Add Phi-4-mini README.md (#9302)

Author: jackzhxng

examples/models/phi-4-mini/README.md

@@ -0,0 +1,63 @@
+## Summary
+Phi-4-mini Instruct (3.8B) is a newly released version of the popular Phi-4 model developed by Microsoft.
+
+## Instructions
+
+Phi-4-mini uses the same example code as Llama, while the checkpoint, model params, and tokenizer are different. Please see the [Llama README page](../llama/README.md) for details.
+
+All commands for exporting and running Llama on various backends should also be applicable to Phi-4-mini, by swapping the following args:
+```
+--model phi_4_mini
+--params examples/models/phi-4-mini/config.json
+--checkpoint <path-to-meta-checkpoint>
+```
+
+### Generate the Checkpoint
+The original checkpoint can be obtained from HuggingFace:
+```
+huggingface-cli download microsoft/Phi-4-mini-instruct
+```
+
+We then convert it to Meta's checkpoint format:
+```
+python examples/models/phi-4-mini/convert_weights.py <path-to-checkpoint-dir> <output-path>
+```
+
+### Example export and run
+Here is an basic example for exporting and running Phi-4-mini, although please refer to [Llama README page](../llama/README.md) for more advanced usage.
+
+Export to XNNPack, no quantization:
+```
+# No quantization
+# Set these paths to point to the downloaded files
+PHI_CHECKPOINT=path/to/checkpoint.pth
+
+python -m examples.models.llama.export_llama \
+  --model phi_4_mini \
+  --checkpoint "${PHI_CHECKPOINT=path/to/checkpoint.pth:?}" \
+  --params examples/models/phi-4-mini/config.json \
+  -kv \
+  --use_sdpa_with_kv_cache \
+  -d fp32 \
+  -X \
+  --metadata '{"get_bos_id":151643, "get_eos_ids":[151643]}' \
+  --output_name="phi-4-mini.pte"
+  --verbose
+```
+
+Run using the executor runner:
+```
+# Currently a work in progress, just need to enable HuggingFace json tokenizer in C++.
+# In the meantime, can run with an example Python runner with pybindings:
+
+python -m examples.models.llama.runner.native
+  --model phi_4_mini
+  --pte <path-to-pte>
+  -kv
+  --tokenizer <path-to-tokenizer>/tokenizer.json
+  --tokenizer_config <path-to_tokenizer>/tokenizer_config.json
+  --prompt "What is in a california roll?"
+  --params examples/models/phi-4-mini/config.json
+  --max_len 64
+  --temperature 0
+```

examples/models/phi-4-mini/convert_weights.py

@@ -71,7 +71,7 @@ def main():
             "model-00002-of-00002.safetensors",
         ],
         output_dir=".",
-        model_type="PHI3_MINI",
+        model_type="PHI4",
     )
 
     print("Loading checkpoint...")