[mlir][linalg] Relax masked_vectorize(pad) to allow zero low Values.

[hanchung]

Summary

It only accepted zeros attributes before the revision. It now acccepts
constant-like zero values as well.

[hanchung]

fix lit test

[dcaballe]

mlir/test/Dialect/Linalg/vectorization.mlir

2852

Could you add another test with a non-constant symbol?

[hanchung]

add a test

mlir/lib/Dialect/Linalg/Transforms/Vectorization.cpp

mlir::linalg::maskedVectorize(RewriterBase &rewriter, tensor::PadOp padOp,
 
   ArrayRef<int64_t> resultTensorShape = padOp.getResultType().getShape();
   if (!(resultTensorShape == inputVectorSizes)) {
     LDBG("result tensor shape must match input vector sizes: " << padOp
                                                                << "\n");
     return rewriter.notifyMatchFailure(
         padOp, "result tensor shape must match input vector sizes");
   }
-  if (llvm::any_of(padOp.getStaticLow(),
-                   [](int64_t val) { return val != 0; })) {
+  if (llvm::any_of(padOp.getLow(), [](Value v) {
+        std::optional<int64_t> res = getConstantIntValue(v);
+        return !res.has_value() || res.value() != 0;
+      })) {
     LDBG("low pad must all be zero: " << padOp << "\n");
     return rewriter.notifyMatchFailure(padOp, "low pad must all be zero");
   }
 
   Location loc = padOp.getLoc();
   int64_t rank = inputVectorSizes.size();
   auto maskType = VectorType::get(inputVectorSizes, rewriter.getI1Type());
   auto vectorType = VectorType::get(inputVectorSizes, padValue.getType());

mlir/test/Dialect/Linalg/vectorization.mlir

func.func @test_masked_vectorize_pad(
   //      CHECK: %[[mask:.*]] = vector.create_mask %[[d0]], %[[d1]] : vector<2x4xi1>
   //      CHECK: %[[masked_read:.*]] = vector.mask %[[mask]] {
   // CHECK-SAME:   vector.transfer_read %{{.*}}[%[[c0]], %[[c0]]], %[[c42]]
   // CHECK-SAME:   {in_bounds = [true, true]} : tensor<?x?xf32>, vector<2x4xf32>
   // CHECK-SAME: } : vector<2x4xi1> -> vector<2x4xf32>
   //      CHECK: vector.transfer_write %[[masked_read]], %[[empty]][%[[c0]], %[[c0]]]
   // CHECK-SAME:   {in_bounds = [true, true]} : vector<2x4xf32>, tensor<2x4xf32>
   %cst = arith.constant 42.43 : f32
-  %1 = tensor.pad %0 low[0, 0] high[%h0, %h1]  {
+  %c0 = arith.constant 0 : index
+  %1 = tensor.pad %0 low[0, %c0] high[%h0, %h1]  {
     ^bb0(%hh1: index, %hh2: index):
       tensor.yield %cst : f32
     } : tensor<?x?xf32> to tensor<2x4xf32>
   return %1: tensor<2x4xf32>
 }
 
 transform.sequence failures(propagate) {
 ^bb1(%arg1: !pdl.operation):