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/Support/Debug.h"
29 #include "llvm/Target/TargetData.h"
30 #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 "Total number of library calls simplified");
41 // Forward declarations
42 class LibCallOptimization;
43 class SimplifyLibCalls;
45 /// This hash map 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 hash_map<std::string,LibCallOptimization*> optlist;
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
70 /// The \p fname argument must be the name of the library function being
71 /// optimized by the subclass.
72 /// @brief Constructor that registers the optimization.
73 LibCallOptimization(const char* fname, const char* description )
76 , occurrences("simplify-libcalls",description)
79 // Register this call optimizer in the optlist (a hash_map)
80 optlist[fname] = this;
83 /// @brief Deregister from the optlist
84 virtual ~LibCallOptimization() { optlist.erase(func_name); }
86 /// The implementation of this function in subclasses should determine if
87 /// \p F is suitable for the optimization. This method is called by
88 /// SimplifyLibCalls::runOnModule to short circuit visiting all the call
89 /// sites of such a function if that function is not suitable in the first
90 /// place. If the called function is suitabe, this method should return true;
91 /// false, otherwise. This function should also perform any lazy
92 /// initialization that the LibCallOptimization needs to do, if its to return
93 /// true. This avoids doing initialization until the optimizer is actually
94 /// going to be called upon to do some optimization.
95 /// @brief Determine if the function is suitable for optimization
96 virtual bool ValidateCalledFunction(
97 const Function* F, ///< The function that is the target of call sites
98 SimplifyLibCalls& SLC ///< The pass object invoking us
101 /// The implementations of this function in subclasses is the heart of the
102 /// SimplifyLibCalls algorithm. Sublcasses of this class implement
103 /// OptimizeCall to determine if (a) the conditions are right for optimizing
104 /// the call and (b) to perform the optimization. If an action is taken
105 /// against ci, the subclass is responsible for returning true and ensuring
106 /// that ci is erased from its parent.
107 /// @brief Optimize a call, if possible.
108 virtual bool OptimizeCall(
109 CallInst* ci, ///< The call instruction that should be optimized.
110 SimplifyLibCalls& SLC ///< The pass object invoking us
113 /// @brief Get the name of the library call being optimized
114 const char * getFunctionName() const { return func_name; }
117 /// @brief Called by SimplifyLibCalls to update the occurrences statistic.
118 void succeeded() { DEBUG(++occurrences); }
122 const char* func_name; ///< Name of the library call we optimize
124 Statistic<> occurrences; ///< debug statistic (-debug-only=simplify-libcalls)
128 /// This class is an LLVM Pass that applies each of the LibCallOptimization
129 /// instances to all the call sites in a module, relatively efficiently. The
130 /// purpose of this pass is to provide optimizations for calls to well-known
131 /// functions with well-known semantics, such as those in the c library. The
132 /// class provides the basic infrastructure for handling runOnModule. Whenever /// this pass finds a function call, it asks the appropriate optimizer to
133 /// validate the call (ValidateLibraryCall). If it is validated, then
134 /// the OptimizeCall method is also called.
135 /// @brief A ModulePass for optimizing well-known function calls.
136 class SimplifyLibCalls : public ModulePass
139 /// We need some target data for accurate signature details that are
140 /// target dependent. So we require target data in our AnalysisUsage.
141 /// @brief Require TargetData from AnalysisUsage.
142 virtual void getAnalysisUsage(AnalysisUsage& Info) const
144 // Ask that the TargetData analysis be performed before us so we can use
146 Info.addRequired<TargetData>();
149 /// For this pass, process all of the function calls in the module, calling
150 /// ValidateLibraryCall and OptimizeCall as appropriate.
151 /// @brief Run all the lib call optimizations on a Module.
152 virtual bool runOnModule(Module &M)
158 // The call optimizations can be recursive. That is, the optimization might
159 // generate a call to another function which can also be optimized. This way
160 // we make the LibCallOptimization instances very specific to the case they
161 // handle. It also means we need to keep running over the function calls in
162 // the module until we don't get any more optimizations possible.
163 bool found_optimization = false;
166 found_optimization = false;
167 for (Module::iterator FI = M.begin(), FE = M.end(); FI != FE; ++FI)
169 // All the "well-known" functions are external and have external linkage
170 // because they live in a runtime library somewhere and were (probably)
171 // not compiled by LLVM. So, we only act on external functions that
172 // have external linkage and non-empty uses.
173 if (!FI->isExternal() || !FI->hasExternalLinkage() || FI->use_empty())
176 // Get the optimization class that pertains to this function
177 LibCallOptimization* CO = optlist[FI->getName().c_str()];
181 // Make sure the called function is suitable for the optimization
182 if (!CO->ValidateCalledFunction(FI,*this))
185 // Loop over each of the uses of the function
186 for (Value::use_iterator UI = FI->use_begin(), UE = FI->use_end();
189 // If the use of the function is a call instruction
190 if (CallInst* CI = dyn_cast<CallInst>(*UI++))
192 // Do the optimization on the LibCallOptimization.
193 if (CO->OptimizeCall(CI,*this))
195 ++SimplifiedLibCalls;
196 found_optimization = result = true;
204 } while (found_optimization);
208 /// @brief Return the *current* module we're working on.
209 Module* getModule() const { return M; }
211 /// @brief Return the *current* target data for the module we're working on.
212 TargetData* getTargetData() const { return TD; }
214 /// @brief Return the size_t type -- syntactic shortcut
215 const Type* getIntPtrType() const { return TD->getIntPtrType(); }
217 /// @brief Return a Function* for the fputc libcall
218 Function* get_fputc(const Type* FILEptr_type)
222 std::vector<const Type*> args;
223 args.push_back(Type::IntTy);
224 args.push_back(FILEptr_type);
225 FunctionType* fputc_type =
226 FunctionType::get(Type::IntTy, args, false);
227 fputc_func = M->getOrInsertFunction("fputc",fputc_type);
232 /// @brief Return a Function* for the fwrite libcall
233 Function* get_fwrite(const Type* FILEptr_type)
237 std::vector<const Type*> args;
238 args.push_back(PointerType::get(Type::SByteTy));
239 args.push_back(TD->getIntPtrType());
240 args.push_back(TD->getIntPtrType());
241 args.push_back(FILEptr_type);
242 FunctionType* fwrite_type =
243 FunctionType::get(TD->getIntPtrType(), args, false);
244 fwrite_func = M->getOrInsertFunction("fwrite",fwrite_type);
249 /// @brief Return a Function* for the sqrt libcall
254 std::vector<const Type*> args;
255 args.push_back(Type::DoubleTy);
256 FunctionType* sqrt_type =
257 FunctionType::get(Type::DoubleTy, args, false);
258 sqrt_func = M->getOrInsertFunction("sqrt",sqrt_type);
263 /// @brief Return a Function* for the strlen libcall
264 Function* get_strcpy()
268 std::vector<const Type*> args;
269 args.push_back(PointerType::get(Type::SByteTy));
270 args.push_back(PointerType::get(Type::SByteTy));
271 FunctionType* strcpy_type =
272 FunctionType::get(PointerType::get(Type::SByteTy), args, false);
273 strcpy_func = M->getOrInsertFunction("strcpy",strcpy_type);
278 /// @brief Return a Function* for the strlen libcall
279 Function* get_strlen()
283 std::vector<const Type*> args;
284 args.push_back(PointerType::get(Type::SByteTy));
285 FunctionType* strlen_type =
286 FunctionType::get(TD->getIntPtrType(), args, false);
287 strlen_func = M->getOrInsertFunction("strlen",strlen_type);
292 /// @brief Return a Function* for the memchr libcall
293 Function* get_memchr()
297 std::vector<const Type*> args;
298 args.push_back(PointerType::get(Type::SByteTy));
299 args.push_back(Type::IntTy);
300 args.push_back(TD->getIntPtrType());
301 FunctionType* memchr_type = FunctionType::get(
302 PointerType::get(Type::SByteTy), args, false);
303 memchr_func = M->getOrInsertFunction("memchr",memchr_type);
308 /// @brief Return a Function* for the memcpy libcall
309 Function* get_memcpy()
313 // Note: this is for llvm.memcpy intrinsic
314 std::vector<const Type*> args;
315 args.push_back(PointerType::get(Type::SByteTy));
316 args.push_back(PointerType::get(Type::SByteTy));
317 args.push_back(Type::UIntTy);
318 args.push_back(Type::UIntTy);
319 FunctionType* memcpy_type = FunctionType::get(Type::VoidTy, args, false);
320 memcpy_func = M->getOrInsertFunction("llvm.memcpy",memcpy_type);
326 /// @brief Reset our cached data for a new Module
327 void reset(Module& mod)
330 TD = &getAnalysis<TargetData>();
341 Function* fputc_func; ///< Cached fputc function
342 Function* fwrite_func; ///< Cached fwrite function
343 Function* memcpy_func; ///< Cached llvm.memcpy function
344 Function* memchr_func; ///< Cached memchr function
345 Function* sqrt_func; ///< Cached sqrt function
346 Function* strcpy_func; ///< Cached strcpy function
347 Function* strlen_func; ///< Cached strlen function
348 Module* M; ///< Cached Module
349 TargetData* TD; ///< Cached TargetData
353 RegisterOpt<SimplifyLibCalls>
354 X("simplify-libcalls","Simplify well-known library calls");
356 } // anonymous namespace
358 // The only public symbol in this file which just instantiates the pass object
359 ModulePass *llvm::createSimplifyLibCallsPass()
361 return new SimplifyLibCalls();
364 // Classes below here, in the anonymous namespace, are all subclasses of the
365 // LibCallOptimization class, each implementing all optimizations possible for a
366 // single well-known library call. Each has a static singleton instance that
367 // auto registers it into the "optlist" global above.
