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- Re-apply 52748 and friends with fix. GetConstantStringInfo() returns an empty string for ConstantAggregateZero case which surprises selectiondag.

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- Correctly handle memcpy from constant string which is zero-initialized.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@52891 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Evan Cheng 2008-06-30 07:31:25 +00:00
parent 2ca698df93
commit 0ff39b3feb
11 changed files with 168 additions and 174 deletions
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11
include/llvm/Analysis/ValueTracking.h
View File

@ -72,7 +72,16 @@ namespace llvm {
Instruction *InsertBefore = 0) {
const unsigned Idxs[1] = { Idx };
return FindInsertedValue(V, &Idxs[0], &Idxs[1], InsertBefore);
}
}
/// GetConstantStringInfo - This function computes the length of a
/// null-terminated C string pointed to by V. If successful, it returns true
/// and returns the string in Str. If unsuccessful, it returns false. If
/// StopAtNul is set to true (the default), the returned string is truncated
/// by a nul character in the global. If StopAtNul is false, the nul
/// character is included in the result string.
bool GetConstantStringInfo(Value *V, std::string &Str, uint64_t Offset = 0,
bool StopAtNul = true);
} // end namespace llvm
#endif

7
include/llvm/Constant.h
View File

@ -115,13 +115,6 @@ public:
"implemented for all constants that have operands!");
assert(0 && "Constants that do not have operands cannot be using 'From'!");
}
/// getStringValue - Turn an LLVM constant pointer that eventually points to a
/// global into a string value. Return an empty string if we can't do it.
/// Parameter Chop determines if the result is chopped at the first null
/// terminator.
///
std::string getStringValue(bool Chop = true, unsigned Offset = 0);
};
} // End llvm namespace

4
include/llvm/IntrinsicInst.h
View File

@ -96,8 +96,8 @@ namespace llvm {
return unsigned(cast<ConstantInt>(getOperand(2))->getZExtValue());
}
std::string getFileName() const;
std::string getDirectory() const;
Value* getFileName() const;
Value* getDirectory() const;
// Methods for support type inquiry through isa, cast, and dyn_cast:
static inline bool classof(const DbgStopPointInst *) { return true; }

100
lib/Analysis/ValueTracking.cpp
View File

@ -15,6 +15,7 @@
#include "llvm/Analysis/ValueTracking.h"
#include "llvm/Constants.h"
#include "llvm/Instructions.h"
#include "llvm/GlobalVariable.h"
#include "llvm/IntrinsicInst.h"
#include "llvm/Target/TargetData.h"
#include "llvm/Support/GetElementPtrTypeIterator.h"
@ -930,3 +931,102 @@ Value *llvm::FindInsertedValue(Value *V, const unsigned *idx_begin,
// or load instruction)
return 0;
}
/// GetConstantStringInfo - This function computes the length of a
/// null-terminated C string pointed to by V. If successful, it returns true
/// and returns the string in Str. If unsuccessful, it returns false.
bool llvm::GetConstantStringInfo(Value *V, std::string &Str, uint64_t Offset,
bool StopAtNul) {
// If V is NULL then return false;
if (V == NULL) return false;
// Look through bitcast instructions.
if (BitCastInst *BCI = dyn_cast<BitCastInst>(V))
return GetConstantStringInfo(BCI->getOperand(0), Str, Offset, StopAtNul);
// If the value is not a GEP instruction nor a constant expression with a
// GEP instruction, then return false because ConstantArray can't occur
// any other way
User *GEP = 0;
if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(V)) {
GEP = GEPI;
} else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) {
if (CE->getOpcode() == Instruction::BitCast)
return GetConstantStringInfo(CE->getOperand(0), Str, Offset, StopAtNul);
if (CE->getOpcode() != Instruction::GetElementPtr)
return false;
GEP = CE;
}
if (GEP) {
// Make sure the GEP has exactly three arguments.
if (GEP->getNumOperands() != 3)
return false;
// Make sure the index-ee is a pointer to array of i8.
const PointerType *PT = cast<PointerType>(GEP->getOperand(0)->getType());
const ArrayType *AT = dyn_cast<ArrayType>(PT->getElementType());
if (AT == 0 || AT->getElementType() != Type::Int8Ty)
return false;
// 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.
ConstantInt *FirstIdx = dyn_cast<ConstantInt>(GEP->getOperand(1));
if (FirstIdx == 0 || !FirstIdx->isZero())
return false;
// 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 false;
return GetConstantStringInfo(GEP->getOperand(0), Str, StartIdx+Offset,
StopAtNul);
}
// 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>(V);
if (!GV || !GV->isConstant() || !GV->hasInitializer())
return false;
Constant *GlobalInit = GV->getInitializer();
// Handle the ConstantAggregateZero case
if (isa<ConstantAggregateZero>(GlobalInit)) {
// This is a degenerate case. The initializer is constant zero so the
// length of the string must be zero.
Str.clear();
return true;
}
// Must be a Constant Array
ConstantArray *Array = dyn_cast<ConstantArray>(GlobalInit);
if (Array == 0 || Array->getType()->getElementType() != Type::Int8Ty)
return false;
// Get the number of elements in the array
uint64_t NumElts = Array->getType()->getNumElements();
if (Offset > NumElts)
return false;
// Traverse the constant array from 'Offset' which is the place the GEP refers
// to in the array.
Str.reserve(NumElts-Offset);
for (unsigned i = Offset; 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 false;
if (StopAtNul && CI->isZero())
return true; // we found end of string, success!
Str += (char)CI->getZExtValue();
}
// The array isn't null terminated, but maybe this is a memcpy, not a strcpy.
return true;
}

