Revert "Cleanup trivial reduction workarounds (#2006)"

This reverts commit bca20c1.

Author: zasdfgbnm

torch/csrc/jit/codegen/cuda/inlining.cpp

@@ -153,25 +153,29 @@ size_t MaxPosCalculator::getMaxPosAll(
   return max_pos;
 }
 
-void inlineMost() {
-  inlineMost(ir_utils::allTvs(FusionGuard::getCurFusion()));
+void inlineMost(const std::unordered_set<IterDomain*>& uninlinable_ids) {
+  inlineMost(ir_utils::allTvs(FusionGuard::getCurFusion()), uninlinable_ids);
 }
 
-void inlineMost(const std::vector<TensorView*>& tvs) {
+void inlineMost(
+    const std::vector<TensorView*>& tvs,
+    const std::unordered_set<IterDomain*>& uninlinable_ids) {
   if (tvs.empty()) {
     return;
   }
-  MaxPosCalculator calc;
+  MaxPosCalculator calc(uninlinable_ids);
   for (auto tv : tvs) {
     tv->inlineAt(-1, true, &calc);
   }
 }
 
-void inlineMost(const std::unordered_set<TensorView*>& tvs) {
+void inlineMost(
+    const std::unordered_set<TensorView*>& tvs,
+    const std::unordered_set<IterDomain*>& uninlinable_ids) {
   if (tvs.empty()) {
     return;
   }
-  MaxPosCalculator calc;
+  MaxPosCalculator calc(uninlinable_ids);
   for (auto tv : tvs) {
     tv->inlineAt(-1, true, &calc);
   }
@@ -272,9 +276,10 @@ std::unordered_map<TensorView*, size_t> getPositionsMappedTo(
 void inlineAllAt(
     TensorView* reference_tv,
     int64_t reference_pos,
-    bool best_effort) {
+    bool best_effort,
+    const std::unordered_set<IterDomain*>& uninlinable_ids) {
   auto mapped_positions = getPositionsMappedTo(reference_tv, reference_pos);
-  MaxPosCalculator calc;
+  MaxPosCalculator calc(uninlinable_ids);
   for (auto pair : mapped_positions) {
     pair.first->inlineAt(pair.second, best_effort, &calc);
   }
@@ -284,9 +289,10 @@ void inlineSelectedAt(
     const std::unordered_set<TensorView*>& selected,
     TensorView* reference_tv,
     int64_t reference_pos,
-    bool best_effort) {
+    bool best_effort,
+    const std::unordered_set<IterDomain*>& uninlinable_ids) {
   auto mapped_positions = getPositionsMappedTo(reference_tv, reference_pos);
-  MaxPosCalculator calc;
+  MaxPosCalculator calc(uninlinable_ids);
   for (auto pair : mapped_positions) {
     if (selected.count(pair.first) > 0) {
       pair.first->inlineAt(pair.second, best_effort, &calc);

torch/csrc/jit/codegen/cuda/inlining.h

@@ -64,28 +64,35 @@ class MaxPosCalculator {
 
 // Inline to the right most allowed position for all tensors in the current
 // fusion.
-TORCH_CUDA_CU_API void inlineMost();
+TORCH_CUDA_CU_API void inlineMost(
+    const std::unordered_set<IterDomain*>& uninlinable_ids = {});
 // Inline to the right most allowed position for the selected tensors in the
 // current fusion.
-TORCH_CUDA_CU_API void inlineMost(const std::vector<TensorView*>& tvs);
+TORCH_CUDA_CU_API void inlineMost(
+    const std::vector<TensorView*>& tvs,
+    const std::unordered_set<IterDomain*>& uninlinable_ids = {});
 // Inline to the right most allowed position for the selected tensors in the
 // current fusion.
-TORCH_CUDA_CU_API void inlineMost(const std::unordered_set<TensorView*>& tvs);
+TORCH_CUDA_CU_API void inlineMost(
+    const std::unordered_set<TensorView*>& tvs,
+    const std::unordered_set<IterDomain*>& uninlinable_ids = {});
 
 // Inline to the position corresponding to the reference position in the
 // reference tensor for all tensors in the current fusion.
 TORCH_CUDA_CU_API void inlineAllAt(
     TensorView* reference_tv,
     int64_t reference_pos,
-    bool best_effort = false);
+    bool best_effort = false,
+    const std::unordered_set<IterDomain*>& uninlinable_ids = {});
 
