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 /// We need some target data for accurate signature details that are
156 /// target dependent. So we require target data in our AnalysisUsage.
157 /// @brief Require TargetData from AnalysisUsage.
158 virtual void getAnalysisUsage(AnalysisUsage& Info) const {
159 // Ask that the TargetData analysis be performed before us so we can use
161 Info.addRequired<TargetData>();
164 /// For this pass, process all of the function calls in the module, calling
165 /// ValidateLibraryCall and OptimizeCall as appropriate.
166 /// @brief Run all the lib call optimizations on a Module.
167 virtual bool runOnModule(Module &M) {
171 hash_map<std::string, LibCallOptimization*> OptznMap;
172 for (LibCallOptimization *Optzn = OptList; Optzn; Optzn = Optzn->getNext())
173 OptznMap[Optzn->getFunctionName()] = Optzn;
175 // The call optimizations can be recursive. That is, the optimization might
176 // generate a call to another function which can also be optimized. This way
177 // we make the LibCallOptimization instances very specific to the case they
178 // handle. It also means we need to keep running over the function calls in
179 // the module until we don't get any more optimizations possible.
180 bool found_optimization = false;
182 found_optimization = false;
183 for (Module::iterator FI = M.begin(), FE = M.end(); FI != FE; ++FI) {
184 // All the "well-known" functions are external and have external linkage
185 // because they live in a runtime library somewhere and were (probably)
186 // not compiled by LLVM. So, we only act on external functions that
187 // have external or dllimport linkage and non-empty uses.
188 if (!FI->isDeclaration() ||
189 !(FI->hasExternalLinkage() || FI->hasDLLImportLinkage()) ||
193 // Get the optimization class that pertains to this function
194 hash_map<std::string, LibCallOptimization*>::iterator OMI =
195 OptznMap.find(FI->getName());
196 if (OMI == OptznMap.end()) continue;
198 LibCallOptimization *CO = OMI->second;
200 // Make sure the called function is suitable for the optimization
201 if (!CO->ValidateCalledFunction(FI, *this))
204 // Loop over each of the uses of the function
205 for (Value::use_iterator UI = FI->use_begin(), UE = FI->use_end();
207 // If the use of the function is a call instruction
208 if (CallInst* CI = dyn_cast<CallInst>(*UI++)) {
209 // Do the optimization on the LibCallOptimization.
210 if (CO->OptimizeCall(CI, *this)) {
211 ++SimplifiedLibCalls;
212 found_optimization = result = true;
218 } while (found_optimization);
223 /// @brief Return the *current* module we're working on.
224 Module* getModule() const { return M; }
226 /// @brief Return the *current* target data for the module we're working on.
227 TargetData* getTargetData() const { return TD; }
229 /// @brief Return the size_t type -- syntactic shortcut
230 const Type* getIntPtrType() const { return TD->getIntPtrType(); }
232 /// @brief Return a Function* for the putchar libcall
233 Constant *get_putchar() {
236 M->getOrInsertFunction("putchar", Type::Int32Ty, Type::Int32Ty, NULL);
240 /// @brief Return a Function* for the puts libcall
241 Constant *get_puts() {
243 puts_func = M->getOrInsertFunction("puts", Type::Int32Ty,
244 PointerType::get(Type::Int8Ty),
249 /// @brief Return a Function* for the fputc libcall
250 Constant *get_fputc(const Type* FILEptr_type) {
252 fputc_func = M->getOrInsertFunction("fputc", Type::Int32Ty, Type::Int32Ty,
257 /// @brief Return a Function* for the fputs libcall
258 Constant *get_fputs(const Type* FILEptr_type) {
260 fputs_func = M->getOrInsertFunction("fputs", Type::Int32Ty,
261 PointerType::get(Type::Int8Ty),
266 /// @brief Return a Function* for the fwrite libcall
267 Constant *get_fwrite(const Type* FILEptr_type) {
269 fwrite_func = M->getOrInsertFunction("fwrite", TD->getIntPtrType(),
270 PointerType::get(Type::Int8Ty),
277 /// @brief Return a Function* for the sqrt libcall
278 Constant *get_sqrt() {
280 sqrt_func = M->getOrInsertFunction("sqrt", Type::DoubleTy,
281 Type::DoubleTy, NULL);
285 /// @brief Return a Function* for the strcpy libcall
286 Constant *get_strcpy() {
288 strcpy_func = M->getOrInsertFunction("strcpy",
289 PointerType::get(Type::Int8Ty),
290 PointerType::get(Type::Int8Ty),
291 PointerType::get(Type::Int8Ty),
296 /// @brief Return a Function* for the strlen libcall
297 Constant *get_strlen() {
299 strlen_func = M->getOrInsertFunction("strlen", TD->getIntPtrType(),
300 PointerType::get(Type::Int8Ty),
305 /// @brief Return a Function* for the memchr libcall
306 Constant *get_memchr() {
308 memchr_func = M->getOrInsertFunction("memchr",
309 PointerType::get(Type::Int8Ty),
310 PointerType::get(Type::Int8Ty),
311 Type::Int32Ty, TD->getIntPtrType(),
316 /// @brief Return a Function* for the memcpy libcall
317 Constant *get_memcpy() {
319 const Type *SBP = PointerType::get(Type::Int8Ty);
320 const char *N = TD->getIntPtrType() == Type::Int32Ty ?
321 "llvm.memcpy.i32" : "llvm.memcpy.i64";
322 memcpy_func = M->getOrInsertFunction(N, Type::VoidTy, SBP, SBP,
323 TD->getIntPtrType(), Type::Int32Ty,
329 Constant *getUnaryFloatFunction(const char *Name, Constant *&Cache) {
331 Cache = M->getOrInsertFunction(Name, Type::FloatTy, Type::FloatTy, NULL);
335 Constant *get_floorf() { return getUnaryFloatFunction("floorf", floorf_func);}
336 Constant *get_ceilf() { return getUnaryFloatFunction( "ceilf", ceilf_func);}
337 Constant *get_roundf() { return getUnaryFloatFunction("roundf", roundf_func);}
338 Constant *get_rintf() { return getUnaryFloatFunction( "rintf", rintf_func);}
339 Constant *get_nearbyintf() { return getUnaryFloatFunction("nearbyintf",
342 /// @brief Reset our cached data for a new Module
343 void reset(Module& mod) {
345 TD = &getAnalysis<TargetData>();
364 /// Caches for function pointers.
365 Constant *putchar_func, *puts_func;
366 Constant *fputc_func, *fputs_func, *fwrite_func;
367 Constant *memcpy_func, *memchr_func;
369 Constant *strcpy_func, *strlen_func;
370 Constant *floorf_func, *ceilf_func, *roundf_func;
371 Constant *rintf_func, *nearbyintf_func;
372 Module *M; ///< Cached Module
373 TargetData *TD; ///< Cached TargetData
377 RegisterPass<SimplifyLibCalls>
378 X("simplify-libcalls", "Simplify well-known library calls");
380 } // anonymous namespace
382 // The only public symbol in this file which just instantiates the pass object
383 ModulePass *llvm::createSimplifyLibCallsPass() {
384 return new SimplifyLibCalls();
387 // Classes below here, in the anonymous namespace, are all subclasses of the
388 // LibCallOptimization class, each implementing all optimizations possible for a
389 // single well-known library call. Each has a static singleton instance that
390 // auto registers it into the "optlist" global above.
393 // Forward declare utility functions.
394 static bool GetConstantStringInfo(Value *V, std::string &Str);
395 static Value *CastToCStr(Value *V, Instruction *IP);
397 /// This LibCallOptimization will find instances of a call to "exit" that occurs
398 /// within the "main" function and change it to a simple "ret" instruction with
399 /// the same value passed to the exit function. When this is done, it splits the
400 /// basic block at the exit(3) call and deletes the call instruction.
401 /// @brief Replace calls to exit in main with a simple return
402 struct VISIBILITY_HIDDEN ExitInMainOptimization : public LibCallOptimization {
403 ExitInMainOptimization() : LibCallOptimization("exit",
404 "Number of 'exit' calls simplified") {}
406 // Make sure the called function looks like exit (int argument, int return
407 // type, external linkage, not varargs).
408 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
409 return F->arg_size() >= 1 && F->arg_begin()->getType()->isInteger();
412 virtual bool OptimizeCall(CallInst* ci, SimplifyLibCalls& SLC) {
413 // To be careful, we check that the call to exit is coming from "main", that
414 // main has external linkage, and the return type of main and the argument
415 // to exit have the same type.
416 Function *from = ci->getParent()->getParent();
417 if (from->hasExternalLinkage())
418 if (from->getReturnType() == ci->getOperand(1)->getType())
419 if (from->getName() == "main") {
420 // Okay, time to actually do the optimization. First, get the basic
421 // block of the call instruction
422 BasicBlock* bb = ci->getParent();
424 // Create a return instruction that we'll replace the call with.