5
lib/CodeGen/MachineModuleInfo.cpp
View File

@ -10,6 +10,7 @@
#include "llvm/CodeGen/MachineModuleInfo.h"
#include "llvm/Constants.h"
#include "llvm/Analysis/ValueTracking.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineLocation.h"
@ -206,7 +207,9 @@ public:
}
virtual void Apply(std::string &Field) {
Constant *C = CI->getOperand(I++);
Field = C->getStringValue();
// Fills in the string if it succeeds
if (!GetConstantStringInfo(C, Field))
Field.clear();
}
virtual void Apply(DebugInfoDesc *&Field) {
Constant *C = CI->getOperand(I++);

63
lib/CodeGen/SelectionDAG/SelectionDAG.cpp
View File

@ -12,6 +12,7 @@
//===----------------------------------------------------------------------===//
#include "llvm/CodeGen/SelectionDAG.h"
#include "llvm/Constants.h"
#include "llvm/Analysis/ValueTracking.h"
#include "llvm/GlobalAlias.h"
#include "llvm/GlobalVariable.h"
#include "llvm/Intrinsics.h"
@ -747,18 +748,14 @@ SDOperand SelectionDAG::getString(const std::string &Val) {
}
SDOperand SelectionDAG::getConstant(uint64_t Val, MVT VT, bool isT) {
MVT EltVT =
VT.isVector() ? VT.getVectorElementType() : VT;
MVT EltVT = VT.isVector() ? VT.getVectorElementType() : VT;
return getConstant(APInt(EltVT.getSizeInBits(), Val), VT, isT);
}
SDOperand SelectionDAG::getConstant(const APInt &Val, MVT VT, bool isT) {
assert(VT.isInteger() && "Cannot create FP integer constant!");
MVT EltVT =
VT.isVector() ? VT.getVectorElementType() : VT;
MVT EltVT = VT.isVector() ? VT.getVectorElementType() : VT;
assert(Val.getBitWidth() == EltVT.getSizeInBits() &&
"APInt size does not match type size!");
@ -2554,6 +2551,16 @@ static SDOperand getMemsetValue(SDOperand Value, MVT VT, SelectionDAG &DAG) {
static SDOperand getMemsetStringVal(MVT VT, SelectionDAG &DAG,
const TargetLowering &TLI,
std::string &Str, unsigned Offset) {
// Handle vector with all elements zero.
if (Str.empty()) {
if (VT.isInteger())
return DAG.getConstant(0, VT);
unsigned NumElts = VT.getVectorNumElements();
MVT EltVT = (VT.getVectorElementType() == MVT::f32) ? MVT::i32 : MVT::i64;
return DAG.getNode(ISD::BIT_CONVERT, VT,
DAG.getConstant(0, MVT::getVectorVT(EltVT, NumElts)));
}
assert(!VT.isVector() && "Can't handle vector type here!");
unsigned NumBits = VT.getSizeInBits();
unsigned MSB = NumBits / 8;
@ -2577,8 +2584,7 @@ static SDOperand getMemBasePlusOffset(SDOperand Base, unsigned Offset,
/// isMemSrcFromString - Returns true if memcpy source is a string constant.
///
static bool isMemSrcFromString(SDOperand Src, std::string &Str,
uint64_t &SrcOff) {
static bool isMemSrcFromString(SDOperand Src, std::string &Str) {
unsigned SrcDelta = 0;
GlobalAddressSDNode *G = NULL;
if (Src.getOpcode() == ISD::GlobalAddress)
@ -2593,13 +2599,8 @@ static bool isMemSrcFromString(SDOperand Src, std::string &Str,
return false;
GlobalVariable *GV = dyn_cast<GlobalVariable>(G->getGlobal());
if (GV && GV->isConstant()) {
Str = GV->getStringValue(false);
if (!Str.empty()) {
SrcOff += SrcDelta;