 // Inline to the position corresponding to the reference position in the
 // reference tensor for selected tensors in the current fusion.
 TORCH_CUDA_CU_API void inlineSelectedAt(
     const std::unordered_set<TensorView*>& selected,
     TensorView* reference_tv,
     int64_t reference_pos,
-    bool best_effort = false);
+    bool best_effort = false,
+    const std::unordered_set<IterDomain*>& uninlinable_ids = {});
 
 } // namespace cuda
 } // namespace fuser

torch/csrc/jit/codegen/cuda/ir_nodes.cpp

@@ -1597,43 +1597,6 @@ std::vector<IterDomain*> IterDomain::clone(
   return cloned_domains;
 }
 
-IterType inferIterType(IterDomain* i1, IterDomain* i2) {
-  // The itertype inference is a pattern matching of the rules below:
-  //
-  //   X + X = X
-  //   trivial reduction + X = X
-  //   X + trivial reduction = X
-  //   broadcasting + X = X
-  //   X + broadcasting = X
-  //   fail
-  //
-  // The rules are proceeded one by one in order. For each rule, we test if the
-  // given (outer, inner) matches the pattern. If it does, then we stop
-  // procceeding and get a result. If we have reached the end without finding
-  // any matched pattern, then it is a mistake and should be reported.
-  //
-  // Note that based on the above rule:
-  //   broadcasting + (non-trivial) reduction = reduction
-  //   broadcasting + trivial reduction = broadcasting
-  if (i1->getIterType() == i2->getIterType()) {
-    return i1->getIterType();
-  }
-  if (i1->isTrivialReduction()) {
-    return i2->getIterType();
-  }
-  if (i2->isTrivialReduction()) {
-    return i1->getIterType();
-  }
-  if (i1->isBroadcast()) {
-    return i2->getIterType();
-  }
-  if (i2->isBroadcast()) {
-    return i1->getIterType();
-  }
-  TORCH_CHECK(
-      false, "Merging IterDomains requires that their iteration types match.");
-}
-
 // Merging does not propagate the start and stop values of the input
 // domains to the merged output domain. The actual range of the
 // domains is enforced by predicates. Note that since only root
@@ -1643,10 +1606,48 @@ IterDomain* IterDomain::merge(IterDomain* outer, IterDomain* inner) {
   TORCH_CHECK(
       !outer->extent()->isZeroInt() && !inner->extent()->isZeroInt(),
       "Merging IterDomains with ending values that are 0 is not supported at this time.");
+  TORCH_CHECK(
+      outer->isReduction() == inner->isReduction() ||
+          (!outer->isReduction() && inner->isTrivialReduction()) ||
+          (outer->isTrivialReduction() && !inner->isReduction()),
+      "Merging IterDomains requires that their iteration types match.");
+  TORCH_CHECK(
+      (outer->isGather() && inner->isGather()) ||
+          (!outer->isGather() && !inner->isGather()),
+      "Merging gather and non-gather domains is not supported.");
+
+  TORCH_CHECK(
+      !outer->isStride() && !inner->isStride(),
+      "No support for merging stride domains");
 
   Val* merged_id_size = mul(outer->extent(), inner->extent());
 
-  IterType itype = inferIterType(outer, inner);
+  IterType itype = outer->getIterType();
+
+  if (outer->isBroadcast() && inner->isBroadcast()) {
+    itype = IterType::Broadcast;
+  }
+
+  if ((outer->isBroadcast() || inner->isBroadcast()) &&
+      (outer->getIterType() == IterType::Iteration ||
+       inner->getIterType() == IterType::Iteration)) {
+    itype = IterType::Iteration;
+  }
+
+  // Merging trivial reduction with iter domain, that's fine, just make it an
+  // iter domain.
+  if ((outer->isTrivialReduction() || inner->isTrivialReduction()) &&
+      (outer->getIterType() == IterType::Iteration ||
+       inner->getIterType() == IterType::Iteration)) {
+    itype = IterType::Iteration;
+  }
+
+  // Merging trivial reduction with broadcasting, that's fine, just make it a
+  // broadcasting.
+  if ((outer->isTrivialReduction() || inner->isTrivialReduction()) &&
+      (outer->isBroadcast() || inner->isBroadcast())) {
+    itype = IterType::Broadcast;
+  }
 
