diff --git a/mlir/include/mlir/Interfaces/ValueBoundsOpInterface.h b/mlir/include/mlir/Interfaces/ValueBoundsOpInterface.h index 83107a3f5f941..3543ab52407a3 100644 --- a/mlir/include/mlir/Interfaces/ValueBoundsOpInterface.h +++ b/mlir/include/mlir/Interfaces/ValueBoundsOpInterface.h @@ -203,6 +203,26 @@ class ValueBoundsConstraintSet std::optional dim1 = std::nullopt, std::optional dim2 = std::nullopt); + /// Traverse the IR starting from the given value/dim and populate constraints + /// as long as the stop condition holds. Also process all values/dims that are + /// already on the worklist. + void populateConstraints(Value value, std::optional dim); + + /// Comparison operator for `ValueBoundsConstraintSet::compare`. + enum ComparisonOperator { LT, LE, EQ, GT, GE }; + + /// Try to prove that, based on the current state of this constraint set + /// (i.e., without analyzing additional IR or adding new constraints), the + /// "lhs" value/dim is LE/LT/EQ/GT/GE than the "rhs" value/dim. + /// + /// Return "true" if the specified relation between the two values/dims was + /// proven to hold. Return "false" if the specified relation could not be + /// proven. This could be because the specified relation does in fact not hold + /// or because there is not enough information in the constraint set. In other + /// words, if we do not know for sure, this function returns "false". + bool compare(Value lhs, std::optional lhsDim, ComparisonOperator cmp, + Value rhs, std::optional rhsDim); + /// Compute whether the given values/dimensions are equal. Return "failure" if /// equality could not be determined. /// @@ -274,13 +294,13 @@ class ValueBoundsConstraintSet ValueBoundsConstraintSet(MLIRContext *ctx, StopConditionFn stopCondition); - /// Populates the constraint set for a value/map without actually computing - /// the bound. Returns the position for the value/map (via the return value - /// and `posOut` output parameter). - int64_t populateConstraintsSet(Value value, - std::optional dim = std::nullopt); - int64_t populateConstraintsSet(AffineMap map, ValueDimList mapOperands, - int64_t *posOut = nullptr); + /// Given an affine map with a single result (and map operands), add a new + /// column to the constraint set that represents the result of the map. + /// Traverse additional IR starting from the map operands as needed (as long + /// as the stop condition is not satisfied). Also process all values/dims that + /// are already on the worklist. Return the position of the newly added + /// column. + int64_t populateConstraints(AffineMap map, ValueDimList mapOperands); /// Iteratively process all elements on the worklist until an index-typed /// value or shaped value meets `stopCondition`. Such values are not processed @@ -295,14 +315,19 @@ class ValueBoundsConstraintSet /// value/dimension exists in the constraint set. int64_t getPos(Value value, std::optional dim = std::nullopt) const; + /// Return an affine expression that represents column `pos` in the constraint + /// set. + AffineExpr getPosExpr(int64_t pos); + /// Insert a value/dimension into the constraint set. If `isSymbol` is set to /// "false", a dimension is added. The value/dimension is added to the - /// worklist. + /// worklist if `addToWorklist` is set. /// /// Note: There are certain affine restrictions wrt. dimensions. E.g., they /// cannot be multiplied. Furthermore, bounds can only be queried for /// dimensions but not for symbols. - int64_t insert(Value value, std::optional dim, bool isSymbol = true); + int64_t insert(Value