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 bool ReplaceCallWith(CallInst *CI, Value *V) {
130 if (!CI->use_empty())
131 CI->replaceAllUsesWith(V);
132 CI->eraseFromParent();
136 /// @brief Called by SimplifyLibCalls to update the occurrences statistic.
139 DEBUG(++occurrences);
144 /// This class is an LLVM Pass that applies each of the LibCallOptimization
145 /// instances to all the call sites in a module, relatively efficiently. The
146 /// purpose of this pass is to provide optimizations for calls to well-known
147 /// functions with well-known semantics, such as those in the c library. The
148 /// class provides the basic infrastructure for handling runOnModule. Whenever
149 /// this pass finds a function call, it asks the appropriate optimizer to
150 /// validate the call (ValidateLibraryCall). If it is validated, then
151 /// the OptimizeCall method is also called.
152 /// @brief A ModulePass for optimizing well-known function calls.
153 class VISIBILITY_HIDDEN SimplifyLibCalls : public ModulePass {
155 static char ID; // Pass identification, replacement for typeid
156 SimplifyLibCalls() : ModulePass((intptr_t)&ID) {}
158 /// We need some target data for accurate signature details that are
159 /// target dependent. So we require target data in our AnalysisUsage.
160 /// @brief Require TargetData from AnalysisUsage.
161 virtual void getAnalysisUsage(AnalysisUsage& Info) const {
162 // Ask that the TargetData analysis be performed before us so we can use
164 Info.addRequired<TargetData>();
167 /// For this pass, process all of the function calls in the module, calling
168 /// ValidateLibraryCall and OptimizeCall as appropriate.
169 /// @brief Run all the lib call optimizations on a Module.
170 virtual bool runOnModule(Module &M) {
174 hash_map<std::string, LibCallOptimization*> OptznMap;
175 for (LibCallOptimization *Optzn = OptList; Optzn; Optzn = Optzn->getNext())
176 OptznMap[Optzn->getFunctionName()] = Optzn;
178 // The call optimizations can be recursive. That is, the optimization might
179 // generate a call to another function which can also be optimized. This way
180 // we make the LibCallOptimization instances very specific to the case they
181 // handle. It also means we need to keep running over the function calls in
182 // the module until we don't get any more optimizations possible.
183 bool found_optimization = false;
185 found_optimization = false;
186 for (Module::iterator FI = M.begin(), FE = M.end(); FI != FE; ++FI) {
187 // All the "well-known" functions are external and have external linkage
188 // because they live in a runtime library somewhere and were (probably)
189 // not compiled by LLVM. So, we only act on external functions that
190 // have external or dllimport linkage and non-empty uses.
191 if (!FI->isDeclaration() ||
192 !(FI->hasExternalLinkage() || FI->hasDLLImportLinkage()) ||
196 // Get the optimization class that pertains to this function
197 hash_map<std::string, LibCallOptimization*>::iterator OMI =
198 OptznMap.find(FI->getName());
199 if (OMI == OptznMap.end()) continue;
201 LibCallOptimization *CO = OMI->second;
203 // Make sure the called function is suitable for the optimization
204 if (!CO->ValidateCalledFunction(FI, *this))
207 // Loop over each of the uses of the function
208 for (Value::use_iterator UI = FI->use_begin(), UE = FI->use_end();
210 // If the use of the function is a call instruction
211 if (CallInst* CI = dyn_cast<CallInst>(*UI++)) {
212 // Do the optimization on the LibCallOptimization.
213 if (CO->OptimizeCall(CI, *this)) {
214 ++SimplifiedLibCalls;
215 found_optimization = result = true;
221 } while (found_optimization);
226 /// @brief Return the *current* module we're working on.
227 Module* getModule() const { return M; }
229 /// @brief Return the *current* target data for the module we're working on.
230 TargetData* getTargetData() const { return TD; }
232 /// @brief Return the size_t type -- syntactic shortcut
233 const Type* getIntPtrType() const { return TD->getIntPtrType(); }
235 /// @brief Return a Function* for the putchar libcall
236 Constant *get_putchar() {
239 M->getOrInsertFunction("putchar", Type::Int32Ty, Type::Int32Ty, NULL);
243 /// @brief Return a Function* for the puts libcall
244 Constant *get_puts() {
246 puts_func = M->getOrInsertFunction("puts", Type::Int32Ty,
247 PointerType::get(Type::Int8Ty),
252 /// @brief Return a Function* for the fputc libcall
253 Constant *get_fputc(const Type* FILEptr_type) {
255 fputc_func = M->getOrInsertFunction("fputc", Type::Int32Ty, Type::Int32Ty,
260 /// @brief Return a Function* for the fputs libcall
261 Constant *get_fputs(const Type* FILEptr_type) {
263 fputs_func = M->getOrInsertFunction("fputs", Type::Int32Ty,
264 PointerType::get(Type::Int8Ty),
269 /// @brief Return a Function* for the fwrite libcall
270 Constant *get_fwrite(const Type* FILEptr_type) {
272 fwrite_func = M->getOrInsertFunction("fwrite", TD->getIntPtrType(),
273 PointerType::get(Type::Int8Ty),
280 /// @brief Return a Function* for the sqrt libcall
281 Constant *get_sqrt() {
283 sqrt_func = M->getOrInsertFunction("sqrt", Type::DoubleTy,
284 Type::DoubleTy, NULL);
288 /// @brief Return a Function* for the strcpy libcall
289 Constant *get_strcpy() {
291 strcpy_func = M->getOrInsertFunction("strcpy",
292 PointerType::get(Type::Int8Ty),
293 PointerType::get(Type::Int8Ty),
294 PointerType::get(Type::Int8Ty),
299 /// @brief Return a Function* for the strlen libcall
300 Constant *get_strlen() {
302 strlen_func = M->getOrInsertFunction("strlen", TD->getIntPtrType(),
303 PointerType::get(Type::Int8Ty),
308 /// @brief Return a Function* for the memchr libcall
309 Constant *get_memchr() {
311 memchr_func = M->getOrInsertFunction("memchr",
312 PointerType::get(Type::Int8Ty),
313 PointerType::get(Type::Int8Ty),
314 Type::Int32Ty, TD->getIntPtrType(),
319 /// @brief Return a Function* for the memcpy libcall
320 Constant *get_memcpy() {
322 const Type *SBP = PointerType::get(Type::Int8Ty);
323 const char *N = TD->getIntPtrType() == Type::Int32Ty ?
324 "llvm.memcpy.i32" : "llvm.memcpy.i64";
325 memcpy_func = M->getOrInsertFunction(N, Type::VoidTy, SBP, SBP,
326 TD->getIntPtrType(), Type::Int32Ty,
332 Constant *getUnaryFloatFunction(const char *Name, Constant *&Cache) {
334 Cache = M->getOrInsertFunction(Name, Type::FloatTy, Type::FloatTy, NULL);
338 Constant *get_floorf() { return getUnaryFloatFunction("floorf", floorf_func);}
339 Constant *get_ceilf() { return getUnaryFloatFunction( "ceilf", ceilf_func);}
340 Constant *get_roundf() { return getUnaryFloatFunction("roundf", roundf_func);}
341 Constant *get_rintf() { return getUnaryFloatFunction( "rintf", rintf_func);}
342 Constant *get_nearbyintf() { return getUnaryFloatFunction("nearbyintf",
345 /// @brief Reset our cached data for a new Module
346 void reset(Module& mod) {
348 TD = &getAnalysis<TargetData>();
367 /// Caches for function pointers.
368 Constant *putchar_func, *puts_func;
369 Constant *fputc_func, *fputs_func, *fwrite_func;
370 Constant *memcpy_func, *memchr_func;
372 Constant *strcpy_func, *strlen_func;
373 Constant *floorf_func, *ceilf_func, *roundf_func;
374 Constant *rintf_func, *nearbyintf_func;
375 Module *M; ///< Cached Module
376 TargetData *TD; ///< Cached TargetData
379 char SimplifyLibCalls::ID = 0;
381 RegisterPass<SimplifyLibCalls>
382 X("simplify-libcalls", "Simplify well-known library calls");
384 } // anonymous namespace
386 // The only public symbol in this file which just instantiates the pass object
387 ModulePass *llvm::createSimplifyLibCallsPass() {
388 return new SimplifyLibCalls();
391 // Classes below here, in the anonymous namespace, are all subclasses of the
392 // LibCallOptimization class, each implementing all optimizations possible for a
393 // single well-known library call. Each has a static singleton instance that
394 // auto registers it into the "optlist" global above.
397 // Forward declare utility functions.
398 static bool GetConstantStringInfo(Value *V, std::string &Str);
399 static Value *CastToCStr(Value *V, Instruction *IP);
401 /// This LibCallOptimization will find instances of a call to "exit" that occurs
402 /// within the "main" function and change it to a simple "ret" instruction with
403 /// the same value passed to the exit function. When this is done, it splits the
404 /// basic block at the exit(3) call and deletes the call instruction.
405 /// @brief Replace calls to exit in main with a simple return
406 struct VISIBILITY_HIDDEN ExitInMainOptimization : public LibCallOptimization {
407 ExitInMainOptimization() : LibCallOptimization("exit",
408 "Number of 'exit' calls simplified") {}
410 // Make sure the called function looks like exit (int argument, int return
411 // type, external linkage, not varargs).
