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//===- ValueBoundsOpInterface.cpp - Value Bounds -------------------------===//
//
// 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 "mlir/Interfaces/ValueBoundsOpInterface.h"
#include "mlir/IR/BuiltinTypes.h"
#include "mlir/IR/Matchers.h"
#include "mlir/Interfaces/DestinationStyleOpInterface.h"
#include "mlir/Interfaces/ViewLikeInterface.h"
#include "llvm/ADT/APSInt.h"
#include "llvm/Support/Debug.h"
#define DEBUG_TYPE "value-bounds-op-interface"
using namespace mlir;
using presburger::BoundType;
using presburger::VarKind;
namespace mlir {
#include "mlir/Interfaces/ValueBoundsOpInterface.cpp.inc"
} // namespace mlir
static Operation *getOwnerOfValue(Value value) {
if (auto bbArg = dyn_cast<BlockArgument>(value))
return bbArg.getOwner()->getParentOp();
return value.getDefiningOp();
}
HyperrectangularSlice::HyperrectangularSlice(ArrayRef<OpFoldResult> offsets,
ArrayRef<OpFoldResult> sizes,
ArrayRef<OpFoldResult> strides)
: mixedOffsets(offsets), mixedSizes(sizes), mixedStrides(strides) {
assert(offsets.size() == sizes.size() &&
"expected same number of offsets, sizes, strides");
assert(offsets.size() == strides.size() &&
"expected same number of offsets, sizes, strides");
}
HyperrectangularSlice::HyperrectangularSlice(ArrayRef<OpFoldResult> offsets,
ArrayRef<OpFoldResult> sizes)
: mixedOffsets(offsets), mixedSizes(sizes) {
assert(offsets.size() == sizes.size() &&
"expected same number of offsets and sizes");
// Assume that all strides are 1.
if (offsets.empty())
return;
MLIRContext *ctx = offsets.front().getContext();
mixedStrides.append(offsets.size(), Builder(ctx).getIndexAttr(1));
}
HyperrectangularSlice::HyperrectangularSlice(OffsetSizeAndStrideOpInterface op)
: HyperrectangularSlice(op.getMixedOffsets(), op.getMixedSizes(),
op.getMixedStrides()) {}
/// If ofr is a constant integer or an IntegerAttr, return the integer.
static std::optional<int64_t> getConstantIntValue(OpFoldResult ofr) {
// Case 1: Check for Constant integer.
if (auto val = llvm::dyn_cast_if_present<Value>(ofr)) {
APSInt intVal;
if (matchPattern(val, m_ConstantInt(&intVal)))
return intVal.getSExtValue();
return std::nullopt;
}
// Case 2: Check for IntegerAttr.
Attribute attr = llvm::dyn_cast_if_present<Attribute>(ofr);
if (auto intAttr = dyn_cast_or_null<IntegerAttr>(attr))
return intAttr.getValue().getSExtValue();
return std::nullopt;
}
ValueBoundsConstraintSet::Variable::Variable(OpFoldResult ofr)
: Variable(ofr, std::nullopt) {}
ValueBoundsConstraintSet::Variable::Variable(Value indexValue)
: Variable(static_cast<OpFoldResult>(indexValue)) {}
ValueBoundsConstraintSet::Variable::Variable(Value shapedValue, int64_t dim)
: Variable(static_cast<OpFoldResult>(shapedValue), std::optional(dim)) {}
ValueBoundsConstraintSet::Variable::Variable(OpFoldResult ofr,
std::optional<int64_t> dim) {
Builder b(ofr.getContext());
if (auto constInt = ::getConstantIntValue(ofr)) {
assert(!dim && "expected no dim for index-typed values");
map = AffineMap::get(/*dimCount=*/0, /*symbolCount=*/0,
b.getAffineConstantExpr(*constInt));
return;
}
Value value = cast<Value>(ofr);
#ifndef NDEBUG
if (dim) {
assert(isa<ShapedType>(value.getType()) && "expected shaped type");
} else {
assert(value.getType().isIndex() && "expected index type");
}
#endif // NDEBUG
map = AffineMap::get(/*dimCount=*/0, /*symbolCount=*/1,
b.getAffineSymbolExpr(0));
mapOperands.emplace_back(value, dim);
}
ValueBoundsConstraintSet::Variable::Variable(AffineMap map,
ArrayRef<Variable> mapOperands) {
assert(map.getNumResults() == 1 && "expected single result");
// Turn all dims into symbols.
Builder b(map.getContext());
SmallVector<AffineExpr> dimReplacements, symReplacements;
for (int64_t i = 0, e = map.getNumDims(); i < e; ++i)
dimReplacements.push_back(b.getAffineSymbolExpr(i));
for (int64_t i = 0, e = map.getNumSymbols(); i < e; ++i)
symReplacements.push_back(b.getAffineSymbolExpr(i + map.getNumDims()));
AffineMap tmpMap = map.replaceDimsAndSymbols(
dimReplacements, symReplacements, /*numResultDims=*/0,
/*numResultSyms=*/map.getNumSymbols() + map.getNumDims());
// Inline operands.
