 1.0) {
1238 ci->replaceAllUsesWith(base);
1239 ci->eraseFromParent();
1241 } else if (Op2V == -1.0) {
1242 // pow(x,-1.0) -> 1.0/x
1243 BinaryOperator* div_inst= BinaryOperator::createDiv(
1244 ConstantFP::get(Ty,1.0), base, ci->getName()+".pow", ci);
1245 ci->replaceAllUsesWith(div_inst);
1246 ci->eraseFromParent();
1250 return false; // opt failed
1254 /// This LibCallOptimization will simplify calls to the "fprintf" library
1255 /// function. It looks for cases where the result of fprintf is not used and the
1256 /// operation can be reduced to something simpler.
1257 /// @brief Simplify the pow library function.
1258 struct FPrintFOptimization : public LibCallOptimization {
1260 /// @brief Default Constructor
1261 FPrintFOptimization() : LibCallOptimization("fprintf",
1262 "Number of 'fprintf' calls simplified") {}
1264 /// @brief Make sure that the "fprintf" function has the right prototype
1265 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC){
1266 // Just make sure this has at least 2 arguments
1267 return (f->arg_size() >= 2);
1270 /// @brief Perform the fprintf optimization.
1271 virtual bool OptimizeCall(CallInst* ci, SimplifyLibCalls& SLC) {
1272 // If the call has more than 3 operands, we can't optimize it
1273 if (ci->getNumOperands() > 4 || ci->getNumOperands() <= 2)
1276 // If the result of the fprintf call is used, none of these optimizations
1278 if (!ci->use_empty())
1281 // All the optimizations depend on the length of the second argument and the
1282 // fact that it is a constant string array. Check that now
1284 ConstantArray* CA = 0;
1285 if (!getConstantStringLength(ci->getOperand(2), len, &CA))
1288 if (ci->getNumOperands() == 3) {
1289 // Make sure there's no % in the constant array
1290 for (unsigned i = 0; i < len; ++i) {
1291 if (ConstantInt* CI = dyn_cast<ConstantInt>(CA->getOperand(i))) {
1292 // Check for the null terminator
1293 if (CI->getRawValue() == '%')
1294 return false; // we found end of string
1300 // fprintf(file,fmt) -> fwrite(fmt,strlen(fmt),file)
1301 const Type* FILEptr_type = ci->getOperand(1)->getType();
1302 Function* fwrite_func = SLC.get_fwrite(FILEptr_type);
1306 // Make sure that the fprintf() and fwrite() functions both take the
1307 // same type of char pointer.
1308 if (ci->getOperand(2)->getType() !=
1309 fwrite_func->getFunctionType()->getParamType(0))
1312 std::vector<Value*> args;
1313 args.push_back(ci->getOperand(2));
1314 args.push_back(ConstantUInt::get(SLC.getIntPtrType(),len));
1315 args.push_back(ConstantUInt::get(SLC.getIntPtrType(),1));
1316 args.push_back(ci->getOperand(1));
1317 new CallInst(fwrite_func,args,ci->getName(),ci);
1318 ci->replaceAllUsesWith(ConstantSInt::get(Type::IntTy,len));
1319 ci->eraseFromParent();
1323 // The remaining optimizations require the format string to be length 2
1328 // The first character has to be a %
1329 if (ConstantInt* CI = dyn_cast<ConstantInt>(CA->getOperand(0)))
1330 if (CI->getRawValue() != '%')
1333 // Get the second character and switch on its value
1334 ConstantInt* CI = dyn_cast<ConstantInt>(CA->getOperand(1));
1335 switch (CI->getRawValue()) {
1339 ConstantArray* CA = 0;
1340 if (!getConstantStringLength(ci->getOperand(3), len, &CA))
1343 // fprintf(file,"%s",str) -> fwrite(fmt,strlen(fmt),1,file)
1344 const Type* FILEptr_type = ci->getOperand(1)->getType();
1345 Function* fwrite_func = SLC.get_fwrite(FILEptr_type);
1348 std::vector<Value*> args;
1349 args.push_back(CastToCStr(ci->getOperand(3), *ci));
1350 args.push_back(ConstantUInt::get(SLC.getIntPtrType(),len));
1351 args.push_back(ConstantUInt::get(SLC.getIntPtrType(),1));
1352 args.push_back(ci->getOperand(1));
1353 new CallInst(fwrite_func,args,ci->getName(),ci);
1354 ci->replaceAllUsesWith(ConstantSInt::get(Type::IntTy,len));
1359 ConstantInt* CI = dyn_cast<ConstantInt>(ci->getOperand(3));
1363 const Type* FILEptr_type = ci->getOperand(1)->getType();
1364 Function* fputc_func = SLC.get_fputc(FILEptr_type);
1367 CastInst* cast = new CastInst(CI,Type::IntTy,CI->getName()+".int",ci);
1368 new CallInst(fputc_func,cast,ci->getOperand(1),"",ci);
1369 ci->replaceAllUsesWith(ConstantSInt::get(Type::IntTy,1));
1375 ci->eraseFromParent();
1380 /// This LibCallOptimization will simplify calls to the "sprintf" library
1381 /// function. It looks for cases where the result of sprintf is not used and the
1382 /// operation can be reduced to something simpler.
