[MetaSchedule] Support padding for irregular shapes for CUDA tensor core

python/tvm/tir/schedule/analysis.py

@@ -68,7 +68,7 @@ class TensorizeInfo(Object):
 
 
 def get_tensorize_loop_mapping(
-    sch: Schedule, block: BlockRV, desc_func: PrimFunc
+    sch: Schedule, block: BlockRV, desc_func: PrimFunc, allow_padding: bool = False
 ) -> Optional[TensorizeInfo]:
     """Establish a mapping between loops in a target block and an intrinsic description
 
@@ -80,13 +80,14 @@ def get_tensorize_loop_mapping(
         The target block to match against
     desc_func : PrimFunc
         The prim func describing the computation to be tensorized
-
+    allow_padding : bool
+        Whether to allow padding the block iters to match the intrinsic description
     Returns
     -------
     tensorize_info : Optional[TensorizeInfo]
         TensorizeInfo structure if a valid mapping is found, None otherwise
     """
-    return _ffi_api.GetTensorizeLoopMapping(sch, block, desc_func)  # type: ignore
+    return _ffi_api.GetTensorizeLoopMapping(sch, block, desc_func, allow_padding)  # type: ignore
 
 
 @tvm._ffi.register_object("tir.schedule.AutoTensorizeMappingInfo")

python/tvm/tir/schedule/transform.py

@@ -21,7 +21,9 @@
 from . import _ffi_api
 
 
-def tile_with_tensor_intrin(sch: Schedule, block: BlockRV, intrin_name: str) -> Optional[LoopRV]:
+def tile_with_tensor_intrin(
+    sch: Schedule, block: BlockRV, intrin_name: str, allow_padding: bool = False
+) -> Optional[LoopRV]:
     """Tile a subset of loops in the block according to the given tensor intrinsic.
 
     Parameters
@@ -32,11 +34,13 @@ def tile_with_tensor_intrin(sch: Schedule, block: BlockRV, intrin_name: str) ->
         The block whose subset of loops will be tiled
     intrin_name : str
         The name of a tensor intrinsic, must be registerd via TensorIntrin.register(...) beforehand
+    allow_padding : bool
+        Whether to allow padding when tiling
 
     Returns
     -------
     tiled_loop_rv : Optional[LoopRV]
         LoopRV corresponding to the outermost loop of a block tiled according to the given intrin
         NullOpt if no valid loop mapping is found
     """
-    return _ffi_api.TileWithTensorIntrin(sch, block, intrin_name)  # type: ignore
+    return _ffi_api.TileWithTensorIntrin(sch, block, intrin_name, allow_padding)  # type: ignore

src/meta_schedule/schedule_rule/multi_level_tiling_tensor_core.cc

@@ -515,7 +515,8 @@ Optional<LoopRV> MultiLevelTilingTensorCoreNode::TransformWithTensorIntrin(
   state->sch->TransformBlockLayout(state->tensor_core_reindex_B, index_map);
   state->sch->TransformBlockLayout(state->block_rv, index_map);
 
-  return tir::TileWithTensorIntrin(state->sch, state->block_rv, intrin_name);
+  return tir::TileWithTensorIntrin(state->sch, state->block_rv, intrin_name,
+                                   /*allow_padding=*/true);
 }
 
 inline std::vector<State> MultiLevelTilingTensorCoreNode::TransformForTensorization(

src/tir/schedule/analysis.h

@@ -731,10 +731,15 @@ class TensorizeInfoNode : public Object {
   Map<tir::StmtSRef, tir::For> loop_map;
   /*! \brief Maps loops in an intrinsic description to its index, outer to inner */
   Map<tir::For, Integer> desc_loop_indexer;
+  /*! \brief Optional padded extents of the block iters when padding is needed to match the
+   * intrinsic description
+   */
+  Optional<Array<Integer>> block_iter_paddings;
 
   void VisitAttrs(AttrVisitor* v) {
     v->Visit("loop_map", &loop_map);
     v->Visit("desc_loop_indexer", &desc_loop_indexer);
+    v->Visit("block_iter_paddings", &block_iter_paddings);
   }
 
