Update docs for the demo app. (#2921)

Summary:
Pull Request resolved: #2921
overriding_review_checks_triggers_an_audit_and_retroactive_review
Oncall Short Name: executorch

Differential Revision: D55885790

fbshipit-source-id: bb62a42b74ecdfb2e1f6bcebab979e2e8fcf0a3c

Author: shoumikhin

docs/source/_static/img/llama_ios_app.mp4

@@ -1 +1 @@
-```{include} ../../examples/demo-apps/apple_ios/README.md
+```{include} ../../examples/demo-apps/apple_ios/ExecuTorchDemo/README.md

docs/source/_static/img/llama_ios_app.png

@@ -626,7 +626,7 @@ The rest of the steps will be the same as the normal flow. Now you can run this
 ## How to build Mobile Apps
 You can also execute an LLM using ExecuTorch on iOS and Android
 
-**For iOS details see the [iOS Sample App](https://github.com/pytorch/executorch/tree/main/examples/demo-apps/apple_ios).**
+**For iOS see the [iLLaMA App](https://pytorch.org/executorch/main/llm/llama-demo-ios.html).**
 
 
 **For Android see the [Android Instructions](https://pytorch.org/executorch/main/llm/llama-demo-android.html).**

docs/source/demo-apps-ios.md

@@ -0,0 +1,2 @@
+```{include} ../../../examples/demo-apps/apple_ios/LLaMA/README.md
+```

docs/source/llm/getting-started.md

@@ -0,0 +1,37 @@
+# Building ExecuTorch LLaMA iOS Demo App
+
+This app demonstrates the use of the LLaMA chat app demonstrating local inference use case with ExecuTorch.
+
+<img src="../_static/img/llama_ios_app.png" alt="iOS LLaMA App" /><br>
+
+## Prerequisites
+* [Xcode 15](https://developer.apple.com/xcode).
+* [iOS 17 SDK](https://developer.apple.com/ios).
+* Set up your ExecuTorch repo and environment if you haven’t done so by following the [Setting up ExecuTorch](https://pytorch.org/executorch/stable/getting-started-setup) to set up the repo and dev environment.
+
+## Exporting models
+Please refer to the [ExecuTorch Llama2 docs](https://github.com/pytorch/executorch/blob/main/examples/models/llama2/README.md) to export the model.
+
+## Run the App
+
+1. Open the [project](https://github.com/pytorch/executorch/blob/main/examples/demo-apps/apple_ios/LLaMA/LLaMA.xcodeproj) in Xcode.
+2. Run the app (cmd+R).
+3. In app UI pick a model and tokenizer to use, type a prompt and tap the arrow buton as on the [video](../_static/img/llama_ios_app.mp4).
+
+```{note}
+ExecuTorch runtime is distributed as a Swift package providing some .xcframework as prebuilt binary targets. Xcode will dowload and cache the package on the first run, which will take some time.
+```
+
+## Copy the model to Simulator
+
+1. Drag&drop the model and tokenizer files onto the Simulator window and save them somewhere inside the iLLaMA folder.
+2. Pick the files in the app dialog, type a prompt and click the arrow-up button.
+
+## Copy the model to Device
+
+1. Wire-connect the device and open the contents in Finder.
+2. Navigate to the Files tab and drag&drop the model and tokenizer files onto the iLLaMA folder.
+3. Wait until the files are copied.
+
+## Reporting Issues
+If you encountered any bugs or issues following this tutorial please file a bug/issue here on [Github](https://github.com/pytorch/executorch/issues/new).

docs/source/llm/llama-demo-ios.md

@@ -218,11 +218,13 @@ adb push cmake-out-android/examples/models/llama2/llama_main /data/local/tmp/lla
 ```
 adb shell "cd /data/local/tmp/llama && ./llama_main --model_path <model.pte> --tokenizer_path <tokenizer.bin> --prompt "Once upon a time" --seq_len 120
 ```
-## Step 6: Build iOS and/or Android apps
+## Step 6: Build Mobile apps
 
-TODO
+### iOS
+
+Please refer to [this tutorial](https://pytorch.org/executorch/main/llm/llama-demo-ios.html) to for full instructions on building the iOS LLAMA Demo App.
 
-### Android app
+### Android
 Please refer to [this tutorial](https://pytorch.org/executorch/main/llm/llama-demo-android.html) to for full instructions on building the Android LLAMA Demo App.
 
 # What is coming next?