412 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
413 return F->arg_size() >= 1 && F->arg_begin()->getType()->isInteger();
416 virtual bool OptimizeCall(CallInst* ci, SimplifyLibCalls& SLC) {
417 // To be careful, we check that the call to exit is coming from "main", that
418 // main has external linkage, and the return type of main and the argument
419 // to exit have the same type.
420 Function *from = ci->getParent()->getParent();
421 if (from->hasExternalLinkage())
422 if (from->getReturnType() == ci->getOperand(1)->getType())
423 if (from->getName() == "main") {
424 // Okay, time to actually do the optimization. First, get the basic
425 // block of the call instruction
426 BasicBlock* bb = ci->getParent();
428 // Create a return instruction that we'll replace the call with.
429 // Note that the argument of the return is the argument of the call
431 new ReturnInst(ci->getOperand(1), ci);
433 // Split the block at the call instruction which places it in a new
435 bb->splitBasicBlock(ci);
437 // The block split caused a branch instruction to be inserted into
438 // the end of the original block, right after the return instruction
439 // that we put there. That's not a valid block, so delete the branch
441 bb->getInstList().pop_back();
443 // Now we can finally get rid of the call instruction which now lives
444 // in the new basic block.
445 ci->eraseFromParent();
447 // Optimization succeeded, return true.
450 // We didn't pass the criteria for this optimization so return false
453 } ExitInMainOptimizer;
455 /// This LibCallOptimization will simplify a call to the strcat library
456 /// function. The simplification is possible only if the string being
457 /// concatenated is a constant array or a constant expression that results in
458 /// a constant string. In this case we can replace it with strlen + llvm.memcpy
459 /// of the constant string. Both of these calls are further reduced, if possible
460 /// on subsequent passes.
461 /// @brief Simplify the strcat library function.
462 struct VISIBILITY_HIDDEN StrCatOptimization : public LibCallOptimization {
464 /// @brief Default constructor
465 StrCatOptimization() : LibCallOptimization("strcat",
466 "Number of 'strcat' calls simplified") {}
470 /// @brief Make sure that the "strcat" function has the right prototype
471 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
472 const FunctionType *FT = F->getFunctionType();
473 return FT->getNumParams() == 2 &&
474 FT->getReturnType() == PointerType::get(Type::Int8Ty) &&
475 FT->getParamType(0) == FT->getReturnType() &&
476 FT->getParamType(1) == FT->getReturnType();
479 /// @brief Optimize the strcat library function
480 virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
481 // Extract some information from the instruction
482 Value *Dst = CI->getOperand(1);
483 Value *Src = CI->getOperand(2);
485 // Extract the initializer (while making numerous checks) from the
486 // source operand of the call to strcat.
488 if (!GetConstantStringInfo(Src, SrcStr))
491 // Handle the simple, do-nothing case
493 return ReplaceCallWith(CI, Dst);
495 // We need to find the end of the destination string. That's where the
496 // memory is to be moved to. We just generate a call to strlen.
497 CallInst *DstLen = new CallInst(SLC.get_strlen(), Dst,
498 Dst->getName()+".len", CI);
500 // Now that we have the destination's length, we must index into the
501 // destination's pointer to get the actual memcpy destination (end of
502 // the string .. we're concatenating).
503 Dst = new GetElementPtrInst(Dst, DstLen, Dst->getName()+".indexed", CI);
505 // We have enough information to now generate the memcpy call to
506 // do the concatenation for us.
509 ConstantInt::get(SLC.getIntPtrType(), SrcStr.size()+1), // copy nul byte.
510 ConstantInt::get(Type::Int32Ty, 1) // alignment
512 new CallInst(SLC.get_memcpy(), Vals, Vals + 4, "", CI);
514 return ReplaceCallWith(CI, Dst);
518 /// This LibCallOptimization will simplify a call to the strchr library
519 /// function. It optimizes out cases where the arguments are both constant
520 /// and the result can be determined statically.
521 /// @brief Simplify the strcmp library function.
522 struct VISIBILITY_HIDDEN StrChrOptimization : public LibCallOptimization {
524 StrChrOptimization() : LibCallOptimization("strchr",
525 "Number of 'strchr' calls simplified") {}
527 /// @brief Make sure that the "strchr" function has the right prototype
528 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
529 const FunctionType *FT = F->getFunctionType();
530 return FT->getNumParams() == 2 &&
531 FT->getReturnType() == PointerType::get(Type::Int8Ty) &&
532 FT->getParamType(0) == FT->getReturnType() &&
533 isa<IntegerType>(FT->getParamType(1));
536 /// @brief Perform the strchr optimizations
537 virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
538 // Check that the first argument to strchr is a constant array of sbyte.
540 if (!GetConstantStringInfo(CI->getOperand(1), Str))
543 // If the second operand is not constant, just lower this to memchr since we
544 // know the length of the input string.
545 ConstantInt *CSI = dyn_cast<ConstantInt>(CI->getOperand(2));
550 ConstantInt::get(SLC.getIntPtrType(), Str.size()+1)
552 return ReplaceCallWith(CI, new CallInst(SLC.get_memchr(), Args, Args + 3,
556 // strchr can find the nul character.
559 // Get the character we're looking for
560 char CharValue = CSI->getSExtValue();
562 // Compute the offset
565 if (i == Str.size()) // Didn't find the char. strchr returns null.
566 return ReplaceCallWith(CI, Constant::getNullValue(CI->getType()));
567 // Did we find our match?
568 if (Str[i] == CharValue)
573 // strchr(s+n,c) -> gep(s+n+i,c)
574 // (if c is a constant integer and s is a constant string)
575 Value *Idx = ConstantInt::get(Type::Int64Ty, i);
576 Value *GEP = new GetElementPtrInst(CI->getOperand(1), Idx,
577 CI->getOperand(1)->getName() +
579 return ReplaceCallWith(CI, GEP);
583 /// This LibCallOptimization will simplify a call to the strcmp library
584 /// function. It optimizes out cases where one or both arguments are constant
585 /// and the result can be determined statically.
586 /// @brief Simplify the strcmp library function.
587 struct VISIBILITY_HIDDEN StrCmpOptimization : public LibCallOptimization {
589 StrCmpOptimization() : LibCallOptimization("strcmp",
590 "Number of 'strcmp' calls simplified") {}
592 /// @brief Make sure that the "strcmp" function has the right prototype
593 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
594 const FunctionType *FT = F->getFunctionType();
595 return FT->getReturnType() == Type::Int32Ty && FT->getNumParams() == 2 &&
596 FT->getParamType(0) == FT->getParamType(1) &&
597 FT->getParamType(0) == PointerType::get(Type::Int8Ty);
600 /// @brief Perform the strcmp optimization
601 virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
602 // First, check to see if src and destination are the same. If they are,
603 // then the optimization is to replace the CallInst with a constant 0
604 // because the call is a no-op.
605 Value *Str1P = CI->getOperand(1);
606 Value *Str2P = CI->getOperand(2);
607 if (Str1P == Str2P) // strcmp(x,x) -> 0
608 return ReplaceCallWith(CI, ConstantInt::get(CI->getType(), 0));
611 if (!GetConstantStringInfo(Str1P, Str1))
614 // strcmp("", x) -> *x
615 Value *V = new LoadInst(Str2P, CI->getName()+".load", CI);
616 V = new ZExtInst(V, CI->getType(), CI->getName()+".int", CI);
617 return ReplaceCallWith(CI, V);
621 if (!GetConstantStringInfo(Str2P, Str2))
624 // strcmp(x,"") -> *x
625 Value *V = new LoadInst(Str1P, CI->getName()+".load", CI);
626 V = new ZExtInst(V, CI->getType(), CI->getName()+".int", CI);
627 return ReplaceCallWith(CI, V);
630 // strcmp(x, y) -> cnst (if both x and y are constant strings)
631 int R = strcmp(Str1.c_str(), Str2.c_str());
632 return ReplaceCallWith(CI, ConstantInt::get(CI->getType(), R));
636 /// This LibCallOptimization will simplify a call to the strncmp library
637 /// function. It optimizes out cases where one or both arguments are constant
638 /// and the result can be determined statically.
639 /// @brief Simplify the strncmp library function.
640 struct VISIBILITY_HIDDEN StrNCmpOptimization : public LibCallOptimization {
642 StrNCmpOptimization() : LibCallOptimization("strncmp",
643 "Number of 'strncmp' calls simplified") {}
645 /// @brief Make sure that the "strncmp" function has the right prototype
646 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
647 const FunctionType *FT = F->getFunctionType();
648 return FT->getReturnType() == Type::Int32Ty && FT->getNumParams() == 3 &&
649 FT->getParamType(0) == FT->getParamType(1) &&
650 FT->getParamType(0) == PointerType::get(Type::Int8Ty) &&
651 isa<IntegerType>(FT->getParamType(2));
655 /// @brief Perform the strncmp optimization
656 virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
657 // First, check to see if src and destination are the same. If they are,
658 // then the optimization is to replace the CallInst with a constant 0
659 // because the call is a no-op.