   static constexpr const char* _type_key = "tir.schedule.TensorizeInfo";
@@ -751,11 +756,12 @@ class TensorizeInfo : public ObjectRef {
  * \param self The schedule state to be tensorized
  * \param block_sref The target block to match against
  * \param desc_func The prim func describing the computation to be tensorized
+ * \param allow_padding Whether to allow padding the block iters to match the intrinsic description
  * \return TensorizeInfo structure if a valid mapping is found, NullOpt otherwise
  */
 Optional<TensorizeInfo> GetTensorizeLoopMapping(const tir::ScheduleState& self,
                                                 const tir::StmtSRef& block_sref,
-                                                const tir::PrimFunc& desc_func);
+                                                const tir::PrimFunc& desc_func, bool allow_padding);
 
 /*！\brief Necessary information used to perform transformations for tensorization */
 class AutoTensorizeMappingInfoNode : public Object {

src/tir/schedule/analysis/analysis.cc

@@ -1699,7 +1699,8 @@ TensorIntrinDescInfo ExtractTensorIntrinDescInfo(arith::Analyzer* analyzer,
 
 Optional<TensorizeInfo> GetTensorizeLoopMapping(const tir::ScheduleState& self,
                                                 const tir::StmtSRef& block_sref,
-                                                const tir::PrimFunc& desc_func) {
+                                                const tir::PrimFunc& desc_func,
+                                                bool allow_padding) {
   arith::Analyzer analyzer;
   const tir::BlockRealize& block = tir::GetBlockRealize(self, block_sref);
   // Step 1. Analyze desc_func, extract its block, loops and loop vars
@@ -1732,6 +1733,8 @@ Optional<TensorizeInfo> GetTensorizeLoopMapping(const tir::ScheduleState& self,
   const int n_desc_vars = desc_block->iter_values.size();
   const int offset = n_block_vars - n_desc_vars;
 
+  std::unordered_map<int, int> block_index_to_padding;  // padding of each block iter if necessary
+
   if (offset < 0) {
     return NullOpt;
   }
@@ -1782,10 +1785,11 @@ Optional<TensorizeInfo> GetTensorizeLoopMapping(const tir::ScheduleState& self,
 
     // Step 3.2. Find the corresponding iter_value of the target block with a matching iterator type
     PrimExpr block_bind;
-    for (int i = next_block_ind; i >= 0; --i) {
-      if (iter_types_block[i] == iter_type_desc) {
-        next_block_ind = i - 1;
-        block_bind = block->iter_values[i];
+    int current_block_ind = next_block_ind;
+    for (; current_block_ind >= 0; --current_block_ind) {
+      if (iter_types_block[current_block_ind] == iter_type_desc) {
+        next_block_ind = current_block_ind - 1;
+        block_bind = block->iter_values[current_block_ind];
         break;
       }
     }
@@ -1802,15 +1806,30 @@ Optional<TensorizeInfo> GetTensorizeLoopMapping(const tir::ScheduleState& self,
 
       PrimExpr residual = analyzer.Simplify(block_bind - block_loops[i]->loop_var);
       if (UsesVar(residual,
-                  [&block_loop_vars](const VarNode* var) { return block_loop_vars.count(var); }))
+                  [&block_loop_vars](const VarNode* var) { return block_loop_vars.count(var); })) {
         continue;
+      }
+      // padding is allowed only when the block has trivial bindings
+      if (allow_padding && !is_zero(residual)) {
+        allow_padding = false;
+      }
 
       const IntImmNode* int_block_extent = block_loops[i]->extent.as<IntImmNode>();
 
