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299 lines
11 KiB
C++
299 lines
11 KiB
C++
//==- llvm/CodeGen/SelectionDAGAddressAnalysis.cpp - DAG Address Analysis --==//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/CodeGen/SelectionDAGAddressAnalysis.h"
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#include "llvm/CodeGen/ISDOpcodes.h"
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#include "llvm/CodeGen/MachineFrameInfo.h"
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#include "llvm/CodeGen/MachineFunction.h"
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#include "llvm/CodeGen/SelectionDAG.h"
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#include "llvm/CodeGen/SelectionDAGNodes.h"
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#include "llvm/CodeGen/TargetLowering.h"
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#include "llvm/Support/Casting.h"
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#include "llvm/Support/Debug.h"
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#include <cstdint>
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using namespace llvm;
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bool BaseIndexOffset::equalBaseIndex(const BaseIndexOffset &Other,
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const SelectionDAG &DAG,
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int64_t &Off) const {
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// Conservatively fail if we a match failed..
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if (!Base.getNode() || !Other.Base.getNode())
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return false;
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if (!hasValidOffset() || !Other.hasValidOffset())
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return false;
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// Initial Offset difference.
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Off = *Other.Offset - *Offset;
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if ((Other.Index == Index) && (Other.IsIndexSignExt == IsIndexSignExt)) {
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// Trivial match.
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if (Other.Base == Base)
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return true;
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// Match GlobalAddresses
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if (auto *A = dyn_cast<GlobalAddressSDNode>(Base))
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if (auto *B = dyn_cast<GlobalAddressSDNode>(Other.Base))
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if (A->getGlobal() == B->getGlobal()) {
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Off += B->getOffset() - A->getOffset();
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return true;
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}
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// Match Constants
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if (auto *A = dyn_cast<ConstantPoolSDNode>(Base))
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if (auto *B = dyn_cast<ConstantPoolSDNode>(Other.Base)) {
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bool IsMatch =
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A->isMachineConstantPoolEntry() == B->isMachineConstantPoolEntry();
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if (IsMatch) {
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if (A->isMachineConstantPoolEntry())
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IsMatch = A->getMachineCPVal() == B->getMachineCPVal();
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else
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IsMatch = A->getConstVal() == B->getConstVal();
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}
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if (IsMatch) {
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Off += B->getOffset() - A->getOffset();
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return true;
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}
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}
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const MachineFrameInfo &MFI = DAG.getMachineFunction().getFrameInfo();
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// Match FrameIndexes.
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if (auto *A = dyn_cast<FrameIndexSDNode>(Base))
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if (auto *B = dyn_cast<FrameIndexSDNode>(Other.Base)) {
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// Equal FrameIndexes - offsets are directly comparable.
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if (A->getIndex() == B->getIndex())
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return true;
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// Non-equal FrameIndexes - If both frame indices are fixed
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// we know their relative offsets and can compare them. Otherwise
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// we must be conservative.
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if (MFI.isFixedObjectIndex(A->getIndex()) &&
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MFI.isFixedObjectIndex(B->getIndex())) {
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Off += MFI.getObjectOffset(B->getIndex()) -
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MFI.getObjectOffset(A->getIndex());
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return true;
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}
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}
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}
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return false;
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}
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bool BaseIndexOffset::computeAliasing(const SDNode *Op0,
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const Optional<int64_t> NumBytes0,
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const SDNode *Op1,
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const Optional<int64_t> NumBytes1,
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const SelectionDAG &DAG, bool &IsAlias) {
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BaseIndexOffset BasePtr0 = match(Op0, DAG);
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BaseIndexOffset BasePtr1 = match(Op1, DAG);
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if (!(BasePtr0.getBase().getNode() && BasePtr1.getBase().getNode()))
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return false;
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int64_t PtrDiff;
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if (NumBytes0.hasValue() && NumBytes1.hasValue() &&
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BasePtr0.equalBaseIndex(BasePtr1, DAG, PtrDiff)) {
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// BasePtr1 is PtrDiff away from BasePtr0. They alias if none of the
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// following situations arise:
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IsAlias = !(
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// [----BasePtr0----]
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// [---BasePtr1--]
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// ========PtrDiff========>
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(*NumBytes0 <= PtrDiff) ||
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// [----BasePtr0----]
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// [---BasePtr1--]
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// =====(-PtrDiff)====>
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(PtrDiff + *NumBytes1 <= 0)); // i.e. *NumBytes1 < -PtrDiff.