660 Value *Str1P = CI->getOperand(1);
661 Value *Str2P = CI->getOperand(2);
662 if (Str1P == Str2P) // strncmp(x,x, n) -> 0
663 return ReplaceCallWith(CI, ConstantInt::get(CI->getType(), 0));
665 // Check the length argument, if it is Constant zero then the strings are
668 if (ConstantInt *LengthArg = dyn_cast<ConstantInt>(CI->getOperand(3)))
669 Length = LengthArg->getZExtValue();
673 if (Length == 0) // strncmp(x,y,0) -> 0
674 return ReplaceCallWith(CI, ConstantInt::get(CI->getType(), 0));
677 if (!GetConstantStringInfo(Str1P, Str1))
680 // strncmp("", x, n) -> *x
681 Value *V = new LoadInst(Str2P, CI->getName()+".load", CI);
682 V = new ZExtInst(V, CI->getType(), CI->getName()+".int", CI);
683 return ReplaceCallWith(CI, V);
687 if (!GetConstantStringInfo(Str2P, Str2))
690 // strncmp(x, "", n) -> *x
691 Value *V = new LoadInst(Str1P, CI->getName()+".load", CI);
692 V = new ZExtInst(V, CI->getType(), CI->getName()+".int", CI);
693 return ReplaceCallWith(CI, V);
696 // strncmp(x, y, n) -> cnst (if both x and y are constant strings)
697 int R = strncmp(Str1.c_str(), Str2.c_str(), Length);
698 return ReplaceCallWith(CI, ConstantInt::get(CI->getType(), R));
702 /// This LibCallOptimization will simplify a call to the strcpy library
703 /// function. Two optimizations are possible:
704 /// (1) If src and dest are the same and not volatile, just return dest
705 /// (2) If the src is a constant then we can convert to llvm.memmove
706 /// @brief Simplify the strcpy library function.
707 struct VISIBILITY_HIDDEN StrCpyOptimization : public LibCallOptimization {
709 StrCpyOptimization() : LibCallOptimization("strcpy",
710 "Number of 'strcpy' calls simplified") {}
712 /// @brief Make sure that the "strcpy" function has the right prototype
713 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
714 const FunctionType *FT = F->getFunctionType();
715 return FT->getNumParams() == 2 &&
716 FT->getParamType(0) == FT->getParamType(1) &&
717 FT->getReturnType() == FT->getParamType(0) &&
718 FT->getParamType(0) == PointerType::get(Type::Int8Ty);
721 /// @brief Perform the strcpy optimization
722 virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
723 // First, check to see if src and destination are the same. If they are,
724 // then the optimization is to replace the CallInst with the destination
725 // because the call is a no-op. Note that this corresponds to the
726 // degenerate strcpy(X,X) case which should have "undefined" results
727 // according to the C specification. However, it occurs sometimes and
728 // we optimize it as a no-op.
729 Value *Dst = CI->getOperand(1);
730 Value *Src = CI->getOperand(2);
733 return ReplaceCallWith(CI, Dst);
736 // Get the length of the constant string referenced by the Src operand.
738 if (!GetConstantStringInfo(Src, SrcStr))
741 // If the constant string's length is zero we can optimize this by just
742 // doing a store of 0 at the first byte of the destination
743 if (SrcStr.size() == 0) {
744 new StoreInst(ConstantInt::get(Type::Int8Ty, 0), Dst, CI);
745 return ReplaceCallWith(CI, Dst);
748 // We have enough information to now generate the memcpy call to
749 // do the concatenation for us.
750 Value *MemcpyOps[] = {
751 Dst, Src, // Pass length including nul byte.
752 ConstantInt::get(SLC.getIntPtrType(), SrcStr.size()+1),
753 ConstantInt::get(Type::Int32Ty, 1) // alignment
755 new CallInst(SLC.get_memcpy(), MemcpyOps, MemcpyOps + 4, "", CI);
757 return ReplaceCallWith(CI, Dst);
761 /// This LibCallOptimization will simplify a call to the strlen library
762 /// function by replacing it with a constant value if the string provided to
763 /// it is a constant array.
764 /// @brief Simplify the strlen library function.
765 struct VISIBILITY_HIDDEN StrLenOptimization : public LibCallOptimization {
766 StrLenOptimization() : LibCallOptimization("strlen",
767 "Number of 'strlen' calls simplified") {}
769 /// @brief Make sure that the "strlen" function has the right prototype
770 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
771 const FunctionType *FT = F->getFunctionType();
772 return FT->getNumParams() == 1 &&
773 FT->getParamType(0) == PointerType::get(Type::Int8Ty) &&
774 isa<IntegerType>(FT->getReturnType());
777 /// @brief Perform the strlen optimization
778 virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
779 // Make sure we're dealing with an sbyte* here.
780 Value *Src = CI->getOperand(1);
782 // Does the call to strlen have exactly one use?
783 if (CI->hasOneUse()) {
784 // Is that single use a icmp operator?
785 if (ICmpInst *Cmp = dyn_cast<ICmpInst>(CI->use_back()))
786 // Is it compared against a constant integer?
787 if (ConstantInt *Cst = dyn_cast<ConstantInt>(Cmp->getOperand(1))) {
788 // If its compared against length 0 with == or !=
789 if (Cst->getZExtValue() == 0 && Cmp->isEquality()) {
790 // strlen(x) != 0 -> *x != 0
791 // strlen(x) == 0 -> *x == 0
792 Value *V = new LoadInst(Src, Src->getName()+".first", CI);
793 V = new ICmpInst(Cmp->getPredicate(), V,
794 ConstantInt::get(Type::Int8Ty, 0),
795 Cmp->getName()+".strlen", CI);
796 Cmp->replaceAllUsesWith(V);
797 Cmp->eraseFromParent();
798 return ReplaceCallWith(CI, 0); // no uses.
803 // Get the length of the constant string operand
805 if (!GetConstantStringInfo(Src, Str))
808 // strlen("xyz") -> 3 (for example)
809 return ReplaceCallWith(CI, ConstantInt::get(CI->getType(), Str.size()));
813 /// IsOnlyUsedInEqualsComparison - Return true if it only matters that the value
814 /// is equal or not-equal to zero.
815 static bool IsOnlyUsedInEqualsZeroComparison(Instruction *I) {
816 for (Value::use_iterator UI = I->use_begin(), E = I->use_end();
818 if (ICmpInst *IC = dyn_cast<ICmpInst>(*UI))
819 if (IC->isEquality())
820 if (Constant *C = dyn_cast<Constant>(IC->getOperand(1)))
821 if (C->isNullValue())
823 // Unknown instruction.
829 /// This memcmpOptimization will simplify a call to the memcmp library
831 struct VISIBILITY_HIDDEN memcmpOptimization : public LibCallOptimization {
832 /// @brief Default Constructor
834 : LibCallOptimization("memcmp", "Number of 'memcmp' calls simplified") {}
836 /// @brief Make sure that the "memcmp" function has the right prototype
837 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &TD) {
838 Function::const_arg_iterator AI = F->arg_begin();
839 if (F->arg_size() != 3 || !isa<PointerType>(AI->getType())) return false;
840 if (!isa<PointerType>((++AI)->getType())) return false;
841 if (!(++AI)->getType()->isInteger()) return false;
842 if (!F->getReturnType()->isInteger()) return false;
846 /// Because of alignment and instruction information that we don't have, we
847 /// leave the bulk of this to the code generators.
849 /// Note that we could do much more if we could force alignment on otherwise
850 /// small aligned allocas, or if we could indicate that loads have a small
852 virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &TD) {
853 Value *LHS = CI->getOperand(1), *RHS = CI->getOperand(2);
855 // If the two operands are the same, return zero.
857 // memcmp(s,s,x) -> 0
858 return ReplaceCallWith(CI, Constant::getNullValue(CI->getType()));
861 // Make sure we have a constant length.
862 ConstantInt *LenC = dyn_cast<ConstantInt>(CI->getOperand(3));
863 if (!LenC) return false;
864 uint64_t Len = LenC->getZExtValue();
866 // If the length is zero, this returns 0.
869 // memcmp(s1,s2,0) -> 0
870 return ReplaceCallWith(CI, Constant::getNullValue(CI->getType()));
872 // memcmp(S1,S2,1) -> *(ubyte*)S1 - *(ubyte*)S2
873 const Type *UCharPtr = PointerType::get(Type::Int8Ty);
874 CastInst *Op1Cast = CastInst::create(
875 Instruction::BitCast, LHS, UCharPtr, LHS->getName(), CI);
876 CastInst *Op2Cast = CastInst::create(
877 Instruction::BitCast, RHS, UCharPtr, RHS->getName(), CI);
878 Value *S1V = new LoadInst(Op1Cast, LHS->getName()+".val", CI);
879 Value *S2V = new LoadInst(Op2Cast, RHS->getName()+".val", CI);
880 Value *RV = BinaryOperator::createSub(S1V, S2V, CI->getName()+".diff",CI);
881 if (RV->getType() != CI->getType())
882 RV = CastInst::createIntegerCast(RV, CI->getType(), false,
884 return ReplaceCallWith(CI, RV);
887 if (IsOnlyUsedInEqualsZeroComparison(CI)) {
888 // TODO: IF both are aligned, use a short load/compare.
