forked from OSchip/llvm-project
142 lines
5.8 KiB
C++
142 lines
5.8 KiB
C++
//===- BufferUtils.cpp - buffer transformation utilities ------------------===//
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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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//
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// This file implements utilities for buffer optimization passes.
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//
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//===----------------------------------------------------------------------===//
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#include "mlir/Transforms/BufferUtils.h"
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#include "PassDetail.h"
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#include "mlir/Dialect/MemRef/Utils/MemRefUtils.h"
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#include "mlir/Dialect/StandardOps/IR/Ops.h"
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#include "mlir/IR/Operation.h"
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#include "mlir/Interfaces/ControlFlowInterfaces.h"
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#include "mlir/Interfaces/LoopLikeInterface.h"
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#include "mlir/Pass/Pass.h"
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#include "mlir/Transforms/Passes.h"
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#include "llvm/ADT/SetOperations.h"
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using namespace mlir;
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//===----------------------------------------------------------------------===//
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// BufferPlacementAllocs
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//===----------------------------------------------------------------------===//
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/// Get the start operation to place the given alloc value withing the
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// specified placement block.
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Operation *BufferPlacementAllocs::getStartOperation(Value allocValue,
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Block *placementBlock,
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const Liveness &liveness) {
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// We have to ensure that we place the alloc before its first use in this
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// block.
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const LivenessBlockInfo &livenessInfo = *liveness.getLiveness(placementBlock);
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Operation *startOperation = livenessInfo.getStartOperation(allocValue);
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// Check whether the start operation lies in the desired placement block.
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// If not, we will use the terminator as this is the last operation in
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// this block.
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if (startOperation->getBlock() != placementBlock) {
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Operation *opInPlacementBlock =
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placementBlock->findAncestorOpInBlock(*startOperation);
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startOperation = opInPlacementBlock ? opInPlacementBlock
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: placementBlock->getTerminator();
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}
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return startOperation;
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}
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/// Initializes the internal list by discovering all supported allocation
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/// nodes.
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BufferPlacementAllocs::BufferPlacementAllocs(Operation *op) { build(op); }
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/// Searches for and registers all supported allocation entries.
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void BufferPlacementAllocs::build(Operation *op) {
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op->walk([&](MemoryEffectOpInterface opInterface) {
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// Try to find a single allocation result.
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SmallVector<MemoryEffects::EffectInstance, 2> effects;
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opInterface.getEffects(effects);
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SmallVector<MemoryEffects::EffectInstance, 2> allocateResultEffects;
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llvm::copy_if(
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effects, std::back_inserter(allocateResultEffects),
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[=](MemoryEffects::EffectInstance &it) {
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Value value = it.getValue();
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return isa<MemoryEffects::Allocate>(it.getEffect()) && value &&
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value.isa<OpResult>() &&
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it.getResource() !=
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SideEffects::AutomaticAllocationScopeResource::get();
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});
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// If there is one result only, we will be able to move the allocation and
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// (possibly existing) deallocation ops.
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if (allocateResultEffects.size() != 1)
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return;
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// Get allocation result.
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Value allocValue = allocateResultEffects[0].getValue();
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// Find the associated dealloc value and register the allocation entry.
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llvm::Optional<Operation *> dealloc = findDealloc(allocValue);
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// If the allocation has > 1 dealloc associated with it, skip handling it.
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if (!dealloc.hasValue())
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return;
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allocs.push_back(std::make_tuple(allocValue, *dealloc));
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});
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}
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//===----------------------------------------------------------------------===//
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// BufferPlacementTransformationBase
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//===----------------------------------------------------------------------===//
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/// Constructs a new transformation base using the given root operation.
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BufferPlacementTransformationBase::BufferPlacementTransformationBase(
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Operation *op)
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: aliases(op), allocs(op), liveness(op) {}
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/// Returns true if the given operation represents a loop by testing whether it
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/// implements the `LoopLikeOpInterface` or the `RegionBranchOpInterface`. In
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/// the case of a `RegionBranchOpInterface`, it checks all region-based control-
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/// flow edges for cycles.
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bool BufferPlacementTransformationBase::isLoop(Operation *op) {
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// If the operation implements the `LoopLikeOpInterface` it can be considered
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// a loop.
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if (isa<LoopLikeOpInterface>(op))
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return true;
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// If the operation does not implement the `RegionBranchOpInterface`, it is
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// (currently) not possible to detect a loop.
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RegionBranchOpInterface regionInterface;
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if (!(regionInterface = dyn_cast<RegionBranchOpInterface>(op)))
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return false;
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// Recurses into a region using the current region interface to find potential
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// cycles.
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SmallPtrSet<Region *, 4> visitedRegions;
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std::function<bool(Region *)> recurse = [&](Region *current) {
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if (!current)
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return false;
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// If we have found a back edge, the parent operation induces a loop.
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if (!visitedRegions.insert(current).second)
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return true;
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// Recurses into all region successors.
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SmallVector<RegionSuccessor, 2> successors;
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regionInterface.getSuccessorRegions(current->getRegionNumber(), successors);
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for (RegionSuccessor ®ionEntry : successors)
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if (recurse(regionEntry.getSuccessor()))
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return true;
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return false;
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};
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// Start with all entry regions and test whether they induce a loop.
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SmallVector<RegionSuccessor, 2> successorRegions;
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regionInterface.getSuccessorRegions(/*index=*/llvm::None, successorRegions);
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for (RegionSuccessor ®ionEntry : successorRegions) {
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if (recurse(regionEntry.getSuccessor()))
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return true;
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visitedRegions.clear();
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}
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return false;
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}
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