[mlir][Linalg][Transform] Add support to let `transform.structured.pack_greedily` pad to the next multiple of a static constant

[nicolasvasilache]

Summary

This increase the flexibility of the transformation to allow mixed packing / padding specifications.

[nicolasvasilache]

Add negative tests

[ThomasRaoux]

Thanks!

mlir/include/mlir/Dialect/Linalg/TransformOps/LinalgTransformOps.td

 //===----------------------------------------------------------------------===//
 def PackGreedilyOp : Op<Transform_Dialect, "structured.pack_greedily", [
                         DeclareOpInterfaceMethods<TransformOpInterface>,
                         DeclareOpInterfaceMethods<MemoryEffectsOpInterface>]> {
   let description = [{
     Target a Linalg op and rewrite it into packed LinalgOp form by trying to
     infer whether a known suboperation is embedded
 
-    Different packing strategies are applied in order, when one applies
+    Different packing strategies are applied in order, when one applies 
     successfully, the transform returns:
       1. Matmul packing: Try to infer a matmul operation embedded in the target op.
          Specifically, this looks for 2 parallel dimensions that participate in
          an outer-product and 1 reduction dimension.
          These dimensions are referred as (m, n, k) to match canonical matmul
          terminology.
-         The packed sizes for (m, n, k) are specified by `matmul_packed_sizes`.
+         
+         The packed sizes for (m, n, k) are specified by `matmul_packed_sizes`
+         and the optional `matmul_padded_sizes_next_multiple_of`.
+         When an entry `matmul_packed_sizes[i]` is non-0, the corresponding 
+         dimension is packed by `matmul_packed_sizes[i]`.
+         Otherwise, the dimension is merely padded to the next multiple of
+         `matmul_padded_sizes_next_multiple_of[i]`.
+
+         `matmul_padded_sizes_next_multiple_of` is optional and is expected to
+         either be empty or of size `3`, matching the size of `matmul_packed_sizes`.
+         For each individual element of `matmul_packed_sizes` and 
+         `matmul_padded_sizes_next_multiple_of`, only one of them is allowed to
+         be non-zero.
+         
          The ordering of the packed dimensions (mm, nn, kk) is specified by the
          `matmul_inner_dims_order` attribute.
 
     Packing occurs as follows:
       1. Find the dimensions to pack according to the strategy.
       2. The target is converted to linalg.generic form.
       3. An interchange transform is applied to isolate the dimensions to pack as
          the most minor indexing dimensions of the linalg.generic. The most minor
          dimensions are themselves ordered according to `inner_dims_order`.
-      4. Packing is performed by `packed_sizes` and following `inner_dims_order`.
+      4. An elementwise traversal of `matmul_packed_sizes` and
+         `matmul_padded_sizes_next_multiple_of` is performed and for each 
+         dimension `d`, either pack to `matmul_packed_sizes[d]` or pad to the
+         `matmul_padded_sizes_next_multiple_of[d]`.
+      5. Packing/padding is performed by the amounts determined in step 4. and
+         following `inner_dims_order`.
 
     By normalizing the most minor dimensions to `inner_dims_order`, the transform
-    guarantees that packing immediates generates inner dimensions in a desirable
+    guarantees that packing immediately generates inner dimensions in a desirable
     layout.
 
     Outer dimension layout permutations are not controlled by this transform op
     at the moment and can be obtained by composing with the pack_transpose
     transformation.
 
     #### Return modes
 
     This operation ignores non-Linalg ops and drops them in the return.
     It returns the list of packed Linalg ops or the original op when all available
     packing strategies failed to apply.
   }];
 
