[Mlir-commits] [mlir] [MLIR] Cyclic AttrType Replacer (PR #98206)
Billy Zhu
llvmlistbot at llvm.org
Thu Jul 11 22:14:19 PDT 2024
https://github.com/zyx-billy updated https://github.com/llvm/llvm-project/pull/98206
>From bcc3edaa9b80c1ee3e87ad15894382a065bef9ad Mon Sep 17 00:00:00 2001
From: Billy Zhu <billyzhu at modular.com>
Date: Tue, 9 Jul 2024 10:26:05 -0700
Subject: [PATCH 1/5] add replacer cache and gtests
---
.../mlir/Support/CyclicReplacerCache.h | 277 ++++++++++
mlir/unittests/Support/CMakeLists.txt | 1 +
.../Support/CyclicReplacerCacheTest.cpp | 472 ++++++++++++++++++
3 files changed, 750 insertions(+)
create mode 100644 mlir/include/mlir/Support/CyclicReplacerCache.h
create mode 100644 mlir/unittests/Support/CyclicReplacerCacheTest.cpp
diff --git a/mlir/include/mlir/Support/CyclicReplacerCache.h b/mlir/include/mlir/Support/CyclicReplacerCache.h
new file mode 100644
index 0000000000000..9a703676fff11
--- /dev/null
+++ b/mlir/include/mlir/Support/CyclicReplacerCache.h
@@ -0,0 +1,277 @@
+//===- CyclicReplacerCache.h ------------------------------------*- 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 file contains helper classes for caching replacer-like functions that
+// map values between two domains. They are able to handle replacer logic that
+// contains self-recursion.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef MLIR_SUPPORT_CACHINGREPLACER_H
+#define MLIR_SUPPORT_CACHINGREPLACER_H
+
+#include "mlir/IR/Visitors.h"
+#include "llvm/ADT/DenseSet.h"
+#include "llvm/ADT/MapVector.h"
+#include <set>
+
+namespace mlir {
+
+//===----------------------------------------------------------------------===//
+// CyclicReplacerCache
+//===----------------------------------------------------------------------===//
+
+/// A cache for replacer-like functions that map values between two domains. The
+/// difference compared to just using a map to cache in-out pairs is that this
+/// class is able to handle replacer logic that is self-recursive (and thus may
+/// cause infinite recursion in the naive case).
+///
+/// This class provides a hook for the user to perform cycle pruning when a
+/// cycle is identified, and is able to perform context-sensitive caching so
+/// that the replacement result for an input that is part of a pruned cycle can
+/// be distinct from the replacement result for the same input when it is not
+/// part of a cycle.
+///
+/// In addition, this class allows deferring cycle pruning until specific inputs
+/// are repeated. This is useful for cases where not all elements in a cycle can
+/// perform pruning. The user still must guarantee that at least one element in
+/// any given cycle can perform pruning. Even if not, an assertion will
+/// eventually be tripped instead of infinite recursion (the run-time is
+/// linearly bounded by the maximum cycle length of its input).
+template <typename InT, typename OutT>
+class CyclicReplacerCache {
+public:
+ /// User-provided replacement function & cycle-breaking functions.
+ /// The cycle-breaking function must not make any more recursive invocations
+ /// to this cached replacer.
+ using CycleBreakerFn = std::function<std::optional<OutT>(const InT &)>;
+
+ CyclicReplacerCache() = delete;
+ CyclicReplacerCache(CycleBreakerFn cycleBreaker)
+ : cycleBreaker(std::move(cycleBreaker)) {}
+
+ /// A possibly unresolved cache entry.
+ /// If unresolved, the entry must be resolved before it goes out of scope.
+ struct CacheEntry {
+ public:
+ ~CacheEntry() { assert(result && "unresovled cache entry"); }
+
+ /// Check whether this node was repeated during recursive replacements.
+ /// This only makes sense to be called after all recursive replacements are
+ /// completed and the current element has resurfaced to the top of the
+ /// replacement stack.
+ bool wasRepeated() const {
+ // If the top frame includes itself as a dependency, then it must have
+ // been repeated.
+ ReplacementFrame &currFrame = cache.replacementStack.back();
+ size_t currFrameIndex = cache.replacementStack.size() - 1;
+ return currFrame.dependentFrames.count(currFrameIndex);
+ }
+
+ /// Resolve an unresolved cache entry by providing the result to be stored
+ /// in the cache.
+ void resolve(OutT result) {
+ assert(!this->result && "cache entry already resolved");
+ this->result = result;
+ cache.finalizeReplacement(element, result);
+ }
+
+ /// Get the resolved result if one exists.
+ std::optional<OutT> get() { return result; }
+
+ private:
+ friend class CyclicReplacerCache;
+ CacheEntry() = delete;
+ CacheEntry(CyclicReplacerCache<InT, OutT> &cache, InT element,
+ std::optional<OutT> result = std::nullopt)
+ : cache(cache), element(element), result(result) {}
+
+ CyclicReplacerCache<InT, OutT> &cache;
+ InT element;
+ std::optional<OutT> result;
+ };
+
+ /// Lookup the cache for a pre-calculated replacement for `element`.
+ /// If one exists, a resolved CacheEntry will be returned. Otherwise, an
+ /// unresolved CacheEntry will be returned, and the caller must resolve it
+ /// with the calculated replacement so it can be registered in the cache for
+ /// future use.
+ /// Multiple unresolved CacheEntries may be retrieved. However, any unresolved
+ /// CacheEntries that are returned must be resolved in reverse order of
+ /// retrieval, i.e. the last retrieved CacheEntry must be resolved first, and
+ /// the first retrieved CacheEntry must be resolved last. This should be
+ /// natural when used as a stack / inside recursion.
+ CacheEntry lookupOrInit(const InT &element);
+
+private:
+ /// Register the replacement in the cache and update the replacementStack.
+ void finalizeReplacement(const InT &element, const OutT &result);
+
+ CycleBreakerFn cycleBreaker;
+ DenseMap<InT, OutT> standaloneCache;
+
+ struct DependentReplacement {
+ OutT replacement;
+ /// The highest replacement frame index that this cache entry is dependent
+ /// on.
+ size_t highestDependentFrame;
+ };
+ DenseMap<InT, DependentReplacement> dependentCache;
+
+ struct ReplacementFrame {
+ /// The set of elements that is only legal while under this current frame.
+ /// They need to be removed from the cache when this frame is popped off the
+ /// replacement stack.
+ DenseSet<InT> dependingReplacements;
+ /// The set of frame indices that this current frame's replacement is
+ /// dependent on, ordered from highest to lowest.
+ std::set<size_t, std::greater<size_t>> dependentFrames;
+ };
+ /// Every element currently in the progress of being replaced pushes a frame
+ /// onto this stack.
+ SmallVector<ReplacementFrame> replacementStack;
+ /// Maps from each input element to its indices on the replacement stack.
+ DenseMap<InT, SmallVector<size_t, 2>> cyclicElementFrame;
+ /// If set to true, we are currently asking an element to break a cycle. No
+ /// more recursive invocations is allowed while this is true (the replacement
+ /// stack can no longer grow).
+ bool resolvingCycle = false;
+};
+
+template <typename InT, typename OutT>
+typename CyclicReplacerCache<InT, OutT>::CacheEntry
+CyclicReplacerCache<InT, OutT>::lookupOrInit(const InT &element) {
+ assert(!resolvingCycle &&
+ "illegal recursive invocation while breaking cycle");
+
+ if (auto it = standaloneCache.find(element); it != standaloneCache.end())
+ return CacheEntry(*this, element, it->second);
+
+ if (auto it = dependentCache.find(element); it != dependentCache.end()) {
+ // pdate the current top frame (the element that invoked this current
+ // replacement) to include any dependencies the cache entry had.
+ ReplacementFrame &currFrame = replacementStack.back();
+ currFrame.dependentFrames.insert(it->second.highestDependentFrame);
+ return CacheEntry(*this, element, it->second.replacement);
+ }
+
+ auto [it, inserted] = cyclicElementFrame.try_emplace(element);
+ if (!inserted) {
+ // This is a repeat of a known element. Try to break cycle here.
+ resolvingCycle = true;
+ std::optional<OutT> result = cycleBreaker(element);
+ resolvingCycle = false;
+ if (result) {
+ // Cycle was broken.
+ size_t dependentFrame = it->second.back();
+ dependentCache[element] = {*result, dependentFrame};
+ ReplacementFrame &currFrame = replacementStack.back();
+ // If this is a repeat, there is no replacement frame to pop. Mark the top
+ // frame as being dependent on this element.