890 // memcmp(S1,S2,2) -> S1[0]-S2[0] | S1[1]-S2[1] iff only ==/!= 0 matters
891 const Type *UCharPtr = PointerType::get(Type::Int8Ty);
892 CastInst *Op1Cast = CastInst::create(
893 Instruction::BitCast, LHS, UCharPtr, LHS->getName(), CI);
894 CastInst *Op2Cast = CastInst::create(
895 Instruction::BitCast, RHS, UCharPtr, RHS->getName(), CI);
896 Value *S1V1 = new LoadInst(Op1Cast, LHS->getName()+".val1", CI);
897 Value *S2V1 = new LoadInst(Op2Cast, RHS->getName()+".val1", CI);
898 Value *D1 = BinaryOperator::createSub(S1V1, S2V1,
899 CI->getName()+".d1", CI);
900 Constant *One = ConstantInt::get(Type::Int32Ty, 1);
901 Value *G1 = new GetElementPtrInst(Op1Cast, One, "next1v", CI);
902 Value *G2 = new GetElementPtrInst(Op2Cast, One, "next2v", CI);
903 Value *S1V2 = new LoadInst(G1, LHS->getName()+".val2", CI);
904 Value *S2V2 = new LoadInst(G2, RHS->getName()+".val2", CI);
905 Value *D2 = BinaryOperator::createSub(S1V2, S2V2,
906 CI->getName()+".d1", CI);
907 Value *Or = BinaryOperator::createOr(D1, D2, CI->getName()+".res", CI);
908 if (Or->getType() != CI->getType())
909 Or = CastInst::createIntegerCast(Or, CI->getType(), false /*ZExt*/,
911 return ReplaceCallWith(CI, Or);
923 /// This LibCallOptimization will simplify a call to the memcpy library
924 /// function by expanding it out to a single store of size 0, 1, 2, 4, or 8
925 /// bytes depending on the length of the string and the alignment. Additional
926 /// optimizations are possible in code generation (sequence of immediate store)
927 /// @brief Simplify the memcpy library function.
928 struct VISIBILITY_HIDDEN LLVMMemCpyMoveOptzn : public LibCallOptimization {
929 LLVMMemCpyMoveOptzn(const char* fname, const char* desc)
930 : LibCallOptimization(fname, desc) {}
932 /// @brief Make sure that the "memcpy" function has the right prototype
933 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& TD) {
934 // Just make sure this has 4 arguments per LLVM spec.
935 return (f->arg_size() == 4);
938 /// Because of alignment and instruction information that we don't have, we
939 /// leave the bulk of this to the code generators. The optimization here just
940 /// deals with a few degenerate cases where the length of the string and the
941 /// alignment match the sizes of our intrinsic types so we can do a load and
942 /// store instead of the memcpy call.
943 /// @brief Perform the memcpy optimization.
944 virtual bool OptimizeCall(CallInst* ci, SimplifyLibCalls& TD) {
945 // Make sure we have constant int values to work with
946 ConstantInt* LEN = dyn_cast<ConstantInt>(ci->getOperand(3));
949 ConstantInt* ALIGN = dyn_cast<ConstantInt>(ci->getOperand(4));
953 // If the length is larger than the alignment, we can't optimize
954 uint64_t len = LEN->getZExtValue();
955 uint64_t alignment = ALIGN->getZExtValue();
957 alignment = 1; // Alignment 0 is identity for alignment 1
961 // Get the type we will cast to, based on size of the string
962 Value* dest = ci->getOperand(1);
963 Value* src = ci->getOperand(2);
964 const Type* castType = 0;
967 // memcpy(d,s,0,a) -> d
968 return ReplaceCallWith(ci, 0);
969 case 1: castType = Type::Int8Ty; break;
970 case 2: castType = Type::Int16Ty; break;
971 case 4: castType = Type::Int32Ty; break;
972 case 8: castType = Type::Int64Ty; break;
977 // Cast source and dest to the right sized primitive and then load/store
978 CastInst* SrcCast = CastInst::create(Instruction::BitCast,
979 src, PointerType::get(castType), src->getName()+".cast", ci);
980 CastInst* DestCast = CastInst::create(Instruction::BitCast,
981 dest, PointerType::get(castType),dest->getName()+".cast", ci);
982 LoadInst* LI = new LoadInst(SrcCast,SrcCast->getName()+".val",ci);
983 new StoreInst(LI, DestCast, ci);
984 return ReplaceCallWith(ci, 0);
988 /// This LibCallOptimization will simplify a call to the memcpy/memmove library
990 LLVMMemCpyMoveOptzn LLVMMemCpyOptimizer32("llvm.memcpy.i32",
991 "Number of 'llvm.memcpy' calls simplified");
992 LLVMMemCpyMoveOptzn LLVMMemCpyOptimizer64("llvm.memcpy.i64",
993 "Number of 'llvm.memcpy' calls simplified");
994 LLVMMemCpyMoveOptzn LLVMMemMoveOptimizer32("llvm.memmove.i32",
995 "Number of 'llvm.memmove' calls simplified");
996 LLVMMemCpyMoveOptzn LLVMMemMoveOptimizer64("llvm.memmove.i64",
997 "Number of 'llvm.memmove' calls simplified");
999 /// This LibCallOptimization will simplify a call to the memset library
1000 /// function by expanding it out to a single store of size 0, 1, 2, 4, or 8
1001 /// bytes depending on the length argument.
1002 struct VISIBILITY_HIDDEN LLVMMemSetOptimization : public LibCallOptimization {
1003 /// @brief Default Constructor
1004 LLVMMemSetOptimization(const char *Name) : LibCallOptimization(Name,
1005 "Number of 'llvm.memset' calls simplified") {}
1007 /// @brief Make sure that the "memset" function has the right prototype
1008 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &TD) {
1009 // Just make sure this has 3 arguments per LLVM spec.
1010 return F->arg_size() == 4;
1013 /// Because of alignment and instruction information that we don't have, we
1014 /// leave the bulk of this to the code generators. The optimization here just
1015 /// deals with a few degenerate cases where the length parameter is constant
1016 /// and the alignment matches the sizes of our intrinsic types so we can do
1017 /// store instead of the memcpy call. Other calls are transformed into the
1018 /// llvm.memset intrinsic.
1019 /// @brief Perform the memset optimization.
1020 virtual bool OptimizeCall(CallInst *ci, SimplifyLibCalls &TD) {
1021 // Make sure we have constant int values to work with
1022 ConstantInt* LEN = dyn_cast<ConstantInt>(ci->getOperand(3));
1025 ConstantInt* ALIGN = dyn_cast<ConstantInt>(ci->getOperand(4));
1029 // Extract the length and alignment
1030 uint64_t len = LEN->getZExtValue();
1031 uint64_t alignment = ALIGN->getZExtValue();
1033 // Alignment 0 is identity for alignment 1
1037 // If the length is zero, this is a no-op
1039 // memset(d,c,0,a) -> noop
1040 return ReplaceCallWith(ci, 0);
1043 // If the length is larger than the alignment, we can't optimize
1044 if (len > alignment)
1047 // Make sure we have a constant ubyte to work with so we can extract
1048 // the value to be filled.
1049 ConstantInt* FILL = dyn_cast<ConstantInt>(ci->getOperand(2));
1052 if (FILL->getType() != Type::Int8Ty)
1055 // memset(s,c,n) -> store s, c (for n=1,2,4,8)
1057 // Extract the fill character
1058 uint64_t fill_char = FILL->getZExtValue();
1059 uint64_t fill_value = fill_char;
1061 // Get the type we will cast to, based on size of memory area to fill, and
1062 // and the value we will store there.
1063 Value* dest = ci->getOperand(1);
1064 const Type* castType = 0;
1067 castType = Type::Int8Ty;
1070 castType = Type::Int16Ty;
1071 fill_value |= fill_char << 8;
1074 castType = Type::Int32Ty;
1075 fill_value |= fill_char << 8 | fill_char << 16 | fill_char << 24;
1078 castType = Type::Int64Ty;
1079 fill_value |= fill_char << 8 | fill_char << 16 | fill_char << 24;
1080 fill_value |= fill_char << 32 | fill_char << 40 | fill_char << 48;
1081 fill_value |= fill_char << 56;
1087 // Cast dest to the right sized primitive and then load/store
1088 CastInst* DestCast = new BitCastInst(dest, PointerType::get(castType),
1089 dest->getName()+".cast", ci);
1090 new StoreInst(ConstantInt::get(castType,fill_value),DestCast, ci);
1091 return ReplaceCallWith(ci, 0);
1095 LLVMMemSetOptimization MemSet32Optimizer("llvm.memset.i32");
1096 LLVMMemSetOptimization MemSet64Optimizer("llvm.memset.i64");
1099 /// This LibCallOptimization will simplify calls to the "pow" library
1100 /// function. It looks for cases where the result of pow is well known and
1101 /// substitutes the appropriate value.
1102 /// @brief Simplify the pow library function.
1103 struct VISIBILITY_HIDDEN PowOptimization : public LibCallOptimization {
1105 /// @brief Default Constructor
1106 PowOptimization() : LibCallOptimization("pow",
1107 "Number of 'pow' calls simplified") {}
1109 /// @brief Make sure that the "pow" function has the right prototype
1110 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC){
1111 // Just make sure this has 2 arguments
1112 return (f->arg_size() == 2);
1115 /// @brief Perform the pow optimization.