   // TODO: Transform_ConcreteOpType<linalg::LinalgOp> needs interface.
   let arguments = (ins TransformHandleTypeInterface:$target,
                    Variadic<PDL_Operation>:$matmul_packed_sizes,
-                   DefaultValuedAttr<DenseI64ArrayAttr, "{}">
-                     :$static_matmul_packed_sizes,
-                   DefaultValuedAttr<DenseI64ArrayAttr, "{}">
-                     :$matmul_inner_dims_order);
+                   ConfinedAttr<DefaultValuedAttr<DenseI64ArrayAttr, "{}">,
+                                 [DenseArrayCount<3>]>:$static_matmul_packed_sizes,
+                   ConfinedAttr<DefaultValuedAttr<DenseI64ArrayAttr, "{}">,
+                                 [Attr<
+                                    Or<[DenseArrayCount<0>.predicate, 
+                                        DenseArrayCount<3>.predicate]>,
+                                        "with 0 or 3 elements"
+                                      >]>
+                                 :$matmul_padded_sizes_next_multiple_of,
+                   ConfinedAttr<DefaultValuedAttr<DenseI64ArrayAttr, "{}">,
+                                 [DenseArrayCount<3>]>:$matmul_inner_dims_order);
   let results = (outs Transform_ConcreteOpType<"linalg.generic">:$packed_op);
 
   let builders = [
     OpBuilder<(ins "Value":$target,
                    "ArrayRef<OpFoldResult>":$mixedMatmulPackedSizes,
+                   "ArrayRef<int64_t>":$matmulPaddededSizesNextMultipleOf,
                    CArg<"ArrayRef<int64_t>", "{}">:$matmulDimsInnerDimsOrder)>
   ];
 
   let assemblyFormat = [{
     $target
     oilist(
       `matmul_packed_sizes` `=` custom<DynamicIndexList>($matmul_packed_sizes,
                                                          $static_matmul_packed_sizes)
+      (`matmul_padded_sizes_next_multiple_of` `=` 
+        $matmul_padded_sizes_next_multiple_of^)?
       `matmul_inner_dims_order` `=` $matmul_inner_dims_order
     )
     attr-dict
     `:` functional-type($target, results)
   }];
   let hasVerifier = 1;
 
   let extraClassDeclaration = [{

mlir/lib/Dialect/Linalg/TransformOps/LinalgTransformOps.cpp

 #include "mlir/Dialect/SCF/Transforms/TileUsingInterface.h"
 #include "mlir/Dialect/Tensor/IR/Tensor.h"
 #include "mlir/Dialect/Tensor/Utils/Utils.h"
 #include "mlir/Dialect/Transform/IR/TransformDialect.h"
 #include "mlir/Dialect/Transform/IR/TransformInterfaces.h"
 #include "mlir/Dialect/Transform/IR/TransformTypes.h"
 #include "mlir/Dialect/Transform/Utils/Utils.h"
 #include "mlir/Dialect/Utils/IndexingUtils.h"
+#include "mlir/Dialect/Utils/StaticValueUtils.h"
 #include "mlir/Dialect/Vector/Transforms/LoweringPatterns.h"
 #include "mlir/IR/PatternMatch.h"
 #include "mlir/IR/TypeUtilities.h"
 #include "mlir/Interfaces/TilingInterface.h"
 #include "mlir/Support/LLVM.h"
 #include "mlir/Transforms/GreedyPatternRewriteDriver.h"
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/ScopeExit.h"

 //===---------------------------------------------------------------------===//
 
 LogicalResult transform::PackGreedilyOp::verify() {
   if (!isPermutationVector(getMatmulInnerDimsOrder())) {
     return emitOpError() << getMatmulInnerDimsOrderAttrName()
                          << " is not a valid permutation";
   }
   // TODO: relax to allow empty once we have another strategy than just matmul.
-  if (getMatmulInnerDimsOrder().size() != 3 ||
-      getMixedMatmulPackedSizes().size() != 3) {
-    return emitOpError() << " needs 3 entries for matmul_packed_sizes and "
-                         << getMatmulInnerDimsOrderAttrName()
-                         << " order for the matmul strategy";
+  if (!getMatmulPaddedSizesNextMultipleOf().empty()) {
+    for (auto [s, nmo] :
+         llvm::zip_equal(getMixedMatmulPackedSizes(),
+                         getMatmulPaddedSizesNextMultipleOf())) {
+      std::optional<int64_t> maybeStaticPackedSize = getConstantIntValue(s);
+      if (nmo != 0 &&
+          (!maybeStaticPackedSize.has_value() || *maybeStaticPackedSize != 0)) {
+        return emitOpError() << "at most one of the packed_size and the "
+                                "padded_sizes_next_multiple_of can be nonzero "
+                                "for the matmul strategy";
+      }
+    }
   }
   return success();
 }
 