425 // Note that the argument of the return is the argument of the call
427 new ReturnInst(ci->getOperand(1), ci);
429 // Split the block at the call instruction which places it in a new
431 bb->splitBasicBlock(ci);
433 // The block split caused a branch instruction to be inserted into
434 // the end of the original block, right after the return instruction
435 // that we put there. That's not a valid block, so delete the branch
437 bb->getInstList().pop_back();
439 // Now we can finally get rid of the call instruction which now lives
440 // in the new basic block.
441 ci->eraseFromParent();
443 // Optimization succeeded, return true.
446 // We didn't pass the criteria for this optimization so return false
449 } ExitInMainOptimizer;
451 /// This LibCallOptimization will simplify a call to the strcat library
452 /// function. The simplification is possible only if the string being
453 /// concatenated is a constant array or a constant expression that results in
454 /// a constant string. In this case we can replace it with strlen + llvm.memcpy
455 /// of the constant string. Both of these calls are further reduced, if possible
456 /// on subsequent passes.
457 /// @brief Simplify the strcat library function.
458 struct VISIBILITY_HIDDEN StrCatOptimization : public LibCallOptimization {
460 /// @brief Default constructor
461 StrCatOptimization() : LibCallOptimization("strcat",
462 "Number of 'strcat' calls simplified") {}
466 /// @brief Make sure that the "strcat" function has the right prototype
467 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
468 const FunctionType *FT = F->getFunctionType();
469 return FT->getNumParams() == 2 &&
470 FT->getReturnType() == PointerType::get(Type::Int8Ty) &&
471 FT->getParamType(0) == FT->getReturnType() &&
472 FT->getParamType(1) == FT->getReturnType();
475 /// @brief Optimize the strcat library function
476 virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
477 // Extract some information from the instruction
478 Value *Dst = CI->getOperand(1);
479 Value *Src = CI->getOperand(2);
481 // Extract the initializer (while making numerous checks) from the
482 // source operand of the call to strcat.
484 if (!GetConstantStringInfo(Src, SrcStr))
487 // Handle the simple, do-nothing case
489 return ReplaceCallWith(CI, Dst);
491 // We need to find the end of the destination string. That's where the
492 // memory is to be moved to. We just generate a call to strlen.
493 CallInst *DstLen = new CallInst(SLC.get_strlen(), Dst,
494 Dst->getName()+".len", CI);
496 // Now that we have the destination's length, we must index into the
497 // destination's pointer to get the actual memcpy destination (end of
498 // the string .. we're concatenating).
499 Dst = new GetElementPtrInst(Dst, DstLen, Dst->getName()+".indexed", CI);
501 // We have enough information to now generate the memcpy call to
502 // do the concatenation for us.
505 ConstantInt::get(SLC.getIntPtrType(), SrcStr.size()+1), // copy nul byte.
506 ConstantInt::get(Type::Int32Ty, 1) // alignment
508 new CallInst(SLC.get_memcpy(), Vals, 4, "", CI);
510 return ReplaceCallWith(CI, Dst);
514 /// This LibCallOptimization will simplify a call to the strchr library
515 /// function. It optimizes out cases where the arguments are both constant
516 /// and the result can be determined statically.
517 /// @brief Simplify the strcmp library function.
518 struct VISIBILITY_HIDDEN StrChrOptimization : public LibCallOptimization {
520 StrChrOptimization() : LibCallOptimization("strchr",
521 "Number of 'strchr' calls simplified") {}
523 /// @brief Make sure that the "strchr" function has the right prototype
524 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
525 const FunctionType *FT = F->getFunctionType();
526 return FT->getNumParams() == 2 &&
527 FT->getReturnType() == PointerType::get(Type::Int8Ty) &&
528 FT->getParamType(0) == FT->getReturnType() &&
529 isa<IntegerType>(FT->getParamType(1));
532 /// @brief Perform the strchr optimizations
533 virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
534 // Check that the first argument to strchr is a constant array of sbyte.
536 if (!GetConstantStringInfo(CI->getOperand(1), Str))
539 // If the second operand is not constant, just lower this to memchr since we
540 // know the length of the input string.
541 ConstantInt *CSI = dyn_cast<ConstantInt>(CI->getOperand(2));
546 ConstantInt::get(SLC.getIntPtrType(), Str.size()+1)
548 return ReplaceCallWith(CI, new CallInst(SLC.get_memchr(), Args, 3,
552 // strchr can find the nul character.
555 // Get the character we're looking for
556 char CharValue = CSI->getSExtValue();
558 // Compute the offset
561 if (i == Str.size()) // Didn't find the char. strchr returns null.
562 return ReplaceCallWith(CI, Constant::getNullValue(CI->getType()));
563 // Did we find our match?
564 if (Str[i] == CharValue)
569 // strchr(s+n,c) -> gep(s+n+i,c)
570 // (if c is a constant integer and s is a constant string)
571 Value *Idx = ConstantInt::get(Type::Int64Ty, i);
572 Value *GEP = new GetElementPtrInst(CI->getOperand(1), Idx,
573 CI->getOperand(1)->getName() +
575 return ReplaceCallWith(CI, GEP);
579 /// This LibCallOptimization will simplify a call to the strcmp library
580 /// function. It optimizes out cases where one or both arguments are constant
581 /// and the result can be determined statically.
582 /// @brief Simplify the strcmp library function.
583 struct VISIBILITY_HIDDEN StrCmpOptimization : public LibCallOptimization {
585 StrCmpOptimization() : LibCallOptimization("strcmp",
586 "Number of 'strcmp' calls simplified") {}
588 /// @brief Make sure that the "strcmp" function has the right prototype
589 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
590 const FunctionType *FT = F->getFunctionType();
591 return FT->getReturnType() == Type::Int32Ty && FT->getNumParams() == 2 &&
592 FT->getParamType(0) == FT->getParamType(1) &&
593 FT->getParamType(0) == PointerType::get(Type::Int8Ty);
596 /// @brief Perform the strcmp optimization
597 virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
598 // First, check to see if src and destination are the same. If they are,
599 // then the optimization is to replace the CallInst with a constant 0
600 // because the call is a no-op.
601 Value *Str1P = CI->getOperand(1);
602 Value *Str2P = CI->getOperand(2);
603 if (Str1P == Str2P) // strcmp(x,x) -> 0
604 return ReplaceCallWith(CI, ConstantInt::get(CI->getType(), 0));
607 if (!GetConstantStringInfo(Str1P, Str1))
610 // strcmp("", x) -> *x
611 Value *V = new LoadInst(Str2P, CI->getName()+".load", CI);
612 V = new ZExtInst(V, CI->getType(), CI->getName()+".int", CI);
613 return ReplaceCallWith(CI, V);
617 if (!GetConstantStringInfo(Str2P, Str2))
620 // strcmp(x,"") -> *x
621 Value *V = new LoadInst(Str1P, CI->getName()+".load", CI);
622 V = new ZExtInst(V, CI->getType(), CI->getName()+".int", CI);
623 return ReplaceCallWith(CI, V);
626 // strcmp(x, y) -> cnst (if both x and y are constant strings)
627 int R = strcmp(Str1.c_str(), Str2.c_str());
628 return ReplaceCallWith(CI, ConstantInt::get(CI->getType(), R));
632 /// This LibCallOptimization will simplify a call to the strncmp library
633 /// function. It optimizes out cases where one or both arguments are constant
634 /// and the result can be determined statically.
635 /// @brief Simplify the strncmp library function.
636 struct VISIBILITY_HIDDEN StrNCmpOptimization : public LibCallOptimization {
638 StrNCmpOptimization() : LibCallOptimization("strncmp",
639 "Number of 'strncmp' calls simplified") {}
641 /// @brief Make sure that the "strncmp" function has the right prototype
642 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
643 const FunctionType *FT = F->getFunctionType();
644 return FT->getReturnType() == Type::Int32Ty && FT->getNumParams() == 3 &&
645 FT->getParamType(0) == FT->getParamType(1) &&
646 FT->getParamType(0) == PointerType::get(Type::Int8Ty) &&
647 isa<IntegerType>(FT->getParamType(2));
651 /// @brief Perform the strncmp optimization
652 virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
653 // First, check to see if src and destination are the same. If they are,
654 // then the optimization is to replace the CallInst with a constant 0
655 // because the call is a no-op.
