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llvm-mirror/lib/Transforms/Scalar/SimplifyLibCalls.cpp
Nick Lewycky 8fd2389593 Turn strcmp into memcmp, such as strcmp(P, "x") --> memcmp(P, "x", 2). 
llvm-svn: 61297
2008-12-21 00:19:21 +00:00

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//===- SimplifyLibCalls.cpp - Optimize specific well-known library calls --===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements a simple pass that applies a variety of small
// optimizations for calls to specific well-known function calls (e.g. runtime
// library functions). For example, a call to the function "exit(3)" that
// occurs within the main() function can be transformed into a simple "return 3"
// instruction. Any optimization that takes this form (replace call to library
// function with simpler code that provides the same result) belongs in this
// file.
//
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "simplify-libcalls"
#include "llvm/Transforms/Scalar.h"
#include "llvm/Intrinsics.h"
#include "llvm/Module.h"
#include "llvm/Pass.h"
#include "llvm/Support/IRBuilder.h"
#include "llvm/Analysis/ValueTracking.h"
#include "llvm/Target/TargetData.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/StringMap.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Support/Debug.h"
#include "llvm/Config/config.h"
using namespace llvm;
STATISTIC(NumSimplified, "Number of library calls simplified");
//===----------------------------------------------------------------------===//
// Optimizer Base Class
//===----------------------------------------------------------------------===//
/// This class is the abstract base class for the set of optimizations that
/// corresponds to one library call.
namespace {
class VISIBILITY_HIDDEN LibCallOptimization {
protected:
Function *Caller;
const TargetData *TD;
public:
LibCallOptimization() { }
virtual ~LibCallOptimization() {}
/// CallOptimizer - This pure virtual method is implemented by base classes to
/// do various optimizations. If this returns null then no transformation was
/// performed. If it returns CI, then it transformed the call and CI is to be
/// deleted. If it returns something else, replace CI with the new value and
/// delete CI.
virtual Value *CallOptimizer(Function *Callee, CallInst *CI, IRBuilder<> &B)
=0;
Value *OptimizeCall(CallInst *CI, const TargetData &TD, IRBuilder<> &B) {
Caller = CI->getParent()->getParent();
this->TD = &TD;
return CallOptimizer(CI->getCalledFunction(), CI, B);
}
/// CastToCStr - Return V if it is an i8*, otherwise cast it to i8*.
Value *CastToCStr(Value *V, IRBuilder<> &B);
/// EmitStrLen - Emit a call to the strlen function to the builder, for the
/// specified pointer. Ptr is required to be some pointer type, and the
/// return value has 'intptr_t' type.
Value *EmitStrLen(Value *Ptr, IRBuilder<> &B);
/// EmitMemCpy - Emit a call to the memcpy function to the builder. This
/// always expects that the size has type 'intptr_t' and Dst/Src are pointers.
Value *EmitMemCpy(Value *Dst, Value *Src, Value *Len,
unsigned Align, IRBuilder<> &B);
/// EmitMemChr - Emit a call to the memchr function. This assumes that Ptr is
/// a pointer, Val is an i32 value, and Len is an 'intptr_t' value.
Value *EmitMemChr(Value *Ptr, Value *Val, Value *Len, IRBuilder<> &B);
/// EmitMemCmp - Emit a call to the memcmp function.
Value *EmitMemCmp(Value *Ptr1, Value *Ptr2, Value *Len, IRBuilder<> &B);
/// EmitUnaryFloatFnCall - Emit a call to the unary function named 'Name' (e.g.
/// 'floor'). This function is known to take a single of type matching 'Op'
/// and returns one value with the same type. If 'Op' is a long double, 'l'
/// is added as the suffix of name, if 'Op' is a float, we add a 'f' suffix.
Value *EmitUnaryFloatFnCall(Value *Op, const char *Name, IRBuilder<> &B);
/// EmitPutChar - Emit a call to the putchar function. This assumes that Char
/// is an integer.
void EmitPutChar(Value *Char, IRBuilder<> &B);
/// EmitPutS - Emit a call to the puts function. This assumes that Str is
/// some pointer.
void EmitPutS(Value *Str, IRBuilder<> &B);
/// EmitFPutC - Emit a call to the fputc function. This assumes that Char is
/// an i32, and File is a pointer to FILE.
void EmitFPutC(Value *Char, Value *File, IRBuilder<> &B);
/// EmitFPutS - Emit a call to the puts function. Str is required to be a
/// pointer and File is a pointer to FILE.
void EmitFPutS(Value *Str, Value *File, IRBuilder<> &B);
/// EmitFWrite - Emit a call to the fwrite function. This assumes that Ptr is
/// a pointer, Size is an 'intptr_t', and File is a pointer to FILE.
void EmitFWrite(Value *Ptr, Value *Size, Value *File, IRBuilder<> &B);
};
} // End anonymous namespace.
/// CastToCStr - Return V if it is an i8*, otherwise cast it to i8*.
Value *LibCallOptimization::CastToCStr(Value *V, IRBuilder<> &B) {
return B.CreateBitCast(V, PointerType::getUnqual(Type::Int8Ty), "cstr");
}
/// EmitStrLen - Emit a call to the strlen function to the builder, for the
/// specified pointer. This always returns an integer value of size intptr_t.
Value *LibCallOptimization::EmitStrLen(Value *Ptr, IRBuilder<> &B) {
Module *M = Caller->getParent();
Constant *StrLen =M->getOrInsertFunction("strlen", TD->getIntPtrType(),
PointerType::getUnqual(Type::Int8Ty),
NULL);
return B.CreateCall(StrLen, CastToCStr(Ptr, B), "strlen");
}
/// EmitMemCpy - Emit a call to the memcpy function to the builder. This always
/// expects that the size has type 'intptr_t' and Dst/Src are pointers.
Value *LibCallOptimization::EmitMemCpy(Value *Dst, Value *Src, Value *Len,
unsigned Align, IRBuilder<> &B) {
Module *M = Caller->getParent();
Intrinsic::ID IID = Intrinsic::memcpy;
const Type *Tys[1];
Tys[0] = Len->getType();
Value *MemCpy = Intrinsic::getDeclaration(M, IID, Tys, 1);
return B.CreateCall4(MemCpy, CastToCStr(Dst, B), CastToCStr(Src, B), Len,
ConstantInt::get(Type::Int32Ty, Align));
}
/// EmitMemChr - Emit a call to the memchr function. This assumes that Ptr is
/// a pointer, Val is an i32 value, and Len is an 'intptr_t' value.
Value *LibCallOptimization::EmitMemChr(Value *Ptr, Value *Val,
Value *Len, IRBuilder<> &B) {
Module *M = Caller->getParent();
Value *MemChr = M->getOrInsertFunction("memchr",
PointerType::getUnqual(Type::Int8Ty),
PointerType::getUnqual(Type::Int8Ty),
Type::Int32Ty, TD->getIntPtrType(),
NULL);
return B.CreateCall3(MemChr, CastToCStr(Ptr, B), Val, Len, "memchr");
}
/// EmitMemCmp - Emit a call to the memcmp function.
Value *LibCallOptimization::EmitMemCmp(Value *Ptr1, Value *Ptr2,
Value *Len, IRBuilder<> &B) {
Module *M = Caller->getParent();
Value *MemCmp = M->getOrInsertFunction("memcmp",
Type::Int32Ty,
PointerType::getUnqual(Type::Int8Ty),
PointerType::getUnqual(Type::Int8Ty),
TD->getIntPtrType(), NULL);
return B.CreateCall3(MemCmp, CastToCStr(Ptr1, B), CastToCStr(Ptr2, B),
Len, "memcmp");
}
/// EmitUnaryFloatFnCall - Emit a call to the unary function named 'Name' (e.g.
/// 'floor'). This function is known to take a single of type matching 'Op' and
/// returns one value with the same type. If 'Op' is a long double, 'l' is
/// added as the suffix of name, if 'Op' is a float, we add a 'f' suffix.
