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/Compiler.h"
30 #include "llvm/Support/Debug.h"
31 #include "llvm/Target/TargetData.h"
32 #include "llvm/Transforms/IPO.h"
35 /// This statistic keeps track of the total number of library calls that have
36 /// been simplified regardless of which call it is.
37 STATISTIC(SimplifiedLibCalls, "Number of library calls simplified");
40 // Forward declarations
41 class LibCallOptimization;
42 class SimplifyLibCalls;
44 /// This list is populated by the constructor for LibCallOptimization class.
45 /// Therefore all subclasses are registered here at static initialization time
46 /// and this list is what the SimplifyLibCalls pass uses to apply the individual
47 /// optimizations to the call sites.
48 /// @brief The list of optimizations deriving from LibCallOptimization
49 static LibCallOptimization *OptList = 0;
51 /// This class is the abstract base class for the set of optimizations that
52 /// corresponds to one library call. The SimplifyLibCalls pass will call the
53 /// ValidateCalledFunction method to ask the optimization if a given Function
54 /// is the kind that the optimization can handle. If the subclass returns true,
55 /// then SImplifyLibCalls will also call the OptimizeCall method to perform,
56 /// or attempt to perform, the optimization(s) for the library call. Otherwise,
57 /// OptimizeCall won't be called. Subclasses are responsible for providing the
58 /// name of the library call (strlen, strcpy, etc.) to the LibCallOptimization
59 /// constructor. This is used to efficiently select which call instructions to
60 /// optimize. The criteria for a "lib call" is "anything with well known
61 /// semantics", typically a library function that is defined by an international
62 /// standard. Because the semantics are well known, the optimizations can
63 /// generally short-circuit actually calling the function if there's a simpler
64 /// way (e.g. strlen(X) can be reduced to a constant if X is a constant global).
65 /// @brief Base class for library call optimizations
66 class VISIBILITY_HIDDEN LibCallOptimization {
67 LibCallOptimization **Prev, *Next;
68 const char *FunctionName; ///< Name of the library call we optimize
70 Statistic occurrences; ///< debug statistic (-debug-only=simplify-libcalls)
73 /// The \p fname argument must be the name of the library function being
74 /// optimized by the subclass.
75 /// @brief Constructor that registers the optimization.
76 LibCallOptimization(const char *FName, const char *Description)
77 : FunctionName(FName) {
80 occurrences.construct("simplify-libcalls", Description);
82 // Register this optimizer in the list of optimizations.
86 if (Next) Next->Prev = &Next;
89 /// getNext - All libcall optimizations are chained together into a list,
90 /// return the next one in the list.
91 LibCallOptimization *getNext() { return Next; }
93 /// @brief Deregister from the optlist
94 virtual ~LibCallOptimization() {
96 if (Next) Next->Prev = Prev;
99 /// The implementation of this function in subclasses should determine if
100 /// \p F is suitable for the optimization. This method is called by
101 /// SimplifyLibCalls::runOnModule to short circuit visiting all the call
102 /// sites of such a function if that function is not suitable in the first
103 /// place. If the called function is suitabe, this method should return true;
104 /// false, otherwise. This function should also perform any lazy
105 /// initialization that the LibCallOptimization needs to do, if its to return
106 /// true. This avoids doing initialization until the optimizer is actually
107 /// going to be called upon to do some optimization.
108 /// @brief Determine if the function is suitable for optimization
109 virtual bool ValidateCalledFunction(
110 const Function* F, ///< The function that is the target of call sites
111 SimplifyLibCalls& SLC ///< The pass object invoking us
114 /// The implementations of this function in subclasses is the heart of the
115 /// SimplifyLibCalls algorithm. Sublcasses of this class implement
116 /// OptimizeCall to determine if (a) the conditions are right for optimizing
117 /// the call and (b) to perform the optimization. If an action is taken
118 /// against ci, the subclass is responsible for returning true and ensuring
119 /// that ci is erased from its parent.
120 /// @brief Optimize a call, if possible.
121 virtual bool OptimizeCall(
122 CallInst* ci, ///< The call instruction that should be optimized.
123 SimplifyLibCalls& SLC ///< The pass object invoking us
126 /// @brief Get the name of the library call being optimized
127 const char *getFunctionName() const { return FunctionName; }
129 /// @brief Called by SimplifyLibCalls to update the occurrences statistic.
132 DEBUG(++occurrences);
137 /// This class is an LLVM Pass that applies each of the LibCallOptimization
138 /// instances to all the call sites in a module, relatively efficiently. The
139 /// purpose of this pass is to provide optimizations for calls to well-known
140 /// functions with well-known semantics, such as those in the c library. The
141 /// class provides the basic infrastructure for handling runOnModule. Whenever
142 /// this pass finds a function call, it asks the appropriate optimizer to
143 /// validate the call (ValidateLibraryCall). If it is validated, then
144 /// the OptimizeCall method is also called.
145 /// @brief A ModulePass for optimizing well-known function calls.
146 class VISIBILITY_HIDDEN SimplifyLibCalls : public ModulePass {
148 /// We need some target data for accurate signature details that are
149 /// target dependent. So we require target data in our AnalysisUsage.
150 /// @brief Require TargetData from AnalysisUsage.
151 virtual void getAnalysisUsage(AnalysisUsage& Info) const {
152 // Ask that the TargetData analysis be performed before us so we can use
154 Info.addRequired<TargetData>();
157 /// For this pass, process all of the function calls in the module, calling
158 /// ValidateLibraryCall and OptimizeCall as appropriate.
159 /// @brief Run all the lib call optimizations on a Module.
160 virtual bool runOnModule(Module &M) {
164 hash_map<std::string, LibCallOptimization*> OptznMap;
165 for (LibCallOptimization *Optzn = OptList; Optzn; Optzn = Optzn->getNext())
166 OptznMap[Optzn->getFunctionName()] = Optzn;
168 // The call optimizations can be recursive. That is, the optimization might
169 // generate a call to another function which can also be optimized. This way
170 // we make the LibCallOptimization instances very specific to the case they
171 // handle. It also means we need to keep running over the function calls in
172 // the module until we don't get any more optimizations possible.
173 bool found_optimization = false;
175 found_optimization = false;
176 for (Module::iterator FI = M.begin(), FE = M.end(); FI != FE; ++FI) {
177 // All the "well-known" functions are external and have external linkage
178 // because they live in a runtime library somewhere and were (probably)
179 // not compiled by LLVM. So, we only act on external functions that
180 // have external or dllimport linkage and non-empty uses.
181 if (!FI->isDeclaration() ||
182 !(FI->hasExternalLinkage() || FI->hasDLLImportLinkage()) ||
186 // Get the optimization class that pertains to this function
187 hash_map<std::string, LibCallOptimization*>::iterator OMI =
188 OptznMap.find(FI->getName());
189 if (OMI == OptznMap.end()) continue;
191 LibCallOptimization *CO = OMI->second;
193 // Make sure the called function is suitable for the optimization
194 if (!CO->ValidateCalledFunction(FI, *this))
197 // Loop over each of the uses of the function
198 for (Value::use_iterator UI = FI->use_begin(), UE = FI->use_end();
200 // If the use of the function is a call instruction
201 if (CallInst* CI = dyn_cast<CallInst>(*UI++)) {
202 // Do the optimization on the LibCallOptimization.
203 if (CO->OptimizeCall(CI, *this)) {
204 ++SimplifiedLibCalls;
205 found_optimization = result = true;
211 } while (found_optimization);
216 /// @brief Return the *current* module we're working on.
217 Module* getModule() const { return M; }
219 /// @brief Return the *current* target data for the module we're working on.
220 TargetData* getTargetData() const { return TD; }
222 /// @brief Return the size_t type -- syntactic shortcut
223 const Type* getIntPtrType() const { return TD->getIntPtrType(); }
225 /// @brief Return a Function* for the putchar libcall
226 Constant *get_putchar() {
229 M->getOrInsertFunction("putchar", Type::Int32Ty, Type::Int32Ty, NULL);
233 /// @brief Return a Function* for the puts libcall
234 Constant *get_puts() {
236 puts_func = M->getOrInsertFunction("puts", Type::Int32Ty,
237 PointerType::get(Type::Int8Ty),
242 /// @brief Return a Function* for the fputc libcall
243 Constant *get_fputc(const Type* FILEptr_type) {
245 fputc_func = M->getOrInsertFunction("fputc", Type::Int32Ty, Type::Int32Ty,
250 /// @brief Return a Function* for the fputs libcall
251 Constant *get_fputs(const Type* FILEptr_type) {
253 fputs_func = M->getOrInsertFunction("fputs", Type::Int32Ty,
254 PointerType::get(Type::Int8Ty),
259 /// @brief Return a Function* for the fwrite libcall
260 Constant *get_fwrite(const Type* FILEptr_type) {
262 fwrite_func = M->getOrInsertFunction("fwrite", TD->getIntPtrType(),
263 PointerType::get(Type::Int8Ty),
270 /// @brief Return a Function* for the sqrt libcall
271 Constant *get_sqrt() {
273 sqrt_func = M->getOrInsertFunction("sqrt", Type::DoubleTy,
274 Type::DoubleTy, NULL);
278 /// @brief Return a Function* for the strcpy libcall
279 Constant *get_strcpy() {
281 strcpy_func = M->getOrInsertFunction("strcpy",
282 PointerType::get(Type::Int8Ty),
283 PointerType::get(Type::Int8Ty),
284 PointerType::get(Type::Int8Ty),
289 /// @brief Return a Function* for the strlen libcall
290 Constant *get_strlen() {
292 strlen_func = M->getOrInsertFunction("strlen", TD->getIntPtrType(),
293 PointerType::get(Type::Int8Ty),
298 /// @brief Return a Function* for the memchr libcall
299 Constant *get_memchr() {
301 memchr_func = M->getOrInsertFunction("memchr",
302 PointerType::get(Type::Int8Ty),
303 PointerType::get(Type::Int8Ty),
304 Type::Int32Ty, TD->getIntPtrType(),
309 /// @brief Return a Function* for the memcpy libcall
310 Constant *get_memcpy() {
312 const Type *SBP = PointerType::get(Type::Int8Ty);
313 const char *N = TD->getIntPtrType() == Type::Int32Ty ?
