Add web doc for bare-metal codegen/run (#6401)
Part of https://github.com/google/iree/issues/6327
diff --git a/docs/website/docs/deployment-configurations/bare-metal.md b/docs/website/docs/deployment-configurations/bare-metal.md
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+# Run on a Bare-Metal Platform
+
+IREE supports CPU model execution on a bare-metal platform. That is, a platform
+without operating system support, and the executable is built with the
+machine-specific linker script and/or the board support package (BSP).
+
+Bare-metal deployment typically uses IREE's LLVM compiler target much like the
+[CPU - Dylib](./cpu-dylib.md)
+configuration, but using a limited subset of IREE's CPU HAL driver at runtime to
+load and execute compiled programs.
+
+## Prerequisites
+
+Out-of-tree bare-metal platform tools and source code for the system should be
+ready, such as
+
+* Compilation toolchain
+* Platform linker script
+* Firmware libraries
+
+Please follow the
+[instructions](./cpu-dylib.md#get-compiler-for-cpu-native-instructions)
+to retrieve the IREE compiler.
+
+## Compile the model for bare-metal
+
+The model can be compiled with the following command from the IREE compiler
+build directory
+
+``` shell hl_lines="3 4 5 6"
+iree/tools/iree-translate \
+ -iree-mlir-to-vm-bytecode-module \
+ -iree-hal-target-backends=dylib-llvm-aot \
+ -iree-llvm-link-embedded=true \
+ -iree-llvm-target-triple=x86_64-pc-linux-elf \
+ -iree-llvm-debug-symbols=false \
+ iree/samples/models/simple_abs.mlir \
+ -o /tmp/simple_abs_dylib.vmfb
+
+```
+
+In which
+
+* `iree-hal-target-backends=dylib-llvm-aot`: Build the model for the dynamic
+library CPU HAL driver
+* `iree-llvm-link-embedded=true`: Generate the dynamic library with
+[LLD](https://lld.llvm.org/) and the artifact can be loaded with the
+[embedded library loader](https://github.com/google/iree/blob/main/iree/hal/local/loaders/embedded_library_loader.h)
+without invoking the dynamic library support
+* `iree-llvm-target-triple`: Use the `<arch>-pc-linux-elf` LLVM target triple so
+the artifact has a fixed ABI to be rendered by the
+[elf_module library](https://github.com/google/iree/tree/main/iree/hal/local/elf)
+* `iree-llvm-debug-symbols=false`: To reduce the artifact size
+
+See [generate.sh](https://github.com/google/iree/blob/main/iree/hal/local/elf/testdata/generate.sh)
+for example command-line instructions of some common architectures
+
+You can replace the MLIR file with the other MLIR model files, following the
+[instructions](./cpu-dylib.md#compile-the-model)
+
+!!! todo
+ Add the static library support
+
+## Build bare-metal runtime from the source
+
+A few CMake options and macros should be set to build a subset of IREE runtime
+libraries compatible with the bare-metal platform. We assume there's no
+multi-thread control nor system library support in the bare-metal system. The
+model execution is in a single-thread synchronous fashion.
+
+### Set CMake options
+
+* `set(IREE_BUILD_COMPILER OFF)`: Build IREE runtime only
+* `set(IREE_ENABLE_MLIR OFF)`: Disable LLVM/MLIR dependencies for the runtime
+library
+* `set(CMAKE_SYSTEM_NAME Generic)`: Tell CMake to skip targeting a specific
+operating system
+* `set(IREE_BINDINGS_TFLITE OFF)`: Disable the TFLite binding support
+* `set(IREE_ENABLE_THREADING OFF)`: Disable multi-thread library support
+* `set(IREE_HAL_DRIVERS_TO_BUILD "Dylib;VMVX")`: Build only the dynamic library
+and VMVX runtime HAL drivers
+* `set(IREE_BUILD_TESTS OFF)`: Disable tests until IREE supports running them on
+bare-metal platforms
+* `set(IREE_BUILD_SAMPLES ON)`: Build
+[simple_embedding](https://github.com/google/iree/tree/main/iree/samples/simple_embedding)
+example
+
+!!! todo
+ Clean the list up after [#6353](https://github.com/google/iree/issues/6353)
+ is fixed.
+
+Also, set the toolchain-specific cmake file to match the tool path, target
+architecture, target abi, linker script, system library path, etc.
+
+### Define IREE macros
+
+* `-DIREE_PLATFORM_GENERIC`: Let IREE to build the runtime library without
+targeting a specific platform
+* `-DIREE_SYNCHRONIZATION_DISABLE_UNSAFE=1`: Disable thread synchronization
+support
+* `-DIREE_TIME_NOW_FN`: A function to return the system time. For the bare-metal
+system, it can be set as `-DIREE_TIME_NOW_FN=\"\{ return 0;\}\"` as there's no
+asynchronous wait handling
+
+Examples of how to setup the CMakeLists.txt and .cmake file:
+
+* [IREE RISC-V toolchain cmake](https://github.com/google/iree/blob/main/build_tools/cmake/riscv.toolchain.cmake)
+* [IREE Bare-Metal Arm Sample](https://github.com/iml130/iree-bare-metal-arm)
+
+## Bare-metal execution example
+
+See
+[simple_embedding for generic platform](https://github.com/google/iree/blob/main/iree/samples/simple_embedding/README.md#generic-platform-support)
+to see how to use the IREE runtime library to build/run the IREE model for the
+bare-metal target.
diff --git a/docs/website/mkdocs.yml b/docs/website/mkdocs.yml
index 4281f2e..a6dca81 100644
--- a/docs/website/mkdocs.yml
+++ b/docs/website/mkdocs.yml
@@ -101,6 +101,7 @@
- JAX: 'ml-frameworks/jax.md'
- 'Deployment configurations':
- CPU - Dylib: 'deployment-configurations/cpu-dylib.md'
+ - CPU - Bare-Metal: 'deployment-configurations/bare-metal.md'
- GPU - Vulkan: 'deployment-configurations/gpu-vulkan.md'
- 'Building from source':
# - 'building-from-source/index.md' # TODO(scotttodd): insiders + navigation.indexes
