feat(compiler): add ESP-IDF LLVM optimization enablement framework

Co-authored-by: Cursor <cursoragent@cursor.com>

examples/system/llvm_opt/README.md

@@ -0,0 +1,43 @@
+| Supported Targets | ESP32-P4 |
+| ----------------- | -------- |
+
+# LLVM optimization (component scope)
+
+Minimal example for the ESP-IDF LLVM optimization framework. It shows how to
+apply the LLVM optimizations selected in menuconfig to **an entire component**
+with the `ENABLE_LLVM_OPT` argument of `idf_component_register`:
+
+```cmake
+idf_component_register(SRCS "llvm_opt_main.c"
+                       INCLUDE_DIRS ""
+                       ENABLE_LLVM_OPT)
+```
+
+Enable the option in menuconfig: **Compiler options > LLVM optimizations >
+Optimize memcpy with PIE**. On ESP32-P4 with the Clang toolchain, ESP-IDF then
+injects the corresponding compiler flags into every source file of this
+component.
+
+With the default GCC toolchain the example still builds (for CI board smoke
+tests); `ENABLE_LLVM_OPT` is ignored and CMake prints a warning. Use Clang for
+real LLVM opt flags:
+
+
+## Build and run
+
+Activate the Clang toolchain before configuring the project:
+
+```bash
+cd "$IDF_PATH/examples/system/llvm_opt"
+IDF_TOOLCHAIN=clang idf.py set-target esp32p4
+IDF_TOOLCHAIN=clang idf.py build flash monitor
+```
+
+`CONFIG_COMPILER_LLVM_MEMCPY_OPTIMIZATION` is enabled by `sdkconfig.defaults`
+and can be changed with `idf.py menuconfig`.
+
+## Related example
+
+For the file-level API (`idf_component_enable_llvm_opt`) and a `memcpy`
+benchmark comparing optimized and baseline sources, see the
+`llvm_memcpy_opt` example.