1 //===- SimplifyLibCalls.cpp - Optimize specific well-known library calls --===//
3 // The LLVM Compiler Infrastructure
5 // This file was developed by Reid Spencer and is distributed under the
6 // University of Illinois Open Source License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file implements a module pass that applies a variety of small
11 // optimizations for calls to specific well-known function calls (e.g. runtime
12 // library functions). For example, a call to the function "exit(3)" that
13 // occurs within the main() function can be transformed into a simple "return 3"
14 // instruction. Any optimization that takes this form (replace call to library
15 // function with simpler code that provides the same result) belongs in this
18 //===----------------------------------------------------------------------===//
20 #define DEBUG_TYPE "simplify-libcalls"
21 #include "llvm/Constants.h"
22 #include "llvm/DerivedTypes.h"
23 #include "llvm/Instructions.h"
24 #include "llvm/Module.h"
25 #include "llvm/Pass.h"
26 #include "llvm/ADT/hash_map"
27 #include "llvm/ADT/Statistic.h"
28 #include "llvm/Config/config.h"
29 #include "llvm/Support/Debug.h"
30 #include "llvm/Target/TargetData.h"
31 #include "llvm/Transforms/IPO.h"
34 /// This statistic keeps track of the total number of library calls that have
35 /// been simplified regardless of which call it is.
36 STATISTIC(SimplifiedLibCalls, "Number of library calls simplified");
39 // Forward declarations
40 class LibCallOptimization;
41 class SimplifyLibCalls;
43 /// This list is populated by the constructor for LibCallOptimization class.
44 /// Therefore all subclasses are registered here at static initialization time
45 /// and this list is what the SimplifyLibCalls pass uses to apply the individual
46 /// optimizations to the call sites.
47 /// @brief The list of optimizations deriving from LibCallOptimization
48 static LibCallOptimization *OptList = 0;
50 /// This class is the abstract base class for the set of optimizations that
51 /// corresponds to one library call. The SimplifyLibCalls pass will call the
52 /// ValidateCalledFunction method to ask the optimization if a given Function
53 /// is the kind that the optimization can handle. If the subclass returns true,
54 /// then SImplifyLibCalls will also call the OptimizeCall method to perform,
55 /// or attempt to perform, the optimization(s) for the library call. Otherwise,
56 /// OptimizeCall won't be called. Subclasses are responsible for providing the
57 /// name of the library call (strlen, strcpy, etc.) to the LibCallOptimization
58 /// constructor. This is used to efficiently select which call instructions to
59 /// optimize. The criteria for a "lib call" is "anything with well known
60 /// semantics", typically a library function that is defined by an international
61 /// standard. Because the semantics are well known, the optimizations can
62 /// generally short-circuit actually calling the function if there's a simpler
63 /// way (e.g. strlen(X) can be reduced to a constant if X is a constant global).
64 /// @brief Base class for library call optimizations
65 class LibCallOptimization {
66 LibCallOptimization **Prev, *Next;
67 const char *FunctionName; ///< Name of the library call we optimize
69 Statistic occurrences; ///< debug statistic (-debug-only=simplify-libcalls)
72 /// The \p fname argument must be the name of the library function being
73 /// optimized by the subclass.
74 /// @brief Constructor that registers the optimization.
75 LibCallOptimization(const char *FName, const char *Description)
76 : FunctionName(FName) {
79 occurrences.construct("simplify-libcalls", Description);
81 // Register this optimizer in the list of optimizations.
85 if (Next) Next->Prev = &Next;
88 /// getNext - All libcall optimizations are chained together into a list,
89 /// return the next one in the list.
90 LibCallOptimization *getNext() { return Next; }
92 /// @brief Deregister from the optlist
93 virtual ~LibCallOptimization() {
95 if (Next) Next->Prev = Prev;
98 /// The implementation of this function in subclasses should determine if
99 /// \p F is suitable for the optimization. This method is called by
100 /// SimplifyLibCalls::runOnModule to short circuit visiting all the call
101 /// sites of such a function if that function is not suitable in the first
102 /// place. If the called function is suitabe, this method should return true;
103 /// false, otherwise. This function should also perform any lazy
104 /// initialization that the LibCallOptimization needs to do, if its to return
105 /// true. This avoids doing initialization until the optimizer is actually
106 /// going to be called upon to do some optimization.
107 /// @brief Determine if the function is suitable for optimization
108 virtual bool ValidateCalledFunction(
109 const Function* F, ///< The function that is the target of call sites
110 SimplifyLibCalls& SLC ///< The pass object invoking us
113 /// The implementations of this function in subclasses is the heart of the
114 /// SimplifyLibCalls algorithm. Sublcasses of this class implement
115 /// OptimizeCall to determine if (a) the conditions are right for optimizing
116 /// the call and (b) to perform the optimization. If an action is taken
117 /// against ci, the subclass is responsible for returning true and ensuring
118 /// that ci is erased from its parent.
119 /// @brief Optimize a call, if possible.
120 virtual bool OptimizeCall(
121 CallInst* ci, ///< The call instruction that should be optimized.
122 SimplifyLibCalls& SLC ///< The pass object invoking us
125 /// @brief Get the name of the library call being optimized
126 const char *getFunctionName() const { return FunctionName; }
128 /// @brief Called by SimplifyLibCalls to update the occurrences statistic.
131 DEBUG(++occurrences);
136 /// This class is an LLVM Pass that applies each of the LibCallOptimization
137 /// instances to all the call sites in a module, relatively efficiently. The
138 /// purpose of this pass is to provide optimizations for calls to well-known
139 /// functions with well-known semantics, such as those in the c library. The
140 /// class provides the basic infrastructure for handling runOnModule. Whenever
141 /// this pass finds a function call, it asks the appropriate optimizer to
142 /// validate the call (ValidateLibraryCall). If it is validated, then
143 /// the OptimizeCall method is also called.
144 /// @brief A ModulePass for optimizing well-known function calls.
145 class SimplifyLibCalls : public ModulePass {
147 /// We need some target data for accurate signature details that are
148 /// target dependent. So we require target data in our AnalysisUsage.
149 /// @brief Require TargetData from AnalysisUsage.
150 virtual void getAnalysisUsage(AnalysisUsage& Info) const {
151 // Ask that the TargetData analysis be performed before us so we can use
153 Info.addRequired<TargetData>();
156 /// For this pass, process all of the function calls in the module, calling
157 /// ValidateLibraryCall and OptimizeCall as appropriate.
158 /// @brief Run all the lib call optimizations on a Module.
159 virtual bool runOnModule(Module &M) {
163 hash_map<std::string, LibCallOptimization*> OptznMap;
164 for (LibCallOptimization *Optzn = OptList; Optzn; Optzn = Optzn->getNext())
165 OptznMap[Optzn->getFunctionName()] = Optzn;
167 // The call optimizations can be recursive. That is, the optimization might
168 // generate a call to another function which can also be optimized. This way
169 // we make the LibCallOptimization instances very specific to the case they
170 // handle. It also means we need to keep running over the function calls in
171 // the module until we don't get any more optimizations possible.
172 bool found_optimization = false;
174 found_optimization = false;
175 for (Module::iterator FI = M.begin(), FE = M.end(); FI != FE; ++FI) {
176 // All the "well-known" functions are external and have external linkage
177 // because they live in a runtime library somewhere and were (probably)
178 // not compiled by LLVM. So, we only act on external functions that
179 // have external or dllimport linkage and non-empty uses.
180 if (!FI->isDeclaration() ||
181 !(FI->hasExternalLinkage() || FI->hasDLLImportLinkage()) ||
185 // Get the optimization class that pertains to this function
186 hash_map<std::string, LibCallOptimization*>::iterator OMI =
187 OptznMap.find(FI->getName());
188 if (OMI == OptznMap.end()) continue;
190 LibCallOptimization *CO = OMI->second;
192 // Make sure the called function is suitable for the optimization
193 if (!CO->ValidateCalledFunction(FI, *this))
196 // Loop over each of the uses of the function
197 for (Value::use_iterator UI = FI->use_begin(), UE = FI->use_end();
199 // If the use of the function is a call instruction
200 if (CallInst* CI = dyn_cast<CallInst>(*UI++)) {
201 // Do the optimization on the LibCallOptimization.
202 if (CO->OptimizeCall(CI, *this)) {
203 ++SimplifiedLibCalls;
204 found_optimization = result = true;
210 } while (found_optimization);
215 /// @brief Return the *current* module we're working on.
216 Module* getModule() const { return M; }
218 /// @brief Return the *current* target data for the module we're working on.
219 TargetData* getTargetData() const { return TD; }
221 /// @brief Return the size_t type -- syntactic shortcut
222 const Type* getIntPtrType() const { return TD->getIntPtrType(); }
224 /// @brief Return a Function* for the putchar libcall
225 Constant *get_putchar() {
228 M->getOrInsertFunction("putchar", Type::Int32Ty, Type::Int32Ty, NULL);
232 /// @brief Return a Function* for the puts libcall
233 Constant *get_puts() {
235 puts_func = M->getOrInsertFunction("puts", Type::Int32Ty,
236 PointerType::get(Type::Int8Ty),
241 /// @brief Return a Function* for the fputc libcall
242 Constant *get_fputc(const Type* FILEptr_type) {
244 fputc_func = M->getOrInsertFunction("fputc", Type::Int32Ty, Type::Int32Ty,
249 /// @brief Return a Function* for the fputs libcall
250 Constant *get_fputs(const Type* FILEptr_type) {
252 fputs_func = M->getOrInsertFunction("fputs", Type::Int32Ty,
253 PointerType::get(Type::Int8Ty),
258 /// @brief Return a Function* for the fwrite libcall
259 Constant *get_fwrite(const Type* FILEptr_type) {
261 fwrite_func = M->getOrInsertFunction("fwrite", TD->getIntPtrType(),
262 PointerType::get(Type::Int8Ty),
269 /// @brief Return a Function* for the sqrt libcall
270 Constant *get_sqrt() {
272 sqrt_func = M->getOrInsertFunction("sqrt", Type::DoubleTy,
273 Type::DoubleTy, NULL);
277 /// @brief Return a Function* for the strcpy libcall
278 Constant *get_strcpy() {
280 strcpy_func = M->getOrInsertFunction("strcpy",
281 PointerType::get(Type::Int8Ty),
282 PointerType::get(Type::Int8Ty),
283 PointerType::get(Type::Int8Ty),
288 /// @brief Return a Function* for the strlen libcall
289 Constant *get_strlen() {
291 strlen_func = M->getOrInsertFunction("strlen", TD->getIntPtrType(),
292 PointerType::get(Type::Int8Ty),
297 /// @brief Return a Function* for the memchr libcall
298 Constant *get_memchr() {
300 memchr_func = M->getOrInsertFunction("memchr",
301 PointerType::get(Type::Int8Ty),
302 PointerType::get(Type::Int8Ty),
303 Type::Int32Ty, TD->getIntPtrType(),
308 /// @brief Return a Function* for the memcpy libcall
309 Constant *get_memcpy() {
311 const Type *SBP = PointerType::get(Type::Int8Ty);
312 const char *N = TD->getIntPtrType() == Type::Int32Ty ?