Value *LibCallOptimization::EmitUnaryFloatFnCall(Value *Op, const char *Name,
IRBuilder<> &B) {
char NameBuffer[20];
if (Op->getType() != Type::DoubleTy) {
// If we need to add a suffix, copy into NameBuffer.
unsigned NameLen = strlen(Name);
assert(NameLen < sizeof(NameBuffer)-2);
memcpy(NameBuffer, Name, NameLen);
if (Op->getType() == Type::FloatTy)
NameBuffer[NameLen] = 'f'; // floorf
else
NameBuffer[NameLen] = 'l'; // floorl
NameBuffer[NameLen+1] = 0;
Name = NameBuffer;
}
Module *M = Caller->getParent();
Value *Callee = M->getOrInsertFunction(Name, Op->getType(),
Op->getType(), NULL);
return B.CreateCall(Callee, Op, Name);
}
/// EmitPutChar - Emit a call to the putchar function. This assumes that Char
/// is an integer.
void LibCallOptimization::EmitPutChar(Value *Char, IRBuilder<> &B) {
Module *M = Caller->getParent();
Value *F = M->getOrInsertFunction("putchar", Type::Int32Ty,
Type::Int32Ty, NULL);
B.CreateCall(F, B.CreateIntCast(Char, Type::Int32Ty, "chari"), "putchar");
}
/// EmitPutS - Emit a call to the puts function. This assumes that Str is
/// some pointer.
void LibCallOptimization::EmitPutS(Value *Str, IRBuilder<> &B) {
Module *M = Caller->getParent();
Value *F = M->getOrInsertFunction("puts", Type::Int32Ty,
PointerType::getUnqual(Type::Int8Ty), NULL);
B.CreateCall(F, CastToCStr(Str, B), "puts");
}
/// EmitFPutC - Emit a call to the fputc function. This assumes that Char is
/// an integer and File is a pointer to FILE.
void LibCallOptimization::EmitFPutC(Value *Char, Value *File, IRBuilder<> &B) {
Module *M = Caller->getParent();
Constant *F = M->getOrInsertFunction("fputc", Type::Int32Ty, Type::Int32Ty,
File->getType(), NULL);
Char = B.CreateIntCast(Char, Type::Int32Ty, "chari");
B.CreateCall2(F, Char, File, "fputc");
}
/// EmitFPutS - Emit a call to the puts function. Str is required to be a
/// pointer and File is a pointer to FILE.
void LibCallOptimization::EmitFPutS(Value *Str, Value *File, IRBuilder<> &B) {
Module *M = Caller->getParent();
Constant *F = M->getOrInsertFunction("fputs", Type::Int32Ty,
PointerType::getUnqual(Type::Int8Ty),
File->getType(), NULL);
B.CreateCall2(F, CastToCStr(Str, B), File, "fputs");
}
/// EmitFWrite - Emit a call to the fwrite function. This assumes that Ptr is
/// a pointer, Size is an 'intptr_t', and File is a pointer to FILE.
void LibCallOptimization::EmitFWrite(Value *Ptr, Value *Size, Value *File,
IRBuilder<> &B) {
Module *M = Caller->getParent();
Constant *F = M->getOrInsertFunction("fwrite", TD->getIntPtrType(),
PointerType::getUnqual(Type::Int8Ty),
TD->getIntPtrType(), TD->getIntPtrType(),
File->getType(), NULL);
B.CreateCall4(F, CastToCStr(Ptr, B), Size,
ConstantInt::get(TD->getIntPtrType(), 1), File);
}
//===----------------------------------------------------------------------===//
// Helper Functions
//===----------------------------------------------------------------------===//
/// GetStringLengthH - If we can compute the length of the string pointed to by
/// the specified pointer, return 'len+1'. If we can't, return 0.
static uint64_t GetStringLengthH(Value *V, SmallPtrSet<PHINode*, 32> &PHIs) {
// Look through noop bitcast instructions.
if (BitCastInst *BCI = dyn_cast<BitCastInst>(V))
return GetStringLengthH(BCI->getOperand(0), PHIs);
// If this is a PHI node, there are two cases: either we have already seen it
// or we haven't.
if (PHINode *PN = dyn_cast<PHINode>(V)) {
if (!PHIs.insert(PN))
return ~0ULL; // already in the set.
// If it was new, see if all the input strings are the same length.
uint64_t LenSoFar = ~0ULL;
for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
uint64_t Len = GetStringLengthH(PN->getIncomingValue(i), PHIs);
if (Len == 0) return 0; // Unknown length -> unknown.
if (Len == ~0ULL) continue;
if (Len != LenSoFar && LenSoFar != ~0ULL)
return 0; // Disagree -> unknown.
LenSoFar = Len;
}
// Success, all agree.
return LenSoFar;
}
// strlen(select(c,x,y)) -> strlen(x) ^ strlen(y)
if (SelectInst *SI = dyn_cast<SelectInst>(V)) {
uint64_t Len1 = GetStringLengthH(SI->getTrueValue(), PHIs);
if (Len1 == 0) return 0;
uint64_t Len2 = GetStringLengthH(SI->getFalseValue(), PHIs);
if (Len2 == 0) return 0;
if (Len1 == ~0ULL) return Len2;
if (Len2 == ~0ULL) return Len1;
if (Len1 != Len2) return 0;
return Len1;
}
// If the value is not a GEP instruction nor a constant expression with a
// GEP instruction, then return unknown.
User *GEP = 0;
if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(V)) {
GEP = GEPI;
} else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) {
if (CE->getOpcode() != Instruction::GetElementPtr)
return 0;
GEP = CE;
} else {
return 0;
}
// Make sure the GEP has exactly three arguments.
if (GEP->getNumOperands() != 3)
return 0;
// Check to make sure that the first operand of the GEP is an integer and
// has value 0 so that we are sure we're indexing into the initializer.
if (ConstantInt *Idx = dyn_cast<ConstantInt>(GEP->getOperand(1))) {
if (!Idx->isZero())
return 0;
} else
return 0;
// If the second index isn't a ConstantInt, then this is a variable index
// into the array. If this occurs, we can't say anything meaningful about
// the string.
uint64_t StartIdx = 0;
if (ConstantInt *CI = dyn_cast<ConstantInt>(GEP->getOperand(2)))
StartIdx = CI->getZExtValue();
else
return 0;
// The GEP instruction, constant or instruction, must reference a global
// variable that is a constant and is initialized. The referenced constant
// initializer is the array that we'll use for optimization.
GlobalVariable* GV = dyn_cast<GlobalVariable>(GEP->getOperand(0));
if (!GV || !GV->isConstant() || !GV->hasInitializer())
return 0;
Constant *GlobalInit = GV->getInitializer();
// Handle the ConstantAggregateZero case, which is a degenerate case. The
// initializer is constant zero so the length of the string must be zero.
if (isa<ConstantAggregateZero>(GlobalInit))
return 1; // Len = 0 offset by 1.
// Must be a Constant Array
ConstantArray *Array = dyn_cast<ConstantArray>(GlobalInit);
if (!Array || Array->getType()->getElementType() != Type::Int8Ty)
return false;
// Get the number of elements in the array
uint64_t NumElts = Array->getType()->getNumElements();
// Traverse the constant array from StartIdx (derived above) which is
// the place the GEP refers to in the array.
for (unsigned i = StartIdx; i != NumElts; ++i) {
Constant *Elt = Array->getOperand(i);
ConstantInt *CI = dyn_cast<ConstantInt>(Elt);
if (!CI) // This array isn't suitable, non-int initializer.
return 0;
if (CI->isZero())
return i-StartIdx+1; // We found end of string, success!
}
return 0; // The array isn't null terminated, conservatively return 'unknown'.
