[mlir][tosa] Fix segmentation fault in case of folding unranked tensor

Trying to fold the unranked tensor for "tosa.equal" crashes due to null reference.
We need to check the dynamic cast result beforehand. This is reported in
#60192.

Reviewed By: rsuderman

Differential Revision: https://reviews.llvm.org/D143034

mlir/lib/Dialect/Tosa/IR/TosaCanonicalizations.cpp

@@ -803,8 +803,8 @@ OpFoldResult EqualOp::fold(FoldAdaptor adaptor) {
 
   // If we are comparing an integer value to itself it is always true. We can
   // not do this with float due to float values.
-  if (lhsTy.getElementType().isa<IntegerType>() && resultTy.hasStaticShape() &&
-      lhs == rhs) {
+  if (lhsTy.getElementType().isa<IntegerType>() && resultTy &&
+      resultTy.hasStaticShape() && lhs == rhs) {
     return DenseElementsAttr::get(resultTy, true);
   }
 

mlir/test/Dialect/Tosa/constant_folding.mlir

@@ -6,3 +6,11 @@ func.func @test_const(%arg0 : index) -> tensor<4xi32> {
   %0 = "tosa.const"() {value = dense<[3, 0, 1, 2]> : tensor<4xi32>} : () -> tensor<4xi32>
   return %0 : tensor<4xi32>
 }
+
+// CHECK-LABEL: func @try_fold_equal_with_unranked_tensor
+func.func @try_fold_equal_with_unranked_tensor(%arg0: tensor<4xi32>, %arg1: tensor<i32>) {
+  // CHECK: "tosa.equal"
+  // CHECK-NEXT: return
+  %0 = "tosa.equal"(%arg0, %arg1) : (tensor<4xi32>, tensor<i32>) -> tensor<*xi1>
+  return
+}