313 "llvm.memcpy.i32" : "llvm.memcpy.i64";
314 memcpy_func = M->getOrInsertFunction(N, Type::VoidTy, SBP, SBP,
315 TD->getIntPtrType(), Type::Int32Ty,
321 Constant *getUnaryFloatFunction(const char *Name, Constant *&Cache) {
323 Cache = M->getOrInsertFunction(Name, Type::FloatTy, Type::FloatTy, NULL);
327 Constant *get_floorf() { return getUnaryFloatFunction("floorf", floorf_func);}
328 Constant *get_ceilf() { return getUnaryFloatFunction( "ceilf", ceilf_func);}
329 Constant *get_roundf() { return getUnaryFloatFunction("roundf", roundf_func);}
330 Constant *get_rintf() { return getUnaryFloatFunction( "rintf", rintf_func);}
331 Constant *get_nearbyintf() { return getUnaryFloatFunction("nearbyintf",
334 /// @brief Reset our cached data for a new Module
335 void reset(Module& mod) {
337 TD = &getAnalysis<TargetData>();
356 /// Caches for function pointers.
357 Constant *putchar_func, *puts_func;
358 Constant *fputc_func, *fputs_func, *fwrite_func;
359 Constant *memcpy_func, *memchr_func;
361 Constant *strcpy_func, *strlen_func;
362 Constant *floorf_func, *ceilf_func, *roundf_func;
363 Constant *rintf_func, *nearbyintf_func;
364 Module *M; ///< Cached Module
365 TargetData *TD; ///< Cached TargetData
369 RegisterPass<SimplifyLibCalls>
370 X("simplify-libcalls", "Simplify well-known library calls");
372 } // anonymous namespace
374 // The only public symbol in this file which just instantiates the pass object
375 ModulePass *llvm::createSimplifyLibCallsPass() {
376 return new SimplifyLibCalls();
379 // Classes below here, in the anonymous namespace, are all subclasses of the
380 // LibCallOptimization class, each implementing all optimizations possible for a
381 // single well-known library call. Each has a static singleton instance that
382 // auto registers it into the "optlist" global above.
385 // Forward declare utility functions.
386 bool getConstantStringLength(Value* V, uint64_t& len, ConstantArray** A = 0 );
387 Value *CastToCStr(Value *V, Instruction &IP);
389 /// This LibCallOptimization will find instances of a call to "exit" that occurs
390 /// within the "main" function and change it to a simple "ret" instruction with
391 /// the same value passed to the exit function. When this is done, it splits the
392 /// basic block at the exit(3) call and deletes the call instruction.
393 /// @brief Replace calls to exit in main with a simple return
394 struct ExitInMainOptimization : public LibCallOptimization {
395 ExitInMainOptimization() : LibCallOptimization("exit",
396 "Number of 'exit' calls simplified") {}
398 // Make sure the called function looks like exit (int argument, int return
399 // type, external linkage, not varargs).
400 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
401 return F->arg_size() >= 1 && F->arg_begin()->getType()->isInteger();
404 virtual bool OptimizeCall(CallInst* ci, SimplifyLibCalls& SLC) {
405 // To be careful, we check that the call to exit is coming from "main", that
406 // main has external linkage, and the return type of main and the argument
407 // to exit have the same type.
408 Function *from = ci->getParent()->getParent();
409 if (from->hasExternalLinkage())
410 if (from->getReturnType() == ci->getOperand(1)->getType())
411 if (from->getName() == "main") {
412 // Okay, time to actually do the optimization. First, get the basic
413 // block of the call instruction
414 BasicBlock* bb = ci->getParent();
416 // Create a return instruction that we'll replace the call with.
417 // Note that the argument of the return is the argument of the call
419 new ReturnInst(ci->getOperand(1), ci);
421 // Split the block at the call instruction which places it in a new
423 bb->splitBasicBlock(ci);
425 // The block split caused a branch instruction to be inserted into
426 // the end of the original block, right after the return instruction
427 // that we put there. That's not a valid block, so delete the branch
429 bb->getInstList().pop_back();
431 // Now we can finally get rid of the call instruction which now lives
432 // in the new basic block.
433 ci->eraseFromParent();
435 // Optimization succeeded, return true.
438 // We didn't pass the criteria for this optimization so return false
441 } ExitInMainOptimizer;
443 /// This LibCallOptimization will simplify a call to the strcat library
444 /// function. The simplification is possible only if the string being
445 /// concatenated is a constant array or a constant expression that results in
446 /// a constant string. In this case we can replace it with strlen + llvm.memcpy
447 /// of the constant string. Both of these calls are further reduced, if possible
448 /// on subsequent passes.
449 /// @brief Simplify the strcat library function.
450 struct StrCatOptimization : public LibCallOptimization {
452 /// @brief Default constructor
453 StrCatOptimization() : LibCallOptimization("strcat",
454 "Number of 'strcat' calls simplified") {}
458 /// @brief Make sure that the "strcat" function has the right prototype
459 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC){
460 if (f->getReturnType() == PointerType::get(Type::Int8Ty))
461 if (f->arg_size() == 2)
463 Function::const_arg_iterator AI = f->arg_begin();
464 if (AI++->getType() == PointerType::get(Type::Int8Ty))
465 if (AI->getType() == PointerType::get(Type::Int8Ty))
467 // Indicate this is a suitable call type.
474 /// @brief Optimize the strcat library function
475 virtual bool OptimizeCall(CallInst* ci, SimplifyLibCalls& SLC) {
476 // Extract some information from the instruction
477 Value* dest = ci->getOperand(1);
478 Value* src = ci->getOperand(2);
480 // Extract the initializer (while making numerous checks) from the
481 // source operand of the call to strcat. If we get null back, one of
482 // a variety of checks in get_GVInitializer failed
484 if (!getConstantStringLength(src,len))
487 // Handle the simple, do-nothing case
489 ci->replaceAllUsesWith(dest);
490 ci->eraseFromParent();
494 // Increment the length because we actually want to memcpy the null
495 // terminator as well.
498 // We need to find the end of the destination string. That's where the
499 // memory is to be moved to. We just generate a call to strlen (further
500 // optimized in another pass). Note that the SLC.get_strlen() call
501 // caches the Function* for us.
502 CallInst* strlen_inst =
503 new CallInst(SLC.get_strlen(), dest, dest->getName()+".len",ci);
505 // Now that we have the destination's length, we must index into the
506 // destination's pointer to get the actual memcpy destination (end of
507 // the string .. we're concatenating).
508 GetElementPtrInst* gep =
509 new GetElementPtrInst(dest, strlen_inst, dest->getName()+".indexed", ci);
511 // We have enough information to now generate the memcpy call to
512 // do the concatenation for us.
513 std::vector<Value*> vals;
514 vals.push_back(gep); // destination
515 vals.push_back(ci->getOperand(2)); // source
516 vals.push_back(ConstantInt::get(SLC.getIntPtrType(),len)); // length
517 vals.push_back(ConstantInt::get(Type::Int32Ty,1)); // alignment
518 new CallInst(SLC.get_memcpy(), vals, "", ci);
520 // Finally, substitute the first operand of the strcat call for the
521 // strcat call itself since strcat returns its first operand; and,
522 // kill the strcat CallInst.
523 ci->replaceAllUsesWith(dest);
524 ci->eraseFromParent();
529 /// This LibCallOptimization will simplify a call to the strchr library
530 /// function. It optimizes out cases where the arguments are both constant
531 /// and the result can be determined statically.
532 /// @brief Simplify the strcmp library function.
533 struct StrChrOptimization : public LibCallOptimization {
535 StrChrOptimization() : LibCallOptimization("strchr",
536 "Number of 'strchr' calls simplified") {}
538 /// @brief Make sure that the "strchr" function has the right prototype
539 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC){
540 if (f->getReturnType() == PointerType::get(Type::Int8Ty) &&
546 /// @brief Perform the strchr optimizations
547 virtual bool OptimizeCall(CallInst *ci, SimplifyLibCalls &SLC) {
548 // If there aren't three operands, bail
549 if (ci->getNumOperands() != 3)
552 // Check that the first argument to strchr is a constant array of sbyte.
553 // If it is, get the length and data, otherwise return false.
555 ConstantArray* CA = 0;
556 if (!getConstantStringLength(ci->getOperand(1), len, &CA))
559 // Check that the second argument to strchr is a constant int. If it isn't
560 // a constant signed integer, we can try an alternate optimization
561 ConstantInt* CSI = dyn_cast<ConstantInt>(ci->getOperand(2));
563 // The second operand is not constant, or not signed. Just lower this to
564 // memchr since we know the length of the string since it is constant.