 /// Pack a LinalgOp by greedily inferring matmul dimensions (m, n, k) where m
 /// and n are proper parallel dimensions and k is a proper reduction
 /// dimension. Packing occurs by rewriting the op as a linalg.generic and
 /// calling linalg::pack by `mnkPackedSizes`. The order of the packed
 /// dimensions is customizable: the `mnkOrder` is a permutation of {0, 1, 2}
 /// to reorder {m, n, k} into one of the 8 possible forms. The outer
 /// dimensions of the operands are not permuted at this time, this is left for
 /// future work.
 static FailureOr<PackResult>
 packMatmulGreedily(RewriterBase &rewriter, LinalgOp linalgOp,
                    ArrayRef<OpFoldResult> mnkPackedSizes,
+                   ArrayRef<int64_t> mnkPaddedSizesNextMultipleOf,
                    ArrayRef<int64_t> mnkOrder) {
   assert(mnkPackedSizes.size() == 3 && "unexpected num of packing sizes");
+  assert(mnkPaddedSizesNextMultipleOf.empty() ||
+         mnkPaddedSizesNextMultipleOf.size() == 3 &&
+             "num of packing sizes next multiple should be empty or of size 3");
   assert(mnkOrder.size() == 3 && "unexpected mnkOrder size");
   assert(isPermutationVector(mnkOrder) && "expected a permutation");
 
   int64_t numLoops = linalgOp.getNumLoops();
   if (numLoops <= 2) {
     return rewriter.notifyMatchFailure(
         linalgOp, "need 3+ loops to find a matmul to pack");
   }
 
   // Locally adjust the desired iterator position of mnk and packing sizes.
   int64_t numPackedDims = mnkPackedSizes.size();
   SmallVector<int64_t> mmnnkkPos(numPackedDims);
   for (int64_t i = 0, e = numPackedDims; i < e; ++i)
     mmnnkkPos[i] = numLoops - numPackedDims + mnkOrder[i];
-  SmallVector<OpFoldResult> packedSizes(mnkPackedSizes.size());
+  SmallVector<OpFoldResult> packedSizes(numPackedDims);
   for (int64_t i = 0, e = numPackedDims; i < e; ++i)
     packedSizes[mnkOrder[i]] = mnkPackedSizes[i];
+  SmallVector<int64_t> paddedSizesNextMultipleOf(numPackedDims);
+  for (int64_t i = 0, e = numPackedDims; i < e; ++i) {
+    paddedSizesNextMultipleOf[mnkOrder[i]] =
+        mnkPaddedSizesNextMultipleOf.empty() ? 0
+                                             : mnkPaddedSizesNextMultipleOf[i];
+  }
 
   // 1. Infer dims that are important for matmul.
   FailureOr<EmbeddedMatmulDimsCandidates> res = inferMatmulDims(linalgOp);
   if (failed(res)) {
     return rewriter.notifyMatchFailure(linalgOp,
                                        "couldn't infer matmul iterators");
   }
 
packMatmulGreedily(RewriterBase &rewriter, LinalgOp linalgOp,
   // If we wanted to change the packed order, we would reorder (k, m, n) to
   // something else above.
   //
   // Additional permutations of the outer dims of the operands (i.e.
   // leading_lhs, leading_rhs and leading_res) could follow by computing the
   // desired outerPerm for each operand.
   // This is left for future work.
 