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return true;
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}
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// If both BasePtr0 and BasePtr1 are FrameIndexes, we will not be
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// able to calculate their relative offset if at least one arises
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// from an alloca. However, these allocas cannot overlap and we
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// can infer there is no alias.
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if (auto *A = dyn_cast<FrameIndexSDNode>(BasePtr0.getBase()))
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if (auto *B = dyn_cast<FrameIndexSDNode>(BasePtr1.getBase())) {
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MachineFrameInfo &MFI = DAG.getMachineFunction().getFrameInfo();
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// If the base are the same frame index but the we couldn't find a
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// constant offset, (indices are different) be conservative.
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if (A != B && (!MFI.isFixedObjectIndex(A->getIndex()) ||
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!MFI.isFixedObjectIndex(B->getIndex()))) {
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IsAlias = false;
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return true;
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}
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}
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bool IsFI0 = isa<FrameIndexSDNode>(BasePtr0.getBase());
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bool IsFI1 = isa<FrameIndexSDNode>(BasePtr1.getBase());
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bool IsGV0 = isa<GlobalAddressSDNode>(BasePtr0.getBase());
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bool IsGV1 = isa<GlobalAddressSDNode>(BasePtr1.getBase());
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bool IsCV0 = isa<ConstantPoolSDNode>(BasePtr0.getBase());
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bool IsCV1 = isa<ConstantPoolSDNode>(BasePtr1.getBase());
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// If of mismatched base types or checkable indices we can check
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// they do not alias.
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if ((BasePtr0.getIndex() == BasePtr1.getIndex() || (IsFI0 != IsFI1) ||
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(IsGV0 != IsGV1) || (IsCV0 != IsCV1)) &&
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(IsFI0 || IsGV0 || IsCV0) && (IsFI1 || IsGV1 || IsCV1)) {
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IsAlias = false;
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return true;
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}
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return false; // Cannot determine whether the pointers alias.
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}
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bool BaseIndexOffset::contains(const SelectionDAG &DAG, int64_t BitSize,
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const BaseIndexOffset &Other,
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int64_t OtherBitSize, int64_t &BitOffset) const {
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int64_t Offset;
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if (!equalBaseIndex(Other, DAG, Offset))
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return false;
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if (Offset >= 0) {
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// Other is after *this:
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// [-------*this---------]
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// [---Other--]
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// ==Offset==>
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BitOffset = 8 * Offset;
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return BitOffset + OtherBitSize <= BitSize;
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}
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// Other starts strictly before *this, it cannot be fully contained.
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// [-------*this---------]
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// [--Other--]
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return false;
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}
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/// Parses tree in Ptr for base, index, offset addresses.
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static BaseIndexOffset matchLSNode(const LSBaseSDNode *N,
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const SelectionDAG &DAG) {
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SDValue Ptr = N->getBasePtr();
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// (((B + I*M) + c)) + c ...
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SDValue Base = DAG.getTargetLoweringInfo().unwrapAddress(Ptr);
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SDValue Index = SDValue();
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int64_t Offset = 0;
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bool IsIndexSignExt = false;
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// pre-inc/pre-dec ops are components of EA.
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if (N->getAddressingMode() == ISD::PRE_INC) {
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if (auto *C = dyn_cast<ConstantSDNode>(N->getOffset()))
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Offset += C->getSExtValue();
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else // If unknown, give up now.
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return BaseIndexOffset(SDValue(), SDValue(), 0, false);
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} else if (N->getAddressingMode() == ISD::PRE_DEC) {
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if (auto *C = dyn_cast<ConstantSDNode>(N->getOffset()))
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Offset -= C->getSExtValue();
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else // If unknown, give up now.
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return BaseIndexOffset(SDValue(), SDValue(), 0, false);
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}
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// Consume constant adds & ors with appropriate masking.
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while (true) {
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switch (Base->getOpcode()) {
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case ISD::OR:
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// Only consider ORs which act as adds.