370 // Forward declare utility functions.
371 bool getConstantStringLength(Value* V, uint64_t& len, ConstantArray** A = 0 );
372 Value *CastToCStr(Value *V, Instruction &IP);
374 /// This LibCallOptimization will find instances of a call to "exit" that occurs
375 /// within the "main" function and change it to a simple "ret" instruction with
376 /// the same value passed to the exit function. When this is done, it splits the
377 /// basic block at the exit(3) call and deletes the call instruction.
378 /// @brief Replace calls to exit in main with a simple return
379 struct ExitInMainOptimization : public LibCallOptimization
381 ExitInMainOptimization() : LibCallOptimization("exit",
382 "Number of 'exit' calls simplified") {}
383 virtual ~ExitInMainOptimization() {}
385 // Make sure the called function looks like exit (int argument, int return
386 // type, external linkage, not varargs).
387 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC)
389 if (f->arg_size() >= 1)
390 if (f->arg_begin()->getType()->isInteger())
395 virtual bool OptimizeCall(CallInst* ci, SimplifyLibCalls& SLC)
397 // To be careful, we check that the call to exit is coming from "main", that
398 // main has external linkage, and the return type of main and the argument
399 // to exit have the same type.
400 Function *from = ci->getParent()->getParent();
401 if (from->hasExternalLinkage())
402 if (from->getReturnType() == ci->getOperand(1)->getType())
403 if (from->getName() == "main")
405 // Okay, time to actually do the optimization. First, get the basic
406 // block of the call instruction
407 BasicBlock* bb = ci->getParent();
409 // Create a return instruction that we'll replace the call with.
410 // Note that the argument of the return is the argument of the call
412 ReturnInst* ri = new ReturnInst(ci->getOperand(1), ci);
414 // Split the block at the call instruction which places it in a new
416 bb->splitBasicBlock(ci);
418 // The block split caused a branch instruction to be inserted into
419 // the end of the original block, right after the return instruction
420 // that we put there. That's not a valid block, so delete the branch
422 bb->getInstList().pop_back();
424 // Now we can finally get rid of the call instruction which now lives
425 // in the new basic block.
426 ci->eraseFromParent();
428 // Optimization succeeded, return true.
431 // We didn't pass the criteria for this optimization so return false
434 } ExitInMainOptimizer;
436 /// This LibCallOptimization will simplify a call to the strcat library
437 /// function. The simplification is possible only if the string being
438 /// concatenated is a constant array or a constant expression that results in
439 /// a constant string. In this case we can replace it with strlen + llvm.memcpy
440 /// of the constant string. Both of these calls are further reduced, if possible
441 /// on subsequent passes.
442 /// @brief Simplify the strcat library function.
443 struct StrCatOptimization : public LibCallOptimization
446 /// @brief Default constructor
447 StrCatOptimization() : LibCallOptimization("strcat",
448 "Number of 'strcat' calls simplified") {}
451 /// @breif Destructor
452 virtual ~StrCatOptimization() {}
454 /// @brief Make sure that the "strcat" function has the right prototype
455 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC)
457 if (f->getReturnType() == PointerType::get(Type::SByteTy))
458 if (f->arg_size() == 2)
460 Function::const_arg_iterator AI = f->arg_begin();
461 if (AI++->getType() == PointerType::get(Type::SByteTy))
462 if (AI->getType() == PointerType::get(Type::SByteTy))
464 // Indicate this is a suitable call type.
471 /// @brief Optimize the strcat library function
472 virtual bool OptimizeCall(CallInst* ci, SimplifyLibCalls& SLC)
474 // Extract some information from the instruction
475 Module* M = ci->getParent()->getParent()->getParent();
476 Value* dest = ci->getOperand(1);
477 Value* src = ci->getOperand(2);
479 // Extract the initializer (while making numerous checks) from the
480 // source operand of the call to strcat. If we get null back, one of
481 // a variety of checks in get_GVInitializer failed
483 if (!getConstantStringLength(src,len))
486 // Handle the simple, do-nothing case
489 ci->replaceAllUsesWith(dest);
490 ci->eraseFromParent();
494 // Increment the length because we actually want to memcpy the null
495 // terminator as well.
498 // We need to find the end of the destination string. That's where the
499 // memory is to be moved to. We just generate a call to strlen (further
500 // optimized in another pass). Note that the SLC.get_strlen() call
501 // caches the Function* for us.
502 CallInst* strlen_inst =
503 new CallInst(SLC.get_strlen(), dest, dest->getName()+".len",ci);
505 // Now that we have the destination's length, we must index into the
506 // destination's pointer to get the actual memcpy destination (end of
507 // the string .. we're concatenating).
508 std::vector<Value*> idx;
509 idx.push_back(strlen_inst);
510 GetElementPtrInst* gep =
511 new GetElementPtrInst(dest,idx,dest->getName()+".indexed",ci);
513 // We have enough information to now generate the memcpy call to
514 // do the concatenation for us.
515 std::vector<Value*> vals;
516 vals.push_back(gep); // destination
517 vals.push_back(ci->getOperand(2)); // source
518 vals.push_back(ConstantUInt::get(Type::UIntTy,len)); // length
519 vals.push_back(ConstantUInt::get(Type::UIntTy,1)); // alignment
520 new CallInst(SLC.get_memcpy(), vals, "", ci);
522 // Finally, substitute the first operand of the strcat call for the
523 // strcat call itself since strcat returns its first operand; and,
524 // kill the strcat CallInst.
525 ci->replaceAllUsesWith(dest);
526 ci->eraseFromParent();
531 /// This LibCallOptimization will simplify a call to the strchr library
532 /// function. It optimizes out cases where the arguments are both constant
533 /// and the result can be determined statically.
534 /// @brief Simplify the strcmp library function.
535 struct StrChrOptimization : public LibCallOptimization
538 StrChrOptimization() : LibCallOptimization("strchr",
539 "Number of 'strchr' calls simplified") {}
540 virtual ~StrChrOptimization() {}
542 /// @brief Make sure that the "strchr" function has the right prototype
543 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC)
545 if (f->getReturnType() == PointerType::get(Type::SByteTy) &&
551 /// @brief Perform the strchr optimizations
552 virtual bool OptimizeCall(CallInst* ci, SimplifyLibCalls& SLC)
554 // If there aren't three operands, bail
555 if (ci->getNumOperands() != 3)
558 // Check that the first argument to strchr is a constant array of sbyte.