1116 virtual bool OptimizeCall(CallInst *ci, SimplifyLibCalls &SLC) {
1117 const Type *Ty = cast<Function>(ci->getOperand(0))->getReturnType();
1118 if (Ty!=Type::FloatTy && Ty!=Type::DoubleTy)
1119 return false; // FIXME long double not yet supported
1120 Value* base = ci->getOperand(1);
1121 Value* expn = ci->getOperand(2);
1122 if (ConstantFP *Op1 = dyn_cast<ConstantFP>(base)) {
1123 if (Op1->isExactlyValue(1.0)) // pow(1.0,x) -> 1.0
1124 return ReplaceCallWith(ci, ConstantFP::get(Ty,
1125 Ty==Type::FloatTy ? APFloat(1.0f) : APFloat(1.0)));
1126 } else if (ConstantFP* Op2 = dyn_cast<ConstantFP>(expn)) {
1127 if (Op2->getValueAPF().isZero()) {
1128 // pow(x,0.0) -> 1.0
1129 return ReplaceCallWith(ci, ConstantFP::get(Ty,
1130 Ty==Type::FloatTy ? APFloat(1.0f) : APFloat(1.0)));
1131 } else if (Op2->isExactlyValue(0.5)) {
1132 // pow(x,0.5) -> sqrt(x)
1133 CallInst* sqrt_inst = new CallInst(SLC.get_sqrt(), base,
1134 ci->getName()+".pow",ci);
1135 return ReplaceCallWith(ci, sqrt_inst);
1136 } else if (Op2->isExactlyValue(1.0)) {
1138 return ReplaceCallWith(ci, base);
1139 } else if (Op2->isExactlyValue(-1.0)) {
1140 // pow(x,-1.0) -> 1.0/x
1142 BinaryOperator::createFDiv(ConstantFP::get(Ty,
1143 Ty==Type::FloatTy ? APFloat(1.0f) : APFloat(1.0)),
1144 base, ci->getName()+".pow", ci);
1145 return ReplaceCallWith(ci, div_inst);
1148 return false; // opt failed
1152 /// This LibCallOptimization will simplify calls to the "printf" library
1153 /// function. It looks for cases where the result of printf is not used and the
1154 /// operation can be reduced to something simpler.
1155 /// @brief Simplify the printf library function.
1156 struct VISIBILITY_HIDDEN PrintfOptimization : public LibCallOptimization {
1158 /// @brief Default Constructor
1159 PrintfOptimization() : LibCallOptimization("printf",
1160 "Number of 'printf' calls simplified") {}
1162 /// @brief Make sure that the "printf" function has the right prototype
1163 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
1164 // Just make sure this has at least 1 argument and returns an integer or
1166 const FunctionType *FT = F->getFunctionType();
1167 return FT->getNumParams() >= 1 &&
1168 (isa<IntegerType>(FT->getReturnType()) ||
1169 FT->getReturnType() == Type::VoidTy);
1172 /// @brief Perform the printf optimization.
1173 virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
1174 // All the optimizations depend on the length of the first argument and the
1175 // fact that it is a constant string array. Check that now
1176 std::string FormatStr;
1177 if (!GetConstantStringInfo(CI->getOperand(1), FormatStr))
1180 // If this is a simple constant string with no format specifiers that ends
1181 // with a \n, turn it into a puts call.
1182 if (FormatStr.empty()) {
1183 // Tolerate printf's declared void.
1184 if (CI->use_empty()) return ReplaceCallWith(CI, 0);
1185 return ReplaceCallWith(CI, ConstantInt::get(CI->getType(), 0));
1188 if (FormatStr.size() == 1) {
1189 // Turn this into a putchar call, even if it is a %.
1190 Value *V = ConstantInt::get(Type::Int32Ty, FormatStr[0]);
1191 new CallInst(SLC.get_putchar(), V, "", CI);
1192 if (CI->use_empty()) return ReplaceCallWith(CI, 0);
1193 return ReplaceCallWith(CI, ConstantInt::get(CI->getType(), 1));
1196 // Check to see if the format str is something like "foo\n", in which case
1197 // we convert it to a puts call. We don't allow it to contain any format
1199 if (FormatStr[FormatStr.size()-1] == '\n' &&
1200 FormatStr.find('%') == std::string::npos) {
1201 // Create a string literal with no \n on it. We expect the constant merge
1202 // pass to be run after this pass, to merge duplicate strings.
1203 FormatStr.erase(FormatStr.end()-1);
1204 Constant *Init = ConstantArray::get(FormatStr, true);
1205 Constant *GV = new GlobalVariable(Init->getType(), true,
1206 GlobalVariable::InternalLinkage,
1208 CI->getParent()->getParent()->getParent());
1209 // Cast GV to be a pointer to char.
1210 GV = ConstantExpr::getBitCast(GV, PointerType::get(Type::Int8Ty));
1211 new CallInst(SLC.get_puts(), GV, "", CI);
1213 if (CI->use_empty()) return ReplaceCallWith(CI, 0);
1214 // The return value from printf includes the \n we just removed, so +1.
1215 return ReplaceCallWith(CI,
1216 ConstantInt::get(CI->getType(),
1217 FormatStr.size()+1));
1221 // Only support %c or "%s\n" for now.
1222 if (FormatStr.size() < 2 || FormatStr[0] != '%')
1225 // Get the second character and switch on its value
1226 switch (FormatStr[1]) {
1227 default: return false;
1229 if (FormatStr != "%s\n" || CI->getNumOperands() < 3 ||
1230 // TODO: could insert strlen call to compute string length.
1234 // printf("%s\n",str) -> puts(str)
1235 new CallInst(SLC.get_puts(), CastToCStr(CI->getOperand(2), CI),
1237 return ReplaceCallWith(CI, 0);
1239 // printf("%c",c) -> putchar(c)
1240 if (FormatStr.size() != 2 || CI->getNumOperands() < 3)
1243 Value *V = CI->getOperand(2);
1244 if (!isa<IntegerType>(V->getType()) ||
1245 cast<IntegerType>(V->getType())->getBitWidth() > 32)
1248 V = CastInst::createZExtOrBitCast(V, Type::Int32Ty, CI->getName()+".int",
1250 new CallInst(SLC.get_putchar(), V, "", CI);
1251 return ReplaceCallWith(CI, ConstantInt::get(CI->getType(), 1));
1257 /// This LibCallOptimization will simplify calls to the "fprintf" library
1258 /// function. It looks for cases where the result of fprintf is not used and the
1259 /// operation can be reduced to something simpler.
1260 /// @brief Simplify the fprintf library function.
1261 struct VISIBILITY_HIDDEN FPrintFOptimization : public LibCallOptimization {
1263 /// @brief Default Constructor
1264 FPrintFOptimization() : LibCallOptimization("fprintf",
1265 "Number of 'fprintf' calls simplified") {}
1267 /// @brief Make sure that the "fprintf" function has the right prototype
1268 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
1269 const FunctionType *FT = F->getFunctionType();
1270 return FT->getNumParams() == 2 && // two fixed arguments.
1271 FT->getParamType(1) == PointerType::get(Type::Int8Ty) &&
1272 isa<PointerType>(FT->getParamType(0)) &&
1273 isa<IntegerType>(FT->getReturnType());
1276 /// @brief Perform the fprintf optimization.
1277 virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
1278 // If the call has more than 3 operands, we can't optimize it
1279 if (CI->getNumOperands() != 3 && CI->getNumOperands() != 4)
1282 // All the optimizations depend on the format string.
1283 std::string FormatStr;
1284 if (!GetConstantStringInfo(CI->getOperand(2), FormatStr))
1287 // If this is just a format string, turn it into fwrite.
1288 if (CI->getNumOperands() == 3) {
1289 for (unsigned i = 0, e = FormatStr.size(); i != e; ++i)
1290 if (FormatStr[i] == '%')
1291 return false; // we found a format specifier
1293 // fprintf(file,fmt) -> fwrite(fmt,strlen(fmt),file)
1294 const Type *FILEty = CI->getOperand(1)->getType();
1296 Value *FWriteArgs[] = {
1298 ConstantInt::get(SLC.getIntPtrType(), FormatStr.size()),
1299 ConstantInt::get(SLC.getIntPtrType(), 1),
1302 new CallInst(SLC.get_fwrite(FILEty), FWriteArgs, FWriteArgs + 4, CI->getName(), CI);
1303 return ReplaceCallWith(CI, ConstantInt::get(CI->getType(),
1307 // The remaining optimizations require the format string to be length 2:
1309 if (FormatStr.size() != 2 || FormatStr[0] != '%')
1312 // Get the second character and switch on its value
1313 switch (FormatStr[1]) {
1315 // fprintf(file,"%c",c) -> fputc(c,file)
1316 const Type *FILETy = CI->getOperand(1)->getType();
1317 Value *C = CastInst::createZExtOrBitCast(CI->getOperand(3), Type::Int32Ty,
1318 CI->getName()+".int", CI);
1319 SmallVector<Value *, 2> Args;
1321 Args.push_back(CI->getOperand(1));
1322 new CallInst(SLC.get_fputc(FILETy), Args.begin(), Args.end(), "", CI);
1323 return ReplaceCallWith(CI, ConstantInt::get(CI->getType(), 1));
1326 const Type *FILETy = CI->getOperand(1)->getType();
1328 // If the result of the fprintf call is used, we can't do this.
1329 // TODO: we should insert a strlen call.
