[TIR] Encode conditional accesses info into block read/write regions

src/tir/analysis/block_access_region_detector.cc

@@ -56,6 +56,8 @@ class BlockReadWriteDetector : public StmtExprVisitor {
  private:
   /*! \brief Iteration range for loop_vars */
   std::unordered_map<const VarNode*, arith::IntSet> dom_map_;
+  /*! \brief Extra iteration range hint for free vars */
+  std::unordered_map<const VarNode*, arith::IntSet> hint_map_;
   /*! \brief The buffers that the current block reads */
   std::vector<Buffer> read_buffers_;
   /*! \brief The buffers that the current block writes */
@@ -96,6 +98,9 @@ class BlockReadWriteDetector : public StmtExprVisitor {
   /*! \brief Helper function to update a opaque access. */
   void UpdateOpaque(const Var& buffer_var);
 
+  /*! \brief Helper function to relax the buffer indices */
+  arith::IntSet RelaxAccessIndex(const PrimExpr& index);
+
   void VisitStmt_(const ForNode* op) override;
   void VisitStmt_(const IfThenElseNode* op) override;
   void VisitStmt_(const BlockRealizeNode* op) override;
@@ -140,10 +145,22 @@ void BlockReadWriteDetector::VisitExpr_(const LoadNode* op) {
   ExprVisitor::VisitExpr_(op);
 }
 
+arith::IntSet BlockReadWriteDetector::RelaxAccessIndex(const PrimExpr& index) {
+  arith::IntSet relaxed = arith::EvalSet(index, dom_map_);
+  if (!hint_map_.empty()) {
+    // take non-relaxed var bound hints into considerations
+    // eg, if i * 4 + j with i >= 10 and j in [0, 4), only j in domain scope
+    // then the index region can be relaxed to [i*4, i*4+4) ^ [40, inf)
+    arith::IntSet hint_bound = arith::EvalSet(relaxed, hint_map_);
+    relaxed = arith::Intersect({relaxed, hint_bound});
+  }
+  return relaxed;
+}
+
 void BlockReadWriteDetector::VisitExpr_(const BufferLoadNode* op) {
   std::vector<arith::IntSet> relaxed_region;
   for (const PrimExpr& index : op->indices) {
-    relaxed_region.push_back(arith::EvalSet(index, dom_map_));
+    relaxed_region.push_back(RelaxAccessIndex(index));
   }
   Update(&read_buffers_, &read_regions_, op->buffer, relaxed_region);
   ExprVisitor::VisitExpr_(op);
@@ -160,12 +177,12 @@ void BlockReadWriteDetector::VisitStmt_(const IfThenElseNode* op) {
   VisitExpr(op->condition);
   {
     // Visit then branch
-    With<ConditionalBoundsContext> ctx(op->condition, &dom_map_, true);
+    With<ConditionalBoundsContext> ctx(op->condition, &dom_map_, &hint_map_, true);
     StmtExprVisitor::VisitStmt(op->then_case);
   }
   if (op->else_case.defined()) {
     // Visit else branch
-    With<ConditionalBoundsContext> ctx(op->condition, &dom_map_, false);
+    With<ConditionalBoundsContext> ctx(op->condition, &dom_map_, &hint_map_, false);
     StmtExprVisitor::VisitStmt(op->else_case);
   }
 }
@@ -175,12 +192,12 @@ void BlockReadWriteDetector::VisitExpr_(const CallNode* op) {
     VisitExpr(op->args[0]);
     {
       // Visit then branch
-      With<ConditionalBoundsContext> ctx(op->args[0], &dom_map_, true);
+      With<ConditionalBoundsContext> ctx(op->args[0], &dom_map_, &hint_map_, true);
       StmtExprVisitor::VisitExpr(op->args[1]);
     }
     {
       // Visit else branch
-      With<ConditionalBoundsContext> ctx(op->args[0], &dom_map_, false);
+      With<ConditionalBoundsContext> ctx(op->args[0], &dom_map_, &hint_map_, false);
       StmtExprVisitor::VisitExpr(op->args[2]);
     }
     return;
@@ -196,7 +213,7 @@ void BlockReadWriteDetector::VisitStmt_(const StoreNode* op) {
 void BlockReadWriteDetector::VisitStmt_(const BufferStoreNode* op) {
   std::vector<arith::IntSet> relaxed_region;
   for (const PrimExpr& index : op->indices) {
-    relaxed_region.push_back(arith::EvalSet(index, dom_map_));
+    relaxed_region.push_back(RelaxAccessIndex(index));
   }
   Update(&writes_buffers_, &write_regions_, op->buffer, relaxed_region);
   StmtVisitor::VisitStmt_(op);