559 // If it is, get the length and data, otherwise return false.
562 if (!getConstantStringLength(ci->getOperand(1),len,&CA))
565 // Check that the second argument to strchr is a constant int, return false
567 ConstantSInt* CSI = dyn_cast<ConstantSInt>(ci->getOperand(2));
570 // Just lower this to memchr since we know the length of the string as
572 Function* f = SLC.get_memchr();
573 std::vector<Value*> args;
574 args.push_back(ci->getOperand(1));
575 args.push_back(ci->getOperand(2));
576 args.push_back(ConstantUInt::get(SLC.getIntPtrType(),len));
577 ci->replaceAllUsesWith( new CallInst(f,args,ci->getName(),ci));
578 ci->eraseFromParent();
582 // Get the character we're looking for
583 int64_t chr = CSI->getValue();
585 // Compute the offset
587 bool char_found = false;
588 for (uint64_t i = 0; i < len; ++i)
590 if (ConstantSInt* CI = dyn_cast<ConstantSInt>(CA->getOperand(i)))
592 // Check for the null terminator
593 if (CI->isNullValue())
594 break; // we found end of string
595 else if (CI->getValue() == chr)
604 // strchr(s,c) -> offset_of_in(c,s)
605 // (if c is a constant integer and s is a constant string)
608 std::vector<Value*> indices;
609 indices.push_back(ConstantUInt::get(Type::ULongTy,offset));
610 GetElementPtrInst* GEP = new GetElementPtrInst(ci->getOperand(1),indices,
611 ci->getOperand(1)->getName()+".strchr",ci);
612 ci->replaceAllUsesWith(GEP);
615 ci->replaceAllUsesWith(
616 ConstantPointerNull::get(PointerType::get(Type::SByteTy)));
618 ci->eraseFromParent();
623 /// This LibCallOptimization will simplify a call to the strcmp library
624 /// function. It optimizes out cases where one or both arguments are constant
625 /// and the result can be determined statically.
626 /// @brief Simplify the strcmp library function.
627 struct StrCmpOptimization : public LibCallOptimization
630 StrCmpOptimization() : LibCallOptimization("strcmp",
631 "Number of 'strcmp' calls simplified") {}
632 virtual ~StrCmpOptimization() {}
634 /// @brief Make sure that the "strcmp" function has the right prototype
635 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC)
637 if (f->getReturnType() == Type::IntTy && f->arg_size() == 2)
642 /// @brief Perform the strcmp optimization
643 virtual bool OptimizeCall(CallInst* ci, SimplifyLibCalls& SLC)
645 // First, check to see if src and destination are the same. If they are,
646 // then the optimization is to replace the CallInst with a constant 0
647 // because the call is a no-op.
648 Value* s1 = ci->getOperand(1);
649 Value* s2 = ci->getOperand(2);
653 ci->replaceAllUsesWith(ConstantInt::get(Type::IntTy,0));
654 ci->eraseFromParent();
658 bool isstr_1 = false;
661 if (getConstantStringLength(s1,len_1,&A1))
666 // strcmp("",x) -> *x
668 new LoadInst(CastToCStr(s2,*ci), ci->getName()+".load",ci);
670 new CastInst(load,Type::IntTy,ci->getName()+".int",ci);
671 ci->replaceAllUsesWith(cast);
672 ci->eraseFromParent();
677 bool isstr_2 = false;
680 if (getConstantStringLength(s2,len_2,&A2))
685 // strcmp(x,"") -> *x
687 new LoadInst(CastToCStr(s1,*ci),ci->getName()+".val",ci);
689 new CastInst(load,Type::IntTy,ci->getName()+".int",ci);
690 ci->replaceAllUsesWith(cast);
691 ci->eraseFromParent();
696 if (isstr_1 && isstr_2)
698 // strcmp(x,y) -> cnst (if both x and y are constant strings)
699 std::string str1 = A1->getAsString();
700 std::string str2 = A2->getAsString();
701 int result = strcmp(str1.c_str(), str2.c_str());
702 ci->replaceAllUsesWith(ConstantSInt::get(Type::IntTy,result));
703 ci->eraseFromParent();
710 /// This LibCallOptimization will simplify a call to the strncmp library
711 /// function. It optimizes out cases where one or both arguments are constant
712 /// and the result can be determined statically.
713 /// @brief Simplify the strncmp library function.
714 struct StrNCmpOptimization : public LibCallOptimization
717 StrNCmpOptimization() : LibCallOptimization("strncmp",
718 "Number of 'strncmp' calls simplified") {}
719 virtual ~StrNCmpOptimization() {}
721 /// @brief Make sure that the "strncmp" function has the right prototype
722 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC)
724 if (f->getReturnType() == Type::IntTy && f->arg_size() == 3)
729 /// @brief Perform the strncpy optimization
730 virtual bool OptimizeCall(CallInst* ci, SimplifyLibCalls& SLC)
732 // First, check to see if src and destination are the same. If they are,
733 // then the optimization is to replace the CallInst with a constant 0
734 // because the call is a no-op.
735 Value* s1 = ci->getOperand(1);
736 Value* s2 = ci->getOperand(2);
739 // strncmp(x,x,l) -> 0
740 ci->replaceAllUsesWith(ConstantInt::get(Type::IntTy,0));
741 ci->eraseFromParent();
745 // Check the length argument, if it is Constant zero then the strings are
747 uint64_t len_arg = 0;
748 bool len_arg_is_const = false;
749 if (ConstantInt* len_CI = dyn_cast<ConstantInt>(ci->getOperand(3)))
751 len_arg_is_const = true;
752 len_arg = len_CI->getRawValue();
755 // strncmp(x,y,0) -> 0
756 ci->replaceAllUsesWith(ConstantInt::get(Type::IntTy,0));
757 ci->eraseFromParent();
762 bool isstr_1 = false;
765 if (getConstantStringLength(s1,len_1,&A1))
770 // strncmp("",x) -> *x
771 LoadInst* load = new LoadInst(s1,ci->getName()+".load",ci);
773 new CastInst(load,Type::IntTy,ci->getName()+".int",ci);
774 ci->replaceAllUsesWith(cast);
775 ci->eraseFromParent();
780 bool isstr_2 = false;
783 if (getConstantStringLength(s2,len_2,&A2))
788 // strncmp(x,"") -> *x
789 LoadInst* load = new LoadInst(s2,ci->getName()+".val",ci);
791 new CastInst(load,Type::IntTy,ci->getName()+".int",ci);
792 ci->replaceAllUsesWith(cast);
793 ci->eraseFromParent();
798 if (isstr_1 && isstr_2 && len_arg_is_const)
800 // strncmp(x,y,const) -> constant
801 std::string str1 = A1->getAsString();
802 std::string str2 = A2->getAsString();
803 int result = strncmp(str1.c_str(), str2.c_str(), len_arg);
804 ci->replaceAllUsesWith(ConstantSInt::get(Type::IntTy,result));
805 ci->eraseFromParent();
812 /// This LibCallOptimization will simplify a call to the strcpy library
813 /// function. Two optimizations are possible:
814 /// (1) If src and dest are the same and not volatile, just return dest
815 /// (2) If the src is a constant then we can convert to llvm.memmove
816 /// @brief Simplify the strcpy library function.
817 struct StrCpyOptimization : public LibCallOptimization
820 StrCpyOptimization() : LibCallOptimization("strcpy",
821 "Number of 'strcpy' calls simplified") {}
822 virtual ~StrCpyOptimization() {}
824 /// @brief Make sure that the "strcpy" function has the right prototype
825 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC)
827 if (f->getReturnType() == PointerType::get(Type::SByteTy))
828 if (f->arg_size() == 2)
830 Function::const_arg_iterator AI = f->arg_begin();
831 if (AI++->getType() == PointerType::get(Type::SByteTy))
832 if (AI->getType() == PointerType::get(Type::SByteTy))
834 // Indicate this is a suitable call type.
