[mlir][memref] Make LoadOp::verify error more clear (#75831)

While debugging #71326, the
`LoadOp::verify` code and error were very confusing. This PR improves
that.

This code was a part from the reverted PR
#75519. Fixing the
`-convert-vector-to-scf` issue is going to take a bit longer and this
code was out of scope anyway.

Co-authored-by: Benjamin Maxwell <macdue@dueutil.tech>

Author: rikhuijzer

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

@@ -1615,8 +1615,10 @@ GetGlobalOp::verifySymbolUses(SymbolTableCollection &symbolTable) {
 //===----------------------------------------------------------------------===//
 
 LogicalResult LoadOp::verify() {
-  if (getNumOperands() != 1 + getMemRefType().getRank())
-    return emitOpError("incorrect number of indices for load");
+  if (static_cast<int64_t>(getIndices().size()) != getMemRefType().getRank()) {
+    return emitOpError("incorrect number of indices for load, expected ")
+           << getMemRefType().getRank() << " but got " << getIndices().size();
+  }
   return success();
 }
 

mlir/test/Dialect/MemRef/invalid.mlir

@@ -896,6 +896,15 @@ func.func @bad_alloc_wrong_symbol_count() {
 
 // -----
 
+func.func @load_invalid_memref_indexes() {
+  %0 = memref.alloca() : memref<10xi32>
+  %c0 = arith.constant 0 : index
+  // expected-error@+1 {{incorrect number of indices for load, expected 1 but got 2}}
+  %1 = memref.load %0[%c0, %c0] : memref<10xi32>
+}
+
+// -----
+
 func.func @test_store_zero_results() {
 ^bb0:
   %0 = memref.alloc() : memref<1024x64xf32, affine_map<(d0, d1) -> (d0, d1)>, 1>