656 Value *Str1P = CI->getOperand(1);
657 Value *Str2P = CI->getOperand(2);
658 if (Str1P == Str2P) // strncmp(x,x, n) -> 0
659 return ReplaceCallWith(CI, ConstantInt::get(CI->getType(), 0));
661 // Check the length argument, if it is Constant zero then the strings are
664 if (ConstantInt *LengthArg = dyn_cast<ConstantInt>(CI->getOperand(3)))
665 Length = LengthArg->getZExtValue();
669 if (Length == 0) // strncmp(x,y,0) -> 0
670 return ReplaceCallWith(CI, ConstantInt::get(CI->getType(), 0));
673 if (!GetConstantStringInfo(Str1P, Str1))
676 // strncmp("", x, n) -> *x
677 Value *V = new LoadInst(Str2P, CI->getName()+".load", CI);
678 V = new ZExtInst(V, CI->getType(), CI->getName()+".int", CI);
679 return ReplaceCallWith(CI, V);
683 if (!GetConstantStringInfo(Str2P, Str2))
686 // strncmp(x, "", n) -> *x
687 Value *V = new LoadInst(Str1P, CI->getName()+".load", CI);
688 V = new ZExtInst(V, CI->getType(), CI->getName()+".int", CI);
689 return ReplaceCallWith(CI, V);
692 // strncmp(x, y, n) -> cnst (if both x and y are constant strings)
693 int R = strncmp(Str1.c_str(), Str2.c_str(), Length);
694 return ReplaceCallWith(CI, ConstantInt::get(CI->getType(), R));
698 /// This LibCallOptimization will simplify a call to the strcpy library
699 /// function. Two optimizations are possible:
700 /// (1) If src and dest are the same and not volatile, just return dest
701 /// (2) If the src is a constant then we can convert to llvm.memmove
702 /// @brief Simplify the strcpy library function.
703 struct VISIBILITY_HIDDEN StrCpyOptimization : public LibCallOptimization {
705 StrCpyOptimization() : LibCallOptimization("strcpy",
706 "Number of 'strcpy' calls simplified") {}
708 /// @brief Make sure that the "strcpy" function has the right prototype
709 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
710 const FunctionType *FT = F->getFunctionType();
711 return FT->getNumParams() == 2 &&
712 FT->getParamType(0) == FT->getParamType(1) &&
713 FT->getReturnType() == FT->getParamType(0) &&
714 FT->getParamType(0) == PointerType::get(Type::Int8Ty);
717 /// @brief Perform the strcpy optimization
718 virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
719 // First, check to see if src and destination are the same. If they are,
720 // then the optimization is to replace the CallInst with the destination
721 // because the call is a no-op. Note that this corresponds to the
722 // degenerate strcpy(X,X) case which should have "undefined" results
723 // according to the C specification. However, it occurs sometimes and
724 // we optimize it as a no-op.
725 Value *Dst = CI->getOperand(1);
726 Value *Src = CI->getOperand(2);
729 return ReplaceCallWith(CI, Dst);
732 // Get the length of the constant string referenced by the Src operand.
734 if (!GetConstantStringInfo(Src, SrcStr))
737 // If the constant string's length is zero we can optimize this by just
738 // doing a store of 0 at the first byte of the destination
739 if (SrcStr.size() == 0) {
740 new StoreInst(ConstantInt::get(Type::Int8Ty, 0), Dst, CI);
741 return ReplaceCallWith(CI, Dst);
744 // We have enough information to now generate the memcpy call to
745 // do the concatenation for us.
746 Value *MemcpyOps[] = {
747 Dst, Src, // Pass length including nul byte.
748 ConstantInt::get(SLC.getIntPtrType(), SrcStr.size()+1),
749 ConstantInt::get(Type::Int32Ty, 1) // alignment
751 new CallInst(SLC.get_memcpy(), MemcpyOps, 4, "", CI);
753 return ReplaceCallWith(CI, Dst);
757 /// This LibCallOptimization will simplify a call to the strlen library
758 /// function by replacing it with a constant value if the string provided to
759 /// it is a constant array.
760 /// @brief Simplify the strlen library function.
761 struct VISIBILITY_HIDDEN StrLenOptimization : public LibCallOptimization {
762 StrLenOptimization() : LibCallOptimization("strlen",
763 "Number of 'strlen' calls simplified") {}
765 /// @brief Make sure that the "strlen" function has the right prototype
766 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
767 const FunctionType *FT = F->getFunctionType();
768 return FT->getNumParams() == 1 &&
769 FT->getParamType(0) == PointerType::get(Type::Int8Ty) &&
770 isa<IntegerType>(FT->getReturnType());
773 /// @brief Perform the strlen optimization
774 virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
775 // Make sure we're dealing with an sbyte* here.
776 Value *Src = CI->getOperand(1);
778 // Does the call to strlen have exactly one use?
779 if (CI->hasOneUse()) {
780 // Is that single use a icmp operator?
781 if (ICmpInst *Cmp = dyn_cast<ICmpInst>(CI->use_back()))
782 // Is it compared against a constant integer?
783 if (ConstantInt *Cst = dyn_cast<ConstantInt>(Cmp->getOperand(1))) {
784 // If its compared against length 0 with == or !=
785 if (Cst->getZExtValue() == 0 && Cmp->isEquality()) {
786 // strlen(x) != 0 -> *x != 0
787 // strlen(x) == 0 -> *x == 0
788 Value *V = new LoadInst(Src, Src->getName()+".first", CI);
789 V = new ICmpInst(Cmp->getPredicate(), V,
790 ConstantInt::get(Type::Int8Ty, 0),
791 Cmp->getName()+".strlen", CI);
792 Cmp->replaceAllUsesWith(V);
793 Cmp->eraseFromParent();
794 return ReplaceCallWith(CI, 0); // no uses.
799 // Get the length of the constant string operand
801 if (!GetConstantStringInfo(Src, Str))
804 // strlen("xyz") -> 3 (for example)
805 return ReplaceCallWith(CI, ConstantInt::get(CI->getType(), Str.size()));
809 /// IsOnlyUsedInEqualsComparison - Return true if it only matters that the value
810 /// is equal or not-equal to zero.
811 static bool IsOnlyUsedInEqualsZeroComparison(Instruction *I) {
812 for (Value::use_iterator UI = I->use_begin(), E = I->use_end();
814 if (ICmpInst *IC = dyn_cast<ICmpInst>(*UI))
815 if (IC->isEquality())
816 if (Constant *C = dyn_cast<Constant>(IC->getOperand(1)))
817 if (C->isNullValue())
819 // Unknown instruction.
825 /// This memcmpOptimization will simplify a call to the memcmp library
827 struct VISIBILITY_HIDDEN memcmpOptimization : public LibCallOptimization {
828 /// @brief Default Constructor
830 : LibCallOptimization("memcmp", "Number of 'memcmp' calls simplified") {}
832 /// @brief Make sure that the "memcmp" function has the right prototype
833 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &TD) {
834 Function::const_arg_iterator AI = F->arg_begin();
835 if (F->arg_size() != 3 || !isa<PointerType>(AI->getType())) return false;
836 if (!isa<PointerType>((++AI)->getType())) return false;
837 if (!(++AI)->getType()->isInteger()) return false;
838 if (!F->getReturnType()->isInteger()) return false;
842 /// Because of alignment and instruction information that we don't have, we
843 /// leave the bulk of this to the code generators.
845 /// Note that we could do much more if we could force alignment on otherwise
846 /// small aligned allocas, or if we could indicate that loads have a small
848 virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &TD) {
849 Value *LHS = CI->getOperand(1), *RHS = CI->getOperand(2);
851 // If the two operands are the same, return zero.
853 // memcmp(s,s,x) -> 0
854 return ReplaceCallWith(CI, Constant::getNullValue(CI->getType()));
857 // Make sure we have a constant length.
858 ConstantInt *LenC = dyn_cast<ConstantInt>(CI->getOperand(3));
859 if (!LenC) return false;
860 uint64_t Len = LenC->getZExtValue();
862 // If the length is zero, this returns 0.
865 // memcmp(s1,s2,0) -> 0
866 return ReplaceCallWith(CI, Constant::getNullValue(CI->getType()));
868 // memcmp(S1,S2,1) -> *(ubyte*)S1 - *(ubyte*)S2
869 const Type *UCharPtr = PointerType::get(Type::Int8Ty);
870 CastInst *Op1Cast = CastInst::create(
871 Instruction::BitCast, LHS, UCharPtr, LHS->getName(), CI);
872 CastInst *Op2Cast = CastInst::create(
873 Instruction::BitCast, RHS, UCharPtr, RHS->getName(), CI);
874 Value *S1V = new LoadInst(Op1Cast, LHS->getName()+".val", CI);
875 Value *S2V = new LoadInst(Op2Cast, RHS->getName()+".val", CI);
876 Value *RV = BinaryOperator::createSub(S1V, S2V, CI->getName()+".diff",CI);
877 if (RV->getType() != CI->getType())
878 RV = CastInst::createIntegerCast(RV, CI->getType(), false,
880 return ReplaceCallWith(CI, RV);
883 if (IsOnlyUsedInEqualsZeroComparison(CI)) {
884 // TODO: IF both are aligned, use a short load/compare.