DenseMap<AffineExpr, AffineExpr> replacements;
for (auto [index, var] : llvm::enumerate(mapOperands)) {
assert(var.map.getNumResults() == 1 && "expected single result");
assert(var.map.getNumDims() == 0 && "expected only symbols");
SmallVector<AffineExpr> symReplacements;
for (auto valueDim : var.mapOperands) {
auto it = llvm::find(this->mapOperands, valueDim);
if (it != this->mapOperands.end()) {
// There is already a symbol for this operand.
symReplacements.push_back(b.getAffineSymbolExpr(
std::distance(this->mapOperands.begin(), it)));
} else {
// This is a new operand: add a new symbol.
symReplacements.push_back(
b.getAffineSymbolExpr(this->mapOperands.size()));
this->mapOperands.push_back(valueDim);
}
}
replacements[b.getAffineSymbolExpr(index)] =
var.map.getResult(0).replaceSymbols(symReplacements);
}
this->map = tmpMap.replace(replacements, /*numResultDims=*/0,
/*numResultSyms=*/this->mapOperands.size());
}
ValueBoundsConstraintSet::Variable::Variable(AffineMap map,
ArrayRef<Value> mapOperands)
: Variable(map, llvm::map_to_vector(mapOperands,
[](Value v) { return Variable(v); })) {}
ValueBoundsConstraintSet::ValueBoundsConstraintSet(
MLIRContext *ctx, StopConditionFn stopCondition)
: builder(ctx), stopCondition(stopCondition) {
assert(stopCondition && "expected non-null stop condition");
}
char ValueBoundsConstraintSet::ID = 0;
#ifndef NDEBUG
static void assertValidValueDim(Value value, std::optional<int64_t> dim) {
if (value.getType().isIndex()) {
assert(!dim.has_value() && "invalid dim value");
} else if (auto shapedType = dyn_cast<ShapedType>(value.getType())) {
assert(*dim >= 0 && "invalid dim value");
if (shapedType.hasRank())
assert(*dim < shapedType.getRank() && "invalid dim value");
} else {
llvm_unreachable("unsupported type");
}
}
#endif // NDEBUG
void ValueBoundsConstraintSet::addBound(BoundType type, int64_t pos,
AffineExpr expr) {
LogicalResult status = cstr.addBound(
type, pos,
AffineMap::get(cstr.getNumDimVars(), cstr.getNumSymbolVars(), expr));
if (failed(status)) {
// Non-pure (e.g., semi-affine) expressions are not yet supported by
// FlatLinearConstraints. However, we can just ignore such failures here.
// Even without this bound, there may be enough information in the
// constraint system to compute the requested bound. In case this bound is
// actually needed, `computeBound` will return `failure`.
LLVM_DEBUG(llvm::dbgs() << "Failed to add bound: " << expr << "\n");
}
}
AffineExpr ValueBoundsConstraintSet::getExpr(Value value,
std::optional<int64_t> dim) {
#ifndef NDEBUG
assertValidValueDim(value, dim);
#endif // NDEBUG
// Check if the value/dim is statically known. In that case, an affine
// constant expression should be returned. This allows us to support
// multiplications with constants. (Multiplications of two columns in the
// constraint set is not supported.)
std::optional<int64_t> constSize = std::nullopt;
auto shapedType = dyn_cast<ShapedType>(value.getType());
if (shapedType) {
if (shapedType.hasRank() && !shapedType.isDynamicDim(*dim))
constSize = shapedType.getDimSize(*dim);
} else if (auto constInt = ::getConstantIntValue(value)) {
constSize = *constInt;
}
// If the value/dim is already mapped, return the corresponding expression
// directly.
ValueDim valueDim = std::make_pair(value, dim.value_or(kIndexValue));
if (valueDimToPosition.contains(valueDim)) {
// If it is a constant, return an affine constant expression. Otherwise,
// return an affine expression that represents the respective column in the
// constraint set.
if (constSize)
return builder.getAffineConstantExpr(*constSize);
return getPosExpr(getPos(value, dim));
}
if (constSize) {
// Constant index value/dim: add column to the constraint set, add EQ bound
// and return an affine constant expression without pushing the newly added
// column to the worklist.
