Transforms.h

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//===- Transforms.h - Transforms Entrypoints --------------------*- C++ -*-===//
//
// 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
//
//===----------------------------------------------------------------------===//
//
// This header file defines a set of transforms specific for the AffineOps
// dialect.
//
//===----------------------------------------------------------------------===//
 
#ifndef MLIR_DIALECT_AFFINE_TRANSFORMS_TRANSFORMS_H
#define MLIR_DIALECT_AFFINE_TRANSFORMS_TRANSFORMS_H
 
#include "mlir/Interfaces/ValueBoundsOpInterface.h"
#include "mlir/Support/LLVM.h"
 
namespace mlir {
class AffineMap;
class Location;
class OpBuilder;
class OpFoldResult;
class RewritePatternSet;
class RewriterBase;
class Value;
 
namespace presburger {
enum class BoundType;
} // namespace presburger
 
namespace affine {
class AffineApplyOp;
class AffineDelinearizeIndexOp;
class AffineLinearizeIndexOp;
class AffineMaxOp;
class AffineMinOp;
 
/// Lowers `affine.delinearize_index` into a sequence of division and remainder
/// operations.
LogicalResult lowerAffineDelinearizeIndexOp(RewriterBase &rewriter,
                                            AffineDelinearizeIndexOp op);
 
/// Lowers `affine.linearize_index` into a sequence of multiplications and
/// additions. Make a best effort to sort the input indices so that
/// the most loop-invariant terms are at the left of the additions
/// to enable loop-invariant code motion.
LogicalResult lowerAffineLinearizeIndexOp(RewriterBase &rewriter,
                                          AffineLinearizeIndexOp op);
 
/// Populate patterns that simplify `affine.delinearize_index` /
/// `affine.linearize_index` pairs using value bounds analysis.
void populateSimplifyAffineWithBoundsPatterns(RewritePatternSet &patterns);
 
/// Populate patterns that expand affine index operations into more fundamental
/// operations (not necessarily restricted to Affine dialect).
void populateAffineExpandIndexOpsPatterns(RewritePatternSet &patterns);
 
/// Populate patterns that expand affine index operations into their equivalent
/// `affine.apply` representations.
void populateAffineExpandIndexOpsAsAffinePatterns(RewritePatternSet &patterns);
 
/// Helper function to rewrite `op`'s affine map and reorder its operands such
/// that they are in increasing order of hoistability (i.e. the least hoistable)
/// operands come first in the operand list.
void reorderOperandsByHoistability(RewriterBase &rewriter, AffineApplyOp op);
 
/// Split an "affine.apply" operation into smaller ops.
/// This reassociates a large AffineApplyOp into an ordered list of smaller
/// AffineApplyOps. This can be used right before lowering affine ops to arith
/// to exhibit more opportunities for CSE and LICM.
/// Return the sink AffineApplyOp on success or failure if `op` does not
/// decompose into smaller AffineApplyOps.
/// Note that this can be undone by canonicalization which tries to
/// maximally compose chains of AffineApplyOps.
FailureOr<AffineApplyOp> decompose(RewriterBase &rewriter, AffineApplyOp op);
 
/// Reify a bound for the given variable in terms of SSA values for which
/// `stopCondition` is met.
///
/// By default, lower/equal bounds are closed and upper bounds are open. If
/// `closedUB` is set to "true", upper bounds are also closed.
FailureOr<OpFoldResult>
reifyValueBound(OpBuilder &b, Location loc, presburger::BoundType type,
                const ValueBoundsConstraintSet::Variable &var,
                ValueBoundsConstraintSet::StopConditionFn stopCondition,
                bool closedUB = false);
 