565 Constant *f = SLC.get_memchr();
566 std::vector<Value*> args;
567 args.push_back(ci->getOperand(1));
568 args.push_back(ci->getOperand(2));
569 args.push_back(ConstantInt::get(SLC.getIntPtrType(), len));
570 ci->replaceAllUsesWith(new CallInst(f, args, ci->getName(), ci));
571 ci->eraseFromParent();
575 // Get the character we're looking for
576 int64_t chr = CSI->getSExtValue();
578 // Compute the offset
580 bool char_found = false;
581 for (uint64_t i = 0; i < len; ++i) {
582 if (ConstantInt* CI = dyn_cast<ConstantInt>(CA->getOperand(i))) {
583 // Check for the null terminator
584 if (CI->isNullValue())
585 break; // we found end of string
586 else if (CI->getSExtValue() == chr) {
594 // strchr(s,c) -> offset_of_in(c,s)
595 // (if c is a constant integer and s is a constant string)
597 Value* Idx = ConstantInt::get(Type::Int64Ty,offset);
598 GetElementPtrInst* GEP = new GetElementPtrInst(ci->getOperand(1), Idx,
599 ci->getOperand(1)->getName()+".strchr",ci);
600 ci->replaceAllUsesWith(GEP);
602 ci->replaceAllUsesWith(
603 ConstantPointerNull::get(PointerType::get(Type::Int8Ty)));
605 ci->eraseFromParent();
610 /// This LibCallOptimization will simplify a call to the strcmp library
611 /// function. It optimizes out cases where one or both arguments are constant
612 /// and the result can be determined statically.
613 /// @brief Simplify the strcmp library function.
614 struct StrCmpOptimization : public LibCallOptimization {
616 StrCmpOptimization() : LibCallOptimization("strcmp",
617 "Number of 'strcmp' calls simplified") {}
619 /// @brief Make sure that the "strcmp" function has the right prototype
620 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
621 return F->getReturnType() == Type::Int32Ty && F->arg_size() == 2;
624 /// @brief Perform the strcmp optimization
625 virtual bool OptimizeCall(CallInst* ci, SimplifyLibCalls& SLC) {
626 // First, check to see if src and destination are the same. If they are,
627 // then the optimization is to replace the CallInst with a constant 0
628 // because the call is a no-op.
629 Value* s1 = ci->getOperand(1);
630 Value* s2 = ci->getOperand(2);
633 ci->replaceAllUsesWith(ConstantInt::get(Type::Int32Ty,0));
634 ci->eraseFromParent();
638 bool isstr_1 = false;
641 if (getConstantStringLength(s1,len_1,&A1)) {
644 // strcmp("",x) -> *x
646 new LoadInst(CastToCStr(s2,*ci), ci->getName()+".load",ci);
648 CastInst::create(Instruction::SExt, load, Type::Int32Ty,
649 ci->getName()+".int", ci);
650 ci->replaceAllUsesWith(cast);
651 ci->eraseFromParent();
656 bool isstr_2 = false;
659 if (getConstantStringLength(s2, len_2, &A2)) {
662 // strcmp(x,"") -> *x
664 new LoadInst(CastToCStr(s1,*ci),ci->getName()+".val",ci);
666 CastInst::create(Instruction::SExt, load, Type::Int32Ty,
667 ci->getName()+".int", ci);
668 ci->replaceAllUsesWith(cast);
669 ci->eraseFromParent();
674 if (isstr_1 && isstr_2) {
675 // strcmp(x,y) -> cnst (if both x and y are constant strings)
676 std::string str1 = A1->getAsString();
677 std::string str2 = A2->getAsString();
678 int result = strcmp(str1.c_str(), str2.c_str());
679 ci->replaceAllUsesWith(ConstantInt::get(Type::Int32Ty,result));
680 ci->eraseFromParent();
687 /// This LibCallOptimization will simplify a call to the strncmp library
688 /// function. It optimizes out cases where one or both arguments are constant
689 /// and the result can be determined statically.
690 /// @brief Simplify the strncmp library function.
691 struct StrNCmpOptimization : public LibCallOptimization {
693 StrNCmpOptimization() : LibCallOptimization("strncmp",
694 "Number of 'strncmp' calls simplified") {}
696 /// @brief Make sure that the "strncmp" function has the right prototype
697 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC){
698 if (f->getReturnType() == Type::Int32Ty && f->arg_size() == 3)
703 /// @brief Perform the strncpy optimization
704 virtual bool OptimizeCall(CallInst *ci, SimplifyLibCalls &SLC) {
705 // First, check to see if src and destination are the same. If they are,
706 // then the optimization is to replace the CallInst with a constant 0
707 // because the call is a no-op.
708 Value* s1 = ci->getOperand(1);
709 Value* s2 = ci->getOperand(2);
711 // strncmp(x,x,l) -> 0
712 ci->replaceAllUsesWith(ConstantInt::get(Type::Int32Ty,0));
713 ci->eraseFromParent();
717 // Check the length argument, if it is Constant zero then the strings are
719 uint64_t len_arg = 0;
720 bool len_arg_is_const = false;
721 if (ConstantInt* len_CI = dyn_cast<ConstantInt>(ci->getOperand(3))) {
722 len_arg_is_const = true;
723 len_arg = len_CI->getZExtValue();
725 // strncmp(x,y,0) -> 0
726 ci->replaceAllUsesWith(ConstantInt::get(Type::Int32Ty,0));
727 ci->eraseFromParent();
732 bool isstr_1 = false;
735 if (getConstantStringLength(s1, len_1, &A1)) {
738 // strncmp("",x) -> *x
739 LoadInst* load = new LoadInst(s1,ci->getName()+".load",ci);
741 CastInst::create(Instruction::SExt, load, Type::Int32Ty,
742 ci->getName()+".int", ci);
743 ci->replaceAllUsesWith(cast);
744 ci->eraseFromParent();
749 bool isstr_2 = false;
752 if (getConstantStringLength(s2,len_2,&A2)) {
755 // strncmp(x,"") -> *x
756 LoadInst* load = new LoadInst(s2,ci->getName()+".val",ci);
758 CastInst::create(Instruction::SExt, load, Type::Int32Ty,
759 ci->getName()+".int", ci);
760 ci->replaceAllUsesWith(cast);
761 ci->eraseFromParent();
766 if (isstr_1 && isstr_2 && len_arg_is_const) {
767 // strncmp(x,y,const) -> constant
768 std::string str1 = A1->getAsString();
769 std::string str2 = A2->getAsString();
770 int result = strncmp(str1.c_str(), str2.c_str(), len_arg);
771 ci->replaceAllUsesWith(ConstantInt::get(Type::Int32Ty,result));
772 ci->eraseFromParent();
779 /// This LibCallOptimization will simplify a call to the strcpy library
780 /// function. Two optimizations are possible:
781 /// (1) If src and dest are the same and not volatile, just return dest
782 /// (2) If the src is a constant then we can convert to llvm.memmove
783 /// @brief Simplify the strcpy library function.
784 struct StrCpyOptimization : public LibCallOptimization {
786 StrCpyOptimization() : LibCallOptimization("strcpy",
787 "Number of 'strcpy' calls simplified") {}
789 /// @brief Make sure that the "strcpy" function has the right prototype
790 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC){
791 if (f->getReturnType() == PointerType::get(Type::Int8Ty))
792 if (f->arg_size() == 2) {
793 Function::const_arg_iterator AI = f->arg_begin();
794 if (AI++->getType() == PointerType::get(Type::Int8Ty))
795 if (AI->getType() == PointerType::get(Type::Int8Ty)) {
796 // Indicate this is a suitable call type.
803 /// @brief Perform the strcpy optimization
804 virtual bool OptimizeCall(CallInst* ci, SimplifyLibCalls& SLC) {
805 // First, check to see if src and destination are the same. If they are,
806 // then the optimization is to replace the CallInst with the destination
807 // because the call is a no-op. Note that this corresponds to the
808 // degenerate strcpy(X,X) case which should have "undefined" results
809 // according to the C specification. However, it occurs sometimes and
810 // we optimize it as a no-op.
811 Value* dest = ci->getOperand(1);
812 Value* src = ci->getOperand(2);
814 ci->replaceAllUsesWith(dest);
815 ci->eraseFromParent();
819 // Get the length of the constant string referenced by the second operand,
820 // the "src" parameter. Fail the optimization if we can't get the length
821 // (note that getConstantStringLength does lots of checks to make sure this
824 if (!getConstantStringLength(ci->getOperand(2),len))
827 // If the constant string's length is zero we can optimize this by just
828 // doing a store of 0 at the first byte of the destination
830 new StoreInst(ConstantInt::get(Type::Int8Ty,0),ci->getOperand(1),ci);
831 ci->replaceAllUsesWith(dest);
832 ci->eraseFromParent();
836 // Increment the length because we actually want to memcpy the null
837 // terminator as well.
840 // We have enough information to now generate the memcpy call to
841 // do the concatenation for us.
842 std::vector<Value*> vals;
843 vals.push_back(dest); // destination
844 vals.push_back(src); // source
845 vals.push_back(ConstantInt::get(SLC.getIntPtrType(),len)); // length
846 vals.push_back(ConstantInt::get(Type::Int32Ty,1)); // alignment
847 new CallInst(SLC.get_memcpy(), vals, "", ci);
849 // Finally, substitute the first operand of the strcat call for the
850 // strcat call itself since strcat returns its first operand; and,
851 // kill the strcat CallInst.
852 ci->replaceAllUsesWith(dest);
853 ci->eraseFromParent();
858 /// This LibCallOptimization will simplify a call to the strlen library
859 /// function by replacing it with a constant value if the string provided to
860 /// it is a constant array.
861 /// @brief Simplify the strlen library function.
862 struct StrLenOptimization : public LibCallOptimization {
863 StrLenOptimization() : LibCallOptimization("strlen",
864 "Number of 'strlen' calls simplified") {}
866 /// @brief Make sure that the "strlen" function has the right prototype
867 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC)
869 if (f->getReturnType() == SLC.getTargetData()->getIntPtrType())
870 if (f->arg_size() == 1)
871 if (Function::const_arg_iterator AI = f->arg_begin())
872 if (AI->getType() == PointerType::get(Type::Int8Ty))
877 /// @brief Perform the strlen optimization
878 virtual bool OptimizeCall(CallInst* ci, SimplifyLibCalls& SLC)
880 // Make sure we're dealing with an sbyte* here.
881 Value* str = ci->getOperand(1);
882 if (str->getType() != PointerType::get(Type::Int8Ty))
885 // Does the call to strlen have exactly one use?
887 // Is that single use a icmp operator?