(void)insert(value, dim, /*isSymbol=*/true, /*addToWorklist=*/false);
if (shapedType)
bound(value)[*dim] == *constSize;
else
bound(value) == *constSize;
return builder.getAffineConstantExpr(*constSize);
}
// Dynamic value/dim: insert column to the constraint set and put it on the
// worklist. Return an affine expression that represents the newly inserted
// column in the constraint set.
return getPosExpr(insert(value, dim, /*isSymbol=*/true));
}
AffineExpr ValueBoundsConstraintSet::getExpr(OpFoldResult ofr) {
if (Value value = llvm::dyn_cast_if_present<Value>(ofr))
return getExpr(value, /*dim=*/std::nullopt);
auto constInt = ::getConstantIntValue(ofr);
assert(constInt.has_value() && "expected Integer constant");
return builder.getAffineConstantExpr(*constInt);
}
AffineExpr ValueBoundsConstraintSet::getExpr(int64_t constant) {
return builder.getAffineConstantExpr(constant);
}
int64_t ValueBoundsConstraintSet::insert(Value value,
std::optional<int64_t> dim,
bool isSymbol, bool addToWorklist) {
#ifndef NDEBUG
assertValidValueDim(value, dim);
#endif // NDEBUG
ValueDim valueDim = std::make_pair(value, dim.value_or(kIndexValue));
assert(!valueDimToPosition.contains(valueDim) && "already mapped");
int64_t pos = isSymbol ? cstr.appendVar(VarKind::Symbol)
: cstr.appendVar(VarKind::SetDim);
LLVM_DEBUG(llvm::dbgs() << "Inserting constraint set column " << pos
<< " for: " << value
<< " (dim: " << dim.value_or(kIndexValue)
<< ", owner: " << getOwnerOfValue(value)->getName()
<< ")\n");
positionToValueDim.insert(positionToValueDim.begin() + pos, valueDim);
// Update reverse mapping.
for (int64_t i = pos, e = positionToValueDim.size(); i < e; ++i)
if (positionToValueDim[i].has_value())
valueDimToPosition[*positionToValueDim[i]] = i;
if (addToWorklist) {
LLVM_DEBUG(llvm::dbgs() << "Push to worklist: " << value
<< " (dim: " << dim.value_or(kIndexValue) << ")\n");
worklist.push(pos);
}
return pos;
}
int64_t ValueBoundsConstraintSet::insert(bool isSymbol) {
int64_t pos = isSymbol ? cstr.appendVar(VarKind::Symbol)
: cstr.appendVar(VarKind::SetDim);
LLVM_DEBUG(llvm::dbgs() << "Inserting anonymous constraint set column " << pos
<< "\n");
positionToValueDim.insert(positionToValueDim.begin() + pos, std::nullopt);
// Update reverse mapping.
for (int64_t i = pos, e = positionToValueDim.size(); i < e; ++i)
if (positionToValueDim[i].has_value())
valueDimToPosition[*positionToValueDim[i]] = i;
return pos;
}
int64_t ValueBoundsConstraintSet::insert(AffineMap map, ValueDimList operands,
bool isSymbol) {
assert(map.getNumResults() == 1 && "expected affine map with one result");
int64_t pos = insert(isSymbol);
// Add map and operands to the constraint set. Dimensions are converted to
// symbols. All operands are added to the worklist (unless they were already
// processed).
auto mapper = [&](std::pair<Value, std::optional<int64_t>> v) {
return getExpr(v.first, v.second);
};
SmallVector<AffineExpr> dimReplacements = llvm::to_vector(
llvm::map_range(ArrayRef(operands).take_front(map.getNumDims()), mapper));
SmallVector<AffineExpr> symReplacements = llvm::to_vector(
llvm::map_range(ArrayRef(operands).drop_front(map.getNumDims()), mapper));
addBound(
presburger::BoundType::EQ, pos,
map.getResult(0).replaceDimsAndSymbols(dimReplacements, symReplacements));
return pos;
}
int64_t ValueBoundsConstraintSet::insert(const Variable &var, bool isSymbol) {
return insert(var.map, var.mapOperands, isSymbol);
}
int64_t ValueBoundsConstraintSet::getPos(Value value,
std::optional<int64_t> dim) const {
#ifndef NDEBUG
assertValidValueDim(value, dim);
assert((isa<OpResult>(value) ||
cast<BlockArgument>(value).getOwner()->isEntryBlock()) &&
"unstructured control flow is not supported");
#endif // NDEBUG
LLVM_DEBUG(llvm::dbgs() << "Getting pos for: " << value
<< " (dim: " << dim.value_or(kIndexValue)
<< ", owner: " << getOwnerOfValue(value)->getName()
<< ")\n");
auto it =
valueDimToPosition.find(std::make_pair(value, dim.value_or(kIndexValue)));
assert(it != valueDimToPosition.end() && "expected mapped entry");
return it->second;
}
AffineExpr ValueBoundsConstraintSet::getPosExpr(int64_t pos) {
assert(pos >= 0 && pos < cstr.getNumDimAndSymbolVars() && "invalid position");
return pos < cstr.getNumDimVars()
? builder.getAffineDimExpr(pos)
: builder.getAffineSymbolExpr(pos - cstr.getNumDimVars());
}
bool ValueBoundsConstraintSet::isMapped(Value value,
std::optional<int64_t> dim) const {
auto it =
valueDimToPosition.find(std::make_pair(value, dim.value_or(kIndexValue)));
return it != valueDimToPosition.end();
}
void ValueBoundsConstraintSet::processWorklist() {
LLVM_DEBUG(llvm::dbgs() << "Processing value bounds worklist...\n");
while (!worklist.empty()) {
int64_t pos = worklist.front();
worklist.pop();
assert(positionToValueDim[pos].has_value() &&
"did not expect std::nullopt on worklist");
ValueDim valueDim = *positionToValueDim[pos];
Value value = valueDim.first;
int64_t dim = valueDim.second;
// Check for static dim size.