886 // memcmp(S1,S2,2) -> S1[0]-S2[0] | S1[1]-S2[1] iff only ==/!= 0 matters
887 const Type *UCharPtr = PointerType::get(Type::Int8Ty);
888 CastInst *Op1Cast = CastInst::create(
889 Instruction::BitCast, LHS, UCharPtr, LHS->getName(), CI);
890 CastInst *Op2Cast = CastInst::create(
891 Instruction::BitCast, RHS, UCharPtr, RHS->getName(), CI);
892 Value *S1V1 = new LoadInst(Op1Cast, LHS->getName()+".val1", CI);
893 Value *S2V1 = new LoadInst(Op2Cast, RHS->getName()+".val1", CI);
894 Value *D1 = BinaryOperator::createSub(S1V1, S2V1,
895 CI->getName()+".d1", CI);
896 Constant *One = ConstantInt::get(Type::Int32Ty, 1);
897 Value *G1 = new GetElementPtrInst(Op1Cast, One, "next1v", CI);
898 Value *G2 = new GetElementPtrInst(Op2Cast, One, "next2v", CI);
899 Value *S1V2 = new LoadInst(G1, LHS->getName()+".val2", CI);
900 Value *S2V2 = new LoadInst(G2, RHS->getName()+".val2", CI);
901 Value *D2 = BinaryOperator::createSub(S1V2, S2V2,
902 CI->getName()+".d1", CI);
903 Value *Or = BinaryOperator::createOr(D1, D2, CI->getName()+".res", CI);
904 if (Or->getType() != CI->getType())
905 Or = CastInst::createIntegerCast(Or, CI->getType(), false /*ZExt*/,
907 return ReplaceCallWith(CI, Or);
919 /// This LibCallOptimization will simplify a call to the memcpy library
920 /// function by expanding it out to a single store of size 0, 1, 2, 4, or 8
921 /// bytes depending on the length of the string and the alignment. Additional
922 /// optimizations are possible in code generation (sequence of immediate store)
923 /// @brief Simplify the memcpy library function.
924 struct VISIBILITY_HIDDEN LLVMMemCpyMoveOptzn : public LibCallOptimization {
925 LLVMMemCpyMoveOptzn(const char* fname, const char* desc)
926 : LibCallOptimization(fname, desc) {}
928 /// @brief Make sure that the "memcpy" function has the right prototype
929 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& TD) {
930 // Just make sure this has 4 arguments per LLVM spec.
931 return (f->arg_size() == 4);
934 /// Because of alignment and instruction information that we don't have, we
935 /// leave the bulk of this to the code generators. The optimization here just
936 /// deals with a few degenerate cases where the length of the string and the
937 /// alignment match the sizes of our intrinsic types so we can do a load and
938 /// store instead of the memcpy call.
939 /// @brief Perform the memcpy optimization.
940 virtual bool OptimizeCall(CallInst* ci, SimplifyLibCalls& TD) {
941 // Make sure we have constant int values to work with
942 ConstantInt* LEN = dyn_cast<ConstantInt>(ci->getOperand(3));
945 ConstantInt* ALIGN = dyn_cast<ConstantInt>(ci->getOperand(4));
949 // If the length is larger than the alignment, we can't optimize
950 uint64_t len = LEN->getZExtValue();
951 uint64_t alignment = ALIGN->getZExtValue();
953 alignment = 1; // Alignment 0 is identity for alignment 1
957 // Get the type we will cast to, based on size of the string
958 Value* dest = ci->getOperand(1);
959 Value* src = ci->getOperand(2);
960 const Type* castType = 0;
963 // memcpy(d,s,0,a) -> d
964 return ReplaceCallWith(ci, 0);
965 case 1: castType = Type::Int8Ty; break;
966 case 2: castType = Type::Int16Ty; break;
967 case 4: castType = Type::Int32Ty; break;
968 case 8: castType = Type::Int64Ty; break;
973 // Cast source and dest to the right sized primitive and then load/store
974 CastInst* SrcCast = CastInst::create(Instruction::BitCast,
975 src, PointerType::get(castType), src->getName()+".cast", ci);
976 CastInst* DestCast = CastInst::create(Instruction::BitCast,
977 dest, PointerType::get(castType),dest->getName()+".cast", ci);
978 LoadInst* LI = new LoadInst(SrcCast,SrcCast->getName()+".val",ci);
979 new StoreInst(LI, DestCast, ci);
980 return ReplaceCallWith(ci, 0);
984 /// This LibCallOptimization will simplify a call to the memcpy/memmove library
986 LLVMMemCpyMoveOptzn LLVMMemCpyOptimizer32("llvm.memcpy.i32",
987 "Number of 'llvm.memcpy' calls simplified");
988 LLVMMemCpyMoveOptzn LLVMMemCpyOptimizer64("llvm.memcpy.i64",
989 "Number of 'llvm.memcpy' calls simplified");
990 LLVMMemCpyMoveOptzn LLVMMemMoveOptimizer32("llvm.memmove.i32",
991 "Number of 'llvm.memmove' calls simplified");
992 LLVMMemCpyMoveOptzn LLVMMemMoveOptimizer64("llvm.memmove.i64",
993 "Number of 'llvm.memmove' calls simplified");
995 /// This LibCallOptimization will simplify a call to the memset library
996 /// function by expanding it out to a single store of size 0, 1, 2, 4, or 8
997 /// bytes depending on the length argument.
998 struct VISIBILITY_HIDDEN LLVMMemSetOptimization : public LibCallOptimization {
999 /// @brief Default Constructor
1000 LLVMMemSetOptimization(const char *Name) : LibCallOptimization(Name,
1001 "Number of 'llvm.memset' calls simplified") {}
1003 /// @brief Make sure that the "memset" function has the right prototype
1004 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &TD) {
1005 // Just make sure this has 3 arguments per LLVM spec.
1006 return F->arg_size() == 4;
1009 /// Because of alignment and instruction information that we don't have, we
1010 /// leave the bulk of this to the code generators. The optimization here just
1011 /// deals with a few degenerate cases where the length parameter is constant
1012 /// and the alignment matches the sizes of our intrinsic types so we can do
1013 /// store instead of the memcpy call. Other calls are transformed into the
1014 /// llvm.memset intrinsic.
1015 /// @brief Perform the memset optimization.
1016 virtual bool OptimizeCall(CallInst *ci, SimplifyLibCalls &TD) {
1017 // Make sure we have constant int values to work with
1018 ConstantInt* LEN = dyn_cast<ConstantInt>(ci->getOperand(3));
1021 ConstantInt* ALIGN = dyn_cast<ConstantInt>(ci->getOperand(4));
1025 // Extract the length and alignment
1026 uint64_t len = LEN->getZExtValue();
1027 uint64_t alignment = ALIGN->getZExtValue();
1029 // Alignment 0 is identity for alignment 1
1033 // If the length is zero, this is a no-op
1035 // memset(d,c,0,a) -> noop
1036 return ReplaceCallWith(ci, 0);
1039 // If the length is larger than the alignment, we can't optimize
1040 if (len > alignment)
1043 // Make sure we have a constant ubyte to work with so we can extract
1044 // the value to be filled.
1045 ConstantInt* FILL = dyn_cast<ConstantInt>(ci->getOperand(2));
1048 if (FILL->getType() != Type::Int8Ty)
1051 // memset(s,c,n) -> store s, c (for n=1,2,4,8)
1053 // Extract the fill character
1054 uint64_t fill_char = FILL->getZExtValue();
1055 uint64_t fill_value = fill_char;
1057 // Get the type we will cast to, based on size of memory area to fill, and
1058 // and the value we will store there.
1059 Value* dest = ci->getOperand(1);
1060 const Type* castType = 0;
1063 castType = Type::Int8Ty;
1066 castType = Type::Int16Ty;
1067 fill_value |= fill_char << 8;
1070 castType = Type::Int32Ty;
1071 fill_value |= fill_char << 8 | fill_char << 16 | fill_char << 24;
1074 castType = Type::Int64Ty;
1075 fill_value |= fill_char << 8 | fill_char << 16 | fill_char << 24;
1076 fill_value |= fill_char << 32 | fill_char << 40 | fill_char << 48;
1077 fill_value |= fill_char << 56;
1083 // Cast dest to the right sized primitive and then load/store
1084 CastInst* DestCast = new BitCastInst(dest, PointerType::get(castType),
1085 dest->getName()+".cast", ci);
1086 new StoreInst(ConstantInt::get(castType,fill_value),DestCast, ci);
1087 return ReplaceCallWith(ci, 0);
1091 LLVMMemSetOptimization MemSet32Optimizer("llvm.memset.i32");
1092 LLVMMemSetOptimization MemSet64Optimizer("llvm.memset.i64");
1095 /// This LibCallOptimization will simplify calls to the "pow" library
1096 /// function. It looks for cases where the result of pow is well known and
1097 /// substitutes the appropriate value.