314 "llvm.memcpy.i32" : "llvm.memcpy.i64";
315 memcpy_func = M->getOrInsertFunction(N, Type::VoidTy, SBP, SBP,
316 TD->getIntPtrType(), Type::Int32Ty,
322 Constant *getUnaryFloatFunction(const char *Name, Constant *&Cache) {
324 Cache = M->getOrInsertFunction(Name, Type::FloatTy, Type::FloatTy, NULL);
328 Constant *get_floorf() { return getUnaryFloatFunction("floorf", floorf_func);}
329 Constant *get_ceilf() { return getUnaryFloatFunction( "ceilf", ceilf_func);}
330 Constant *get_roundf() { return getUnaryFloatFunction("roundf", roundf_func);}
331 Constant *get_rintf() { return getUnaryFloatFunction( "rintf", rintf_func);}
332 Constant *get_nearbyintf() { return getUnaryFloatFunction("nearbyintf",
335 /// @brief Reset our cached data for a new Module
336 void reset(Module& mod) {
338 TD = &getAnalysis<TargetData>();
357 /// Caches for function pointers.
358 Constant *putchar_func, *puts_func;
359 Constant *fputc_func, *fputs_func, *fwrite_func;
360 Constant *memcpy_func, *memchr_func;
362 Constant *strcpy_func, *strlen_func;
363 Constant *floorf_func, *ceilf_func, *roundf_func;
364 Constant *rintf_func, *nearbyintf_func;
365 Module *M; ///< Cached Module
366 TargetData *TD; ///< Cached TargetData
370 RegisterPass<SimplifyLibCalls>
371 X("simplify-libcalls", "Simplify well-known library calls");
373 } // anonymous namespace
375 // The only public symbol in this file which just instantiates the pass object
376 ModulePass *llvm::createSimplifyLibCallsPass() {
377 return new SimplifyLibCalls();
380 // Classes below here, in the anonymous namespace, are all subclasses of the
381 // LibCallOptimization class, each implementing all optimizations possible for a
382 // single well-known library call. Each has a static singleton instance that
383 // auto registers it into the "optlist" global above.
386 // Forward declare utility functions.
387 static bool getConstantStringLength(Value* V, uint64_t& len,
388 ConstantArray** A = 0 );
389 static Value *CastToCStr(Value *V, Instruction &IP);
391 /// This LibCallOptimization will find instances of a call to "exit" that occurs
392 /// within the "main" function and change it to a simple "ret" instruction with
393 /// the same value passed to the exit function. When this is done, it splits the
394 /// basic block at the exit(3) call and deletes the call instruction.
395 /// @brief Replace calls to exit in main with a simple return
396 struct VISIBILITY_HIDDEN ExitInMainOptimization : public LibCallOptimization {
397 ExitInMainOptimization() : LibCallOptimization("exit",
398 "Number of 'exit' calls simplified") {}
400 // Make sure the called function looks like exit (int argument, int return
401 // type, external linkage, not varargs).
402 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
403 return F->arg_size() >= 1 && F->arg_begin()->getType()->isInteger();
406 virtual bool OptimizeCall(CallInst* ci, SimplifyLibCalls& SLC) {
407 // To be careful, we check that the call to exit is coming from "main", that
408 // main has external linkage, and the return type of main and the argument
409 // to exit have the same type.
410 Function *from = ci->getParent()->getParent();
411 if (from->hasExternalLinkage())
412 if (from->getReturnType() == ci->getOperand(1)->getType())
413 if (from->getName() == "main") {
414 // Okay, time to actually do the optimization. First, get the basic
415 // block of the call instruction
416 BasicBlock* bb = ci->getParent();
418 // Create a return instruction that we'll replace the call with.
419 // Note that the argument of the return is the argument of the call
421 new ReturnInst(ci->getOperand(1), ci);
423 // Split the block at the call instruction which places it in a new
425 bb->splitBasicBlock(ci);
427 // The block split caused a branch instruction to be inserted into
428 // the end of the original block, right after the return instruction
429 // that we put there. That's not a valid block, so delete the branch
431 bb->getInstList().pop_back();
433 // Now we can finally get rid of the call instruction which now lives
434 // in the new basic block.
435 ci->eraseFromParent();
437 // Optimization succeeded, return true.
440 // We didn't pass the criteria for this optimization so return false
443 } ExitInMainOptimizer;
445 /// This LibCallOptimization will simplify a call to the strcat library
446 /// function. The simplification is possible only if the string being
447 /// concatenated is a constant array or a constant expression that results in
448 /// a constant string. In this case we can replace it with strlen + llvm.memcpy
449 /// of the constant string. Both of these calls are further reduced, if possible
450 /// on subsequent passes.
451 /// @brief Simplify the strcat library function.
452 struct VISIBILITY_HIDDEN StrCatOptimization : public LibCallOptimization {
454 /// @brief Default constructor
455 StrCatOptimization() : LibCallOptimization("strcat",
456 "Number of 'strcat' calls simplified") {}
460 /// @brief Make sure that the "strcat" function has the right prototype
461 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC){
462 if (f->getReturnType() == PointerType::get(Type::Int8Ty))
463 if (f->arg_size() == 2)
465 Function::const_arg_iterator AI = f->arg_begin();
466 if (AI++->getType() == PointerType::get(Type::Int8Ty))
467 if (AI->getType() == PointerType::get(Type::Int8Ty))
469 // Indicate this is a suitable call type.
476 /// @brief Optimize the strcat library function
477 virtual bool OptimizeCall(CallInst* ci, SimplifyLibCalls& SLC) {
478 // Extract some information from the instruction
479 Value* dest = ci->getOperand(1);
480 Value* src = ci->getOperand(2);
482 // Extract the initializer (while making numerous checks) from the
483 // source operand of the call to strcat. If we get null back, one of
484 // a variety of checks in get_GVInitializer failed
486 if (!getConstantStringLength(src,len))
489 // Handle the simple, do-nothing case
491 ci->replaceAllUsesWith(dest);
492 ci->eraseFromParent();
496 // Increment the length because we actually want to memcpy the null
497 // terminator as well.
500 // We need to find the end of the destination string. That's where the
501 // memory is to be moved to. We just generate a call to strlen (further
502 // optimized in another pass). Note that the SLC.get_strlen() call
503 // caches the Function* for us.
504 CallInst* strlen_inst =
505 new CallInst(SLC.get_strlen(), dest, dest->getName()+".len",ci);
507 // Now that we have the destination's length, we must index into the
508 // destination's pointer to get the actual memcpy destination (end of
509 // the string .. we're concatenating).
510 GetElementPtrInst* gep =
511 new GetElementPtrInst(dest, strlen_inst, dest->getName()+".indexed", ci);
513 // We have enough information to now generate the memcpy call to
514 // do the concatenation for us.
516 vals[0] = gep; // destination
517 vals[1] = ci->getOperand(2); // source
518 vals[2] = ConstantInt::get(SLC.getIntPtrType(),len); // length
519 vals[3] = ConstantInt::get(Type::Int32Ty,1); // alignment
520 new CallInst(SLC.get_memcpy(), vals, 4, "", 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 VISIBILITY_HIDDEN StrChrOptimization : public LibCallOptimization {
537 StrChrOptimization() : LibCallOptimization("strchr",
538 "Number of 'strchr' calls simplified") {}
540 /// @brief Make sure that the "strchr" function has the right prototype
541 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC){
542 if (f->getReturnType() == PointerType::get(Type::Int8Ty) &&
548 /// @brief Perform the strchr optimizations
549 virtual bool OptimizeCall(CallInst *ci, SimplifyLibCalls &SLC) {
550 // If there aren't three operands, bail
551 if (ci->getNumOperands() != 3)
554 // Check that the first argument to strchr is a constant array of sbyte.
555 // If it is, get the length and data, otherwise return false.
557 ConstantArray* CA = 0;
558 if (!getConstantStringLength(ci->getOperand(1), len, &CA))
561 // Check that the second argument to strchr is a constant int. If it isn't
562 // a constant signed integer, we can try an alternate optimization
563 ConstantInt* CSI = dyn_cast<ConstantInt>(ci->getOperand(2));
565 // The second operand is not constant, or not signed. Just lower this to
566 // memchr since we know the length of the string since it is constant.
567 Constant *f = SLC.get_memchr();
571 ConstantInt::get(SLC.getIntPtrType(), len)
573 ci->replaceAllUsesWith(new CallInst(f, args, 3, ci->getName(), ci));
574 ci->eraseFromParent();
578 // Get the character we're looking for
579 int64_t chr = CSI->getSExtValue();
581 // Compute the offset
583 bool char_found = false;
584 for (uint64_t i = 0; i < len; ++i) {
585 if (ConstantInt* CI = dyn_cast<ConstantInt>(CA->getOperand(i))) {
586 // Check for the null terminator
588 break; // we found end of string
589 else if (CI->getSExtValue() == chr) {
597 // strchr(s,c) -> offset_of_in(c,s)
598 // (if c is a constant integer and s is a constant string)
600 Value* Idx = ConstantInt::get(Type::Int64Ty,offset);
601 GetElementPtrInst* GEP = new GetElementPtrInst(ci->getOperand(1), Idx,
602 ci->getOperand(1)->getName()+".strchr",ci);
603 ci->replaceAllUsesWith(GEP);
605 ci->replaceAllUsesWith(
606 ConstantPointerNull::get(PointerType::get(Type::Int8Ty)));
608 ci->eraseFromParent();
613 /// This LibCallOptimization will simplify a call to the strcmp library
614 /// function. It optimizes out cases where one or both arguments are constant
615 /// and the result can be determined statically.
616 /// @brief Simplify the strcmp library function.
