[MemRef] Migrate away from PointerUnion::{is,get} (NFC) (llvm#120202)

Note that PointerUnion::{is,get} have been soft deprecated in
PointerUnion.h:

  // FIXME: Replace the uses of is(), get() and dyn_cast() with
  //        isa<T>, cast<T> and the llvm::dyn_cast<T>

I'm not touching PointerUnion::dyn_cast for now because it's a bit
complicated; we could blindly migrate it to dyn_cast_if_present, but
we should probably use dyn_cast when the operand is known to be
non-null.

mlir/lib/Dialect/MemRef/IR/MemRefOps.cpp

@@ -125,7 +125,7 @@ static void constifyIndexValues(
       values[it.index()] = builder.getIndexAttr(constValue);
   }
   for (OpFoldResult &ofr : values) {
-    if (ofr.is<Attribute>()) {
+    if (auto attr = dyn_cast<Attribute>(ofr)) {
       // FIXME: We shouldn't need to do that, but right now, the static indices
       // are created with the wrong type: `i64` instead of `index`.
       // As a result, if we were to keep the attribute as is, we may fail to see
@@ -139,12 +139,11 @@ static void constifyIndexValues(
       // The workaround here is to stick to the IndexAttr type for all the
       // values, hence we recreate the attribute even when it is already static
       // to make sure the type is consistent.
-      ofr = builder.getIndexAttr(
-          llvm::cast<IntegerAttr>(ofr.get<Attribute>()).getInt());
+      ofr = builder.getIndexAttr(llvm::cast<IntegerAttr>(attr).getInt());
       continue;
     }
     std::optional<int64_t> maybeConstant =
-        getConstantIntValue(ofr.get<Value>());
+        getConstantIntValue(cast<Value>(ofr));
     if (maybeConstant)
       ofr = builder.getIndexAttr(*maybeConstant);
   }
@@ -1406,12 +1405,11 @@ static bool replaceConstantUsesOf(OpBuilder &rewriter, Location loc,
     // infinite loops in the driver.
     if (result.use_empty() || maybeConstant == getAsOpFoldResult(result))
       continue;
-    assert(maybeConstant.template is<Attribute>() &&
+    assert(isa<Attribute>(maybeConstant) &&
            "The constified value should be either unchanged (i.e., == result) "
            "or a constant");
     Value constantVal = rewriter.create<arith::ConstantIndexOp>(
-        loc, llvm::cast<IntegerAttr>(maybeConstant.template get<Attribute>())
-                 .getInt());
+        loc, llvm::cast<IntegerAttr>(cast<Attribute>(maybeConstant)).getInt());
     for (Operation *op : llvm::make_early_inc_range(result.getUsers())) {
       // modifyOpInPlace: lambda cannot capture structured bindings in C++17
       // yet.

mlir/lib/Dialect/MemRef/Transforms/ComposeSubView.cpp

@@ -82,7 +82,7 @@ struct ComposeSubViewOpPattern : public OpRewritePattern<memref::SubViewOp> {
          llvm::zip(op.getMixedOffsets(), sourceOp.getMixedOffsets(),
                    sourceOp.getMixedStrides(), op.getMixedSizes())) {
       // We only support static sizes.
-      if (opSize.is<Value>()) {
+      if (isa<Value>(opSize)) {
         return failure();
       }
       sizes.push_back(opSize);
@@ -109,7 +109,7 @@ struct ComposeSubViewOpPattern : public OpRewritePattern<memref::SubViewOp> {
               rewriter.getAffineConstantExpr(cast<IntegerAttr>(attr).getInt());
         } else {
           expr = rewriter.getAffineSymbolExpr(affineApplyOperands.size());
-          affineApplyOperands.push_back(sourceOffset.get<Value>());
+          affineApplyOperands.push_back(cast<Value>(sourceOffset));
         }
 
         // Multiply 'opOffset' by 'sourceStride' and make the 'expr' add the
@@ -121,7 +121,7 @@ struct ComposeSubViewOpPattern : public OpRewritePattern<memref::SubViewOp> {
           expr =
               expr + rewriter.getAffineSymbolExpr(affineApplyOperands.size()) *
                          cast<IntegerAttr>(sourceStrideAttr).getInt();
-          affineApplyOperands.push_back(opOffset.get<Value>());
+          affineApplyOperands.push_back(cast<Value>(opOffset));
         }
 
         AffineMap map = AffineMap::get(0, affineApplyOperands.size(), expr);

mlir/lib/Dialect/MemRef/Transforms/ExpandStridedMetadata.cpp

@@ -383,7 +383,7 @@ SmallVector<OpFoldResult> getExpandedStrides(memref::ExpandShapeOp expandShape,
     AffineExpr s1 = builder.getAffineSymbolExpr(1);
     for (; doneStrideIdx < *dynSizeIdx; ++doneStrideIdx) {
       int64_t baseExpandedStride =
-          cast<IntegerAttr>(expandedStrides[doneStrideIdx].get<Attribute>())
+          cast<IntegerAttr>(cast<Attribute>(expandedStrides[doneStrideIdx]))
               .getInt();
       expandedStrides[doneStrideIdx] = makeComposedFoldedAffineApply(
           builder, expandShape.getLoc(),
@@ -396,7 +396,7 @@ SmallVector<OpFoldResult> getExpandedStrides(memref::ExpandShapeOp expandShape,
   AffineExpr s0 = builder.getAffineSymbolExpr(0);
   for (; doneStrideIdx < groupSize; ++doneStrideIdx) {
     int64_t baseExpandedStride =
-        cast<IntegerAttr>(expandedStrides[doneStrideIdx].get<Attribute>())
+        cast<IntegerAttr>(cast<Attribute>(expandedStrides[doneStrideIdx]))
             .getInt();
     expandedStrides[doneStrideIdx] = makeComposedFoldedAffineApply(
         builder, expandShape.getLoc(), s0 * baseExpandedStride, {origStride});

mlir/lib/Dialect/MemRef/Transforms/IndependenceTransforms.cpp

@@ -21,7 +21,7 @@ using namespace mlir::memref;
 static FailureOr<OpFoldResult> makeIndependent(OpBuilder &b, Location loc,
                                                OpFoldResult ofr,
                                                ValueRange independencies) {
-  if (ofr.is<Attribute>())
+  if (isa<Attribute>(ofr))
     return ofr;
   AffineMap boundMap;
   ValueDimList mapOperands;