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move DecomposeGEPExpression out into ValueTracking.cpp

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@89956 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2009-11-26 17:12:50 +00:00
parent fa3966881f
commit e405c64f6b
3 changed files with 170 additions and 158 deletions
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15
include/llvm/Analysis/ValueTracking.h
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@ -19,6 +19,7 @@
#include <string> #include <string>
namespace llvm { namespace llvm {
template <typename T> class SmallVectorImpl;
class Value; class Value;
class Instruction; class Instruction;
class APInt; class APInt;
@ -77,6 +78,20 @@ namespace llvm {
/// ///
bool CannotBeNegativeZero(const Value *V, unsigned Depth = 0); bool CannotBeNegativeZero(const Value *V, unsigned Depth = 0);
/// DecomposeGEPExpression - If V is a symbolic pointer expression, decompose
/// it into a base pointer with a constant offset and a number of scaled
/// symbolic offsets.
///
/// When TargetData is around, this function is capable of analyzing
/// everything that Value::getUnderlyingObject() can look through. When not,
/// it just looks through pointer casts.
///
const Value *DecomposeGEPExpression(const Value *V, int64_t &BaseOffs,
SmallVectorImpl<std::pair<const Value*, int64_t> > &VarIndices,
const TargetData *TD);
/// FindScalarValue - Given an aggregrate and an sequence of indices, see if /// FindScalarValue - Given an aggregrate and an sequence of indices, see if
/// the scalar value indexed is already around as a register, for example if /// the scalar value indexed is already around as a register, for example if
/// it were inserted directly into the aggregrate. /// it were inserted directly into the aggregrate.

159
lib/Analysis/BasicAliasAnalysis.cpp
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@ -18,7 +18,6 @@
#include "llvm/Constants.h" #include "llvm/Constants.h"
#include "llvm/DerivedTypes.h" #include "llvm/DerivedTypes.h"
#include "llvm/Function.h" #include "llvm/Function.h"
#include "llvm/GlobalAlias.h"
#include "llvm/GlobalVariable.h" #include "llvm/GlobalVariable.h"
#include "llvm/Instructions.h" #include "llvm/Instructions.h"
#include "llvm/IntrinsicInst.h" #include "llvm/IntrinsicInst.h"
@ -28,11 +27,9 @@
#include "llvm/Analysis/MemoryBuiltins.h" #include "llvm/Analysis/MemoryBuiltins.h"
#include "llvm/Analysis/ValueTracking.h" #include "llvm/Analysis/ValueTracking.h"
#include "llvm/Target/TargetData.h" #include "llvm/Target/TargetData.h"
#include "llvm/ADT/SmallSet.h" #include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/SmallVector.h" #include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/Support/ErrorHandling.h" #include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/GetElementPtrTypeIterator.h"
#include <algorithm> #include <algorithm>
using namespace llvm; using namespace llvm;
@ -379,160 +376,6 @@ BasicAliasAnalysis::getModRefInfo(CallSite CS1, CallSite CS2) {
return NoAA::getModRefInfo(CS1, CS2); return NoAA::getModRefInfo(CS1, CS2);
} }
/// GetLinearExpression - Analyze the specified value as a linear expression:
/// "A*V + B". Return the scale and offset values as APInts and return V as a
/// Value*. The incoming Value is known to be a scalar integer.
static Value *GetLinearExpression(Value *V, APInt &Scale, APInt &Offset,
const TargetData *TD) {
assert(isa<IntegerType>(V->getType()) && "Not an integer value");
if (BinaryOperator *BOp = dyn_cast<BinaryOperator>(V)) {
if (ConstantInt *RHSC = dyn_cast<ConstantInt>(BOp->getOperand(1))) {
switch (BOp->getOpcode()) {
default: break;
case Instruction::Or:
// X|C == X+C if all the bits in C are unset in X. Otherwise we can't
// analyze it.
if (!MaskedValueIsZero(BOp->getOperand(0), RHSC->getValue(), TD))
break;
// FALL THROUGH.
case Instruction::Add:
V = GetLinearExpression(BOp->getOperand(0), Scale, Offset, TD);
Offset += RHSC->getValue();
return V;
case Instruction::Mul:
V = GetLinearExpression(BOp->getOperand(0), Scale, Offset, TD);
Offset *= RHSC->getValue();
Scale *= RHSC->getValue();
return V;
case Instruction::Shl:
V = GetLinearExpression(BOp->getOperand(0), Scale, Offset, TD);
Offset <<= RHSC->getValue().getLimitedValue();
Scale <<= RHSC->getValue().getLimitedValue();
return V;
}
}
}
Scale = 1;
Offset = 0;
return V;
}
/// DecomposeGEPExpression - If V is a symbolic pointer expression, decompose it
/// into a base pointer with a constant offset and a number of scaled symbolic
/// offsets.
///
/// When TargetData is around, this function is capable of analyzing everything
/// that Value::getUnderlyingObject() can look through. When not, it just looks
/// through pointer casts.