1098 /// @brief Simplify the pow library function.
1099 struct VISIBILITY_HIDDEN PowOptimization : public LibCallOptimization {
1101 /// @brief Default Constructor
1102 PowOptimization() : LibCallOptimization("pow",
1103 "Number of 'pow' calls simplified") {}
1105 /// @brief Make sure that the "pow" function has the right prototype
1106 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC){
1107 // Just make sure this has 2 arguments
1108 return (f->arg_size() == 2);
1111 /// @brief Perform the pow optimization.
1112 virtual bool OptimizeCall(CallInst *ci, SimplifyLibCalls &SLC) {
1113 const Type *Ty = cast<Function>(ci->getOperand(0))->getReturnType();
1114 Value* base = ci->getOperand(1);
1115 Value* expn = ci->getOperand(2);
1116 if (ConstantFP *Op1 = dyn_cast<ConstantFP>(base)) {
1117 double Op1V = Op1->getValue();
1118 if (Op1V == 1.0) // pow(1.0,x) -> 1.0
1119 return ReplaceCallWith(ci, ConstantFP::get(Ty, 1.0));
1120 } else if (ConstantFP* Op2 = dyn_cast<ConstantFP>(expn)) {
1121 double Op2V = Op2->getValue();
1123 // pow(x,0.0) -> 1.0
1124 return ReplaceCallWith(ci, ConstantFP::get(Ty,1.0));
1125 } else if (Op2V == 0.5) {
1126 // pow(x,0.5) -> sqrt(x)
1127 CallInst* sqrt_inst = new CallInst(SLC.get_sqrt(), base,
1128 ci->getName()+".pow",ci);
1129 return ReplaceCallWith(ci, sqrt_inst);
1130 } else if (Op2V == 1.0) {
1132 return ReplaceCallWith(ci, base);
1133 } else if (Op2V == -1.0) {
1134 // pow(x,-1.0) -> 1.0/x
1136 BinaryOperator::createFDiv(ConstantFP::get(Ty, 1.0), base,
1137 ci->getName()+".pow", ci);
1138 return ReplaceCallWith(ci, div_inst);
1141 return false; // opt failed
1145 /// This LibCallOptimization will simplify calls to the "printf" library
1146 /// function. It looks for cases where the result of printf is not used and the
1147 /// operation can be reduced to something simpler.
1148 /// @brief Simplify the printf library function.
1149 struct VISIBILITY_HIDDEN PrintfOptimization : public LibCallOptimization {
1151 /// @brief Default Constructor
1152 PrintfOptimization() : LibCallOptimization("printf",
1153 "Number of 'printf' calls simplified") {}
1155 /// @brief Make sure that the "printf" function has the right prototype
1156 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
1157 // Just make sure this has at least 1 arguments
1158 return F->arg_size() >= 1;
1161 /// @brief Perform the printf optimization.
1162 virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
1163 // If the call has more than 2 operands, we can't optimize it
1164 if (CI->getNumOperands() != 3)
1167 // All the optimizations depend on the length of the first argument and the
1168 // fact that it is a constant string array. Check that now
1169 std::string FormatStr;
1170 if (!GetConstantStringInfo(CI->getOperand(1), FormatStr))
1173 // Only support %c or "%s\n" for now.
1174 if (FormatStr.size() < 2 || FormatStr[0] != '%')
1177 // Get the second character and switch on its value
1178 switch (FormatStr[1]) {
1179 default: return false;
1181 if (FormatStr != "%s\n" ||
1182 // TODO: could insert strlen call to compute string length.
1186 // printf("%s\n",str) -> puts(str)
1187 new CallInst(SLC.get_puts(), CastToCStr(CI->getOperand(2), CI),
1189 return ReplaceCallWith(CI, 0);
1191 // printf("%c",c) -> putchar(c)
1192 if (FormatStr.size() != 2)
1195 Value *V = CI->getOperand(2);
1196 if (!isa<IntegerType>(V->getType()) ||
1197 cast<IntegerType>(V->getType())->getBitWidth() > 32)
1200 V = CastInst::createZExtOrBitCast(V, Type::Int32Ty, CI->getName()+".int",
1202 new CallInst(SLC.get_putchar(), V, "", CI);
1203 return ReplaceCallWith(CI, ConstantInt::get(CI->getType(), 1));
1209 /// This LibCallOptimization will simplify calls to the "fprintf" library
1210 /// function. It looks for cases where the result of fprintf is not used and the
1211 /// operation can be reduced to something simpler.
1212 /// @brief Simplify the fprintf library function.
1213 struct VISIBILITY_HIDDEN FPrintFOptimization : public LibCallOptimization {
1215 /// @brief Default Constructor
1216 FPrintFOptimization() : LibCallOptimization("fprintf",
1217 "Number of 'fprintf' calls simplified") {}
1219 /// @brief Make sure that the "fprintf" function has the right prototype
1220 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
1221 const FunctionType *FT = F->getFunctionType();
1222 return FT->getNumParams() == 2 && // two fixed arguments.
1223 FT->getParamType(1) == PointerType::get(Type::Int8Ty) &&
1224 isa<PointerType>(FT->getParamType(0)) &&
1225 isa<IntegerType>(FT->getReturnType());
1228 /// @brief Perform the fprintf optimization.
1229 virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
1230 // If the call has more than 3 operands, we can't optimize it
1231 if (CI->getNumOperands() != 3 && CI->getNumOperands() != 4)
1234 // All the optimizations depend on the format string.
1235 std::string FormatStr;
1236 if (!GetConstantStringInfo(CI->getOperand(2), FormatStr))
1239 // If this is just a format string, turn it into fwrite.
1240 if (CI->getNumOperands() == 3) {
1241 for (unsigned i = 0, e = FormatStr.size(); i != e; ++i)
1242 if (FormatStr[i] == '%')
1243 return false; // we found a format specifier
1245 // fprintf(file,fmt) -> fwrite(fmt,strlen(fmt),file)
1246 const Type *FILEty = CI->getOperand(1)->getType();
1248 Value *FWriteArgs[] = {
1250 ConstantInt::get(SLC.getIntPtrType(), FormatStr.size()),
1251 ConstantInt::get(SLC.getIntPtrType(), 1),
1254 new CallInst(SLC.get_fwrite(FILEty), FWriteArgs, 4, CI->getName(), CI);
1255 return ReplaceCallWith(CI, ConstantInt::get(CI->getType(),
1259 // The remaining optimizations require the format string to be length 2:
1261 if (FormatStr.size() != 2 || FormatStr[0] != '%')
1264 // Get the second character and switch on its value
1265 switch (FormatStr[1]) {
1267 // fprintf(file,"%c",c) -> fputc(c,file)
1268 const Type *FILETy = CI->getOperand(1)->getType();
1269 Value *C = CastInst::createZExtOrBitCast(CI->getOperand(3), Type::Int32Ty,
1270 CI->getName()+".int", CI);
1271 new CallInst(SLC.get_fputc(FILETy), C, CI->getOperand(1), "", CI);
1272 return ReplaceCallWith(CI, ConstantInt::get(CI->getType(), 1));
1275 const Type *FILETy = CI->getOperand(1)->getType();
1277 // If the result of the fprintf call is used, we can't do this.
1278 // TODO: we should insert a strlen call.
1279 if (!CI->use_empty())
1282 // fprintf(file,"%s",str) -> fputs(str,file)
1283 new CallInst(SLC.get_fputs(FILETy), CastToCStr(CI->getOperand(3), CI),
1284 CI->getOperand(1), CI->getName(), CI);
1285 return ReplaceCallWith(CI, 0);
1293 /// This LibCallOptimization will simplify calls to the "sprintf" library
1294 /// function. It looks for cases where the result of sprintf is not used and the
1295 /// operation can be reduced to something simpler.
1296 /// @brief Simplify the sprintf library function.
1297 struct VISIBILITY_HIDDEN SPrintFOptimization : public LibCallOptimization {
1299 /// @brief Default Constructor
1300 SPrintFOptimization() : LibCallOptimization("sprintf",
1301 "Number of 'sprintf' calls simplified") {}
1303 /// @brief Make sure that the "sprintf" function has the right prototype
1304 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
1305 const FunctionType *FT = F->getFunctionType();
1306 return FT->getNumParams() == 2 && // two fixed arguments.
1307 FT->getParamType(1) == PointerType::get(Type::Int8Ty) &&
1308 FT->getParamType(0) == FT->getParamType(1) &&
1309 isa<IntegerType>(FT->getReturnType());
1312 /// @brief Perform the sprintf optimization.