if (dim != kIndexValue) {
auto shapedType = cast<ShapedType>(value.getType());
if (shapedType.hasRank() && !shapedType.isDynamicDim(dim)) {
bound(value)[dim] == getExpr(shapedType.getDimSize(dim));
continue;
}
}
// Do not process any further if the stop condition is met.
auto maybeDim = dim == kIndexValue ? std::nullopt : std::make_optional(dim);
if (stopCondition(value, maybeDim, *this)) {
LLVM_DEBUG(llvm::dbgs() << "Stop condition met for: " << value
<< " (dim: " << maybeDim << ")\n");
continue;
}
// Query `ValueBoundsOpInterface` for constraints. New items may be added to
// the worklist.
auto valueBoundsOp =
dyn_cast<ValueBoundsOpInterface>(getOwnerOfValue(value));
LLVM_DEBUG(llvm::dbgs()
<< "Query value bounds for: " << value
<< " (owner: " << getOwnerOfValue(value)->getName() << ")\n");
if (valueBoundsOp) {
if (dim == kIndexValue) {
valueBoundsOp.populateBoundsForIndexValue(value, *this);
} else {
valueBoundsOp.populateBoundsForShapedValueDim(value, dim, *this);
}
continue;
}
LLVM_DEBUG(llvm::dbgs() << "--> ValueBoundsOpInterface not implemented\n");
// If the op does not implement `ValueBoundsOpInterface`, check if it
// implements the `DestinationStyleOpInterface`. OpResults of such ops are
// tied to OpOperands. Tied values have the same shape.
auto dstOp = value.getDefiningOp<DestinationStyleOpInterface>();
if (!dstOp || dim == kIndexValue)
continue;
Value tiedOperand = dstOp.getTiedOpOperand(cast<OpResult>(value))->get();
bound(value)[dim] == getExpr(tiedOperand, dim);
}
}
void ValueBoundsConstraintSet::projectOut(int64_t pos) {
assert(pos >= 0 && pos < static_cast<int64_t>(positionToValueDim.size()) &&
"invalid position");
cstr.projectOut(pos);
if (positionToValueDim[pos].has_value()) {
bool erased = valueDimToPosition.erase(*positionToValueDim[pos]);
(void)erased;
assert(erased && "inconsistent reverse mapping");
}
positionToValueDim.erase(positionToValueDim.begin() + pos);
// Update reverse mapping.
for (int64_t i = pos, e = positionToValueDim.size(); i < e; ++i)
if (positionToValueDim[i].has_value())
valueDimToPosition[*positionToValueDim[i]] = i;
}
void ValueBoundsConstraintSet::projectOut(
function_ref<bool(ValueDim)> condition) {
int64_t nextPos = 0;
while (nextPos < static_cast<int64_t>(positionToValueDim.size())) {
if (positionToValueDim[nextPos].has_value() &&
condition(*positionToValueDim[nextPos])) {
projectOut(nextPos);
// The column was projected out so another column is now at that position.
// Do not increase the counter.
} else {
++nextPos;
}
}
}
void ValueBoundsConstraintSet::projectOutAnonymous(
std::optional<int64_t> except) {
int64_t nextPos = 0;
while (nextPos < static_cast<int64_t>(positionToValueDim.size())) {
if (positionToValueDim[nextPos].has_value() || except == nextPos) {
++nextPos;
} else {
projectOut(nextPos);
// The column was projected out so another column is now at that position.
// Do not increase the counter.
}
}
}
LogicalResult ValueBoundsConstraintSet::computeBound(
AffineMap &resultMap, ValueDimList &mapOperands, presburger::BoundType type,
const Variable &var, StopConditionFn stopCondition, bool closedUB) {
MLIRContext *ctx = var.getContext();
int64_t ubAdjustment = closedUB ? 0 : 1;
Builder b(ctx);
mapOperands.clear();
// Process the backward slice of `value` (i.e., reverse use-def chain) until
// `stopCondition` is met.
ValueBoundsConstraintSet cstr(ctx, stopCondition);
int64_t pos = cstr.insert(var, /*isSymbol=*/false);
assert(pos == 0 && "expected first column");
cstr.processWorklist();
// Project out all variables (apart from `valueDim`) that do not match the
// stop condition.
cstr.projectOut([&](ValueDim p) {
auto maybeDim =
p.second == kIndexValue ? std::nullopt : std::make_optional(p.second);
return !stopCondition(p.first, maybeDim, cstr);
});
cstr.projectOutAnonymous(/*except=*/pos);
// Compute lower and upper bounds for `valueDim`.