841 /// @brief Perform the strcpy optimization
842 virtual bool OptimizeCall(CallInst* ci, SimplifyLibCalls& SLC)
844 // First, check to see if src and destination are the same. If they are,
845 // then the optimization is to replace the CallInst with the destination
846 // because the call is a no-op. Note that this corresponds to the
847 // degenerate strcpy(X,X) case which should have "undefined" results
848 // according to the C specification. However, it occurs sometimes and
849 // we optimize it as a no-op.
850 Value* dest = ci->getOperand(1);
851 Value* src = ci->getOperand(2);
854 ci->replaceAllUsesWith(dest);
855 ci->eraseFromParent();
859 // Get the length of the constant string referenced by the second operand,
860 // the "src" parameter. Fail the optimization if we can't get the length
861 // (note that getConstantStringLength does lots of checks to make sure this
864 if (!getConstantStringLength(ci->getOperand(2),len))
867 // If the constant string's length is zero we can optimize this by just
868 // doing a store of 0 at the first byte of the destination
871 new StoreInst(ConstantInt::get(Type::SByteTy,0),ci->getOperand(1),ci);
872 ci->replaceAllUsesWith(dest);
873 ci->eraseFromParent();
877 // Increment the length because we actually want to memcpy the null
878 // terminator as well.
881 // Extract some information from the instruction
882 Module* M = ci->getParent()->getParent()->getParent();
884 // We have enough information to now generate the memcpy call to
885 // do the concatenation for us.
886 std::vector<Value*> vals;
887 vals.push_back(dest); // destination
888 vals.push_back(src); // source
889 vals.push_back(ConstantUInt::get(Type::UIntTy,len)); // length
890 vals.push_back(ConstantUInt::get(Type::UIntTy,1)); // alignment
891 new CallInst(SLC.get_memcpy(), vals, "", ci);
893 // Finally, substitute the first operand of the strcat call for the
894 // strcat call itself since strcat returns its first operand; and,
895 // kill the strcat CallInst.
896 ci->replaceAllUsesWith(dest);
897 ci->eraseFromParent();
902 /// This LibCallOptimization will simplify a call to the strlen library
903 /// function by replacing it with a constant value if the string provided to
904 /// it is a constant array.
905 /// @brief Simplify the strlen library function.
906 struct StrLenOptimization : public LibCallOptimization
908 StrLenOptimization() : LibCallOptimization("strlen",
909 "Number of 'strlen' calls simplified") {}
910 virtual ~StrLenOptimization() {}
912 /// @brief Make sure that the "strlen" function has the right prototype
913 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC)
915 if (f->getReturnType() == SLC.getTargetData()->getIntPtrType())
916 if (f->arg_size() == 1)
917 if (Function::const_arg_iterator AI = f->arg_begin())
918 if (AI->getType() == PointerType::get(Type::SByteTy))
923 /// @brief Perform the strlen optimization
924 virtual bool OptimizeCall(CallInst* ci, SimplifyLibCalls& SLC)
926 // Make sure we're dealing with an sbyte* here.
927 Value* str = ci->getOperand(1);
928 if (str->getType() != PointerType::get(Type::SByteTy))
931 // Does the call to strlen have exactly one use?
933 // Is that single use a binary operator?
934 if (BinaryOperator* bop = dyn_cast<BinaryOperator>(ci->use_back()))
935 // Is it compared against a constant integer?
936 if (ConstantInt* CI = dyn_cast<ConstantInt>(bop->getOperand(1)))
938 // Get the value the strlen result is compared to
939 uint64_t val = CI->getRawValue();
941 // If its compared against length 0 with == or !=
943 (bop->getOpcode() == Instruction::SetEQ ||
944 bop->getOpcode() == Instruction::SetNE))
946 // strlen(x) != 0 -> *x != 0
947 // strlen(x) == 0 -> *x == 0
948 LoadInst* load = new LoadInst(str,str->getName()+".first",ci);
949 BinaryOperator* rbop = BinaryOperator::create(bop->getOpcode(),
950 load, ConstantSInt::get(Type::SByteTy,0),
951 bop->getName()+".strlen", ci);
952 bop->replaceAllUsesWith(rbop);
953 bop->eraseFromParent();
954 ci->eraseFromParent();
959 // Get the length of the constant string operand
961 if (!getConstantStringLength(ci->getOperand(1),len))
964 // strlen("xyz") -> 3 (for example)
965 ci->replaceAllUsesWith(
966 ConstantInt::get(SLC.getTargetData()->getIntPtrType(),len));
967 ci->eraseFromParent();
972 /// This LibCallOptimization will simplify a call to the memcpy library
973 /// function by expanding it out to a single store of size 0, 1, 2, 4, or 8
974 /// bytes depending on the length of the string and the alignment. Additional
975 /// optimizations are possible in code generation (sequence of immediate store)
976 /// @brief Simplify the memcpy library function.
977 struct LLVMMemCpyOptimization : public LibCallOptimization
979 /// @brief Default Constructor
980 LLVMMemCpyOptimization() : LibCallOptimization("llvm.memcpy",
981 "Number of 'llvm.memcpy' calls simplified") {}
984 /// @brief Subclass Constructor
985 LLVMMemCpyOptimization(const char* fname, const char* desc)
986 : LibCallOptimization(fname, desc) {}
988 /// @brief Destructor
989 virtual ~LLVMMemCpyOptimization() {}
991 /// @brief Make sure that the "memcpy" function has the right prototype
992 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& TD)
994 // Just make sure this has 4 arguments per LLVM spec.
995 return (f->arg_size() == 4);
998 /// Because of alignment and instruction information that we don't have, we
999 /// leave the bulk of this to the code generators. The optimization here just
1000 /// deals with a few degenerate cases where the length of the string and the
1001 /// alignment match the sizes of our intrinsic types so we can do a load and
1002 /// store instead of the memcpy call.
1003 /// @brief Perform the memcpy optimization.
1004 virtual bool OptimizeCall(CallInst* ci, SimplifyLibCalls& TD)
1006 // Make sure we have constant int values to work with
1007 ConstantInt* LEN = dyn_cast<ConstantInt>(ci->getOperand(3));
1010 ConstantInt* ALIGN = dyn_cast<ConstantInt>(ci->getOperand(4));
1014 // If the length is larger than the alignment, we can't optimize
1015 uint64_t len = LEN->getRawValue();
1016 uint64_t alignment = ALIGN->getRawValue();
1018 alignment = 1; // Alignment 0 is identity for alignment 1
1019 if (len > alignment)
1022 // Get the type we will cast to, based on size of the string
1023 Value* dest = ci->getOperand(1);
1024 Value* src = ci->getOperand(2);
1029 // memcpy(d,s,0,a) -> noop
1030 ci->eraseFromParent();
1032 case 1: castType = Type::SByteTy; break;
1033 case 2: castType = Type::ShortTy; break;
1034 case 4: castType = Type::IntTy; break;
1035 case 8: castType = Type::LongTy; break;
1040 // Cast source and dest to the right sized primitive and then load/store
1042 new CastInst(src,PointerType::get(castType),src->getName()+".cast",ci);
1043 CastInst* DestCast =
1044 new CastInst(dest,PointerType::get(castType),dest->getName()+".cast",ci);
1045 LoadInst* LI = new LoadInst(SrcCast,SrcCast->getName()+".val",ci);
1046 StoreInst* SI = new StoreInst(LI, DestCast, ci);
1047 ci->eraseFromParent();
1050 } LLVMMemCpyOptimizer;
1052 /// This LibCallOptimization will simplify a call to the memmove library
1053 /// function. It is identical to MemCopyOptimization except for the name of
1055 /// @brief Simplify the memmove library function.
1056 struct LLVMMemMoveOptimization : public LLVMMemCpyOptimization
1058 /// @brief Default Constructor
1059 LLVMMemMoveOptimization() : LLVMMemCpyOptimization("llvm.memmove",
1060 "Number of 'llvm.memmove' calls simplified") {}
1062 } LLVMMemMoveOptimizer;
1064 /// This LibCallOptimization will simplify a call to the memset library
1065 /// function by expanding it out to a single store of size 0, 1, 2, 4, or 8
1066 /// bytes depending on the length argument.
