Add support for kTfLiteInt2 to Dequantize kernels.

This change enables the Dequantize and PerChannelDequantize operations to handle 2-bit integer inputs (`kTfLiteInt2`). It includes logic to unpack the packed 2-bit integers into int8_t before performing the dequantization and adds new test cases for both per-tensor and per-channel dequantization with kTfLiteInt2.

LiteRT-Converter-PiperOrigin-RevId: 822207279

Author: majiddadashi

tflite/converter/ir/tfl_ops.td

@@ -4279,7 +4279,7 @@ def TFL_DequantizeOp: TFL_Op<"dequantize", [NoMemoryEffect]> {
     quantization parameters.
   }];
 
-  let arguments = (ins TFL_TensorOf<[QI4, QI8, QUI8, QI16, F16]>:$input);
+  let arguments = (ins TFL_TensorOf<[QI2, QI4, QI8, QUI8, QI16, F16]>:$input);
 
   let results = (outs TFL_FpTensor:$output);
 

tflite/converter/tools/versioning/op_version.cc

@@ -499,6 +499,9 @@ int GetBuiltinOperatorVersion(const OpSignature& op_sig) {
       return 1;
 
     case BuiltinOperator_DEQUANTIZE:
+      if (op_sig.inputs.at(0).type == kTfLiteInt2) {
+        return 7;
+      }
       if (op_sig.inputs.at(0).type == kTfLiteInt4) {
         return 6;
       }

tflite/converter/tools/versioning/op_version_test.cc

@@ -757,6 +757,12 @@ TEST(OpVersionTest, VersioningDequantizeTest) {
   fake_op_sig.ext_options.dequantize.is_per_channel_quantized = true;
   EXPECT_EQ(GetBuiltinOperatorVersion(fake_op_sig), 5);
 
+  fake_op_sig = {
+      .op = BuiltinOperator_DEQUANTIZE,
+      .inputs = CreateOpSignatureTensorSpecs(kTfLiteInt2),
+  };
+  EXPECT_EQ(GetBuiltinOperatorVersion(fake_op_sig), 7);
+
   fake_op_sig = {
       .op = BuiltinOperator_DEQUANTIZE,
       .inputs = CreateOpSignatureTensorSpecs(kTfLiteFloat32),

tflite/converter/tools/versioning/runtime_version.cc

@@ -326,6 +326,7 @@ std::string FindMinimumRuntimeVersionForOp(tflite::BuiltinOperator op_code,
               {{BuiltinOperator_DEQUANTIZE, 4}, "2.2.0"},
               {{BuiltinOperator_DEQUANTIZE, 5}, "2.7.0"},
               {{BuiltinOperator_DEQUANTIZE, 6}, "2.18.0"},
+              {{BuiltinOperator_DEQUANTIZE, 7}, "2.21.0"},
               {{BuiltinOperator_REVERSE_SEQUENCE, 1}, "1.14.0"},
               {{BuiltinOperator_EQUAL, 1}, "1.14.0"},
               {{BuiltinOperator_EQUAL, 2}, "1.14.0"},