617 struct VISIBILITY_HIDDEN StrCmpOptimization : public LibCallOptimization {
619 StrCmpOptimization() : LibCallOptimization("strcmp",
620 "Number of 'strcmp' calls simplified") {}
622 /// @brief Make sure that the "strcmp" function has the right prototype
623 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
624 return F->getReturnType() == Type::Int32Ty && F->arg_size() == 2;
627 /// @brief Perform the strcmp optimization
628 virtual bool OptimizeCall(CallInst* ci, SimplifyLibCalls& SLC) {
629 // First, check to see if src and destination are the same. If they are,
630 // then the optimization is to replace the CallInst with a constant 0
631 // because the call is a no-op.
632 Value* s1 = ci->getOperand(1);
633 Value* s2 = ci->getOperand(2);
636 ci->replaceAllUsesWith(ConstantInt::get(Type::Int32Ty,0));
637 ci->eraseFromParent();
641 bool isstr_1 = false;
644 if (getConstantStringLength(s1,len_1,&A1)) {
647 // strcmp("",x) -> *x
649 new LoadInst(CastToCStr(s2,*ci), ci->getName()+".load",ci);
651 CastInst::create(Instruction::SExt, load, Type::Int32Ty,
652 ci->getName()+".int", ci);
653 ci->replaceAllUsesWith(cast);
654 ci->eraseFromParent();
659 bool isstr_2 = false;
662 if (getConstantStringLength(s2, len_2, &A2)) {
665 // strcmp(x,"") -> *x
667 new LoadInst(CastToCStr(s1,*ci),ci->getName()+".val",ci);
669 CastInst::create(Instruction::SExt, load, Type::Int32Ty,
670 ci->getName()+".int", ci);
671 ci->replaceAllUsesWith(cast);
672 ci->eraseFromParent();
677 if (isstr_1 && isstr_2) {
678 // strcmp(x,y) -> cnst (if both x and y are constant strings)
679 std::string str1 = A1->getAsString();
680 std::string str2 = A2->getAsString();
681 int result = strcmp(str1.c_str(), str2.c_str());
682 ci->replaceAllUsesWith(ConstantInt::get(Type::Int32Ty,result));
683 ci->eraseFromParent();
690 /// This LibCallOptimization will simplify a call to the strncmp library
691 /// function. It optimizes out cases where one or both arguments are constant
692 /// and the result can be determined statically.
693 /// @brief Simplify the strncmp library function.
694 struct VISIBILITY_HIDDEN StrNCmpOptimization : public LibCallOptimization {
696 StrNCmpOptimization() : LibCallOptimization("strncmp",
697 "Number of 'strncmp' calls simplified") {}
699 /// @brief Make sure that the "strncmp" function has the right prototype
700 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC){
701 if (f->getReturnType() == Type::Int32Ty && f->arg_size() == 3)
706 /// @brief Perform the strncpy optimization
707 virtual bool OptimizeCall(CallInst *ci, SimplifyLibCalls &SLC) {
708 // First, check to see if src and destination are the same. If they are,
709 // then the optimization is to replace the CallInst with a constant 0
710 // because the call is a no-op.
711 Value* s1 = ci->getOperand(1);
712 Value* s2 = ci->getOperand(2);
714 // strncmp(x,x,l) -> 0
715 ci->replaceAllUsesWith(ConstantInt::get(Type::Int32Ty,0));
716 ci->eraseFromParent();
720 // Check the length argument, if it is Constant zero then the strings are
722 uint64_t len_arg = 0;
723 bool len_arg_is_const = false;
724 if (ConstantInt* len_CI = dyn_cast<ConstantInt>(ci->getOperand(3))) {
725 len_arg_is_const = true;
726 len_arg = len_CI->getZExtValue();
728 // strncmp(x,y,0) -> 0
729 ci->replaceAllUsesWith(ConstantInt::get(Type::Int32Ty,0));
730 ci->eraseFromParent();
735 bool isstr_1 = false;
738 if (getConstantStringLength(s1, len_1, &A1)) {
741 // strncmp("",x) -> *x
742 LoadInst* load = new LoadInst(s1,ci->getName()+".load",ci);
744 CastInst::create(Instruction::SExt, load, Type::Int32Ty,
745 ci->getName()+".int", ci);
746 ci->replaceAllUsesWith(cast);
747 ci->eraseFromParent();
752 bool isstr_2 = false;
755 if (getConstantStringLength(s2,len_2,&A2)) {
758 // strncmp(x,"") -> *x
759 LoadInst* load = new LoadInst(s2,ci->getName()+".val",ci);
761 CastInst::create(Instruction::SExt, load, Type::Int32Ty,
762 ci->getName()+".int", ci);
763 ci->replaceAllUsesWith(cast);
764 ci->eraseFromParent();
769 if (isstr_1 && isstr_2 && len_arg_is_const) {
770 // strncmp(x,y,const) -> constant
771 std::string str1 = A1->getAsString();
772 std::string str2 = A2->getAsString();
773 int result = strncmp(str1.c_str(), str2.c_str(), len_arg);
774 ci->replaceAllUsesWith(ConstantInt::get(Type::Int32Ty,result));
775 ci->eraseFromParent();
782 /// This LibCallOptimization will simplify a call to the strcpy library
783 /// function. Two optimizations are possible:
784 /// (1) If src and dest are the same and not volatile, just return dest
785 /// (2) If the src is a constant then we can convert to llvm.memmove
786 /// @brief Simplify the strcpy library function.
787 struct VISIBILITY_HIDDEN StrCpyOptimization : public LibCallOptimization {
789 StrCpyOptimization() : LibCallOptimization("strcpy",
790 "Number of 'strcpy' calls simplified") {}
792 /// @brief Make sure that the "strcpy" function has the right prototype
793 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC){
794 if (f->getReturnType() == PointerType::get(Type::Int8Ty))
795 if (f->arg_size() == 2) {
796 Function::const_arg_iterator AI = f->arg_begin();
797 if (AI++->getType() == PointerType::get(Type::Int8Ty))
798 if (AI->getType() == PointerType::get(Type::Int8Ty)) {
799 // Indicate this is a suitable call type.
806 /// @brief Perform the strcpy optimization
807 virtual bool OptimizeCall(CallInst* ci, SimplifyLibCalls& SLC) {
808 // First, check to see if src and destination are the same. If they are,
809 // then the optimization is to replace the CallInst with the destination
810 // because the call is a no-op. Note that this corresponds to the
811 // degenerate strcpy(X,X) case which should have "undefined" results
812 // according to the C specification. However, it occurs sometimes and
813 // we optimize it as a no-op.
814 Value* dest = ci->getOperand(1);
815 Value* src = ci->getOperand(2);
817 ci->replaceAllUsesWith(dest);
818 ci->eraseFromParent();
822 // Get the length of the constant string referenced by the second operand,
823 // the "src" parameter. Fail the optimization if we can't get the length
824 // (note that getConstantStringLength does lots of checks to make sure this
827 if (!getConstantStringLength(ci->getOperand(2),len))
830 // If the constant string's length is zero we can optimize this by just
831 // doing a store of 0 at the first byte of the destination
833 new StoreInst(ConstantInt::get(Type::Int8Ty,0),ci->getOperand(1),ci);
834 ci->replaceAllUsesWith(dest);
835 ci->eraseFromParent();
839 // Increment the length because we actually want to memcpy the null
840 // terminator as well.
843 // We have enough information to now generate the memcpy call to
844 // do the concatenation for us.
847 ConstantInt::get(SLC.getIntPtrType(),len), // length
848 ConstantInt::get(Type::Int32Ty, 1) // alignment
850 new CallInst(SLC.get_memcpy(), vals, 4, "", ci);
852 // Finally, substitute the first operand of the strcat call for the
853 // strcat call itself since strcat returns its first operand; and,
854 // kill the strcat CallInst.
855 ci->replaceAllUsesWith(dest);
856 ci->eraseFromParent();
861 /// This LibCallOptimization will simplify a call to the strlen library
862 /// function by replacing it with a constant value if the string provided to
863 /// it is a constant array.
864 /// @brief Simplify the strlen library function.
865 struct VISIBILITY_HIDDEN StrLenOptimization : public LibCallOptimization {
866 StrLenOptimization() : LibCallOptimization("strlen",
867 "Number of 'strlen' calls simplified") {}
869 /// @brief Make sure that the "strlen" function has the right prototype
870 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC)
872 if (f->getReturnType() == SLC.getTargetData()->getIntPtrType())
873 if (f->arg_size() == 1)
874 if (Function::const_arg_iterator AI = f->arg_begin())
875 if (AI->getType() == PointerType::get(Type::Int8Ty))
880 /// @brief Perform the strlen optimization
881 virtual bool OptimizeCall(CallInst* ci, SimplifyLibCalls& SLC)
883 // Make sure we're dealing with an sbyte* here.
884 Value* str = ci->getOperand(1);
885 if (str->getType() != PointerType::get(Type::Int8Ty))
888 // Does the call to strlen have exactly one use?
890 // Is that single use a icmp operator?
891 if (ICmpInst* bop = dyn_cast<ICmpInst>(ci->use_back()))
892 // Is it compared against a constant integer?
893 if (ConstantInt* CI = dyn_cast<ConstantInt>(bop->getOperand(1)))
895 // Get the value the strlen result is compared to
896 uint64_t val = CI->getZExtValue();
898 // If its compared against length 0 with == or !=
900 (bop->getPredicate() == ICmpInst::ICMP_EQ ||
901 bop->getPredicate() == ICmpInst::ICMP_NE))
903 // strlen(x) != 0 -> *x != 0
904 // strlen(x) == 0 -> *x == 0
905 LoadInst* load = new LoadInst(str,str->getName()+".first",ci);
906 ICmpInst* rbop = new ICmpInst(bop->getPredicate(), load,
907 ConstantInt::get(Type::Int8Ty,0),
908 bop->getName()+".strlen", ci);
909 bop->replaceAllUsesWith(rbop);
910 bop->eraseFromParent();
911 ci->eraseFromParent();
916 // Get the length of the constant string operand
918 if (!getConstantStringLength(ci->getOperand(1),len))
921 // strlen("xyz") -> 3 (for example)
922 const Type *Ty = SLC.getTargetData()->getIntPtrType();
923 ci->replaceAllUsesWith(ConstantInt::get(Ty, len));
925 ci->eraseFromParent();
930 /// IsOnlyUsedInEqualsComparison - Return true if it only matters that the value
931 /// is equal or not-equal to zero.