+ currFrame.dependentFrames.insert(dependentFrame);
+
+ return CacheEntry(*this, element, *result);
+ }
+
+ // Cycle could not be broken.
+ // A legal setup must ensure at least one element of each cycle can break
+ // cycles. Under this setup, each element can be seen at most twice before
+ // the cycle is broken. If we see an element more than twice, we know this
+ // is an illegal setup.
+ assert(it->second.size() <= 2 && "illegal 3rd repeat of input");
+ }
+
+ // Otherwise, either this is the first time we see this element, or this
+ // element could not break this cycle.
+ it->second.push_back(replacementStack.size());
+ replacementStack.emplace_back();
+
+ return CacheEntry(*this, element);
+}
+
+template <typename InT, typename OutT>
+void CyclicReplacerCache<InT, OutT>::finalizeReplacement(const InT &element,
+ const OutT &result) {
+ ReplacementFrame &currFrame = replacementStack.back();
+ // With the conclusion of this replacement frame, the current element is no
+ // longer a dependent element.
+ currFrame.dependentFrames.erase(replacementStack.size() - 1);
+
+ auto prevLayerIter = ++replacementStack.rbegin();
+ if (prevLayerIter == replacementStack.rend()) {
+ // If this is the last frame, there should be zero dependents.
+ assert(currFrame.dependentFrames.empty() &&
+ "internal error: top-level dependent replacement");
+ // Cache standalone result.
+ standaloneCache[element] = result;
+ } else if (currFrame.dependentFrames.empty()) {
+ // Cache standalone result.
+ standaloneCache[element] = result;
+ } else {
+ // Cache dependent result.
+ size_t highestDependentFrame = *currFrame.dependentFrames.begin();
+ dependentCache[element] = {result, highestDependentFrame};
+
+ // Otherwise, the previous frame inherits the same dependent frames.
+ prevLayerIter->dependentFrames.insert(currFrame.dependentFrames.begin(),
+ currFrame.dependentFrames.end());
+
+ // Mark this current replacement as a depending replacement on the closest
+ // dependent frame.
+ replacementStack[highestDependentFrame].dependingReplacements.insert(
+ element);
+ }
+
+ // All depending replacements in the cache must be purged.
+ for (InT key : currFrame.dependingReplacements)
+ dependentCache.erase(key);
+
+ replacementStack.pop_back();
+ auto it = cyclicElementFrame.find(element);
+ it->second.pop_back();
+ if (it->second.empty())
+ cyclicElementFrame.erase(it);
+}
+
+//===----------------------------------------------------------------------===//
+// CachedCyclicReplacer
+//===----------------------------------------------------------------------===//
+
+/// A helper class for cases where the input/output types of the replacer
+/// function is identical to the types stored in the cache. This class wraps
+/// the user-provided replacer function, and can be used in place of the user
+/// function.
+template <typename InT, typename OutT>
+class CachedCyclicReplacer {
+public:
+ using ReplacerFn = std::function<OutT(const InT &)>;
+ using CycleBreakerFn =
+ typename CyclicReplacerCache<InT, OutT>::CycleBreakerFn;
+
+ CachedCyclicReplacer() = delete;
+ CachedCyclicReplacer(ReplacerFn replacer, CycleBreakerFn cycleBreaker)
+ : replacer(std::move(replacer)), cache(std::move(cycleBreaker)) {}
+
+ OutT operator()(const InT &element) {
+ auto cacheEntry = cache.lookupOrInit(element);
+ if (std::optional<OutT> result = cacheEntry.get())
+ return *result;
+
+ OutT result = replacer(element);
+ cacheEntry.resolve(result);
+ return result;
+ }
+
+private:
+ ReplacerFn replacer;
+ CyclicReplacerCache<InT, OutT> cache;
+};
+
+} // namespace mlir
+
+#endif // MLIR_SUPPORT_CACHINGREPLACER_H
diff --git a/mlir/unittests/Support/CMakeLists.txt b/mlir/unittests/Support/CMakeLists.txt
index 1dbf072bcbbfd..ec79a1c640909 100644
--- a/mlir/unittests/Support/CMakeLists.txt
+++ b/mlir/unittests/Support/CMakeLists.txt
@@ -1,4 +1,5 @@
add_mlir_unittest(MLIRSupportTests
+ CyclicReplacerCacheTest.cpp
IndentedOstreamTest.cpp
StorageUniquerTest.cpp
)
diff --git a/mlir/unittests/Support/CyclicReplacerCacheTest.cpp b/mlir/unittests/Support/CyclicReplacerCacheTest.cpp
new file mode 100644
index 0000000000000..23748e29765cb
--- /dev/null
+++ b/mlir/unittests/Support/CyclicReplacerCacheTest.cpp
@@ -0,0 +1,472 @@
+//===- CyclicReplacerCacheTest.cpp ----------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#include "mlir/Support/CyclicReplacerCache.h"
+#include "llvm/ADT/SetVector.h"
+#include "gmock/gmock.h"
+#include <map>
+#include <set>
+
+using namespace mlir;
+
+TEST(CachedCyclicReplacerTest, testNoRecursion) {
+ CachedCyclicReplacer<int, bool> replacer(
+ /*replacer=*/[](int n) { return static_cast<bool>(n); },
+ /*cycleBreaker=*/[](int n) { return std::nullopt; });
+
+ EXPECT_EQ(replacer(3), true);
+ EXPECT_EQ(replacer(0), false);
+}
+
+TEST(CachedCyclicReplacerTest, testInPlaceRecursionPruneAnywhere) {
+ // Replacer cycles through ints 0 -> 1 -> 2 -> 0 -> ...
+ CachedCyclicReplacer<int, int> replacer(
+ /*replacer=*/[&](int n) { return replacer((n + 1) % 3); },
+ /*cycleBreaker=*/[&](int n) { return -1; });
+
+ // Starting at 0.
+ EXPECT_EQ(replacer(0), -1);
+ // Starting at 2.
+ EXPECT_EQ(replacer(2), -1);
+}
+
+//===----------------------------------------------------------------------===//
+// CachedCyclicReplacer: ChainRecursion
+//===----------------------------------------------------------------------===//
+
+/// This set of tests uses a replacer function that maps ints into vectors of
+/// ints.
+///
+/// The replacement result for input `n` is the replacement result of `(n+1)%3`
+/// appended with an element `42`. Theoretically, this will produce an
+/// infinitely long vector. The cycle-breaker function prunes this infinite
+/// recursion in the replacer logic by returning an empty vector upon the first
+/// re-occurrence of an input value.
+class CachedCyclicReplacerChainRecursionPruningTest : public ::testing::Test {
+public:
+ // N ==> (N+1) % 3
+ // This will create a chain of infinite length without recursion pruning.
+ CachedCyclicReplacerChainRecursionPruningTest()
+ : replacer(
+ [&](int n) {
+ ++invokeCount;
+ std::vector<int> result = replacer((n + 1) % 3);
+ result.push_back(42);
+ return result;
+ },
+ [&](int n) -> std::optional<std::vector<int>> {
+ return baseCase.value_or(n) == n
+ ? std::make_optional(std::vector<int>{})
+ : std::nullopt;
+ }) {}
+
+ std::vector<int> getChain(unsigned N) { return std::vector<int>(N, 42); };
+
+ CachedCyclicReplacer<int, std::vector<int>> replacer;
+ int invokeCount = 0;
+ std::optional<int> baseCase = std::nullopt;
+};
+
+TEST_F(CachedCyclicReplacerChainRecursionPruningTest, testPruneAnywhere0) {
+ // Starting at 0. Cycle length is 3.
+ EXPECT_EQ(replacer(0), getChain(3));
+ EXPECT_EQ(invokeCount, 3);
+
+ // Starting at 1. Cycle length is 5 now because of a cached replacement at 0.
+ invokeCount = 0;
+ EXPECT_EQ(replacer(1), getChain(5));
+ EXPECT_EQ(invokeCount, 2);
+
+ // Starting at 2. Cycle length is 4. Entire result is cached.
+ invokeCount = 0;
+ EXPECT_EQ(replacer(2), getChain(4));
+ EXPECT_EQ(invokeCount, 0);
+}
+
+TEST_F(CachedCyclicReplacerChainRecursionPruningTest, testPruneAnywhere1) {
+ // Starting at 1. Cycle length is 3.
+ EXPECT_EQ(replacer(1), getChain(3));
+ EXPECT_EQ(invokeCount, 3);
+}
+
+TEST_F(CachedCyclicReplacerChainRecursionPruningTest, testPruneSpecific0) {
+ baseCase = 0;
+
+ // Starting at 0. Cycle length is 3.