1313 virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
1314 // If the call has more than 3 operands, we can't optimize it
1315 if (CI->getNumOperands() != 3 && CI->getNumOperands() != 4)
1318 std::string FormatStr;
1319 if (!GetConstantStringInfo(CI->getOperand(2), FormatStr))
1322 if (CI->getNumOperands() == 3) {
1323 // Make sure there's no % in the constant array
1324 for (unsigned i = 0, e = FormatStr.size(); i != e; ++i)
1325 if (FormatStr[i] == '%')
1326 return false; // we found a format specifier
1328 // sprintf(str,fmt) -> llvm.memcpy(str,fmt,strlen(fmt),1)
1329 Value *MemCpyArgs[] = {
1330 CI->getOperand(1), CI->getOperand(2),
1331 ConstantInt::get(SLC.getIntPtrType(),
1332 FormatStr.size()+1), // Copy the nul byte.
1333 ConstantInt::get(Type::Int32Ty, 1)
1335 new CallInst(SLC.get_memcpy(), MemCpyArgs, 4, "", CI);
1336 return ReplaceCallWith(CI, ConstantInt::get(CI->getType(),
1340 // The remaining optimizations require the format string to be "%s" or "%c".
1341 if (FormatStr.size() != 2 || FormatStr[0] != '%')
1344 // Get the second character and switch on its value
1345 switch (FormatStr[1]) {
1347 // sprintf(dest,"%c",chr) -> store chr, dest
1348 Value *V = CastInst::createTruncOrBitCast(CI->getOperand(3),
1349 Type::Int8Ty, "char", CI);
1350 new StoreInst(V, CI->getOperand(1), CI);
1351 Value *Ptr = new GetElementPtrInst(CI->getOperand(1),
1352 ConstantInt::get(Type::Int32Ty, 1),
1353 CI->getOperand(1)->getName()+".end",
1355 new StoreInst(ConstantInt::get(Type::Int8Ty,0), Ptr, CI);
1356 return ReplaceCallWith(CI, ConstantInt::get(Type::Int32Ty, 1));
1359 // sprintf(dest,"%s",str) -> llvm.memcpy(dest, str, strlen(str)+1, 1)
1360 Value *Len = new CallInst(SLC.get_strlen(),
1361 CastToCStr(CI->getOperand(3), CI),
1362 CI->getOperand(3)->getName()+".len", CI);
1363 Value *UnincLen = Len;
1364 Len = BinaryOperator::createAdd(Len, ConstantInt::get(Len->getType(), 1),
1365 Len->getName()+"1", CI);
1366 Value *MemcpyArgs[4] = {
1368 CastToCStr(CI->getOperand(3), CI),
1370 ConstantInt::get(Type::Int32Ty, 1)
1372 new CallInst(SLC.get_memcpy(), MemcpyArgs, 4, "", CI);
1374 // The strlen result is the unincremented number of bytes in the string.
1375 if (!CI->use_empty()) {
1376 if (UnincLen->getType() != CI->getType())
1377 UnincLen = CastInst::createIntegerCast(UnincLen, CI->getType(), false,
1378 Len->getName(), CI);
1379 CI->replaceAllUsesWith(UnincLen);
1381 return ReplaceCallWith(CI, 0);
1388 /// This LibCallOptimization will simplify calls to the "fputs" library
1389 /// function. It looks for cases where the result of fputs is not used and the
1390 /// operation can be reduced to something simpler.
1391 /// @brief Simplify the fputs library function.
1392 struct VISIBILITY_HIDDEN FPutsOptimization : public LibCallOptimization {
1394 /// @brief Default Constructor
1395 FPutsOptimization() : LibCallOptimization("fputs",
1396 "Number of 'fputs' calls simplified") {}
1398 /// @brief Make sure that the "fputs" function has the right prototype
1399 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
1400 // Just make sure this has 2 arguments
1401 return F->arg_size() == 2;
1404 /// @brief Perform the fputs optimization.
1405 virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
1406 // If the result is used, none of these optimizations work.
1407 if (!CI->use_empty())
1410 // All the optimizations depend on the length of the first argument and the
1411 // fact that it is a constant string array. Check that now
1413 if (!GetConstantStringInfo(CI->getOperand(1), Str))
1416 const Type *FILETy = CI->getOperand(2)->getType();
1417 // fputs(s,F) -> fwrite(s,1,len,F) (if s is constant and strlen(s) > 1)
1418 Value *FWriteParms[4] = {
1420 ConstantInt::get(SLC.getIntPtrType(), Str.size()),
1421 ConstantInt::get(SLC.getIntPtrType(), 1),
1424 new CallInst(SLC.get_fwrite(FILETy), FWriteParms, 4, "", CI);
1425 return ReplaceCallWith(CI, 0); // Known to have no uses (see above).
1429 /// This LibCallOptimization will simplify calls to the "fwrite" function.
1430 struct VISIBILITY_HIDDEN FWriteOptimization : public LibCallOptimization {
1432 /// @brief Default Constructor
1433 FWriteOptimization() : LibCallOptimization("fwrite",
1434 "Number of 'fwrite' calls simplified") {}
1436 /// @brief Make sure that the "fputs" function has the right prototype
1437 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
1438 const FunctionType *FT = F->getFunctionType();
1439 return FT->getNumParams() == 4 &&
1440 FT->getParamType(0) == PointerType::get(Type::Int8Ty) &&
1441 FT->getParamType(1) == FT->getParamType(2) &&
1442 isa<IntegerType>(FT->getParamType(1)) &&
1443 isa<PointerType>(FT->getParamType(3)) &&
1444 isa<IntegerType>(FT->getReturnType());
1447 virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
1448 // Get the element size and count.
1449 uint64_t EltSize, EltCount;
1450 if (ConstantInt *C = dyn_cast<ConstantInt>(CI->getOperand(2)))
1451 EltSize = C->getZExtValue();
1454 if (ConstantInt *C = dyn_cast<ConstantInt>(CI->getOperand(3)))
1455 EltCount = C->getZExtValue();
1459 // If this is writing zero records, remove the call (it's a noop).
1460 if (EltSize * EltCount == 0)
1461 return ReplaceCallWith(CI, ConstantInt::get(CI->getType(), 0));
1463 // If this is writing one byte, turn it into fputc.
1464 if (EltSize == 1 && EltCount == 1) {
1465 // fwrite(s,1,1,F) -> fputc(s[0],F)
1466 Value *Ptr = CI->getOperand(1);
1467 Value *Val = new LoadInst(Ptr, Ptr->getName()+".byte", CI);
1468 Val = new ZExtInst(Val, Type::Int32Ty, Val->getName()+".int", CI);
1469 const Type *FILETy = CI->getOperand(4)->getType();
1470 new CallInst(SLC.get_fputc(FILETy), Val, CI->getOperand(4), "", CI);
1471 return ReplaceCallWith(CI, ConstantInt::get(CI->getType(), 1));
1477 /// This LibCallOptimization will simplify calls to the "isdigit" library
1478 /// function. It simply does range checks the parameter explicitly.
1479 /// @brief Simplify the isdigit library function.
1480 struct VISIBILITY_HIDDEN isdigitOptimization : public LibCallOptimization {
1482 isdigitOptimization() : LibCallOptimization("isdigit",
1483 "Number of 'isdigit' calls simplified") {}
1485 /// @brief Make sure that the "isdigit" function has the right prototype
1486 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC){
1487 // Just make sure this has 1 argument
1488 return (f->arg_size() == 1);
1491 /// @brief Perform the toascii optimization.
1492 virtual bool OptimizeCall(CallInst *ci, SimplifyLibCalls &SLC) {
1493 if (ConstantInt* CI = dyn_cast<ConstantInt>(ci->getOperand(1))) {
1494 // isdigit(c) -> 0 or 1, if 'c' is constant
1495 uint64_t val = CI->getZExtValue();
1496 if (val >= '0' && val <= '9')
1497 return ReplaceCallWith(ci, ConstantInt::get(Type::Int32Ty, 1));
1499 return ReplaceCallWith(ci, ConstantInt::get(Type::Int32Ty, 0));
1502 // isdigit(c) -> (unsigned)c - '0' <= 9
1503 CastInst* cast = CastInst::createIntegerCast(ci->getOperand(1),
1504 Type::Int32Ty, false/*ZExt*/, ci->getOperand(1)->getName()+".uint", ci);
1505 BinaryOperator* sub_inst = BinaryOperator::createSub(cast,
1506 ConstantInt::get(Type::Int32Ty,0x30),
1507 ci->getOperand(1)->getName()+".sub",ci);
1508 ICmpInst* setcond_inst = new ICmpInst(ICmpInst::ICMP_ULE,sub_inst,
1509 ConstantInt::get(Type::Int32Ty,9),
1510 ci->getOperand(1)->getName()+".cmp",ci);
1511 CastInst* c2 = new ZExtInst(setcond_inst, Type::Int32Ty,
1512 ci->getOperand(1)->getName()+".isdigit", ci);
1513 return ReplaceCallWith(ci, c2);
1517 struct VISIBILITY_HIDDEN isasciiOptimization : public LibCallOptimization {
1519 isasciiOptimization()
1520 : LibCallOptimization("isascii", "Number of 'isascii' calls simplified") {}
1522 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
1523 return F->arg_size() == 1 && F->arg_begin()->getType()->isInteger() &&
1524 F->getReturnType()->isInteger();
1527 /// @brief Perform the isascii optimization.