1383 /// @brief Simplify the pow library function.
1384 struct SPrintFOptimization : public LibCallOptimization {
1386 /// @brief Default Constructor
1387 SPrintFOptimization() : LibCallOptimization("sprintf",
1388 "Number of 'sprintf' calls simplified") {}
1390 /// @brief Make sure that the "fprintf" function has the right prototype
1391 virtual bool ValidateCalledFunction(const Function *f, SimplifyLibCalls &SLC){
1392 // Just make sure this has at least 2 arguments
1393 return (f->getReturnType() == Type::IntTy && f->arg_size() >= 2);
1396 /// @brief Perform the sprintf optimization.
1397 virtual bool OptimizeCall(CallInst *ci, SimplifyLibCalls &SLC) {
1398 // If the call has more than 3 operands, we can't optimize it
1399 if (ci->getNumOperands() > 4 || ci->getNumOperands() < 3)
1402 // All the optimizations depend on the length of the second argument and the
1403 // fact that it is a constant string array. Check that now
1405 ConstantArray* CA = 0;
1406 if (!getConstantStringLength(ci->getOperand(2), len, &CA))
1409 if (ci->getNumOperands() == 3) {
1411 // If the length is 0, we just need to store a null byte
1412 new StoreInst(ConstantInt::get(Type::SByteTy,0),ci->getOperand(1),ci);
1413 ci->replaceAllUsesWith(ConstantSInt::get(Type::IntTy,0));
1414 ci->eraseFromParent();
1418 // Make sure there's no % in the constant array
1419 for (unsigned i = 0; i < len; ++i) {
1420 if (ConstantInt* CI = dyn_cast<ConstantInt>(CA->getOperand(i))) {
1421 // Check for the null terminator
1422 if (CI->getRawValue() == '%')
1423 return false; // we found a %, can't optimize
1425 return false; // initializer is not constant int, can't optimize
1429 // Increment length because we want to copy the null byte too
1432 // sprintf(str,fmt) -> llvm.memcpy(str,fmt,strlen(fmt),1)
1433 Function* memcpy_func = SLC.get_memcpy();
1436 std::vector<Value*> args;
1437 args.push_back(ci->getOperand(1));
1438 args.push_back(ci->getOperand(2));
1439 args.push_back(ConstantUInt::get(Type::UIntTy,len));
1440 args.push_back(ConstantUInt::get(Type::UIntTy,1));
1441 new CallInst(memcpy_func,args,"",ci);
1442 ci->replaceAllUsesWith(ConstantSInt::get(Type::IntTy,len));
1443 ci->eraseFromParent();
1447 // The remaining optimizations require the format string to be length 2
1452 // The first character has to be a %
1453 if (ConstantInt* CI = dyn_cast<ConstantInt>(CA->getOperand(0)))
1454 if (CI->getRawValue() != '%')
1457 // Get the second character and switch on its value
1458 ConstantInt* CI = dyn_cast<ConstantInt>(CA->getOperand(1));
1459 switch (CI->getRawValue()) {
1461 // sprintf(dest,"%s",str) -> llvm.memcpy(dest, str, strlen(str)+1, 1)
1462 Function* strlen_func = SLC.get_strlen();
1463 Function* memcpy_func = SLC.get_memcpy();
1464 if (!strlen_func || !memcpy_func)
1467 Value *Len = new CallInst(strlen_func, CastToCStr(ci->getOperand(3), *ci),
1468 ci->getOperand(3)->getName()+".len", ci);
1469 Value *Len1 = BinaryOperator::createAdd(Len,
1470 ConstantInt::get(Len->getType(), 1),
1471 Len->getName()+"1", ci);
1472 if (Len1->getType() != Type::UIntTy)
1473 Len1 = new CastInst(Len1, Type::UIntTy, Len1->getName(), ci);
1474 std::vector<Value*> args;
1475 args.push_back(CastToCStr(ci->getOperand(1), *ci));
1476 args.push_back(CastToCStr(ci->getOperand(3), *ci));
1477 args.push_back(Len1);
1478 args.push_back(ConstantUInt::get(Type::UIntTy,1));
1479 new CallInst(memcpy_func, args, "", ci);
1481 // The strlen result is the unincremented number of bytes in the string.