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if (auto *C = dyn_cast<ConstantSDNode>(Base->getOperand(1)))
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if (DAG.MaskedValueIsZero(Base->getOperand(0), C->getAPIntValue())) {
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Offset += C->getSExtValue();
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Base = DAG.getTargetLoweringInfo().unwrapAddress(Base->getOperand(0));
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continue;
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}
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break;
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case ISD::ADD:
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if (auto *C = dyn_cast<ConstantSDNode>(Base->getOperand(1))) {
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Offset += C->getSExtValue();
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Base = DAG.getTargetLoweringInfo().unwrapAddress(Base->getOperand(0));
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continue;
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}
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break;
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case ISD::LOAD:
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case ISD::STORE: {
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auto *LSBase = cast<LSBaseSDNode>(Base.getNode());
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unsigned int IndexResNo = (Base->getOpcode() == ISD::LOAD) ? 1 : 0;
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if (LSBase->isIndexed() && Base.getResNo() == IndexResNo)
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if (auto *C = dyn_cast<ConstantSDNode>(LSBase->getOffset())) {
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auto Off = C->getSExtValue();
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if (LSBase->getAddressingMode() == ISD::PRE_DEC ||
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LSBase->getAddressingMode() == ISD::POST_DEC)
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Offset -= Off;
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else
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Offset += Off;
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Base = DAG.getTargetLoweringInfo().unwrapAddress(LSBase->getBasePtr());
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continue;
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}
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break;
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}
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}
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// If we get here break out of the loop.
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break;
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}
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if (Base->getOpcode() == ISD::ADD) {
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// TODO: The following code appears to be needless as it just
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// bails on some Ptrs early, reducing the cases where we
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// find equivalence. We should be able to remove this.
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// Inside a loop the current BASE pointer is calculated using an ADD and a
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// MUL instruction. In this case Base is the actual BASE pointer.
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// (i64 add (i64 %array_ptr)
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// (i64 mul (i64 %induction_var)
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// (i64 %element_size)))
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if (Base->getOperand(1)->getOpcode() == ISD::MUL)
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return BaseIndexOffset(Base, Index, Offset, IsIndexSignExt);
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// Look at Base + Index + Offset cases.
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Index = Base->getOperand(1);
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SDValue PotentialBase = Base->getOperand(0);
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// Skip signextends.
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if (Index->getOpcode() == ISD::SIGN_EXTEND) {
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Index = Index->getOperand(0);
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IsIndexSignExt = true;
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}
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// Check if Index Offset pattern
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if (Index->getOpcode() != ISD::ADD ||
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!isa<ConstantSDNode>(Index->getOperand(1)))
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return BaseIndexOffset(PotentialBase, Index, Offset, IsIndexSignExt);
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Offset += cast<ConstantSDNode>(Index->getOperand(1))->getSExtValue();
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Index = Index->getOperand(0);
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if (Index->getOpcode() == ISD::SIGN_EXTEND) {
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Index = Index->getOperand(0);
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IsIndexSignExt = true;
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} else
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IsIndexSignExt = false;
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Base = PotentialBase;
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}
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return BaseIndexOffset(Base, Index, Offset, IsIndexSignExt);
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}
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BaseIndexOffset BaseIndexOffset::match(const SDNode *N,
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const SelectionDAG &DAG) {
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if (const auto *LS0 = dyn_cast<LSBaseSDNode>(N))
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return matchLSNode(LS0, DAG);
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if (const auto *LN = dyn_cast<LifetimeSDNode>(N)) {
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if (LN->hasOffset())
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return BaseIndexOffset(LN->getOperand(1), SDValue(), LN->getOffset(),
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false);
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return BaseIndexOffset(LN->getOperand(1), SDValue(), false);
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}
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return BaseIndexOffset();
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}
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#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
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LLVM_DUMP_METHOD void BaseIndexOffset::dump() const {
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print(dbgs());
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}
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void BaseIndexOffset::print(raw_ostream& OS) const {
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OS << "BaseIndexOffset base=[";
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Base->print(OS);
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OS << "] index=[";
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if (Index)
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Index->print(OS);
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OS << "] offset=" << Offset;
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}
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#endif
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