+ EXPECT_EQ(replacer(0), getChain(3));
+ EXPECT_EQ(invokeCount, 3);
+}
+
+TEST_F(CachedCyclicReplacerChainRecursionPruningTest, testPruneSpecific1) {
+ baseCase = 0;
+
+ // Starting at 1. Cycle length is 5 (1 -> 2 -> 0 -> 1 -> 2 -> Prune).
+ EXPECT_EQ(replacer(1), getChain(5));
+ EXPECT_EQ(invokeCount, 5);
+
+ // Starting at 0. Cycle length is 3. Entire result is cached.
+ invokeCount = 0;
+ EXPECT_EQ(replacer(0), getChain(3));
+ EXPECT_EQ(invokeCount, 0);
+}
+
+//===----------------------------------------------------------------------===//
+// CachedCyclicReplacer: GraphReplacement
+//===----------------------------------------------------------------------===//
+
+/// This set of tests uses a replacer function that maps from cyclic graphs to
+/// trees, pruning out cycles in the process.
+///
+/// It consists of two helper classes:
+/// - Graph
+/// - A directed graph where nodes are non-negative integers.
+/// - PrunedGraph
+/// - A Graph where edges that used to cause cycles are now represented with
+/// an indirection (a recursionId).
+class CachedCyclicReplacerGraphReplacement : public ::testing::Test {
+public:
+ /// A directed graph where nodes are non-negative integers.
+ struct Graph {
+ using Node = int64_t;
+
+ /// Use ordered containers for deterministic output.
+ /// Nodes without outgoing edges are considered nonexistent.
+ std::map<Node, std::set<Node>> edges;
+
+ void addEdge(Node src, Node sink) { edges[src].insert(sink); }
+
+ bool isCyclic() const {
+ DenseSet<Node> visited;
+ for (Node root : llvm::make_first_range(edges)) {
+ if (visited.contains(root))
+ continue;
+
+ SetVector<Node> path;
+ SmallVector<Node> workstack;
+ workstack.push_back(root);
+ while (!workstack.empty()) {
+ Node curr = workstack.back();
+ workstack.pop_back();
+
+ if (curr < 0) {
+ // A negative node signals the end of processing all of this node's
+ // children. Remove self from path.
+ assert(path.back() == -curr && "internal inconsistency");
+ path.pop_back();
+ continue;
+ }
+
+ if (path.contains(curr))
+ return true;
+
+ visited.insert(curr);
+ auto edgesIter = edges.find(curr);
+ if (edgesIter == edges.end() || edgesIter->second.empty())
+ continue;
+
+ path.insert(curr);
+ // Push negative node to signify recursion return.
+ workstack.push_back(-curr);
+ workstack.insert(workstack.end(), edgesIter->second.begin(),
+ edgesIter->second.end());
+ }
+ }
+ return false;
+ }
+
+ /// Deterministic output for testing.
+ std::string serialize() const {
+ std::ostringstream oss;
+ for (const auto &[src, neighbors] : edges) {
+ oss << src << ":";
+ for (Graph::Node neighbor : neighbors)
+ oss << " " << neighbor;
+ oss << "\n";
+ }
+ return oss.str();
+ }
+ };
+
+ /// A Graph where edges that used to cause cycles (back-edges) are now
+ /// represented with an indirection (a recursionId).
+ ///
+ /// In addition to each node being an integer, each node also tracks the
+ /// original integer id it had in the original graph. This way for every
+ /// back-edge, we can represent it as pointing to a new instance of the
+ /// original node. Then we mark the original node and the new instance with
+ /// a new unique recursionId to indicate that they're supposed to be the same
+ /// graph.
+ struct PrunedGraph {
+ using Node = Graph::Node;
+ struct NodeInfo {
+ Graph::Node originalId;
+ // A negative recursive index means not recursive.
+ int64_t recursionId;
+ };
+
+ /// Add a regular non-recursive-self node.
+ Node addNode(Graph::Node originalId, int64_t recursionIndex = -1) {
+ Node id = nextConnectionId++;
+ info[id] = {originalId, recursionIndex};
+ return id;
+ }
+ /// Add a recursive-self-node, i.e. a duplicate of the original node that is
+ /// meant to represent an indirection to it.
+ std::pair<Node, int64_t> addRecursiveSelfNode(Graph::Node originalId) {
+ return {addNode(originalId, nextRecursionId), nextRecursionId++};
+ }
+ void addEdge(Node src, Node sink) { connections.addEdge(src, sink); }
+
+ /// Deterministic output for testing.
+ std::string serialize() const {
+ std::ostringstream oss;
+ oss << "nodes\n";
+ for (const auto &[nodeId, nodeInfo] : info) {
+ oss << nodeId << ": n" << nodeInfo.originalId;
+ if (nodeInfo.recursionId >= 0)
+ oss << '<' << nodeInfo.recursionId << '>';
+ oss << "\n";
+ }
+ oss << "edges\n";
+ oss << connections.serialize();
+ return oss.str();
+ }
+
+ bool isCyclic() const { return connections.isCyclic(); }
+
+ private:
+ Graph connections;
+ int64_t nextRecursionId = 0;
+ int64_t nextConnectionId = 0;
+ // Use ordered map for deterministic output.
+ std::map<Graph::Node, NodeInfo> info;
+ };
+
+ PrunedGraph breakCycles(const Graph &input) {
+ assert(input.isCyclic() && "input graph is not cyclic");
+
+ PrunedGraph output;
+
+ DenseMap<Graph::Node, int64_t> recMap;
+ auto cycleBreaker = [&](Graph::Node inNode) -> std::optional<Graph::Node> {
+ auto [node, recId] = output.addRecursiveSelfNode(inNode);
+ recMap[inNode] = recId;
+ return node;
+ };
+
+ CyclicReplacerCache<Graph::Node, Graph::Node> cache(cycleBreaker);
+
+ std::function<Graph::Node(Graph::Node)> replaceNode =
+ [&](Graph::Node inNode) {
+ auto cacheEntry = cache.lookupOrInit(inNode);
+ if (std::optional<Graph::Node> result = cacheEntry.get())
+ return *result;
+
+ // Recursively replace its neighbors.
+ SmallVector<Graph::Node> neighbors;
+ if (auto it = input.edges.find(inNode); it != input.edges.end())
+ neighbors = SmallVector<Graph::Node>(
+ llvm::map_range(it->second, replaceNode));
+
+ // Create a new node in the output graph.
+ int64_t recursionIndex =
+ cacheEntry.wasRepeated() ? recMap.lookup(inNode) : -1;
+ Graph::Node result = output.addNode(inNode, recursionIndex);
+
+ for (Graph::Node neighbor : neighbors)
+ output.addEdge(result, neighbor);
+
+ cacheEntry.resolve(result);
+ return result;
+ };
+
+ /// Translate starting from each node.
+ for (Graph::Node root : llvm::make_first_range(input.edges))
+ replaceNode(root);
+
+ return output;
+ }
+
+ /// Helper for serialization tests that allow putting comments in the
+ /// serialized format. Every line that begins with a `;` is considered a
+ /// comment. The entire line, incl. the terminating `\n` is removed.
+ std::string trimComments(StringRef input) {
+ std::ostringstream oss;
+ bool isNewLine = false;
+ bool isComment = false;
+ for (char c : input) {
+ // Lines beginning with ';' are comments.