1482 if (!ci->use_empty()) {
1483 if (Len->getType() != ci->getType())
1484 Len = new CastInst(Len, ci->getType(), Len->getName(), ci);
1485 ci->replaceAllUsesWith(Len);
1487 ci->eraseFromParent();
1491 // sprintf(dest,"%c",chr) -> store chr, dest
1492 CastInst* cast = new CastInst(ci->getOperand(3),Type::SByteTy,"char",ci);
1493 new StoreInst(cast, ci->getOperand(1), ci);
1494 GetElementPtrInst* gep = new GetElementPtrInst(ci->getOperand(1),
1495 ConstantUInt::get(Type::UIntTy,1),ci->getOperand(1)->getName()+".end",
1497 new StoreInst(ConstantInt::get(Type::SByteTy,0),gep,ci);
1498 ci->replaceAllUsesWith(ConstantSInt::get(Type::IntTy,1));
1499 ci->eraseFromParent();
1507 /// This LibCallOptimization will simplify calls to the "fputs" library
1508 /// function. It looks for cases where the result of fputs is not used and the
1509 /// operation can be reduced to something simpler.
1510 /// @brief Simplify the pow library function.
1511 struct PutsOptimization : public LibCallOptimization {
1513 /// @brief Default Constructor
1514 PutsOptimization() : LibCallOptimization("fputs",
1515 "Number of 'fputs' calls simplified") {}
1517 /// @brief Make sure that the "fputs" function has the right prototype
1518 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
1519 // Just make sure this has 2 arguments
1520 return F->arg_size() == 2;
1523 /// @brief Perform the fputs optimization.
1524 virtual bool OptimizeCall(CallInst* ci, SimplifyLibCalls& SLC) {
1525 // If the result is used, none of these optimizations work
1526 if (!ci->use_empty())
1529 // All the optimizations depend on the length of the first argument and the
1530 // fact that it is a constant string array. Check that now
1532 if (!getConstantStringLength(ci->getOperand(1), len))
1537 // fputs("",F) -> noop
1541 // fputs(s,F) -> fputc(s[0],F) (if s is constant and strlen(s) == 1)
1542 const Type* FILEptr_type = ci->getOperand(2)->getType();
1543 Function* fputc_func = SLC.get_fputc(FILEptr_type);
1546 LoadInst* loadi = new LoadInst(ci->getOperand(1),
1547 ci->getOperand(1)->getName()+".byte",ci);
1548 CastInst* casti = new CastInst(loadi,Type::IntTy,
1549 loadi->getName()+".int",ci);
1550 new CallInst(fputc_func,casti,ci->getOperand(2),"",ci);
1555 // fputs(s,F) -> fwrite(s,1,len,F) (if s is constant and strlen(s) > 1)
1556 const Type* FILEptr_type = ci->getOperand(2)->getType();
1557 Function* fwrite_func = SLC.get_fwrite(FILEptr_type);
1560 std::vector<Value*> parms;
1561 parms.push_back(ci->getOperand(1));
1562 parms.push_back(ConstantUInt::get(SLC.getIntPtrType(),len));
1563 parms.push_back(ConstantUInt::get(SLC.getIntPtrType(),1));
1564 parms.push_back(ci->getOperand(2));
1565 new CallInst(fwrite_func,parms,"",ci);
1569 ci->eraseFromParent();
1570 return true; // success
1574 /// This LibCallOptimization will simplify calls to the "isdigit" library
1575 /// function. It simply does range checks the parameter explicitly.