1330 if (!CI->use_empty())
1333 // fprintf(file,"%s",str) -> fputs(str,file)
1334 SmallVector<Value *, 2> Args;
1335 Args.push_back(CastToCStr(CI->getOperand(3), CI));
1336 Args.push_back(CI->getOperand(1));
1337 new CallInst(SLC.get_fputs(FILETy), Args.begin(),
1338 Args.end(), CI->getName(), CI);
1339 return ReplaceCallWith(CI, 0);
1347 /// This LibCallOptimization will simplify calls to the "sprintf" library
1348 /// function. It looks for cases where the result of sprintf is not used and the
1349 /// operation can be reduced to something simpler.
1350 /// @brief Simplify the sprintf library function.
1351 struct VISIBILITY_HIDDEN SPrintFOptimization : public LibCallOptimization {
1353 /// @brief Default Constructor
1354 SPrintFOptimization() : LibCallOptimization("sprintf",
1355 "Number of 'sprintf' calls simplified") {}
1357 /// @brief Make sure that the "sprintf" function has the right prototype
1358 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
1359 const FunctionType *FT = F->getFunctionType();
1360 return FT->getNumParams() == 2 && // two fixed arguments.
1361 FT->getParamType(1) == PointerType::get(Type::Int8Ty) &&
1362 FT->getParamType(0) == FT->getParamType(1) &&
1363 isa<IntegerType>(FT->getReturnType());
1366 /// @brief Perform the sprintf optimization.
1367 virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
1368 // If the call has more than 3 operands, we can't optimize it
1369 if (CI->getNumOperands() != 3 && CI->getNumOperands() != 4)
1372 std::string FormatStr;
1373 if (!GetConstantStringInfo(CI->getOperand(2), FormatStr))
1376 if (CI->getNumOperands() == 3) {
1377 // Make sure there's no % in the constant array
1378 for (unsigned i = 0, e = FormatStr.size(); i != e; ++i)
1379 if (FormatStr[i] == '%')
1380 return false; // we found a format specifier
1382 // sprintf(str,fmt) -> llvm.memcpy(str,fmt,strlen(fmt),1)
1383 Value *MemCpyArgs[] = {
1384 CI->getOperand(1), CI->getOperand(2),
1385 ConstantInt::get(SLC.getIntPtrType(),
1386 FormatStr.size()+1), // Copy the nul byte.
1387 ConstantInt::get(Type::Int32Ty, 1)
1389 new CallInst(SLC.get_memcpy(), MemCpyArgs, MemCpyArgs + 4, "", CI);
1390 return ReplaceCallWith(CI, ConstantInt::get(CI->getType(),
1394 // The remaining optimizations require the format string to be "%s" or "%c".
1395 if (FormatStr.size() != 2 || FormatStr[0] != '%')
1398 // Get the second character and switch on its value
1399 switch (FormatStr[1]) {
1401 // sprintf(dest,"%c",chr) -> store chr, dest
1402 Value *V = CastInst::createTruncOrBitCast(CI->getOperand(3),
1403 Type::Int8Ty, "char", CI);
1404 new StoreInst(V, CI->getOperand(1), CI);
1405 Value *Ptr = new GetElementPtrInst(CI->getOperand(1),
1406 ConstantInt::get(Type::Int32Ty, 1),
1407 CI->getOperand(1)->getName()+".end",
1409 new StoreInst(ConstantInt::get(Type::Int8Ty,0), Ptr, CI);
1410 return ReplaceCallWith(CI, ConstantInt::get(Type::Int32Ty, 1));
1413 // sprintf(dest,"%s",str) -> llvm.memcpy(dest, str, strlen(str)+1, 1)
1414 Value *Len = new CallInst(SLC.get_strlen(),
1415 CastToCStr(CI->getOperand(3), CI),
1416 CI->getOperand(3)->getName()+".len", CI);
1417 Value *UnincLen = Len;
1418 Len = BinaryOperator::createAdd(Len, ConstantInt::get(Len->getType(), 1),
1419 Len->getName()+"1", CI);
1420 Value *MemcpyArgs[4] = {
1422 CastToCStr(CI->getOperand(3), CI),
1424 ConstantInt::get(Type::Int32Ty, 1)
1426 new CallInst(SLC.get_memcpy(), MemcpyArgs, MemcpyArgs + 4, "", CI);
1428 // The strlen result is the unincremented number of bytes in the string.
1429 if (!CI->use_empty()) {
1430 if (UnincLen->getType() != CI->getType())
1431 UnincLen = CastInst::createIntegerCast(UnincLen, CI->getType(), false,
1432 Len->getName(), CI);
1433 CI->replaceAllUsesWith(UnincLen);
1435 return ReplaceCallWith(CI, 0);
1442 /// This LibCallOptimization will simplify calls to the "fputs" library
1443 /// function. It looks for cases where the result of fputs is not used and the
1444 /// operation can be reduced to something simpler.
1445 /// @brief Simplify the fputs library function.
1446 struct VISIBILITY_HIDDEN FPutsOptimization : public LibCallOptimization {
1448 /// @brief Default Constructor
1449 FPutsOptimization() : LibCallOptimization("fputs",
1450 "Number of 'fputs' calls simplified") {}
1452 /// @brief Make sure that the "fputs" function has the right prototype
1453 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
1454 // Just make sure this has 2 arguments
1455 return F->arg_size() == 2;
1458 /// @brief Perform the fputs optimization.
1459 virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
1460 // If the result is used, none of these optimizations work.
1461 if (!CI->use_empty())
1464 // All the optimizations depend on the length of the first argument and the
1465 // fact that it is a constant string array. Check that now
1467 if (!GetConstantStringInfo(CI->getOperand(1), Str))
1470 const Type *FILETy = CI->getOperand(2)->getType();
1471 // fputs(s,F) -> fwrite(s,1,len,F) (if s is constant and strlen(s) > 1)
1472 Value *FWriteParms[4] = {
1474 ConstantInt::get(SLC.getIntPtrType(), Str.size()),
1475 ConstantInt::get(SLC.getIntPtrType(), 1),
1478 new CallInst(SLC.get_fwrite(FILETy), FWriteParms, FWriteParms + 4, "", CI);
1479 return ReplaceCallWith(CI, 0); // Known to have no uses (see above).
1483 /// This LibCallOptimization will simplify calls to the "fwrite" function.
1484 struct VISIBILITY_HIDDEN FWriteOptimization : public LibCallOptimization {
1486 /// @brief Default Constructor
1487 FWriteOptimization() : LibCallOptimization("fwrite",
1488 "Number of 'fwrite' calls simplified") {}
1490 /// @brief Make sure that the "fputs" function has the right prototype
1491 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
1492 const FunctionType *FT = F->getFunctionType();
1493 return FT->getNumParams() == 4 &&
1494 FT->getParamType(0) == PointerType::get(Type::Int8Ty) &&
1495 FT->getParamType(1) == FT->getParamType(2) &&
1496 isa<IntegerType>(FT->getParamType(1)) &&
1497 isa<PointerType>(FT->getParamType(3)) &&
1498 isa<IntegerType>(FT->getReturnType());
1501 virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
1502 // Get the element size and count.
1503 uint64_t EltSize, EltCount;
1504 if (ConstantInt *C = dyn_cast<ConstantInt>(CI->getOperand(2)))
1505 EltSize = C->getZExtValue();
1508 if (ConstantInt *C = dyn_cast<ConstantInt>(CI->getOperand(3)))
1509 EltCount = C->getZExtValue();
1513 // If this is writing zero records, remove the call (it's a noop).
1514 if (EltSize * EltCount == 0)
1515 return ReplaceCallWith(CI, ConstantInt::get(CI->getType(), 0));
1517 // If this is writing one byte, turn it into fputc.
1518 if (EltSize == 1 && EltCount == 1) {
1519 SmallVector<Value *, 2> Args;
1520 // fwrite(s,1,1,F) -> fputc(s[0],F)
1521 Value *Ptr = CI->getOperand(1);
1522 Value *Val = new LoadInst(Ptr, Ptr->getName()+".byte", CI);
1523 Args.push_back(new ZExtInst(Val, Type::Int32Ty, Val->getName()+".int", CI));
1524 Args.push_back(CI->getOperand(4));
1525 const Type *FILETy = CI->getOperand(4)->getType();
1526 new CallInst(SLC.get_fputc(FILETy), Args.begin(), Args.end(), "", CI);
1527 return ReplaceCallWith(CI, ConstantInt::get(CI->getType(), 1));
1533 /// This LibCallOptimization will simplify calls to the "isdigit" library
1534 /// function. It simply does range checks the parameter explicitly.
1535 /// @brief Simplify the isdigit library function.
1536 struct VISIBILITY_HIDDEN isdigitOptimization : public LibCallOptimization {
1538 isdigitOptimization() : LibCallOptimization("isdigit",
1539 "Number of 'isdigit' calls simplified") {}
1541 /// @brief Make sure that the "isdigit" function has the right prototype
1542 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC){
1543 // Just make sure this has 1 argument
1544 return (f->arg_size() == 1);
1547 /// @brief Perform the toascii optimization.