932 static bool IsOnlyUsedInEqualsZeroComparison(Instruction *I) {
933 for (Value::use_iterator UI = I->use_begin(), E = I->use_end();
935 Instruction *User = cast<Instruction>(*UI);
936 if (ICmpInst *IC = dyn_cast<ICmpInst>(User)) {
937 if ((IC->getPredicate() == ICmpInst::ICMP_NE ||
938 IC->getPredicate() == ICmpInst::ICMP_EQ) &&
939 isa<Constant>(IC->getOperand(1)) &&
940 cast<Constant>(IC->getOperand(1))->isNullValue())
942 } else if (CastInst *CI = dyn_cast<CastInst>(User))
943 if (CI->getType() == Type::Int1Ty)
945 // Unknown instruction.
951 /// This memcmpOptimization will simplify a call to the memcmp library
953 struct VISIBILITY_HIDDEN memcmpOptimization : public LibCallOptimization {
954 /// @brief Default Constructor
956 : LibCallOptimization("memcmp", "Number of 'memcmp' calls simplified") {}
958 /// @brief Make sure that the "memcmp" function has the right prototype
959 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &TD) {
960 Function::const_arg_iterator AI = F->arg_begin();
961 if (F->arg_size() != 3 || !isa<PointerType>(AI->getType())) return false;
962 if (!isa<PointerType>((++AI)->getType())) return false;
963 if (!(++AI)->getType()->isInteger()) return false;
964 if (!F->getReturnType()->isInteger()) return false;
968 /// Because of alignment and instruction information that we don't have, we
969 /// leave the bulk of this to the code generators.
971 /// Note that we could do much more if we could force alignment on otherwise
972 /// small aligned allocas, or if we could indicate that loads have a small
974 virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &TD) {
975 Value *LHS = CI->getOperand(1), *RHS = CI->getOperand(2);
977 // If the two operands are the same, return zero.
979 // memcmp(s,s,x) -> 0
980 CI->replaceAllUsesWith(Constant::getNullValue(CI->getType()));
981 CI->eraseFromParent();
985 // Make sure we have a constant length.
986 ConstantInt *LenC = dyn_cast<ConstantInt>(CI->getOperand(3));
987 if (!LenC) return false;
988 uint64_t Len = LenC->getZExtValue();
990 // If the length is zero, this returns 0.
993 // memcmp(s1,s2,0) -> 0
994 CI->replaceAllUsesWith(Constant::getNullValue(CI->getType()));
995 CI->eraseFromParent();
998 // memcmp(S1,S2,1) -> *(ubyte*)S1 - *(ubyte*)S2
999 const Type *UCharPtr = PointerType::get(Type::Int8Ty);
1000 CastInst *Op1Cast = CastInst::create(
1001 Instruction::BitCast, LHS, UCharPtr, LHS->getName(), CI);
1002 CastInst *Op2Cast = CastInst::create(
1003 Instruction::BitCast, RHS, UCharPtr, RHS->getName(), CI);
1004 Value *S1V = new LoadInst(Op1Cast, LHS->getName()+".val", CI);
1005 Value *S2V = new LoadInst(Op2Cast, RHS->getName()+".val", CI);
1006 Value *RV = BinaryOperator::createSub(S1V, S2V, CI->getName()+".diff",CI);
1007 if (RV->getType() != CI->getType())
1008 RV = CastInst::createIntegerCast(RV, CI->getType(), false,
1010 CI->replaceAllUsesWith(RV);
1011 CI->eraseFromParent();
1015 if (IsOnlyUsedInEqualsZeroComparison(CI)) {
1016 // TODO: IF both are aligned, use a short load/compare.
1018 // memcmp(S1,S2,2) -> S1[0]-S2[0] | S1[1]-S2[1] iff only ==/!= 0 matters
1019 const Type *UCharPtr = PointerType::get(Type::Int8Ty);
1020 CastInst *Op1Cast = CastInst::create(
1021 Instruction::BitCast, LHS, UCharPtr, LHS->getName(), CI);
1022 CastInst *Op2Cast = CastInst::create(
1023 Instruction::BitCast, RHS, UCharPtr, RHS->getName(), CI);
1024 Value *S1V1 = new LoadInst(Op1Cast, LHS->getName()+".val1", CI);
1025 Value *S2V1 = new LoadInst(Op2Cast, RHS->getName()+".val1", CI);
1026 Value *D1 = BinaryOperator::createSub(S1V1, S2V1,
1027 CI->getName()+".d1", CI);
1028 Constant *One = ConstantInt::get(Type::Int32Ty, 1);
1029 Value *G1 = new GetElementPtrInst(Op1Cast, One, "next1v", CI);
1030 Value *G2 = new GetElementPtrInst(Op2Cast, One, "next2v", CI);
1031 Value *S1V2 = new LoadInst(G1, LHS->getName()+".val2", CI);
1032 Value *S2V2 = new LoadInst(G2, RHS->getName()+".val2", CI);
1033 Value *D2 = BinaryOperator::createSub(S1V2, S2V2,
1034 CI->getName()+".d1", CI);
1035 Value *Or = BinaryOperator::createOr(D1, D2, CI->getName()+".res", CI);
1036 if (Or->getType() != CI->getType())
1037 Or = CastInst::createIntegerCast(Or, CI->getType(), false /*ZExt*/,
1039 CI->replaceAllUsesWith(Or);
1040 CI->eraseFromParent();
1053 /// This LibCallOptimization will simplify a call to the memcpy library
1054 /// function by expanding it out to a single store of size 0, 1, 2, 4, or 8
1055 /// bytes depending on the length of the string and the alignment. Additional
1056 /// optimizations are possible in code generation (sequence of immediate store)
1057 /// @brief Simplify the memcpy library function.
1058 struct VISIBILITY_HIDDEN LLVMMemCpyMoveOptzn : public LibCallOptimization {
1059 LLVMMemCpyMoveOptzn(const char* fname, const char* desc)
1060 : LibCallOptimization(fname, desc) {}
1062 /// @brief Make sure that the "memcpy" function has the right prototype
1063 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& TD) {
1064 // Just make sure this has 4 arguments per LLVM spec.
1065 return (f->arg_size() == 4);
1068 /// Because of alignment and instruction information that we don't have, we
1069 /// leave the bulk of this to the code generators. The optimization here just
1070 /// deals with a few degenerate cases where the length of the string and the
1071 /// alignment match the sizes of our intrinsic types so we can do a load and
1072 /// store instead of the memcpy call.
1073 /// @brief Perform the memcpy optimization.
1074 virtual bool OptimizeCall(CallInst* ci, SimplifyLibCalls& TD) {
1075 // Make sure we have constant int values to work with
1076 ConstantInt* LEN = dyn_cast<ConstantInt>(ci->getOperand(3));
1079 ConstantInt* ALIGN = dyn_cast<ConstantInt>(ci->getOperand(4));
1083 // If the length is larger than the alignment, we can't optimize
1084 uint64_t len = LEN->getZExtValue();
1085 uint64_t alignment = ALIGN->getZExtValue();
1087 alignment = 1; // Alignment 0 is identity for alignment 1
1088 if (len > alignment)
1091 // Get the type we will cast to, based on size of the string
1092 Value* dest = ci->getOperand(1);
1093 Value* src = ci->getOperand(2);
1094 const Type* castType = 0;
1098 // memcpy(d,s,0,a) -> noop
1099 ci->eraseFromParent();
1101 case 1: castType = Type::Int8Ty; break;
1102 case 2: castType = Type::Int16Ty; break;
1103 case 4: castType = Type::Int32Ty; break;
1104 case 8: castType = Type::Int64Ty; break;
1109 // Cast source and dest to the right sized primitive and then load/store
1110 CastInst* SrcCast = CastInst::create(Instruction::BitCast,
1111 src, PointerType::get(castType), src->getName()+".cast", ci);
1112 CastInst* DestCast = CastInst::create(Instruction::BitCast,
1113 dest, PointerType::get(castType),dest->getName()+".cast", ci);
1114 LoadInst* LI = new LoadInst(SrcCast,SrcCast->getName()+".val",ci);
1115 new StoreInst(LI, DestCast, ci);
1116 ci->eraseFromParent();
1121 /// This LibCallOptimization will simplify a call to the memcpy/memmove library
1123 LLVMMemCpyMoveOptzn LLVMMemCpyOptimizer32("llvm.memcpy.i32",
1124 "Number of 'llvm.memcpy' calls simplified");
1125 LLVMMemCpyMoveOptzn LLVMMemCpyOptimizer64("llvm.memcpy.i64",
1126 "Number of 'llvm.memcpy' calls simplified");
1127 LLVMMemCpyMoveOptzn LLVMMemMoveOptimizer32("llvm.memmove.i32",
1128 "Number of 'llvm.memmove' calls simplified");
1129 LLVMMemCpyMoveOptzn LLVMMemMoveOptimizer64("llvm.memmove.i64",
1130 "Number of 'llvm.memmove' calls simplified");
1132 /// This LibCallOptimization will simplify a call to the memset library
1133 /// function by expanding it out to a single store of size 0, 1, 2, 4, or 8
1134 /// bytes depending on the length argument.