/// Reify a bound for the given index-typed value in terms of SSA values for
/// which `stopCondition` is met. If no stop condition is specified, reify in
/// terms of the operands of the owner op.
///
/// By default, lower/equal bounds are closed and upper bounds are open. If
/// `closedUB` is set to "true", upper bounds are also closed.
///
/// Example:
/// %0 = arith.addi %a, %b : index
/// %1 = arith.addi %0, %c : index
///
/// * If `stopCondition` evaluates to "true" for %0 and %c, "%0 + %c" is an EQ
///   bound for %1.
/// * If `stopCondition` evaluates to "true" for %a, %b and %c, "%a + %b + %c"
///   is an EQ bound for %1.
/// * Otherwise, if the owners of %a, %b or %c do not implement the
///   ValueBoundsOpInterface, no bound can be computed.
FailureOr<OpFoldResult> reifyIndexValueBound(
    OpBuilder &b, Location loc, presburger::BoundType type, Value value,
    ValueBoundsConstraintSet::StopConditionFn stopCondition = nullptr,
    bool closedUB = false);
 
/// Reify a bound for the specified dimension of the given shaped value in terms
/// of SSA values for which `stopCondition` is met. If no stop condition is
/// specified, reify in terms of the operands of the owner op.
///
/// By default, lower/equal bounds are closed and upper bounds are open. If
/// `closedUB` is set to "true", upper bounds are also closed.
FailureOr<OpFoldResult> reifyShapedValueDimBound(
    OpBuilder &b, Location loc, presburger::BoundType type, Value value,
    int64_t dim,
    ValueBoundsConstraintSet::StopConditionFn stopCondition = nullptr,
    bool closedUB = false);
 
/// Materialize an already computed bound with Affine dialect ops.
///
/// * `ValueBoundsOpInterface::computeBound` computes bounds but does not
///   create IR. It is dialect independent.
/// * `materializeComputedBound` materializes computed bounds with Affine
///   dialect ops.
/// * `reifyIndexValueBound`/`reifyShapedValueDimBound` are a combination of
///   the two functions mentioned above.
OpFoldResult materializeComputedBound(
    OpBuilder &b, Location loc, AffineMap boundMap,
    ArrayRef<std::pair<Value, std::optional<int64_t>>> mapOperands);
 
/// This transform tries to simplify the affine min operation `op`, by finding a
/// common lower bound for a set of expressions in the affine map results. It
/// returns whether the transform updated `op`'s affine map.
///
/// In concrete terms, given an operation like:
/// `affine.min affine_map<(d0)[s0, s1] -> (d0, s1, s0, 128)>(%i)[%s0, %s1]`
/// If `d0 < 128` and `128 < s1 < s0`, the transform will update `op` to:
/// `affine.min affine_map<(d0)[s0, s1] -> (d0, 128)>(%i)[%s0, %s1]`.
bool simplifyAffineMinOp(RewriterBase &rewriter, AffineMinOp op);
 
/// This transform tries to simplify the affine max operation `op`, by finding a
/// common upper bound for a set of expressions in the affine map results. It
/// returns whether the transform updated `op`'s affine map.
///
/// In concrete terms, given an operation like:
/// `affine.max affine_map<(d0)[s0, s1] -> (d0, s1, s0, 128)>(%i)[%s0, %s1]`
/// If `d0 > 128` and `s0 > s1 > 128`, the transform will update `op` to:
/// `affine.max affine_map<(d0)[s0, s1] -> (d0, s0)>(%i)[%s0, %s1]`.
bool simplifyAffineMaxOp(RewriterBase &rewriter, AffineMaxOp op);
 
/// This transform applies `simplifyAffineMinOp` and `simplifyAffineMaxOp` to
/// all the `affine.min` or `affine.max` operations in `ops`. After
/// simplification, it invokes the `affine.min/max` canonicalization patterns on
/// `ops`.
///
/// This transform returns failure if the greedy pattern rewriter failed to
/// converge during canonicalization, otherwise it returns success. If provided,
/// `modified` is set to `true` if the IR was modified in any way.
LogicalResult simplifyAffineMinMaxOps(RewriterBase &rewriter,
                                      ArrayRef<Operation *> ops,
                                      bool *modified = nullptr);
} // namespace affine
} // namespace mlir
 
#endif // MLIR_DIALECT_AFFINE_TRANSFORMS_TRANSFORMS_H