1548 virtual bool OptimizeCall(CallInst *ci, SimplifyLibCalls &SLC) {
1549 if (ConstantInt* CI = dyn_cast<ConstantInt>(ci->getOperand(1))) {
1550 // isdigit(c) -> 0 or 1, if 'c' is constant
1551 uint64_t val = CI->getZExtValue();
1552 if (val >= '0' && val <= '9')
1553 return ReplaceCallWith(ci, ConstantInt::get(Type::Int32Ty, 1));
1555 return ReplaceCallWith(ci, ConstantInt::get(Type::Int32Ty, 0));
1558 // isdigit(c) -> (unsigned)c - '0' <= 9
1559 CastInst* cast = CastInst::createIntegerCast(ci->getOperand(1),
1560 Type::Int32Ty, false/*ZExt*/, ci->getOperand(1)->getName()+".uint", ci);
1561 BinaryOperator* sub_inst = BinaryOperator::createSub(cast,
1562 ConstantInt::get(Type::Int32Ty,0x30),
1563 ci->getOperand(1)->getName()+".sub",ci);
1564 ICmpInst* setcond_inst = new ICmpInst(ICmpInst::ICMP_ULE,sub_inst,
1565 ConstantInt::get(Type::Int32Ty,9),
1566 ci->getOperand(1)->getName()+".cmp",ci);
1567 CastInst* c2 = new ZExtInst(setcond_inst, Type::Int32Ty,
1568 ci->getOperand(1)->getName()+".isdigit", ci);
1569 return ReplaceCallWith(ci, c2);
1573 struct VISIBILITY_HIDDEN isasciiOptimization : public LibCallOptimization {
1575 isasciiOptimization()
1576 : LibCallOptimization("isascii", "Number of 'isascii' calls simplified") {}
1578 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
1579 return F->arg_size() == 1 && F->arg_begin()->getType()->isInteger() &&
1580 F->getReturnType()->isInteger();
1583 /// @brief Perform the isascii optimization.
1584 virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
1585 // isascii(c) -> (unsigned)c < 128
1586 Value *V = CI->getOperand(1);
1587 Value *Cmp = new ICmpInst(ICmpInst::ICMP_ULT, V,
1588 ConstantInt::get(V->getType(), 128),
1589 V->getName()+".isascii", CI);
1590 if (Cmp->getType() != CI->getType())
1591 Cmp = new ZExtInst(Cmp, CI->getType(), Cmp->getName(), CI);
1592 return ReplaceCallWith(CI, Cmp);
1597 /// This LibCallOptimization will simplify calls to the "toascii" library
1598 /// function. It simply does the corresponding and operation to restrict the
1599 /// range of values to the ASCII character set (0-127).
1600 /// @brief Simplify the toascii library function.
1601 struct VISIBILITY_HIDDEN ToAsciiOptimization : public LibCallOptimization {
1603 /// @brief Default Constructor
1604 ToAsciiOptimization() : LibCallOptimization("toascii",
1605 "Number of 'toascii' calls simplified") {}
1607 /// @brief Make sure that the "fputs" function has the right prototype
1608 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC){
1609 // Just make sure this has 2 arguments
1610 return (f->arg_size() == 1);
1613 /// @brief Perform the toascii optimization.
1614 virtual bool OptimizeCall(CallInst *ci, SimplifyLibCalls &SLC) {
1615 // toascii(c) -> (c & 0x7f)
1616 Value *chr = ci->getOperand(1);
1617 Value *and_inst = BinaryOperator::createAnd(chr,
1618 ConstantInt::get(chr->getType(),0x7F),ci->getName()+".toascii",ci);
1619 return ReplaceCallWith(ci, and_inst);
1623 /// This LibCallOptimization will simplify calls to the "ffs" library
1624 /// calls which find the first set bit in an int, long, or long long. The
1625 /// optimization is to compute the result at compile time if the argument is
1627 /// @brief Simplify the ffs library function.
1628 struct VISIBILITY_HIDDEN FFSOptimization : public LibCallOptimization {
1630 /// @brief Subclass Constructor
1631 FFSOptimization(const char* funcName, const char* description)
1632 : LibCallOptimization(funcName, description) {}
1635 /// @brief Default Constructor
1636 FFSOptimization() : LibCallOptimization("ffs",
1637 "Number of 'ffs' calls simplified") {}
1639 /// @brief Make sure that the "ffs" function has the right prototype
1640 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
1641 // Just make sure this has 2 arguments
1642 return F->arg_size() == 1 && F->getReturnType() == Type::Int32Ty;
1645 /// @brief Perform the ffs optimization.
1646 virtual bool OptimizeCall(CallInst *TheCall, SimplifyLibCalls &SLC) {
1647 if (ConstantInt *CI = dyn_cast<ConstantInt>(TheCall->getOperand(1))) {
1648 // ffs(cnst) -> bit#
1649 // ffsl(cnst) -> bit#
1650 // ffsll(cnst) -> bit#
1651 uint64_t val = CI->getZExtValue();
1655 while ((val & 1) == 0) {
1660 return ReplaceCallWith(TheCall, ConstantInt::get(Type::Int32Ty, result));
1663 // ffs(x) -> x == 0 ? 0 : llvm.cttz(x)+1
1664 // ffsl(x) -> x == 0 ? 0 : llvm.cttz(x)+1
1665 // ffsll(x) -> x == 0 ? 0 : llvm.cttz(x)+1
1666 const Type *ArgType = TheCall->getOperand(1)->getType();
1667 const char *CTTZName;
1668 assert(ArgType->getTypeID() == Type::IntegerTyID &&
1669 "llvm.cttz argument is not an integer?");
1670 unsigned BitWidth = cast<IntegerType>(ArgType)->getBitWidth();
1672 CTTZName = "llvm.cttz.i8";
1673 else if (BitWidth == 16)
1674 CTTZName = "llvm.cttz.i16";
1675 else if (BitWidth == 32)
1676 CTTZName = "llvm.cttz.i32";
1678 assert(BitWidth == 64 && "Unknown bitwidth");
1679 CTTZName = "llvm.cttz.i64";
1682 Constant *F = SLC.getModule()->getOrInsertFunction(CTTZName, ArgType,
1684 Value *V = CastInst::createIntegerCast(TheCall->getOperand(1), ArgType,
1685 false/*ZExt*/, "tmp", TheCall);
1686 Value *V2 = new CallInst(F, V, "tmp", TheCall);
1687 V2 = CastInst::createIntegerCast(V2, Type::Int32Ty, false/*ZExt*/,
1689 V2 = BinaryOperator::createAdd(V2, ConstantInt::get(Type::Int32Ty, 1),
1691 Value *Cond = new ICmpInst(ICmpInst::ICMP_EQ, V,
1692 Constant::getNullValue(V->getType()), "tmp",
1694 V2 = new SelectInst(Cond, ConstantInt::get(Type::Int32Ty, 0), V2,
1695 TheCall->getName(), TheCall);
1696 return ReplaceCallWith(TheCall, V2);
1700 /// This LibCallOptimization will simplify calls to the "ffsl" library
1701 /// calls. It simply uses FFSOptimization for which the transformation is
1703 /// @brief Simplify the ffsl library function.
1704 struct VISIBILITY_HIDDEN FFSLOptimization : public FFSOptimization {
1706 /// @brief Default Constructor
1707 FFSLOptimization() : FFSOptimization("ffsl",
1708 "Number of 'ffsl' calls simplified") {}
1712 /// This LibCallOptimization will simplify calls to the "ffsll" library
1713 /// calls. It simply uses FFSOptimization for which the transformation is
1715 /// @brief Simplify the ffsl library function.
1716 struct VISIBILITY_HIDDEN FFSLLOptimization : public FFSOptimization {
1718 /// @brief Default Constructor
1719 FFSLLOptimization() : FFSOptimization("ffsll",
1720 "Number of 'ffsll' calls simplified") {}
1724 /// This optimizes unary functions that take and return doubles.
1725 struct UnaryDoubleFPOptimizer : public LibCallOptimization {
1726 UnaryDoubleFPOptimizer(const char *Fn, const char *Desc)
1727 : LibCallOptimization(Fn, Desc) {}
1729 // Make sure that this function has the right prototype
1730 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
1731 return F->arg_size() == 1 && F->arg_begin()->getType() == Type::DoubleTy &&
1732 F->getReturnType() == Type::DoubleTy;
1735 /// ShrinkFunctionToFloatVersion - If the input to this function is really a
1736 /// float, strength reduce this to a float version of the function,
1737 /// e.g. floor((double)FLT) -> (double)floorf(FLT). This can only be called
1738 /// when the target supports the destination function and where there can be
1739 /// no precision loss.
1740 static bool ShrinkFunctionToFloatVersion(CallInst *CI, SimplifyLibCalls &SLC,
1741 Constant *(SimplifyLibCalls::*FP)()){
1742 if (FPExtInst *Cast = dyn_cast<FPExtInst>(CI->getOperand(1)))
1743 if (Cast->getOperand(0)->getType() == Type::FloatTy) {
1744 Value *New = new CallInst((SLC.*FP)(), Cast->getOperand(0),
1746 New = new FPExtInst(New, Type::DoubleTy, CI->getName(), CI);
1747 CI->replaceAllUsesWith(New);
1748 CI->eraseFromParent();
1749 if (Cast->use_empty())
1750 Cast->eraseFromParent();
1758 struct VISIBILITY_HIDDEN FloorOptimization : public UnaryDoubleFPOptimizer {
1760 : UnaryDoubleFPOptimizer("floor", "Number of 'floor' calls simplified") {}
1762 virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
1764 // If this is a float argument passed in, convert to floorf.