///
/// FIXME: Move this out to ValueTracking.cpp
///
static const Value *DecomposeGEPExpression(const Value *V, int64_t &BaseOffs,
SmallVectorImpl<std::pair<const Value*, int64_t> > &VarIndices,
const TargetData *TD) {
// FIXME: Should limit depth like getUnderlyingObject?
BaseOffs = 0;
while (1) {
// See if this is a bitcast or GEP.
const Operator *Op = dyn_cast<Operator>(V);
if (Op == 0) {
// The only non-operator case we can handle are GlobalAliases.
if (const GlobalAlias *GA = dyn_cast<GlobalAlias>(V)) {
if (!GA->mayBeOverridden()) {
V = GA->getAliasee();
continue;
}
}
return V;
}
if (Op->getOpcode() == Instruction::BitCast) {
V = Op->getOperand(0);
continue;
}
const GEPOperator *GEPOp = dyn_cast<GEPOperator>(Op);
if (GEPOp == 0)
return V;
// Don't attempt to analyze GEPs over unsized objects.
if (!cast<PointerType>(GEPOp->getOperand(0)->getType())
->getElementType()->isSized())
return V;
// If we are lacking TargetData information, we can't compute the offets of
// elements computed by GEPs. However, we can handle bitcast equivalent
// GEPs.
if (!TD) {
if (!GEPOp->hasAllZeroIndices())
return V;
V = GEPOp->getOperand(0);
continue;
}
// Walk the indices of the GEP, accumulating them into BaseOff/VarIndices.
gep_type_iterator GTI = gep_type_begin(GEPOp);
for (User::const_op_iterator I = next(GEPOp->op_begin()),
E = GEPOp->op_end(); I != E; ++I) {
Value *Index = *I;
// Compute the (potentially symbolic) offset in bytes for this index.
if (const StructType *STy = dyn_cast<StructType>(*GTI++)) {
// For a struct, add the member offset.
unsigned FieldNo = cast<ConstantInt>(Index)->getZExtValue();
if (FieldNo == 0) continue;
BaseOffs += TD->getStructLayout(STy)->getElementOffset(FieldNo);
continue;
}
// For an array/pointer, add the element offset, explicitly scaled.
if (ConstantInt *CIdx = dyn_cast<ConstantInt>(Index)) {
if (CIdx->isZero()) continue;
BaseOffs += TD->getTypeAllocSize(*GTI)*CIdx->getSExtValue();
continue;
}
// TODO: Could handle linear expressions here like A[X+1], also A[X*4|1].
uint64_t Scale = TD->getTypeAllocSize(*GTI);
unsigned Width = cast<IntegerType>(Index->getType())->getBitWidth();
APInt IndexScale(Width, 0), IndexOffset(Width, 0);
Index = GetLinearExpression(Index, IndexScale, IndexOffset, TD);
Scale *= IndexScale.getZExtValue();
BaseOffs += IndexOffset.getZExtValue()*Scale;
// If we already had an occurrance of this index variable, merge this
// scale into it. For example, we want to handle:
// A[x][x] -> x*16 + x*4 -> x*20
// This also ensures that 'x' only appears in the index list once.
for (unsigned i = 0, e = VarIndices.size(); i != e; ++i) {
if (VarIndices[i].first == Index) {
Scale += VarIndices[i].second;
VarIndices.erase(VarIndices.begin()+i);
break;
}
}
// Make sure that we have a scale that makes sense for this target's
// pointer size.
if (unsigned ShiftBits = 64-TD->getPointerSizeInBits()) {
Scale <<= ShiftBits;
Scale >>= ShiftBits;
}
if (Scale)
VarIndices.push_back(std::make_pair(Index, Scale));
}
// Analyze the base pointer next.
V = GEPOp->getOperand(0);
}
}
/// GetIndiceDifference - Dest and Src are the variable indices from two /// GetIndiceDifference - Dest and Src are the variable indices from two
/// decomposed GetElementPtr instructions GEP1 and GEP2 which have common base /// decomposed GetElementPtr instructions GEP1 and GEP2 which have common base
/// pointers. Subtract the GEP2 indices from GEP1 to find the symbolic /// pointers. Subtract the GEP2 indices from GEP1 to find the symbolic

154
lib/Analysis/ValueTracking.cpp
View File

@ -948,6 +948,160 @@ bool llvm::CannotBeNegativeZero(const Value *V, unsigned Depth) {
return false; return false;
} }
/// GetLinearExpression - Analyze the specified value as a linear expression:
/// "A*V + B". Return the scale and offset values as APInts and return V as a
/// Value*. The incoming Value is known to be a scalar integer.
static Value *GetLinearExpression(Value *V, APInt &Scale, APInt &Offset,
const TargetData *TD) {
assert(isa<IntegerType>(V->getType()) && "Not an integer value");
if (BinaryOperator *BOp = dyn_cast<BinaryOperator>(V)) {
if (ConstantInt *RHSC = dyn_cast<ConstantInt>(BOp->getOperand(1))) {
switch (BOp->getOpcode()) {
default: break;
case Instruction::Or:
// X|C == X+C if all the bits in C are unset in X. Otherwise we can't
// analyze it.
if (!MaskedValueIsZero(BOp->getOperand(0), RHSC->getValue(), TD))
break;
// FALL THROUGH.
