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                         <h1 id="installation"><a class="header" href="#installation">Installation</a></h1>
 <p>In the future, <code>std::offload</code> should become available in nightly builds for users. For now, everyone still needs to build rustc from source.</p>
 <h2 id="build-instructions"><a class="header" href="#build-instructions">Build instructions</a></h2>
 <p>First you need to clone and configure the Rust repository:</p>
 <pre><code class="language-bash">git clone --depth=1 git@github.com:rust-lang/rust.git
 cd rust
 ./configure --enable-llvm-link-shared --release-channel=nightly --enable-llvm-assertions --enable-offload --enable-enzyme --enable-clang --enable-lld --enable-option-checking --enable-ninja --disable-docs
 </code></pre>
 <p>Afterwards you can build rustc using:</p>
 <pre><code class="language-bash">./x.py build --stage 1 library
 </code></pre>
 <p>Afterwards rustc toolchain link will allow you to use it through cargo:</p>
 <pre><code>rustup toolchain link offload build/host/stage1
 rustup toolchain install nightly # enables -Z unstable-options
 </code></pre>
 <h2 id="build-instruction-for-llvm-itself"><a class="header" href="#build-instruction-for-llvm-itself">Build instruction for LLVM itself</a></h2>
 <pre><code class="language-bash">git clone --depth=1 git@github.com:llvm/llvm-project.git
 cd llvm-project
 mkdir build
 cd build
 cmake -G Ninja ../llvm -DLLVM_TARGETS_TO_BUILD="host,AMDGPU,NVPTX" -DLLVM_ENABLE_ASSERTIONS=ON -DLLVM_ENABLE_PROJECTS="clang;lld" -DLLVM_ENABLE_RUNTIMES="offload,openmp" -DLLVM_ENABLE_PLUGINS=ON -DCMAKE_BUILD_TYPE=Release -DCMAKE_INSTALL_PREFIX=.
 ninja
 ninja install
 </code></pre>
 <p>This gives you a working LLVM build.</p>
 <h2 id="testing"><a class="header" href="#testing">Testing</a></h2>
 <p>run</p>
 <pre><code>./x.py test --stage 1 tests/codegen/gpu_offload
 </code></pre>
 <h2 id="usage"><a class="header" href="#usage">Usage</a></h2>
 <p>It is important to use a clang compiler build on the same llvm as rustc. Just calling clang without the full path will likely use your system clang, which probably will be incompatible.</p>
 <pre><code>/absolute/path/to/rust/build/x86_64-unknown-linux-gnu/stage1/bin/rustc --edition=2024 --crate-type cdylib src/main.rs --emit=llvm-ir  -O -C lto=fat -Cpanic=abort -Zoffload=Enable
 /absolute/path/to/rust/build/x86_64-unknown-linux-gnu/llvm/bin/clang++ -fopenmp --offload-arch=native -g  -O3 main.ll -o main -save-temps
 LIBOMPTARGET_INFO=-1  ./main
 </code></pre>
 <p>The first step will generate a <code>main.ll</code> file, which has enough instructions to cause the offload runtime to move data to and from a gpu.
 The second step will use clang as the compilation driver to compile our IR file down to a working binary. Only a very small Rust subset will work out of the box here, unless
 you use features like build-std, which are not covered by this guide. Look at the codegen test to get a feeling for how to write a working example.