return true;
}
}
if (GV && GetConstantStringInfo(GV, Str, SrcDelta, false))
return true;
return false;
}
@ -2611,14 +2612,12 @@ static
bool MeetsMaxMemopRequirement(std::vector<MVT> &MemOps,
SDOperand Dst, SDOperand Src,
unsigned Limit, uint64_t Size, unsigned &Align,
std::string &Str, bool &isSrcStr,
SelectionDAG &DAG,
const TargetLowering &TLI) {
bool AllowUnalign = TLI.allowsUnalignedMemoryAccesses();
std::string Str;
uint64_t SrcOff = 0;
bool isSrcStr = isMemSrcFromString(Src, Str, SrcOff);
isSrcStr = isMemSrcFromString(Src, Str);
bool isSrcConst = isa<ConstantSDNode>(Src);
bool AllowUnalign = TLI.allowsUnalignedMemoryAccesses();
MVT VT= TLI.getOptimalMemOpType(Size, Align, isSrcConst, isSrcStr);
if (VT != MVT::iAny) {
unsigned NewAlign = (unsigned)
@ -2707,26 +2706,28 @@ static SDOperand getMemcpyLoadsAndStores(SelectionDAG &DAG,
if (!AlwaysInline)
Limit = TLI.getMaxStoresPerMemcpy();
unsigned DstAlign = Align; // Destination alignment can change.
std::string Str;
bool CopyFromStr;
if (!MeetsMaxMemopRequirement(MemOps, Dst, Src, Limit, Size, DstAlign,
DAG, TLI))
Str, CopyFromStr, DAG, TLI))
return SDOperand();
std::string Str;
uint64_t SrcOff = 0, DstOff = 0;
bool CopyFromStr = isMemSrcFromString(Src, Str, SrcOff);
bool isZeroStr = CopyFromStr && Str.empty();
SmallVector<SDOperand, 8> OutChains;
unsigned NumMemOps = MemOps.size();
uint64_t SrcOff = 0, DstOff = 0;
for (unsigned i = 0; i < NumMemOps; i++) {
MVT VT = MemOps[i];
unsigned VTSize = VT.getSizeInBits() / 8;
SDOperand Value, Store;
if (CopyFromStr && !VT.isVector()) {
if (CopyFromStr && (isZeroStr || !VT.isVector())) {
// It's unlikely a store of a vector immediate can be done in a single
// instruction. It would require a load from a constantpool first.
// FIXME: Handle cases where store of vector immediate is done in a
// single instruction.
// We also handle store a vector with all zero's.
// FIXME: Handle other cases where store of vector immediate is done in
// a single instruction.
Value = getMemsetStringVal(VT, DAG, TLI, Str, SrcOff);
Store = DAG.getStore(Chain, Value,
getMemBasePlusOffset(Dst, DstOff, DAG),
@ -2763,8 +2764,10 @@ static SDOperand getMemmoveLoadsAndStores(SelectionDAG &DAG,
if (!AlwaysInline)
Limit = TLI.getMaxStoresPerMemmove();
unsigned DstAlign = Align; // Destination alignment can change.
std::string Str;
bool CopyFromStr;
if (!MeetsMaxMemopRequirement(MemOps, Dst, Src, Limit, Size, DstAlign,
DAG, TLI))
Str, CopyFromStr, DAG, TLI))
return SDOperand();
uint64_t SrcOff = 0, DstOff = 0;
@ -2814,8 +2817,10 @@ static SDOperand getMemsetStores(SelectionDAG &DAG,
// Expand memset to a series of load/store ops if the size operand
// falls below a certain threshold.
std::vector<MVT> MemOps;
std::string Str;
bool CopyFromStr;
if (!MeetsMaxMemopRequirement(MemOps, Dst, Src, TLI.getMaxStoresPerMemset(),
Size, Align, DAG, TLI))
Size, Align, Str, CopyFromStr, DAG, TLI))
return SDOperand();
SmallVector<SDOperand, 8> OutChains;