       // Check divisibility
-      if (!int_block_extent || int_block_extent->value % int_desc_extent->value != 0) {
+      if (!int_block_extent) {
         return NullOpt;
       }
+      int64_t remainder = int_block_extent->value % int_desc_extent->value;
+      if (remainder != 0) {
+        if (allow_padding) {
+          // If the block loop is not divisible by the desc loop, we pad the block loop to make it
+          // divisible if padding is allowed.
+          block_index_to_padding[current_block_ind] = int_desc_extent->value - remainder;
+        } else {
+          return NullOpt;
+        }
+      }
 
       ret->loop_map.Set(block_loop_sref, GetRef<tir::For>(desc_loop));
       break;
@@ -1820,13 +1839,29 @@ Optional<TensorizeInfo> GetTensorizeLoopMapping(const tir::ScheduleState& self,
   for (int i = 0, n = desc_loops.size(); i < n; ++i) {
     ret->desc_loop_indexer.Set(GetRef<tir::For>(desc_loops[i]), Integer(i));
   }
+  if (!block_index_to_padding.empty()) {
+    if (!allow_padding) {
+      return NullOpt;
+    }
+    Array<Integer> paddings;
+    for (int i = 0, n = block->block->iter_vars.size(); i < n; ++i) {
+      const IterVar& iter_var = block->block->iter_vars[i];
+      if (auto it = block_index_to_padding.find(i); it != block_index_to_padding.end()) {
+        paddings.push_back(IntImm(iter_var->var.dtype(), it->second));
+      } else {
+        paddings.push_back(IntImm(iter_var->var.dtype(), 0));
+      }
+    }
+    ret->block_iter_paddings = std::move(paddings);
+  }
+
   return TensorizeInfo(ret);
 }
 
 TVM_REGISTER_GLOBAL("tir.schedule.IsSpatialPrimFunc").set_body_typed(IsSpatialPrimFunc);
 TVM_REGISTER_GLOBAL("tir.schedule.GetTensorizeLoopMapping")
-    .set_body_typed([](Schedule sch, BlockRV block, PrimFunc desc_func) {
-      return GetTensorizeLoopMapping(sch->state(), sch->GetSRef(block), desc_func);
+    .set_body_typed([](Schedule sch, BlockRV block, PrimFunc desc_func, bool allow_padding) {
+      return GetTensorizeLoopMapping(sch->state(), sch->GetSRef(block), desc_func, allow_padding);
     });
 
 /******** Auto Tensorization ********/

src/tir/schedule/transform.cc

@@ -288,11 +288,15 @@ void LeafBlockRemovalPlan(const ScheduleState& self, const StmtSRef& leaf_block_
 }
 
 Optional<LoopRV> TileWithTensorIntrin(const tir::Schedule& sch, const tir::BlockRV& block_rv,
-                                      const String& intrin_name) {
-  Optional<tir::TensorizeInfo> opt_tensorize_info = GetTensorizeLoopMapping(
-      sch->state(), sch->GetSRef(block_rv), tir::TensorIntrin::Get(intrin_name)->desc);
+                                      const String& intrin_name, bool allow_padding) {
+  Optional<tir::TensorizeInfo> opt_tensorize_info =
+      GetTensorizeLoopMapping(sch->state(), sch->GetSRef(block_rv),
+                              tir::TensorIntrin::Get(intrin_name)->desc, allow_padding);
   if (!opt_tensorize_info) return NullOpt;
   const tir::TensorizeInfoNode* info = opt_tensorize_info.value().get();
+  if (info->block_iter_paddings.defined()) {
+    sch->PadEinsum(block_rv, info->block_iter_paddings.value());
+  }
   // Construct a mapping from tir loops back to LoopRVs
   Map<tir::StmtSRef, LoopRV> loop2rv;
   {

src/tir/schedule/transform.h

@@ -193,11 +193,12 @@ void LeafBlockRemovalPlan(const ScheduleState& self, const StmtSRef& leaf_block_
  * \param block_rv The block whose subset of loops will be tiled
  * \param intrin_name The name of a tensor intrinsic, must be registerd via
  * TensorIntrin.register(...) beforehand
+ * \param allow_padding Whether to allow padding when tiling
  * \return LoopRV corresponding to the outermost loop of a
  * block tiled according to the given intrin, NullOpt if a valid loop mapping is not found
  */
 Optional<tir::LoopRV> TileWithTensorIntrin(const tir::Schedule& sch, const tir::BlockRV& block_rv,
-                                           const String& intrin_name);
+                                           const String& intrin_name, bool allow_padding = false);
 
 /******** Block mutation ********/