-  // Add leading zeros to match numLoops.
+  // TODO: this creates too much IR, go use reifyResultShapes.
+  SmallVector<Range, 4> loopRanges =
+      cast<LinalgOp>(genericOp.getOperation())
+          .createLoopRanges(rewriter, genericOp.getLoc());
+
+  // Add leading zeros to match numLoops, we only pack the last 3 dimensions
+  // post interchange.
+  LLVM_DEBUG(llvm::interleaveComma(paddedSizesNextMultipleOf,
+                                   DBGS() << "paddedSizesNextMultipleOf: ");
+             DBGSNL(););
+  LLVM_DEBUG(llvm::interleaveComma(loopRanges, DBGS() << "loopRanges: ",
+                                   [](Range r) { llvm::dbgs() << r.size; });
+             DBGSNL(););
   SmallVector<OpFoldResult> adjustedPackedSizes(numLoops - packedSizes.size(),
                                                 rewriter.getIndexAttr(0));
-  llvm::append_range(adjustedPackedSizes, packedSizes);
+  for (int64_t i = 0, e = numPackedDims; i < e; ++i) {
+    if (paddedSizesNextMultipleOf[i] == 0) {
+      adjustedPackedSizes.push_back(packedSizes[i]);
+      continue;
+    }
+    AffineExpr d0, s0;
+    bindDims(rewriter.getContext(), d0);
+    bindSymbols(rewriter.getContext(), s0);
+    adjustedPackedSizes.push_back(makeComposedFoldedAffineApply(
+        rewriter, genericOp->getLoc(), d0.ceilDiv(s0) * s0,
+        {loopRanges[adjustedPackedSizes.size()].size,
+         rewriter.getIndexAttr(paddedSizesNextMultipleOf[i])}));
+  }
+  LLVM_DEBUG(llvm::interleaveComma(adjustedPackedSizes,
+                                   DBGS() << "adjustedPackedSizes: ");
+             DBGSNL(););
 
   // TODO: If we wanted to give the genericOp a name after packing, after
   // calling `pack` would be a good time.
   auto packingRes = linalg::pack(rewriter, genericOp, adjustedPackedSizes);
   assert(containsMostMinorMatmul(packingRes->packedLinalgOp) &&
          "failed to pack to a most minor matmul");
   return packingRes;
 }
for (Operation *op : targetOps) {
     // we set it before -> set it after.
     rewriter.setInsertionPointAfter(linalgOp);
     // Failing to pack greedily is perfectly fine.
     // In the future we will want to order packings according to some metric.
     FailureOr<PackResult> packResult = packMatmulGreedily(
         /*rewriter=*/rewriter,
         /*linalgOp=*/linalgOp,
         /*mnkPackedSizes=*/getMixedMatmulPackedSizes(),
+        /*mnkPaddedSizesNextMultipleOf=*/
+        getMatmulPaddedSizesNextMultipleOf(),
         /*mnkOrder=*/getMatmulInnerDimsOrder());
     if (succeeded(packResult)) {
       results.push_back(packResult->packedLinalgOp);
       continue;
     }
     results.push_back(linalgOp);
   }
   transformResults.set(getPackedOp().cast<OpResult>(), results);

mlir/test/Dialect/Linalg/transform-ops-invalid.mlir

 // -----
 
 transform.sequence failures(propagate) {
 ^bb0(%arg0: !pdl.operation):
   // expected-error@below {{expects all results type to be the same}}
   "transform.structured.multitile_sizes"(%arg0) { target_size = 3, divisor = 2, dimension = 0 }
       : (!pdl.operation) -> (!transform.param<i64>, !transform.param<i64>, !transform.param<i32>)
 }
+
+// -----
+
+transform.sequence failures(propagate) {
+^bb0(%arg0: !pdl.operation):
+  // expected-error@below {{not a valid permutation}}
+  transform.structured.pack_greedily %arg0
+      matmul_packed_sizes = [8, 0, 32] 
+      matmul_inner_dims_order = [1, 1, 0]
+    : (!pdl.operation) -> !transform.op<"linalg.generic">
+
+}
+
+// -----
+
+transform.sequence failures(propagate) {
+^bb0(%arg0: !pdl.operation):
+  // expected-error@below {{at most one of the packed_size and the padded_sizes_next_multiple_of can be nonzero}}
+  transform.structured.pack_greedily %arg0
+      matmul_packed_sizes = [1, 1, 1] 
+      matmul_padded_sizes_next_multiple_of = [1, 1, 1] 
+      matmul_inner_dims_order = [0, 1, 2]
+    : (!pdl.operation) -> !transform.op<"linalg.generic">
+
+}

