audio float API (#15234)

### Summary
Some audio inputs are float[]
### Test plan
CI

cc @cbilgin

Co-authored-by: Hansong Zhang <[email protected]>

Author: pytorchbot

extension/android/executorch_android/src/main/java/org/pytorch/executorch/extension/llm/LlmModule.java

@@ -233,6 +233,28 @@ public long prefillAudio(byte[] audio, int batch_size, int n_bins, int n_frames)
 
   private native int appendAudioInput(byte[] audio, int batch_size, int n_bins, int n_frames);
 
+  /**
+   * Prefill a multimodal Module with the given audio input.
+   *
+   * @param audio Input preprocessed audio as a float array
+   * @param batch_size Input batch size
+   * @param n_bins Input number of bins
+   * @param n_frames Input number of frames
+   * @return 0, as the updated starting position in KV cache of the input in the LLM is no longer
+   *     exposed to user.
+   * @throws RuntimeException if the prefill failed
+   */
+  @Experimental
+  public long prefillAudio(float[] audio, int batch_size, int n_bins, int n_frames) {
+    int nativeResult = appendAudioInputFloat(audio, batch_size, n_bins, n_frames);
+    if (nativeResult != 0) {
+      throw new RuntimeException("Prefill failed with error code: " + nativeResult);
+    }
+    return 0;
+  }
+
+  private native int appendAudioInputFloat(float[] audio, int batch_size, int n_bins, int n_frames);
+
   /**
    * Prefill a multimodal Module with the given raw audio input.
    *

extension/android/jni/jni_layer_llama.cpp

@@ -325,6 +325,29 @@ class ExecuTorchLlmJni : public facebook::jni::HybridClass<ExecuTorchLlmJni> {
     return 0;
   }
 
+  // Returns status_code
+  jint append_audio_input_float(
+      facebook::jni::alias_ref<jfloatArray> data,
+      jint batch_size,
+      jint n_bins,
+      jint n_frames) {
+    if (data == nullptr) {
+      return static_cast<jint>(Error::EndOfMethod);
+    }
+    auto data_size = data->size();
+    if (data_size != 0) {
+      std::vector<jfloat> data_jfloat(data_size);
+      std::vector<float> data_f(data_size);
+      data->getRegion(0, data_size, data_jfloat.data());
+      for (int i = 0; i < data_size; i++) {
+        data_f[i] = data_jfloat[i];
+      }
+      llm::Audio audio{std::move(data_f), batch_size, n_bins, n_frames};
+      prefill_inputs_.emplace_back(llm::MultimodalInput{std::move(audio)});
+    }
+    return 0;
+  }
+
   // Returns status_code
   jint append_raw_audio_input(
       facebook::jni::alias_ref<jbyteArray> data,
@@ -388,6 +411,9 @@ class ExecuTorchLlmJni : public facebook::jni::HybridClass<ExecuTorchLlmJni> {
             ExecuTorchLlmJni::append_normalized_images_input),
         makeNativeMethod(
             "appendAudioInput", ExecuTorchLlmJni::append_audio_input),
+        makeNativeMethod(
+            "appendAudioInputFloat",
+            ExecuTorchLlmJni::append_audio_input_float),
         makeNativeMethod(
             "appendRawAudioInput", ExecuTorchLlmJni::append_raw_audio_input),
         makeNativeMethod(