package/mesa3d: add RustiCL support

RustiCL is an OpenCL implementation written entirely in
RUST and integrated into Mesa3D. It enables the use of OpenCL
programs on top of existing Gallium drivers. RustiCL is a
modern and maintainable replacement for the old C-implemention
Clover.

To build Rusticl in Mesa3D, the following components are required:

  - host-rustc (Rust compiler)
  - host-rust-bindgen (for generating bindings)
  - spirv-tools
  - spirv-llvm-translator (providing libLLVMSPIRVLib.so matching the LLVM version)
  - LLVM built with libclc and -DLLVM_ENABLE_DUMP=ON
  - Mesa headers via mesa-clc-bundle-headers=enabled
  - There is a known meson bug and in order to fix it we set -Drust_std=2021, see:
    https://docs.mesa3d.org/rusticl.html#known-issues
    https://github.com/mesonbuild/meson/issues/10664

More details in the Mesa documentation:
https://docs.mesa3d.org/rusticl.html

Rusticl is the provider of OpenCL in Buildroot.
However, Mesa does not provide the `libOpenCL.so` library itself.
We therefore depend on the `opencl-icd-loader` package to
install this loader in the toolchain sysroot, so that other
OpenCL-dependent packages can build and link against it.

Without the ICD loader, only `libRustiOpenCL.so` is available and
tools like `clinfo` or `clpeak` fail.

- 'Dmesa-clc-bundle-headers=enabled' ensures that the OpenCL header
   files are bundled and available in the target. Without this,
   runtime compilation of OpenCL kernels via clpeak or clinfo fails
   with:
	fatal error: 'opencl-c-base.h' file not found

see https://gitlab.freedesktop.org/mesa/mesa/-/commit/3619611b31bade726b3dd3d0583ff41a5794cad3

We add a Rust compiler override to Meson to use Buildroot’s
host Rust toolchain using MESA3D_MESON_EXTRA_BINARIES.
Rusticl requires Meson to invoke rustc with the correct target and linker:
    * 'rust=['$(HOST_DIR)/bin/rustc','--target=$(RUSTC_TARGET_NAME)']'
    * 'rust_ld='$(TARGET_CROSS)gcc''
Another solution was proposed to set rust and rust_ld globally in
cross-compilation.conf, we prefer to define them locally within mesa
for now to ensure precise control over the rust toolchain behavior
during the Mesa build.

see https://lore.kernel.org/buildroot/ZcOeEMfwX4XlRXO7@landeda/

Currently, we should always use RUSTICL_ENABLE= driver to use rusticl.
More information:
https://docs.mesa3d.org/envvars.html#envvar-RUSTICL_ENABLE

Signed-off-by: El Mehdi YOUNES <elmehdi.younes@smile.fr>
[Julien: add references to meson bug]
Signed-off-by: Julien Olivain <ju.o@free.fr>

package/mesa3d/Config.in

@@ -50,19 +50,43 @@ comment "llvm support needs a toolchain not affected by GCC bug 64735"
 	depends on BR2_PACKAGE_LLVM_ARCH_SUPPORTS
 	depends on BR2_TOOLCHAIN_HAS_GCC_BUG_64735
 
-# clang and libclc dependencies are satisfied by
-# BR2_PACKAGE_MESA3D_LLVM
-config BR2_PACKAGE_MESA3D_OPENCL
+menuconfig BR2_PACKAGE_MESA3D_OPENCL
 	bool "OpenCL support"
 	depends on BR2_PACKAGE_MESA3D_LLVM
 	depends on BR2_PACKAGE_MESA3D_GALLIUM_DRIVER_R600 || \
 		BR2_PACKAGE_MESA3D_GALLIUM_DRIVER_PANFROST || \
 		BR2_PACKAGE_MESA3D_GALLIUM_DRIVER_RADEONSI || \
-		BR2_PACKAGE_MESA3D_GALLIUM_DRIVER_IRIS
+		BR2_PACKAGE_MESA3D_GALLIUM_DRIVER_IRIS || \
+		BR2_PACKAGE_HOST_RUSTC_TARGET_ARCH_SUPPORTS && \
+		BR2_PACKAGE_MESA3D_RUSTICL_SUPPORTED_DRIVER
 	select BR2_PACKAGE_LLVM_RTTI
 	select BR2_PACKAGE_CLANG
 	select BR2_PACKAGE_LIBCLC
 	select BR2_PACKAGE_HAS_LIBOPENCL
+if BR2_PACKAGE_MESA3D_OPENCL
+# libclc dependency is satisfied by
+# BR2_PACKAGE_MESA3D_LLVM
+config BR2_PACKAGE_MESA3D_RUSTICL
+	bool "RustiCL"
+	depends on BR2_PACKAGE_HOST_RUSTC_TARGET_ARCH_SUPPORTS
+	depends on BR2_PACKAGE_MESA3D_RUSTICL_SUPPORTED_DRIVER
+	select BR2_PACKAGE_HOST_RUSTC
+	select BR2_PACKAGE_LLVM_DUMP
+	select BR2_PACKAGE_SPIRV_TOOLS
+	select BR2_PACKAGE_SPIRV_LLVM_TRANSLATOR
+	select BR2_PACKAGE_OPENCL_ICD_LOADER
+	help
+	  RustiCL is an OpenCL implementation written in Rust.
+	  By default, devices are disabled in RustiCL. If you want
+	  to enable a device, you need to set the environment variable
+	  RUSTICL_ENABLE to the driver you are using.
+
+	  https://docs.mesa3d.org/envvars.html#envvar-RUSTICL_ENABLE
+
+endif # BR2_PACKAGE_MESA3D_OPENCL
+
+config BR2_PACKAGE_MESA3D_RUSTICL_SUPPORTED_DRIVER
+	bool
 
