[GitHub] [tvm] ArmageddonKnight commented on a diff in pull request #11793: [DietCode] Local Padding

[GitBox <gi...@apache.org>]

ArmageddonKnight commented on code in PR #11793:
URL: https://github.com/apache/tvm/pull/11793#discussion_r913288805


##########
src/tir/transforms/local_pad.cc:
##########
@@ -0,0 +1,302 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+#include <tvm/meta_schedule/postproc.h>
+#include <tvm/tir/op.h>
+#include <tvm/tir/stmt.h>
+#include <tvm/tir/stmt_functor.h>
+#include <tvm/tir/transform.h>
+
+#include <array>
+#include <utility>
+#include <vector>
+
+namespace tvm {
+namespace tir {
+namespace transform {
+namespace {
+
+/*!
+ * \brief Analyze the read and write accesses of the body statements, used by `LocalPadder`.
+ */
+class StorageAccessAnalyzer : public StmtExprVisitor {
+ private:
+  struct StorageType {
+    enum { kGlobal = 0, kShared, kLocal, kOthers };
+  };
+
+  void VisitStmt_(const BufferStoreNode* op) final {
+    write_marker_.SetStorageAccessMarker_(op->buffer);
+    StmtExprVisitor::VisitStmt_(op);
+  }
+  void VisitExpr_(const BufferLoadNode* op) final {
+    read_marker_.SetStorageAccessMarker_(op->buffer);
+    StmtExprVisitor::VisitExpr_(op);
+  }
+  class AccessMarker {
+   public:
+    void SetStorageAccessMarker_(const Buffer& buf) {
+      if (buf.scope() == "global") {
+        bit_vector_[StorageType::kGlobal] = true;
+      } else if (buf.scope() == "shared") {
+        bit_vector_[StorageType::kShared] = true;
+      } else if (buf.scope() == "local") {
+        bit_vector_[StorageType::kLocal] = true;
+      } else {
+        bit_vector_[StorageType::kOthers] = true;
+      }
+    }
+    bool NoAccesses() const {
+      return !(bit_vector_[StorageType::kGlobal] || bit_vector_[StorageType::kShared] ||
+               bit_vector_[StorageType::kLocal] || bit_vector_[StorageType::kOthers]);
+    }
+    bool OnlyGlobalAccesses() const {
+      return !(bit_vector_[StorageType::kShared] || bit_vector_[StorageType::kLocal] ||
+               bit_vector_[StorageType::kOthers]) &&
+             bit_vector_[StorageType::kGlobal];
+    }
+    bool OnlyLocalOrSharedAccesses() const {
+      return !(bit_vector_[StorageType::kGlobal] || bit_vector_[StorageType::kOthers]) &&
+             (bit_vector_[StorageType::kShared] || bit_vector_[StorageType::kLocal]);
+    }
+
+   private:
+    std::array<bool, StorageType::kOthers + 1> bit_vector_ = {false};
+  };
+  AccessMarker read_marker_, write_marker_;
+  std::pair<AccessMarker, AccessMarker> Analyze_(const Stmt& stmt) {
+    VisitStmt(stmt);
+    return std::make_pair(read_marker_, write_marker_);
+  }
+
+  friend class LocalPadder;
+};
+
+/*!
+ * \brief Verify that all local variables are initialized to the same constant expression.
+ */
+class InitChecker : public StmtVisitor {
+ private:
+  void VisitStmt_(const BufferStoreNode* op) final {
+    // Read the check the RHS values, make sure that they are the same constant for all the
+    // initialization statements.
+    CheckInitValue_<IntImmNode>(op->value);
+    CheckInitValue_<FloatImmNode>(op->value);
+    return StmtVisitor::VisitStmt_(op);
+  }
+  template <typename ImmNodeType>
+  void CheckInitValue_(const PrimExpr& rhs) {
+    if (const ImmNodeType* const rhs_val = rhs.as<ImmNodeType>()) {
+      if (init_constexpr_.defined()) {
+        if (const ImmNodeType* const init_val = init_constexpr_.as<ImmNodeType>()) {
+          if (rhs_val->value != init_val->value) {
+            init_with_single_constexpr_ = false;
+          }
+        } else {
+          init_with_single_constexpr_ = false;
+        }
+      } else {
+        init_with_single_constexpr_ = true;
+        init_constexpr_ = rhs;
+      }
+    }
+  }
+  void operator()(const Stmt& stmt) {
+    StmtVisitor::operator()(stmt);
+    if (!init_with_single_constexpr_) {
+      init_constexpr_ = PrimExpr();
+    }
+  }
+
+  bool init_with_single_constexpr_ = false;
+  PrimExpr init_constexpr_;
+
+  friend class LocalPadder;
+};
+
+/*!
+ * \brief Split a predicate into inlinable and non-inlinable component.
+ *
+ *        We refer to "inlinable predicate" as
+ *
+ *            if (predicate) A = ...;
+ *            ↓
+ *            A = predicate ? ... : init_constexpr;
+ *
+ *        Note that not all predicates can be inlined. For example, if a predicate is there to guard
+ *        against out-of-boundary accesses to local/shared variables, then it cannot be inlined.
+ */
+class PredicateInliner : public StmtExprVisitor {
+ private:
+  explicit PredicateInliner(const Stmt& body_stmt) : body_stmt_(body_stmt) {}
+
+#define VISIT_PREDICATE(OpType)                      \
+  void VisitExpr_(const OpType##Node* op) final {    \
+    OpType predicate = GetRef<OpType>(op);           \
+    if (CanInlinePredicate_<OpType##Node>(op)) {     \
+      inlinable_predicates_.push_back(predicate);    \
+    } else {                                         \
+      non_inlinable_residuals_.push_back(predicate); \
+    }                                                \
+  }
+  VISIT_PREDICATE(LT)
+  VISIT_PREDICATE(LE)
+  VISIT_PREDICATE(GT)
+  VISIT_PREDICATE(GE)
+#undef VISIT_PREDICATE
+
+  void VisitStmt_(const BufferStoreNode* op) final {
+    if (op->indices.size() != 1) {
+      return StmtVisitor::VisitStmt_(op);
+    }
+    CHECK(op->buffer.scope() == "shared" || op->buffer.scope() == "local");
+    if (StructuralEqual()(op->indices[0], predicate_lhs_)) {
+      predicate_inlinable_ = false;
+    }

Review Comment:
   Yes.



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