41d4aa7de6
SymbolRefAttr is fundamentally a base string plus a sequence of nested references. Instead of storing the string data as a copies StringRef, store it as an already-uniqued StringAttr. This makes a lot of things simpler and more efficient because: 1) references to the symbol are already stored as StringAttr's: there is no need to copy the string data into MLIRContext multiple times. 2) This allows pointer comparisons instead of string comparisons (or redundant uniquing) within SymbolTable.cpp. 3) This allows SymbolTable to hold a DenseMap instead of a StringMap (which again copies the string data and slows lookup). This is a moderately invasive patch, so I kept a lot of compatibility APIs around. It would be nice to explore changing getName() to return a StringAttr for example (right now you have to use getNameAttr()), and eliminate things like the StringRef version of getSymbol. Differential Revision: https://reviews.llvm.org/D108899
253 lines
9.3 KiB
C++
253 lines
9.3 KiB
C++
//===- ModuleCombiner.cpp - MLIR SPIR-V Module Combiner ---------*- C++ -*-===//
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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 the SPIR-V module combiner library.
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//
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//===----------------------------------------------------------------------===//
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#include "mlir/Dialect/SPIRV/Linking/ModuleCombiner.h"
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#include "mlir/Dialect/SPIRV/IR/SPIRVAttributes.h"
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#include "mlir/Dialect/SPIRV/IR/SPIRVDialect.h"
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#include "mlir/Dialect/SPIRV/IR/SPIRVOps.h"
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#include "mlir/IR/Attributes.h"
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#include "mlir/IR/Builders.h"
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#include "mlir/IR/SymbolTable.h"
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#include "llvm/ADT/ArrayRef.h"
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#include "llvm/ADT/Hashing.h"
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#include "llvm/ADT/STLExtras.h"
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#include "llvm/ADT/StringExtras.h"
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#include "llvm/ADT/StringMap.h"
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using namespace mlir;
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static constexpr unsigned maxFreeID = 1 << 20;
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/// Returns an unsed symbol in `module` for `oldSymbolName` by trying numeric
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/// suffix in `lastUsedID`.
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static StringAttr renameSymbol(StringRef oldSymName, unsigned &lastUsedID,
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spirv::ModuleOp module) {
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SmallString<64> newSymName(oldSymName);
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newSymName.push_back('_');
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MLIRContext *ctx = module->getContext();
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while (lastUsedID < maxFreeID) {
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auto possible = StringAttr::get(ctx, newSymName + Twine(++lastUsedID));
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if (!SymbolTable::lookupSymbolIn(module, possible))
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return possible;
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}
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return StringAttr::get(ctx, newSymName);
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}
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/// Checks if a symbol with the same name as `op` already exists in `source`.
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/// If so, renames `op` and updates all its references in `target`.
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static LogicalResult updateSymbolAndAllUses(SymbolOpInterface op,
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spirv::ModuleOp target,
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spirv::ModuleOp source,
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unsigned &lastUsedID) {
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if (!SymbolTable::lookupSymbolIn(source, op.getName()))
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return success();
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StringRef oldSymName = op.getName();
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StringAttr newSymName = renameSymbol(oldSymName, lastUsedID, target);
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if (failed(SymbolTable::replaceAllSymbolUses(op, newSymName, target)))
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return op.emitError("unable to update all symbol uses for ")
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<< oldSymName << " to " << newSymName;
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SymbolTable::setSymbolName(op, newSymName);
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return success();
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}
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/// Computes a hash code to represent `symbolOp` based on all its attributes
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/// except for the symbol name.
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///
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/// Note: We use the operation's name (not the symbol name) as part of the hash
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/// computation. This prevents, for example, mistakenly considering a global
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/// variable and a spec constant as duplicates because their descriptor set +
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/// binding and spec_id, respectively, happen to hash to the same value.
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static llvm::hash_code computeHash(SymbolOpInterface symbolOp) {
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auto range =
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llvm::make_filter_range(symbolOp->getAttrs(), [](NamedAttribute attr) {
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return attr.first != SymbolTable::getSymbolAttrName();
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});
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return llvm::hash_combine(
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symbolOp->getName(),
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llvm::hash_combine_range(range.begin(), range.end()));
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}
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namespace mlir {
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namespace spirv {
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OwningOpRef<spirv::ModuleOp> combine(ArrayRef<spirv::ModuleOp> inputModules,
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OpBuilder &combinedModuleBuilder,
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SymbolRenameListener symRenameListener) {
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if (inputModules.empty())
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return nullptr;
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spirv::ModuleOp firstModule = inputModules.front();
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auto addressingModel = firstModule.addressing_model();
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auto memoryModel = firstModule.memory_model();
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auto vceTriple = firstModule.vce_triple();
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// First check whether there are conflicts between addressing/memory model.
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// Return early if so.