}
/// GetStringLength - If we can compute the length of the string pointed to by
/// the specified pointer, return 'len+1'. If we can't, return 0.
static uint64_t GetStringLength(Value *V) {
if (!isa<PointerType>(V->getType())) return 0;
SmallPtrSet<PHINode*, 32> PHIs;
uint64_t Len = GetStringLengthH(V, PHIs);
// If Len is ~0ULL, we had an infinite phi cycle: this is dead code, so return
// an empty string as a length.
return Len == ~0ULL ? 1 : Len;
}
/// IsOnlyUsedInZeroEqualityComparison - Return true if it only matters that the
/// value is equal or not-equal to zero.
static bool IsOnlyUsedInZeroEqualityComparison(Value *V) {
for (Value::use_iterator UI = V->use_begin(), E = V->use_end();
UI != E; ++UI) {
if (ICmpInst *IC = dyn_cast<ICmpInst>(*UI))
if (IC->isEquality())
if (Constant *C = dyn_cast<Constant>(IC->getOperand(1)))
if (C->isNullValue())
continue;
// Unknown instruction.
return false;
}
return true;
}
//===----------------------------------------------------------------------===//
// Miscellaneous LibCall Optimizations
//===----------------------------------------------------------------------===//
namespace {
//===---------------------------------------===//
// 'exit' Optimizations
/// ExitOpt - int main() { exit(4); } --> int main() { return 4; }
struct VISIBILITY_HIDDEN ExitOpt : public LibCallOptimization {
virtual Value *CallOptimizer(Function *Callee, CallInst *CI, IRBuilder<> &B) {
// Verify we have a reasonable prototype for exit.
if (Callee->arg_size() == 0 || !CI->use_empty())
return 0;
// Verify the caller is main, and that the result type of main matches the
// argument type of exit.
if (!Caller->isName("main") || !Caller->hasExternalLinkage() ||
Caller->getReturnType() != CI->getOperand(1)->getType())
return 0;
TerminatorInst *OldTI = CI->getParent()->getTerminator();
// Create the return after the call.
ReturnInst *RI = B.CreateRet(CI->getOperand(1));
// Drop all successor phi node entries.
for (unsigned i = 0, e = OldTI->getNumSuccessors(); i != e; ++i)
OldTI->getSuccessor(i)->removePredecessor(CI->getParent());
// Erase all instructions from after our return instruction until the end of
// the block.
BasicBlock::iterator FirstDead = RI; ++FirstDead;
CI->getParent()->getInstList().erase(FirstDead, CI->getParent()->end());
return CI;
}
};
//===----------------------------------------------------------------------===//
// String and Memory LibCall Optimizations
//===----------------------------------------------------------------------===//
//===---------------------------------------===//
// 'strcat' Optimizations
struct VISIBILITY_HIDDEN StrCatOpt : public LibCallOptimization {
virtual Value *CallOptimizer(Function *Callee, CallInst *CI, IRBuilder<> &B) {
// Verify the "strcat" function prototype.
const FunctionType *FT = Callee->getFunctionType();
if (FT->getNumParams() != 2 ||
FT->getReturnType() != PointerType::getUnqual(Type::Int8Ty) ||
FT->getParamType(0) != FT->getReturnType() ||
FT->getParamType(1) != FT->getReturnType())
return 0;
// Extract some information from the instruction
Value *Dst = CI->getOperand(1);
Value *Src = CI->getOperand(2);
// See if we can get the length of the input string.
uint64_t Len = GetStringLength(Src);
if (Len == 0) return 0;
--Len; // Unbias length.
// Handle the simple, do-nothing case: strcat(x, "") -> x
if (Len == 0)
return Dst;
// We need to find the end of the destination string. That's where the
// memory is to be moved to. We just generate a call to strlen.
Value *DstLen = EmitStrLen(Dst, B);
// Now that we have the destination's length, we must index into the
// destination's pointer to get the actual memcpy destination (end of
// the string .. we're concatenating).
Dst = B.CreateGEP(Dst, DstLen, "endptr");
// We have enough information to now generate the memcpy call to do the
// concatenation for us. Make a memcpy to copy the nul byte with align = 1.
EmitMemCpy(Dst, Src, ConstantInt::get(TD->getIntPtrType(), Len+1), 1, B);
return Dst;
}
};
//===---------------------------------------===//
// 'strchr' Optimizations
struct VISIBILITY_HIDDEN StrChrOpt : public LibCallOptimization {
virtual Value *CallOptimizer(Function *Callee, CallInst *CI, IRBuilder<> &B) {
// Verify the "strchr" function prototype.
const FunctionType *FT = Callee->getFunctionType();
if (FT->getNumParams() != 2 ||
FT->getReturnType() != PointerType::getUnqual(Type::Int8Ty) ||
FT->getParamType(0) != FT->getReturnType())
return 0;
Value *SrcStr = CI->getOperand(1);
// If the second operand is non-constant, see if we can compute the length
// of the input string and turn this into memchr.
ConstantInt *CharC = dyn_cast<ConstantInt>(CI->getOperand(2));
if (CharC == 0) {
uint64_t Len = GetStringLength(SrcStr);
if (Len == 0 || FT->getParamType(1) != Type::Int32Ty) // memchr needs i32.
return 0;
return EmitMemChr(SrcStr, CI->getOperand(2), // include nul.
ConstantInt::get(TD->getIntPtrType(), Len), B);
}
// Otherwise, the character is a constant, see if the first argument is
// a string literal. If so, we can constant fold.
std::string Str;
if (!GetConstantStringInfo(SrcStr, Str))
return 0;
// strchr can find the nul character.
Str += '\0';
char CharValue = CharC->getSExtValue();
// Compute the offset.
uint64_t i = 0;
while (1) {
if (i == Str.size()) // Didn't find the char. strchr returns null.
return Constant::getNullValue(CI->getType());
// Did we find our match?
if (Str[i] == CharValue)
break;
++i;
}
// strchr(s+n,c) -> gep(s+n+i,c)
Value *Idx = ConstantInt::get(Type::Int64Ty, i);
return B.CreateGEP(SrcStr, Idx, "strchr");
}
};
//===---------------------------------------===//
// 'strcmp' Optimizations
struct VISIBILITY_HIDDEN StrCmpOpt : public LibCallOptimization {
virtual Value *CallOptimizer(Function *Callee, CallInst *CI, IRBuilder<> &B) {
// Verify the "strcmp" function prototype.
const FunctionType *FT = Callee->getFunctionType();
if (FT->getNumParams() != 2 || FT->getReturnType() != Type::Int32Ty ||
FT->getParamType(0) != FT->getParamType(1) ||
FT->getParamType(0) != PointerType::getUnqual(Type::Int8Ty))
return 0;
Value *Str1P = CI->getOperand(1), *Str2P = CI->getOperand(2);
if (Str1P == Str2P) // strcmp(x,x) -> 0
return ConstantInt::get(CI->getType(), 0);
std::string Str1, Str2;
bool HasStr1 = GetConstantStringInfo(Str1P, Str1);
bool HasStr2 = GetConstantStringInfo(Str2P, Str2);
if (HasStr1 && Str1.empty()) // strcmp("", x) -> *x
return B.CreateZExt(B.CreateLoad(Str2P, "strcmpload"), CI->getType());
if (HasStr2 && Str2.empty()) // strcmp(x,"") -> *x
return B.CreateZExt(B.CreateLoad(Str1P, "strcmpload"), CI->getType());
// strcmp(x, y) -> cnst (if both x and y are constant strings)
if (HasStr1 && HasStr2)
return ConstantInt::get(CI->getType(), strcmp(Str1.c_str(),Str2.c_str()));
// strcmp(P, "x") -> memcmp(P, "x", 2)
uint64_t Len1 = GetStringLength(Str1P);
uint64_t Len2 = GetStringLength(Str2P);
if (Len1 || Len2) {
// Choose the smallest Len excluding 0 which means 'unknown'.
if (!Len1 || (Len2 && Len2 < Len1))
Len1 = Len2;
return EmitMemCmp(Str1P, Str2P,
ConstantInt::get(TD->getIntPtrType(), Len1), B);
}
return 0;
}
};
//===---------------------------------------===//
// 'strncmp' Optimizations
struct VISIBILITY_HIDDEN StrNCmpOpt : public LibCallOptimization {
virtual Value *CallOptimizer(Function *Callee, CallInst *CI, IRBuilder<> &B) {
// Verify the "strncmp" function prototype.