1135 struct VISIBILITY_HIDDEN LLVMMemSetOptimization : public LibCallOptimization {
1136 /// @brief Default Constructor
1137 LLVMMemSetOptimization(const char *Name) : LibCallOptimization(Name,
1138 "Number of 'llvm.memset' calls simplified") {}
1140 /// @brief Make sure that the "memset" function has the right prototype
1141 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &TD) {
1142 // Just make sure this has 3 arguments per LLVM spec.
1143 return F->arg_size() == 4;
1146 /// Because of alignment and instruction information that we don't have, we
1147 /// leave the bulk of this to the code generators. The optimization here just
1148 /// deals with a few degenerate cases where the length parameter is constant
1149 /// and the alignment matches the sizes of our intrinsic types so we can do
1150 /// store instead of the memcpy call. Other calls are transformed into the
1151 /// llvm.memset intrinsic.
1152 /// @brief Perform the memset optimization.
1153 virtual bool OptimizeCall(CallInst *ci, SimplifyLibCalls &TD) {
1154 // Make sure we have constant int values to work with
1155 ConstantInt* LEN = dyn_cast<ConstantInt>(ci->getOperand(3));
1158 ConstantInt* ALIGN = dyn_cast<ConstantInt>(ci->getOperand(4));
1162 // Extract the length and alignment
1163 uint64_t len = LEN->getZExtValue();
1164 uint64_t alignment = ALIGN->getZExtValue();
1166 // Alignment 0 is identity for alignment 1
1170 // If the length is zero, this is a no-op
1172 // memset(d,c,0,a) -> noop
1173 ci->eraseFromParent();
1177 // If the length is larger than the alignment, we can't optimize
1178 if (len > alignment)
1181 // Make sure we have a constant ubyte to work with so we can extract
1182 // the value to be filled.
1183 ConstantInt* FILL = dyn_cast<ConstantInt>(ci->getOperand(2));
1186 if (FILL->getType() != Type::Int8Ty)
1189 // memset(s,c,n) -> store s, c (for n=1,2,4,8)
1191 // Extract the fill character
1192 uint64_t fill_char = FILL->getZExtValue();
1193 uint64_t fill_value = fill_char;
1195 // Get the type we will cast to, based on size of memory area to fill, and
1196 // and the value we will store there.
1197 Value* dest = ci->getOperand(1);
1198 const Type* castType = 0;
1201 castType = Type::Int8Ty;
1204 castType = Type::Int16Ty;
1205 fill_value |= fill_char << 8;
1208 castType = Type::Int32Ty;
1209 fill_value |= fill_char << 8 | fill_char << 16 | fill_char << 24;
1212 castType = Type::Int64Ty;
1213 fill_value |= fill_char << 8 | fill_char << 16 | fill_char << 24;
1214 fill_value |= fill_char << 32 | fill_char << 40 | fill_char << 48;
1215 fill_value |= fill_char << 56;
1221 // Cast dest to the right sized primitive and then load/store
1222 CastInst* DestCast = new BitCastInst(dest, PointerType::get(castType),
1223 dest->getName()+".cast", ci);
1224 new StoreInst(ConstantInt::get(castType,fill_value),DestCast, ci);
1225 ci->eraseFromParent();
1230 LLVMMemSetOptimization MemSet32Optimizer("llvm.memset.i32");
1231 LLVMMemSetOptimization MemSet64Optimizer("llvm.memset.i64");
1234 /// This LibCallOptimization will simplify calls to the "pow" library
1235 /// function. It looks for cases where the result of pow is well known and
1236 /// substitutes the appropriate value.
1237 /// @brief Simplify the pow library function.
1238 struct VISIBILITY_HIDDEN PowOptimization : public LibCallOptimization {
1240 /// @brief Default Constructor
1241 PowOptimization() : LibCallOptimization("pow",
1242 "Number of 'pow' calls simplified") {}
1244 /// @brief Make sure that the "pow" function has the right prototype
1245 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC){
1246 // Just make sure this has 2 arguments
1247 return (f->arg_size() == 2);
1250 /// @brief Perform the pow optimization.
1251 virtual bool OptimizeCall(CallInst *ci, SimplifyLibCalls &SLC) {
1252 const Type *Ty = cast<Function>(ci->getOperand(0))->getReturnType();
1253 Value* base = ci->getOperand(1);
1254 Value* expn = ci->getOperand(2);
1255 if (ConstantFP *Op1 = dyn_cast<ConstantFP>(base)) {
1256 double Op1V = Op1->getValue();
1258 // pow(1.0,x) -> 1.0
1259 ci->replaceAllUsesWith(ConstantFP::get(Ty,1.0));
1260 ci->eraseFromParent();
1263 } else if (ConstantFP* Op2 = dyn_cast<ConstantFP>(expn)) {
1264 double Op2V = Op2->getValue();
1266 // pow(x,0.0) -> 1.0
1267 ci->replaceAllUsesWith(ConstantFP::get(Ty,1.0));
1268 ci->eraseFromParent();
1270 } else if (Op2V == 0.5) {
1271 // pow(x,0.5) -> sqrt(x)
1272 CallInst* sqrt_inst = new CallInst(SLC.get_sqrt(), base,
1273 ci->getName()+".pow",ci);
1274 ci->replaceAllUsesWith(sqrt_inst);
1275 ci->eraseFromParent();
1277 } else if (Op2V == 1.0) {
1279 ci->replaceAllUsesWith(base);
1280 ci->eraseFromParent();
1282 } else if (Op2V == -1.0) {
1283 // pow(x,-1.0) -> 1.0/x
1284 BinaryOperator* div_inst= BinaryOperator::createFDiv(
1285 ConstantFP::get(Ty,1.0), base, ci->getName()+".pow", ci);
1286 ci->replaceAllUsesWith(div_inst);
1287 ci->eraseFromParent();
1291 return false; // opt failed
1295 /// This LibCallOptimization will simplify calls to the "printf" library
1296 /// function. It looks for cases where the result of printf is not used and the
1297 /// operation can be reduced to something simpler.
1298 /// @brief Simplify the printf library function.
1299 struct VISIBILITY_HIDDEN PrintfOptimization : public LibCallOptimization {
1301 /// @brief Default Constructor
1302 PrintfOptimization() : LibCallOptimization("printf",
1303 "Number of 'printf' calls simplified") {}
1305 /// @brief Make sure that the "printf" function has the right prototype
1306 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC){
1307 // Just make sure this has at least 1 arguments
1308 return (f->arg_size() >= 1);
1311 /// @brief Perform the printf optimization.
1312 virtual bool OptimizeCall(CallInst* ci, SimplifyLibCalls& SLC) {
1313 // If the call has more than 2 operands, we can't optimize it
1314 if (ci->getNumOperands() > 3 || ci->getNumOperands() <= 2)
1317 // If the result of the printf call is used, none of these optimizations
1319 if (!ci->use_empty())
1322 // All the optimizations depend on the length of the first argument and the
1323 // fact that it is a constant string array. Check that now
1325 ConstantArray* CA = 0;
1326 if (!getConstantStringLength(ci->getOperand(1), len, &CA))
1329 if (len != 2 && len != 3)
1332 // The first character has to be a %
1333 if (ConstantInt* CI = dyn_cast<ConstantInt>(CA->getOperand(0)))
1334 if (CI->getZExtValue() != '%')
1337 // Get the second character and switch on its value
1338 ConstantInt* CI = dyn_cast<ConstantInt>(CA->getOperand(1));
1339 switch (CI->getZExtValue()) {
1343 dyn_cast<ConstantInt>(CA->getOperand(2))->getZExtValue() != '\n')
1346 // printf("%s\n",str) -> puts(str)
1347 std::vector<Value*> args;
1348 new CallInst(SLC.get_puts(), CastToCStr(ci->getOperand(2), *ci),
1350 ci->replaceAllUsesWith(ConstantInt::get(Type::Int32Ty, len));
1355 // printf("%c",c) -> putchar(c)
1359 CastInst *Char = CastInst::createSExtOrBitCast(
1360 ci->getOperand(2), Type::Int32Ty, CI->getName()+".int", ci);
1361 new CallInst(SLC.get_putchar(), Char, "", ci);
1362 ci->replaceAllUsesWith(ConstantInt::get(Type::Int32Ty, 1));
1368 ci->eraseFromParent();
1373 /// This LibCallOptimization will simplify calls to the "fprintf" library
1374 /// function. It looks for cases where the result of fprintf is not used and the
1375 /// operation can be reduced to something simpler.
1376 /// @brief Simplify the fprintf library function.
1377 struct VISIBILITY_HIDDEN FPrintFOptimization : public LibCallOptimization {
1379 /// @brief Default Constructor
1380 FPrintFOptimization() : LibCallOptimization("fprintf",
1381 "Number of 'fprintf' calls simplified") {}
1383 /// @brief Make sure that the "fprintf" function has the right prototype
1384 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC){
1385 // Just make sure this has at least 2 arguments
1386 return (f->arg_size() >= 2);
1389 /// @brief Perform the fprintf optimization.
1390 virtual bool OptimizeCall(CallInst* ci, SimplifyLibCalls& SLC) {
1391 // If the call has more than 3 operands, we can't optimize it
1392 if (ci->getNumOperands() > 4 || ci->getNumOperands() <= 2)
1395 // If the result of the fprintf call is used, none of these optimizations
1397 if (!ci->use_empty())
1400 // All the optimizations depend on the length of the second argument and the
1401 // fact that it is a constant string array. Check that now
1403 ConstantArray* CA = 0;
1404 if (!getConstantStringLength(ci->getOperand(2), len, &CA))
1407 if (ci->getNumOperands() == 3) {
1408 // Make sure there's no % in the constant array
1409 for (unsigned i = 0; i < len; ++i) {
1410 if (ConstantInt* CI = dyn_cast<ConstantInt>(CA->getOperand(i))) {
1411 // Check for the null terminator
1412 if (CI->getZExtValue() == '%')
1413 return false; // we found end of string
1419 // fprintf(file,fmt) -> fwrite(fmt,strlen(fmt),file)
1420 const Type* FILEptr_type = ci->getOperand(1)->getType();
1422 // Make sure that the fprintf() and fwrite() functions both take the
1423 // same type of char pointer.