1067 struct LLVMMemSetOptimization : public LibCallOptimization
1069 /// @brief Default Constructor
1070 LLVMMemSetOptimization() : LibCallOptimization("llvm.memset",
1071 "Number of 'llvm.memset' calls simplified") {}
1074 /// @brief Destructor
1075 virtual ~LLVMMemSetOptimization() {}
1077 /// @brief Make sure that the "memset" function has the right prototype
1078 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& TD)
1080 // Just make sure this has 3 arguments per LLVM spec.
1081 return (f->arg_size() == 4);
1084 /// Because of alignment and instruction information that we don't have, we
1085 /// leave the bulk of this to the code generators. The optimization here just
1086 /// deals with a few degenerate cases where the length parameter is constant
1087 /// and the alignment matches the sizes of our intrinsic types so we can do
1088 /// store instead of the memcpy call. Other calls are transformed into the
1089 /// llvm.memset intrinsic.
1090 /// @brief Perform the memset optimization.
1091 virtual bool OptimizeCall(CallInst* ci, SimplifyLibCalls& TD)
1093 // Make sure we have constant int values to work with
1094 ConstantInt* LEN = dyn_cast<ConstantInt>(ci->getOperand(3));
1097 ConstantInt* ALIGN = dyn_cast<ConstantInt>(ci->getOperand(4));
1101 // Extract the length and alignment
1102 uint64_t len = LEN->getRawValue();
1103 uint64_t alignment = ALIGN->getRawValue();
1105 // Alignment 0 is identity for alignment 1
1109 // If the length is zero, this is a no-op
1112 // memset(d,c,0,a) -> noop
1113 ci->eraseFromParent();
1117 // If the length is larger than the alignment, we can't optimize
1118 if (len > alignment)
1121 // Make sure we have a constant ubyte to work with so we can extract
1122 // the value to be filled.
1123 ConstantUInt* FILL = dyn_cast<ConstantUInt>(ci->getOperand(2));
1126 if (FILL->getType() != Type::UByteTy)
1129 // memset(s,c,n) -> store s, c (for n=1,2,4,8)
1131 // Extract the fill character
1132 uint64_t fill_char = FILL->getValue();
1133 uint64_t fill_value = fill_char;
1135 // Get the type we will cast to, based on size of memory area to fill, and
1136 // and the value we will store there.
1137 Value* dest = ci->getOperand(1);
1142 castType = Type::UByteTy;
1145 castType = Type::UShortTy;
1146 fill_value |= fill_char << 8;
1149 castType = Type::UIntTy;
1150 fill_value |= fill_char << 8 | fill_char << 16 | fill_char << 24;
1153 castType = Type::ULongTy;
1154 fill_value |= fill_char << 8 | fill_char << 16 | fill_char << 24;
1155 fill_value |= fill_char << 32 | fill_char << 40 | fill_char << 48;
1156 fill_value |= fill_char << 56;
1162 // Cast dest to the right sized primitive and then load/store
1163 CastInst* DestCast =
1164 new CastInst(dest,PointerType::get(castType),dest->getName()+".cast",ci);
1165 new StoreInst(ConstantUInt::get(castType,fill_value),DestCast, ci);
1166 ci->eraseFromParent();
1169 } LLVMMemSetOptimizer;
1171 /// This LibCallOptimization will simplify calls to the "pow" library
1172 /// function. It looks for cases where the result of pow is well known and
1173 /// substitutes the appropriate value.
1174 /// @brief Simplify the pow library function.
1175 struct PowOptimization : public LibCallOptimization
1178 /// @brief Default Constructor
1179 PowOptimization() : LibCallOptimization("pow",
1180 "Number of 'pow' calls simplified") {}
1182 /// @brief Destructor
1183 virtual ~PowOptimization() {}
1185 /// @brief Make sure that the "pow" function has the right prototype
1186 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC)
1188 // Just make sure this has 2 arguments
1189 return (f->arg_size() == 2);
1192 /// @brief Perform the pow optimization.
1193 virtual bool OptimizeCall(CallInst* ci, SimplifyLibCalls& SLC)
1195 const Type *Ty = cast<Function>(ci->getOperand(0))->getReturnType();
1196 Value* base = ci->getOperand(1);
1197 Value* expn = ci->getOperand(2);
1198 if (ConstantFP *Op1 = dyn_cast<ConstantFP>(base)) {
1199 double Op1V = Op1->getValue();
1202 // pow(1.0,x) -> 1.0
1203 ci->replaceAllUsesWith(ConstantFP::get(Ty,1.0));
1204 ci->eraseFromParent();
1208 else if (ConstantFP* Op2 = dyn_cast<ConstantFP>(expn))
1210 double Op2V = Op2->getValue();
1213 // pow(x,0.0) -> 1.0
1214 ci->replaceAllUsesWith(ConstantFP::get(Ty,1.0));
1215 ci->eraseFromParent();
1218 else if (Op2V == 0.5)
1220 // pow(x,0.5) -> sqrt(x)
1221 CallInst* sqrt_inst = new CallInst(SLC.get_sqrt(), base,
1222 ci->getName()+".pow",ci);
1223 ci->replaceAllUsesWith(sqrt_inst);
1224 ci->eraseFromParent();
1227 else if (Op2V == 1.0)
1230 ci->replaceAllUsesWith(base);
1231 ci->eraseFromParent();
1234 else if (Op2V == -1.0)
1236 // pow(x,-1.0) -> 1.0/x
1237 BinaryOperator* div_inst= BinaryOperator::create(Instruction::Div,
1238 ConstantFP::get(Ty,1.0), base, ci->getName()+".pow", ci);
1239 ci->replaceAllUsesWith(div_inst);
1240 ci->eraseFromParent();
1244 return false; // opt failed
1248 /// This LibCallOptimization will simplify calls to the "fprintf" library
1249 /// function. It looks for cases where the result of fprintf is not used and the
1250 /// operation can be reduced to something simpler.
1251 /// @brief Simplify the pow library function.
1252 struct FPrintFOptimization : public LibCallOptimization
1255 /// @brief Default Constructor
1256 FPrintFOptimization() : LibCallOptimization("fprintf",
1257 "Number of 'fprintf' calls simplified") {}
1259 /// @brief Destructor
1260 virtual ~FPrintFOptimization() {}
1262 /// @brief Make sure that the "fprintf" function has the right prototype
1263 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC)
1265 // Just make sure this has at least 2 arguments
1266 return (f->arg_size() >= 2);
1269 /// @brief Perform the fprintf optimization.
1270 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->hasNUses(0))
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)
1290 // Make sure there's no % in the constant array
1291 for (unsigned i = 0; i < len; ++i)
1293 if (ConstantInt* CI = dyn_cast<ConstantInt>(CA->getOperand(i)))
1295 // Check for the null terminator
1296 if (CI->getRawValue() == '%')
1297 return false; // we found end of string
1303 // fprintf(file,fmt) -> fwrite(fmt,strlen(fmt),file)
1304 const Type* FILEptr_type = ci->getOperand(1)->getType();
1305 Function* fwrite_func = SLC.get_fwrite(FILEptr_type);
1309 // Make sure that the fprintf() and fwrite() functions both take the
1310 // same type of char pointer.