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for (auto module : inputModules) {
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if (module.addressing_model() != addressingModel ||
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module.memory_model() != memoryModel ||
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module.vce_triple() != vceTriple) {
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module.emitError("input modules differ in addressing model, memory "
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"model, and/or VCE triple");
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return nullptr;
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}
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}
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auto combinedModule = combinedModuleBuilder.create<spirv::ModuleOp>(
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firstModule.getLoc(), addressingModel, memoryModel, vceTriple);
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combinedModuleBuilder.setInsertionPointToStart(combinedModule.getBody());
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// In some cases, a symbol in the (current state of the) combined module is
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// renamed in order to enable the conflicting symbol in the input module
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// being merged. For example, if the conflict is between a global variable in
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// the current combined module and a function in the input module, the global
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// variable is renamed. In order to notify listeners of the symbol updates in
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// such cases, we need to keep track of the module from which the renamed
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// symbol in the combined module originated. This map keeps such information.
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llvm::StringMap<spirv::ModuleOp> symNameToModuleMap;
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unsigned lastUsedID = 0;
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for (auto inputModule : inputModules) {
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spirv::ModuleOp moduleClone = inputModule.clone();
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// In the combined module, rename all symbols that conflict with symbols
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// from the current input module. This renaming applies to all ops except
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// for spv.funcs. This way, if the conflicting op in the input module is
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// non-spv.func, we rename that symbol instead and maintain the spv.func in
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// the combined module name as it is.
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for (auto &op : *combinedModule.getBody()) {
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auto symbolOp = dyn_cast<SymbolOpInterface>(op);
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if (!symbolOp)
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continue;
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StringRef oldSymName = symbolOp.getName();
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if (!isa<FuncOp>(op) &&
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failed(updateSymbolAndAllUses(symbolOp, combinedModule, moduleClone,
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lastUsedID)))
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return nullptr;
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StringRef newSymName = symbolOp.getName();
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if (symRenameListener && oldSymName != newSymName) {
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spirv::ModuleOp originalModule = symNameToModuleMap.lookup(oldSymName);
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if (!originalModule) {
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inputModule.emitError(
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"unable to find original spirv::ModuleOp for symbol ")
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<< oldSymName;
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return nullptr;
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}
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symRenameListener(originalModule, oldSymName, newSymName);
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// Since the symbol name is updated, there is no need to maintain the
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// entry that associates the old symbol name with the original module.
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symNameToModuleMap.erase(oldSymName);
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// Instead, add a new entry to map the new symbol name to the original
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// module in case it gets renamed again later.
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symNameToModuleMap[newSymName] = originalModule;
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}
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}
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// In the current input module, rename all symbols that conflict with
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// symbols from the combined module. This includes renaming spv.funcs.
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for (auto &op : *moduleClone.getBody()) {
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auto symbolOp = dyn_cast<SymbolOpInterface>(op);
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if (!symbolOp)
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continue;
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StringRef oldSymName = symbolOp.getName();
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if (failed(updateSymbolAndAllUses(symbolOp, moduleClone, combinedModule,
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lastUsedID)))
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return nullptr;
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StringRef newSymName = symbolOp.getName();
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if (symRenameListener) {
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if (oldSymName != newSymName)
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symRenameListener(inputModule, oldSymName, newSymName);
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// Insert the module associated with the symbol name.
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auto emplaceResult =
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symNameToModuleMap.try_emplace(newSymName, inputModule);
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// If an entry with the same symbol name is already present, this must
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// be a problem with the implementation, specially clean-up of the map
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// while iterating over the combined module above.
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if (!emplaceResult.second) {
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inputModule.emitError("did not expect to find an entry for symbol ")
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<< symbolOp.getName();
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return nullptr;
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}
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}
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}
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// Clone all the module's ops to the combined module.
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for (auto &op : *moduleClone.getBody())
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combinedModuleBuilder.insert(op.clone());
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}
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// Deduplicate identical global variables, spec constants, and functions.
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DenseMap<llvm::hash_code, SymbolOpInterface> hashToSymbolOp;
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SmallVector<SymbolOpInterface, 0> eraseList;
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for (auto &op : *combinedModule.getBody()) {
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SymbolOpInterface symbolOp = dyn_cast<SymbolOpInterface>(op);
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if (!symbolOp)
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continue;
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// Do not support ops with operands or results.
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// Global variables, spec constants, and functions won't have
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// operands/results, but just for safety here.
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if (op.getNumOperands() != 0 || op.getNumResults() != 0)
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continue;
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// Deduplicating functions are not supported yet.
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if (isa<FuncOp>(op))
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continue;
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auto result = hashToSymbolOp.try_emplace(computeHash(symbolOp), symbolOp);
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if (result.second)
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continue;
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SymbolOpInterface replacementSymOp = result.first->second;
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if (failed(SymbolTable::replaceAllSymbolUses(
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symbolOp, replacementSymOp.getNameAttr(), combinedModule))) {
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symbolOp.emitError("unable to update all symbol uses for ")
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<< symbolOp.getName() << " to " << replacementSymOp.getName();
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return nullptr;
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}
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eraseList.push_back(symbolOp);
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}
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for (auto symbolOp : eraseList)
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symbolOp.erase();
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return combinedModule;
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}
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} // namespace spirv
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} // namespace mlir
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