1424 if (ci->getOperand(2)->getType() != PointerType::get(Type::Int8Ty))
1429 ConstantInt::get(SLC.getIntPtrType(),len),
1430 ConstantInt::get(SLC.getIntPtrType(),1),
1433 new CallInst(SLC.get_fwrite(FILEptr_type), args, 4, ci->getName(), ci);
1434 ci->replaceAllUsesWith(ConstantInt::get(Type::Int32Ty,len));
1435 ci->eraseFromParent();
1439 // The remaining optimizations require the format string to be length 2
1444 // The first character has to be a %
1445 if (ConstantInt* CI = dyn_cast<ConstantInt>(CA->getOperand(0)))
1446 if (CI->getZExtValue() != '%')
1449 // Get the second character and switch on its value
1450 ConstantInt* CI = dyn_cast<ConstantInt>(CA->getOperand(1));
1451 switch (CI->getZExtValue()) {
1455 ConstantArray* CA = 0;
1456 if (getConstantStringLength(ci->getOperand(3), len, &CA)) {
1457 // fprintf(file,"%s",str) -> fwrite(str,strlen(str),1,file)
1458 const Type* FILEptr_type = ci->getOperand(1)->getType();
1460 CastToCStr(ci->getOperand(3), *ci),
1461 ConstantInt::get(SLC.getIntPtrType(), len),
1462 ConstantInt::get(SLC.getIntPtrType(), 1),
1465 new CallInst(SLC.get_fwrite(FILEptr_type), args, 4,ci->getName(), ci);
1466 ci->replaceAllUsesWith(ConstantInt::get(Type::Int32Ty, len));
1468 // fprintf(file,"%s",str) -> fputs(str,file)
1469 const Type* FILEptr_type = ci->getOperand(1)->getType();
1470 new CallInst(SLC.get_fputs(FILEptr_type),
1471 CastToCStr(ci->getOperand(3), *ci),
1472 ci->getOperand(1), ci->getName(),ci);
1473 ci->replaceAllUsesWith(ConstantInt::get(Type::Int32Ty,len));
1479 // fprintf(file,"%c",c) -> fputc(c,file)
1480 const Type* FILEptr_type = ci->getOperand(1)->getType();
1481 CastInst* cast = CastInst::createSExtOrBitCast(
1482 ci->getOperand(3), Type::Int32Ty, CI->getName()+".int", ci);
1483 new CallInst(SLC.get_fputc(FILEptr_type), cast,ci->getOperand(1),"",ci);
1484 ci->replaceAllUsesWith(ConstantInt::get(Type::Int32Ty,1));
1490 ci->eraseFromParent();
1495 /// This LibCallOptimization will simplify calls to the "sprintf" library
1496 /// function. It looks for cases where the result of sprintf is not used and the
1497 /// operation can be reduced to something simpler.
1498 /// @brief Simplify the sprintf library function.
1499 struct VISIBILITY_HIDDEN SPrintFOptimization : public LibCallOptimization {
1501 /// @brief Default Constructor
1502 SPrintFOptimization() : LibCallOptimization("sprintf",
1503 "Number of 'sprintf' calls simplified") {}
1505 /// @brief Make sure that the "fprintf" function has the right prototype
1506 virtual bool ValidateCalledFunction(const Function *f, SimplifyLibCalls &SLC){
1507 // Just make sure this has at least 2 arguments
1508 return (f->getReturnType() == Type::Int32Ty && f->arg_size() >= 2);
1511 /// @brief Perform the sprintf optimization.
1512 virtual bool OptimizeCall(CallInst *ci, SimplifyLibCalls &SLC) {
1513 // If the call has more than 3 operands, we can't optimize it
1514 if (ci->getNumOperands() > 4 || ci->getNumOperands() < 3)
1517 // All the optimizations depend on the length of the second argument and the
1518 // fact that it is a constant string array. Check that now
1520 ConstantArray* CA = 0;
1521 if (!getConstantStringLength(ci->getOperand(2), len, &CA))
1524 if (ci->getNumOperands() == 3) {
1526 // If the length is 0, we just need to store a null byte
1527 new StoreInst(ConstantInt::get(Type::Int8Ty,0),ci->getOperand(1),ci);
1528 ci->replaceAllUsesWith(ConstantInt::get(Type::Int32Ty,0));
1529 ci->eraseFromParent();
1533 // Make sure there's no % in the constant array
1534 for (unsigned i = 0; i < len; ++i) {
1535 if (ConstantInt* CI = dyn_cast<ConstantInt>(CA->getOperand(i))) {
1536 // Check for the null terminator
1537 if (CI->getZExtValue() == '%')
1538 return false; // we found a %, can't optimize
1540 return false; // initializer is not constant int, can't optimize
1544 // Increment length because we want to copy the null byte too
1547 // sprintf(str,fmt) -> llvm.memcpy(str,fmt,strlen(fmt),1)
1551 ConstantInt::get(SLC.getIntPtrType(),len),
1552 ConstantInt::get(Type::Int32Ty, 1)
1554 new CallInst(SLC.get_memcpy(), args, 4, "", ci);
1555 ci->replaceAllUsesWith(ConstantInt::get(Type::Int32Ty,len));
1556 ci->eraseFromParent();
1560 // The remaining optimizations require the format string to be length 2
1565 // The first character has to be a %
1566 if (ConstantInt* CI = dyn_cast<ConstantInt>(CA->getOperand(0)))
1567 if (CI->getZExtValue() != '%')
1570 // Get the second character and switch on its value
1571 ConstantInt* CI = dyn_cast<ConstantInt>(CA->getOperand(1));
1572 switch (CI->getZExtValue()) {
1574 // sprintf(dest,"%s",str) -> llvm.memcpy(dest, str, strlen(str)+1, 1)
1575 Value *Len = new CallInst(SLC.get_strlen(),
1576 CastToCStr(ci->getOperand(3), *ci),
1577 ci->getOperand(3)->getName()+".len", ci);
1578 Value *Len1 = BinaryOperator::createAdd(Len,
1579 ConstantInt::get(Len->getType(), 1),
1580 Len->getName()+"1", ci);
1581 if (Len1->getType() != SLC.getIntPtrType())
1582 Len1 = CastInst::createIntegerCast(Len1, SLC.getIntPtrType(), false,
1583 Len1->getName(), ci);
1585 CastToCStr(ci->getOperand(1), *ci),
1586 CastToCStr(ci->getOperand(3), *ci),
1588 ConstantInt::get(Type::Int32Ty,1)
1590 new CallInst(SLC.get_memcpy(), args, 4, "", ci);
1592 // The strlen result is the unincremented number of bytes in the string.
1593 if (!ci->use_empty()) {
1594 if (Len->getType() != ci->getType())
1595 Len = CastInst::createIntegerCast(Len, ci->getType(), false,
1596 Len->getName(), ci);
1597 ci->replaceAllUsesWith(Len);
1599 ci->eraseFromParent();
1603 // sprintf(dest,"%c",chr) -> store chr, dest
1604 CastInst* cast = CastInst::createTruncOrBitCast(
1605 ci->getOperand(3), Type::Int8Ty, "char", ci);
1606 new StoreInst(cast, ci->getOperand(1), ci);
1607 GetElementPtrInst* gep = new GetElementPtrInst(ci->getOperand(1),
1608 ConstantInt::get(Type::Int32Ty,1),ci->getOperand(1)->getName()+".end",
1610 new StoreInst(ConstantInt::get(Type::Int8Ty,0),gep,ci);
1611 ci->replaceAllUsesWith(ConstantInt::get(Type::Int32Ty,1));
1612 ci->eraseFromParent();
1620 /// This LibCallOptimization will simplify calls to the "fputs" library
1621 /// function. It looks for cases where the result of fputs is not used and the
1622 /// operation can be reduced to something simpler.
1623 /// @brief Simplify the puts library function.
1624 struct VISIBILITY_HIDDEN PutsOptimization : public LibCallOptimization {
1626 /// @brief Default Constructor
1627 PutsOptimization() : LibCallOptimization("fputs",
1628 "Number of 'fputs' calls simplified") {}
1630 /// @brief Make sure that the "fputs" function has the right prototype
1631 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
1632 // Just make sure this has 2 arguments
1633 return F->arg_size() == 2;
1636 /// @brief Perform the fputs optimization.
1637 virtual bool OptimizeCall(CallInst* ci, SimplifyLibCalls& SLC) {
1638 // If the result is used, none of these optimizations work
1639 if (!ci->use_empty())
1642 // All the optimizations depend on the length of the first argument and the
1643 // fact that it is a constant string array. Check that now
1645 if (!getConstantStringLength(ci->getOperand(1), len))
1650 // fputs("",F) -> noop
1654 // fputs(s,F) -> fputc(s[0],F) (if s is constant and strlen(s) == 1)
1655 const Type* FILEptr_type = ci->getOperand(2)->getType();
1656 LoadInst* loadi = new LoadInst(ci->getOperand(1),
1657 ci->getOperand(1)->getName()+".byte",ci);
1658 CastInst* casti = new SExtInst(loadi, Type::Int32Ty,
1659 loadi->getName()+".int", ci);
1660 new CallInst(SLC.get_fputc(FILEptr_type), casti,
1661 ci->getOperand(2), "", ci);
1666 // fputs(s,F) -> fwrite(s,1,len,F) (if s is constant and strlen(s) > 1)
1667 const Type* FILEptr_type = ci->getOperand(2)->getType();
1670 ConstantInt::get(SLC.getIntPtrType(),len),
1671 ConstantInt::get(SLC.getIntPtrType(),1),
1674 new CallInst(SLC.get_fwrite(FILEptr_type), parms, 4, "", ci);
1678 ci->eraseFromParent();
1679 return true; // success
1683 /// This LibCallOptimization will simplify calls to the "isdigit" library
1684 /// function. It simply does range checks the parameter explicitly.
