llvm-project/llvm/lib/CodeGen/SelectionDAG/SelectionDAGAddressAnalysis...

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//==- llvm/CodeGen/SelectionDAGAddressAnalysis.cpp - DAG Address Analysis --==//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#include "llvm/CodeGen/SelectionDAGAddressAnalysis.h"
#include "llvm/CodeGen/ISDOpcodes.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/SelectionDAG.h"
#include "llvm/CodeGen/SelectionDAGNodes.h"
#include "llvm/CodeGen/TargetLowering.h"
#include "llvm/Support/Casting.h"
#include <cstdint>
using namespace llvm;
bool BaseIndexOffset::equalBaseIndex(const BaseIndexOffset &Other,
const SelectionDAG &DAG,
int64_t &Off) const {
// Conservatively fail if we a match failed..
if (!Base.getNode() || !Other.Base.getNode())
return false;
// Initial Offset difference.
Off = Other.Offset - Offset;
if ((Other.Index == Index) && (Other.IsIndexSignExt == IsIndexSignExt)) {
// Trivial match.
if (Other.Base == Base)
return true;
// Match GlobalAddresses
if (auto *A = dyn_cast<GlobalAddressSDNode>(Base))
if (auto *B = dyn_cast<GlobalAddressSDNode>(Other.Base))
if (A->getGlobal() == B->getGlobal()) {
Off += B->getOffset() - A->getOffset();
return true;
}
// Match Constants
if (auto *A = dyn_cast<ConstantPoolSDNode>(Base))
if (auto *B = dyn_cast<ConstantPoolSDNode>(Other.Base)) {
bool IsMatch =
A->isMachineConstantPoolEntry() == B->isMachineConstantPoolEntry();
if (IsMatch) {
if (A->isMachineConstantPoolEntry())
IsMatch = A->getMachineCPVal() == B->getMachineCPVal();
else
IsMatch = A->getConstVal() == B->getConstVal();
}
if (IsMatch) {
Off += B->getOffset() - A->getOffset();
return true;
}
}
const MachineFrameInfo &MFI = DAG.getMachineFunction().getFrameInfo();
// Match FrameIndexes.
if (auto *A = dyn_cast<FrameIndexSDNode>(Base))
if (auto *B = dyn_cast<FrameIndexSDNode>(Other.Base)) {
// Equal FrameIndexes - offsets are directly comparable.
if (A->getIndex() == B->getIndex())
return true;
// Non-equal FrameIndexes - If both frame indices are fixed
// we know their relative offsets and can compare them. Otherwise
// we must be conservative.
if (MFI.isFixedObjectIndex(A->getIndex()) &&
MFI.isFixedObjectIndex(B->getIndex())) {
Off += MFI.getObjectOffset(B->getIndex()) -
MFI.getObjectOffset(A->getIndex());
return true;
}
}
}
return false;
}
bool BaseIndexOffset::computeAliasing(const BaseIndexOffset &BasePtr0,
const int64_t NumBytes0,
const BaseIndexOffset &BasePtr1,
const int64_t NumBytes1,
const SelectionDAG &DAG, bool &IsAlias) {
if (!(BasePtr0.getBase().getNode() && BasePtr1.getBase().getNode()))
return false;
int64_t PtrDiff;
if (BasePtr0.equalBaseIndex(BasePtr1, DAG, PtrDiff)) {
// BasePtr1 is PtrDiff away from BasePtr0. They alias if none of the
// following situations arise:
IsAlias = !(
// [----BasePtr0----]
// [---BasePtr1--]
// ========PtrDiff========>
(NumBytes0 <= PtrDiff) ||
// [----BasePtr0----]
// [---BasePtr1--]
// =====(-PtrDiff)====>
(PtrDiff + NumBytes1 <= 0)); // i.e. NumBytes1 < -PtrDiff.
return true;
}
// If both BasePtr0 and BasePtr1 are FrameIndexes, we will not be
// able to calculate their relative offset if at least one arises
// from an alloca. However, these allocas cannot overlap and we
// can infer there is no alias.
if (auto *A = dyn_cast<FrameIndexSDNode>(BasePtr0.getBase()))
if (auto *B = dyn_cast<FrameIndexSDNode>(BasePtr1.getBase())) {
MachineFrameInfo &MFI = DAG.getMachineFunction().getFrameInfo();
// If the base are the same frame index but the we couldn't find a
// constant offset, (indices are different) be conservative.
if (A != B && (!MFI.isFixedObjectIndex(A->getIndex()) ||
!MFI.isFixedObjectIndex(B->getIndex()))) {
IsAlias = false;
return true;
}
}
bool IsFI0 = isa<FrameIndexSDNode>(BasePtr0.getBase());
bool IsFI1 = isa<FrameIndexSDNode>(BasePtr1.getBase());
bool IsGV0 = isa<GlobalAddressSDNode>(BasePtr0.getBase());
bool IsGV1 = isa<GlobalAddressSDNode>(BasePtr1.getBase());
bool IsCV0 = isa<ConstantPoolSDNode>(BasePtr0.getBase());
bool IsCV1 = isa<ConstantPoolSDNode>(BasePtr1.getBase());
// If of mismatched base types or checkable indices we can check
// they do not alias.
if ((BasePtr0.getIndex() == BasePtr1.getIndex() || (IsFI0 != IsFI1) ||
(IsGV0 != IsGV1) || (IsCV0 != IsCV1)) &&
(IsFI0 || IsGV0 || IsCV0) && (IsFI1 || IsGV1 || IsCV1)) {
IsAlias = false;
return true;
}
return false; // Cannot determine whether the pointers alias.