10
lib/Debugger/ProgramInfo.cpp
View File

@ -14,6 +14,7 @@
#include "llvm/Debugger/ProgramInfo.h"
#include "llvm/Constants.h"
#include "llvm/Analysis/ValueTracking.h"
#include "llvm/DerivedTypes.h"
#include "llvm/Intrinsics.h"
#include "llvm/IntrinsicInst.h"
@ -115,8 +116,10 @@ SourceFileInfo::SourceFileInfo(const GlobalVariable *Desc,
if (ConstantInt *CUI = dyn_cast<ConstantInt>(CS->getOperand(1)))
Version = CUI->getZExtValue();
BaseName = CS->getOperand(3)->getStringValue();
Directory = CS->getOperand(4)->getStringValue();
if (!GetConstantStringInfo(CS->getOperand(3), BaseName))
BaseName = "";
if (!GetConstantStringInfo(CS->getOperand(4), Directory))
Directory = "";
}
}
@ -156,7 +159,8 @@ SourceFunctionInfo::SourceFunctionInfo(ProgramInfo &PI,
SourceFile = &PI.getSourceFile(GV);
// Entry #2 is the function name.
Name = CS->getOperand(2)->getStringValue();
if (!GetConstantStringInfo(CS->getOperand(2), Name))
Name = "";
}
}

4
lib/Transforms/Scalar/InstructionCombining.cpp
View File

@ -9973,8 +9973,8 @@ static Instruction *InstCombineLoadCast(InstCombiner &IC, LoadInst &LI,
if (ConstantExpr *CE = dyn_cast<ConstantExpr>(CI)) {
// Instead of loading constant c string, use corresponding integer value
// directly if string length is small enough.
const std::string &Str = CE->getOperand(0)->getStringValue();
if (!Str.empty()) {
std::string Str;
if (GetConstantStringInfo(CE->getOperand(0), Str) && !Str.empty()) {
unsigned len = Str.length();
const Type *Ty = cast<PointerType>(CE->getType())->getElementType();
unsigned numBits = Ty->getPrimitiveSizeInBits();

83
lib/Transforms/Scalar/SimplifyLibCalls.cpp
View File

@ -23,6 +23,7 @@
#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"
@ -229,88 +230,6 @@ void LibCallOptimization::EmitFWrite(Value *Ptr, Value *Size, Value *File,
// Helper Functions
//===----------------------------------------------------------------------===//
/// GetConstantStringInfo - This function computes the length of a
/// null-terminated C string pointed to by V. If successful, it returns true
/// and returns the string in Str. If unsuccessful, it returns false.
static bool GetConstantStringInfo(Value *V, std::string &Str) {
// Look bitcast instructions.
if (BitCastInst *BCI = dyn_cast<BitCastInst>(V))
return GetConstantStringInfo(BCI->getOperand(0), Str);
// If the value is not a GEP instruction nor a constant expression with a
// GEP instruction, then return false because ConstantArray can't occur
// any other way
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 false;
GEP = CE;
} else {
return false;
}
// Make sure the GEP has exactly three arguments.
if (GEP->getNumOperands() != 3)
return false;
// 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 false;
} else
return false;
// 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 false;
// 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 false;
Constant *GlobalInit = GV->getInitializer();
// Handle the ConstantAggregateZero case
if (isa<ConstantAggregateZero>(GlobalInit)) {
// This is a degenerate case. The initializer is constant zero so the
// length of the string must be zero.
Str.clear();
return true;
}
// Must be a Constant Array
ConstantArray *Array = dyn_cast<ConstantArray>(GlobalInit);
if (Array == 0 || 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 false;
if (CI->isZero())
return true; // we found end of string, success!
Str += (char)CI->getZExtValue();
}
return false; // The array isn't null terminated.
}
/// 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) {

