OneShotModuleBufferize.cpp | Explore in Territory

//===- ModuleBufferization.cpp - Bufferization across Func. Boundaries ----===//
//
// 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
//
//===----------------------------------------------------------------------===//
//
// Module Bufferization is an extension of One-Shot Bufferize that
// bufferizes function boundaries. It provides `BufferizableOpInterface`
// implementations for FuncOp, CallOp and ReturnOp.
//
// Module Bufferization is run via `runOneShotModuleBufferize(ModuleOp, ...)`.
// This function analyzes the given module and determines the order of analysis
// and bufferization: Functions that are called are processed before their
// respective callers.
//
// After analyzing a FuncOp, additional information about its bbArgs is
// gathered and stored in `FuncAnalysisState`.
//
// * `aliasingFuncOpBBArgsAnalysis` determines the equivalent/aliasing bbArgs
// for
//   each tensor return value (if any).
// * `funcOpBbArgReadWriteAnalysis` determines whether or not a tensor bbArg is
//   read/written.
//
// Module Bufferization implements the following calling convention.
//
// * In the absence of conflicts within a FuncOp, the FuncOp's bbArgs may always
//   be written to in-place.
// * If a tensor operand of a CallOp is read after the CallOp, the operand of
//   the CallOp must bufferize out-of-place.
//
// Example: The tensor.insert op bufferizes in-place because it is allowed to
// modify the buffer of `%t1` directly. The CallOp in `caller` must bufferize
// out-of-place because `%t0` is modified by the callee but read by the
// tensor.extract op. The analysis of CallOps decides whether an OpOperand must
// bufferize out-of-place based on results of `funcOpBbArgReadWriteAnalysis`.
// ```
// func @callee(%t1 : tensor<?xf32>) -> tensor<?xf32> {
//   %f = ... : f32
//   %0 = tensor.insert %f into %t1[...] : tensor<?xf32>
//   return %0 : tensor<?xf32>
// }
//
// func @caller() -> () {
//   %t0 = ... : tensor<?xf32>
//   %1 = call @callee(%t0) : (tensor<?xf32>) -> (tensor<?xf32>)
//   %2 = tensor.extract %1[...]  : tensor<?xf32>
// }
// ```
//
// Note: If a function is external, `funcOpBbArgReadWriteAnalysis` cannot
// analyze the function body. In such a case, the CallOp analysis conservatively
// assumes that each tensor OpOperand is both read and written.
//
// TODO: Add FuncOp attributes so that bbArgs of external FuncOps can be marked
// as "not reading" and/or "not writing".

#include "mlir/Dialect/Bufferization/Transforms/OneShotModuleBufferize.h"

#include "mlir/Dialect/Bufferization/IR/BufferizableOpInterface.h"
#include "mlir/Dialect/Bufferization/IR/Bufferization.h"
#include "mlir/Dialect/Bufferization/Transforms/Bufferize.h"
#include "mlir/Dialect/Bufferization/Transforms/FuncBufferizableOpInterfaceImpl.h"
#include "mlir/Dialect/Bufferization/Transforms/OneShotAnalysis.h"
#include "mlir/Dialect/Bufferization/Transforms/Transforms.h"
#include "mlir/Dialect/Func/IR/FuncOps.h"
#include "mlir/Dialect/MemRef/IR/MemRef.h"
#include "mlir/IR/BuiltinTypes.h"
#include "mlir/IR/Operation.h"

usingnamespacemlir;
usingnamespacemlir::bufferization;
usingnamespacemlir::bufferization::func_ext;

/// A mapping of FuncOps to their callers.
FuncCallerMap;

/// Get or create FuncAnalysisState.
static FuncAnalysisState &
getOrCreateFuncAnalysisState(OneShotAnalysisState &state) { … }

/// Return the unique ReturnOp that terminates `funcOp`.
/// Return nullptr if there is no such unique ReturnOp.
static Operation *getAssumedUniqueReturnOp(FunctionOpInterface funcOp) { … }

namespace {

/// Annotate IR with the results of the analysis. For testing purposes only.
static void annotateEquivalentReturnBbArg(OpOperand &returnVal,
                                          BlockArgument bbArg) { … }

/// Store function BlockArguments that are equivalent to/aliasing a returned
/// value in FuncAnalysisState.
static LogicalResult
aliasingFuncOpBBArgsAnalysis(FunctionOpInterface funcOp,
                             OneShotAnalysisState &state,
                             FuncAnalysisState &funcState) { … }

static void annotateFuncArgAccess(FunctionOpInterface funcOp, int64_t idx,
                                  bool isRead, bool isWritten) { … }

/// Determine which FuncOp bbArgs are read and which are written. When run on a
/// function with unknown ops, we conservatively assume that such ops bufferize
/// to a read + write.
static LogicalResult
funcOpBbArgReadWriteAnalysis(FunctionOpInterface funcOp,
                             OneShotAnalysisState &state,
                             FuncAnalysisState &funcState) { … }
} // namespace

/// Remove bufferization attributes on FuncOp arguments.
static void removeBufferizationAttributes(BlockArgument bbArg) { … }

static FunctionOpInterface getCalledFunction(CallOpInterface callOp) { … }

/// Gather equivalence info of CallOps.
/// Note: This only adds new equivalence info if the called function was already
/// analyzed.
// TODO: This does not handle cyclic function call graphs etc.
static void equivalenceAnalysis(FunctionOpInterface funcOp,
                                OneShotAnalysisState &state,
                                FuncAnalysisState &funcState) { … }

/// Return "true" if the given function signature has tensor semantics.
static bool hasTensorSignature(FunctionOpInterface funcOp) { … }

/// Store all functions of the `moduleOp` in `orderedFuncOps`, sorted by
/// callee-caller order (i.e. callees without callers first).
/// Store the map of FuncOp to all its callers in `callerMap`.
/// Return `failure()` if a cycle of calls is detected or if we are unable to
/// retrieve the called FuncOp from any func::CallOp.
static LogicalResult
getFuncOpsOrderedByCalls(ModuleOp moduleOp,
                         SmallVectorImpl<FunctionOpInterface> &orderedFuncOps,
                         FuncCallerMap &callerMap) { … }

/// Fold return values that are memref casts and update function return types.
///
/// During FuncOp bufferization, the exact type of the returned memrefs (if any)
/// is not known yet. Therefore, the bufferization uses memref types with the
/// most generic layout map as function return types. After bufferizing the
/// entire function body, a more concise memref type can potentially be used for
/// the return type of the function.
static void foldMemRefCasts(FunctionOpInterface funcOp) { … }

LogicalResult
mlir::bufferization::analyzeModuleOp(ModuleOp moduleOp,
                                     OneShotAnalysisState &state,
                                     BufferizationStatistics *statistics) { … }

void mlir::bufferization::removeBufferizationAttributesInModule(
    ModuleOp moduleOp) { … }

LogicalResult mlir::bufferization::bufferizeModuleOp(
    ModuleOp moduleOp, const OneShotBufferizationOptions &options,
    BufferizationStatistics *statistics) { … }

LogicalResult mlir::bufferization::runOneShotModuleBufferize(
    ModuleOp moduleOp, const OneShotBufferizationOptions &options,
    BufferizationStatistics *statistics) { … }
llvm/mlir/lib/Dialect/Bufferization/Transforms/OneShotModuleBufferize.cpp