1311 if (ci->getOperand(2)->getType() !=
1312 fwrite_func->getFunctionType()->getParamType(0))
1315 std::vector<Value*> args;
1316 args.push_back(ci->getOperand(2));
1317 args.push_back(ConstantUInt::get(SLC.getIntPtrType(),len));
1318 args.push_back(ConstantUInt::get(SLC.getIntPtrType(),1));
1319 args.push_back(ci->getOperand(1));
1320 new CallInst(fwrite_func,args,ci->getName(),ci);
1321 ci->replaceAllUsesWith(ConstantSInt::get(Type::IntTy,len));
1322 ci->eraseFromParent();
1326 // The remaining optimizations require the format string to be length 2
1331 // The first character has to be a %
1332 if (ConstantInt* CI = dyn_cast<ConstantInt>(CA->getOperand(0)))
1333 if (CI->getRawValue() != '%')
1336 // Get the second character and switch on its value
1337 ConstantInt* CI = dyn_cast<ConstantInt>(CA->getOperand(1));
1338 switch (CI->getRawValue())
1343 ConstantArray* CA = 0;
1344 if (!getConstantStringLength(ci->getOperand(3), len, &CA))
1347 // fprintf(file,"%s",str) -> fwrite(fmt,strlen(fmt),1,file)
1348 const Type* FILEptr_type = ci->getOperand(1)->getType();
1349 Function* fwrite_func = SLC.get_fwrite(FILEptr_type);
1352 std::vector<Value*> args;
1353 args.push_back(CastToCStr(ci->getOperand(3), *ci));
1354 args.push_back(ConstantUInt::get(SLC.getIntPtrType(),len));
1355 args.push_back(ConstantUInt::get(SLC.getIntPtrType(),1));
1356 args.push_back(ci->getOperand(1));
1357 new CallInst(fwrite_func,args,ci->getName(),ci);
1358 ci->replaceAllUsesWith(ConstantSInt::get(Type::IntTy,len));
1363 ConstantInt* CI = dyn_cast<ConstantInt>(ci->getOperand(3));
1367 const Type* FILEptr_type = ci->getOperand(1)->getType();
1368 Function* fputc_func = SLC.get_fputc(FILEptr_type);
1371 CastInst* cast = new CastInst(CI,Type::IntTy,CI->getName()+".int",ci);
1372 new CallInst(fputc_func,cast,ci->getOperand(1),"",ci);
1373 ci->replaceAllUsesWith(ConstantSInt::get(Type::IntTy,1));
1379 ci->eraseFromParent();
1384 /// This LibCallOptimization will simplify calls to the "sprintf" library
1385 /// function. It looks for cases where the result of sprintf is not used and the
1386 /// operation can be reduced to something simpler.
1387 /// @brief Simplify the pow library function.
1388 struct SPrintFOptimization : public LibCallOptimization
1391 /// @brief Default Constructor
1392 SPrintFOptimization() : LibCallOptimization("sprintf",
1393 "Number of 'sprintf' calls simplified") {}
1395 /// @brief Destructor
1396 virtual ~SPrintFOptimization() {}
1398 /// @brief Make sure that the "fprintf" function has the right prototype
1399 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC)
1401 // Just make sure this has at least 2 arguments
1402 return (f->getReturnType() == Type::IntTy && f->arg_size() >= 2);
1405 /// @brief Perform the sprintf optimization.
1406 virtual bool OptimizeCall(CallInst* ci, SimplifyLibCalls& SLC)
1408 // If the call has more than 3 operands, we can't optimize it
1409 if (ci->getNumOperands() > 4 || ci->getNumOperands() < 3)
1412 // All the optimizations depend on the length of the second argument and the
1413 // fact that it is a constant string array. Check that now
1415 ConstantArray* CA = 0;
1416 if (!getConstantStringLength(ci->getOperand(2), len, &CA))
1419 if (ci->getNumOperands() == 3)
1423 // If the length is 0, we just need to store a null byte
1424 new StoreInst(ConstantInt::get(Type::SByteTy,0),ci->getOperand(1),ci);
1425 ci->replaceAllUsesWith(ConstantSInt::get(Type::IntTy,0));
1426 ci->eraseFromParent();
1430 // Make sure there's no % in the constant array
1431 for (unsigned i = 0; i < len; ++i)
1433 if (ConstantInt* CI = dyn_cast<ConstantInt>(CA->getOperand(i)))
1435 // Check for the null terminator
1436 if (CI->getRawValue() == '%')
1437 return false; // we found a %, can't optimize
1440 return false; // initializer is not constant int, can't optimize
1443 // Increment length because we want to copy the null byte too
1446 // sprintf(str,fmt) -> llvm.memcpy(str,fmt,strlen(fmt),1)
1447 Function* memcpy_func = SLC.get_memcpy();
1450 std::vector<Value*> args;
1451 args.push_back(ci->getOperand(1));
1452 args.push_back(ci->getOperand(2));
1453 args.push_back(ConstantUInt::get(Type::UIntTy,len));
1454 args.push_back(ConstantUInt::get(Type::UIntTy,1));
1455 new CallInst(memcpy_func,args,"",ci);
1456 ci->replaceAllUsesWith(ConstantSInt::get(Type::IntTy,len));
1457 ci->eraseFromParent();
1461 // The remaining optimizations require the format string to be length 2
1466 // The first character has to be a %
1467 if (ConstantInt* CI = dyn_cast<ConstantInt>(CA->getOperand(0)))
1468 if (CI->getRawValue() != '%')
1471 // Get the second character and switch on its value
1472 ConstantInt* CI = dyn_cast<ConstantInt>(CA->getOperand(1));
1473 switch (CI->getRawValue())
1478 if (ci->hasNUses(0))
1480 // sprintf(dest,"%s",str) -> strcpy(dest,str)
1481 Function* strcpy_func = SLC.get_strcpy();
1484 std::vector<Value*> args;
1485 args.push_back(CastToCStr(ci->getOperand(1), *ci));
1486 args.push_back(CastToCStr(ci->getOperand(3), *ci));
1487 new CallInst(strcpy_func,args,"",ci);
1489 else if (getConstantStringLength(ci->getOperand(3),len))
1491 // sprintf(dest,"%s",cstr) -> llvm.memcpy(dest,str,strlen(str),1)
1492 len++; // get the null-terminator
1493 Function* memcpy_func = SLC.get_memcpy();
1496 std::vector<Value*> args;
1497 args.push_back(CastToCStr(ci->getOperand(1), *ci));
1498 args.push_back(CastToCStr(ci->getOperand(3), *ci));
1499 args.push_back(ConstantUInt::get(Type::UIntTy,len));
1500 args.push_back(ConstantUInt::get(Type::UIntTy,1));
1501 new CallInst(memcpy_func,args,"",ci);
1502 ci->replaceAllUsesWith(ConstantSInt::get(Type::IntTy,len));
1508 // sprintf(dest,"%c",chr) -> store chr, dest
1510 new CastInst(ci->getOperand(3),Type::SByteTy,"char",ci);
1511 new StoreInst(cast, ci->getOperand(1), ci);
1512 GetElementPtrInst* gep = new GetElementPtrInst(ci->getOperand(1),
1513 ConstantUInt::get(Type::UIntTy,1),ci->getOperand(1)->getName()+".end",
1515 new StoreInst(ConstantInt::get(Type::SByteTy,0),gep,ci);
1516 ci->replaceAllUsesWith(ConstantSInt::get(Type::IntTy,1));
1522 ci->eraseFromParent();
1527 /// This LibCallOptimization will simplify calls to the "fputs" library
1528 /// function. It looks for cases where the result of fputs is not used and the
1529 /// operation can be reduced to something simpler.
1530 /// @brief Simplify the pow library function.
1531 struct PutsOptimization : public LibCallOptimization
1534 /// @brief Default Constructor
1535 PutsOptimization() : LibCallOptimization("fputs",
1536 "Number of 'fputs' calls simplified") {}
1538 /// @brief Destructor
1539 virtual ~PutsOptimization() {}
1541 /// @brief Make sure that the "fputs" function has the right prototype
1542 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC)
1544 // Just make sure this has 2 arguments
1545 return (f->arg_size() == 2);
1548 /// @brief Perform the fputs optimization.