+ if (isNewLine && c == ';')
+ isComment = true;
+
+ if (!isComment)
+ oss << c;
+
+ if (c == '\n') {
+ isNewLine = true;
+ isComment = false;
+ }
+ }
+ return oss.str();
+ }
+};
+
+TEST_F(CachedCyclicReplacerGraphReplacement, testSingleLoop) {
+ // 0 -> 1 -> 2
+ // ^ |
+ // +---------+
+ Graph input = {{{0, {1}}, {1, {2}}, {2, {0}}}};
+ PrunedGraph output = breakCycles(input);
+ ASSERT_FALSE(output.isCyclic()) << output.serialize();
+ EXPECT_EQ(output.serialize(), trimComments(R"(nodes
+; root 0
+0: n0<0>
+1: n2
+2: n1
+3: n0<0>
+; root 1
+4: n2
+; root 2
+5: n1
+edges
+1: 0
+2: 1
+3: 2
+4: 3
+5: 4
+)"));
+}
+
+TEST_F(CachedCyclicReplacerGraphReplacement, testDualLoop) {
+ // +----> 1 -----+
+ // | v
+ // 0 <---------- 3
+ // | ^
+ // +----> 2 -----+
+ //
+ // Two loops:
+ // 0 -> 1 -> 3 -> 0
+ // 0 -> 2 -> 3 -> 0
+ Graph input = {{{0, {1, 2}}, {1, {3}}, {2, {3}}, {3, {0}}}};
+ PrunedGraph output = breakCycles(input);
+ ASSERT_FALSE(output.isCyclic()) << output.serialize();
+ EXPECT_EQ(output.serialize(), trimComments(R"(nodes
+; root 0
+0: n0<0>
+1: n3
+2: n1
+3: n2
+4: n0<0>
+; root 1
+5: n3
+6: n1
+; root 2
+7: n2
+edges
+1: 0
+2: 1
+3: 1
+4: 2 3
+5: 4
+6: 5
+7: 5
+)"));
+}
+
+TEST_F(CachedCyclicReplacerGraphReplacement, testNestedLoops) {
+ // +----> 1 -----+
+ // | ^ v
+ // 0 <----+----- 2
+ //
+ // Two nested loops:
+ // 0 -> 1 -> 2 -> 0
+ // 1 -> 2 -> 1
+ Graph input = {{{0, {1}}, {1, {2}}, {2, {0, 1}}}};
+ PrunedGraph output = breakCycles(input);
+ ASSERT_FALSE(output.isCyclic()) << output.serialize();
+ EXPECT_EQ(output.serialize(), trimComments(R"(nodes
+; root 0
+0: n0<0>
+1: n1<1>
+2: n2
+3: n1<1>
+4: n0<0>
+; root 1
+5: n1<2>
+6: n2
+7: n1<2>
+; root 2
+8: n2
+edges
+2: 0 1
+3: 2
+4: 3
+6: 4 5
+7: 6
+8: 4 7
+)"));
+}
+
+TEST_F(CachedCyclicReplacerGraphReplacement, testDualNestedLoops) {
+ // +----> 1 -----+
+ // | ^ v
+ // 0 <----+----- 3
+ // | v ^
+ // +----> 2 -----+
+ //
+ // Two sets of nested loops:
+ // 0 -> 1 -> 3 -> 0
+ // 1 -> 3 -> 1
+ // 0 -> 2 -> 3 -> 0
+ // 2 -> 3 -> 2
+ Graph input = {{{0, {1, 2}}, {1, {3}}, {2, {3}}, {3, {0, 1, 2}}}};
+ PrunedGraph output = breakCycles(input);
+ ASSERT_FALSE(output.isCyclic()) << output.serialize();
+ EXPECT_EQ(output.serialize(), trimComments(R"(nodes
+; root 0
+0: n0<0>
+1: n1<1>
+2: n3<2>
+3: n2
+4: n3<2>
+5: n1<1>
+6: n2<3>
+7: n3
+8: n2<3>
+9: n0<0>
+; root 1
+10: n1<4>
+11: n3<5>
+12: n2
+13: n3<5>
+14: n1<4>
+; root 2
+15: n2<6>
+16: n3
+17: n2<6>
+; root 3
+18: n3
+edges
+; root 0
+3: 2
+4: 0 1 3
+5: 4
+7: 0 5 6
+8: 7
+9: 5 8
+; root 1
+12: 11
+13: 9 10 12
+14: 13
+; root 2
+16: 9 14 15
+17: 16
+; root 3
+18: 9 14 17
+)"));
+}
>From 8d1dd886c4a80507c8a97dda15e91acbfa7c3619 Mon Sep 17 00:00:00 2001
From: Billy Zhu <billyzhu at modular.com>
Date: Tue, 9 Jul 2024 10:27:13 -0700
Subject: [PATCH 2/5] refactor attrtype replacers & add tests
---
mlir/include/mlir/IR/AttrTypeSubElements.h | 138 ++++++++++--
mlir/lib/IR/AttrTypeSubElements.cpp | 146 ++++++++++---
mlir/unittests/IR/AttrTypeReplacerTest.cpp | 231 +++++++++++++++++++++
mlir/unittests/IR/CMakeLists.txt | 1 +
4 files changed, 467 insertions(+), 49 deletions(-)
create mode 100644 mlir/unittests/IR/AttrTypeReplacerTest.cpp
diff --git a/mlir/include/mlir/IR/AttrTypeSubElements.h b/mlir/include/mlir/IR/AttrTypeSubElements.h
index 3105040b87631..234767deea00a 100644
--- a/mlir/include/mlir/IR/AttrTypeSubElements.h
+++ b/mlir/include/mlir/IR/AttrTypeSubElements.h
@@ -16,6 +16,7 @@
#include "mlir/IR/MLIRContext.h"
#include "mlir/IR/Visitors.h"
+#include "mlir/Support/CyclicReplacerCache.h"
#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/DenseMap.h"
#include <optional>
@@ -116,9 +117,21 @@ class AttrTypeWalker {
/// AttrTypeReplacer
//===----------------------------------------------------------------------===//
-/// This class provides a utility for replacing attributes/types, and their sub
-/// elements. Multiple replacement functions may be registered.
-class AttrTypeReplacer {
+namespace detail {
+
+/// This class provides a base utility for replacing attributes/types, and their
+/// sub elements. Multiple replacement functions may be registered.
+///
+/// This base utility is uncached. Users can choose between two cached versions
+/// of this replacer:
+/// * For non-cyclic replacer logic, use `AttrTypeReplacer`.
+/// * For cyclic replacer logic, use `CyclicAttrTypeReplacer`.
+///
+/// Concrete implementations implement the following `replace` entry functions:
+/// * Attribute replace(Attribute attr);
+/// * Type replace(Type type);
+template <typename Concrete>
+class AttrTypeReplacerBase {
public:
//===--------------------------------------------------------------------===//
// Application
@@ -139,12 +152,6 @@ class AttrTypeReplacer {
bool replaceLocs = false,
bool replaceTypes = false);
- /// Replace the given attribute/type, and recursively replace any sub
- /// elements. Returns either the new attribute/type, or nullptr in the case of
- /// failure.
- Attribute replace(Attribute attr);
- Type replace(Type type);
-
//===--------------------------------------------------------------------===//
// Registration
//===--------------------------------------------------------------------===//
@@ -206,21 +213,114 @@ class AttrTypeReplacer {
});
}
-private:
- /// Internal implementation of the `replace` methods above.
- template <typename T, typename ReplaceFns>
- T replaceImpl(T element, ReplaceFns &replaceFns);
-
- /// Replace the sub elements of the given interface.
- template <typename T>
- T replaceSubElements(T interface);
+protected:
+ /// Invokes the registered replacement functions from most recently registered
+ /// to least recently registered until a successful replacement is returned.
+ /// Unless skipping is requested, invokes `replace` on sub-elements of the
+ /// current attr/type.
+ Attribute replaceBase(Attribute attr);
+ Type replaceBase(Type type);
+private:
/// The set of replacement functions that map sub elements.
std::vector<ReplaceFn<Attribute>> attrReplacementFns;
std::vector<ReplaceFn<Type>> typeReplacementFns;
+};
+
+} // namespace detail
+
+/// This is an attribute/type replacer that is naively cached. It is best used
+/// when the replacer logic is guaranteed to not contain cycles. Otherwise, any
+/// re-occurrence of an in-progress element will be skipped.
+class AttrTypeReplacer : public detail::AttrTypeReplacerBase<AttrTypeReplacer> {
+public:
+ Attribute replace(Attribute attr);
+ Type replace(Type type);
+
+private:
+ /// Shared concrete implementation of the public `replace` functions. Invokes
+ /// `replaceBase` with caching.
+ template <typename T>
+ T cachedReplaceImpl(T element);
+
+ // Stores the opaque pointer of an attribute or type.
+ DenseMap<const void *, const void *> cache;
+};
+
+/// This is an attribute/type replacer that supports custom handling of cycles
+/// in the replacer logic. In addition to registering replacer functions, it
+/// allows registering cycle-breaking functions in the same style.
+class CyclicAttrTypeReplacer
+ : public detail::AttrTypeReplacerBase<CyclicAttrTypeReplacer> {
+public:
+ CyclicAttrTypeReplacer();
- /// The set of cached mappings for attributes/types.
- DenseMap<const void *, const void *> attrTypeMap;
+ //===--------------------------------------------------------------------===//
+ // Application
+ //===--------------------------------------------------------------------===//
+
+ Attribute replace(Attribute attr);
+ Type replace(Type type);
+
+ //===--------------------------------------------------------------------===//
+ // Registration
+ //===--------------------------------------------------------------------===//
+
+ /// A cycle-breaking function. This is invoked if the same element is asked to
+ /// be replaced again when the first instance of it is still being replaced.
+ /// This function must not perform any more recursive `replace` calls.
+ /// If it is able to break the cycle, it should return a replacement result.