const FunctionType *FT = Callee->getFunctionType();
if (FT->getNumParams() != 3 || FT->getReturnType() != Type::Int32Ty ||
FT->getParamType(0) != FT->getParamType(1) ||
FT->getParamType(0) != PointerType::getUnqual(Type::Int8Ty) ||
!isa<IntegerType>(FT->getParamType(2)))
return 0;
Value *Str1P = CI->getOperand(1), *Str2P = CI->getOperand(2);
if (Str1P == Str2P) // strncmp(x,x,n) -> 0
return ConstantInt::get(CI->getType(), 0);
// Get the length argument if it is constant.
uint64_t Length;
if (ConstantInt *LengthArg = dyn_cast<ConstantInt>(CI->getOperand(3)))
Length = LengthArg->getZExtValue();
else
return 0;
if (Length == 0) // strncmp(x,y,0) -> 0
return ConstantInt::get(CI->getType(), 0);
std::string Str1, Str2;
bool HasStr1 = GetConstantStringInfo(Str1P, Str1);
bool HasStr2 = GetConstantStringInfo(Str2P, Str2);
if (HasStr1 && Str1.empty()) // strncmp("", x, n) -> *x
return B.CreateZExt(B.CreateLoad(Str2P, "strcmpload"), CI->getType());
if (HasStr2 && Str2.empty()) // strncmp(x, "", n) -> *x
return B.CreateZExt(B.CreateLoad(Str1P, "strcmpload"), CI->getType());
// strncmp(x, y) -> cnst (if both x and y are constant strings)
if (HasStr1 && HasStr2)
return ConstantInt::get(CI->getType(),
strncmp(Str1.c_str(), Str2.c_str(), Length));
return 0;
}
};
//===---------------------------------------===//
// 'strcpy' Optimizations
struct VISIBILITY_HIDDEN StrCpyOpt : public LibCallOptimization {
virtual Value *CallOptimizer(Function *Callee, CallInst *CI, IRBuilder<> &B) {
// Verify the "strcpy" function prototype.
const FunctionType *FT = Callee->getFunctionType();
if (FT->getNumParams() != 2 || FT->getReturnType() != FT->getParamType(0) ||
FT->getParamType(0) != FT->getParamType(1) ||
FT->getParamType(0) != PointerType::getUnqual(Type::Int8Ty))
return 0;
Value *Dst = CI->getOperand(1), *Src = CI->getOperand(2);
if (Dst == Src) // strcpy(x,x) -> x
return Src;
// See if we can get the length of the input string.
uint64_t Len = GetStringLength(Src);
if (Len == 0) return 0;
// We have enough information to now generate the memcpy call to do the
// concatenation for us. Make a memcpy to copy the nul byte with align = 1.
EmitMemCpy(Dst, Src, ConstantInt::get(TD->getIntPtrType(), Len), 1, B);
return Dst;
}
};
//===---------------------------------------===//
// 'strlen' Optimizations
struct VISIBILITY_HIDDEN StrLenOpt : public LibCallOptimization {
virtual Value *CallOptimizer(Function *Callee, CallInst *CI, IRBuilder<> &B) {
const FunctionType *FT = Callee->getFunctionType();
if (FT->getNumParams() != 1 ||
FT->getParamType(0) != PointerType::getUnqual(Type::Int8Ty) ||
!isa<IntegerType>(FT->getReturnType()))
return 0;
Value *Src = CI->getOperand(1);
// Constant folding: strlen("xyz") -> 3
if (uint64_t Len = GetStringLength(Src))
return ConstantInt::get(CI->getType(), Len-1);
// Handle strlen(p) != 0.
if (!IsOnlyUsedInZeroEqualityComparison(CI)) return 0;
// strlen(x) != 0 --> *x != 0
// strlen(x) == 0 --> *x == 0
return B.CreateZExt(B.CreateLoad(Src, "strlenfirst"), CI->getType());
}
};
//===---------------------------------------===//
// 'memcmp' Optimizations
struct VISIBILITY_HIDDEN MemCmpOpt : public LibCallOptimization {
virtual Value *CallOptimizer(Function *Callee, CallInst *CI, IRBuilder<> &B) {
const FunctionType *FT = Callee->getFunctionType();
if (FT->getNumParams() != 3 || !isa<PointerType>(FT->getParamType(0)) ||
!isa<PointerType>(FT->getParamType(1)) ||
FT->getReturnType() != Type::Int32Ty)
return 0;
Value *LHS = CI->getOperand(1), *RHS = CI->getOperand(2);
if (LHS == RHS) // memcmp(s,s,x) -> 0
return Constant::getNullValue(CI->getType());
// Make sure we have a constant length.
ConstantInt *LenC = dyn_cast<ConstantInt>(CI->getOperand(3));
if (!LenC) return 0;
uint64_t Len = LenC->getZExtValue();
if (Len == 0) // memcmp(s1,s2,0) -> 0
return Constant::getNullValue(CI->getType());
if (Len == 1) { // memcmp(S1,S2,1) -> *LHS - *RHS
Value *LHSV = B.CreateLoad(CastToCStr(LHS, B), "lhsv");
Value *RHSV = B.CreateLoad(CastToCStr(RHS, B), "rhsv");
return B.CreateZExt(B.CreateSub(LHSV, RHSV, "chardiff"), CI->getType());
}
// memcmp(S1,S2,2) != 0 -> (*(short*)LHS ^ *(short*)RHS) != 0
// memcmp(S1,S2,4) != 0 -> (*(int*)LHS ^ *(int*)RHS) != 0
if ((Len == 2 || Len == 4) && IsOnlyUsedInZeroEqualityComparison(CI)) {
const Type *PTy = PointerType::getUnqual(Len == 2 ?
Type::Int16Ty : Type::Int32Ty);
LHS = B.CreateBitCast(LHS, PTy, "tmp");
RHS = B.CreateBitCast(RHS, PTy, "tmp");
LoadInst *LHSV = B.CreateLoad(LHS, "lhsv");
LoadInst *RHSV = B.CreateLoad(RHS, "rhsv");
LHSV->setAlignment(1); RHSV->setAlignment(1); // Unaligned loads.
return B.CreateZExt(B.CreateXor(LHSV, RHSV, "shortdiff"), CI->getType());
}
return 0;
}
};
//===---------------------------------------===//
// 'memcpy' Optimizations
struct VISIBILITY_HIDDEN MemCpyOpt : public LibCallOptimization {
virtual Value *CallOptimizer(Function *Callee, CallInst *CI, IRBuilder<> &B) {
const FunctionType *FT = Callee->getFunctionType();
if (FT->getNumParams() != 3 || FT->getReturnType() != FT->getParamType(0) ||
!isa<PointerType>(FT->getParamType(0)) ||
!isa<PointerType>(FT->getParamType(1)) ||
FT->getParamType(2) != TD->getIntPtrType())
return 0;
// memcpy(x, y, n) -> llvm.memcpy(x, y, n, 1)
EmitMemCpy(CI->getOperand(1), CI->getOperand(2), CI->getOperand(3), 1, B);
return CI->getOperand(1);
}
};
//===---------------------------------------===//
// 'memmove' Optimizations
struct VISIBILITY_HIDDEN MemMoveOpt : public LibCallOptimization {
virtual Value *CallOptimizer(Function *Callee, CallInst *CI, IRBuilder<> &B) {
const FunctionType *FT = Callee->getFunctionType();
if (FT->getNumParams() != 3 || FT->getReturnType() != FT->getParamType(0) ||
!isa<PointerType>(FT->getParamType(0)) ||
!isa<PointerType>(FT->getParamType(1)) ||
FT->getParamType(2) != TD->getIntPtrType())
return 0;
// memmove(x, y, n) -> llvm.memmove(x, y, n, 1)
Module *M = Caller->getParent();
Intrinsic::ID IID = Intrinsic::memmove;
const Type *Tys[1];
Tys[0] = TD->getIntPtrType();
Value *MemMove = Intrinsic::getDeclaration(M, IID, Tys, 1);
Value *Dst = CastToCStr(CI->getOperand(1), B);
Value *Src = CastToCStr(CI->getOperand(2), B);
Value *Size = CI->getOperand(3);
Value *Align = ConstantInt::get(Type::Int32Ty, 1);
B.CreateCall4(MemMove, Dst, Src, Size, Align);
return CI->getOperand(1);
}
};
//===---------------------------------------===//
// 'memset' Optimizations
struct VISIBILITY_HIDDEN MemSetOpt : public LibCallOptimization {
virtual Value *CallOptimizer(Function *Callee, CallInst *CI, IRBuilder<> &B) {
const FunctionType *FT = Callee->getFunctionType();
if (FT->getNumParams() != 3 || FT->getReturnType() != FT->getParamType(0) ||
!isa<PointerType>(FT->getParamType(0)) ||
FT->getParamType(1) != TD->getIntPtrType() ||
FT->getParamType(2) != TD->getIntPtrType())
return 0;
// memset(p, v, n) -> llvm.memset(p, v, n, 1)
Module *M = Caller->getParent();
Intrinsic::ID IID = Intrinsic::memset;
const Type *Tys[1];
Tys[0] = TD->getIntPtrType();
Value *MemSet = Intrinsic::getDeclaration(M, IID, Tys, 1);
Value *Dst = CastToCStr(CI->getOperand(1), B);
Value *Val = B.CreateTrunc(CI->getOperand(2), Type::Int8Ty);
Value *Size = CI->getOperand(3);
Value *Align = ConstantInt::get(Type::Int32Ty, 1);
B.CreateCall4(MemSet, Dst, Val, Size, Align);
return CI->getOperand(1);
}
};
//===----------------------------------------------------------------------===//
// Math Library Optimizations
//===----------------------------------------------------------------------===//
//===---------------------------------------===//
// 'pow*' Optimizations
struct VISIBILITY_HIDDEN PowOpt : public LibCallOptimization {
virtual Value *CallOptimizer(Function *Callee, CallInst *CI, IRBuilder<> &B) {
const FunctionType *FT = Callee->getFunctionType();
// Just make sure this has 2 arguments of the same FP type, which match the
// result type.