1685 /// @brief Simplify the isdigit library function.
1686 struct VISIBILITY_HIDDEN isdigitOptimization : public LibCallOptimization {
1688 isdigitOptimization() : LibCallOptimization("isdigit",
1689 "Number of 'isdigit' calls simplified") {}
1691 /// @brief Make sure that the "isdigit" function has the right prototype
1692 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC){
1693 // Just make sure this has 1 argument
1694 return (f->arg_size() == 1);
1697 /// @brief Perform the toascii optimization.
1698 virtual bool OptimizeCall(CallInst *ci, SimplifyLibCalls &SLC) {
1699 if (ConstantInt* CI = dyn_cast<ConstantInt>(ci->getOperand(1))) {
1700 // isdigit(c) -> 0 or 1, if 'c' is constant
1701 uint64_t val = CI->getZExtValue();
1702 if (val >= '0' && val <='9')
1703 ci->replaceAllUsesWith(ConstantInt::get(Type::Int32Ty,1));
1705 ci->replaceAllUsesWith(ConstantInt::get(Type::Int32Ty,0));
1706 ci->eraseFromParent();
1710 // isdigit(c) -> (unsigned)c - '0' <= 9
1711 CastInst* cast = CastInst::createIntegerCast(ci->getOperand(1),
1712 Type::Int32Ty, false/*ZExt*/, ci->getOperand(1)->getName()+".uint", ci);
1713 BinaryOperator* sub_inst = BinaryOperator::createSub(cast,
1714 ConstantInt::get(Type::Int32Ty,0x30),
1715 ci->getOperand(1)->getName()+".sub",ci);
1716 ICmpInst* setcond_inst = new ICmpInst(ICmpInst::ICMP_ULE,sub_inst,
1717 ConstantInt::get(Type::Int32Ty,9),
1718 ci->getOperand(1)->getName()+".cmp",ci);
1719 CastInst* c2 = new ZExtInst(setcond_inst, Type::Int32Ty,
1720 ci->getOperand(1)->getName()+".isdigit", ci);
1721 ci->replaceAllUsesWith(c2);
1722 ci->eraseFromParent();
1727 struct VISIBILITY_HIDDEN isasciiOptimization : public LibCallOptimization {
1729 isasciiOptimization()
1730 : LibCallOptimization("isascii", "Number of 'isascii' calls simplified") {}
1732 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
1733 return F->arg_size() == 1 && F->arg_begin()->getType()->isInteger() &&
1734 F->getReturnType()->isInteger();
1737 /// @brief Perform the isascii optimization.
1738 virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
1739 // isascii(c) -> (unsigned)c < 128
1740 Value *V = CI->getOperand(1);
1741 Value *Cmp = new ICmpInst(ICmpInst::ICMP_ULT, V,
1742 ConstantInt::get(V->getType(), 128),
1743 V->getName()+".isascii", CI);
1744 if (Cmp->getType() != CI->getType())
1745 Cmp = new BitCastInst(Cmp, CI->getType(), Cmp->getName(), CI);
1746 CI->replaceAllUsesWith(Cmp);
1747 CI->eraseFromParent();
1753 /// This LibCallOptimization will simplify calls to the "toascii" library
1754 /// function. It simply does the corresponding and operation to restrict the
1755 /// range of values to the ASCII character set (0-127).
1756 /// @brief Simplify the toascii library function.
1757 struct VISIBILITY_HIDDEN ToAsciiOptimization : public LibCallOptimization {
1759 /// @brief Default Constructor
1760 ToAsciiOptimization() : LibCallOptimization("toascii",
1761 "Number of 'toascii' calls simplified") {}
1763 /// @brief Make sure that the "fputs" function has the right prototype
1764 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC){
1765 // Just make sure this has 2 arguments
1766 return (f->arg_size() == 1);
1769 /// @brief Perform the toascii optimization.
1770 virtual bool OptimizeCall(CallInst *ci, SimplifyLibCalls &SLC) {
1771 // toascii(c) -> (c & 0x7f)
1772 Value* chr = ci->getOperand(1);
1773 BinaryOperator* and_inst = BinaryOperator::createAnd(chr,
1774 ConstantInt::get(chr->getType(),0x7F),ci->getName()+".toascii",ci);
1775 ci->replaceAllUsesWith(and_inst);
1776 ci->eraseFromParent();
1781 /// This LibCallOptimization will simplify calls to the "ffs" library
1782 /// calls which find the first set bit in an int, long, or long long. The
1783 /// optimization is to compute the result at compile time if the argument is
1785 /// @brief Simplify the ffs library function.
1786 struct VISIBILITY_HIDDEN FFSOptimization : public LibCallOptimization {
1788 /// @brief Subclass Constructor
1789 FFSOptimization(const char* funcName, const char* description)
1790 : LibCallOptimization(funcName, description) {}
1793 /// @brief Default Constructor
1794 FFSOptimization() : LibCallOptimization("ffs",
1795 "Number of 'ffs' calls simplified") {}
1797 /// @brief Make sure that the "ffs" function has the right prototype
1798 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
1799 // Just make sure this has 2 arguments
1800 return F->arg_size() == 1 && F->getReturnType() == Type::Int32Ty;
1803 /// @brief Perform the ffs optimization.
1804 virtual bool OptimizeCall(CallInst *TheCall, SimplifyLibCalls &SLC) {
1805 if (ConstantInt *CI = dyn_cast<ConstantInt>(TheCall->getOperand(1))) {
1806 // ffs(cnst) -> bit#
1807 // ffsl(cnst) -> bit#
1808 // ffsll(cnst) -> bit#
1809 uint64_t val = CI->getZExtValue();
1813 while ((val & 1) == 0) {
1818 TheCall->replaceAllUsesWith(ConstantInt::get(Type::Int32Ty, result));
1819 TheCall->eraseFromParent();
1823 // ffs(x) -> x == 0 ? 0 : llvm.cttz(x)+1
1824 // ffsl(x) -> x == 0 ? 0 : llvm.cttz(x)+1
1825 // ffsll(x) -> x == 0 ? 0 : llvm.cttz(x)+1
1826 const Type *ArgType = TheCall->getOperand(1)->getType();
1827 const char *CTTZName;
1828 assert(ArgType->getTypeID() == Type::IntegerTyID &&
1829 "llvm.cttz argument is not an integer?");
1830 unsigned BitWidth = cast<IntegerType>(ArgType)->getBitWidth();
1832 CTTZName = "llvm.cttz.i8";
1833 else if (BitWidth == 16)
1834 CTTZName = "llvm.cttz.i16";
1835 else if (BitWidth == 32)
1836 CTTZName = "llvm.cttz.i32";
1838 assert(BitWidth == 64 && "Unknown bitwidth");
1839 CTTZName = "llvm.cttz.i64";
1842 Constant *F = SLC.getModule()->getOrInsertFunction(CTTZName, ArgType,
1844 Value *V = CastInst::createIntegerCast(TheCall->getOperand(1), ArgType,
1845 false/*ZExt*/, "tmp", TheCall);
1846 Value *V2 = new CallInst(F, V, "tmp", TheCall);
1847 V2 = CastInst::createIntegerCast(V2, Type::Int32Ty, false/*ZExt*/,
1849 V2 = BinaryOperator::createAdd(V2, ConstantInt::get(Type::Int32Ty, 1),
1851 Value *Cond = new ICmpInst(ICmpInst::ICMP_EQ, V,
1852 Constant::getNullValue(V->getType()), "tmp",
1854 V2 = new SelectInst(Cond, ConstantInt::get(Type::Int32Ty, 0), V2,
1855 TheCall->getName(), TheCall);
1856 TheCall->replaceAllUsesWith(V2);
1857 TheCall->eraseFromParent();
1862 /// This LibCallOptimization will simplify calls to the "ffsl" library
1863 /// calls. It simply uses FFSOptimization for which the transformation is
1865 /// @brief Simplify the ffsl library function.
1866 struct VISIBILITY_HIDDEN FFSLOptimization : public FFSOptimization {
1868 /// @brief Default Constructor
1869 FFSLOptimization() : FFSOptimization("ffsl",
1870 "Number of 'ffsl' calls simplified") {}
1874 /// This LibCallOptimization will simplify calls to the "ffsll" library
1875 /// calls. It simply uses FFSOptimization for which the transformation is
1877 /// @brief Simplify the ffsl library function.
1878 struct VISIBILITY_HIDDEN FFSLLOptimization : public FFSOptimization {
1880 /// @brief Default Constructor
1881 FFSLLOptimization() : FFSOptimization("ffsll",
1882 "Number of 'ffsll' calls simplified") {}
1886 /// This optimizes unary functions that take and return doubles.
1887 struct UnaryDoubleFPOptimizer : public LibCallOptimization {
1888 UnaryDoubleFPOptimizer(const char *Fn, const char *Desc)
1889 : LibCallOptimization(Fn, Desc) {}
1891 // Make sure that this function has the right prototype
1892 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
1893 return F->arg_size() == 1 && F->arg_begin()->getType() == Type::DoubleTy &&
1894 F->getReturnType() == Type::DoubleTy;
1897 /// ShrinkFunctionToFloatVersion - If the input to this function is really a
1898 /// float, strength reduce this to a float version of the function,
1899 /// e.g. floor((double)FLT) -> (double)floorf(FLT). This can only be called
1900 /// when the target supports the destination function and where there can be
1901 /// no precision loss.
1902 static bool ShrinkFunctionToFloatVersion(CallInst *CI, SimplifyLibCalls &SLC,
1903 Constant *(SimplifyLibCalls::*FP)()){
1904 if (CastInst *Cast = dyn_cast<CastInst>(CI->getOperand(1)))
1905 if (Cast->getOperand(0)->getType() == Type::FloatTy) {
1906 Value *New = new CallInst((SLC.*FP)(), Cast->getOperand(0),
1908 New = new FPExtInst(New, Type::DoubleTy, CI->getName(), CI);
1909 CI->replaceAllUsesWith(New);
1910 CI->eraseFromParent();
1911 if (Cast->use_empty())
1912 Cast->eraseFromParent();
1920 struct VISIBILITY_HIDDEN FloorOptimization : public UnaryDoubleFPOptimizer {
1922 : UnaryDoubleFPOptimizer("floor", "Number of 'floor' calls simplified") {}
1924 virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
1926 // If this is a float argument passed in, convert to floorf.