SmallVector<AffineMap> lb(1), ub(1);
cstr.cstr.getSliceBounds(pos, 1, ctx, &lb, &ub,
/*closedUB=*/true);
// Note: There are TODOs in the implementation of `getSliceBounds`. In such a
// case, no lower/upper bound can be computed at the moment.
// EQ, UB bounds: upper bound is needed.
if ((type != BoundType::LB) &&
(ub.empty() || !ub[0] || ub[0].getNumResults() == 0))
return failure();
// EQ, LB bounds: lower bound is needed.
if ((type != BoundType::UB) &&
(lb.empty() || !lb[0] || lb[0].getNumResults() == 0))
return failure();
// TODO: Generate an affine map with multiple results.
if (type != BoundType::LB)
assert(ub.size() == 1 && ub[0].getNumResults() == 1 &&
"multiple bounds not supported");
if (type != BoundType::UB)
assert(lb.size() == 1 && lb[0].getNumResults() == 1 &&
"multiple bounds not supported");
// EQ bound: lower and upper bound must match.
if (type == BoundType::EQ && ub[0] != lb[0])
return failure();
AffineMap bound;
if (type == BoundType::EQ || type == BoundType::LB) {
bound = lb[0];
} else {
// Computed UB is a closed bound.
bound = AffineMap::get(ub[0].getNumDims(), ub[0].getNumSymbols(),
ub[0].getResult(0) + ubAdjustment);
}
// Gather all SSA values that are used in the computed bound.
assert(cstr.cstr.getNumDimAndSymbolVars() == cstr.positionToValueDim.size() &&
"inconsistent mapping state");
SmallVector<AffineExpr> replacementDims, replacementSymbols;
int64_t numDims = 0, numSymbols = 0;
for (int64_t i = 0; i < cstr.cstr.getNumDimAndSymbolVars(); ++i) {
// Skip `value`.
if (i == pos)
continue;
// Check if the position `i` is used in the generated bound. If so, it must
// be included in the generated affine.apply op.
bool used = false;
bool isDim = i < cstr.cstr.getNumDimVars();
if (isDim) {
if (bound.isFunctionOfDim(i))
used = true;
} else {
if (bound.isFunctionOfSymbol(i - cstr.cstr.getNumDimVars()))
used = true;
}
if (!used) {
// Not used: Remove dim/symbol from the result.
if (isDim) {
replacementDims.push_back(b.getAffineConstantExpr(0));
} else {
replacementSymbols.push_back(b.getAffineConstantExpr(0));
}
continue;
}
if (isDim) {
replacementDims.push_back(b.getAffineDimExpr(numDims++));
} else {
replacementSymbols.push_back(b.getAffineSymbolExpr(numSymbols++));
}
assert(cstr.positionToValueDim[i].has_value() &&
"cannot build affine map in terms of anonymous column");
ValueBoundsConstraintSet::ValueDim valueDim = *cstr.positionToValueDim[i];
Value value = valueDim.first;
int64_t dim = valueDim.second;
if (dim == ValueBoundsConstraintSet::kIndexValue) {
// An index-type value is used: can be used directly in the affine.apply
// op.
assert(value.getType().isIndex() && "expected index type");
mapOperands.push_back(std::make_pair(value, std::nullopt));
continue;
}
assert(cast<ShapedType>(value.getType()).isDynamicDim(dim) &&
"expected dynamic dim");
mapOperands.push_back(std::make_pair(value, dim));
}
resultMap = bound.replaceDimsAndSymbols(replacementDims, replacementSymbols,
numDims, numSymbols);
return success();
}
LogicalResult ValueBoundsConstraintSet::computeDependentBound(
AffineMap &resultMap, ValueDimList &mapOperands, presburger::BoundType type,
const Variable &var, ValueDimList dependencies, bool closedUB) {
return computeBound(
resultMap, mapOperands, type, var,
[&](Value v, std::optional<int64_t> d, ValueBoundsConstraintSet &cstr) {
return llvm::is_contained(dependencies, std::make_pair(v, d));
},
closedUB);
}
LogicalResult ValueBoundsConstraintSet::computeIndependentBound(
AffineMap &resultMap, ValueDimList &mapOperands, presburger::BoundType type,
const Variable &var, ValueRange independencies, bool closedUB) {
// Return "true" if the given value is independent of all values in
// `independencies`. I.e., neither the value itself nor any value in the
// backward slice (reverse use-def chain) is contained in `independencies`.
auto isIndependent = [&](Value v) {
SmallVector<Value> worklist;
DenseSet<Value> visited;
worklist.push_back(v);
while (!worklist.empty()) {
Value next = worklist.pop_back_val();
if (visited.contains(next))
continue;
visited.insert(next);
if (llvm::is_contained(independencies, next))
return false;
// TODO: DominanceInfo could be used to stop the traversal early.