if (FT->getNumParams() != 2 || FT->getReturnType() != FT->getParamType(0) ||
FT->getParamType(0) != FT->getParamType(1) ||
!FT->getParamType(0)->isFloatingPoint())
return 0;
Value *Op1 = CI->getOperand(1), *Op2 = CI->getOperand(2);
if (ConstantFP *Op1C = dyn_cast<ConstantFP>(Op1)) {
if (Op1C->isExactlyValue(1.0)) // pow(1.0, x) -> 1.0
return Op1C;
if (Op1C->isExactlyValue(2.0)) // pow(2.0, x) -> exp2(x)
return EmitUnaryFloatFnCall(Op2, "exp2", B);
}
ConstantFP *Op2C = dyn_cast<ConstantFP>(Op2);
if (Op2C == 0) return 0;
if (Op2C->getValueAPF().isZero()) // pow(x, 0.0) -> 1.0
return ConstantFP::get(CI->getType(), 1.0);
if (Op2C->isExactlyValue(0.5)) {
// FIXME: This is not safe for -0.0 and -inf. This can only be done when
// 'unsafe' math optimizations are allowed.
// x pow(x, 0.5) sqrt(x)
// ---------------------------------------------
// -0.0 +0.0 -0.0
// -inf +inf NaN
#if 0
// pow(x, 0.5) -> sqrt(x)
return B.CreateCall(get_sqrt(), Op1, "sqrt");
#endif
}
if (Op2C->isExactlyValue(1.0)) // pow(x, 1.0) -> x
return Op1;
if (Op2C->isExactlyValue(2.0)) // pow(x, 2.0) -> x*x
return B.CreateMul(Op1, Op1, "pow2");
if (Op2C->isExactlyValue(-1.0)) // pow(x, -1.0) -> 1.0/x
return B.CreateFDiv(ConstantFP::get(CI->getType(), 1.0), Op1, "powrecip");
return 0;
}
};
//===---------------------------------------===//
// 'exp2' Optimizations
struct VISIBILITY_HIDDEN Exp2Opt : public LibCallOptimization {
virtual Value *CallOptimizer(Function *Callee, CallInst *CI, IRBuilder<> &B) {
const FunctionType *FT = Callee->getFunctionType();
// Just make sure this has 1 argument of FP type, which matches the
// result type.
if (FT->getNumParams() != 1 || FT->getReturnType() != FT->getParamType(0) ||
!FT->getParamType(0)->isFloatingPoint())
return 0;
Value *Op = CI->getOperand(1);
// Turn exp2(sitofp(x)) -> ldexp(1.0, sext(x)) if sizeof(x) <= 32
// Turn exp2(uitofp(x)) -> ldexp(1.0, zext(x)) if sizeof(x) < 32
Value *LdExpArg = 0;
if (SIToFPInst *OpC = dyn_cast<SIToFPInst>(Op)) {
if (OpC->getOperand(0)->getType()->getPrimitiveSizeInBits() <= 32)
LdExpArg = B.CreateSExt(OpC->getOperand(0), Type::Int32Ty, "tmp");
} else if (UIToFPInst *OpC = dyn_cast<UIToFPInst>(Op)) {
if (OpC->getOperand(0)->getType()->getPrimitiveSizeInBits() < 32)
LdExpArg = B.CreateZExt(OpC->getOperand(0), Type::Int32Ty, "tmp");
}
if (LdExpArg) {
const char *Name;
if (Op->getType() == Type::FloatTy)
Name = "ldexpf";
else if (Op->getType() == Type::DoubleTy)
Name = "ldexp";
else
Name = "ldexpl";
Constant *One = ConstantFP::get(APFloat(1.0f));
if (Op->getType() != Type::FloatTy)
One = ConstantExpr::getFPExtend(One, Op->getType());
Module *M = Caller->getParent();
Value *Callee = M->getOrInsertFunction(Name, Op->getType(),
Op->getType(), Type::Int32Ty,NULL);
return B.CreateCall2(Callee, One, LdExpArg);
}
return 0;
}
};
//===---------------------------------------===//
// Double -> Float Shrinking Optimizations for Unary Functions like 'floor'
struct VISIBILITY_HIDDEN UnaryDoubleFPOpt : public LibCallOptimization {
virtual Value *CallOptimizer(Function *Callee, CallInst *CI, IRBuilder<> &B) {
const FunctionType *FT = Callee->getFunctionType();
if (FT->getNumParams() != 1 || FT->getReturnType() != Type::DoubleTy ||
FT->getParamType(0) != Type::DoubleTy)
return 0;
// If this is something like 'floor((double)floatval)', convert to floorf.
FPExtInst *Cast = dyn_cast<FPExtInst>(CI->getOperand(1));
if (Cast == 0 || Cast->getOperand(0)->getType() != Type::FloatTy)
return 0;
// floor((double)floatval) -> (double)floorf(floatval)
Value *V = Cast->getOperand(0);
V = EmitUnaryFloatFnCall(V, Callee->getNameStart(), B);
return B.CreateFPExt(V, Type::DoubleTy);
}
};
//===----------------------------------------------------------------------===//
// Integer Optimizations
//===----------------------------------------------------------------------===//
//===---------------------------------------===//
// 'ffs*' Optimizations
struct VISIBILITY_HIDDEN FFSOpt : public LibCallOptimization {
virtual Value *CallOptimizer(Function *Callee, CallInst *CI, IRBuilder<> &B) {
const FunctionType *FT = Callee->getFunctionType();
// Just make sure this has 2 arguments of the same FP type, which match the
// result type.
if (FT->getNumParams() != 1 || FT->getReturnType() != Type::Int32Ty ||
!isa<IntegerType>(FT->getParamType(0)))
return 0;
Value *Op = CI->getOperand(1);
// Constant fold.
if (ConstantInt *CI = dyn_cast<ConstantInt>(Op)) {
if (CI->getValue() == 0) // ffs(0) -> 0.