src/tir/transforms/compact_buffer_region.cc

@@ -123,12 +123,12 @@ class BufferAccessRegionCollector : public StmtExprVisitor {
     StmtExprVisitor::VisitExpr(op->condition);
     {
       // Visit then branch
-      With<ConditionalBoundsContext> ctx(op->condition, &dom_map_, true);
+      With<ConditionalBoundsContext> ctx(op->condition, &dom_map_, &hint_map_, true);
       StmtExprVisitor::VisitStmt(op->then_case);
     }
     if (op->else_case.defined()) {
       // Visit else branch
-      With<ConditionalBoundsContext> ctx(op->condition, &dom_map_, false);
+      With<ConditionalBoundsContext> ctx(op->condition, &dom_map_, &hint_map_, false);
       StmtExprVisitor::VisitStmt(op->else_case);
     }
   }
@@ -139,12 +139,12 @@ class BufferAccessRegionCollector : public StmtExprVisitor {
       StmtExprVisitor::VisitExpr(op->args[0]);
       {
         // Visit then branch
-        With<ConditionalBoundsContext> ctx(op->args[0], &dom_map_, true);
+        With<ConditionalBoundsContext> ctx(op->args[0], &dom_map_, &hint_map_, true);
         StmtExprVisitor::VisitExpr(op->args[1]);
       }
       {
         // Visit else branch
-        With<ConditionalBoundsContext> ctx(op->args[0], &dom_map_, false);
+        With<ConditionalBoundsContext> ctx(op->args[0], &dom_map_, &hint_map_, false);
         StmtExprVisitor::VisitExpr(op->args[2]);
       }
       return;
@@ -282,6 +282,8 @@ class BufferAccessRegionCollector : public StmtExprVisitor {
 
   /*! \brief The map from loop vars to their iter range. */
   std::unordered_map<const VarNode*, arith::IntSet> dom_map_;
+  /*! \brief Extra map from free vars to their iter range hints. */
+  std::unordered_map<const VarNode*, arith::IntSet> hint_map_;
   /*! \brief The analyzer aware of loop domains. */
   arith::Analyzer dom_analyzer_;
   /*! \brief The map from Buffer to it's relaxed access set. */

src/tir/transforms/ir_utils.cc

@@ -300,11 +300,18 @@ Map<Var, Range> ConditionalBoundsContext::GetVarBoundsFromCondition() {
   Array<Var> vars = Array<Var>(var_set.begin(), var_set.end());
   Map<Var, Range> ranges;
   for (const Var& v : vars) {
-    auto it = dom_map_->find(v.get());
-    if (it != dom_map_->end()) {
-      const auto& int_set = it->second;
-      ranges.Set(v, Range::FromMinExtent(int_set.min(),
-                                         analyzer.Simplify(int_set.max() - int_set.min() + 1)));
+    arith::IntSet dom;
+    auto relax_it = relax_map_->find(v.get());
+    if (relax_it != relax_map_->end()) {
+      dom = relax_it->second;
+    } else {
+      auto hint_it = hint_map_->find(v.get());
+      if (hint_it != hint_map_->end()) {
+        dom = hint_it->second;
+      }
+    }
+    if (dom.defined()) {
+      ranges.Set(v, Range::FromMinExtent(dom.min(), analyzer.Simplify(dom.max() - dom.min() + 1)));
     }
   }
   // solve constraints
@@ -314,24 +321,53 @@ Map<Var, Range> ConditionalBoundsContext::GetVarBoundsFromCondition() {
 }
 