+ /// Otherwise, it can return std::nullopt to defer cycle breaking to the next
+ /// repeated element. However, the user must guarantee that, in any possible
+ /// cycle, there always exists at least one element that can break the cycle.
+ template <typename T>
+ using CycleBreakerFn = std::function<std::optional<T>(T)>;
+
+ /// Register a cycle-breaking function.
+ /// When breaking cycles, the mostly recently added cycle-breaking functions
+ /// will be invoked first.
+ void addCycleBreaker(CycleBreakerFn<Attribute> fn);
+ void addCycleBreaker(CycleBreakerFn<Type> fn);
+
+ /// Register a cycle-breaking function that doesn't match the default
+ /// signature.
+ template <typename FnT,
+ typename T = typename llvm::function_traits<
+ std::decay_t<FnT>>::template arg_t<0>,
+ typename BaseT = std::conditional_t<std::is_base_of_v<Attribute, T>,
+ Attribute, Type>>
+ std::enable_if_t<!std::is_same_v<T, BaseT>> addCycleBreaker(FnT &&callback) {
+ addCycleBreaker([callback = std::forward<FnT>(callback)](
+ BaseT base) -> std::optional<BaseT> {
+ if (auto derived = dyn_cast<T>(base))
+ return callback(derived);
+ return std::nullopt;
+ });
+ }
+
+private:
+ /// Invokes the registered cycle-breaker functions from most recently
+ /// registered to least recently registered until a successful result is
+ /// returned.
+ std::optional<const void *> breakCycleImpl(void *element);
+
+ /// Shared concrete implementation of the public `replace` functions.
+ template <typename T>
+ T cachedReplaceImpl(T element);
+
+ /// The set of registered cycle-breaker functions.
+ std::vector<CycleBreakerFn<Attribute>> attrCycleBreakerFns;
+ std::vector<CycleBreakerFn<Type>> typeCycleBreakerFns;
+
+ /// A cache of previously-replaced attr/types.
+ /// The key of the cache is the opaque value of an AttrOrType. Using
+ /// AttrOrType allows distinguishing between the two types when invoking
+ /// cycle-breakers. Using its opaque value avoids the cyclic dependency issue
+ /// of directly using `AttrOrType` to instantiate the cache.
+ /// The value of the cache is just the opaque value of the attr/type itself
+ /// (not the PointerUnion).
+ using AttrOrType = PointerUnion<Attribute, Type>;
+ CyclicReplacerCache<void *, const void *> cache;
};
//===----------------------------------------------------------------------===//
diff --git a/mlir/lib/IR/AttrTypeSubElements.cpp b/mlir/lib/IR/AttrTypeSubElements.cpp
index 79b04966be6eb..783236ed3a9df 100644
--- a/mlir/lib/IR/AttrTypeSubElements.cpp
+++ b/mlir/lib/IR/AttrTypeSubElements.cpp
@@ -67,22 +67,28 @@ WalkResult AttrTypeWalker::walkSubElements(T interface, WalkOrder order) {
}
//===----------------------------------------------------------------------===//
-/// AttrTypeReplacer
+/// AttrTypeReplacerBase
//===----------------------------------------------------------------------===//
-void AttrTypeReplacer::addReplacement(ReplaceFn<Attribute> fn) {
+template <typename Concrete>
+void detail::AttrTypeReplacerBase<Concrete>::addReplacement(
+ ReplaceFn<Attribute> fn) {
attrReplacementFns.emplace_back(std::move(fn));
}
-void AttrTypeReplacer::addReplacement(ReplaceFn<Type> fn) {
+
+template <typename Concrete>
+void detail::AttrTypeReplacerBase<Concrete>::addReplacement(
+ ReplaceFn<Type> fn) {
typeReplacementFns.push_back(std::move(fn));
}
-void AttrTypeReplacer::replaceElementsIn(Operation *op, bool replaceAttrs,
- bool replaceLocs, bool replaceTypes) {
+template <typename Concrete>
+void detail::AttrTypeReplacerBase<Concrete>::replaceElementsIn(
+ Operation *op, bool replaceAttrs, bool replaceLocs, bool replaceTypes) {
// Functor that replaces the given element if the new value is different,
// otherwise returns nullptr.
auto replaceIfDifferent = [&](auto element) {
- auto replacement = replace(element);
+ auto replacement = static_cast<Concrete *>(this)->replace(element);
return (replacement && replacement != element) ? replacement : nullptr;
};
@@ -127,17 +133,16 @@ void AttrTypeReplacer::replaceElementsIn(Operation *op, bool replaceAttrs,
}
}
-void AttrTypeReplacer::recursivelyReplaceElementsIn(Operation *op,
- bool replaceAttrs,
- bool replaceLocs,
- bool replaceTypes) {
+template <typename Concrete>
+void detail::AttrTypeReplacerBase<Concrete>::recursivelyReplaceElementsIn(
+ Operation *op, bool replaceAttrs, bool replaceLocs, bool replaceTypes) {
op->walk([&](Operation *nestedOp) {
replaceElementsIn(nestedOp, replaceAttrs, replaceLocs, replaceTypes);
});
}
-template <typename T>
-static void updateSubElementImpl(T element, AttrTypeReplacer &replacer,
+template <typename T, typename Replacer>
+static void updateSubElementImpl(T element, Replacer &replacer,
SmallVectorImpl<T> &newElements,
FailureOr<bool> &changed) {
// Bail early if we failed at any point.
@@ -160,18 +165,18 @@ static void updateSubElementImpl(T element, AttrTypeReplacer &replacer,
}
}
-template <typename T>
-T AttrTypeReplacer::replaceSubElements(T interface) {
+template <typename T, typename Replacer>
+static T replaceSubElements(T interface, Replacer &replacer) {
// Walk the current sub-elements, replacing them as necessary.
SmallVector<Attribute, 16> newAttrs;
SmallVector<Type, 16> newTypes;
FailureOr<bool> changed = false;
interface.walkImmediateSubElements(
[&](Attribute element) {
- updateSubElementImpl(element, *this, newAttrs, changed);
+ updateSubElementImpl(element, replacer, newAttrs, changed);
},
[&](Type element) {
- updateSubElementImpl(element, *this, newTypes, changed);
+ updateSubElementImpl(element, replacer, newTypes, changed);
});
if (failed(changed))
return nullptr;
@@ -184,13 +189,9 @@ T AttrTypeReplacer::replaceSubElements(T interface) {
}
/// Shared implementation of replacing a given attribute or type element.
-template <typename T, typename ReplaceFns>
-T AttrTypeReplacer::replaceImpl(T element, ReplaceFns &replaceFns) {
- const void *opaqueElement = element.getAsOpaquePointer();
- auto [it, inserted] = attrTypeMap.try_emplace(opaqueElement, opaqueElement);
- if (!inserted)
- return T::getFromOpaquePointer(it->second);
-
+template <typename T, typename ReplaceFns, typename Replacer>
+static T replaceElementImpl(T element, ReplaceFns &replaceFns,
+ Replacer &replacer) {
T result = element;
WalkResult walkResult = WalkResult::advance();
for (auto &replaceFn : llvm::reverse(replaceFns)) {
@@ -202,29 +203,114 @@ T AttrTypeReplacer::replaceImpl(T element, ReplaceFns &replaceFns) {
// If an error occurred, return nullptr to indicate failure.
if (walkResult.wasInterrupted() || !result) {
- attrTypeMap[opaqueElement] = nullptr;
return nullptr;
}
// Handle replacing sub-elements if this element is also a container.
if (!walkResult.wasSkipped()) {
// Replace the sub elements of this element, bailing if we fail.