return Constant::getNullValue(CI->getType());
return ConstantInt::get(Type::Int32Ty, // ffs(c) -> cttz(c)+1
CI->getValue().countTrailingZeros()+1);
}
// ffs(x) -> x != 0 ? (i32)llvm.cttz(x)+1 : 0
const Type *ArgType = Op->getType();
Value *F = Intrinsic::getDeclaration(Callee->getParent(),
Intrinsic::cttz, &ArgType, 1);
Value *V = B.CreateCall(F, Op, "cttz");
V = B.CreateAdd(V, ConstantInt::get(Type::Int32Ty, 1), "tmp");
V = B.CreateIntCast(V, Type::Int32Ty, false, "tmp");
Value *Cond = B.CreateICmpNE(Op, Constant::getNullValue(ArgType), "tmp");
return B.CreateSelect(Cond, V, ConstantInt::get(Type::Int32Ty, 0));
}
};
//===---------------------------------------===//
// 'isdigit' Optimizations
struct VISIBILITY_HIDDEN IsDigitOpt : public LibCallOptimization {
virtual Value *CallOptimizer(Function *Callee, CallInst *CI, IRBuilder<> &B) {
const FunctionType *FT = Callee->getFunctionType();
// We require integer(i32)
if (FT->getNumParams() != 1 || !isa<IntegerType>(FT->getReturnType()) ||
FT->getParamType(0) != Type::Int32Ty)
return 0;
// isdigit(c) -> (c-'0') <u 10
Value *Op = CI->getOperand(1);
Op = B.CreateSub(Op, ConstantInt::get(Type::Int32Ty, '0'), "isdigittmp");
Op = B.CreateICmpULT(Op, ConstantInt::get(Type::Int32Ty, 10), "isdigit");
return B.CreateZExt(Op, CI->getType());
}
};
//===---------------------------------------===//
// 'isascii' Optimizations
struct VISIBILITY_HIDDEN IsAsciiOpt : public LibCallOptimization {
virtual Value *CallOptimizer(Function *Callee, CallInst *CI, IRBuilder<> &B) {
const FunctionType *FT = Callee->getFunctionType();
// We require integer(i32)
if (FT->getNumParams() != 1 || !isa<IntegerType>(FT->getReturnType()) ||
FT->getParamType(0) != Type::Int32Ty)
return 0;
// isascii(c) -> c <u 128
Value *Op = CI->getOperand(1);
Op = B.CreateICmpULT(Op, ConstantInt::get(Type::Int32Ty, 128), "isascii");
return B.CreateZExt(Op, CI->getType());
}
};
//===---------------------------------------===//
// 'abs', 'labs', 'llabs' Optimizations
struct VISIBILITY_HIDDEN AbsOpt : public LibCallOptimization {
virtual Value *CallOptimizer(Function *Callee, CallInst *CI, IRBuilder<> &B) {
const FunctionType *FT = Callee->getFunctionType();
// We require integer(integer) where the types agree.
if (FT->getNumParams() != 1 || !isa<IntegerType>(FT->getReturnType()) ||
FT->getParamType(0) != FT->getReturnType())
return 0;
// abs(x) -> x >s -1 ? x : -x
Value *Op = CI->getOperand(1);
Value *Pos = B.CreateICmpSGT(Op,ConstantInt::getAllOnesValue(Op->getType()),
"ispos");
Value *Neg = B.CreateNeg(Op, "neg");
return B.CreateSelect(Pos, Op, Neg);
}
};
//===---------------------------------------===//
// 'toascii' Optimizations
struct VISIBILITY_HIDDEN ToAsciiOpt : public LibCallOptimization {
virtual Value *CallOptimizer(Function *Callee, CallInst *CI, IRBuilder<> &B) {
const FunctionType *FT = Callee->getFunctionType();
// We require i32(i32)
if (FT->getNumParams() != 1 || FT->getReturnType() != FT->getParamType(0) ||
FT->getParamType(0) != Type::Int32Ty)
return 0;
// isascii(c) -> c & 0x7f
return B.CreateAnd(CI->getOperand(1), ConstantInt::get(CI->getType(),0x7F));
}
};
//===----------------------------------------------------------------------===//
// Formatting and IO Optimizations
//===----------------------------------------------------------------------===//
//===---------------------------------------===//
// 'printf' Optimizations
struct VISIBILITY_HIDDEN PrintFOpt : public LibCallOptimization {
virtual Value *CallOptimizer(Function *Callee, CallInst *CI, IRBuilder<> &B) {
// Require one fixed pointer argument and an integer/void result.
const FunctionType *FT = Callee->getFunctionType();
if (FT->getNumParams() < 1 || !isa<PointerType>(FT->getParamType(0)) ||
!(isa<IntegerType>(FT->getReturnType()) ||
FT->getReturnType() == Type::VoidTy))
return 0;
// Check for a fixed format string.
std::string FormatStr;
if (!GetConstantStringInfo(CI->getOperand(1), FormatStr))
return 0;
// Empty format string -> noop.
if (FormatStr.empty()) // Tolerate printf's declared void.
return CI->use_empty() ? (Value*)CI : ConstantInt::get(CI->getType(), 0);
// printf("x") -> putchar('x'), even for '%'.
if (FormatStr.size() == 1) {
EmitPutChar(ConstantInt::get(Type::Int32Ty, FormatStr[0]), B);
return CI->use_empty() ? (Value*)CI : ConstantInt::get(CI->getType(), 1);
}
// printf("foo\n") --> puts("foo")
if (FormatStr[FormatStr.size()-1] == '\n' &&
FormatStr.find('%') == std::string::npos) { // no format characters.
// Create a string literal with no \n on it. We expect the constant merge
// pass to be run after this pass, to merge duplicate strings.
FormatStr.erase(FormatStr.end()-1);
Constant *C = ConstantArray::get(FormatStr, true);
C = new GlobalVariable(C->getType(), true,GlobalVariable::InternalLinkage,
C, "str", Callee->getParent());
EmitPutS(C, B);
return CI->use_empty() ? (Value*)CI :
ConstantInt::get(CI->getType(), FormatStr.size()+1);
}
// Optimize specific format strings.
// printf("%c", chr) --> putchar(*(i8*)dst)
if (FormatStr == "%c" && CI->getNumOperands() > 2 &&
isa<IntegerType>(CI->getOperand(2)->getType())) {
EmitPutChar(CI->getOperand(2), B);
return CI->use_empty() ? (Value*)CI : ConstantInt::get(CI->getType(), 1);
}
// printf("%s\n", str) --> puts(str)
if (FormatStr == "%s\n" && CI->getNumOperands() > 2 &&
isa<PointerType>(CI->getOperand(2)->getType()) &&
CI->use_empty()) {
EmitPutS(CI->getOperand(2), B);
return CI;
}
return 0;
}
};
//===---------------------------------------===//
// 'sprintf' Optimizations
struct VISIBILITY_HIDDEN SPrintFOpt : public LibCallOptimization {
virtual Value *CallOptimizer(Function *Callee, CallInst *CI, IRBuilder<> &B) {
// Require two fixed pointer arguments and an integer result.
const FunctionType *FT = Callee->getFunctionType();
if (FT->getNumParams() != 2 || !isa<PointerType>(FT->getParamType(0)) ||
!isa<PointerType>(FT->getParamType(1)) ||
!isa<IntegerType>(FT->getReturnType()))
return 0;
// Check for a fixed format string.
std::string FormatStr;
if (!GetConstantStringInfo(CI->getOperand(2), FormatStr))
return 0;
// If we just have a format string (nothing else crazy) transform it.
if (CI->getNumOperands() == 3) {
// Make sure there's no % in the constant array. We could try to handle
// %% -> % in the future if we cared.
for (unsigned i = 0, e = FormatStr.size(); i != e; ++i)
if (FormatStr[i] == '%')
return 0; // we found a format specifier, bail out.
// sprintf(str, fmt) -> llvm.memcpy(str, fmt, strlen(fmt)+1, 1)
EmitMemCpy(CI->getOperand(1), CI->getOperand(2), // Copy the nul byte.