1765 if (ShrinkFunctionToFloatVersion(CI, SLC, &SimplifyLibCalls::get_floorf))
1768 return false; // opt failed
1772 struct VISIBILITY_HIDDEN CeilOptimization : public UnaryDoubleFPOptimizer {
1774 : UnaryDoubleFPOptimizer("ceil", "Number of 'ceil' calls simplified") {}
1776 virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
1778 // If this is a float argument passed in, convert to ceilf.
1779 if (ShrinkFunctionToFloatVersion(CI, SLC, &SimplifyLibCalls::get_ceilf))
1782 return false; // opt failed
1786 struct VISIBILITY_HIDDEN RoundOptimization : public UnaryDoubleFPOptimizer {
1788 : UnaryDoubleFPOptimizer("round", "Number of 'round' calls simplified") {}
1790 virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
1792 // If this is a float argument passed in, convert to roundf.
1793 if (ShrinkFunctionToFloatVersion(CI, SLC, &SimplifyLibCalls::get_roundf))
1796 return false; // opt failed
1800 struct VISIBILITY_HIDDEN RintOptimization : public UnaryDoubleFPOptimizer {
1802 : UnaryDoubleFPOptimizer("rint", "Number of 'rint' calls simplified") {}
1804 virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
1806 // If this is a float argument passed in, convert to rintf.
1807 if (ShrinkFunctionToFloatVersion(CI, SLC, &SimplifyLibCalls::get_rintf))
1810 return false; // opt failed
1814 struct VISIBILITY_HIDDEN NearByIntOptimization : public UnaryDoubleFPOptimizer {
1815 NearByIntOptimization()
1816 : UnaryDoubleFPOptimizer("nearbyint",
1817 "Number of 'nearbyint' calls simplified") {}
1819 virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
1820 #ifdef HAVE_NEARBYINTF
1821 // If this is a float argument passed in, convert to nearbyintf.
1822 if (ShrinkFunctionToFloatVersion(CI, SLC,&SimplifyLibCalls::get_nearbyintf))
1825 return false; // opt failed
1827 } NearByIntOptimizer;
1829 /// GetConstantStringInfo - This function computes the length of a
1830 /// null-terminated constant array of integers. This function can't rely on the
1831 /// size of the constant array because there could be a null terminator in the
1832 /// middle of the array.
1834 /// We also have to bail out if we find a non-integer constant initializer
1835 /// of one of the elements or if there is no null-terminator. The logic
1836 /// below checks each of these conditions and will return true only if all
1837 /// conditions are met. If the conditions aren't met, this returns false.
1839 /// If successful, the \p Array param is set to the constant array being
1840 /// indexed, the \p Length parameter is set to the length of the null-terminated
1841 /// string pointed to by V, the \p StartIdx value is set to the first
1842 /// element of the Array that V points to, and true is returned.
1843 static bool GetConstantStringInfo(Value *V, std::string &Str) {
1844 // Look through noop bitcast instructions.
1845 if (BitCastInst *BCI = dyn_cast<BitCastInst>(V)) {
1846 if (BCI->getType() == BCI->getOperand(0)->getType())
1847 return GetConstantStringInfo(BCI->getOperand(0), Str);
1851 // If the value is not a GEP instruction nor a constant expression with a
1852 // GEP instruction, then return false because ConstantArray can't occur
1855 if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(V)) {
1857 } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) {
1858 if (CE->getOpcode() != Instruction::GetElementPtr)
1865 // Make sure the GEP has exactly three arguments.
1866 if (GEP->getNumOperands() != 3)
1869 // Check to make sure that the first operand of the GEP is an integer and
1870 // has value 0 so that we are sure we're indexing into the initializer.
1871 if (ConstantInt *Idx = dyn_cast<ConstantInt>(GEP->getOperand(1))) {
1877 // If the second index isn't a ConstantInt, then this is a variable index
1878 // into the array. If this occurs, we can't say anything meaningful about
1880 uint64_t StartIdx = 0;
1881 if (ConstantInt *CI = dyn_cast<ConstantInt>(GEP->getOperand(2)))
1882 StartIdx = CI->getZExtValue();
1886 // The GEP instruction, constant or instruction, must reference a global
1887 // variable that is a constant and is initialized. The referenced constant
1888 // initializer is the array that we'll use for optimization.
1889 GlobalVariable* GV = dyn_cast<GlobalVariable>(GEP->getOperand(0));
1890 if (!GV || !GV->isConstant() || !GV->hasInitializer())
1892 Constant *GlobalInit = GV->getInitializer();
1894 // Handle the ConstantAggregateZero case
1895 if (isa<ConstantAggregateZero>(GlobalInit)) {
1896 // This is a degenerate case. The initializer is constant zero so the
1897 // length of the string must be zero.
1902 // Must be a Constant Array
1903 ConstantArray *Array = dyn_cast<ConstantArray>(GlobalInit);
1904 if (!Array) return false;
1906 // Get the number of elements in the array
1907 uint64_t NumElts = Array->getType()->getNumElements();
1909 // Traverse the constant array from StartIdx (derived above) which is
1910 // the place the GEP refers to in the array.
1911 for (unsigned i = StartIdx; i < NumElts; ++i) {
1912 Constant *Elt = Array->getOperand(i);
1913 ConstantInt *CI = dyn_cast<ConstantInt>(Elt);
1914 if (!CI) // This array isn't suitable, non-int initializer.
1917 return true; // we found end of string, success!
1918 Str += (char)CI->getZExtValue();
1921 return false; // The array isn't null terminated.
1924 /// CastToCStr - Return V if it is an sbyte*, otherwise cast it to sbyte*,
1925 /// inserting the cast before IP, and return the cast.
1926 /// @brief Cast a value to a "C" string.
1927 static Value *CastToCStr(Value *V, Instruction *IP) {
1928 assert(isa<PointerType>(V->getType()) &&
1929 "Can't cast non-pointer type to C string type");
1930 const Type *SBPTy = PointerType::get(Type::Int8Ty);
1931 if (V->getType() != SBPTy)
1932 return new BitCastInst(V, SBPTy, V->getName(), IP);
1937 // Additional cases that we need to add to this file:
1940 // * cbrt(expN(X)) -> expN(x/3)
1941 // * cbrt(sqrt(x)) -> pow(x,1/6)
1942 // * cbrt(sqrt(x)) -> pow(x,1/9)
1945 // * cos(-x) -> cos(x)
1948 // * exp(log(x)) -> x
1951 // * log(exp(x)) -> x
1952 // * log(x**y) -> y*log(x)
1953 // * log(exp(y)) -> y*log(e)
1954 // * log(exp2(y)) -> y*log(2)
1955 // * log(exp10(y)) -> y*log(10)
1956 // * log(sqrt(x)) -> 0.5*log(x)
1957 // * log(pow(x,y)) -> y*log(x)
1959 // lround, lroundf, lroundl:
1960 // * lround(cnst) -> cnst'
1963 // * memcmp(x,y,l) -> cnst
1964 // (if all arguments are constant and strlen(x) <= l and strlen(y) <= l)
1967 // * memmove(d,s,l,a) -> memcpy(d,s,l,a)
1968 // (if s is a global constant array)
1971 // * pow(exp(x),y) -> exp(x*y)
1972 // * pow(sqrt(x),y) -> pow(x,y*0.5)
1973 // * pow(pow(x,y),z)-> pow(x,y*z)
1976 // * puts("") -> putchar("\n")
1978 // round, roundf, roundl:
1979 // * round(cnst) -> cnst'
1982 // * signbit(cnst) -> cnst'
1983 // * signbit(nncst) -> 0 (if pstv is a non-negative constant)
1985 // sqrt, sqrtf, sqrtl:
1986 // * sqrt(expN(x)) -> expN(x*0.5)
1987 // * sqrt(Nroot(x)) -> pow(x,1/(2*N))
1988 // * sqrt(pow(x,y)) -> pow(|x|,y*0.5)
1991 // * stpcpy(str, "literal") ->
1992 // llvm.memcpy(str,"literal",strlen("literal")+1,1)
1994 // * strrchr(s,c) -> reverse_offset_of_in(c,s)
1995 // (if c is a constant integer and s is a constant string)
1996 // * strrchr(s1,0) -> strchr(s1,0)
1999 // * strncat(x,y,0) -> x
2000 // * strncat(x,y,0) -> x (if strlen(y) = 0)
2001 // * strncat(x,y,l) -> strcat(x,y) (if y and l are constants an l > strlen(y))
2004 // * strncpy(d,s,0) -> d
2005 // * strncpy(d,s,l) -> memcpy(d,s,l,1)
2006 // (if s and l are constants)
2009 // * strpbrk(s,a) -> offset_in_for(s,a)
2010 // (if s and a are both constant strings)
2011 // * strpbrk(s,"") -> 0
2012 // * strpbrk(s,a) -> strchr(s,a[0]) (if a is constant string of length 1)
2015 // * strspn(s,a) -> const_int (if both args are constant)
2016 // * strspn("",a) -> 0
2017 // * strspn(s,"") -> 0
2018 // * strcspn(s,a) -> const_int (if both args are constant)
2019 // * strcspn("",a) -> 0
2020 // * strcspn(s,"") -> strlen(a)
2023 // * strstr(x,x) -> x
2024 // * strstr(s1,s2) -> offset_of_s2_in(s1)
2025 // (if s1 and s2 are constant strings)
2028 // * tan(atan(x)) -> x
2030 // trunc, truncf, truncl:
2031 // * trunc(cnst) -> cnst'