 # inform the .mk file of gallium or vulkan driver selection
 config BR2_PACKAGE_MESA3D_GALLIUM_DRIVER
@@ -139,6 +163,7 @@ config BR2_PACKAGE_MESA3D_GALLIUM_DRIVER_IRIS
 	depends on BR2_PACKAGE_MESA3D_LLVM
 	select BR2_PACKAGE_MESA3D_GALLIUM_DRIVER
 	select BR2_PACKAGE_MESA3D_NEEDS_PRECOMP_COMPILER
+	select BR2_PACKAGE_MESA3D_RUSTICL_SUPPORTED_DRIVER
 	help
 	  Mesa driver for iris-based Intel GPUs.
 
@@ -157,6 +182,7 @@ config BR2_PACKAGE_MESA3D_GALLIUM_DRIVER_LLVMPIPE
 	bool "Gallium llvmpipe driver"
 	depends on BR2_PACKAGE_MESA3D_LLVM
 	select BR2_PACKAGE_MESA3D_GALLIUM_DRIVER
+	select BR2_PACKAGE_MESA3D_RUSTICL_SUPPORTED_DRIVER
 	help
 	  This is a llvm opengl implementation using the Gallium3D
 	  infrastructure.
@@ -170,6 +196,7 @@ config BR2_PACKAGE_MESA3D_GALLIUM_DRIVER_NOUVEAU
 	select BR2_PACKAGE_LIBDRM_NOUVEAU
 	select BR2_PACKAGE_MESA3D_NEEDS_XA
 	select BR2_PACKAGE_LLVM_RTTI if BR2_PACKAGE_MESA3D_LLVM
+	select BR2_PACKAGE_MESA3D_RUSTICL_SUPPORTED_DRIVER
 	help
 	  Supports all Nvidia GPUs.
 
@@ -179,6 +206,7 @@ config BR2_PACKAGE_MESA3D_GALLIUM_DRIVER_PANFROST
 	depends on BR2_PACKAGE_MESA3D_LLVM
 	select BR2_PACKAGE_MESA3D_GALLIUM_DRIVER
 	select BR2_PACKAGE_MESA3D_NEEDS_PRECOMP_COMPILER
+	select BR2_PACKAGE_MESA3D_RUSTICL_SUPPORTED_DRIVER
 	help
 	  Mesa driver for ARM Mali Midgard and Bifrost GPUs.
 
@@ -229,6 +257,7 @@ config BR2_PACKAGE_MESA3D_GALLIUM_DRIVER_RADEONSI
 	select BR2_PACKAGE_LLVM_AMDGPU
 	select BR2_PACKAGE_ELFUTILS
 	select BR2_PACKAGE_MESA3D_NEEDS_ELFUTILS
+	select BR2_PACKAGE_MESA3D_RUSTICL_SUPPORTED_DRIVER
 	help
 	  Driver for ATI/AMD Radeon HD7000/HD8000/Rx200 GPUs.
 

package/mesa3d/mesa3d.mk

@@ -30,7 +30,6 @@ MESA3D_DEPENDENCIES = \
 	zlib
 
 MESA3D_CONF_OPTS = \
-	-Dgallium-rusticl=false \
 	-Dmicrosoft-clc=disabled
 
 ifeq ($(BR2_PACKAGE_MESA3D_DRIVER)$(BR2_PACKAGE_XORG7),yy)
@@ -56,6 +55,30 @@ MESA3D_PROVIDES += libopencl
 MESA3D_DEPENDENCIES += clang libclc
 endif
 
+ifeq ($(BR2_PACKAGE_MESA3D_RUSTICL),y)
+MESA3D_DEPENDENCIES += \
+	host-rustc \
+	host-rust-bindgen \
+	spirv-tools \
+	spirv-llvm-translator \
+	opencl-icd-loader
+
+# rust_std is defined here to workaround a known meson bug. See:
+# https://docs.mesa3d.org/rusticl.html#known-issues
+# https://github.com/mesonbuild/meson/issues/10664
+MESA3D_CONF_OPTS += \
+	-Dgallium-rusticl=true \
+	-Drust_std=2021 \
+	-Dmesa-clc-bundle-headers=enabled
+
+MESA3D_MESON_EXTRA_BINARIES += \
+	rust=['$(HOST_DIR)/bin/rustc','--target=$(RUSTC_TARGET_NAME)'] \
+	rust_ld='$(TARGET_CROSS)gcc'
+
+else
+MESA3D_CONF_OPTS += -Dgallium-rusticl=false
+endif
+
 ifeq ($(BR2_PACKAGE_MESA3D_NEEDS_ELFUTILS),y)
 MESA3D_DEPENDENCIES += elfutils
 endif