- if (!(result = replaceSubElements(result))) {
- attrTypeMap[opaqueElement] = nullptr;
+ if (!(result = replaceSubElements(result, replacer))) {
return nullptr;
}
}
- attrTypeMap[opaqueElement] = result.getAsOpaquePointer();
+ return result;
+}
+
+template <typename Concrete>
+Attribute detail::AttrTypeReplacerBase<Concrete>::replaceBase(Attribute attr) {
+ return replaceElementImpl(attr, attrReplacementFns,
+ *static_cast<Concrete *>(this));
+}
+
+template <typename Concrete>
+Type detail::AttrTypeReplacerBase<Concrete>::replaceBase(Type type) {
+ return replaceElementImpl(type, typeReplacementFns,
+ *static_cast<Concrete *>(this));
+}
+
+//===----------------------------------------------------------------------===//
+/// AttrTypeReplacer
+//===----------------------------------------------------------------------===//
+
+template class detail::AttrTypeReplacerBase<AttrTypeReplacer>;
+
+template <typename T>
+T AttrTypeReplacer::cachedReplaceImpl(T element) {
+ const void *opaqueElement = element.getAsOpaquePointer();
+ auto [it, inserted] = cache.try_emplace(opaqueElement, opaqueElement);
+ if (!inserted)
+ return T::getFromOpaquePointer(it->second);
+
+ T result = replaceBase(element);
+
+ cache[opaqueElement] = result.getAsOpaquePointer();
return result;
}
Attribute AttrTypeReplacer::replace(Attribute attr) {
- return replaceImpl(attr, attrReplacementFns);
+ return cachedReplaceImpl(attr);
}
-Type AttrTypeReplacer::replace(Type type) {
- return replaceImpl(type, typeReplacementFns);
+Type AttrTypeReplacer::replace(Type type) { return cachedReplaceImpl(type); }
+
+//===----------------------------------------------------------------------===//
+/// CyclicAttrTypeReplacer
+//===----------------------------------------------------------------------===//
+
+template class detail::AttrTypeReplacerBase<CyclicAttrTypeReplacer>;
+
+CyclicAttrTypeReplacer::CyclicAttrTypeReplacer()
+ : cache([&](void *attr) { return breakCycleImpl(attr); }) {}
+
+void CyclicAttrTypeReplacer::addCycleBreaker(CycleBreakerFn<Attribute> fn) {
+ attrCycleBreakerFns.emplace_back(std::move(fn));
+}
+
+void CyclicAttrTypeReplacer::addCycleBreaker(CycleBreakerFn<Type> fn) {
+ typeCycleBreakerFns.emplace_back(std::move(fn));
+}
+
+template <typename T>
+T CyclicAttrTypeReplacer::cachedReplaceImpl(T element) {
+ void *opaqueTaggedElement = AttrOrType(element).getOpaqueValue();
+ CyclicReplacerCache<void *, const void *>::CacheEntry cacheEntry =
+ cache.lookupOrInit(opaqueTaggedElement);
+ if (auto resultOpt = cacheEntry.get())
+ return T::getFromOpaquePointer(*resultOpt);
+
+ T result = replaceBase(element);
+
+ cacheEntry.resolve(result.getAsOpaquePointer());
+ return result;
+}
+
+Attribute CyclicAttrTypeReplacer::replace(Attribute attr) {
+ return cachedReplaceImpl(attr);
+}
+
+Type CyclicAttrTypeReplacer::replace(Type type) {
+ return cachedReplaceImpl(type);
+}
+
+std::optional<const void *>
+CyclicAttrTypeReplacer::breakCycleImpl(void *element) {
+ AttrOrType attrType = AttrOrType::getFromOpaqueValue(element);
+ if (auto attr = dyn_cast<Attribute>(attrType)) {
+ for (auto &cyclicReplaceFn : llvm::reverse(attrCycleBreakerFns)) {
+ if (std::optional<Attribute> newRes = cyclicReplaceFn(attr)) {
+ return newRes->getAsOpaquePointer();
+ }
+ }
+ } else {
+ auto type = dyn_cast<Type>(attrType);
+ for (auto &cyclicReplaceFn : llvm::reverse(typeCycleBreakerFns)) {
+ if (std::optional<Type> newRes = cyclicReplaceFn(type)) {
+ return newRes->getAsOpaquePointer();
+ }
+ }
+ }
+ return std::nullopt;
}
//===----------------------------------------------------------------------===//
diff --git a/mlir/unittests/IR/AttrTypeReplacerTest.cpp b/mlir/unittests/IR/AttrTypeReplacerTest.cpp
new file mode 100644
index 0000000000000..c7b42eb267c7a
--- /dev/null
+++ b/mlir/unittests/IR/AttrTypeReplacerTest.cpp
@@ -0,0 +1,231 @@
+//===- AttrTypeReplacerTest.cpp - Sub-element replacer unit tests ---------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#include "mlir/IR/AttrTypeSubElements.h"
+#include "mlir/IR/Builders.h"
+#include "mlir/IR/BuiltinAttributes.h"
+#include "mlir/IR/BuiltinTypes.h"
+#include "gtest/gtest.h"
+
+using namespace mlir;
+
+//===----------------------------------------------------------------------===//
+// CyclicAttrTypeReplacer
+//===----------------------------------------------------------------------===//
+
+TEST(CyclicAttrTypeReplacerTest, testNoRecursion) {
+ MLIRContext ctx;
+
+ CyclicAttrTypeReplacer replacer;
+ replacer.addReplacement([&](BoolAttr b) {
+ return StringAttr::get(&ctx, b.getValue() ? "true" : "false");
+ });
+
+ EXPECT_EQ(replacer.replace(BoolAttr::get(&ctx, true)),
+ StringAttr::get(&ctx, "true"));
+ EXPECT_EQ(replacer.replace(BoolAttr::get(&ctx, false)),
+ StringAttr::get(&ctx, "false"));
+ EXPECT_EQ(replacer.replace(mlir::UnitAttr::get(&ctx)),
+ mlir::UnitAttr::get(&ctx));
+}
+
+TEST(CyclicAttrTypeReplacerTest, testInPlaceRecursionPruneAnywhere) {
+ MLIRContext ctx;
+ Builder b(&ctx);
+
+ CyclicAttrTypeReplacer replacer;
+ // Replacer cycles through integer attrs 0 -> 1 -> 2 -> 0 -> ...
+ replacer.addReplacement([&](IntegerAttr attr) {
+ return replacer.replace(b.getI8IntegerAttr((attr.getInt() + 1) % 3));
+ });
+ // The first repeat of any integer attr is pruned into a unit attr.
+ replacer.addCycleBreaker([&](IntegerAttr attr) { return b.getUnitAttr(); });
+
+ // No recursion case.
+ EXPECT_EQ(replacer.replace(mlir::UnitAttr::get(&ctx)),
+ mlir::UnitAttr::get(&ctx));
+ // Starting at 0.
+ EXPECT_EQ(replacer.replace(b.getI8IntegerAttr(0)), mlir::UnitAttr::get(&ctx));
+ // Starting at 2.
+ EXPECT_EQ(replacer.replace(b.getI8IntegerAttr(2)), mlir::UnitAttr::get(&ctx));
+}
+
+//===----------------------------------------------------------------------===//
+// CyclicAttrTypeReplacerTest: ChainRecursion
+//===----------------------------------------------------------------------===//
+
+class CyclicAttrTypeReplacerChainRecursionPruningTest : public ::testing::Test {
+public:
+ CyclicAttrTypeReplacerChainRecursionPruningTest() : b(&ctx) {
+ // IntegerType<width = N>
+ // ==> FunctionType<() => IntegerType< width = (N+1) % 3>>.
+ // This will create a chain of infinite length without recursion pruning.
+ replacer.addReplacement([&](mlir::IntegerType intType) {
+ ++invokeCount;
+ return b.getFunctionType(
+ {}, {mlir::IntegerType::get(&ctx, (intType.getWidth() + 1) % 3)});
+ });
+ }
+
+ void setBaseCase(std::optional<unsigned> pruneAt) {
+ replacer.addCycleBreaker([&, pruneAt](mlir::IntegerType intType) {
+ return (!pruneAt || intType.getWidth() == *pruneAt)
+ ? std::make_optional(b.getIndexType())
+ : std::nullopt;
+ });
+ }
+
+ Type getFunctionTypeChain(unsigned N) {
+ Type type = b.getIndexType();
+ for (unsigned i = 0; i < N; i++)
+ type = b.getFunctionType({}, type);
+ return type;
+ };
+
+ MLIRContext ctx;
+ Builder b;
+ CyclicAttrTypeReplacer replacer;
+ int invokeCount = 0;
+};
+
+TEST_F(CyclicAttrTypeReplacerChainRecursionPruningTest, testPruneAnywhere0) {
+ setBaseCase(std::nullopt);
+
+ // No recursion case.
+ EXPECT_EQ(replacer.replace(b.getIndexType()), b.getIndexType());
+ EXPECT_EQ(invokeCount, 0);
+
+ // Starting at 0. Cycle length is 3.
+ invokeCount = 0;
+ EXPECT_EQ(replacer.replace(mlir::IntegerType::get(&ctx, 0)),
+ getFunctionTypeChain(3));
+ EXPECT_EQ(invokeCount, 3);
+
+ // Starting at 1. Cycle length is 5 now because of a cached replacement at 0.
+ invokeCount = 0;
+ EXPECT_EQ(replacer.replace(mlir::IntegerType::get(&ctx, 1)),
+ getFunctionTypeChain(5));
+ EXPECT_EQ(invokeCount, 2);
+}
+
+TEST_F(CyclicAttrTypeReplacerChainRecursionPruningTest, testPruneAnywhere1) {
+ setBaseCase(std::nullopt);
+
+ // Starting at 1. Cycle length is 3.