value, std::optional dim, bool isSymbol = true, + bool addToWorklist = true); /// Insert an anonymous column into the constraint set. The column is not /// bound to any value/dimension. If `isSymbol` is set to "false", a dimension diff --git a/mlir/lib/Dialect/SCF/IR/ValueBoundsOpInterfaceImpl.cpp b/mlir/lib/Dialect/SCF/IR/ValueBoundsOpInterfaceImpl.cpp index 1e13e60068ee7..8e9d1021f93e4 100644 --- a/mlir/lib/Dialect/SCF/IR/ValueBoundsOpInterfaceImpl.cpp +++ b/mlir/lib/Dialect/SCF/IR/ValueBoundsOpInterfaceImpl.cpp @@ -111,6 +111,66 @@ struct ForOpInterface } }; +struct IfOpInterface + : public ValueBoundsOpInterface::ExternalModel { + + static void populateBounds(scf::IfOp ifOp, Value value, + std::optional dim, + ValueBoundsConstraintSet &cstr) { + unsigned int resultNum = cast(value).getResultNumber(); + Value thenValue = ifOp.thenYield().getResults()[resultNum]; + Value elseValue = ifOp.elseYield().getResults()[resultNum]; + + // Populate constraints for the yielded value (and all values on the + // backward slice, as long as the current stop condition is not satisfied). + cstr.populateConstraints(thenValue, dim); + cstr.populateConstraints(elseValue, dim); + auto boundsBuilder = cstr.bound(value); + if (dim) + boundsBuilder[*dim]; + + // Compare yielded values. + // If thenValue <= elseValue: + // * result <= elseValue + // * result >= thenValue + if (cstr.compare(thenValue, dim, + ValueBoundsConstraintSet::ComparisonOperator::LE, + elseValue, dim)) { + if (dim) { + cstr.bound(value)[*dim] >= cstr.getExpr(thenValue, dim); + cstr.bound(value)[*dim] <= cstr.getExpr(elseValue, dim); + } else { + cstr.bound(value) >= thenValue; + cstr.bound(value) <= elseValue; + } + } + // If elseValue <= thenValue: + // * result <= thenValue + // * result >= elseValue + if (cstr.compare(elseValue, dim, + ValueBoundsConstraintSet::ComparisonOperator::LE, + thenValue, dim)) { + if (dim) { + cstr.bound(value)[*dim] >= cstr.getExpr(elseValue, dim); + cstr.bound(value)[*dim] <= cstr.getExpr(thenValue, dim); + } else { + cstr.bound(value) >= elseValue; + cstr.bound(value) <= thenValue; + } + } + } + + void populateBoundsForIndexValue(Operation *op, Value value, + ValueBoundsConstraintSet &cstr) const { + populateBounds(cast(op), value, /*dim=*/std::nullopt, cstr); + } + + void populateBoundsForShapedValueDim(Operation *op, Value value, int64_t dim, + ValueBoundsConstraintSet &cstr) const { + populateBounds(cast(op), value, dim, cstr); + } +}; + } // namespace } // namespace scf } // namespace mlir @@ -119,5 +179,6 @@ void mlir::scf::registerValueBoundsOpInterfaceExternalModels( DialectRegistry ®istry) { registry.addExtension(+[](MLIRContext *ctx, scf::SCFDialect *dialect) { scf::ForOp::attachInterface(*ctx); + scf::IfOp::attachInterface(*ctx); }); } diff --git a/mlir/lib/Dialect/Vector/IR/ScalableValueBoundsConstraintSet.cpp b/mlir/lib/Dialect/Vector/IR/ScalableValueBoundsConstraintSet.cpp index 52359fa8a510d..f8df34843a363 100644 --- a/mlir/lib/Dialect/Vector/IR/ScalableValueBoundsConstraintSet.cpp +++ b/mlir/lib/Dialect/Vector/IR/ScalableValueBoundsConstraintSet.cpp @@ -59,12 +59,16 @@ ScalableValueBoundsConstraintSet::computeScalableBound( ScalableValueBoundsConstraintSet scalableCstr( value.getContext(), stopCondition ? stopCondition : defaultStopCondition, vscaleMin, vscaleMax); - int64_t pos = scalableCstr.populateConstraintsSet(value, dim); + int64_t pos = scalableCstr.insert(value, dim, /*isSymbol=*/false); + scalableCstr.processWorklist(); - // Project out all variables apart from vscale. - // This