| //==- 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 "llvm/Support/Debug.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; |
| if (!hasValidOffset() || !Other.hasValidOffset()) |
| 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 SDNode *Op0, |
| const Optional<int64_t> NumBytes0, |
| const SDNode *Op1, |
| const Optional<int64_t> NumBytes1, |
| const SelectionDAG &DAG, bool &IsAlias) { |
| |
| BaseIndexOffset BasePtr0 = match(Op0, DAG); |
| BaseIndexOffset BasePtr1 = match(Op1, DAG); |
| |
| if (!(BasePtr0.getBase().getNode() && BasePtr1.getBase().getNode())) |
| return false; |
| int64_t PtrDiff; |
| if (NumBytes0.hasValue() && NumBytes1.hasValue() && |
| 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. |
| static BaseIndexOffset matchLSNode(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); |
| } |
| |
| BaseIndexOffset BaseIndexOffset::match(const SDNode *N, |
| const SelectionDAG &DAG) { |
| if (const auto *LS0 = dyn_cast<LSBaseSDNode>(N)) |
| return matchLSNode(LS0, DAG); |
| if (const auto *LN = dyn_cast<LifetimeSDNode>(N)) { |
| if (LN->hasOffset()) |
| return BaseIndexOffset(LN->getOperand(1), SDValue(), LN->getOffset(), |
| false); |
| return BaseIndexOffset(LN->getOperand(1), SDValue(), false); |
| } |
| return BaseIndexOffset(); |
| } |
| |
| #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 |