case Instruction::Add:
V = GetLinearExpression(BOp->getOperand(0), Scale, Offset, TD);
Offset += RHSC->getValue();
return V;
case Instruction::Mul:
V = GetLinearExpression(BOp->getOperand(0), Scale, Offset, TD);
Offset *= RHSC->getValue();
Scale *= RHSC->getValue();
return V;
case Instruction::Shl:
V = GetLinearExpression(BOp->getOperand(0), Scale, Offset, TD);
Offset <<= RHSC->getValue().getLimitedValue();
Scale <<= RHSC->getValue().getLimitedValue();
return V;
}
}
}
Scale = 1;
Offset = 0;
return V;
}
/// DecomposeGEPExpression - If V is a symbolic pointer expression, decompose it
/// into a base pointer with a constant offset and a number of scaled symbolic
/// offsets.
///
/// When TargetData is around, this function is capable of analyzing everything
/// that Value::getUnderlyingObject() can look through. When not, it just looks
/// through pointer casts.
///
const Value *llvm::DecomposeGEPExpression(const Value *V, int64_t &BaseOffs,
SmallVectorImpl<std::pair<const Value*, int64_t> > &VarIndices,
const TargetData *TD) {
// FIXME: Should limit depth like getUnderlyingObject?
BaseOffs = 0;
while (1) {
// See if this is a bitcast or GEP.
const Operator *Op = dyn_cast<Operator>(V);
if (Op == 0) {
// The only non-operator case we can handle are GlobalAliases.
if (const GlobalAlias *GA = dyn_cast<GlobalAlias>(V)) {
if (!GA->mayBeOverridden()) {
V = GA->getAliasee();
continue;
}
}
return V;
}
if (Op->getOpcode() == Instruction::BitCast) {
V = Op->getOperand(0);
continue;
}
const GEPOperator *GEPOp = dyn_cast<GEPOperator>(Op);
if (GEPOp == 0)
return V;
// Don't attempt to analyze GEPs over unsized objects.
if (!cast<PointerType>(GEPOp->getOperand(0)->getType())
->getElementType()->isSized())
return V;
// If we are lacking TargetData information, we can't compute the offets of
// elements computed by GEPs. However, we can handle bitcast equivalent
// GEPs.
if (!TD) {
if (!GEPOp->hasAllZeroIndices())
return V;
V = GEPOp->getOperand(0);
continue;
}
// Walk the indices of the GEP, accumulating them into BaseOff/VarIndices.
gep_type_iterator GTI = gep_type_begin(GEPOp);
for (User::const_op_iterator I = GEPOp->op_begin()+1,
E = GEPOp->op_end(); I != E; ++I) {
Value *Index = *I;
// Compute the (potentially symbolic) offset in bytes for this index.
if (const StructType *STy = dyn_cast<StructType>(*GTI++)) {
// For a struct, add the member offset.
unsigned FieldNo = cast<ConstantInt>(Index)->getZExtValue();
if (FieldNo == 0) continue;
BaseOffs += TD->getStructLayout(STy)->getElementOffset(FieldNo);
continue;
}
// For an array/pointer, add the element offset, explicitly scaled.
if (ConstantInt *CIdx = dyn_cast<ConstantInt>(Index)) {
if (CIdx->isZero()) continue;
BaseOffs += TD->getTypeAllocSize(*GTI)*CIdx->getSExtValue();
continue;
}
// TODO: Could handle linear expressions here like A[X+1], also A[X*4|1].
uint64_t Scale = TD->getTypeAllocSize(*GTI);
unsigned Width = cast<IntegerType>(Index->getType())->getBitWidth();
APInt IndexScale(Width, 0), IndexOffset(Width, 0);
Index = GetLinearExpression(Index, IndexScale, IndexOffset, TD);
Scale *= IndexScale.getZExtValue();
BaseOffs += IndexOffset.getZExtValue()*Scale;
// If we already had an occurrance of this index variable, merge this
// scale into it. For example, we want to handle:
// A[x][x] -> x*16 + x*4 -> x*20
// This also ensures that 'x' only appears in the index list once.
for (unsigned i = 0, e = VarIndices.size(); i != e; ++i) {
if (VarIndices[i].first == Index) {
Scale += VarIndices[i].second;
VarIndices.erase(VarIndices.begin()+i);
break;
}
}
// Make sure that we have a scale that makes sense for this target's
// pointer size.
if (unsigned ShiftBits = 64-TD->getPointerSizeInBits()) {
Scale <<= ShiftBits;
Scale >>= ShiftBits;
}
if (Scale)
VarIndices.push_back(std::make_pair(Index, Scale));
}
// Analyze the base pointer next.
V = GEPOp->getOperand(0);
}
}
// This is the recursive version of BuildSubAggregate. It takes a few different // This is the recursive version of BuildSubAggregate. It takes a few different
// arguments. Idxs is the index within the nested struct From that we are // arguments. Idxs is the index within the nested struct From that we are
// looking at now (which is of type IndexedType). IdxSkip is the number of // looking at now (which is of type IndexedType). IdxSkip is the number of