1528 virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
1529 // isascii(c) -> (unsigned)c < 128
1530 Value *V = CI->getOperand(1);
1531 Value *Cmp = new ICmpInst(ICmpInst::ICMP_ULT, V,
1532 ConstantInt::get(V->getType(), 128),
1533 V->getName()+".isascii", CI);
1534 if (Cmp->getType() != CI->getType())
1535 Cmp = new BitCastInst(Cmp, CI->getType(), Cmp->getName(), CI);
1536 return ReplaceCallWith(CI, Cmp);
1541 /// This LibCallOptimization will simplify calls to the "toascii" library
1542 /// function. It simply does the corresponding and operation to restrict the
1543 /// range of values to the ASCII character set (0-127).
1544 /// @brief Simplify the toascii library function.
1545 struct VISIBILITY_HIDDEN ToAsciiOptimization : public LibCallOptimization {
1547 /// @brief Default Constructor
1548 ToAsciiOptimization() : LibCallOptimization("toascii",
1549 "Number of 'toascii' calls simplified") {}
1551 /// @brief Make sure that the "fputs" function has the right prototype
1552 virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC){
1553 // Just make sure this has 2 arguments
1554 return (f->arg_size() == 1);
1557 /// @brief Perform the toascii optimization.
1558 virtual bool OptimizeCall(CallInst *ci, SimplifyLibCalls &SLC) {
1559 // toascii(c) -> (c & 0x7f)
1560 Value *chr = ci->getOperand(1);
1561 Value *and_inst = BinaryOperator::createAnd(chr,
1562 ConstantInt::get(chr->getType(),0x7F),ci->getName()+".toascii",ci);
1563 return ReplaceCallWith(ci, and_inst);
1567 /// This LibCallOptimization will simplify calls to the "ffs" library
1568 /// calls which find the first set bit in an int, long, or long long. The
1569 /// optimization is to compute the result at compile time if the argument is
1571 /// @brief Simplify the ffs library function.
1572 struct VISIBILITY_HIDDEN FFSOptimization : public LibCallOptimization {
1574 /// @brief Subclass Constructor
1575 FFSOptimization(const char* funcName, const char* description)
1576 : LibCallOptimization(funcName, description) {}
1579 /// @brief Default Constructor
1580 FFSOptimization() : LibCallOptimization("ffs",
1581 "Number of 'ffs' calls simplified") {}
1583 /// @brief Make sure that the "ffs" function has the right prototype
1584 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
1585 // Just make sure this has 2 arguments
1586 return F->arg_size() == 1 && F->getReturnType() == Type::Int32Ty;
1589 /// @brief Perform the ffs optimization.
1590 virtual bool OptimizeCall(CallInst *TheCall, SimplifyLibCalls &SLC) {
1591 if (ConstantInt *CI = dyn_cast<ConstantInt>(TheCall->getOperand(1))) {
1592 // ffs(cnst) -> bit#
1593 // ffsl(cnst) -> bit#
1594 // ffsll(cnst) -> bit#
1595 uint64_t val = CI->getZExtValue();
1599 while ((val & 1) == 0) {
1604 return ReplaceCallWith(TheCall, ConstantInt::get(Type::Int32Ty, result));
1607 // ffs(x) -> x == 0 ? 0 : llvm.cttz(x)+1
1608 // ffsl(x) -> x == 0 ? 0 : llvm.cttz(x)+1
1609 // ffsll(x) -> x == 0 ? 0 : llvm.cttz(x)+1
1610 const Type *ArgType = TheCall->getOperand(1)->getType();
1611 const char *CTTZName;
1612 assert(ArgType->getTypeID() == Type::IntegerTyID &&
1613 "llvm.cttz argument is not an integer?");
1614 unsigned BitWidth = cast<IntegerType>(ArgType)->getBitWidth();
1616 CTTZName = "llvm.cttz.i8";
1617 else if (BitWidth == 16)
1618 CTTZName = "llvm.cttz.i16";
1619 else if (BitWidth == 32)
1620 CTTZName = "llvm.cttz.i32";
1622 assert(BitWidth == 64 && "Unknown bitwidth");
1623 CTTZName = "llvm.cttz.i64";
1626 Constant *F = SLC.getModule()->getOrInsertFunction(CTTZName, ArgType,
1628 Value *V = CastInst::createIntegerCast(TheCall->getOperand(1), ArgType,
1629 false/*ZExt*/, "tmp", TheCall);
1630 Value *V2 = new CallInst(F, V, "tmp", TheCall);
1631 V2 = CastInst::createIntegerCast(V2, Type::Int32Ty, false/*ZExt*/,
1633 V2 = BinaryOperator::createAdd(V2, ConstantInt::get(Type::Int32Ty, 1),
1635 Value *Cond = new ICmpInst(ICmpInst::ICMP_EQ, V,
1636 Constant::getNullValue(V->getType()), "tmp",
1638 V2 = new SelectInst(Cond, ConstantInt::get(Type::Int32Ty, 0), V2,
1639 TheCall->getName(), TheCall);
1640 return ReplaceCallWith(TheCall, V2);
1644 /// This LibCallOptimization will simplify calls to the "ffsl" library
1645 /// calls. It simply uses FFSOptimization for which the transformation is
1647 /// @brief Simplify the ffsl library function.
1648 struct VISIBILITY_HIDDEN FFSLOptimization : public FFSOptimization {
1650 /// @brief Default Constructor
1651 FFSLOptimization() : FFSOptimization("ffsl",
1652 "Number of 'ffsl' calls simplified") {}
1656 /// This LibCallOptimization will simplify calls to the "ffsll" library
1657 /// calls. It simply uses FFSOptimization for which the transformation is
1659 /// @brief Simplify the ffsl library function.
1660 struct VISIBILITY_HIDDEN FFSLLOptimization : public FFSOptimization {
1662 /// @brief Default Constructor
1663 FFSLLOptimization() : FFSOptimization("ffsll",
1664 "Number of 'ffsll' calls simplified") {}
1668 /// This optimizes unary functions that take and return doubles.
1669 struct UnaryDoubleFPOptimizer : public LibCallOptimization {
1670 UnaryDoubleFPOptimizer(const char *Fn, const char *Desc)
1671 : LibCallOptimization(Fn, Desc) {}
1673 // Make sure that this function has the right prototype
1674 virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
1675 return F->arg_size() == 1 && F->arg_begin()->getType() == Type::DoubleTy &&
1676 F->getReturnType() == Type::DoubleTy;
1679 /// ShrinkFunctionToFloatVersion - If the input to this function is really a
1680 /// float, strength reduce this to a float version of the function,
1681 /// e.g. floor((double)FLT) -> (double)floorf(FLT). This can only be called
1682 /// when the target supports the destination function and where there can be
1683 /// no precision loss.
1684 static bool ShrinkFunctionToFloatVersion(CallInst *CI, SimplifyLibCalls &SLC,
1685 Constant *(SimplifyLibCalls::*FP)()){
1686 if (FPExtInst *Cast = dyn_cast<FPExtInst>(CI->getOperand(1)))
1687 if (Cast->getOperand(0)->getType() == Type::FloatTy) {
1688 Value *New = new CallInst((SLC.*FP)(), Cast->getOperand(0),
1690 New = new FPExtInst(New, Type::DoubleTy, CI->getName(), CI);
1691 CI->replaceAllUsesWith(New);
1692 CI->eraseFromParent();
1693 if (Cast->use_empty())
1694 Cast->eraseFromParent();
1702 struct VISIBILITY_HIDDEN FloorOptimization : public UnaryDoubleFPOptimizer {
1704 : UnaryDoubleFPOptimizer("floor", "Number of 'floor' calls simplified") {}
1706 virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
1708 // If this is a float argument passed in, convert to floorf.
1709 if (ShrinkFunctionToFloatVersion(CI, SLC, &SimplifyLibCalls::get_floorf))
1712 return false; // opt failed
1716 struct VISIBILITY_HIDDEN CeilOptimization : public UnaryDoubleFPOptimizer {
1718 : UnaryDoubleFPOptimizer("ceil", "Number of 'ceil' calls simplified") {}
1720 virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
1722 // If this is a float argument passed in, convert to ceilf.
1723 if (ShrinkFunctionToFloatVersion(CI, SLC, &SimplifyLibCalls::get_ceilf))
1726 return false; // opt failed
1730 struct VISIBILITY_HIDDEN RoundOptimization : public UnaryDoubleFPOptimizer {
1732 : UnaryDoubleFPOptimizer("round", "Number of 'round' calls simplified") {}
1734 virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
1736 // If this is a float argument passed in, convert to roundf.
