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//===- BufferUtils.cpp - buffer transformation utilities ------------------===//
//
// 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 file implements utilities for buffer optimization passes.
//
//===----------------------------------------------------------------------===//
#include "mlir/Dialect/Bufferization/Transforms/BufferUtils.h"
#include "mlir/Dialect/Bufferization/IR/BufferizableOpInterface.h"
#include "mlir/Dialect/Bufferization/Transforms/Bufferize.h"
#include "mlir/Dialect/MemRef/IR/MemRef.h"
#include "mlir/Dialect/MemRef/Utils/MemRefUtils.h"
#include "mlir/IR/Operation.h"
#include <optional>
using namespace mlir;
using namespace mlir::bufferization;
//===----------------------------------------------------------------------===//
// BufferPlacementAllocs
//===----------------------------------------------------------------------===//
/// Get the start operation to place the given alloc value withing the
// specified placement block.
Operation *BufferPlacementAllocs::getStartOperation(Value allocValue,
Block *placementBlock,
const Liveness &liveness) {
// We have to ensure that we place the alloc before its first use in this
// block.
const LivenessBlockInfo &livenessInfo = *liveness.getLiveness(placementBlock);
Operation *startOperation = livenessInfo.getStartOperation(allocValue);
// Check whether the start operation lies in the desired placement block.
// If not, we will use the terminator as this is the last operation in
// this block.
if (startOperation->getBlock() != placementBlock) {
Operation *opInPlacementBlock =
placementBlock->findAncestorOpInBlock(*startOperation);
startOperation = opInPlacementBlock ? opInPlacementBlock
: placementBlock->getTerminator();
}
return startOperation;
}
/// Initializes the internal list by discovering all supported allocation
/// nodes.
BufferPlacementAllocs::BufferPlacementAllocs(Operation *op) { build(op); }
/// Searches for and registers all supported allocation entries.
void BufferPlacementAllocs::build(Operation *op) {
op->walk([&](MemoryEffectOpInterface opInterface) {
// Try to find a single allocation result.
SmallVector<MemoryEffects::EffectInstance, 2> effects;
opInterface.getEffects(effects);
SmallVector<MemoryEffects::EffectInstance, 2> allocateResultEffects;
llvm::copy_if(
effects, std::back_inserter(allocateResultEffects),
[=](MemoryEffects::EffectInstance &it) {
Value value = it.getValue();
return isa<MemoryEffects::Allocate>(it.getEffect()) && value &&
isa<OpResult>(value) &&
it.getResource() !=
SideEffects::AutomaticAllocationScopeResource::get();
});
// If there is one result only, we will be able to move the allocation and
// (possibly existing) deallocation ops.
if (allocateResultEffects.size() != 1)
return;
// Get allocation result.
Value allocValue = allocateResultEffects[0].getValue();
// Find the associated dealloc value and register the allocation entry.
std::optional<Operation *> dealloc = memref::findDealloc(allocValue);
// If the allocation has > 1 dealloc associated with it, skip handling it.
if (!dealloc)
return;
allocs.push_back(std::make_tuple(allocValue, *dealloc));
});
}
//===----------------------------------------------------------------------===//
// BufferPlacementTransformationBase
//===----------------------------------------------------------------------===//
/// Constructs a new transformation base using the given root operation.
BufferPlacementTransformationBase::BufferPlacementTransformationBase(
Operation *op)
: aliases(op), allocs(op), liveness(op) {}
//===----------------------------------------------------------------------===//
// BufferPlacementTransformationBase
//===----------------------------------------------------------------------===//
FailureOr<memref::GlobalOp>
bufferization::getGlobalFor(arith::ConstantOp constantOp,
SymbolTableCollection &symbolTables,
uint64_t alignment, Attribute memorySpace) {
auto type = cast<RankedTensorType>(constantOp.getType());
auto moduleOp = constantOp->getParentOfType<ModuleOp>();
if (!moduleOp)
return failure();
// If we already have a global for this constant value, no need to do
// anything else.
for (Operation &op : moduleOp.getRegion().getOps()) {
auto globalOp = dyn_cast<memref::GlobalOp>(&op);
if (!globalOp)
continue;
if (!globalOp.getInitialValue().has_value())
continue;
uint64_t opAlignment = globalOp.getAlignment().value_or(0);
Attribute initialValue = globalOp.getInitialValue().value();
if (opAlignment == alignment && initialValue == constantOp.getValue())
return globalOp;
}
// Create a builder without an insertion point. We will insert using the
// symbol table to guarantee unique names.
OpBuilder globalBuilder(moduleOp.getContext());
SymbolTable &symbolTable = symbolTables.getSymbolTable(moduleOp);
// Create a pretty name.
SmallString<64> buf;
llvm::raw_svector_ostream os(buf);
interleave(type.getShape(), os, "x");
os << "x" << type.getElementType();
// Add an optional alignment to the global memref.
IntegerAttr memrefAlignment =
alignment > 0 ? IntegerAttr::get(globalBuilder.getI64Type(), alignment)
: IntegerAttr();
// Memref globals always have an identity layout.
auto memrefType =
cast<MemRefType>(getMemRefTypeWithStaticIdentityLayout(type));
if (memorySpace)
memrefType = MemRefType::Builder(memrefType).setMemorySpace(memorySpace);
auto global = memref::GlobalOp::create(
globalBuilder, constantOp.getLoc(),
(Twine("__constant_") + os.str()).str(),
/*sym_visibility=*/globalBuilder.getStringAttr("private"),
/*type=*/memrefType,
/*initial_value=*/cast<ElementsAttr>(constantOp.getValue()),
/*constant=*/true,
/*alignment=*/memrefAlignment);
symbolTable.insert(global);
// The symbol table inserts at the end of the module, but globals are a bit
// nicer if they are at the beginning.
global->moveBefore(&moduleOp.front());
return global;
}
namespace mlir::bufferization {
void removeSymbol(Operation *op, BufferizationState &state) {
SymbolTable &symbolTable = state.getSymbolTables().getSymbolTable(
op->getParentWithTrait<OpTrait::SymbolTable>());
symbolTable.remove(op);
}
void insertSymbol(Operation *op, BufferizationState &state) {
SymbolTable &symbolTable = state.getSymbolTables().getSymbolTable(
op->getParentWithTrait<OpTrait::SymbolTable>());
symbolTable.insert(op);
}
} // namespace mlir::bufferization
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