Emit unsupported error when parsing a DenseElementAttr with an integer type of greater than 64 bits.

DenseElementAttr currently does not support value bitwidths of > 64. This can result in asan failures and crashes when trying to invoke DenseElementsAttr::writeBits/DenseElementsAttr::readBits.

PiperOrigin-RevId: 229241125

mlir/lib/IR/Attributes.cpp

@@ -170,6 +170,8 @@ ArrayRef<char> DenseElementsAttr::getRawData() const {
 /// starting from `rawData`.
 void DenseElementsAttr::writeBits(char *data, size_t bitPos, size_t bitWidth,
                                   uint64_t value) {
+  assert(bitWidth <= 64 && "expected bitWidth to be within 64-bits");
+
   // Read the destination bytes which will be written to.
   uint64_t dst = 0;
   auto dstData = reinterpret_cast<char *>(&dst);
@@ -195,6 +197,8 @@ void DenseElementsAttr::writeBits(char *data, size_t bitPos, size_t bitWidth,
 /// and put them in the lowest bits.
 uint64_t DenseElementsAttr::readBits(const char *rawData, size_t bitPos,
                                      size_t bitsWidth) {
+  assert(bitsWidth <= 64 && "expected bitWidth to be within 64-bits");
+
   uint64_t dst = 0;
   auto dstData = reinterpret_cast<char *>(&dst);
   auto endPos = bitPos + bitsWidth;

mlir/lib/Parser/Parser.cpp

@@ -766,6 +766,12 @@ TensorLiteralParser::parseElementOrList(llvm::SmallVectorImpl<int> &dims) {
       if (value.getMinSignedBits() > bitWidth)
         return p.emitError("tensor literal element has more bits than that "
                            "specified in the type");
+
+      // FIXME: Handle larger than 64-bit types more gracefully.
+      if (bitWidth > 64)
+        return p.emitError("tensor literal element with more than 64-bits is "
+                           "not currently supported");
+
       addToStorage(value.getSExtValue());
       break;
     }

mlir/test/IR/invalid.mlir

@@ -750,6 +750,15 @@ func @elementsattr_toolarge2() -> () {
 
 // -----
 
+// FIXME: Handle larger than 64-bit types more gracefully.
+func @elementsattr_larger_than_64_bits() -> () {
+^bb0:
+  "fooi67"(){bar: dense<vector<1x1x1xi67>, [[[-5]]]>} : () -> () // expected-error {{tensor literal element with more than 64-bits is not currently supported}}
+  return
+}
+
+// -----
+
 func @elementsattr_malformed_opaque() -> () {
 ^bb0:
   "foo"(){bar: opaque<tensor<1xi8>, "0xQZz123">} : () -> () // expected-error {{opaque string only contains hex digits}}