888 if (ICmpInst* bop = dyn_cast<ICmpInst>(ci->use_back()))
889 // Is it compared against a constant integer?
890 if (ConstantInt* CI = dyn_cast<ConstantInt>(bop->getOperand(1)))
892 // Get the value the strlen result is compared to
893 uint64_t val = CI->getZExtValue();
895 // If its compared against length 0 with == or !=
897 (bop->getPredicate() == ICmpInst::ICMP_EQ ||
898 bop->getPredicate() == ICmpInst::ICMP_NE))
900 // strlen(x) != 0 -> *x != 0
901 // strlen(x) == 0 -> *x == 0
902 LoadInst* load = new LoadInst(str,str->getName()+".first",ci);
903 ICmpInst* rbop = new ICmpInst(bop->getPredicate(), load,
904 ConstantInt::get(Type::Int8Ty,0),
905 bop->getName()+".strlen", ci);
906 bop->replaceAllUsesWith(rbop);
907 bop->eraseFromParent();
908 ci->eraseFromParent();
913 // Get the length of the constant string operand
915 if (!getConstantStringLength(ci->getOperand(1),len))
918 // strlen("xyz") -> 3 (for example)
919 const Type *Ty = SLC.getTargetData()->getIntPtrType();
920 ci->replaceAllUsesWith(ConstantInt::get(Ty, len));
922 ci->eraseFromParent();
927 /// IsOnlyUsedInEqualsComparison - Return true if it only matters that the value
928 /// is equal or not-equal to zero.
929 static bool IsOnlyUsedInEqualsZeroComparison(Instruction *I) {
930 for (Value::use_iterator UI = I->use_begin(), E = I->use_end();
932 Instruction *User = cast<Instruction>(*UI);
933 if (ICmpInst *IC = dyn_cast<ICmpInst>(User)) {
934 if ((IC->getPredicate() == ICmpInst::ICMP_NE ||
935 IC->getPredicate() == ICmpInst::ICMP_EQ) &&
936 isa<Constant>(IC->getOperand(1)) &&
937 cast<Constant>(IC->getOperand(1))->isNullValue())
939 } else if (CastInst *CI = dyn_cast<CastInst>(User))
940 if (CI->getType() == Type::Int1Ty)
942 // Unknown instruction.
948 /// This memcmpOptimization will simplify a call to the memcmp library
950 struct memcmpOptimization : public LibCallOptimization {
951 /// @brief Default Constructor
953 : LibCallOptimization("memcmp", "Number of 'memcmp' calls simplified") {}
955 /// @brief Make sure that the "memcmp" function has the right prototype
956 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &TD) {
957 Function::const_arg_iterator AI = F->arg_begin();
958 if (F->arg_size() != 3 || !isa<PointerType>(AI->getType())) return false;
959 if (!isa<PointerType>((++AI)->getType())) return false;
960 if (!(++AI)->getType()->isInteger()) return false;
961 if (!F->getReturnType()->isInteger()) return false;
965 /// Because of alignment and instruction information that we don't have, we
966 /// leave the bulk of this to the code generators.
968 /// Note that we could do much more if we could force alignment on otherwise
969 /// small aligned allocas, or if we could indicate that loads have a small
971 virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &TD) {
972 Value *LHS = CI->getOperand(1), *RHS = CI->getOperand(2);
974 // If the two operands are the same, return zero.
976 // memcmp(s,s,x) -> 0
977 CI->replaceAllUsesWith(Constant::getNullValue(CI->getType()));
978 CI->eraseFromParent();
982 // Make sure we have a constant length.
983 ConstantInt *LenC = dyn_cast<ConstantInt>(CI->getOperand(3));
984 if (!LenC) return false;
985 uint64_t Len = LenC->getZExtValue();
987 // If the length is zero, this returns 0.
990 // memcmp(s1,s2,0) -> 0
991 CI->replaceAllUsesWith(Constant::getNullValue(CI->getType()));
992 CI->eraseFromParent();
995 // memcmp(S1,S2,1) -> *(ubyte*)S1 - *(ubyte*)S2
996 const Type *UCharPtr = PointerType::get(Type::Int8Ty);
997 CastInst *Op1Cast = CastInst::create(
998 Instruction::BitCast, LHS, UCharPtr, LHS->getName(), CI);
999 CastInst *Op2Cast = CastInst::create(
1000 Instruction::BitCast, RHS, UCharPtr, RHS->getName(), CI);
1001 Value *S1V = new LoadInst(Op1Cast, LHS->getName()+".val", CI);
1002 Value *S2V = new LoadInst(Op2Cast, RHS->getName()+".val", CI);
1003 Value *RV = BinaryOperator::createSub(S1V, S2V, CI->getName()+".diff",CI);
1004 if (RV->getType() != CI->getType())
1005 RV = CastInst::createIntegerCast(RV, CI->getType(), false,
1007 CI->replaceAllUsesWith(RV);
1008 CI->eraseFromParent();
1012 if (IsOnlyUsedInEqualsZeroComparison(CI)) {
1013 // TODO: IF both are aligned, use a short load/compare.
1015 // memcmp(S1,S2,2) -> S1[0]-S2[0] | S1[1]-S2[1] iff only ==/!= 0 matters
1016 const Type *UCharPtr = PointerType::get(Type::Int8Ty);
1017 CastInst *Op1Cast = CastInst::create(
1018 Instruction::BitCast, LHS, UCharPtr, LHS->getName(), CI);
1019 CastInst *Op2Cast = CastInst::create(
1020 Instruction::BitCast, RHS, UCharPtr, RHS->getName(), CI);
1021 Value *S1V1 = new LoadInst(Op1Cast, LHS->getName()+".val1", CI);
1022 Value *S2V1 = new LoadInst(Op2Cast, RHS->getName()+".val1", CI);
1023 Value *D1 = BinaryOperator::createSub(S1V1, S2V1,
1024 CI->getName()+".d1", CI);
1025 Constant *One = ConstantInt::get(Type::Int32Ty, 1);
1026 Value *G1 = new GetElementPtrInst(Op1Cast, One, "next1v", CI);
1027 Value *G2 = new GetElementPtrInst(Op2Cast, One, "next2v", CI);
1028 Value *S1V2 = new LoadInst(G1, LHS->getName()+".val2", CI);
1029 Value *S2V2 = new LoadInst(G2, RHS->getName()+".val2", CI);
1030 Value *D2 = BinaryOperator::createSub(S1V2, S2V2,
1031 CI->getName()+".d1", CI);
1032 Value *Or = BinaryOperator::createOr(D1, D2, CI->getName()+".res", CI);
1033 if (Or->getType() != CI->getType())
1034 Or = CastInst::createIntegerCast(Or, CI->getType(), false /*ZExt*/,
1036 CI->replaceAllUsesWith(Or);
1037 CI->eraseFromParent();
1050 /// This LibCallOptimization will simplify a call to the memcpy library
1051 /// function by expanding it out to a single store of size 0, 1, 2, 4, or 8
1052 /// bytes depending on the length of the string and the alignment. Additional
1053 /// optimizations are possible in code generation (sequence of immediate store)
1054 /// @brief Simplify the memcpy library function.
1055 struct LLVMMemCpyMoveOptzn : public LibCallOptimization {
1056 LLVMMemCpyMoveOptzn(const char* fname, const char* desc)
1057 : LibCallOptimization(fname, desc) {}
1059 /// @brief Make sure that the "memcpy" function has the right prototype
1060 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& TD) {
1061 // Just make sure this has 4 arguments per LLVM spec.
1062 return (f->arg_size() == 4);
1065 /// Because of alignment and instruction information that we don't have, we
1066 /// leave the bulk of this to the code generators. The optimization here just
1067 /// deals with a few degenerate cases where the length of the string and the
1068 /// alignment match the sizes of our intrinsic types so we can do a load and
1069 /// store instead of the memcpy call.
1070 /// @brief Perform the memcpy optimization.
1071 virtual bool OptimizeCall(CallInst* ci, SimplifyLibCalls& TD) {
1072 // Make sure we have constant int values to work with
1073 ConstantInt* LEN = dyn_cast<ConstantInt>(ci->getOperand(3));
1076 ConstantInt* ALIGN = dyn_cast<ConstantInt>(ci->getOperand(4));
1080 // If the length is larger than the alignment, we can't optimize
1081 uint64_t len = LEN->getZExtValue();
1082 uint64_t alignment = ALIGN->getZExtValue();
1084 alignment = 1; // Alignment 0 is identity for alignment 1
1085 if (len > alignment)
1088 // Get the type we will cast to, based on size of the string
1089 Value* dest = ci->getOperand(1);
1090 Value* src = ci->getOperand(2);
1091 const Type* castType = 0;
1095 // memcpy(d,s,0,a) -> noop
1096 ci->eraseFromParent();
1098 case 1: castType = Type::Int8Ty; break;
1099 case 2: castType = Type::Int16Ty; break;
1100 case 4: castType = Type::Int32Ty; break;
1101 case 8: castType = Type::Int64Ty; break;
1106 // Cast source and dest to the right sized primitive and then load/store
1107 CastInst* SrcCast = CastInst::create(Instruction::BitCast,
1108 src, PointerType::get(castType), src->getName()+".cast", ci);
1109 CastInst* DestCast = CastInst::create(Instruction::BitCast,
1110 dest, PointerType::get(castType),dest->getName()+".cast", ci);
1111 LoadInst* LI = new LoadInst(SrcCast,SrcCast->getName()+".val",ci);
1112 new StoreInst(LI, DestCast, ci);
1113 ci->eraseFromParent();
1118 /// This LibCallOptimization will simplify a call to the memcpy/memmove library
1120 LLVMMemCpyMoveOptzn LLVMMemCpyOptimizer32("llvm.memcpy.i32",
1121 "Number of 'llvm.memcpy' calls simplified");
1122 LLVMMemCpyMoveOptzn LLVMMemCpyOptimizer64("llvm.memcpy.i64",
1123 "Number of 'llvm.memcpy' calls simplified");
1124 LLVMMemCpyMoveOptzn LLVMMemMoveOptimizer32("llvm.memmove.i32",
1125 "Number of 'llvm.memmove' calls simplified");
1126 LLVMMemCpyMoveOptzn LLVMMemMoveOptimizer64("llvm.memmove.i64",
1127 "Number of 'llvm.memmove' calls simplified");
1129 /// This LibCallOptimization will simplify a call to the memset library
1130 /// function by expanding it out to a single store of size 0, 1, 2, 4, or 8
1131 /// bytes depending on the length argument.