1576 /// @brief Simplify the isdigit library function.
1577 struct isdigitOptimization : public LibCallOptimization {
1579 isdigitOptimization() : LibCallOptimization("isdigit",
1580 "Number of 'isdigit' calls simplified") {}
1582 /// @brief Make sure that the "isdigit" function has the right prototype
1583 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC){
1584 // Just make sure this has 1 argument
1585 return (f->arg_size() == 1);
1588 /// @brief Perform the toascii optimization.
1589 virtual bool OptimizeCall(CallInst *ci, SimplifyLibCalls &SLC) {
1590 if (ConstantInt* CI = dyn_cast<ConstantInt>(ci->getOperand(1))) {
1591 // isdigit(c) -> 0 or 1, if 'c' is constant
1592 uint64_t val = CI->getRawValue();
1593 if (val >= '0' && val <='9')
1594 ci->replaceAllUsesWith(ConstantSInt::get(Type::IntTy,1));
1596 ci->replaceAllUsesWith(ConstantSInt::get(Type::IntTy,0));
1597 ci->eraseFromParent();
1601 // isdigit(c) -> (unsigned)c - '0' <= 9
1603 new CastInst(ci->getOperand(1),Type::UIntTy,
1604 ci->getOperand(1)->getName()+".uint",ci);
1605 BinaryOperator* sub_inst = BinaryOperator::createSub(cast,
1606 ConstantUInt::get(Type::UIntTy,0x30),
1607 ci->getOperand(1)->getName()+".sub",ci);
1608 SetCondInst* setcond_inst = new SetCondInst(Instruction::SetLE,sub_inst,
1609 ConstantUInt::get(Type::UIntTy,9),
1610 ci->getOperand(1)->getName()+".cmp",ci);
1612 new CastInst(setcond_inst,Type::IntTy,
1613 ci->getOperand(1)->getName()+".isdigit",ci);
1614 ci->replaceAllUsesWith(c2);
1615 ci->eraseFromParent();
1620 struct isasciiOptimization : public LibCallOptimization {
1622 isasciiOptimization()
1623 : LibCallOptimization("isascii", "Number of 'isascii' calls simplified") {}
1625 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
1626 return F->arg_size() == 1 && F->arg_begin()->getType()->isInteger() &&
1627 F->getReturnType()->isInteger();
1630 /// @brief Perform the isascii optimization.
1631 virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
1632 // isascii(c) -> (unsigned)c < 128
1633 Value *V = CI->getOperand(1);
1634 if (V->getType()->isSigned())
1635 V = new CastInst(V, V->getType()->getUnsignedVersion(), V->getName(), CI);
1636 Value *Cmp = BinaryOperator::createSetLT(V, ConstantUInt::get(V->getType(),
1638 V->getName()+".isascii", CI);
1639 if (Cmp->getType() != CI->getType())
1640 Cmp = new CastInst(Cmp, CI->getType(), Cmp->getName(), CI);
1641 CI->replaceAllUsesWith(Cmp);
1642 CI->eraseFromParent();
1648 /// This LibCallOptimization will simplify calls to the "toascii" library
1649 /// function. It simply does the corresponding and operation to restrict the
1650 /// range of values to the ASCII character set (0-127).
1651 /// @brief Simplify the toascii library function.
1652 struct ToAsciiOptimization : public LibCallOptimization {
1654 /// @brief Default Constructor
1655 ToAsciiOptimization() : LibCallOptimization("toascii",
1656 "Number of 'toascii' calls simplified") {}
1658 /// @brief Make sure that the "fputs" function has the right prototype
1659 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC){
1660 // Just make sure this has 2 arguments
1661 return (f->arg_size() == 1);
1664 /// @brief Perform the toascii optimization.
1665 virtual bool OptimizeCall(CallInst *ci, SimplifyLibCalls &SLC) {
1666 // toascii(c) -> (c & 0x7f)
1667 Value* chr = ci->getOperand(1);
1668 BinaryOperator* and_inst = BinaryOperator::createAnd(chr,
1669 ConstantInt::get(chr->getType(),0x7F),ci->getName()+".toascii",ci);
1670 ci->replaceAllUsesWith(and_inst);
1671 ci->eraseFromParent();
1676 /// This LibCallOptimization will simplify calls to the "ffs" library
1677 /// calls which find the first set bit in an int, long, or long long. The
1678 /// optimization is to compute the result at compile time if the argument is
1680 /// @brief Simplify the ffs library function.