1549 virtual bool OptimizeCall(CallInst* ci, SimplifyLibCalls& SLC)
1551 // If the result is used, none of these optimizations work
1552 if (!ci->hasNUses(0))
1555 // All the optimizations depend on the length of the first argument and the
1556 // fact that it is a constant string array. Check that now
1558 if (!getConstantStringLength(ci->getOperand(1), len))
1564 // fputs("",F) -> noop
1568 // fputs(s,F) -> fputc(s[0],F) (if s is constant and strlen(s) == 1)
1569 const Type* FILEptr_type = ci->getOperand(2)->getType();
1570 Function* fputc_func = SLC.get_fputc(FILEptr_type);
1573 LoadInst* loadi = new LoadInst(ci->getOperand(1),
1574 ci->getOperand(1)->getName()+".byte",ci);
1575 CastInst* casti = new CastInst(loadi,Type::IntTy,
1576 loadi->getName()+".int",ci);
1577 new CallInst(fputc_func,casti,ci->getOperand(2),"",ci);
1582 // fputs(s,F) -> fwrite(s,1,len,F) (if s is constant and strlen(s) > 1)
1583 const Type* FILEptr_type = ci->getOperand(2)->getType();
1584 Function* fwrite_func = SLC.get_fwrite(FILEptr_type);
1587 std::vector<Value*> parms;
1588 parms.push_back(ci->getOperand(1));
1589 parms.push_back(ConstantUInt::get(SLC.getIntPtrType(),len));
1590 parms.push_back(ConstantUInt::get(SLC.getIntPtrType(),1));
1591 parms.push_back(ci->getOperand(2));
1592 new CallInst(fwrite_func,parms,"",ci);
1596 ci->eraseFromParent();
1597 return true; // success
1601 /// This LibCallOptimization will simplify calls to the "isdigit" library
1602 /// function. It simply does range checks the parameter explicitly.
1603 /// @brief Simplify the isdigit library function.
1604 struct IsDigitOptimization : public LibCallOptimization
1607 /// @brief Default Constructor
1608 IsDigitOptimization() : LibCallOptimization("isdigit",
1609 "Number of 'isdigit' calls simplified") {}
1611 /// @brief Destructor
1612 virtual ~IsDigitOptimization() {}
1614 /// @brief Make sure that the "fputs" function has the right prototype
1615 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC)
1617 // Just make sure this has 1 argument
1618 return (f->arg_size() == 1);
1621 /// @brief Perform the toascii optimization.
1622 virtual bool OptimizeCall(CallInst* ci, SimplifyLibCalls& SLC)
1624 if (ConstantInt* CI = dyn_cast<ConstantInt>(ci->getOperand(1)))
1626 // isdigit(c) -> 0 or 1, if 'c' is constant
1627 uint64_t val = CI->getRawValue();
1628 if (val >= '0' && val <='9')
1629 ci->replaceAllUsesWith(ConstantSInt::get(Type::IntTy,1));
1631 ci->replaceAllUsesWith(ConstantSInt::get(Type::IntTy,0));
1632 ci->eraseFromParent();
1636 // isdigit(c) -> (unsigned)c - '0' <= 9
1638 new CastInst(ci->getOperand(1),Type::UIntTy,
1639 ci->getOperand(1)->getName()+".uint",ci);
1640 BinaryOperator* sub_inst = BinaryOperator::create(Instruction::Sub,cast,
1641 ConstantUInt::get(Type::UIntTy,0x30),
1642 ci->getOperand(1)->getName()+".sub",ci);
1643 SetCondInst* setcond_inst = new SetCondInst(Instruction::SetLE,sub_inst,
1644 ConstantUInt::get(Type::UIntTy,9),
1645 ci->getOperand(1)->getName()+".cmp",ci);
1647 new CastInst(setcond_inst,Type::IntTy,
1648 ci->getOperand(1)->getName()+".isdigit",ci);
1649 ci->replaceAllUsesWith(c2);
1650 ci->eraseFromParent();
1655 /// This LibCallOptimization will simplify calls to the "toascii" library
1656 /// function. It simply does the corresponding and operation to restrict the
1657 /// range of values to the ASCII character set (0-127).
1658 /// @brief Simplify the toascii library function.
1659 struct ToAsciiOptimization : public LibCallOptimization
1662 /// @brief Default Constructor
1663 ToAsciiOptimization() : LibCallOptimization("toascii",
1664 "Number of 'toascii' calls simplified") {}
1666 /// @brief Destructor
1667 virtual ~ToAsciiOptimization() {}
1669 /// @brief Make sure that the "fputs" function has the right prototype
1670 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC)
1672 // Just make sure this has 2 arguments
1673 return (f->arg_size() == 1);
1676 /// @brief Perform the toascii optimization.
1677 virtual bool OptimizeCall(CallInst* ci, SimplifyLibCalls& SLC)
1679 // toascii(c) -> (c & 0x7f)
1680 Value* chr = ci->getOperand(1);
1681 BinaryOperator* and_inst = BinaryOperator::create(Instruction::And,chr,
1682 ConstantInt::get(chr->getType(),0x7F),ci->getName()+".toascii",ci);
1683 ci->replaceAllUsesWith(and_inst);
1684 ci->eraseFromParent();
1689 /// This LibCallOptimization will simplify calls to the "ffs" library
1690 /// calls which find the first set bit in an int, long, or long long. The
1691 /// optimization is to compute the result at compile time if the argument is
1693 /// @brief Simplify the ffs library function.
1694 struct FFSOptimization : public LibCallOptimization
1697 /// @brief Subclass Constructor
1698 FFSOptimization(const char* funcName, const char* description)
1699 : LibCallOptimization(funcName, description)
1703 /// @brief Default Constructor
1704 FFSOptimization() : LibCallOptimization("ffs",
1705 "Number of 'ffs' calls simplified") {}
1707 /// @brief Destructor
1708 virtual ~FFSOptimization() {}
1710 /// @brief Make sure that the "fputs" function has the right prototype
1711 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC)
1713 // Just make sure this has 2 arguments
1714 return (f->arg_size() == 1 && f->getReturnType() == Type::IntTy);
1717 /// @brief Perform the ffs optimization.
1718 virtual bool OptimizeCall(CallInst* ci, SimplifyLibCalls& SLC)
1720 if (ConstantInt* CI = dyn_cast<ConstantInt>(ci->getOperand(1)))
1722 // ffs(cnst) -> bit#
1723 // ffsl(cnst) -> bit#
1724 // ffsll(cnst) -> bit#
1725 uint64_t val = CI->getRawValue();
1733 ci->replaceAllUsesWith(ConstantSInt::get(Type::IntTy, result));
1734 ci->eraseFromParent();
1738 // ffs(x) -> ( x == 0 ? 0 : llvm.cttz(x)+1)
1739 // ffsl(x) -> ( x == 0 ? 0 : llvm.cttz(x)+1)
1740 // ffsll(x) -> ( x == 0 ? 0 : llvm.cttz(x)+1)
1741 const Type* arg_type = ci->getOperand(1)->getType();
1742 std::vector<const Type*> args;
1743 args.push_back(arg_type);
1744 FunctionType* llvm_cttz_type = FunctionType::get(arg_type,args,false);
1746 SLC.getModule()->getOrInsertFunction("llvm.cttz",llvm_cttz_type);
1747 std::string inst_name(ci->getName()+".ffs");
1749 new CallInst(F, ci->getOperand(1), inst_name, ci);
1750 if (arg_type != Type::IntTy)
1751 call = new CastInst(call, Type::IntTy, inst_name, ci);
1752 BinaryOperator* add = BinaryOperator::create(Instruction::Add, call,
1753 ConstantSInt::get(Type::IntTy,1), inst_name, ci);
1754 SetCondInst* eq = new SetCondInst(Instruction::SetEQ,ci->getOperand(1),
1755 ConstantSInt::get(ci->getOperand(1)->getType(),0),inst_name,ci);
1756 SelectInst* select = new SelectInst(eq,ConstantSInt::get(Type::IntTy,0),add,
1758 ci->replaceAllUsesWith(select);
1759 ci->eraseFromParent();
1764 /// This LibCallOptimization will simplify calls to the "ffsl" library
1765 /// calls. It simply uses FFSOptimization for which the transformation is
1767 /// @brief Simplify the ffsl library function.
1768 struct FFSLOptimization : public FFSOptimization
1771 /// @brief Default Constructor
1772 FFSLOptimization() : FFSOptimization("ffsl",
1773 "Number of 'ffsl' calls simplified") {}
1777 /// This LibCallOptimization will simplify calls to the "ffsll" library
1778 /// calls. It simply uses FFSOptimization for which the transformation is
1780 /// @brief Simplify the ffsl library function.