 ConditionalBoundsContext::ConditionalBoundsContext(
-    const PrimExpr& condition, std::unordered_map<const VarNode*, arith::IntSet>* dom_map,
-    bool is_true_branch)
-    : condition_(condition), dom_map_(dom_map), is_true_branch_(is_true_branch) {}
+    const PrimExpr& condition, std::unordered_map<const VarNode*, arith::IntSet>* relax_map,
+    std::unordered_map<const VarNode*, arith::IntSet>* hint_map, bool is_true_branch)
+    : condition_(condition),
+      relax_map_(relax_map),
+      hint_map_(hint_map),
+      is_true_branch_(is_true_branch) {}
 
 void ConditionalBoundsContext::EnterWithScope() {
   for (const auto& p : GetVarBoundsFromCondition()) {
     const auto* var = p.first.get();
-    auto it = dom_map_->find(var);
-    if (it != dom_map_->end()) {
-      origin_map_.emplace(var, it->second);
-      it->second = arith::Intersect({it->second, arith::IntSet::FromRange(p.second)});
+    arith::IntSet new_dom = arith::IntSet::FromRange(p.second);
+    auto relax_it = relax_map_->find(var);
+    if (relax_it != relax_map_->end()) {
+      // this is a bound for relaxed var
+      origin_map_.emplace(var, relax_it->second);
+      relax_it->second = arith::Intersect({relax_it->second, new_dom});
+    } else {
+      // this is a bound for free var
+      auto hint_it = hint_map_->find(var);
+      if (hint_it != hint_map_->end()) {
+        origin_map_.emplace(var, hint_it->second);
+        hint_it->second = arith::Intersect({hint_it->second, new_dom});
+      } else {
+        origin_map_.emplace(var, arith::IntSet::Nothing());
+        hint_map_->insert(hint_it, {var, new_dom});
+      }
     }
   }
 }
 
 void ConditionalBoundsContext::ExitWithScope() {
   for (const auto& p : origin_map_) {
-    (*dom_map_)[p.first] = p.second;
+    const auto* var = p.first;
+    auto relax_it = relax_map_->find(var);
+    if (relax_it != relax_map_->end()) {
+      // recover bound for relaxed var
+      relax_it->second = p.second;
+    } else {
+      // recover bound for free var
+      auto hint_it = hint_map_->find(var);
+      ICHECK(hint_it != hint_map_->end());
+      if (p.second.IsNothing()) {
+        hint_map_->erase(hint_it);
+      } else {
+        hint_it->second = p.second;
+      }
+    }
   }
 }
 

src/tir/transforms/ir_utils.h

@@ -231,21 +231,23 @@ Bool IsFromLegacyTESchedule(PrimFunc f);
  *\brief Context helper to update domain map within conditional scope.
  *
  * Assume the condition is `0 <= i && i < 9` and global domain of i is [0, 20], thus `bounds[i]` is
- *[0, 8]. Then `With<ConditionalBoundsContext> ctx(&dom_map, bounds, true)` step into scope where
- *dom_map[i] is [0, 8] and `With<ConditionalBoundsContext> ctx(&dom_map, bounds, false)` step into
- *scope where dom_map[i] is [9, 20]
+ * [0, 8]. Then `With<ConditionalBoundsContext> ctx(condition, &relax_map, &hint_map, true)` step
+ *into scope where dom_map[i] is [0, 8] and `With<ConditionalBoundsContext> ctx(condition,
+ *&relax_map, &hint_map, false)` step into scope where dom_map[i] is [9, 20]
  */
 class ConditionalBoundsContext {
  private:
   friend class With<ConditionalBoundsContext>;
   /*!
    * \brief Construct a condition bounds context.
    * \param condition The condition holds on true branch.
-   * \param dom_map The global domain map to be updated.
+   * \param relax_map The domain map for relaxed vars to update.
+   * \param hint_map The domain map for free vars to update.
    * \param is_true_branch Whether step into the branch where condition bounds holds.
    */
   ConditionalBoundsContext(const PrimExpr& condition,
-                           std::unordered_map<const VarNode*, arith::IntSet>* dom_map,
+                           std::unordered_map<const VarNode*, arith::IntSet>* relax_map,
+                           std::unordered_map<const VarNode*, arith::IntSet>* hint_map,
                            bool is_true_branch);
   void EnterWithScope();
   void ExitWithScope();
@@ -255,8 +257,10 @@ class ConditionalBoundsContext {
 
   /*! \brief the condition holds on true branch. */
   const PrimExpr& condition_;
-  /*! \brief global domain map to updated */
-  std::unordered_map<const VarNode*, arith::IntSet>* dom_map_;
+  /*! \brief domain map for relaxed vars to update */
+  std::unordered_map<const VarNode*, arith::IntSet>* relax_map_;
+  /*! \brief domain map for free vars to update */
+  std::unordered_map<const VarNode*, arith::IntSet>* hint_map_;
   /*! \brief whether is on true branch */
   bool is_true_branch_;
   /*! \brief used to record and restore original var bounds */

tests/python/unittest/test_tir_analysis_get_block_access_region.py

@@ -130,6 +130,41 @@ def access_in_branch_func() -> None:
                 B[i] = A[i - 1]
 
