Add ios.md to explain IREE iOS support (#11758)
Follow up [this
discussion](https://github.com/iree-org/iree/discussions/11732#discussioncomment-4636418)
to document the new support for iOS.
diff --git a/docs/website/docs/building-from-source/ios.md b/docs/website/docs/building-from-source/ios.md
new file mode 100644
index 0000000..550c993
--- /dev/null
+++ b/docs/website/docs/building-from-source/ios.md
@@ -0,0 +1,147 @@
+# iOS cross-compilation
+
+Cross-compilation for iOS consists of the two steps below.
+
+* On the macOS host, build the IREE compiler. We can run it to create
+ IREE modules.
+* Build the IREE runtime on the macOS host for iOS devices and the
+ simulator. We can then run the IREE module on the simulator.
+
+## Prerequisites
+
+### Install Xcode and iOS SDK
+
+For cross-compilation, you need
+[Xcode](https://developer.apple.com/xcode/). It comes with the SDKs
+for iOS devices and the simulator, as well as the `simctl` tool for
+controlling the simulator from the command line.
+
+### Host environment setup
+
+On your host platform, you should already be able to build IREE from
+source. Please make sure you've gone through the steps in [getting
+started](./getting-started.md).
+
+## Configure and Build
+
+### Build the IREE Compiler for the Host
+
+Build and install on your macOS host:
+
+``` shell
+cmake -S . -B ../iree-build/ -GNinja \
+ -DCMAKE_BUILD_TYPE=RelWithDebInfo \
+ -DCMAKE_INSTALL_PREFIX=../iree-build/install
+
+cmake --build ../iree-build/ --target install
+```
+
+## Cross-compile the IREE Runtime for iOS
+
+Build the runtime for the iOS Simulator.
+
+```shell
+cmake -S . -B ../build-ios-sim -GNinja \
+ -DCMAKE_SYSTEM_NAME=iOS \
+ -DCMAKE_OSX_SYSROOT=$(xcodebuild -version -sdk iphonesimulator Path) \
+ -DCMAKE_OSX_ARCHITECTURES=arm64 \
+ -DCMAKE_SYSTEM_PROCESSOR=arm64 \
+ -DCMAKE_OSX_DEPLOYMENT_TARGET=11.0 \
+ -DCMAKE_IOS_INSTALL_COMBINED=YES \
+ -DIREE_HOST_BINARY_ROOT=$PWD/../iree-build/install \
+ -DCMAKE_INSTALL_PREFIX=../build-ios-sim/install \
+ -DIREE_BUILD_COMPILER=OFF
+
+cmake --build ../build-ios-sim --config Release --target install
+```
+
+Or, we can build the runtime for iOS devices it by changing the value
+of the `-DCMAKE OSX SYSROOT` option to:
+
+```shell
+ -DCMAKE_OSX_SYSROOT=$(xcodebuild -version -sdk iphoneos Path)
+```
+
+## Running IREE Modules on the iOS Simulator
+
+Run the IREE compiler on the host to generate a module.
+
+``` shell
+../iree-build/install/bin/iree-compile \
+ --iree-hal-target-backends=vmvx \
+ samples/models/simple_abs.mlir \
+ -o /tmp/simple_abs_vmvx.vmfb
+```
+
+We could test the generated module by running the macOS version of
+`iree-run-module` on the host.
+
+```shell
+../iree-build/install/bin/iree-run-module \
+ --module_file=/tmp/simple_abs_vmvx.vmfb \
+ --device=local-task \
+ --entry_function=abs \
+ --function_input="f32=-5"
+```
+
+To run it on the iOS simulator, we need to copy the vmfb file into the
+`iree-run-module` iOS app bundle.
+
+```
+cp /tmp/simple_abs_vmvx.vmfb \
+ ../build-ios-sim/install/bin/iree-run-module.app/
+```
+
+Open the iOS Simulator Manager on the host.
+
+```shell
+open -a Simulator
+```
+
+After creating and booting a simulator in this app, you can list it
+from the command-line.
+
+```shell
+xcrun simctl list devices | grep Booted
+```
+
+This is what should come out of the command:
+
+```
+ iPhone 14 Pro (12341234-ABCD-ABCD-ABCD-123412341234) (Booted)
+```
+
+where `iPhone 14 Pro` is the device being simulated and
+`12341234-ABCD-ABCD-ABCD-123412341234` is the simulator's _unique
+device ID_ (UDID).
+
+Install the app `iree-run-module` on the simulator, given its UDID.
+
+```shell
+xcrun simctl install <UDID> ../build-ios-sim/install/bin/iree-run-module.app
+```
+
+Check the path to the installed bundle, where the
+`simple_abs_vmvx.vmfb` module should be found.
+
+```shell
+ls $(xcrun simctl get_app_container <UDID> dev.iree.iree-run-module)
+```
+
+The string `dev.iree.iree-run-module` is the _bundle identifier_ of
+the iOS app. The CMake building process generates it and saves it in
+the _property list_ (plist) file
+`../build-ios-sim/install/bin/iree-run-module.app/Info.plist`.
+
+Launch the `iree-run-module` app on the simulator to run the IREE
+module `simple_abs_vmvx.vmfb`.
+
+```shell
+xcrun simctl launch --console \
+ <UDID> \
+ dev.iree.runmodule \
+ --device=local-task \
+ --entry_function=abs \
+ --function_input="f32=-5" \
+ --module_file=$(xcrun simctl get_app_container <UDID> dev.iree.iree-run-module)/simple_abs_vmvx.vmfb
+```
diff --git a/docs/website/docs/index.md b/docs/website/docs/index.md
index 3a1a75c..24969b2 100644
--- a/docs/website/docs/index.md
+++ b/docs/website/docs/index.md
@@ -33,8 +33,8 @@
- [x] Linux
- [x] Windows
- [x] Android
-- [ ] macOS (planned)
-- [ ] iOS (planned)
+- [x] macOS
+- [x] iOS
- [x] Bare metal
- [ ] WebAssembly (planned)
diff --git a/docs/website/mkdocs.yml b/docs/website/mkdocs.yml
index 38d878c..138a372 100644
--- a/docs/website/mkdocs.yml
+++ b/docs/website/mkdocs.yml
@@ -111,6 +111,7 @@
- "building-from-source/getting-started.md"
- "building-from-source/python-bindings-and-importers.md"
- "building-from-source/android.md"
+ - "building-from-source/ios.md"
- "building-from-source/riscv.md"
- "Bindings":
- "bindings/index.md"