should result in constraints in terms of vscale only. + // Project out all columns apart from vscale and the starting point + // (value/dim). This should result in constraints in terms of vscale only. auto projectOutFn = [&](ValueDim p) { - return p.first != scalableCstr.getVscaleValue(); + bool isStartingPoint = + p.first == value && + p.second == dim.value_or(ValueBoundsConstraintSet::kIndexValue); + return p.first != scalableCstr.getVscaleValue() && !isStartingPoint; }; scalableCstr.projectOut(projectOutFn); @@ -72,7 +76,7 @@ ScalableValueBoundsConstraintSet::computeScalableBound( scalableCstr.positionToValueDim.size() && "inconsistent mapping state"); - // Check that the only symbols left are vscale. + // Check that the only columns left are vscale and the starting point. for (int64_t i = 0; i < scalableCstr.cstr.getNumDimAndSymbolVars(); ++i) { if (i == pos) continue; diff --git a/mlir/lib/Interfaces/ValueBoundsOpInterface.cpp b/mlir/lib/Interfaces/ValueBoundsOpInterface.cpp index 0d362c7efa0a0..6e3d6dd3c7575 100644 --- a/mlir/lib/Interfaces/ValueBoundsOpInterface.cpp +++ b/mlir/lib/Interfaces/ValueBoundsOpInterface.cpp @@ -110,25 +110,47 @@ AffineExpr ValueBoundsConstraintSet::getExpr(Value value, 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 constSize = std::nullopt; auto shapedType = dyn_cast(value.getType()); if (shapedType) { - // Static dimension: return constant directly. if (shapedType.hasRank() && !shapedType.isDynamicDim(*dim)) - return builder.getAffineConstantExpr(shapedType.getDimSize(*dim)); - } else { - // Constant index value: return directly. - if (auto constInt = ::getConstantIntValue(value)) - return builder.getAffineConstantExpr(*constInt); + constSize = shapedType.getDimSize(*dim); + } else if (auto constInt = ::getConstantIntValue(value)) { + constSize = *constInt; } - // Dynamic value: add to constraint set. + // 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)) - (void)insert(value, dim); - int64_t pos = getPos(value, dim); - return pos < cstr.getNumDimVars() - ? builder.getAffineDimExpr(pos) - : builder.getAffineSymbolExpr(pos - cstr.getNumDimVars()); + 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) { @@ -145,7 +167,7 @@ AffineExpr ValueBoundsConstraintSet::getExpr(int64_t constant) { int64_t ValueBoundsConstraintSet::insert(Value value, std::optional dim, - bool isSymbol) { + bool isSymbol, bool addToWorklist) { #ifndef NDEBUG assertValidValueDim(value, dim); #endif // NDEBUG @@ -160,7 +182,12 @@ int64_t ValueBoundsConstraintSet::insert(Value value, if (positionToValueDim[i].has_value()) valueDimToPosition[*positionToValueDim[i]] = i; - worklist.push(pos); + if (addToWorklist) { + LLVM_DEBUG(llvm::dbgs() << "Push to worklist: " << value + << " (dim: " << dim.value_or(kIndexValue) << ")\n"); + worklist.push(pos); + } + return pos; } @@ -190,6 +217,13 @@ int64_t ValueBoundsConstraintSet::getPos(Value value, 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()); +} + static Operation *getOwnerOfValue(Value value) { if (auto bbArg = dyn_cast(value)) return bbArg.getOwner()->getParentOp(); @@ -492,7 +526,7 @@ FailureOr ValueBoundsConstraintSet::computeConstantBound( // Default stop condition if none was specified: Keep adding constraints until // a bound could be computed. - int64_t pos; + int64_t pos = 0; auto defaultStopCondition = [&](Value v, std::optional dim, ValueBoundsConstraintSet &cstr) { return cstr.cstr.getConstantBound64(type, pos).has_value(); @@ -500,7 +534,8 @@ FailureOr ValueBoundsConstraintSet::computeConstantBound( ValueBoundsConstraintSet cstr( map.getContext(), stopCondition ? stopCondition : defaultStopCondition); - cstr.populateConstraintsSet(map, operands, &pos); + pos = cstr.populateConstraints(map, operands); + assert(pos == 0 && "expected `map` is the first column"); // Compute constant bound for `valueDim`. int64_t ubAdjustment = closedUB ? 