ConstantInt::get(TD->getIntPtrType(), FormatStr.size()+1),1,B);
return ConstantInt::get(CI->getType(), FormatStr.size());
}
// The remaining optimizations require the format string to be "%s" or "%c"
// and have an extra operand.
if (FormatStr.size() != 2 || FormatStr[0] != '%' || CI->getNumOperands() <4)
return 0;
// Decode the second character of the format string.
if (FormatStr[1] == 'c') {
// sprintf(dst, "%c", chr) --> *(i8*)dst = chr; *((i8*)dst+1) = 0
if (!isa<IntegerType>(CI->getOperand(3)->getType())) return 0;
Value *V = B.CreateTrunc(CI->getOperand(3), Type::Int8Ty, "char");
Value *Ptr = CastToCStr(CI->getOperand(1), B);
B.CreateStore(V, Ptr);
Ptr = B.CreateGEP(Ptr, ConstantInt::get(Type::Int32Ty, 1), "nul");
B.CreateStore(Constant::getNullValue(Type::Int8Ty), Ptr);
return ConstantInt::get(CI->getType(), 1);
}
if (FormatStr[1] == 's') {
// sprintf(dest, "%s", str) -> llvm.memcpy(dest, str, strlen(str)+1, 1)
if (!isa<PointerType>(CI->getOperand(3)->getType())) return 0;
Value *Len = EmitStrLen(CI->getOperand(3), B);
Value *IncLen = B.CreateAdd(Len, ConstantInt::get(Len->getType(), 1),
"leninc");
EmitMemCpy(CI->getOperand(1), CI->getOperand(3), IncLen, 1, B);
// The sprintf result is the unincremented number of bytes in the string.
return B.CreateIntCast(Len, CI->getType(), false);
}
return 0;
}
};
//===---------------------------------------===//
// 'fwrite' Optimizations
struct VISIBILITY_HIDDEN FWriteOpt : public LibCallOptimization {
virtual Value *CallOptimizer(Function *Callee, CallInst *CI, IRBuilder<> &B) {
// Require a pointer, an integer, an integer, a pointer, returning integer.
const FunctionType *FT = Callee->getFunctionType();
if (FT->getNumParams() != 4 || !isa<PointerType>(FT->getParamType(0)) ||
!isa<IntegerType>(FT->getParamType(1)) ||
!isa<IntegerType>(FT->getParamType(2)) ||
!isa<PointerType>(FT->getParamType(3)) ||
!isa<IntegerType>(FT->getReturnType()))
return 0;
// Get the element size and count.
ConstantInt *SizeC = dyn_cast<ConstantInt>(CI->getOperand(2));
ConstantInt *CountC = dyn_cast<ConstantInt>(CI->getOperand(3));
if (!SizeC || !CountC) return 0;
uint64_t Bytes = SizeC->getZExtValue()*CountC->getZExtValue();
// If this is writing zero records, remove the call (it's a noop).
if (Bytes == 0)
return ConstantInt::get(CI->getType(), 0);
// If this is writing one byte, turn it into fputc.
if (Bytes == 1) { // fwrite(S,1,1,F) -> fputc(S[0],F)
Value *Char = B.CreateLoad(CastToCStr(CI->getOperand(1), B), "char");
EmitFPutC(Char, CI->getOperand(4), B);
return ConstantInt::get(CI->getType(), 1);
}
return 0;
}
};
//===---------------------------------------===//
// 'fputs' Optimizations
struct VISIBILITY_HIDDEN FPutsOpt : public LibCallOptimization {
virtual Value *CallOptimizer(Function *Callee, CallInst *CI, IRBuilder<> &B) {
// Require two pointers. Also, we can't optimize if return value is used.
const FunctionType *FT = Callee->getFunctionType();
if (FT->getNumParams() != 2 || !isa<PointerType>(FT->getParamType(0)) ||
!isa<PointerType>(FT->getParamType(1)) ||
!CI->use_empty())
return 0;
// fputs(s,F) --> fwrite(s,1,strlen(s),F)
uint64_t Len = GetStringLength(CI->getOperand(1));
if (!Len) return 0;
EmitFWrite(CI->getOperand(1), ConstantInt::get(TD->getIntPtrType(), Len-1),
CI->getOperand(2), B);
return CI; // Known to have no uses (see above).
}
};
//===---------------------------------------===//
// 'fprintf' Optimizations
struct VISIBILITY_HIDDEN FPrintFOpt : public LibCallOptimization {
virtual Value *CallOptimizer(Function *Callee, CallInst *CI, IRBuilder<> &B) {
// Require two fixed paramters as pointers and integer result.
const FunctionType *FT = Callee->getFunctionType();
if (FT->getNumParams() != 2 || !isa<PointerType>(FT->getParamType(0)) ||
!isa<PointerType>(FT->getParamType(1)) ||
!isa<IntegerType>(FT->getReturnType()))
return 0;
// All the optimizations depend on the format string.
std::string FormatStr;
if (!GetConstantStringInfo(CI->getOperand(2), FormatStr))
return 0;
// fprintf(F, "foo") --> fwrite("foo", 3, 1, F)
if (CI->getNumOperands() == 3) {
for (unsigned i = 0, e = FormatStr.size(); i != e; ++i)
if (FormatStr[i] == '%') // Could handle %% -> % if we cared.
return 0; // We found a format specifier.
EmitFWrite(CI->getOperand(2), ConstantInt::get(TD->getIntPtrType(),
FormatStr.size()),
CI->getOperand(1), B);
return ConstantInt::get(CI->getType(), FormatStr.size());
}
// The remaining optimizations require the format string to be "%s" or "%c"
// and have an extra operand.
if (FormatStr.size() != 2 || FormatStr[0] != '%' || CI->getNumOperands() <4)
return 0;
// Decode the second character of the format string.
if (FormatStr[1] == 'c') {
// fprintf(F, "%c", chr) --> *(i8*)dst = chr
if (!isa<IntegerType>(CI->getOperand(3)->getType())) return 0;
EmitFPutC(CI->getOperand(3), CI->getOperand(1), B);
return ConstantInt::get(CI->getType(), 1);
}
if (FormatStr[1] == 's') {
// fprintf(F, "%s", str) -> fputs(str, F)
if (!isa<PointerType>(CI->getOperand(3)->getType()) || !CI->use_empty())
return 0;
EmitFPutS(CI->getOperand(3), CI->getOperand(1), B);
return CI;
}
return 0;
}
};
} // end anonymous namespace.
//===----------------------------------------------------------------------===//
// SimplifyLibCalls Pass Implementation
//===----------------------------------------------------------------------===//
namespace {
/// This pass optimizes well known library functions from libc and libm.
///
class VISIBILITY_HIDDEN SimplifyLibCalls : public FunctionPass {
StringMap<LibCallOptimization*> Optimizations;
// Miscellaneous LibCall Optimizations
ExitOpt Exit;
// String and Memory LibCall Optimizations
StrCatOpt StrCat; StrChrOpt StrChr; StrCmpOpt StrCmp; StrNCmpOpt StrNCmp;
StrCpyOpt StrCpy; StrLenOpt StrLen; MemCmpOpt MemCmp; MemCpyOpt MemCpy;
MemMoveOpt MemMove; MemSetOpt MemSet;
// Math Library Optimizations
PowOpt Pow; Exp2Opt Exp2; UnaryDoubleFPOpt UnaryDoubleFP;
// Integer Optimizations
FFSOpt FFS; AbsOpt Abs; IsDigitOpt IsDigit; IsAsciiOpt IsAscii;
ToAsciiOpt ToAscii;
// Formatting and IO Optimizations
SPrintFOpt SPrintF; PrintFOpt PrintF;
FWriteOpt FWrite; FPutsOpt FPuts; FPrintFOpt FPrintF;
public:
static char ID; // Pass identification
SimplifyLibCalls() : FunctionPass(&ID) {}
void InitOptimizations();
bool runOnFunction(Function &F);
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
AU.addRequired<TargetData>();
}
};
char SimplifyLibCalls::ID = 0;
} // end anonymous namespace.
static RegisterPass<SimplifyLibCalls>
X("simplify-libcalls", "Simplify well-known library calls");
// Public interface to the Simplify LibCalls pass.