 
+@T.prim_func
+def access_of_padding_pattern() -> None:
+    X = T.alloc_buffer([28, 28])
+    X_pad = T.alloc_buffer([32, 32])
+    Y = T.alloc_buffer([28, 28])
+    for i, j in T.grid(32, 32):
+        with T.block("padding"):
+            vi, vj = T.axis.remap("SS", [i, j])
+            T.reads(
+                [
+                    X[
+                        T.max(vi - 2, 0) : T.min(vi - 2, 27) + 1,
+                        T.max(vj - 2, 0) : T.min(vj - 2, 27) + 1,
+                    ]
+                ]
+            )
+            T.writes([X_pad[vi, vj]])
+            X_pad[vi, vj] = T.if_then_else(
+                2 <= vi and vi < 30 and 2 <= vj and vj < 30, X[vi - 2, vj - 2], 0.0, dtype="float32"
+            )
+        with T.block("padding_reverse"):
+            vi, vj = T.axis.remap("SS", [i, j])
+            T.reads([X_pad[T.max(vi, 2) : T.min(vi, 29) + 1, T.max(vj, 2) : T.min(vj, 29) + 1]])
+            T.writes(
+                [
+                    Y[
+                        T.max(vi - 2, 0) : T.min(vi - 2, 27) + 1,
+                        T.max(vj - 2, 0) : T.min(vj - 2, 27) + 1,
+                    ]
+                ]
+            )
+            if 2 <= vi and vi < 30 and 2 <= vj and vj < 30:
+                Y[vi - 2, vj - 2] = X_pad[vi, vj]
+
+
 def test_block_access_region_detector():
     block = func.body.block.body.block
     alloc_buffers = func.body.block.alloc_buffers
@@ -220,10 +255,41 @@ def test_access_in_branch_func():
     tvm.ir.assert_structural_equal(ret0[1], ret1[1])
 
 
+def test_access_of_padding_pattern():
+    s = tvm.tir.schedule.Schedule(access_of_padding_pattern)
+    alloc_buffers = s.get_sref(s.get_block("root")).stmt.alloc_buffers
+    buffer_var_map = {buf.data: buf for buf in alloc_buffers}
+
+    def do_compare_buffer_region(region, expect):
+        assert region.buffer == expect.buffer
+        analyzer = tvm.arith.Analyzer()
+        for k, rng in enumerate(region.region):
+            tvm.ir.assert_structural_equal(
+                analyzer.simplify(rng.min), analyzer.simplify(expect.region[k].min)
+            )
+            tvm.ir.assert_structural_equal(
+                analyzer.simplify(rng.extent), analyzer.simplify(expect.region[k].extent)
+            )
+
+    def do_check_block(block_name):
+        block = s.get_sref(s.get_block(block_name)).stmt
+        expect_reads = block.reads
+        expect_writes = block.writes
+        ret = tir.analysis.get_block_access_region(block, buffer_var_map)
+        for i, read in enumerate(ret[0]):
+            do_compare_buffer_region(read, expect_reads[i])
+        for i, write in enumerate(ret[1]):
+            do_compare_buffer_region(write, expect_writes[i])
+
+    do_check_block("padding")
+    do_check_block("padding_reverse")
+
+
 if __name__ == "__main__":
     test_block_access_region_detector()
     test_opaque_block()
     test_opaque_access()
     test_match_buffer()
     test_access_in_if_then_else_func()
     test_access_in_branch_func()
+    test_access_of_padding_pattern()

tests/python/unittest/test_tir_transform_compact_buffer_region.py

@@ -24,6 +24,7 @@ def _check(original, transformed):
     mod = tvm.IRModule.from_expr(func)
     mod = tvm.tir.transform.CompactBufferAllocation()(mod)
     mod = tvm.tir.transform.Simplify()(mod)
+    transformed = tvm.tir.transform.Simplify()(tvm.IRModule.from_expr(transformed))["main"]
     tvm.ir.assert_structural_equal(mod["main"], transformed)