1681 struct FFSOptimization : public LibCallOptimization {
1683 /// @brief Subclass Constructor
1684 FFSOptimization(const char* funcName, const char* description)
1685 : LibCallOptimization(funcName, description) {}
1688 /// @brief Default Constructor
1689 FFSOptimization() : LibCallOptimization("ffs",
1690 "Number of 'ffs' calls simplified") {}
1692 /// @brief Make sure that the "ffs" function has the right prototype
1693 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
1694 // Just make sure this has 2 arguments
1695 return F->arg_size() == 1 && F->getReturnType() == Type::IntTy;
1698 /// @brief Perform the ffs optimization.
1699 virtual bool OptimizeCall(CallInst *TheCall, SimplifyLibCalls &SLC) {
1700 if (ConstantInt *CI = dyn_cast<ConstantInt>(TheCall->getOperand(1))) {
1701 // ffs(cnst) -> bit#
1702 // ffsl(cnst) -> bit#
1703 // ffsll(cnst) -> bit#
1704 uint64_t val = CI->getRawValue();
1708 while ((val & 1) == 0) {
1713 TheCall->replaceAllUsesWith(ConstantSInt::get(Type::IntTy, result));
1714 TheCall->eraseFromParent();
1718 // ffs(x) -> x == 0 ? 0 : llvm.cttz(x)+1
1719 // ffsl(x) -> x == 0 ? 0 : llvm.cttz(x)+1
1720 // ffsll(x) -> x == 0 ? 0 : llvm.cttz(x)+1
1721 const Type *ArgType = TheCall->getOperand(1)->getType();
1722 ArgType = ArgType->getUnsignedVersion();
1723 const char *CTTZName;
1724 switch (ArgType->getTypeID()) {
1725 default: assert(0 && "Unknown unsigned type!");
1726 case Type::UByteTyID : CTTZName = "llvm.cttz.i8" ; break;
1727 case Type::UShortTyID: CTTZName = "llvm.cttz.i16"; break;
1728 case Type::UIntTyID : CTTZName = "llvm.cttz.i32"; break;
1729 case Type::ULongTyID : CTTZName = "llvm.cttz.i64"; break;
1732 Function *F = SLC.getModule()->getOrInsertFunction(CTTZName, ArgType,
1734 Value *V = new CastInst(TheCall->getOperand(1), ArgType, "tmp", TheCall);
1735 Value *V2 = new CallInst(F, V, "tmp", TheCall);
1736 V2 = new CastInst(V2, Type::IntTy, "tmp", TheCall);
1737 V2 = BinaryOperator::createAdd(V2, ConstantSInt::get(Type::IntTy, 1),
1740 BinaryOperator::createSetEQ(V, Constant::getNullValue(V->getType()),
1742 V2 = new SelectInst(Cond, ConstantInt::get(Type::IntTy, 0), V2,
1743 TheCall->getName(), TheCall);
1744 TheCall->replaceAllUsesWith(V2);
1745 TheCall->eraseFromParent();
1750 /// This LibCallOptimization will simplify calls to the "ffsl" library
1751 /// calls. It simply uses FFSOptimization for which the transformation is
1753 /// @brief Simplify the ffsl library function.
1754 struct FFSLOptimization : public FFSOptimization {
1756 /// @brief Default Constructor
1757 FFSLOptimization() : FFSOptimization("ffsl",
1758 "Number of 'ffsl' calls simplified") {}
1762 /// This LibCallOptimization will simplify calls to the "ffsll" library
1763 /// calls. It simply uses FFSOptimization for which the transformation is
1765 /// @brief Simplify the ffsl library function.
1766 struct FFSLLOptimization : public FFSOptimization {
1768 /// @brief Default Constructor
1769 FFSLLOptimization() : FFSOptimization("ffsll",
1770 "Number of 'ffsll' calls simplified") {}
1775 /// This LibCallOptimization will simplify calls to the "floor" library
1777 /// @brief Simplify the floor library function.