+ EXPECT_EQ(replacer.replace(mlir::IntegerType::get(&ctx, 1)),
+ getFunctionTypeChain(3));
+ EXPECT_EQ(invokeCount, 3);
+}
+
+TEST_F(CyclicAttrTypeReplacerChainRecursionPruningTest, testPruneSpecific0) {
+ setBaseCase(0);
+
+ // Starting at 0. Cycle length is 3.
+ EXPECT_EQ(replacer.replace(mlir::IntegerType::get(&ctx, 0)),
+ getFunctionTypeChain(3));
+ EXPECT_EQ(invokeCount, 3);
+}
+
+TEST_F(CyclicAttrTypeReplacerChainRecursionPruningTest, testPruneSpecific1) {
+ setBaseCase(0);
+
+ // Starting at 1. Cycle length is 5 (1 -> 2 -> 0 -> 1 -> 2 -> Prune).
+ EXPECT_EQ(replacer.replace(mlir::IntegerType::get(&ctx, 1)),
+ getFunctionTypeChain(5));
+ EXPECT_EQ(invokeCount, 5);
+}
+
+//===----------------------------------------------------------------------===//
+// CyclicAttrTypeReplacerTest: BranchingRecusion
+//===----------------------------------------------------------------------===//
+
+class CyclicAttrTypeReplacerBranchingRecusionPruningTest
+ : public ::testing::Test {
+public:
+ CyclicAttrTypeReplacerBranchingRecusionPruningTest() : b(&ctx) {
+ // IntegerType<width = N>
+ // ==> FunctionType<
+ // IntegerType< width = (N+1) % 3> =>
+ // IntegerType< width = (N+1) % 3>>.
+ // This will create a binary tree of infinite depth without pruning.
+ replacer.addReplacement([&](mlir::IntegerType intType) {
+ ++invokeCount;
+ Type child = mlir::IntegerType::get(&ctx, (intType.getWidth() + 1) % 3);
+ return b.getFunctionType({child}, {child});
+ });
+ }
+
+ void setBaseCase(std::optional<unsigned> pruneAt) {
+ replacer.addCycleBreaker([&, pruneAt](mlir::IntegerType intType) {
+ return (!pruneAt || intType.getWidth() == *pruneAt)
+ ? std::make_optional(b.getIndexType())
+ : std::nullopt;
+ });
+ }
+
+ Type getFunctionTypeTree(unsigned N) {
+ Type type = b.getIndexType();
+ for (unsigned i = 0; i < N; i++)
+ type = b.getFunctionType(type, type);
+ return type;
+ };
+
+ MLIRContext ctx;
+ Builder b;
+ CyclicAttrTypeReplacer replacer;
+ int invokeCount = 0;
+};
+
+TEST_F(CyclicAttrTypeReplacerBranchingRecusionPruningTest, testPruneAnywhere0) {
+ setBaseCase(std::nullopt);
+
+ // No recursion case.
+ EXPECT_EQ(replacer.replace(b.getIndexType()), b.getIndexType());
+ EXPECT_EQ(invokeCount, 0);
+
+ // Starting at 0. Cycle length is 3.
+ invokeCount = 0;
+ EXPECT_EQ(replacer.replace(mlir::IntegerType::get(&ctx, 0)),
+ getFunctionTypeTree(3));
+ // Since both branches are identical, this should incur linear invocations
+ // of the replacement function instead of exponential.
+ EXPECT_EQ(invokeCount, 3);
+
+ // Starting at 1. Cycle length is 5 now because of a cached replacement at 0.
+ invokeCount = 0;
+ EXPECT_EQ(replacer.replace(mlir::IntegerType::get(&ctx, 1)),
+ getFunctionTypeTree(5));
+ EXPECT_EQ(invokeCount, 2);
+}
+
+TEST_F(CyclicAttrTypeReplacerBranchingRecusionPruningTest, testPruneAnywhere1) {
+ setBaseCase(std::nullopt);
+
+ // Starting at 1. Cycle length is 3.
+ EXPECT_EQ(replacer.replace(mlir::IntegerType::get(&ctx, 1)),
+ getFunctionTypeTree(3));
+ EXPECT_EQ(invokeCount, 3);
+}
+
+TEST_F(CyclicAttrTypeReplacerBranchingRecusionPruningTest, testPruneSpecific0) {
+ setBaseCase(0);
+
+ // Starting at 0. Cycle length is 3.
+ EXPECT_EQ(replacer.replace(mlir::IntegerType::get(&ctx, 0)),
+ getFunctionTypeTree(3));
+ EXPECT_EQ(invokeCount, 3);
+}
+
+TEST_F(CyclicAttrTypeReplacerBranchingRecusionPruningTest, testPruneSpecific1) {
+ setBaseCase(0);
+
+ // Starting at 1. Cycle length is 5 (1 -> 2 -> 0 -> 1 -> 2 -> Prune).
+ EXPECT_EQ(replacer.replace(mlir::IntegerType::get(&ctx, 1)),
+ getFunctionTypeTree(5));
+ EXPECT_EQ(invokeCount, 5);
+}
diff --git a/mlir/unittests/IR/CMakeLists.txt b/mlir/unittests/IR/CMakeLists.txt
index 71f8f449756ec..05cb36e190316 100644
--- a/mlir/unittests/IR/CMakeLists.txt
+++ b/mlir/unittests/IR/CMakeLists.txt
@@ -3,6 +3,7 @@ add_mlir_unittest(MLIRIRTests
AffineExprTest.cpp
AffineMapTest.cpp
AttributeTest.cpp
+ AttrTypeReplacerTest.cpp
DialectTest.cpp
InterfaceTest.cpp
IRMapping.cpp
>From 5ccbf4bc13ac48240d9fcb14411617809e527304 Mon Sep 17 00:00:00 2001
From: Billy Zhu <billyzhu at modular.com>
Date: Tue, 9 Jul 2024 13:58:34 -0700
Subject: [PATCH 3/5] typo & comments
---
mlir/unittests/Support/CyclicReplacerCacheTest.cpp | 12 +++++++-----
1 file changed, 7 insertions(+), 5 deletions(-)
diff --git a/mlir/unittests/Support/CyclicReplacerCacheTest.cpp b/mlir/unittests/Support/CyclicReplacerCacheTest.cpp
index 23748e29765cb..a4a92dbe147d4 100644
--- a/mlir/unittests/Support/CyclicReplacerCacheTest.cpp
+++ b/mlir/unittests/Support/CyclicReplacerCacheTest.cpp
@@ -195,17 +195,19 @@ class CachedCyclicReplacerGraphReplacement : public ::testing::Test {
/// A Graph where edges that used to cause cycles (back-edges) are now
/// represented with an indirection (a recursionId).
///
- /// In addition to each node being an integer, each node also tracks the
- /// original integer id it had in the original graph. This way for every
+ /// In addition to each node having an integer ID, each node also tracks the
+ /// original integer ID it had in the original graph. This way for every
/// back-edge, we can represent it as pointing to a new instance of the
/// original node. Then we mark the original node and the new instance with
/// a new unique recursionId to indicate that they're supposed to be the same
- /// graph.
+ /// node.
struct PrunedGraph {
using Node = Graph::Node;
struct NodeInfo {
Graph::Node originalId;
- // A negative recursive index means not recursive.
+ /// A negative recursive index means not recursive. Otherwise nodes with
+ /// the same originalId & recursionId are the same node in the original
+ /// graph.
int64_t recursionId;
};
@@ -243,7 +245,7 @@ class CachedCyclicReplacerGraphReplacement : public ::testing::Test {
Graph connections;
int64_t nextRecursionId = 0;
int64_t nextConnectionId = 0;
- // Use ordered map for deterministic output.
+ /// Use ordered map for deterministic output.
std::map<Graph::Node, NodeInfo> info;
};
>From a27223a7375afaaf5abd66c26d6b0f4fda372abf Mon Sep 17 00:00:00 2001
From: Billy Zhu <billyzhu at modular.com>
Date: Thu, 11 Jul 2024 10:59:52 -0700
Subject: [PATCH 4/5] Apply suggestions from code review
Co-authored-by: Jeff Niu <jeff at modular.com>
---
mlir/include/mlir/Support/CyclicReplacerCache.h | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/mlir/include/mlir/Support/CyclicReplacerCache.h b/mlir/include/mlir/Support/CyclicReplacerCache.h
index 9a703676fff11..7ad8c717199ec 100644
--- a/mlir/include/mlir/Support/CyclicReplacerCache.h
+++ b/mlir/include/mlir/Support/CyclicReplacerCache.h
@@ -82,14 +82,14 @@ class CyclicReplacerCache {
}
/// Get the resolved result if one exists.
