From 37f9f81776ed20082a2ae907b63017e1f8355c2e Mon Sep 17 00:00:00 2001
From: Aqeel Akber <aqeel@aqeelakber.com>
Date: Fri, 19 Sep 2025 22:41:08 +1000
Subject: [PATCH] feat(opencl): add optional OpenCL backend support via Cargo
 feature

Introduce an `opencl` feature for both crates, package ggml-opencl sources,
and enable GGML_OPENCL in build.rs with per-OS linking to the OpenCL loader.
Keeps changes consistent with existing CUDA/Vulkan patterns.
---
 llama-cpp-2/Cargo.toml     |  1 +
 llama-cpp-sys-2/Cargo.toml |  2 ++
 llama-cpp-sys-2/README.md  |  2 +-
 llama-cpp-sys-2/build.rs   | 21 +++++++++++++++++++++
 4 files changed, 25 insertions(+), 1 deletion(-)

diff --git a/llama-cpp-2/Cargo.toml b/llama-cpp-2/Cargo.toml
index bcb85c6f..99667138 100644
--- a/llama-cpp-2/Cargo.toml
+++ b/llama-cpp-2/Cargo.toml
@@ -32,6 +32,7 @@ sampler = []
 # Only has an impact on Android.
 android-shared-stdcxx = ["llama-cpp-sys-2/shared-stdcxx"]
 mtmd = ["llama-cpp-sys-2/mtmd"]
+opencl = ["llama-cpp-sys-2/opencl"]
 
 
 [target.'cfg(all(target_os = "macos", any(target_arch = "aarch64", target_arch = "arm64")))'.dependencies]
diff --git a/llama-cpp-sys-2/Cargo.toml b/llama-cpp-sys-2/Cargo.toml
index fa5d46d0..a85ed1af 100644
--- a/llama-cpp-sys-2/Cargo.toml
+++ b/llama-cpp-sys-2/Cargo.toml
@@ -39,6 +39,7 @@ include = [
     "/llama.cpp/ggml/src/ggml-cuda/**/*",
     "/llama.cpp/ggml/src/ggml-metal/**/*",
     "/llama.cpp/ggml/src/ggml-vulkan/**/*",
+    "/llama.cpp/ggml/src/ggml-opencl/**/*",
 
     "/llama.cpp/ggml/src/llamafile/sgemm.h",
     "/llama.cpp/ggml/src/llamafile/sgemm.cpp",
@@ -81,3 +82,4 @@ openmp = []
 # Only has an impact on Android.
 shared-stdcxx = []
 mtmd = []
+opencl = []
diff --git a/llama-cpp-sys-2/README.md b/llama-cpp-sys-2/README.md
index 69dd4733..a932ba40 100644
--- a/llama-cpp-sys-2/README.md
+++ b/llama-cpp-sys-2/README.md
@@ -1,5 +1,5 @@
 # llama-cpp-sys
 
-Raw bindings to llama.cpp with cuda support.
+Raw bindings to llama.cpp with cuda and opencl support.
 
 See [llama-cpp-2](https://crates.io/crates/llama-cpp-2) for a safe API.
diff --git a/llama-cpp-sys-2/build.rs b/llama-cpp-sys-2/build.rs
index 08fcd49b..dc9e8492 100644
--- a/llama-cpp-sys-2/build.rs
+++ b/llama-cpp-sys-2/build.rs
@@ -625,6 +625,27 @@ fn main() {
         }
     }
 
+    // OpenCL backend
+    if cfg!(feature = "opencl") {
+        config.define("GGML_OPENCL", "ON");
+        // Explicit for clarity; upstream defaults are ON
+        config.define("GGML_OPENCL_USE_ADRENO_KERNELS", "ON");
+        config.define("GGML_OPENCL_EMBED_KERNELS", "ON");
+
+        match target_os {
+            TargetOs::Apple(_) => {
+                println!("cargo:rustc-link-lib=framework=OpenCL");
+            }
+            TargetOs::Windows(_) => {
+                println!("cargo:rustc-link-lib=OpenCL");
+            }
+            TargetOs::Linux | TargetOs::Android => {
+                println!("cargo:rustc-link-lib=OpenCL");
+            }
+            _ => (),
+        }
+    }
+
     // Android doesn't have OpenMP support AFAICT and openmp is a default feature. Do this here
     // rather than modifying the defaults in Cargo.toml just in case someone enables the OpenMP feature
     // and tries to build for Android anyway.