0 : 1; @@ -509,29 +544,28 @@ FailureOr ValueBoundsConstraintSet::computeConstantBound( return failure(); } -int64_t -ValueBoundsConstraintSet::populateConstraintsSet(Value value, - std::optional dim) { +void ValueBoundsConstraintSet::populateConstraints(Value value, + std::optional dim) { #ifndef NDEBUG assertValidValueDim(value, dim); #endif // NDEBUG - AffineMap map = - AffineMap::get(/*dimCount=*/1, /*symbolCount=*/0, - Builder(value.getContext()).getAffineDimExpr(0)); - return populateConstraintsSet(map, {{value, dim}}); + // `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::populateConstraintsSet(AffineMap map, - ValueDimList operands, - int64_t *posOut) { +int64_t ValueBoundsConstraintSet::populateConstraints(AffineMap map, + ValueDimList operands) { assert(map.getNumResults() == 1 && "expected affine map with one result"); int64_t pos = insert(/*isSymbol=*/false); - if (posOut) - *posOut = pos; // Add map and operands to the constraint set. Dimensions are converted to - // symbols. All operands are added to the worklist. + // symbols. All operands are added to the worklist (unless they were already + // processed). auto mapper = [&](std::pair> v) { return getExpr(v.first, v.second); }; @@ -566,6 +600,55 @@ ValueBoundsConstraintSet::computeConstantDelta(Value value1, Value value2, {{value1, dim1}, {value2, dim2}}); } +bool ValueBoundsConstraintSet::compare(Value lhs, std::optional lhsDim, + ComparisonOperator cmp, Value rhs, + std::optional rhsDim) { + // 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 compare(lhs, lhsDim, ComparisonOperator::LE, rhs, rhsDim) && + compare(lhs, lhsDim, ComparisonOperator::GE, rhs, rhsDim); + + // Construct inequality. For the above example: lhs > rhs. + // `IntegerRelation` inequalities are expressed in the "flattened" form and + // with ">= 0". I.e., lhs - rhs - 1 >= 0. + SmallVector eq(cstr.getNumDimAndSymbolVars() + 1, 0); + if (cmp == LT || cmp == LE) { + ++eq[getPos(lhs, lhsDim)]; + --eq[getPos(rhs, rhsDim)]; + } else if (cmp == GT || cmp == GE) { + --eq[getPos(lhs, lhsDim)]; + ++eq[getPos(rhs, rhsDim)]; + } else { + llvm_unreachable("unsupported comparison operator"); + } + if (cmp == LE || cmp == GE) + eq[cstr.getNumDimAndSymbolVars()] -= 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; +} + FailureOr ValueBoundsConstraintSet::areEqual(Value value1, Value value2, std::optional dim1, diff --git a/mlir/test/Dialect/SCF/value-bounds-op-interface-impl.mlir b/mlir/test/Dialect/SCF/value-bounds-op-interface-impl.mlir index e4d7141592499..0ea06737886d4 100644 --- a/mlir/test/Dialect/SCF/value-bounds-op-interface-impl.mlir +++ b/mlir/test/Dialect/SCF/value-bounds-op-interface-impl.mlir @@ -1,5 +1,5 @@ -// RUN: mlir-opt %s -test-affine-reify-value-bounds -verify-diagnostics \ -// RUN: -split-input-file | FileCheck %s +// RUN: mlir-opt %s -test-affine-reify-value-bounds="reify-to-func-args" \ +// RUN: -verify-diagnostics -split-input-file | FileCheck %s // CHECK-LABEL: func @scf_for( // CHECK-SAME: %[[a:.*]]: index, %[[b:.*]]: index, %[[c:.