1927 if (ShrinkFunctionToFloatVersion(CI, SLC, &SimplifyLibCalls::get_floorf))
1930 return false; // opt failed
1934 struct VISIBILITY_HIDDEN CeilOptimization : public UnaryDoubleFPOptimizer {
1936 : UnaryDoubleFPOptimizer("ceil", "Number of 'ceil' calls simplified") {}
1938 virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
1940 // If this is a float argument passed in, convert to ceilf.
1941 if (ShrinkFunctionToFloatVersion(CI, SLC, &SimplifyLibCalls::get_ceilf))
1944 return false; // opt failed
1948 struct VISIBILITY_HIDDEN RoundOptimization : public UnaryDoubleFPOptimizer {
1950 : UnaryDoubleFPOptimizer("round", "Number of 'round' calls simplified") {}
1952 virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
1954 // If this is a float argument passed in, convert to roundf.
1955 if (ShrinkFunctionToFloatVersion(CI, SLC, &SimplifyLibCalls::get_roundf))
1958 return false; // opt failed
1962 struct VISIBILITY_HIDDEN RintOptimization : public UnaryDoubleFPOptimizer {
1964 : UnaryDoubleFPOptimizer("rint", "Number of 'rint' calls simplified") {}
1966 virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
1968 // If this is a float argument passed in, convert to rintf.
1969 if (ShrinkFunctionToFloatVersion(CI, SLC, &SimplifyLibCalls::get_rintf))
1972 return false; // opt failed
1976 struct VISIBILITY_HIDDEN NearByIntOptimization : public UnaryDoubleFPOptimizer {
1977 NearByIntOptimization()
1978 : UnaryDoubleFPOptimizer("nearbyint",
1979 "Number of 'nearbyint' calls simplified") {}
1981 virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
1982 #ifdef HAVE_NEARBYINTF
1983 // If this is a float argument passed in, convert to nearbyintf.
1984 if (ShrinkFunctionToFloatVersion(CI, SLC,&SimplifyLibCalls::get_nearbyintf))
1987 return false; // opt failed
1989 } NearByIntOptimizer;
1991 /// A function to compute the length of a null-terminated constant array of
1992 /// integers. This function can't rely on the size of the constant array
1993 /// because there could be a null terminator in the middle of the array.
1994 /// We also have to bail out if we find a non-integer constant initializer
1995 /// of one of the elements or if there is no null-terminator. The logic
1996 /// below checks each of these conditions and will return true only if all
1997 /// conditions are met. In that case, the \p len parameter is set to the length
1998 /// of the null-terminated string. If false is returned, the conditions were
1999 /// not met and len is set to 0.
2000 /// @brief Get the length of a constant string (null-terminated array).
2001 static bool getConstantStringLength(Value *V, uint64_t &len, ConstantArray **CA)
2003 assert(V != 0 && "Invalid args to getConstantStringLength");
2004 len = 0; // make sure we initialize this
2006 // If the value is not a GEP instruction nor a constant expression with a
2007 // GEP instruction, then return false because ConstantArray can't occur
2009 if (GetElementPtrInst* GEPI = dyn_cast<GetElementPtrInst>(V))
2011 else if (ConstantExpr* CE = dyn_cast<ConstantExpr>(V))
2012 if (CE->getOpcode() == Instruction::GetElementPtr)
2019 // Make sure the GEP has exactly three arguments.
2020 if (GEP->getNumOperands() != 3)
2023 // Check to make sure that the first operand of the GEP is an integer and
2024 // has value 0 so that we are sure we're indexing into the initializer.
2025 if (ConstantInt* op1 = dyn_cast<ConstantInt>(GEP->getOperand(1))) {
2031 // Ensure that the second operand is a ConstantInt. If it isn't then this
2032 // GEP is wonky and we're not really sure what were referencing into and
2033 // better of not optimizing it. While we're at it, get the second index
2034 // value. We'll need this later for indexing the ConstantArray.
2035 uint64_t start_idx = 0;
2036 if (ConstantInt* CI = dyn_cast<ConstantInt>(GEP->getOperand(2)))
2037 start_idx = CI->getZExtValue();
2041 // The GEP instruction, constant or instruction, must reference a global
2042 // variable that is a constant and is initialized. The referenced constant
2043 // initializer is the array that we'll use for optimization.
2044 GlobalVariable* GV = dyn_cast<GlobalVariable>(GEP->getOperand(0));
2045 if (!GV || !GV->isConstant() || !GV->hasInitializer())
2048 // Get the initializer.
2049 Constant* INTLZR = GV->getInitializer();
2051 // Handle the ConstantAggregateZero case
2052 if (isa<ConstantAggregateZero>(INTLZR)) {
2053 // This is a degenerate case. The initializer is constant zero so the
2054 // length of the string must be zero.
2059 // Must be a Constant Array
2060 ConstantArray* A = dyn_cast<ConstantArray>(INTLZR);
2064 // Get the number of elements in the array
2065 uint64_t max_elems = A->getType()->getNumElements();
2067 // Traverse the constant array from start_idx (derived above) which is
2068 // the place the GEP refers to in the array.
2069 for (len = start_idx; len < max_elems; len++) {
2070 if (ConstantInt *CI = dyn_cast<ConstantInt>(A->getOperand(len))) {
2071 // Check for the null terminator
2073 break; // we found end of string
2075 return false; // This array isn't suitable, non-int initializer
2078 if (len >= max_elems)
2079 return false; // This array isn't null terminated
2081 // Subtract out the initial value from the length
2085 return true; // success!
2088 /// CastToCStr - Return V if it is an sbyte*, otherwise cast it to sbyte*,
2089 /// inserting the cast before IP, and return the cast.
2090 /// @brief Cast a value to a "C" string.
2091 static Value *CastToCStr(Value *V, Instruction &IP) {
2092 assert(isa<PointerType>(V->getType()) &&
2093 "Can't cast non-pointer type to C string type");
2094 const Type *SBPTy = PointerType::get(Type::Int8Ty);
2095 if (V->getType() != SBPTy)
2096 return new BitCastInst(V, SBPTy, V->getName(), &IP);
2101 // Additional cases that we need to add to this file:
2104 // * cbrt(expN(X)) -> expN(x/3)
2105 // * cbrt(sqrt(x)) -> pow(x,1/6)
2106 // * cbrt(sqrt(x)) -> pow(x,1/9)
2109 // * cos(-x) -> cos(x)
2112 // * exp(log(x)) -> x
2115 // * log(exp(x)) -> x
2116 // * log(x**y) -> y*log(x)
2117 // * log(exp(y)) -> y*log(e)
2118 // * log(exp2(y)) -> y*log(2)
2119 // * log(exp10(y)) -> y*log(10)
2120 // * log(sqrt(x)) -> 0.5*log(x)
2121 // * log(pow(x,y)) -> y*log(x)
2123 // lround, lroundf, lroundl:
2124 // * lround(cnst) -> cnst'
2127 // * memcmp(x,y,l) -> cnst
2128 // (if all arguments are constant and strlen(x) <= l and strlen(y) <= l)
2131 // * memmove(d,s,l,a) -> memcpy(d,s,l,a)
2132 // (if s is a global constant array)
2135 // * pow(exp(x),y) -> exp(x*y)
2136 // * pow(sqrt(x),y) -> pow(x,y*0.5)
2137 // * pow(pow(x,y),z)-> pow(x,y*z)
2140 // * puts("") -> fputc("\n",stdout) (how do we get "stdout"?)
2142 // round, roundf, roundl:
2143 // * round(cnst) -> cnst'
2146 // * signbit(cnst) -> cnst'
2147 // * signbit(nncst) -> 0 (if pstv is a non-negative constant)
2149 // sqrt, sqrtf, sqrtl:
2150 // * sqrt(expN(x)) -> expN(x*0.5)
2151 // * sqrt(Nroot(x)) -> pow(x,1/(2*N))
2152 // * sqrt(pow(x,y)) -> pow(|x|,y*0.5)
2155 // * stpcpy(str, "literal") ->
2156 // llvm.memcpy(str,"literal",strlen("literal")+1,1)
2158 // * strrchr(s,c) -> reverse_offset_of_in(c,s)
2159 // (if c is a constant integer and s is a constant string)
2160 // * strrchr(s1,0) -> strchr(s1,0)
2163 // * strncat(x,y,0) -> x
2164 // * strncat(x,y,0) -> x (if strlen(y) = 0)
2165 // * strncat(x,y,l) -> strcat(x,y) (if y and l are constants an l > strlen(y))
2168 // * strncpy(d,s,0) -> d
2169 // * strncpy(d,s,l) -> memcpy(d,s,l,1)
2170 // (if s and l are constants)
2173 // * strpbrk(s,a) -> offset_in_for(s,a)
2174 // (if s and a are both constant strings)
2175 // * strpbrk(s,"") -> 0
2176 // * strpbrk(s,a) -> strchr(s,a[0]) (if a is constant string of length 1)
2179 // * strspn(s,a) -> const_int (if both args are constant)
2180 // * strspn("",a) -> 0
2181 // * strspn(s,"") -> 0
2182 // * strcspn(s,a) -> const_int (if both args are constant)
2183 // * strcspn("",a) -> 0
2184 // * strcspn(s,"") -> strlen(a)
2187 // * strstr(x,x) -> x
2188 // * strstr(s1,s2) -> offset_of_s2_in(s1)
2189 // (if s1 and s2 are constant strings)
2192 // * tan(atan(x)) -> x
2194 // trunc, truncf, truncl:
2195 // * trunc(cnst) -> cnst'