- std::optional<OutT> get() { return result; }
+ const std::optional<OutT> &get() { return result; }
private:
friend class CyclicReplacerCache;
CacheEntry() = delete;
CacheEntry(CyclicReplacerCache<InT, OutT> &cache, InT element,
std::optional<OutT> result = std::nullopt)
- : cache(cache), element(element), result(result) {}
+ : cache(cache), element(std::move(element)), result(result) {}
CyclicReplacerCache<InT, OutT> &cache;
InT element;
@@ -153,7 +153,7 @@ CyclicReplacerCache<InT, OutT>::lookupOrInit(const InT &element) {
return CacheEntry(*this, element, it->second);
if (auto it = dependentCache.find(element); it != dependentCache.end()) {
- // pdate the current top frame (the element that invoked this current
+ // Update the current top frame (the element that invoked this current
// replacement) to include any dependencies the cache entry had.
ReplacementFrame &currFrame = replacementStack.back();
currFrame.dependentFrames.insert(it->second.highestDependentFrame);
>From 1abb63f81154de65757b25717a1e616b5b8971d1 Mon Sep 17 00:00:00 2001
From: Billy Zhu <billyzhu at modular.com>
Date: Thu, 11 Jul 2024 11:18:02 -0700
Subject: [PATCH 5/5] double down on trivial type support
---
.../mlir/Support/CyclicReplacerCache.h | 29 ++++++++++---------
.../Support/CyclicReplacerCacheTest.cpp | 4 +++
2 files changed, 20 insertions(+), 13 deletions(-)
diff --git a/mlir/include/mlir/Support/CyclicReplacerCache.h b/mlir/include/mlir/Support/CyclicReplacerCache.h
index 7ad8c717199ec..42428c1507ffb 100644
--- a/mlir/include/mlir/Support/CyclicReplacerCache.h
+++ b/mlir/include/mlir/Support/CyclicReplacerCache.h
@@ -12,8 +12,8 @@
//
//===----------------------------------------------------------------------===//
-#ifndef MLIR_SUPPORT_CACHINGREPLACER_H
-#define MLIR_SUPPORT_CACHINGREPLACER_H
+#ifndef MLIR_SUPPORT_CYCLICREPLACERCACHE_H
+#define MLIR_SUPPORT_CYCLICREPLACERCACHE_H
#include "mlir/IR/Visitors.h"
#include "llvm/ADT/DenseSet.h"
@@ -43,13 +43,16 @@ namespace mlir {
/// any given cycle can perform pruning. Even if not, an assertion will
/// eventually be tripped instead of infinite recursion (the run-time is
/// linearly bounded by the maximum cycle length of its input).
+///
+/// WARNING: This class works best with InT & OutT that are trivial scalar
+/// types. The input/output elements will be frequently copied and hashed.
template <typename InT, typename OutT>
class CyclicReplacerCache {
public:
/// User-provided replacement function & cycle-breaking functions.
/// The cycle-breaking function must not make any more recursive invocations
/// to this cached replacer.
- using CycleBreakerFn = std::function<std::optional<OutT>(const InT &)>;
+ using CycleBreakerFn = std::function<std::optional<OutT>(InT)>;
CyclicReplacerCache() = delete;
CyclicReplacerCache(CycleBreakerFn cycleBreaker)
@@ -77,12 +80,12 @@ class CyclicReplacerCache {
/// in the cache.
void resolve(OutT result) {
assert(!this->result && "cache entry already resolved");
- this->result = result;
cache.finalizeReplacement(element, result);
+ this->result = std::move(result);
}
/// Get the resolved result if one exists.
- const std::optional<OutT> &get() { return result; }
+ const std::optional<OutT> &get() const { return result; }
private:
friend class CyclicReplacerCache;
@@ -106,11 +109,11 @@ class CyclicReplacerCache {
/// retrieval, i.e. the last retrieved CacheEntry must be resolved first, and
/// the first retrieved CacheEntry must be resolved last. This should be
/// natural when used as a stack / inside recursion.
- CacheEntry lookupOrInit(const InT &element);
+ CacheEntry lookupOrInit(InT element);
private:
/// Register the replacement in the cache and update the replacementStack.
- void finalizeReplacement(const InT &element, const OutT &result);
+ void finalizeReplacement(InT element, OutT result);
CycleBreakerFn cycleBreaker;
DenseMap<InT, OutT> standaloneCache;
@@ -145,7 +148,7 @@ class CyclicReplacerCache {
template <typename InT, typename OutT>
typename CyclicReplacerCache<InT, OutT>::CacheEntry
-CyclicReplacerCache<InT, OutT>::lookupOrInit(const InT &element) {
+CyclicReplacerCache<InT, OutT>::lookupOrInit(InT element) {
assert(!resolvingCycle &&
"illegal recursive invocation while breaking cycle");
@@ -195,8 +198,8 @@ CyclicReplacerCache<InT, OutT>::lookupOrInit(const InT &element) {
}
template <typename InT, typename OutT>
-void CyclicReplacerCache<InT, OutT>::finalizeReplacement(const InT &element,
- const OutT &result) {
+void CyclicReplacerCache<InT, OutT>::finalizeReplacement(InT element,
+ OutT result) {
ReplacementFrame &currFrame = replacementStack.back();
// With the conclusion of this replacement frame, the current element is no
// longer a dependent element.
@@ -249,7 +252,7 @@ void CyclicReplacerCache<InT, OutT>::finalizeReplacement(const InT &element,
template <typename InT, typename OutT>
class CachedCyclicReplacer {
public:
- using ReplacerFn = std::function<OutT(const InT &)>;
+ using ReplacerFn = std::function<OutT(InT)>;
using CycleBreakerFn =
typename CyclicReplacerCache<InT, OutT>::CycleBreakerFn;
@@ -257,7 +260,7 @@ class CachedCyclicReplacer {
CachedCyclicReplacer(ReplacerFn replacer, CycleBreakerFn cycleBreaker)
: replacer(std::move(replacer)), cache(std::move(cycleBreaker)) {}
- OutT operator()(const InT &element) {
+ OutT operator()(InT element) {
auto cacheEntry = cache.lookupOrInit(element);
if (std::optional<OutT> result = cacheEntry.get())
return *result;
@@ -274,4 +277,4 @@ class CachedCyclicReplacer {
} // namespace mlir
-#endif // MLIR_SUPPORT_CACHINGREPLACER_H
+#endif // MLIR_SUPPORT_CYCLICREPLACERCACHE_H
diff --git a/mlir/unittests/Support/CyclicReplacerCacheTest.cpp b/mlir/unittests/Support/CyclicReplacerCacheTest.cpp
index a4a92dbe147d4..ca02a3d692b2a 100644
--- a/mlir/unittests/Support/CyclicReplacerCacheTest.cpp
+++ b/mlir/unittests/Support/CyclicReplacerCacheTest.cpp
@@ -47,6 +47,7 @@ TEST(CachedCyclicReplacerTest, testInPlaceRecursionPruneAnywhere) {
/// infinitely long vector. The cycle-breaker function prunes this infinite
/// recursion in the replacer logic by returning an empty vector upon the first
/// re-occurrence of an input value.
+namespace {
class CachedCyclicReplacerChainRecursionPruningTest : public ::testing::Test {
public:
// N ==> (N+1) % 3
@@ -71,6 +72,7 @@ class CachedCyclicReplacerChainRecursionPruningTest : public ::testing::Test {
int invokeCount = 0;
std::optional<int> baseCase = std::nullopt;
};
+} // namespace
TEST_F(CachedCyclicReplacerChainRecursionPruningTest, testPruneAnywhere0) {
// Starting at 0. Cycle length is 3.
@@ -128,6 +130,7 @@ TEST_F(CachedCyclicReplacerChainRecursionPruningTest, testPruneSpecific1) {
/// - PrunedGraph
/// - A Graph where edges that used to cause cycles are now represented with
/// an indirection (a recursionId).
+namespace {
class CachedCyclicReplacerGraphReplacement : public ::testing::Test {
public:
/// A directed graph where nodes are non-negative integers.
@@ -317,6 +320,7 @@ class CachedCyclicReplacerGraphReplacement : public ::testing::Test {
return oss.str();
}
};
+} // namespace
TEST_F(CachedCyclicReplacerGraphReplacement, testSingleLoop) {
// 0 -> 1 -> 2
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