1778 struct FloorOptimization : public LibCallOptimization {
1780 : LibCallOptimization("floor", "Number of 'floor' calls simplified") {}
1782 /// @brief Make sure that the "floor" function has the right prototype
1783 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
1784 return F->arg_size() == 1 && F->arg_begin()->getType() == Type::DoubleTy &&
1785 F->getReturnType() == Type::DoubleTy;
1788 virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
1789 // If this is a float argument passed in, convert to floorf.
1790 // e.g. floor((double)FLT) -> (double)floorf(FLT). There can be no loss of
1791 // precision due to this.
1792 if (CastInst *Cast = dyn_cast<CastInst>(CI->getOperand(1)))
1793 if (Cast->getOperand(0)->getType() == Type::FloatTy) {
1794 Value *New = new CallInst(SLC.get_floorf(), Cast->getOperand(0),
1796 New = new CastInst(New, Type::DoubleTy, CI->getName(), CI);
1797 CI->replaceAllUsesWith(New);
1798 CI->eraseFromParent();
1799 if (Cast->use_empty())
1800 Cast->eraseFromParent();
1803 return false; // opt failed
1808 FloorOptimization FloorOptimizer;
1813 /// A function to compute the length of a null-terminated constant array of
1814 /// integers. This function can't rely on the size of the constant array
1815 /// because there could be a null terminator in the middle of the array.
1816 /// We also have to bail out if we find a non-integer constant initializer
1817 /// of one of the elements or if there is no null-terminator. The logic
1818 /// below checks each of these conditions and will return true only if all
1819 /// conditions are met. In that case, the \p len parameter is set to the length
1820 /// of the null-terminated string. If false is returned, the conditions were
1821 /// not met and len is set to 0.
1822 /// @brief Get the length of a constant string (null-terminated array).
1823 bool getConstantStringLength(Value *V, uint64_t &len, ConstantArray **CA) {
1824 assert(V != 0 && "Invalid args to getConstantStringLength");
1825 len = 0; // make sure we initialize this
1827 // If the value is not a GEP instruction nor a constant expression with a
1828 // GEP instruction, then return false because ConstantArray can't occur
1830 if (GetElementPtrInst* GEPI = dyn_cast<GetElementPtrInst>(V))
1832 else if (ConstantExpr* CE = dyn_cast<ConstantExpr>(V))
1833 if (CE->getOpcode() == Instruction::GetElementPtr)
1840 // Make sure the GEP has exactly three arguments.
1841 if (GEP->getNumOperands() != 3)
1844 // Check to make sure that the first operand of the GEP is an integer and
1845 // has value 0 so that we are sure we're indexing into the initializer.
1846 if (ConstantInt* op1 = dyn_cast<ConstantInt>(GEP->getOperand(1))) {
1847 if (!op1->isNullValue())
1852 // Ensure that the second operand is a ConstantInt. If it isn't then this
1853 // GEP is wonky and we're not really sure what were referencing into and
1854 // better of not optimizing it. While we're at it, get the second index
1855 // value. We'll need this later for indexing the ConstantArray.
1856 uint64_t start_idx = 0;
1857 if (ConstantInt* CI = dyn_cast<ConstantInt>(GEP->getOperand(2)))
1858 start_idx = CI->getRawValue();
1862 // The GEP instruction, constant or instruction, must reference a global
1863 // variable that is a constant and is initialized. The referenced constant
1864 // initializer is the array that we'll use for optimization.
1865 GlobalVariable* GV = dyn_cast<GlobalVariable>(GEP->getOperand(0));
1866 if (!GV || !GV->isConstant() || !GV->hasInitializer())
1869 // Get the initializer.
1870 Constant* INTLZR = GV->getInitializer();
1872 // Handle the ConstantAggregateZero case
1873 if (ConstantAggregateZero *CAZ = dyn_cast<ConstantAggregateZero>(INTLZR)) {
1874 // This is a degenerate case. The initializer is constant zero so the
1875 // length of the string must be zero.
1880 // Must be a Constant Array
1881 ConstantArray* A = dyn_cast<ConstantArray>(INTLZR);
1885 // Get the number of elements in the array
1886 uint64_t max_elems = A->getType()->getNumElements();
1888 // Traverse the constant array from start_idx (derived above) which is
1889 // the place the GEP refers to in the array.