1781 struct FFSLLOptimization : public FFSOptimization
1784 /// @brief Default Constructor
1785 FFSLLOptimization() : FFSOptimization("ffsll",
1786 "Number of 'ffsll' calls simplified") {}
1790 /// A function to compute the length of a null-terminated constant array of
1791 /// integers. This function can't rely on the size of the constant array
1792 /// because there could be a null terminator in the middle of the array.
1793 /// We also have to bail out if we find a non-integer constant initializer
1794 /// of one of the elements or if there is no null-terminator. The logic
1795 /// below checks each of these conditions and will return true only if all
1796 /// conditions are met. In that case, the \p len parameter is set to the length
1797 /// of the null-terminated string. If false is returned, the conditions were
1798 /// not met and len is set to 0.
1799 /// @brief Get the length of a constant string (null-terminated array).
1800 bool getConstantStringLength(Value* V, uint64_t& len, ConstantArray** CA )
1802 assert(V != 0 && "Invalid args to getConstantStringLength");
1803 len = 0; // make sure we initialize this
1805 // If the value is not a GEP instruction nor a constant expression with a
1806 // GEP instruction, then return false because ConstantArray can't occur
1808 if (GetElementPtrInst* GEPI = dyn_cast<GetElementPtrInst>(V))
1810 else if (ConstantExpr* CE = dyn_cast<ConstantExpr>(V))
1811 if (CE->getOpcode() == Instruction::GetElementPtr)
1818 // Make sure the GEP has exactly three arguments.
1819 if (GEP->getNumOperands() != 3)
1822 // Check to make sure that the first operand of the GEP is an integer and
1823 // has value 0 so that we are sure we're indexing into the initializer.
1824 if (ConstantInt* op1 = dyn_cast<ConstantInt>(GEP->getOperand(1)))
1826 if (!op1->isNullValue())
1832 // Ensure that the second operand is a ConstantInt. If it isn't then this
1833 // GEP is wonky and we're not really sure what were referencing into and
1834 // better of not optimizing it. While we're at it, get the second index
1835 // value. We'll need this later for indexing the ConstantArray.
1836 uint64_t start_idx = 0;
1837 if (ConstantInt* CI = dyn_cast<ConstantInt>(GEP->getOperand(2)))
1838 start_idx = CI->getRawValue();
1842 // The GEP instruction, constant or instruction, must reference a global
1843 // variable that is a constant and is initialized. The referenced constant
1844 // initializer is the array that we'll use for optimization.
1845 GlobalVariable* GV = dyn_cast<GlobalVariable>(GEP->getOperand(0));
1846 if (!GV || !GV->isConstant() || !GV->hasInitializer())
1849 // Get the initializer.
1850 Constant* INTLZR = GV->getInitializer();
1852 // Handle the ConstantAggregateZero case
1853 if (ConstantAggregateZero* CAZ = dyn_cast<ConstantAggregateZero>(INTLZR))
1855 // This is a degenerate case. The initializer is constant zero so the
1856 // length of the string must be zero.
1861 // Must be a Constant Array
1862 ConstantArray* A = dyn_cast<ConstantArray>(INTLZR);
1866 // Get the number of elements in the array
1867 uint64_t max_elems = A->getType()->getNumElements();
1869 // Traverse the constant array from start_idx (derived above) which is
1870 // the place the GEP refers to in the array.
1871 for ( len = start_idx; len < max_elems; len++)
1873 if (ConstantInt* CI = dyn_cast<ConstantInt>(A->getOperand(len)))
1875 // Check for the null terminator
1876 if (CI->isNullValue())
1877 break; // we found end of string
1880 return false; // This array isn't suitable, non-int initializer
1882 if (len >= max_elems)
1883 return false; // This array isn't null terminated
1885 // Subtract out the initial value from the length
1889 return true; // success!
1892 /// CastToCStr - Return V if it is an sbyte*, otherwise cast it to sbyte*,
1893 /// inserting the cast before IP, and return the cast.
1894 /// @brief Cast a value to a "C" string.
1895 Value *CastToCStr(Value *V, Instruction &IP) {
1896 const Type *SBPTy = PointerType::get(Type::SByteTy);
1897 if (V->getType() != SBPTy)
1898 return new CastInst(V, SBPTy, V->getName(), &IP);
1903 // Additional cases that we need to add to this file:
1906 // * cbrt(expN(X)) -> expN(x/3)
1907 // * cbrt(sqrt(x)) -> pow(x,1/6)
1908 // * cbrt(sqrt(x)) -> pow(x,1/9)
1911 // * cos(-x) -> cos(x)
1914 // * exp(log(x)) -> x
1917 // * isascii(c) -> ((c & ~0x7f) == 0)
1920 // * isdigit(c) -> (unsigned)(c) - '0' <= 9
1923 // * log(exp(x)) -> x
1924 // * log(x**y) -> y*log(x)
1925 // * log(exp(y)) -> y*log(e)
1926 // * log(exp2(y)) -> y*log(2)
1927 // * log(exp10(y)) -> y*log(10)
1928 // * log(sqrt(x)) -> 0.5*log(x)
1929 // * log(pow(x,y)) -> y*log(x)
1931 // lround, lroundf, lroundl:
1932 // * lround(cnst) -> cnst'
1935 // * memcmp(s1,s2,0) -> 0
1936 // * memcmp(x,x,l) -> 0
1937 // * memcmp(x,y,l) -> cnst
1938 // (if all arguments are constant and strlen(x) <= l and strlen(y) <= l)
1939 // * memcmp(x,y,1) -> *x - *y
1942 // * memmove(d,s,l,a) -> memcpy(d,s,l,a)
1943 // (if s is a global constant array)
1946 // * pow(exp(x),y) -> exp(x*y)
1947 // * pow(sqrt(x),y) -> pow(x,y*0.5)
1948 // * pow(pow(x,y),z)-> pow(x,y*z)
1951 // * puts("") -> fputc("\n",stdout) (how do we get "stdout"?)
1953 // round, roundf, roundl:
1954 // * round(cnst) -> cnst'
1957 // * signbit(cnst) -> cnst'
1958 // * signbit(nncst) -> 0 (if pstv is a non-negative constant)
1960 // sqrt, sqrtf, sqrtl:
1961 // * sqrt(expN(x)) -> expN(x*0.5)
1962 // * sqrt(Nroot(x)) -> pow(x,1/(2*N))
1963 // * sqrt(pow(x,y)) -> pow(|x|,y*0.5)
1966 // * stpcpy(str, "literal") ->
1967 // llvm.memcpy(str,"literal",strlen("literal")+1,1)
1969 // * strrchr(s,c) -> reverse_offset_of_in(c,s)
1970 // (if c is a constant integer and s is a constant string)
1971 // * strrchr(s1,0) -> strchr(s1,0)
1974 // * strncat(x,y,0) -> x
1975 // * strncat(x,y,0) -> x (if strlen(y) = 0)
1976 // * strncat(x,y,l) -> strcat(x,y) (if y and l are constants an l > strlen(y))
1979 // * strncpy(d,s,0) -> d
1980 // * strncpy(d,s,l) -> memcpy(d,s,l,1)
1981 // (if s and l are constants)
1984 // * strpbrk(s,a) -> offset_in_for(s,a)
1985 // (if s and a are both constant strings)
1986 // * strpbrk(s,"") -> 0
1987 // * strpbrk(s,a) -> strchr(s,a[0]) (if a is constant string of length 1)
1990 // * strspn(s,a) -> const_int (if both args are constant)
1991 // * strspn("",a) -> 0
1992 // * strspn(s,"") -> 0
1993 // * strcspn(s,a) -> const_int (if both args are constant)
1994 // * strcspn("",a) -> 0
1995 // * strcspn(s,"") -> strlen(a)
1998 // * strstr(x,x) -> x
1999 // * strstr(s1,s2) -> offset_of_s2_in(s1)
2000 // (if s1 and s2 are constant strings)
2003 // * tan(atan(x)) -> x
2005 // trunc, truncf, truncl:
2006 // * trunc(cnst) -> cnst'