1132 struct LLVMMemSetOptimization : public LibCallOptimization {
1133 /// @brief Default Constructor
1134 LLVMMemSetOptimization(const char *Name) : LibCallOptimization(Name,
1135 "Number of 'llvm.memset' calls simplified") {}
1137 /// @brief Make sure that the "memset" function has the right prototype
1138 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &TD) {
1139 // Just make sure this has 3 arguments per LLVM spec.
1140 return F->arg_size() == 4;
1143 /// Because of alignment and instruction information that we don't have, we
1144 /// leave the bulk of this to the code generators. The optimization here just
1145 /// deals with a few degenerate cases where the length parameter is constant
1146 /// and the alignment matches the sizes of our intrinsic types so we can do
1147 /// store instead of the memcpy call. Other calls are transformed into the
1148 /// llvm.memset intrinsic.
1149 /// @brief Perform the memset optimization.
1150 virtual bool OptimizeCall(CallInst *ci, SimplifyLibCalls &TD) {
1151 // Make sure we have constant int values to work with
1152 ConstantInt* LEN = dyn_cast<ConstantInt>(ci->getOperand(3));
1155 ConstantInt* ALIGN = dyn_cast<ConstantInt>(ci->getOperand(4));
1159 // Extract the length and alignment
1160 uint64_t len = LEN->getZExtValue();
1161 uint64_t alignment = ALIGN->getZExtValue();
1163 // Alignment 0 is identity for alignment 1
1167 // If the length is zero, this is a no-op
1169 // memset(d,c,0,a) -> noop
1170 ci->eraseFromParent();
1174 // If the length is larger than the alignment, we can't optimize
1175 if (len > alignment)
1178 // Make sure we have a constant ubyte to work with so we can extract
1179 // the value to be filled.
1180 ConstantInt* FILL = dyn_cast<ConstantInt>(ci->getOperand(2));
1183 if (FILL->getType() != Type::Int8Ty)
1186 // memset(s,c,n) -> store s, c (for n=1,2,4,8)
1188 // Extract the fill character
1189 uint64_t fill_char = FILL->getZExtValue();
1190 uint64_t fill_value = fill_char;
1192 // Get the type we will cast to, based on size of memory area to fill, and
1193 // and the value we will store there.
1194 Value* dest = ci->getOperand(1);
1195 const Type* castType = 0;
1198 castType = Type::Int8Ty;
1201 castType = Type::Int16Ty;
1202 fill_value |= fill_char << 8;
1205 castType = Type::Int32Ty;
1206 fill_value |= fill_char << 8 | fill_char << 16 | fill_char << 24;
1209 castType = Type::Int64Ty;
1210 fill_value |= fill_char << 8 | fill_char << 16 | fill_char << 24;
1211 fill_value |= fill_char << 32 | fill_char << 40 | fill_char << 48;
1212 fill_value |= fill_char << 56;
1218 // Cast dest to the right sized primitive and then load/store
1219 CastInst* DestCast = new BitCastInst(dest, PointerType::get(castType),
1220 dest->getName()+".cast", ci);
1221 new StoreInst(ConstantInt::get(castType,fill_value),DestCast, ci);
1222 ci->eraseFromParent();
1227 LLVMMemSetOptimization MemSet32Optimizer("llvm.memset.i32");
1228 LLVMMemSetOptimization MemSet64Optimizer("llvm.memset.i64");
1231 /// This LibCallOptimization will simplify calls to the "pow" library
1232 /// function. It looks for cases where the result of pow is well known and
1233 /// substitutes the appropriate value.
1234 /// @brief Simplify the pow library function.
1235 struct PowOptimization : public LibCallOptimization {
1237 /// @brief Default Constructor
1238 PowOptimization() : LibCallOptimization("pow",
1239 "Number of 'pow' calls simplified") {}
1241 /// @brief Make sure that the "pow" function has the right prototype
1242 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC){
1243 // Just make sure this has 2 arguments
1244 return (f->arg_size() == 2);
1247 /// @brief Perform the pow optimization.
1248 virtual bool OptimizeCall(CallInst *ci, SimplifyLibCalls &SLC) {
1249 const Type *Ty = cast<Function>(ci->getOperand(0))->getReturnType();
1250 Value* base = ci->getOperand(1);
1251 Value* expn = ci->getOperand(2);
1252 if (ConstantFP *Op1 = dyn_cast<ConstantFP>(base)) {
1253 double Op1V = Op1->getValue();
1255 // pow(1.0,x) -> 1.0
1256 ci->replaceAllUsesWith(ConstantFP::get(Ty,1.0));
1257 ci->eraseFromParent();
1260 } else if (ConstantFP* Op2 = dyn_cast<ConstantFP>(expn)) {
1261 double Op2V = Op2->getValue();
1263 // pow(x,0.0) -> 1.0
1264 ci->replaceAllUsesWith(ConstantFP::get(Ty,1.0));
1265 ci->eraseFromParent();
1267 } else if (Op2V == 0.5) {
1268 // pow(x,0.5) -> sqrt(x)
1269 CallInst* sqrt_inst = new CallInst(SLC.get_sqrt(), base,
1270 ci->getName()+".pow",ci);
1271 ci->replaceAllUsesWith(sqrt_inst);
1272 ci->eraseFromParent();
1274 } else if (Op2V == 1.0) {
1276 ci->replaceAllUsesWith(base);
1277 ci->eraseFromParent();
1279 } else if (Op2V == -1.0) {
1280 // pow(x,-1.0) -> 1.0/x
1281 BinaryOperator* div_inst= BinaryOperator::createFDiv(
1282 ConstantFP::get(Ty,1.0), base, ci->getName()+".pow", ci);
1283 ci->replaceAllUsesWith(div_inst);
1284 ci->eraseFromParent();
1288 return false; // opt failed
1292 /// This LibCallOptimization will simplify calls to the "printf" library
1293 /// function. It looks for cases where the result of printf is not used and the
1294 /// operation can be reduced to something simpler.
1295 /// @brief Simplify the printf library function.
1296 struct PrintfOptimization : public LibCallOptimization {
1298 /// @brief Default Constructor
1299 PrintfOptimization() : LibCallOptimization("printf",
1300 "Number of 'printf' calls simplified") {}
1302 /// @brief Make sure that the "printf" function has the right prototype
1303 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC){
1304 // Just make sure this has at least 1 arguments
1305 return (f->arg_size() >= 1);
1308 /// @brief Perform the printf optimization.
1309 virtual bool OptimizeCall(CallInst* ci, SimplifyLibCalls& SLC) {
1310 // If the call has more than 2 operands, we can't optimize it
1311 if (ci->getNumOperands() > 3 || ci->getNumOperands() <= 2)
1314 // If the result of the printf call is used, none of these optimizations
1316 if (!ci->use_empty())
1319 // All the optimizations depend on the length of the first argument and the
1320 // fact that it is a constant string array. Check that now
1322 ConstantArray* CA = 0;
1323 if (!getConstantStringLength(ci->getOperand(1), len, &CA))
1326 if (len != 2 && len != 3)
1329 // The first character has to be a %
1330 if (ConstantInt* CI = dyn_cast<ConstantInt>(CA->getOperand(0)))
1331 if (CI->getZExtValue() != '%')
1334 // Get the second character and switch on its value
1335 ConstantInt* CI = dyn_cast<ConstantInt>(CA->getOperand(1));
1336 switch (CI->getZExtValue()) {
1340 dyn_cast<ConstantInt>(CA->getOperand(2))->getZExtValue() != '\n')
1343 // printf("%s\n",str) -> puts(str)
1344 std::vector<Value*> args;
1345 new CallInst(SLC.get_puts(), CastToCStr(ci->getOperand(2), *ci),
1347 ci->replaceAllUsesWith(ConstantInt::get(Type::Int32Ty, len));
1352 // printf("%c",c) -> putchar(c)
1356 CastInst *Char = CastInst::createSExtOrBitCast(
1357 ci->getOperand(2), Type::Int32Ty, CI->getName()+".int", ci);
1358 new CallInst(SLC.get_putchar(), Char, "", ci);
1359 ci->replaceAllUsesWith(ConstantInt::get(Type::Int32Ty, 1));
1365 ci->eraseFromParent();
1370 /// This LibCallOptimization will simplify calls to the "fprintf" library
1371 /// function. It looks for cases where the result of fprintf is not used and the
1372 /// operation can be reduced to something simpler.
1373 /// @brief Simplify the fprintf library function.
1374 struct FPrintFOptimization : public LibCallOptimization {
1376 /// @brief Default Constructor
1377 FPrintFOptimization() : LibCallOptimization("fprintf",
1378 "Number of 'fprintf' calls simplified") {}
1380 /// @brief Make sure that the "fprintf" function has the right prototype
1381 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC){
1382 // Just make sure this has at least 2 arguments
1383 return (f->arg_size() >= 2);
1386 /// @brief Perform the fprintf optimization.
1387 virtual bool OptimizeCall(CallInst* ci, SimplifyLibCalls& SLC) {
1388 // If the call has more than 3 operands, we can't optimize it
1389 if (ci->getNumOperands() > 4 || ci->getNumOperands() <= 2)
1392 // If the result of the fprintf call is used, none of these optimizations
1394 if (!ci->use_empty())
1397 // All the optimizations depend on the length of the second argument and the
1398 // fact that it is a constant string array. Check that now
1400 ConstantArray* CA = 0;
1401 if (!getConstantStringLength(ci->getOperand(2), len, &CA))
1404 if (ci->getNumOperands() == 3) {
1405 // Make sure there's no % in the constant array
1406 for (unsigned i = 0; i < len; ++i) {
1407 if (ConstantInt* CI = dyn_cast<ConstantInt>(CA->getOperand(i))) {
1408 // Check for the null terminator
1409 if (CI->getZExtValue() == '%')
1410 return false; // we found end of string
1416 // fprintf(file,fmt) -> fwrite(fmt,strlen(fmt),file)
1417 const Type* FILEptr_type = ci->getOperand(1)->getType();
1419 // Make sure that the fprintf() and fwrite() functions both take the
1420 // same type of char pointer.