FunctionPass *llvm::createSimplifyLibCallsPass() {
return new SimplifyLibCalls();
}
/// Optimizations - Populate the Optimizations map with all the optimizations
/// we know.
void SimplifyLibCalls::InitOptimizations() {
// Miscellaneous LibCall Optimizations
Optimizations["exit"] = &Exit;
// String and Memory LibCall Optimizations
Optimizations["strcat"] = &StrCat;
Optimizations["strchr"] = &StrChr;
Optimizations["strcmp"] = &StrCmp;
Optimizations["strncmp"] = &StrNCmp;
Optimizations["strcpy"] = &StrCpy;
Optimizations["strlen"] = &StrLen;
Optimizations["memcmp"] = &MemCmp;
Optimizations["memcpy"] = &MemCpy;
Optimizations["memmove"] = &MemMove;
Optimizations["memset"] = &MemSet;
// Math Library Optimizations
Optimizations["powf"] = &Pow;
Optimizations["pow"] = &Pow;
Optimizations["powl"] = &Pow;
Optimizations["llvm.pow.f32"] = &Pow;
Optimizations["llvm.pow.f64"] = &Pow;
Optimizations["llvm.pow.f80"] = &Pow;
Optimizations["llvm.pow.f128"] = &Pow;
Optimizations["llvm.pow.ppcf128"] = &Pow;
Optimizations["exp2l"] = &Exp2;
Optimizations["exp2"] = &Exp2;
Optimizations["exp2f"] = &Exp2;
Optimizations["llvm.exp2.ppcf128"] = &Exp2;
Optimizations["llvm.exp2.f128"] = &Exp2;
Optimizations["llvm.exp2.f80"] = &Exp2;
Optimizations["llvm.exp2.f64"] = &Exp2;
Optimizations["llvm.exp2.f32"] = &Exp2;
#ifdef HAVE_FLOORF
Optimizations["floor"] = &UnaryDoubleFP;
#endif
#ifdef HAVE_CEILF
Optimizations["ceil"] = &UnaryDoubleFP;
#endif
#ifdef HAVE_ROUNDF
Optimizations["round"] = &UnaryDoubleFP;
#endif
#ifdef HAVE_RINTF
Optimizations["rint"] = &UnaryDoubleFP;
#endif
#ifdef HAVE_NEARBYINTF
Optimizations["nearbyint"] = &UnaryDoubleFP;
#endif
// Integer Optimizations
Optimizations["ffs"] = &FFS;
Optimizations["ffsl"] = &FFS;
Optimizations["ffsll"] = &FFS;
Optimizations["abs"] = &Abs;
Optimizations["labs"] = &Abs;
Optimizations["llabs"] = &Abs;
Optimizations["isdigit"] = &IsDigit;
Optimizations["isascii"] = &IsAscii;
Optimizations["toascii"] = &ToAscii;
// Formatting and IO Optimizations
Optimizations["sprintf"] = &SPrintF;
Optimizations["printf"] = &PrintF;
Optimizations["fwrite"] = &FWrite;
Optimizations["fputs"] = &FPuts;
Optimizations["fprintf"] = &FPrintF;
}
/// runOnFunction - Top level algorithm.
///
bool SimplifyLibCalls::runOnFunction(Function &F) {
if (Optimizations.empty())
InitOptimizations();
const TargetData &TD = getAnalysis<TargetData>();
IRBuilder<> Builder;
bool Changed = false;
for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB) {
for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ) {
// Ignore non-calls.
CallInst *CI = dyn_cast<CallInst>(I++);
if (!CI) continue;
// Ignore indirect calls and calls to non-external functions.
Function *Callee = CI->getCalledFunction();
if (Callee == 0 || !Callee->isDeclaration() ||
!(Callee->hasExternalLinkage() || Callee->hasDLLImportLinkage()))
continue;
// Ignore unknown calls.
const char *CalleeName = Callee->getNameStart();
StringMap<LibCallOptimization*>::iterator OMI =
Optimizations.find(CalleeName, CalleeName+Callee->getNameLen());
if (OMI == Optimizations.end()) continue;
// Set the builder to the instruction after the call.
Builder.SetInsertPoint(BB, I);
// Try to optimize this call.
Value *Result = OMI->second->OptimizeCall(CI, TD, Builder);
if (Result == 0) continue;
DEBUG(DOUT << "SimplifyLibCalls simplified: " << *CI;
DOUT << " into: " << *Result << "\n");
// Something changed!
Changed = true;
++NumSimplified;
// Inspect the instruction after the call (which was potentially just
// added) next.
I = CI; ++I;
if (CI != Result && !CI->use_empty()) {
CI->replaceAllUsesWith(Result);
if (!Result->hasName())
Result->takeName(CI);
}
CI->eraseFromParent();
}
}
return Changed;
}
// TODO:
// Additional cases that we need to add to this file:
//
// cbrt:
// * cbrt(expN(X)) -> expN(x/3)
// * cbrt(sqrt(x)) -> pow(x,1/6)
// * cbrt(sqrt(x)) -> pow(x,1/9)
//
// cos, cosf, cosl:
// * cos(-x) -> cos(x)
//
// exp, expf, expl:
// * exp(log(x)) -> x
//
// log, logf, logl:
// * log(exp(x)) -> x
// * log(x**y) -> y*log(x)
// * log(exp(y)) -> y*log(e)
// * log(exp2(y)) -> y*log(2)
// * log(exp10(y)) -> y*log(10)
// * log(sqrt(x)) -> 0.5*log(x)
// * log(pow(x,y)) -> y*log(x)
//
// lround, lroundf, lroundl:
// * lround(cnst) -> cnst'
//
// memcmp:
// * memcmp(x,y,l) -> cnst
// (if all arguments are constant and strlen(x) <= l and strlen(y) <= l)
//
// pow, powf, powl:
// * pow(exp(x),y) -> exp(x*y)
// * pow(sqrt(x),y) -> pow(x,y*0.5)
// * pow(pow(x,y),z)-> pow(x,y*z)
//
// puts:
// * puts("") -> putchar("\n")
//
// round, roundf, roundl:
// * round(cnst) -> cnst'
//
// signbit:
// * signbit(cnst) -> cnst'
// * signbit(nncst) -> 0 (if pstv is a non-negative constant)
//
// sqrt, sqrtf, sqrtl:
// * sqrt(expN(x)) -> expN(x*0.5)
// * sqrt(Nroot(x)) -> pow(x,1/(2*N))
// * sqrt(pow(x,y)) -> pow(|x|,y*0.5)
//
// stpcpy:
// * stpcpy(str, "literal") ->
// llvm.memcpy(str,"literal",strlen("literal")+1,1)
// strrchr:
// * strrchr(s,c) -> reverse_offset_of_in(c,s)
// (if c is a constant integer and s is a constant string)
// * strrchr(s1,0) -> strchr(s1,0)
//
// strncat:
// * strncat(x,y,0) -> x
// * strncat(x,y,0) -> x (if strlen(y) = 0)
// * strncat(x,y,l) -> strcat(x,y) (if y and l are constants an l > strlen(y))
//
// strncpy:
// * strncpy(d,s,0) -> d
// * strncpy(d,s,l) -> memcpy(d,s,l,1)
// (if s and l are constants)
//
// strpbrk:
// * strpbrk(s,a) -> offset_in_for(s,a)
// (if s and a are both constant strings)
// * strpbrk(s,"") -> 0
// * strpbrk(s,a) -> strchr(s,a[0]) (if a is constant string of length 1)
//
// strspn, strcspn:
// * strspn(s,a) -> const_int (if both args are constant)
// * strspn("",a) -> 0
// * strspn(s,"") -> 0
// * strcspn(s,a) -> const_int (if both args are constant)
// * strcspn("",a) -> 0
// * strcspn(s,"") -> strlen(a)
//
// strstr:
// * strstr(x,x) -> x
// * strstr(s1,s2) -> offset_of_s2_in(s1)
// (if s1 and s2 are constant strings)
//
// tan, tanf, tanl:
// * tan(atan(x)) -> x
//
// trunc, truncf, truncl:
// * trunc(cnst) -> cnst'
//
//
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