Operation *op = next.getDefiningOp();
if (!op)
continue;
worklist.append(op->getOperands().begin(), op->getOperands().end());
}
return true;
};
// Reify bounds in terms of any independent values.
return computeBound(
resultMap, mapOperands, type, var,
[&](Value v, std::optional<int64_t> d, ValueBoundsConstraintSet &cstr) {
return isIndependent(v);
},
closedUB);
}
FailureOr<int64_t> ValueBoundsConstraintSet::computeConstantBound(
presburger::BoundType type, const Variable &var,
StopConditionFn stopCondition, bool closedUB) {
// Default stop condition if none was specified: Keep adding constraints until
// a bound could be computed.
int64_t pos = 0;
auto defaultStopCondition = [&](Value v, std::optional<int64_t> dim,
ValueBoundsConstraintSet &cstr) {
return cstr.cstr.getConstantBound64(type, pos).has_value();
};
ValueBoundsConstraintSet cstr(
var.getContext(), stopCondition ? stopCondition : defaultStopCondition);
pos = cstr.populateConstraints(var.map, var.mapOperands);
assert(pos == 0 && "expected `map` is the first column");
// Compute constant bound for `valueDim`.
int64_t ubAdjustment = closedUB ? 0 : 1;
if (auto bound = cstr.cstr.getConstantBound64(type, pos))
return type == BoundType::UB ? *bound + ubAdjustment : *bound;
return failure();
}
void ValueBoundsConstraintSet::populateConstraints(Value value,
std::optional<int64_t> dim) {
#ifndef NDEBUG
assertValidValueDim(value, dim);
#endif // NDEBUG
// `getExpr` pushes the value/dim onto the worklist (unless it was already
// analyzed).
(void)getExpr(value, dim);
// Process all values/dims on the worklist. This may traverse and analyze
// additional IR, depending the current stop function.
processWorklist();
}
int64_t ValueBoundsConstraintSet::populateConstraints(AffineMap map,
ValueDimList operands) {
int64_t pos = insert(map, operands, /*isSymbol=*/false);
// Process the backward slice of `operands` (i.e., reverse use-def chain)
// until `stopCondition` is met.
processWorklist();
return pos;
}
FailureOr<int64_t>
ValueBoundsConstraintSet::computeConstantDelta(Value value1, Value value2,
std::optional<int64_t> dim1,
std::optional<int64_t> dim2) {
#ifndef NDEBUG
assertValidValueDim(value1, dim1);
assertValidValueDim(value2, dim2);
#endif // NDEBUG
Builder b(value1.getContext());
AffineMap map = AffineMap::get(/*dimCount=*/2, /*symbolCount=*/0,
b.getAffineDimExpr(0) - b.getAffineDimExpr(1));
return computeConstantBound(presburger::BoundType::EQ,
Variable(map, {{value1, dim1}, {value2, dim2}}));
}
bool ValueBoundsConstraintSet::comparePos(int64_t lhsPos,
ComparisonOperator cmp,
int64_t rhsPos) {
// This function returns "true" if "lhs CMP rhs" is proven to hold.
//
// Example for ComparisonOperator::LE and index-typed values: We would like to
// prove that lhs <= rhs. Proof by contradiction: add the inverse
// relation (lhs > rhs) to the constraint set and check if the resulting
// constraint set is "empty" (i.e. has no solution). In that case,
// lhs > rhs must be incorrect and we can deduce that lhs <= rhs holds.
// We cannot prove anything if the constraint set is already empty.
if (cstr.isEmpty()) {
LLVM_DEBUG(
llvm::dbgs()
<< "cannot compare value/dims: constraint system is already empty");
return false;
}
// EQ can be expressed as LE and GE.
if (cmp == EQ)
return comparePos(lhsPos, ComparisonOperator::LE, rhsPos) &&
comparePos(lhsPos, ComparisonOperator::GE, rhsPos);
// Construct inequality.
SmallVector<int64_t> eq(cstr.getNumCols(), 0);
if (cmp == LT || cmp == LE) {
++eq[lhsPos];
--eq[rhsPos];
} else if (cmp == GT || cmp == GE) {
--eq[lhsPos];
++eq[rhsPos];
} else {
llvm_unreachable("unsupported comparison operator");
}
if (cmp == LE || cmp == GE)
eq[cstr.getNumCols() - 1] -= 1;
// Add inequality to the constraint set and check if it made the constraint
// set empty.
int64_t ineqPos = cstr.getNumInequalities();
cstr.addInequality(eq);
bool isEmpty = cstr.isEmpty();
cstr.removeInequality(ineqPos);
return isEmpty;
}
bool ValueBoundsConstraintSet::populateAndCompare(const Variable &lhs,
ComparisonOperator cmp,
const Variable &rhs) {
int64_t lhsPos = populateConstraints(lhs.map, lhs.mapOperands);
int64_t rhsPos = populateConstraints(rhs.map, rhs.mapOperands);
return comparePos(lhsPos, cmp, rhsPos);
}
bool ValueBoundsConstraintSet::compare(const Variable &lhs,
ComparisonOperator cmp,
const Variable &rhs) {
int64_t lhsPos = -1, rhsPos = -1;
auto stopCondition = [&](Value v, std::optional<int64_t> dim,
ValueBoundsConstraintSet &cstr) {
// Keep processing as long as lhs/rhs were not processed.