mlir/test/Dialect/Linalg/transform-pack-greedily.mlir

 
 transform.sequence failures(propagate) {
 ^bb1(%module_op: !pdl.operation):
   %generic = transform.structured.match ops{["linalg.generic"]} in %module_op : (!pdl.operation) -> !transform.op<"linalg.generic">
   transform.structured.pack_greedily %generic
       matmul_packed_sizes = [8, 16, 32] matmul_inner_dims_order = [1, 2, 0]
     : (!transform.op<"linalg.generic">) -> !transform.op<"linalg.generic">
 }
+
+// -----
+
+!A_mk = tensor<1023x255xf32>
+!B_nk = tensor<127x255xf32>
+!C_nm = tensor<127x1023xf32>
+
+#mkn_accesses = [
+  affine_map<(m, n, k) -> (m, k)>,
+  affine_map<(m, n, k) -> (n, k)>,
+  affine_map<(m, n, k) -> (n, m)>
+]
+#mkn_trait = {
+  indexing_maps = #mkn_accesses,
+  iterator_types = ["parallel", "parallel", "reduction"]
+}
+
+// Normalized dims are:                     ( k,  m,  n)(kk, mm, nn)
+// CHECK-DAG: #[[$km_kkmm:.*]] = affine_map<(d0, d1, d2, d3, d4, d5) -> (d1, d0, d3, d4)>
+// CHECK-DAG: #[[$kn_kknn:.*]] = affine_map<(d0, d1, d2, d3, d4, d5) -> (d2, d0, d3, d5)>
+// CHECK-DAG: #[[$mn_mmnn:.*]] = affine_map<(d0, d1, d2, d3, d4, d5) -> (d2, d1, d4, d5)>
+
+// CHECK-LABEL: @matmul_mk_nk_nm(
+func.func @matmul_mk_nk_nm(%A : !A_mk, %B : !B_nk, %C : !C_nm) -> !C_nm {
+  //      CHECK: linalg.generic
+  // CHECK-SAME: indexing_maps = [#[[$mk_kkmm]], #[[$kn_kknn]], #[[$mn_mmnn]]]
+  // CHECK-SAME:   ["reduction", "parallel", "parallel", "reduction", "parallel", "parallel"]} 
+  // CHECK-SAME:   ins(%{{.*}} : tensor<128x8x32x8xf32>, tensor<1x8x32x130xf32>)
+  // CHECK-SAME:  outs(%{{.*}} : tensor<1x128x8x130xf32>)
+  %0 = linalg.generic #mkn_trait ins(%A, %B : !A_mk, !B_nk) outs(%C : !C_nm) {
+    ^bb0(%a: f32, %b: f32, %c: f32):
+      %d = arith.mulf %a, %b : f32
+      %e = arith.addf %c, %d : f32
+      linalg.yield %e : f32
+  } -> !C_nm
+  return %0 : !C_nm
+}
+
+transform.sequence failures(propagate) {
+^bb1(%module_op: !pdl.operation):
+  %generic = transform.structured.match ops{["linalg.generic"]} in %module_op : (!pdl.operation) -> !transform.op<"linalg.generic">
+  transform.structured.pack_greedily %generic
+      // In this spec, the "k" dimension is not packed but rather padded to the
+      // next multiple of 10 (i.e. 130).
+      matmul_packed_sizes = [8, 0, 32] 
+      matmul_padded_sizes_next_multiple_of = [0, 10, 0] 
+      matmul_inner_dims_order = [1, 2, 0]
+    : (!transform.op<"linalg.generic">) -> !transform.op<"linalg.generic">
+}