1421 if (ci->getOperand(2)->getType() != PointerType::get(Type::Int8Ty))
1424 std::vector<Value*> args;
1425 args.push_back(ci->getOperand(2));
1426 args.push_back(ConstantInt::get(SLC.getIntPtrType(),len));
1427 args.push_back(ConstantInt::get(SLC.getIntPtrType(),1));
1428 args.push_back(ci->getOperand(1));
1429 new CallInst(SLC.get_fwrite(FILEptr_type), args, ci->getName(), ci);
1430 ci->replaceAllUsesWith(ConstantInt::get(Type::Int32Ty,len));
1431 ci->eraseFromParent();
1435 // The remaining optimizations require the format string to be length 2
1440 // The first character has to be a %
1441 if (ConstantInt* CI = dyn_cast<ConstantInt>(CA->getOperand(0)))
1442 if (CI->getZExtValue() != '%')
1445 // Get the second character and switch on its value
1446 ConstantInt* CI = dyn_cast<ConstantInt>(CA->getOperand(1));
1447 switch (CI->getZExtValue()) {
1451 ConstantArray* CA = 0;
1452 if (getConstantStringLength(ci->getOperand(3), len, &CA)) {
1453 // fprintf(file,"%s",str) -> fwrite(str,strlen(str),1,file)
1454 const Type* FILEptr_type = ci->getOperand(1)->getType();
1455 std::vector<Value*> args;
1456 args.push_back(CastToCStr(ci->getOperand(3), *ci));
1457 args.push_back(ConstantInt::get(SLC.getIntPtrType(), len));
1458 args.push_back(ConstantInt::get(SLC.getIntPtrType(), 1));
1459 args.push_back(ci->getOperand(1));
1460 new CallInst(SLC.get_fwrite(FILEptr_type), args, ci->getName(), ci);
1461 ci->replaceAllUsesWith(ConstantInt::get(Type::Int32Ty, len));
1463 // fprintf(file,"%s",str) -> fputs(str,file)
1464 const Type* FILEptr_type = ci->getOperand(1)->getType();
1465 new CallInst(SLC.get_fputs(FILEptr_type),
1466 CastToCStr(ci->getOperand(3), *ci),
1467 ci->getOperand(1), ci->getName(),ci);
1468 ci->replaceAllUsesWith(ConstantInt::get(Type::Int32Ty,len));
1474 // fprintf(file,"%c",c) -> fputc(c,file)
1475 const Type* FILEptr_type = ci->getOperand(1)->getType();
1476 CastInst* cast = CastInst::createSExtOrBitCast(
1477 ci->getOperand(3), Type::Int32Ty, CI->getName()+".int", ci);
1478 new CallInst(SLC.get_fputc(FILEptr_type), cast,ci->getOperand(1),"",ci);
1479 ci->replaceAllUsesWith(ConstantInt::get(Type::Int32Ty,1));
1485 ci->eraseFromParent();
1490 /// This LibCallOptimization will simplify calls to the "sprintf" library
1491 /// function. It looks for cases where the result of sprintf is not used and the
1492 /// operation can be reduced to something simpler.
1493 /// @brief Simplify the sprintf library function.
1494 struct SPrintFOptimization : public LibCallOptimization {
1496 /// @brief Default Constructor
1497 SPrintFOptimization() : LibCallOptimization("sprintf",
1498 "Number of 'sprintf' calls simplified") {}
1500 /// @brief Make sure that the "fprintf" function has the right prototype
1501 virtual bool ValidateCalledFunction(const Function *f, SimplifyLibCalls &SLC){
1502 // Just make sure this has at least 2 arguments
1503 return (f->getReturnType() == Type::Int32Ty && f->arg_size() >= 2);
1506 /// @brief Perform the sprintf optimization.
1507 virtual bool OptimizeCall(CallInst *ci, SimplifyLibCalls &SLC) {
1508 // If the call has more than 3 operands, we can't optimize it
1509 if (ci->getNumOperands() > 4 || ci->getNumOperands() < 3)
1512 // All the optimizations depend on the length of the second argument and the
1513 // fact that it is a constant string array. Check that now
1515 ConstantArray* CA = 0;
1516 if (!getConstantStringLength(ci->getOperand(2), len, &CA))
1519 if (ci->getNumOperands() == 3) {
1521 // If the length is 0, we just need to store a null byte
1522 new StoreInst(ConstantInt::get(Type::Int8Ty,0),ci->getOperand(1),ci);
1523 ci->replaceAllUsesWith(ConstantInt::get(Type::Int32Ty,0));
1524 ci->eraseFromParent();
1528 // Make sure there's no % in the constant array
1529 for (unsigned i = 0; i < len; ++i) {
1530 if (ConstantInt* CI = dyn_cast<ConstantInt>(CA->getOperand(i))) {
1531 // Check for the null terminator
1532 if (CI->getZExtValue() == '%')
1533 return false; // we found a %, can't optimize
1535 return false; // initializer is not constant int, can't optimize
1539 // Increment length because we want to copy the null byte too
1542 // sprintf(str,fmt) -> llvm.memcpy(str,fmt,strlen(fmt),1)
1543 std::vector<Value*> args;
1544 args.push_back(ci->getOperand(1));
1545 args.push_back(ci->getOperand(2));
1546 args.push_back(ConstantInt::get(SLC.getIntPtrType(),len));
1547 args.push_back(ConstantInt::get(Type::Int32Ty,1));
1548 new CallInst(SLC.get_memcpy(), args, "", ci);
1549 ci->replaceAllUsesWith(ConstantInt::get(Type::Int32Ty,len));
1550 ci->eraseFromParent();
1554 // The remaining optimizations require the format string to be length 2
1559 // The first character has to be a %
1560 if (ConstantInt* CI = dyn_cast<ConstantInt>(CA->getOperand(0)))
1561 if (CI->getZExtValue() != '%')
1564 // Get the second character and switch on its value
1565 ConstantInt* CI = dyn_cast<ConstantInt>(CA->getOperand(1));
1566 switch (CI->getZExtValue()) {
1568 // sprintf(dest,"%s",str) -> llvm.memcpy(dest, str, strlen(str)+1, 1)
1569 Value *Len = new CallInst(SLC.get_strlen(),
1570 CastToCStr(ci->getOperand(3), *ci),
1571 ci->getOperand(3)->getName()+".len", ci);
1572 Value *Len1 = BinaryOperator::createAdd(Len,
1573 ConstantInt::get(Len->getType(), 1),
1574 Len->getName()+"1", ci);
1575 if (Len1->getType() != SLC.getIntPtrType())
1576 Len1 = CastInst::createIntegerCast(Len1, SLC.getIntPtrType(), false,
1577 Len1->getName(), ci);
1578 std::vector<Value*> args;
1579 args.push_back(CastToCStr(ci->getOperand(1), *ci));
1580 args.push_back(CastToCStr(ci->getOperand(3), *ci));
1581 args.push_back(Len1);
1582 args.push_back(ConstantInt::get(Type::Int32Ty,1));
1583 new CallInst(SLC.get_memcpy(), args, "", ci);
1585 // The strlen result is the unincremented number of bytes in the string.
1586 if (!ci->use_empty()) {
1587 if (Len->getType() != ci->getType())
1588 Len = CastInst::createIntegerCast(Len, ci->getType(), false,
1589 Len->getName(), ci);
1590 ci->replaceAllUsesWith(Len);
1592 ci->eraseFromParent();
1596 // sprintf(dest,"%c",chr) -> store chr, dest
1597 CastInst* cast = CastInst::createTruncOrBitCast(
1598 ci->getOperand(3), Type::Int8Ty, "char", ci);
1599 new StoreInst(cast, ci->getOperand(1), ci);
1600 GetElementPtrInst* gep = new GetElementPtrInst(ci->getOperand(1),
1601 ConstantInt::get(Type::Int32Ty,1),ci->getOperand(1)->getName()+".end",
1603 new StoreInst(ConstantInt::get(Type::Int8Ty,0),gep,ci);
1604 ci->replaceAllUsesWith(ConstantInt::get(Type::Int32Ty,1));
1605 ci->eraseFromParent();
1613 /// This LibCallOptimization will simplify calls to the "fputs" library
1614 /// function. It looks for cases where the result of fputs is not used and the
1615 /// operation can be reduced to something simpler.
1616 /// @brief Simplify the puts library function.
1617 struct PutsOptimization : public LibCallOptimization {
1619 /// @brief Default Constructor
1620 PutsOptimization() : LibCallOptimization("fputs",
1621 "Number of 'fputs' calls simplified") {}
1623 /// @brief Make sure that the "fputs" function has the right prototype
1624 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
1625 // Just make sure this has 2 arguments
1626 return F->arg_size() == 2;
1629 /// @brief Perform the fputs optimization.
1630 virtual bool OptimizeCall(CallInst* ci, SimplifyLibCalls& SLC) {
1631 // If the result is used, none of these optimizations work
1632 if (!ci->use_empty())
1635 // All the optimizations depend on the length of the first argument and the
1636 // fact that it is a constant string array. Check that now
1638 if (!getConstantStringLength(ci->getOperand(1), len))
1643 // fputs("",F) -> noop
1647 // fputs(s,F) -> fputc(s[0],F) (if s is constant and strlen(s) == 1)
1648 const Type* FILEptr_type = ci->getOperand(2)->getType();
1649 LoadInst* loadi = new LoadInst(ci->getOperand(1),
1650 ci->getOperand(1)->getName()+".byte",ci);
1651 CastInst* casti = new SExtInst(loadi, Type::Int32Ty,
1652 loadi->getName()+".int", ci);
1653 new CallInst(SLC.get_fputc(FILEptr_type), casti,
1654 ci->getOperand(2), "", ci);
1659 // fputs(s,F) -> fwrite(s,1,len,F) (if s is constant and strlen(s) > 1)
1660 const Type* FILEptr_type = ci->getOperand(2)->getType();
1661 std::vector<Value*> parms;
1662 parms.push_back(ci->getOperand(1));
1663 parms.push_back(ConstantInt::get(SLC.getIntPtrType(),len));
1664 parms.push_back(ConstantInt::get(SLC.getIntPtrType(),1));
1665 parms.push_back(ci->getOperand(2));
1666 new CallInst(SLC.get_fwrite(FILEptr_type), parms, "", ci);
1670 ci->eraseFromParent();
1671 return true; // success
1675 /// This LibCallOptimization will simplify calls to the "isdigit" library
1676 /// function. It simply does range checks the parameter explicitly.