   Val* expanded_extent = nullptr;
   if (outer->hasExpandedExtent() || inner->hasExpandedExtent()) {

torch/csrc/jit/codegen/cuda/scheduler/reduction_utils.cpp

@@ -330,8 +330,13 @@ void multiReductionInliner(
     }
   }
 
+  // Find iter domains that are mapped to a trivial reduction, these should
+  // never be inlined.
+  std::unordered_set<IterDomain*> mapped_to_trivial_reduction =
+      scheduler_utils::getTrivialReductionMap(fusion);
+
   // Inline the schedule
-  inlineMost();
+  inlineMost(mapped_to_trivial_reduction);
 }
 
 namespace {

torch/csrc/jit/codegen/cuda/scheduler/utils.cpp

@@ -21,20 +21,26 @@ namespace scheduler_utils {
 
 // Returns number of "valid" dimensions. e.g. if tv has
 // [I1, R2, I3, I4, R3{1}]
-// resulting domain should be:
-// [I1, I3*I4, R2*R3{1}] with return value 3
+// where R3{1} is in dont_merge, resulting domain should be:
+// [I1, I3*I4, R2, R3{1}] with return value 3
 //
 // if tv has
 // [R1, I2, R3, I4, R4, R5{1}, R6{1}]
-// resulting domain should be:
-// [I2*I4, R1*R3, R4*R5{1}*R6{1}]
+//  where R5{1} and R6{1} are in dont_merge, resulting domain should be:
+// [I2*I4, R1*R3, R4, R5{1}, R6{1}]
 // with return value 3
-size_t merge_3d(TensorView* tv) {
+size_t merge_3d(
+    TensorView* tv,
+    const std::unordered_set<IterDomain*>& dont_merge) {
   bool active_is_reduction = false;
   bool first_dim = true;
   int prev_i = -1;
 
   for (int i = static_cast<int>(tv->nDims()) - 1; i >= 0; i--) {
+    if (dont_merge.count(tv->axis(i))) {
+      continue;
+    }
+
     if (first_dim) {
       active_is_reduction = tv->axis(i)->isReduction();
       prev_i = i;
@@ -61,6 +67,10 @@ size_t merge_3d(TensorView* tv) {
 
   for (int i = static_cast<int>(tv->nDims()) - 2; i >= 0; i--) {
     auto id = tv->axis(i);
+    if (dont_merge.count(id)) {
+      continue;
+    }
+
     if (first_dim) {
       active_is_reduction = id->isReduction();
       prev_i = i;
@@ -86,6 +96,10 @@ size_t merge_3d(TensorView* tv) {
   prev_i = -1;
 
   for (int i = static_cast<int>(tv->nDims()) - 3; i >= 0; i--) {
+    if (dont_merge.count(tv->axis(i))) {
+      continue;
+    }
+
     if (first_dim) {
       active_is_reduction = tv->axis(i)->isReduction();
       prev_i = i;
@@ -100,7 +114,7 @@ size_t merge_3d(TensorView* tv) {
   if (prev_i == -1) {
     // Two dimensional, put merged dimensions first
     tv->reorder({{-1, 0}, {-2, 1}});
-    // [outer, inner]
+    // [outer, inner, dont_merge...]
     if (tv->axis(0)->isReduction()) {
       // put reductions as second axis
       tv->reorder({{0, 1}, {1, 0}});
@@ -181,11 +195,13 @@ c10::optional<size_t> mergeDims(
   return left;
 }
 
-size_t mergeReduction(TensorView* tv) {
+size_t mergeReduction(
+    TensorView* tv,
+    const std::unordered_set<IterDomain*>& dont_merge) {
   int prev_i = -1;
   size_t num_merged = 0;
   for (int i = static_cast<int>(tv->nDims()) - 1; i >= 0; i--) {
-    if (!tv->axis(i)->isReduction()) {
+    if (!tv->axis(i)->isReduction() || dont_merge.count(tv->axis(i))) {
       continue;
     }
     if (prev_i == -1) {
@@ -203,14 +219,16 @@ size_t mergeReduction(TensorView* tv) {
   return prev_i == -1 ? 0 : num_merged + 1;
 }
 
