[GitHub] [tvm] Lunderberg commented on a diff in pull request #12352: [TIR] Add pass to check for out of bounds memory access

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

Lunderberg commented on code in PR #12352:
URL: https://github.com/apache/tvm/pull/12352#discussion_r942866132


##########
src/tir/analysis/oob_checker.cc:
##########
@@ -0,0 +1,122 @@
+/*
+ * 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.
+ */
+
+/*!
+ *  Out of bounds array access static analyzer.
+ */
+
+#include <tvm/tir/transform.h>
+
+#include "../../arith/ir_visitor_with_analyzer.h"
+#include "../../printer/text_printer.h"
+#include "../schedule/error.h"
+
+namespace tvm {
+namespace tir {
+namespace transform {
+struct OOBLocation {
+  Buffer buf;
+  size_t dimension;
+  ObjectRef index;
+  arith::IntSet index_bounds;
+  arith::IntSet shape_bounds;
+};
+
+class OOBError : public ScheduleError {
+ public:
+  OOBError(IRModule mod, std::vector<OOBLocation> locations) : mod_(mod), locations_(locations) {}
+  String FastErrorString() const final { return "Out of bound memory access"; }
+
+  String DetailRenderTemplate() const final {
+    std::stringstream s;
+    for (const auto& oob : locations_) {
+      s << "Out of bounds memory access on buffer " << oob.buf->name << " dimension "
+        << oob.dimension << ".";
+      s << " index " << oob.index << " with bounds [" << oob.index_bounds.min() << ", "
+        << oob.index_bounds.max() << "] is outside the range [0, " << oob.shape_bounds.min()
+        << "].";
+      s << "\n";
+    }
+    return s.str();
+  }
+  IRModule mod() const final { return mod_; }
+  Array<ObjectRef> LocationsOfInterest() const final {
+    std::vector<ObjectRef> locs;
+    for (auto loc : locations_) {
+      locs.push_back(loc.index);
+    }
+    return locs;
+  }
+
+ private:
+  IRModule mod_;
+  std::vector<OOBLocation> locations_;
+};
+class OOBCheckerVisitor final : public arith::IRVisitorWithAnalyzer {
+  using IRVisitorWithAnalyzer::VisitExpr_;
+  using IRVisitorWithAnalyzer::VisitStmt_;
+
+ public:
+  void VisitStmt_(const BufferStoreNode* node) final {
+    for (size_t i = 0; i < node->buffer->shape.size(); i++) {
+      CheckBounds(node, i);
+    }
+    IRVisitorWithAnalyzer::VisitStmt_(node);
+  }
+  void VisitExpr_(const BufferLoadNode* node) final {
+    for (size_t i = 0; i < node->buffer->shape.size(); i++) {
+      CheckBounds(node, i);
+    }
+    IRVisitorWithAnalyzer::VisitExpr_(node);
+  }
+
+  template <class T>
+  void CheckBounds(const T* node, size_t i) {
+    auto ind_bounds = analyzer_.int_set(node->indices[i]);
+    auto shape_bounds = analyzer_.int_set(node->buffer->shape[i]);
+    // Only show an error if we can prove that the access occurs out of bounds.
+    // In some cases we may not be able to prove that the access is in or out
+    // of bounds and we would like to ignore these cases.
+    if (analyzer_.CanProve(ind_bounds.max() >= shape_bounds.min()) ||

Review Comment:
   Do we need to use the `int_set` analyzer here?  Why not `analyzer_.CanProve(node->indices[i] < 0 || node->indices[i] >= node->buffer->shape[i])`.



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