1677 /// @brief Simplify the isdigit library function.
1678 struct isdigitOptimization : public LibCallOptimization {
1680 isdigitOptimization() : LibCallOptimization("isdigit",
1681 "Number of 'isdigit' calls simplified") {}
1683 /// @brief Make sure that the "isdigit" function has the right prototype
1684 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC){
1685 // Just make sure this has 1 argument
1686 return (f->arg_size() == 1);
1689 /// @brief Perform the toascii optimization.
1690 virtual bool OptimizeCall(CallInst *ci, SimplifyLibCalls &SLC) {
1691 if (ConstantInt* CI = dyn_cast<ConstantInt>(ci->getOperand(1))) {
1692 // isdigit(c) -> 0 or 1, if 'c' is constant
1693 uint64_t val = CI->getZExtValue();
1694 if (val >= '0' && val <='9')
1695 ci->replaceAllUsesWith(ConstantInt::get(Type::Int32Ty,1));
1697 ci->replaceAllUsesWith(ConstantInt::get(Type::Int32Ty,0));
1698 ci->eraseFromParent();
1702 // isdigit(c) -> (unsigned)c - '0' <= 9
1703 CastInst* cast = CastInst::createIntegerCast(ci->getOperand(1),
1704 Type::Int32Ty, false/*ZExt*/, ci->getOperand(1)->getName()+".uint", ci);
1705 BinaryOperator* sub_inst = BinaryOperator::createSub(cast,
1706 ConstantInt::get(Type::Int32Ty,0x30),
1707 ci->getOperand(1)->getName()+".sub",ci);
1708 ICmpInst* setcond_inst = new ICmpInst(ICmpInst::ICMP_ULE,sub_inst,
1709 ConstantInt::get(Type::Int32Ty,9),
1710 ci->getOperand(1)->getName()+".cmp",ci);
1711 CastInst* c2 = new ZExtInst(setcond_inst, Type::Int32Ty,
1712 ci->getOperand(1)->getName()+".isdigit", ci);
1713 ci->replaceAllUsesWith(c2);
1714 ci->eraseFromParent();
1719 struct isasciiOptimization : public LibCallOptimization {
1721 isasciiOptimization()
1722 : LibCallOptimization("isascii", "Number of 'isascii' calls simplified") {}
1724 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
1725 return F->arg_size() == 1 && F->arg_begin()->getType()->isInteger() &&
1726 F->getReturnType()->isInteger();
1729 /// @brief Perform the isascii optimization.
1730 virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
1731 // isascii(c) -> (unsigned)c < 128
1732 Value *V = CI->getOperand(1);
1733 Value *Cmp = new ICmpInst(ICmpInst::ICMP_ULT, V,
1734 ConstantInt::get(V->getType(), 128),
1735 V->getName()+".isascii", CI);
1736 if (Cmp->getType() != CI->getType())
1737 Cmp = new BitCastInst(Cmp, CI->getType(), Cmp->getName(), CI);
1738 CI->replaceAllUsesWith(Cmp);
1739 CI->eraseFromParent();
1745 /// This LibCallOptimization will simplify calls to the "toascii" library
1746 /// function. It simply does the corresponding and operation to restrict the
1747 /// range of values to the ASCII character set (0-127).
1748 /// @brief Simplify the toascii library function.
1749 struct ToAsciiOptimization : public LibCallOptimization {
1751 /// @brief Default Constructor
1752 ToAsciiOptimization() : LibCallOptimization("toascii",
1753 "Number of 'toascii' calls simplified") {}
1755 /// @brief Make sure that the "fputs" function has the right prototype
1756 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC){
1757 // Just make sure this has 2 arguments
1758 return (f->arg_size() == 1);
1761 /// @brief Perform the toascii optimization.
1762 virtual bool OptimizeCall(CallInst *ci, SimplifyLibCalls &SLC) {
1763 // toascii(c) -> (c & 0x7f)
1764 Value* chr = ci->getOperand(1);
1765 BinaryOperator* and_inst = BinaryOperator::createAnd(chr,
1766 ConstantInt::get(chr->getType(),0x7F),ci->getName()+".toascii",ci);
1767 ci->replaceAllUsesWith(and_inst);
1768 ci->eraseFromParent();
1773 /// This LibCallOptimization will simplify calls to the "ffs" library
1774 /// calls which find the first set bit in an int, long, or long long. The
1775 /// optimization is to compute the result at compile time if the argument is
1777 /// @brief Simplify the ffs library function.
1778 struct FFSOptimization : public LibCallOptimization {
1780 /// @brief Subclass Constructor
1781 FFSOptimization(const char* funcName, const char* description)
1782 : LibCallOptimization(funcName, description) {}
1785 /// @brief Default Constructor
1786 FFSOptimization() : LibCallOptimization("ffs",
1787 "Number of 'ffs' calls simplified") {}
1789 /// @brief Make sure that the "ffs" function has the right prototype
1790 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
1791 // Just make sure this has 2 arguments
1792 return F->arg_size() == 1 && F->getReturnType() == Type::Int32Ty;
1795 /// @brief Perform the ffs optimization.
1796 virtual bool OptimizeCall(CallInst *TheCall, SimplifyLibCalls &SLC) {
1797 if (ConstantInt *CI = dyn_cast<ConstantInt>(TheCall->getOperand(1))) {
1798 // ffs(cnst) -> bit#
1799 // ffsl(cnst) -> bit#
1800 // ffsll(cnst) -> bit#
1801 uint64_t val = CI->getZExtValue();
1805 while ((val & 1) == 0) {
1810 TheCall->replaceAllUsesWith(ConstantInt::get(Type::Int32Ty, result));
1811 TheCall->eraseFromParent();
1815 // ffs(x) -> x == 0 ? 0 : llvm.cttz(x)+1
1816 // ffsl(x) -> x == 0 ? 0 : llvm.cttz(x)+1
1817 // ffsll(x) -> x == 0 ? 0 : llvm.cttz(x)+1
1818 const Type *ArgType = TheCall->getOperand(1)->getType();
1819 const char *CTTZName;
1820 assert(ArgType->getTypeID() == Type::IntegerTyID &&
1821 "llvm.cttz argument is not an integer?");
1822 unsigned BitWidth = cast<IntegerType>(ArgType)->getBitWidth();
1824 CTTZName = "llvm.cttz.i8";
1825 else if (BitWidth == 16)
1826 CTTZName = "llvm.cttz.i16";
1827 else if (BitWidth == 32)
1828 CTTZName = "llvm.cttz.i32";
1830 assert(BitWidth == 64 && "Unknown bitwidth");
1831 CTTZName = "llvm.cttz.i64";
1834 Constant *F = SLC.getModule()->getOrInsertFunction(CTTZName, ArgType,
1836 Value *V = CastInst::createIntegerCast(TheCall->getOperand(1), ArgType,
1837 false/*ZExt*/, "tmp", TheCall);
1838 Value *V2 = new CallInst(F, V, "tmp", TheCall);
1839 V2 = CastInst::createIntegerCast(V2, Type::Int32Ty, false/*ZExt*/,
1841 V2 = BinaryOperator::createAdd(V2, ConstantInt::get(Type::Int32Ty, 1),
1843 Value *Cond = new ICmpInst(ICmpInst::ICMP_EQ, V,
1844 Constant::getNullValue(V->getType()), "tmp",
1846 V2 = new SelectInst(Cond, ConstantInt::get(Type::Int32Ty, 0), V2,
1847 TheCall->getName(), TheCall);
1848 TheCall->replaceAllUsesWith(V2);
1849 TheCall->eraseFromParent();
1854 /// This LibCallOptimization will simplify calls to the "ffsl" library
1855 /// calls. It simply uses FFSOptimization for which the transformation is
1857 /// @brief Simplify the ffsl library function.
1858 struct FFSLOptimization : public FFSOptimization {
1860 /// @brief Default Constructor
1861 FFSLOptimization() : FFSOptimization("ffsl",
1862 "Number of 'ffsl' calls simplified") {}
1866 /// This LibCallOptimization will simplify calls to the "ffsll" library
1867 /// calls. It simply uses FFSOptimization for which the transformation is
1869 /// @brief Simplify the ffsl library function.
1870 struct FFSLLOptimization : public FFSOptimization {
1872 /// @brief Default Constructor
1873 FFSLLOptimization() : FFSOptimization("ffsll",
1874 "Number of 'ffsll' calls simplified") {}
1878 /// This optimizes unary functions that take and return doubles.
1879 struct UnaryDoubleFPOptimizer : public LibCallOptimization {
1880 UnaryDoubleFPOptimizer(const char *Fn, const char *Desc)
1881 : LibCallOptimization(Fn, Desc) {}
1883 // Make sure that this function has the right prototype
1884 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
1885 return F->arg_size() == 1 && F->arg_begin()->getType() == Type::DoubleTy &&
1886 F->getReturnType() == Type::DoubleTy;
1889 /// ShrinkFunctionToFloatVersion - If the input to this function is really a
1890 /// float, strength reduce this to a float version of the function,
1891 /// e.g. floor((double)FLT) -> (double)floorf(FLT). This can only be called
1892 /// when the target supports the destination function and where there can be
1893 /// no precision loss.