1737 if (ShrinkFunctionToFloatVersion(CI, SLC, &SimplifyLibCalls::get_roundf))
1740 return false; // opt failed
1744 struct VISIBILITY_HIDDEN RintOptimization : public UnaryDoubleFPOptimizer {
1746 : UnaryDoubleFPOptimizer("rint", "Number of 'rint' calls simplified") {}
1748 virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
1750 // If this is a float argument passed in, convert to rintf.
1751 if (ShrinkFunctionToFloatVersion(CI, SLC, &SimplifyLibCalls::get_rintf))
1754 return false; // opt failed
1758 struct VISIBILITY_HIDDEN NearByIntOptimization : public UnaryDoubleFPOptimizer {
1759 NearByIntOptimization()
1760 : UnaryDoubleFPOptimizer("nearbyint",
1761 "Number of 'nearbyint' calls simplified") {}
1763 virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
1764 #ifdef HAVE_NEARBYINTF
1765 // If this is a float argument passed in, convert to nearbyintf.
1766 if (ShrinkFunctionToFloatVersion(CI, SLC,&SimplifyLibCalls::get_nearbyintf))
1769 return false; // opt failed
1771 } NearByIntOptimizer;
1773 /// GetConstantStringInfo - This function computes the length of a
1774 /// null-terminated constant array of integers. This function can't rely on the
1775 /// size of the constant array because there could be a null terminator in the
1776 /// middle of the array.
1778 /// We also have to bail out if we find a non-integer constant initializer
1779 /// of one of the elements or if there is no null-terminator. The logic
1780 /// below checks each of these conditions and will return true only if all
1781 /// conditions are met. If the conditions aren't met, this returns false.
1783 /// If successful, the \p Array param is set to the constant array being
1784 /// indexed, the \p Length parameter is set to the length of the null-terminated
1785 /// string pointed to by V, the \p StartIdx value is set to the first
1786 /// element of the Array that V points to, and true is returned.
1787 static bool GetConstantStringInfo(Value *V, std::string &Str) {
1788 // Look through noop bitcast instructions.
1789 if (BitCastInst *BCI = dyn_cast<BitCastInst>(V)) {
1790 if (BCI->getType() == BCI->getOperand(0)->getType())
1791 return GetConstantStringInfo(BCI->getOperand(0), Str);
1795 // If the value is not a GEP instruction nor a constant expression with a
1796 // GEP instruction, then return false because ConstantArray can't occur
1799 if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(V)) {
1801 } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) {
1802 if (CE->getOpcode() != Instruction::GetElementPtr)
1809 // Make sure the GEP has exactly three arguments.
1810 if (GEP->getNumOperands() != 3)
1813 // Check to make sure that the first operand of the GEP is an integer and
1814 // has value 0 so that we are sure we're indexing into the initializer.
1815 if (ConstantInt *Idx = dyn_cast<ConstantInt>(GEP->getOperand(1))) {
1821 // If the second index isn't a ConstantInt, then this is a variable index
1822 // into the array. If this occurs, we can't say anything meaningful about
1824 uint64_t StartIdx = 0;
1825 if (ConstantInt *CI = dyn_cast<ConstantInt>(GEP->getOperand(2)))
1826 StartIdx = CI->getZExtValue();
1830 // The GEP instruction, constant or instruction, must reference a global
1831 // variable that is a constant and is initialized. The referenced constant
1832 // initializer is the array that we'll use for optimization.
1833 GlobalVariable* GV = dyn_cast<GlobalVariable>(GEP->getOperand(0));
1834 if (!GV || !GV->isConstant() || !GV->hasInitializer())
1836 Constant *GlobalInit = GV->getInitializer();
1838 // Handle the ConstantAggregateZero case
1839 if (isa<ConstantAggregateZero>(GlobalInit)) {
1840 // This is a degenerate case. The initializer is constant zero so the
1841 // length of the string must be zero.
1846 // Must be a Constant Array
1847 ConstantArray *Array = dyn_cast<ConstantArray>(GlobalInit);
1848 if (!Array) return false;
1850 // Get the number of elements in the array
1851 uint64_t NumElts = Array->getType()->getNumElements();
1853 // Traverse the constant array from StartIdx (derived above) which is
1854 // the place the GEP refers to in the array.
1855 for (unsigned i = StartIdx; i < NumElts; ++i) {
1856 Constant *Elt = Array->getOperand(i);
1857 ConstantInt *CI = dyn_cast<ConstantInt>(Elt);
1858 if (!CI) // This array isn't suitable, non-int initializer.
1861 return true; // we found end of string, success!
1862 Str += (char)CI->getZExtValue();
1865 return false; // The array isn't null terminated.
1868 /// CastToCStr - Return V if it is an sbyte*, otherwise cast it to sbyte*,
1869 /// inserting the cast before IP, and return the cast.
1870 /// @brief Cast a value to a "C" string.
1871 static Value *CastToCStr(Value *V, Instruction *IP) {
1872 assert(isa<PointerType>(V->getType()) &&
1873 "Can't cast non-pointer type to C string type");
1874 const Type *SBPTy = PointerType::get(Type::Int8Ty);
1875 if (V->getType() != SBPTy)
1876 return new BitCastInst(V, SBPTy, V->getName(), IP);
1881 // Additional cases that we need to add to this file:
1884 // * cbrt(expN(X)) -> expN(x/3)
1885 // * cbrt(sqrt(x)) -> pow(x,1/6)
1886 // * cbrt(sqrt(x)) -> pow(x,1/9)
1889 // * cos(-x) -> cos(x)
1892 // * exp(log(x)) -> x
1895 // * log(exp(x)) -> x
1896 // * log(x**y) -> y*log(x)
1897 // * log(exp(y)) -> y*log(e)
1898 // * log(exp2(y)) -> y*log(2)
1899 // * log(exp10(y)) -> y*log(10)
1900 // * log(sqrt(x)) -> 0.5*log(x)
1901 // * log(pow(x,y)) -> y*log(x)
1903 // lround, lroundf, lroundl:
1904 // * lround(cnst) -> cnst'
1907 // * memcmp(x,y,l) -> cnst
1908 // (if all arguments are constant and strlen(x) <= l and strlen(y) <= l)
1911 // * memmove(d,s,l,a) -> memcpy(d,s,l,a)
1912 // (if s is a global constant array)
1915 // * pow(exp(x),y) -> exp(x*y)
1916 // * pow(sqrt(x),y) -> pow(x,y*0.5)
1917 // * pow(pow(x,y),z)-> pow(x,y*z)
1920 // * puts("") -> fputc("\n",stdout) (how do we get "stdout"?)
1922 // round, roundf, roundl:
1923 // * round(cnst) -> cnst'
1926 // * signbit(cnst) -> cnst'
1927 // * signbit(nncst) -> 0 (if pstv is a non-negative constant)
1929 // sqrt, sqrtf, sqrtl:
1930 // * sqrt(expN(x)) -> expN(x*0.5)
1931 // * sqrt(Nroot(x)) -> pow(x,1/(2*N))
1932 // * sqrt(pow(x,y)) -> pow(|x|,y*0.5)
1935 // * stpcpy(str, "literal") ->
1936 // llvm.memcpy(str,"literal",strlen("literal")+1,1)
1938 // * strrchr(s,c) -> reverse_offset_of_in(c,s)
1939 // (if c is a constant integer and s is a constant string)
1940 // * strrchr(s1,0) -> strchr(s1,0)
1943 // * strncat(x,y,0) -> x
1944 // * strncat(x,y,0) -> x (if strlen(y) = 0)
1945 // * strncat(x,y,l) -> strcat(x,y) (if y and l are constants an l > strlen(y))
1948 // * strncpy(d,s,0) -> d
1949 // * strncpy(d,s,l) -> memcpy(d,s,l,1)
1950 // (if s and l are constants)
1953 // * strpbrk(s,a) -> offset_in_for(s,a)
1954 // (if s and a are both constant strings)
1955 // * strpbrk(s,"") -> 0
1956 // * strpbrk(s,a) -> strchr(s,a[0]) (if a is constant string of length 1)
1959 // * strspn(s,a) -> const_int (if both args are constant)
1960 // * strspn("",a) -> 0
1961 // * strspn(s,"") -> 0
1962 // * strcspn(s,a) -> const_int (if both args are constant)
1963 // * strcspn("",a) -> 0
1964 // * strcspn(s,"") -> strlen(a)
1967 // * strstr(x,x) -> x
1968 // * strstr(s1,s2) -> offset_of_s2_in(s1)
1969 // (if s1 and s2 are constant strings)
1972 // * tan(atan(x)) -> x
1974 // trunc, truncf, truncl:
1975 // * trunc(cnst) -> cnst'