}
bool BaseIndexOffset::contains(const SelectionDAG &DAG, int64_t BitSize,
const BaseIndexOffset &Other,
int64_t OtherBitSize, int64_t &BitOffset) const {
int64_t Offset;
if (!equalBaseIndex(Other, DAG, Offset))
return false;
if (Offset >= 0) {
// Other is after *this:
// [-------*this---------]
// [---Other--]
// ==Offset==>
BitOffset = 8 * Offset;
return BitOffset + OtherBitSize <= BitSize;
}
// Other starts strictly before *this, it cannot be fully contained.
// [-------*this---------]
// [--Other--]
return false;
}
/// Parses tree in Ptr for base, index, offset addresses.
BaseIndexOffset BaseIndexOffset::match(const LSBaseSDNode *N,
const SelectionDAG &DAG) {
SDValue Ptr = N->getBasePtr();
// (((B + I*M) + c)) + c ...
SDValue Base = DAG.getTargetLoweringInfo().unwrapAddress(Ptr);
SDValue Index = SDValue();
int64_t Offset = 0;
bool IsIndexSignExt = false;
// pre-inc/pre-dec ops are components of EA.
if (N->getAddressingMode() == ISD::PRE_INC) {
if (auto *C = dyn_cast<ConstantSDNode>(N->getOffset()))
Offset += C->getSExtValue();
else // If unknown, give up now.
return BaseIndexOffset(SDValue(), SDValue(), 0, false);
} else if (N->getAddressingMode() == ISD::PRE_DEC) {
if (auto *C = dyn_cast<ConstantSDNode>(N->getOffset()))
Offset -= C->getSExtValue();
else // If unknown, give up now.
return BaseIndexOffset(SDValue(), SDValue(), 0, false);
}
// Consume constant adds & ors with appropriate masking.
while (true) {
switch (Base->getOpcode()) {
case ISD::OR:
// Only consider ORs which act as adds.
if (auto *C = dyn_cast<ConstantSDNode>(Base->getOperand(1)))
if (DAG.MaskedValueIsZero(Base->getOperand(0), C->getAPIntValue())) {
Offset += C->getSExtValue();
Base = DAG.getTargetLoweringInfo().unwrapAddress(Base->getOperand(0));
continue;
}
break;
case ISD::ADD:
if (auto *C = dyn_cast<ConstantSDNode>(Base->getOperand(1))) {
Offset += C->getSExtValue();
Base = DAG.getTargetLoweringInfo().unwrapAddress(Base->getOperand(0));
continue;
}
break;
case ISD::LOAD:
case ISD::STORE: {
auto *LSBase = cast<LSBaseSDNode>(Base.getNode());
unsigned int IndexResNo = (Base->getOpcode() == ISD::LOAD) ? 1 : 0;
if (LSBase->isIndexed() && Base.getResNo() == IndexResNo)
if (auto *C = dyn_cast<ConstantSDNode>(LSBase->getOffset())) {
auto Off = C->getSExtValue();
if (LSBase->getAddressingMode() == ISD::PRE_DEC ||
LSBase->getAddressingMode() == ISD::POST_DEC)
Offset -= Off;
else
Offset += Off;
Base = DAG.getTargetLoweringInfo().unwrapAddress(LSBase->getBasePtr());
continue;
}
break;
}
}
// If we get here break out of the loop.
break;
}
if (Base->getOpcode() == ISD::ADD) {
// TODO: The following code appears to be needless as it just
// bails on some Ptrs early, reducing the cases where we
// find equivalence. We should be able to remove this.
// Inside a loop the current BASE pointer is calculated using an ADD and a
// MUL instruction. In this case Base is the actual BASE pointer.
// (i64 add (i64 %array_ptr)
// (i64 mul (i64 %induction_var)
// (i64 %element_size)))
if (Base->getOperand(1)->getOpcode() == ISD::MUL)
return BaseIndexOffset(Base, Index, Offset, IsIndexSignExt);
// Look at Base + Index + Offset cases.
Index = Base->getOperand(1);
SDValue PotentialBase = Base->getOperand(0);
// Skip signextends.
if (Index->getOpcode() == ISD::SIGN_EXTEND) {
Index = Index->getOperand(0);
IsIndexSignExt = true;
}
// Check if Index Offset pattern
if (Index->getOpcode() != ISD::ADD ||
!isa<ConstantSDNode>(Index->getOperand(1)))
return BaseIndexOffset(PotentialBase, Index, Offset, IsIndexSignExt);
Offset += cast<ConstantSDNode>(Index->getOperand(1))->getSExtValue();
Index = Index->getOperand(0);
if (Index->getOpcode() == ISD::SIGN_EXTEND) {
Index = Index->getOperand(0);
IsIndexSignExt = true;
} else
IsIndexSignExt = false;
Base = PotentialBase;
}
return BaseIndexOffset(Base, Index, Offset, IsIndexSignExt);
}
#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
LLVM_DUMP_METHOD void BaseIndexOffset::dump() const {
print(dbgs());
}
void BaseIndexOffset::print(raw_ostream& OS) const {
OS << "BaseIndexOffset base=[";
Base->print(OS);
OS << "] index=[";
if (Index)
Index->print(OS);
OS << "] offset=" << Offset;
}
#endif