1894 static bool ShrinkFunctionToFloatVersion(CallInst *CI, SimplifyLibCalls &SLC,
1895 Constant *(SimplifyLibCalls::*FP)()){
1896 if (CastInst *Cast = dyn_cast<CastInst>(CI->getOperand(1)))
1897 if (Cast->getOperand(0)->getType() == Type::FloatTy) {
1898 Value *New = new CallInst((SLC.*FP)(), Cast->getOperand(0),
1900 New = new FPExtInst(New, Type::DoubleTy, CI->getName(), CI);
1901 CI->replaceAllUsesWith(New);
1902 CI->eraseFromParent();
1903 if (Cast->use_empty())
1904 Cast->eraseFromParent();
1912 struct FloorOptimization : public UnaryDoubleFPOptimizer {
1914 : UnaryDoubleFPOptimizer("floor", "Number of 'floor' calls simplified") {}
1916 virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
1918 // If this is a float argument passed in, convert to floorf.
1919 if (ShrinkFunctionToFloatVersion(CI, SLC, &SimplifyLibCalls::get_floorf))
1922 return false; // opt failed
1926 struct CeilOptimization : public UnaryDoubleFPOptimizer {
1928 : UnaryDoubleFPOptimizer("ceil", "Number of 'ceil' calls simplified") {}
1930 virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
1932 // If this is a float argument passed in, convert to ceilf.
1933 if (ShrinkFunctionToFloatVersion(CI, SLC, &SimplifyLibCalls::get_ceilf))
1936 return false; // opt failed
1940 struct RoundOptimization : public UnaryDoubleFPOptimizer {
1942 : UnaryDoubleFPOptimizer("round", "Number of 'round' calls simplified") {}
1944 virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
1946 // If this is a float argument passed in, convert to roundf.
1947 if (ShrinkFunctionToFloatVersion(CI, SLC, &SimplifyLibCalls::get_roundf))
1950 return false; // opt failed
1954 struct RintOptimization : public UnaryDoubleFPOptimizer {
1956 : UnaryDoubleFPOptimizer("rint", "Number of 'rint' calls simplified") {}
1958 virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
1960 // If this is a float argument passed in, convert to rintf.
1961 if (ShrinkFunctionToFloatVersion(CI, SLC, &SimplifyLibCalls::get_rintf))
1964 return false; // opt failed
1968 struct NearByIntOptimization : public UnaryDoubleFPOptimizer {
1969 NearByIntOptimization()
1970 : UnaryDoubleFPOptimizer("nearbyint",
1971 "Number of 'nearbyint' calls simplified") {}
1973 virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
1974 #ifdef HAVE_NEARBYINTF
1975 // If this is a float argument passed in, convert to nearbyintf.
1976 if (ShrinkFunctionToFloatVersion(CI, SLC,&SimplifyLibCalls::get_nearbyintf))
1979 return false; // opt failed
1981 } NearByIntOptimizer;
1983 /// A function to compute the length of a null-terminated constant array of
1984 /// integers. This function can't rely on the size of the constant array
1985 /// because there could be a null terminator in the middle of the array.
1986 /// We also have to bail out if we find a non-integer constant initializer
1987 /// of one of the elements or if there is no null-terminator. The logic
1988 /// below checks each of these conditions and will return true only if all
1989 /// conditions are met. In that case, the \p len parameter is set to the length
1990 /// of the null-terminated string. If false is returned, the conditions were
1991 /// not met and len is set to 0.
1992 /// @brief Get the length of a constant string (null-terminated array).
1993 bool getConstantStringLength(Value *V, uint64_t &len, ConstantArray **CA) {
1994 assert(V != 0 && "Invalid args to getConstantStringLength");
1995 len = 0; // make sure we initialize this
1997 // If the value is not a GEP instruction nor a constant expression with a
1998 // GEP instruction, then return false because ConstantArray can't occur
2000 if (GetElementPtrInst* GEPI = dyn_cast<GetElementPtrInst>(V))
2002 else if (ConstantExpr* CE = dyn_cast<ConstantExpr>(V))
2003 if (CE->getOpcode() == Instruction::GetElementPtr)
2010 // Make sure the GEP has exactly three arguments.
2011 if (GEP->getNumOperands() != 3)
2014 // Check to make sure that the first operand of the GEP is an integer and
2015 // has value 0 so that we are sure we're indexing into the initializer.
2016 if (ConstantInt* op1 = dyn_cast<ConstantInt>(GEP->getOperand(1))) {
2017 if (!op1->isNullValue())
2022 // Ensure that the second operand is a ConstantInt. If it isn't then this
2023 // GEP is wonky and we're not really sure what were referencing into and
2024 // better of not optimizing it. While we're at it, get the second index
2025 // value. We'll need this later for indexing the ConstantArray.
2026 uint64_t start_idx = 0;
2027 if (ConstantInt* CI = dyn_cast<ConstantInt>(GEP->getOperand(2)))
2028 start_idx = CI->getZExtValue();
2032 // The GEP instruction, constant or instruction, must reference a global
2033 // variable that is a constant and is initialized. The referenced constant
2034 // initializer is the array that we'll use for optimization.
2035 GlobalVariable* GV = dyn_cast<GlobalVariable>(GEP->getOperand(0));
2036 if (!GV || !GV->isConstant() || !GV->hasInitializer())
2039 // Get the initializer.
2040 Constant* INTLZR = GV->getInitializer();
2042 // Handle the ConstantAggregateZero case
2043 if (isa<ConstantAggregateZero>(INTLZR)) {
2044 // This is a degenerate case. The initializer is constant zero so the
2045 // length of the string must be zero.
2050 // Must be a Constant Array
2051 ConstantArray* A = dyn_cast<ConstantArray>(INTLZR);
2055 // Get the number of elements in the array
2056 uint64_t max_elems = A->getType()->getNumElements();
2058 // Traverse the constant array from start_idx (derived above) which is
2059 // the place the GEP refers to in the array.
2060 for (len = start_idx; len < max_elems; len++) {
2061 if (ConstantInt *CI = dyn_cast<ConstantInt>(A->getOperand(len))) {
2062 // Check for the null terminator
2063 if (CI->isNullValue())
2064 break; // we found end of string
2066 return false; // This array isn't suitable, non-int initializer
2069 if (len >= max_elems)
2070 return false; // This array isn't null terminated
2072 // Subtract out the initial value from the length
2076 return true; // success!
2079 /// CastToCStr - Return V if it is an sbyte*, otherwise cast it to sbyte*,
2080 /// inserting the cast before IP, and return the cast.
2081 /// @brief Cast a value to a "C" string.
2082 Value *CastToCStr(Value *V, Instruction &IP) {
2083 assert(isa<PointerType>(V->getType()) &&
2084 "Can't cast non-pointer type to C string type");
2085 const Type *SBPTy = PointerType::get(Type::Int8Ty);
2086 if (V->getType() != SBPTy)
2087 return new BitCastInst(V, SBPTy, V->getName(), &IP);
2092 // Additional cases that we need to add to this file:
2095 // * cbrt(expN(X)) -> expN(x/3)
2096 // * cbrt(sqrt(x)) -> pow(x,1/6)
2097 // * cbrt(sqrt(x)) -> pow(x,1/9)
2100 // * cos(-x) -> cos(x)
2103 // * exp(log(x)) -> x
2106 // * log(exp(x)) -> x
2107 // * log(x**y) -> y*log(x)
2108 // * log(exp(y)) -> y*log(e)
2109 // * log(exp2(y)) -> y*log(2)
2110 // * log(exp10(y)) -> y*log(10)
2111 // * log(sqrt(x)) -> 0.5*log(x)
2112 // * log(pow(x,y)) -> y*log(x)
2114 // lround, lroundf, lroundl:
2115 // * lround(cnst) -> cnst'
2118 // * memcmp(x,y,l) -> cnst
2119 // (if all arguments are constant and strlen(x) <= l and strlen(y) <= l)
2122 // * memmove(d,s,l,a) -> memcpy(d,s,l,a)
2123 // (if s is a global constant array)
2126 // * pow(exp(x),y) -> exp(x*y)
2127 // * pow(sqrt(x),y) -> pow(x,y*0.5)
2128 // * pow(pow(x,y),z)-> pow(x,y*z)
2131 // * puts("") -> fputc("\n",stdout) (how do we get "stdout"?)
2133 // round, roundf, roundl:
2134 // * round(cnst) -> cnst'
2137 // * signbit(cnst) -> cnst'
2138 // * signbit(nncst) -> 0 (if pstv is a non-negative constant)
2140 // sqrt, sqrtf, sqrtl:
2141 // * sqrt(expN(x)) -> expN(x*0.5)
2142 // * sqrt(Nroot(x)) -> pow(x,1/(2*N))
2143 // * sqrt(pow(x,y)) -> pow(|x|,y*0.5)
2146 // * stpcpy(str, "literal") ->
2147 // llvm.memcpy(str,"literal",strlen("literal")+1,1)
2149 // * strrchr(s,c) -> reverse_offset_of_in(c,s)
2150 // (if c is a constant integer and s is a constant string)
2151 // * strrchr(s1,0) -> strchr(s1,0)
2154 // * strncat(x,y,0) -> x
2155 // * strncat(x,y,0) -> x (if strlen(y) = 0)
2156 // * strncat(x,y,l) -> strcat(x,y) (if y and l are constants an l > strlen(y))
2159 // * strncpy(d,s,0) -> d
2160 // * strncpy(d,s,l) -> memcpy(d,s,l,1)
2161 // (if s and l are constants)
2164 // * strpbrk(s,a) -> offset_in_for(s,a)
2165 // (if s and a are both constant strings)
2166 // * strpbrk(s,"") -> 0
2167 // * strpbrk(s,a) -> strchr(s,a[0]) (if a is constant string of length 1)
2170 // * strspn(s,a) -> const_int (if both args are constant)
2171 // * strspn("",a) -> 0
2172 // * strspn(s,"") -> 0
2173 // * strcspn(s,a) -> const_int (if both args are constant)
2174 // * strcspn("",a) -> 0
2175 // * strcspn(s,"") -> strlen(a)
2178 // * strstr(x,x) -> x
2179 // * strstr(s1,s2) -> offset_of_s2_in(s1)
2180 // (if s1 and s2 are constant strings)
2183 // * tan(atan(x)) -> x
2185 // trunc, truncf, truncl:
2186 // * trunc(cnst) -> cnst'