-size_t mergeNonReduction(TensorView* tv) {
+size_t mergeNonReduction(
+    TensorView* tv,
+    const std::unordered_set<IterDomain*>& dont_merge) {
   int prev_i = -1;
   size_t num_merged = 0;
   if (tv->nDims() == 0) {
     return 0;
   }
   for (int i = static_cast<int>(tv->nDims()) - 1; i >= 0; i--) {
-    if (tv->axis(i)->isReduction()) {
+    if (tv->axis(i)->isReduction() || dont_merge.count(tv->axis(i))) {
       continue;
     }
     if (prev_i == -1) {
@@ -887,21 +905,63 @@ PersistentBufferSizeReturn persistentBufferSize(
   return persistent_buffer_size;
 }
 
+std::unordered_set<IterDomain*> getTrivialReductionMap(Fusion* fusion) {
+  auto all_tvs = ir_utils::allTvs(fusion);
+  std::unordered_set<IterDomain*> mapped_to_trivial_reduction;
+  for (auto tv : all_tvs) {
+    // root domain vs domain shouldn't matter as at this point we shouldn't have
+    // any transformations.
+    for (auto id : tv->getRootDomain()) {
+      if (id->isTrivialReduction()) {
+        mapped_to_trivial_reduction.emplace(id);
+      }
+    }
+  }
+
+  if (!mapped_to_trivial_reduction.empty()) {
+    // Use the loop map as that is the most permissive
+    auto ca_map = ComputeAtMap(fusion);
+    // Make a copy we need to check mappings of all
+    auto trivial_ids = mapped_to_trivial_reduction;
+    for (auto tv : all_tvs) {
+      for (auto id : tv->getRootDomain()) {
+        if (!id->extent()->isOneInt()) {
+          continue;
+        }
+        if (std::any_of(
+                trivial_ids.begin(),
+                trivial_ids.end(),
+                [&ca_map, &id](IterDomain* trivial_id) {
+                  return ca_map.areMapped(
+                      id, trivial_id, IdMappingMode::PERMISSIVE);
+                })) {
+          mapped_to_trivial_reduction.emplace(id);
+        }
+      }
+    }
+  }
+  return mapped_to_trivial_reduction;
+}
+
 std::pair<bool, bool> canonicalDimReduction(
     Fusion* fusion,
     TensorView* tv,
     bool schedule_3D) {
+  std::unordered_set<IterDomain*> mapped_to_trivial_reduction =
+      getTrivialReductionMap(fusion);
+
   TORCH_INTERNAL_ASSERT(tv != nullptr);
 
   if (!schedule_3D) {
     // We coalesce all reduction axes to the right;
-    bool has_red_axis = mergeReduction(tv) > 0;
+    bool has_red_axis = mergeReduction(tv, mapped_to_trivial_reduction) > 0;
 
-    bool has_iter_axis = mergeNonReduction(tv) > 0;
+    bool has_iter_axis = mergeNonReduction(tv, mapped_to_trivial_reduction) > 0;
     return {has_iter_axis, has_red_axis};
   } else {
     TORCH_INTERNAL_ASSERT(
-        merge_3d(tv) == 3, "Tried 3D merge, but result is not 3D.");
+        merge_3d(tv, mapped_to_trivial_reduction) == 3,
+        "Tried 3D merge, but result is not 3D.");
     return {true, true};
   }
 }

torch/csrc/jit/codegen/cuda/scheduler/utils.h

@@ -78,12 +78,16 @@ TORCH_CUDA_CU_API inline c10::optional<size_t> mergeDims(
 }
 
 // Merge all reduction to the right side and returns total number of
-// reduction axes.
-size_t mergeReduction(TensorView* tv);
+// reduction axes. Don't merge is typically used for trivial reductions.
+size_t mergeReduction(
+    TensorView* tv,
+    const std::unordered_set<IterDomain*>& dont_merge = {});
 
 // merge all non-reduction axes to the left side and returns total number of
-// iteration axes.
-size_t mergeNonReduction(TensorView* tv);
+// iteration axes. Don't merge is typically used for trivial reductions.
+size_t mergeNonReduction(
+    TensorView* tv,
+    const std::unordered_set<IterDomain*>& dont_merge = {});
 
 // Propagate the parallelization from the selected dimensions of the reference
 // tensor to their corresponding dimensions in all selected tensors in the DAG.