*]]: index @@ -104,3 +104,118 @@ func.func @scf_for_swapping_yield(%t1: tensor, %t2: tensor, %a: in "test.some_use"(%reify1) : (index) -> () return } + +// ----- + +// CHECK-LABEL: func @scf_if_constant( +func.func @scf_if_constant(%c : i1) { + // CHECK: arith.constant 4 : index + // CHECK: arith.constant 9 : index + %c4 = arith.constant 4 : index + %c9 = arith.constant 9 : index + %r = scf.if %c -> index { + scf.yield %c4 : index + } else { + scf.yield %c9 : index + } + + // CHECK: %[[c4:.*]] = arith.constant 4 : index + // CHECK: %[[c10:.*]] = arith.constant 10 : index + %reify1 = "test.reify_bound"(%r) {type = "LB"} : (index) -> (index) + %reify2 = "test.reify_bound"(%r) {type = "UB"} : (index) -> (index) + // CHECK: "test.some_use"(%[[c4]], %[[c10]]) + "test.some_use"(%reify1, %reify2) : (index, index) -> () + return +} + +// ----- + +// CHECK: #[[$map:.*]] = affine_map<()[s0, s1] -> (s0 + s1)> +// CHECK: #[[$map1:.*]] = affine_map<()[s0, s1] -> (s0 + s1 + 5)> +// CHECK-LABEL: func @scf_if_dynamic( +// CHECK-SAME: %[[a:.*]]: index, %[[b:.*]]: index, %{{.*}}: i1) +func.func @scf_if_dynamic(%a: index, %b: index, %c : i1) { + %c4 = arith.constant 4 : index + %r = scf.if %c -> index { + %add1 = arith.addi %a, %b : index + scf.yield %add1 : index + } else { + %add2 = arith.addi %b, %c4 : index + %add3 = arith.addi %add2, %a : index + scf.yield %add3 : index + } + + // CHECK: %[[lb:.*]] = affine.apply #[[$map]]()[%[[a]], %[[b]]] + // CHECK: %[[ub:.*]] = affine.apply #[[$map1]]()[%[[a]], %[[b]]] + %reify1 = "test.reify_bound"(%r) {type = "LB"} : (index) -> (index) + %reify2 = "test.reify_bound"(%r) {type = "UB"} : (index) -> (index) + // CHECK: "test.some_use"(%[[lb]], %[[ub]]) + "test.some_use"(%reify1, %reify2) : (index, index) -> () + return +} + +// ----- + +func.func @scf_if_no_affine_bound(%a: index, %b: index, %c : i1) { + %r = scf.if %c -> index { + scf.yield %a : index + } else { + scf.yield %b : index + } + // The reified bound would be min(%a, %b). min/max expressions are not + // supported in reified bounds. + // expected-error @below{{could not reify bound}} + %reify1 = "test.reify_bound"(%r) {type = "LB"} : (index) -> (index) + "test.some_use"(%reify1) : (index) -> () + return +} + +// ----- + +// CHECK-LABEL: func @scf_if_tensor_dim( +func.func @scf_if_tensor_dim(%c : i1) { + // CHECK: arith.constant 4 : index + // CHECK: arith.constant 9 : index + %c4 = arith.constant 4 : index + %c9 = arith.constant 9 : index + %t1 = tensor.empty(%c4) : tensor + %t2 = tensor.empty(%c9) : tensor + %r = scf.if %c -> tensor { + scf.yield %t1 : tensor + } else { + scf.yield %t2 : tensor + } + + // CHECK: %[[c4:.*]] = arith.constant 4 : index + // CHECK: %[[c10:.*]] = arith.constant 10 : index + %reify1 = "test.reify_bound"(%r) {type = "LB", dim = 0} + : (tensor) -> (index) + %reify2 = "test.reify_bound"(%r) {type = "UB", dim = 0} + : (tensor) -> (index) + // CHECK: "test.some_use"(%[[c4]], %[[c10]]) + "test.some_use"(%reify1, %reify2) : (index, index) -> () + return +} + +// ----- + +// CHECK: #[[$map:.*]] = affine_map<()[s0, s1] -> (s0 + s1)> +// CHECK-LABEL: func @scf_if_eq( +// CHECK-SAME: %[[a:.*]]: index, %[[b:.*]]: index, %{{.*}}: i1) +func.func @scf_if_eq(%a: index, %b: index, %c : i1) { + %c0 = arith.constant 0 : index + %r = scf.if %c -> index { + %add1 = arith.addi %a, %b : index + scf.yield %add1 : index + } else { + %add2 = arith.addi %b, %c0 : index + %add3 = arith.addi %add2, %a : index + scf.yield %add3 : index + } + + // CHECK: %[[eq:.*]] = affine.apply #[[$map]]()[%[[a]], %[[b]]] + %reify1 = "test.reify_bound"(%r) {type = "EQ"} : (index) -> (index) + // CHECK: "test.some_use"(%[[eq]]) + "test.some_use"(%reify1) : (index) -> () + return +}