if (size_t(lhsPos) >= cstr.positionToValueDim.size() ||
size_t(rhsPos) >= cstr.positionToValueDim.size())
return false;
// Keep processing as long as the relation cannot be proven.
return cstr.comparePos(lhsPos, cmp, rhsPos);
};
ValueBoundsConstraintSet cstr(lhs.getContext(), stopCondition);
lhsPos = cstr.populateConstraints(lhs.map, lhs.mapOperands);
rhsPos = cstr.populateConstraints(rhs.map, rhs.mapOperands);
return cstr.comparePos(lhsPos, cmp, rhsPos);
}
FailureOr<bool> ValueBoundsConstraintSet::areEqual(const Variable &var1,
const Variable &var2) {
if (ValueBoundsConstraintSet::compare(var1, ComparisonOperator::EQ, var2))
return true;
if (ValueBoundsConstraintSet::compare(var1, ComparisonOperator::LT, var2) ||
ValueBoundsConstraintSet::compare(var1, ComparisonOperator::GT, var2))
return false;
return failure();
}
FailureOr<bool>
ValueBoundsConstraintSet::areOverlappingSlices(MLIRContext *ctx,
HyperrectangularSlice slice1,
HyperrectangularSlice slice2) {
assert(slice1.getMixedOffsets().size() == slice1.getMixedOffsets().size() &&
"expected slices of same rank");
assert(slice1.getMixedSizes().size() == slice1.getMixedSizes().size() &&
"expected slices of same rank");
assert(slice1.getMixedStrides().size() == slice1.getMixedStrides().size() &&
"expected slices of same rank");
Builder b(ctx);
bool foundUnknownBound = false;
for (int64_t i = 0, e = slice1.getMixedOffsets().size(); i < e; ++i) {
AffineMap map =
AffineMap::get(/*dimCount=*/0, /*symbolCount=*/4,
b.getAffineSymbolExpr(0) +
b.getAffineSymbolExpr(1) * b.getAffineSymbolExpr(2) -
b.getAffineSymbolExpr(3));
{
// Case 1: Slices are guaranteed to be non-overlapping if
// offset1 + size1 * stride1 <= offset2 (for at least one dimension).
SmallVector<OpFoldResult> ofrOperands;
ofrOperands.push_back(slice1.getMixedOffsets()[i]);
ofrOperands.push_back(slice1.getMixedSizes()[i]);
ofrOperands.push_back(slice1.getMixedStrides()[i]);
ofrOperands.push_back(slice2.getMixedOffsets()[i]);
SmallVector<Value> valueOperands;
AffineMap foldedMap =
foldAttributesIntoMap(b, map, ofrOperands, valueOperands);
FailureOr<int64_t> constBound = computeConstantBound(
presburger::BoundType::EQ, Variable(foldedMap, valueOperands));
foundUnknownBound |= failed(constBound);
if (succeeded(constBound) && *constBound <= 0)
return false;
}
{
// Case 2: Slices are guaranteed to be non-overlapping if
// offset2 + size2 * stride2 <= offset1 (for at least one dimension).
SmallVector<OpFoldResult> ofrOperands;
ofrOperands.push_back(slice2.getMixedOffsets()[i]);
ofrOperands.push_back(slice2.getMixedSizes()[i]);
ofrOperands.push_back(slice2.getMixedStrides()[i]);
ofrOperands.push_back(slice1.getMixedOffsets()[i]);
SmallVector<Value> valueOperands;
AffineMap foldedMap =
foldAttributesIntoMap(b, map, ofrOperands, valueOperands);
FailureOr<int64_t> constBound = computeConstantBound(
presburger::BoundType::EQ, Variable(foldedMap, valueOperands));
foundUnknownBound |= failed(constBound);
if (succeeded(constBound) && *constBound <= 0)
return false;
}
}
// If at least one bound could not be computed, we cannot be certain that the
// slices are really overlapping.
if (foundUnknownBound)
return failure();
// All bounds could be computed and none of the above cases applied.