42
lib/VMCore/Constants.cpp
View File

@ -2658,44 +2658,4 @@ void ConstantExpr::replaceUsesOfWithOnConstant(Value *From, Value *ToV,
// Delete the old constant!
destroyConstant();
}
/// getStringValue - Turn an LLVM constant pointer that eventually points to a
/// global into a string value. Return an empty string if we can't do it.
/// Parameter Chop determines if the result is chopped at the first null
/// terminator.
///
std::string Constant::getStringValue(bool Chop, unsigned Offset) {
if (GlobalVariable *GV = dyn_cast<GlobalVariable>(this)) {
if (GV->hasInitializer() && isa<ConstantArray>(GV->getInitializer())) {
ConstantArray *Init = cast<ConstantArray>(GV->getInitializer());
if (Init->isString()) {
std::string Result = Init->getAsString();
if (Offset < Result.size()) {
// If we are pointing INTO The string, erase the beginning...
Result.erase(Result.begin(), Result.begin()+Offset);
// Take off the null terminator, and any string fragments after it.
if (Chop) {
std::string::size_type NullPos = Result.find_first_of((char)0);
if (NullPos != std::string::npos)
Result.erase(Result.begin()+NullPos, Result.end());
}
return Result;
}
}
}
} else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(this)) {
if (CE->getOpcode() == Instruction::GetElementPtr) {
// Turn a gep into the specified offset.
if (CE->getNumOperands() == 3 &&
cast<Constant>(CE->getOperand(1))->isNullValue() &&
isa<ConstantInt>(CE->getOperand(2))) {
Offset += cast<ConstantInt>(CE->getOperand(2))->getZExtValue();
return CE->getOperand(0)->getStringValue(Chop, Offset);
}
}
}
return "";
}
}

13
lib/VMCore/IntrinsicInst.cpp
View File

@ -28,6 +28,7 @@
#include "llvm/IntrinsicInst.h"
#include "llvm/Constants.h"
#include "llvm/GlobalVariable.h"
#include "llvm/Analysis/ValueTracking.h"
#include "llvm/CodeGen/MachineDebugInfoDesc.h"
#include "llvm/CodeGen/MachineModuleInfo.h"
using namespace llvm;
@ -58,20 +59,20 @@ Value *DbgInfoIntrinsic::StripCast(Value *C) {
/// DbgStopPointInst - This represents the llvm.dbg.stoppoint instruction.
///
std::string DbgStopPointInst::getFileName() const {
Value *DbgStopPointInst::getFileName() const {
// Once the operand indices are verified, update this assert
assert(LLVMDebugVersion == (6 << 16) && "Verify operand indices");
GlobalVariable *GV = cast<GlobalVariable>(getContext());
if (!GV->hasInitializer()) return "";
if (!GV->hasInitializer()) return NULL;
ConstantStruct *CS = cast<ConstantStruct>(GV->getInitializer());
return CS->getOperand(3)->getStringValue();
return CS->getOperand(4);
}
std::string DbgStopPointInst::getDirectory() const {
Value *DbgStopPointInst::getDirectory() const {
// Once the operand indices are verified, update this assert
assert(LLVMDebugVersion == (6 << 16) && "Verify operand indices");
GlobalVariable *GV = cast<GlobalVariable>(getContext());
if (!GV->hasInitializer()) return "";
if (!GV->hasInitializer()) return NULL;
ConstantStruct *CS = cast<ConstantStruct>(GV->getInitializer());
return CS->getOperand(4)->getStringValue();
return CS->getOperand(4);
}