1890 for (len = start_idx; len < max_elems; len++) {
1891 if (ConstantInt *CI = dyn_cast<ConstantInt>(A->getOperand(len))) {
1892 // Check for the null terminator
1893 if (CI->isNullValue())
1894 break; // we found end of string
1896 return false; // This array isn't suitable, non-int initializer
1899 if (len >= max_elems)
1900 return false; // This array isn't null terminated
1902 // Subtract out the initial value from the length
1906 return true; // success!
1909 /// CastToCStr - Return V if it is an sbyte*, otherwise cast it to sbyte*,
1910 /// inserting the cast before IP, and return the cast.
1911 /// @brief Cast a value to a "C" string.
1912 Value *CastToCStr(Value *V, Instruction &IP) {
1913 const Type *SBPTy = PointerType::get(Type::SByteTy);
1914 if (V->getType() != SBPTy)
1915 return new CastInst(V, SBPTy, V->getName(), &IP);
1920 // Additional cases that we need to add to this file:
1923 // * cbrt(expN(X)) -> expN(x/3)
1924 // * cbrt(sqrt(x)) -> pow(x,1/6)
1925 // * cbrt(sqrt(x)) -> pow(x,1/9)
1928 // * cos(-x) -> cos(x)
1931 // * exp(log(x)) -> x
1934 // * log(exp(x)) -> x
1935 // * log(x**y) -> y*log(x)
1936 // * log(exp(y)) -> y*log(e)
1937 // * log(exp2(y)) -> y*log(2)
1938 // * log(exp10(y)) -> y*log(10)
1939 // * log(sqrt(x)) -> 0.5*log(x)
1940 // * log(pow(x,y)) -> y*log(x)
1942 // lround, lroundf, lroundl:
1943 // * lround(cnst) -> cnst'
1946 // * memcmp(x,y,l) -> cnst
1947 // (if all arguments are constant and strlen(x) <= l and strlen(y) <= l)
1950 // * memmove(d,s,l,a) -> memcpy(d,s,l,a)
1951 // (if s is a global constant array)
1954 // * pow(exp(x),y) -> exp(x*y)
1955 // * pow(sqrt(x),y) -> pow(x,y*0.5)
1956 // * pow(pow(x,y),z)-> pow(x,y*z)
1959 // * puts("") -> fputc("\n",stdout) (how do we get "stdout"?)
1961 // round, roundf, roundl:
1962 // * round(cnst) -> cnst'
1965 // * signbit(cnst) -> cnst'
1966 // * signbit(nncst) -> 0 (if pstv is a non-negative constant)
1968 // sqrt, sqrtf, sqrtl:
1969 // * sqrt(expN(x)) -> expN(x*0.5)
1970 // * sqrt(Nroot(x)) -> pow(x,1/(2*N))
1971 // * sqrt(pow(x,y)) -> pow(|x|,y*0.5)
1974 // * stpcpy(str, "literal") ->
1975 // llvm.memcpy(str,"literal",strlen("literal")+1,1)
1977 // * strrchr(s,c) -> reverse_offset_of_in(c,s)
1978 // (if c is a constant integer and s is a constant string)
1979 // * strrchr(s1,0) -> strchr(s1,0)
1982 // * strncat(x,y,0) -> x
1983 // * strncat(x,y,0) -> x (if strlen(y) = 0)
1984 // * strncat(x,y,l) -> strcat(x,y) (if y and l are constants an l > strlen(y))
1987 // * strncpy(d,s,0) -> d
1988 // * strncpy(d,s,l) -> memcpy(d,s,l,1)
1989 // (if s and l are constants)
1992 // * strpbrk(s,a) -> offset_in_for(s,a)
1993 // (if s and a are both constant strings)
1994 // * strpbrk(s,"") -> 0
1995 // * strpbrk(s,a) -> strchr(s,a[0]) (if a is constant string of length 1)
1998 // * strspn(s,a) -> const_int (if both args are constant)
1999 // * strspn("",a) -> 0
2000 // * strspn(s,"") -> 0
2001 // * strcspn(s,a) -> const_int (if both args are constant)
2002 // * strcspn("",a) -> 0
2003 // * strcspn(s,"") -> strlen(a)
2006 // * strstr(x,x) -> x
2007 // * strstr(s1,s2) -> offset_of_s2_in(s1)
2008 // (if s1 and s2 are constant strings)
2011 // * tan(atan(x)) -> x
2013 // trunc, truncf, truncl:
2014 // * trunc(cnst) -> cnst'