// Therefore, the slices are guaranteed to overlap.
return true;
}
FailureOr<bool>
ValueBoundsConstraintSet::areEquivalentSlices(MLIRContext *ctx,
HyperrectangularSlice slice1,
HyperrectangularSlice slice2) {
assert(slice1.getMixedOffsets().size() == slice1.getMixedOffsets().size() &&
"expected slices of same rank");
assert(slice1.getMixedSizes().size() == slice1.getMixedSizes().size() &&
"expected slices of same rank");
assert(slice1.getMixedStrides().size() == slice1.getMixedStrides().size() &&
"expected slices of same rank");
// The two slices are equivalent if all of their offsets, sizes and strides
// are equal. If equality cannot be determined for at least one of those
// values, equivalence cannot be determined and this function returns
// "failure".
for (auto [offset1, offset2] :
llvm::zip_equal(slice1.getMixedOffsets(), slice2.getMixedOffsets())) {
FailureOr<bool> equal = areEqual(offset1, offset2);
if (failed(equal))
return failure();
if (!equal.value())
return false;
}
for (auto [size1, size2] :
llvm::zip_equal(slice1.getMixedSizes(), slice2.getMixedSizes())) {
FailureOr<bool> equal = areEqual(size1, size2);
if (failed(equal))
return failure();
if (!equal.value())
return false;
}
for (auto [stride1, stride2] :
llvm::zip_equal(slice1.getMixedStrides(), slice2.getMixedStrides())) {
FailureOr<bool> equal = areEqual(stride1, stride2);
if (failed(equal))
return failure();
if (!equal.value())
return false;
}
return true;
}
void ValueBoundsConstraintSet::dump() const {
llvm::errs() << "==========\nColumns:\n";
llvm::errs() << "(column\tdim\tvalue)\n";
for (auto [index, valueDim] : llvm::enumerate(positionToValueDim)) {
llvm::errs() << " " << index << "\t";
if (valueDim) {
if (valueDim->second == kIndexValue) {
llvm::errs() << "n/a\t";
} else {
llvm::errs() << valueDim->second << "\t";
}
llvm::errs() << getOwnerOfValue(valueDim->first)->getName() << " ";
if (OpResult result = dyn_cast<OpResult>(valueDim->first)) {
llvm::errs() << "(result " << result.getResultNumber() << ")";
} else {
llvm::errs() << "(bbarg "
<< cast<BlockArgument>(valueDim->first).getArgNumber()
<< ")";
}
llvm::errs() << "\n";
} else {
llvm::errs() << "n/a\tn/a\n";
}
}
llvm::errs() << "\nConstraint set:\n";
cstr.dump();
llvm::errs() << "==========\n";
}
ValueBoundsConstraintSet::BoundBuilder &
ValueBoundsConstraintSet::BoundBuilder::operator[](int64_t dim) {
assert(!this->dim.has_value() && "dim was already set");
this->dim = dim;
#ifndef NDEBUG
assertValidValueDim(value, this->dim);
#endif // NDEBUG
return *this;
}
void ValueBoundsConstraintSet::BoundBuilder::operator<(AffineExpr expr) {
#ifndef NDEBUG
assertValidValueDim(value, this->dim);
#endif // NDEBUG
cstr.addBound(BoundType::UB, cstr.getPos(value, this->dim), expr);
}
void ValueBoundsConstraintSet::BoundBuilder::operator<=(AffineExpr expr) {
operator<(expr + 1);
}
void ValueBoundsConstraintSet::BoundBuilder::operator>(AffineExpr expr) {
operator>=(expr + 1);
}
void ValueBoundsConstraintSet::BoundBuilder::operator>=(AffineExpr expr) {
#ifndef NDEBUG
assertValidValueDim(value, this->dim);
#endif // NDEBUG
cstr.addBound(BoundType::LB, cstr.getPos(value, this->dim), expr);
}
void ValueBoundsConstraintSet::BoundBuilder::operator==(AffineExpr expr) {
#ifndef NDEBUG
assertValidValueDim(value, this->dim);
#endif // NDEBUG
cstr.addBound(BoundType::EQ, cstr.getPos(value, this->dim), expr);
}
void ValueBoundsConstraintSet::BoundBuilder::operator<(OpFoldResult ofr) {
operator<(cstr.getExpr(ofr));
}
void ValueBoundsConstraintSet::BoundBuilder::operator<=(OpFoldResult ofr) {
operator<=(cstr.getExpr(ofr));
}
void ValueBoundsConstraintSet::BoundBuilder::operator>(OpFoldResult ofr) {
operator>(cstr.getExpr(ofr));
}
void ValueBoundsConstraintSet::BoundBuilder::operator>=(OpFoldResult ofr) {
operator>=(cstr.getExpr(ofr));
}
void ValueBoundsConstraintSet::BoundBuilder::operator==(OpFoldResult ofr) {
operator==(cstr.getExpr(ofr));
}
void ValueBoundsConstraintSet::BoundBuilder::operator<(int64_t i) {
operator<(cstr.getExpr(i));
}
void ValueBoundsConstraintSet::BoundBuilder::operator<=(int64_t i) {
operator<=(cstr.getExpr(i));
}
void ValueBoundsConstraintSet::BoundBuilder::operator>(int64_t i) {
operator>(cstr.getExpr(i));
}
void ValueBoundsConstraintSet::BoundBuilder::operator>=(int64_t i) {
operator>=(cstr.getExpr(i));
}
void ValueBoundsConstraintSet::BoundBuilder::operator==(int64_t i) {
operator==(cstr.getExpr(i));
}
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