 In the last step you can run your binary, if all went well you will see a data transfer being reported:</p>
 <pre><code>omptarget device 0 info: Entering OpenMP data region with being_mapper at unknown:0:0 with 1 arguments:
 omptarget device 0 info: tofrom(unknown)[1024]
 omptarget device 0 info: Creating new map entry with HstPtrBase=0x00007fffffff9540, HstPtrBegin=0x00007fffffff9540, TgtAllocBegin=0x0000155547200000, TgtPtrBegin=0x0000155547200000, Size=1024, DynRefCount=1, HoldRefCount=0, Name=unknown
 omptarget device 0 info: Copying data from host to device, HstPtr=0x00007fffffff9540, TgtPtr=0x0000155547200000, Size=1024, Name=unknown
 omptarget device 0 info: OpenMP Host-Device pointer mappings after block at unknown:0:0:
 omptarget device 0 info: Host Ptr           Target Ptr         Size (B) DynRefCount HoldRefCount Declaration
 omptarget device 0 info: 0x00007fffffff9540 0x0000155547200000 1024     1           0            unknown at unknown:0:0
 // some other output
 omptarget device 0 info: Exiting OpenMP data region with end_mapper at unknown:0:0 with 1 arguments:
 omptarget device 0 info: tofrom(unknown)[1024]
 omptarget device 0 info: Mapping exists with HstPtrBegin=0x00007fffffff9540, TgtPtrBegin=0x0000155547200000, Size=1024, DynRefCount=0 (decremented, delayed deletion), HoldRefCount=0
 omptarget device 0 info: Copying data from device to host, TgtPtr=0x0000155547200000, HstPtr=0x00007fffffff9540, Size=1024, Name=unknown
 omptarget device 0 info: Removing map entry with HstPtrBegin=0x00007fffffff9540, TgtPtrBegin=0x0000155547200000, Size=1024, Name=unknown
 </code></pre>

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	<div id="content" class="content">
	<main>
	<h1 id="installation"><a class="header" href="#installation">Installation</a></h1>
	<p>In the future, <code>std::offload</code> should become available in nightly builds for users. For now, everyone still needs to build rustc from source.</p>
	<h2 id="build-instructions"><a class="header" href="#build-instructions">Build instructions</a></h2>
	<p>First you need to clone and configure the Rust repository:</p>
	<pre><code class="language-bash">git clone --depth=1 git@github.com:rust-lang/rust.git
	cd rust
	./configure --enable-llvm-link-shared --release-channel=nightly --enable-llvm-assertions --enable-offload --enable-enzyme --enable-clang --enable-lld --enable-option-checking --enable-ninja --disable-docs
	</code></pre>
	<p>Afterwards you can build rustc using:</p>
	<pre><code class="language-bash">./x.py build --stage 1 library
	</code></pre>
	<p>Afterwards rustc toolchain link will allow you to use it through cargo:</p>
	<pre><code>rustup toolchain link offload build/host/stage1
	rustup toolchain install nightly # enables -Z unstable-options
	</code></pre>
	<h2 id="build-instruction-for-llvm-itself"><a class="header" href="#build-instruction-for-llvm-itself">Build instruction for LLVM itself</a></h2>
	<pre><code class="language-bash">git clone --depth=1 git@github.com:llvm/llvm-project.git
	cd llvm-project
	mkdir build
	cd build
	cmake -G Ninja ../llvm -DLLVM_TARGETS_TO_BUILD="host,AMDGPU,NVPTX" -DLLVM_ENABLE_ASSERTIONS=ON -DLLVM_ENABLE_PROJECTS="clang;lld" -DLLVM_ENABLE_RUNTIMES="offload,openmp" -DLLVM_ENABLE_PLUGINS=ON -DCMAKE_BUILD_TYPE=Release -DCMAKE_INSTALL_PREFIX=.
	ninja
	ninja install
	</code></pre>
	<p>This gives you a working LLVM build.</p>
	<h2 id="testing"><a class="header" href="#testing">Testing</a></h2>
	<p>run</p>
	<pre><code>./x.py test --stage 1 tests/codegen/gpu_offload
	</code></pre>
	<h2 id="usage"><a class="header" href="#usage">Usage</a></h2>
	<p>It is important to use a clang compiler build on the same llvm as rustc. Just calling clang without the full path will likely use your system clang, which probably will be incompatible.</p>
	<pre><code>/absolute/path/to/rust/build/x86_64-unknown-linux-gnu/stage1/bin/rustc --edition=2024 --crate-type cdylib src/main.rs --emit=llvm-ir -O -C lto=fat -Cpanic=abort -Zoffload=Enable
	/absolute/path/to/rust/build/x86_64-unknown-linux-gnu/llvm/bin/clang++ -fopenmp --offload-arch=native -g -O3 main.ll -o main -save-temps
	LIBOMPTARGET_INFO=-1 ./main
	</code></pre>
	<p>The first step will generate a <code>main.ll</code> file, which has enough instructions to cause the offload runtime to move data to and from a gpu.
	The second step will use clang as the compilation driver to compile our IR file down to a working binary. Only a very small Rust subset will work out of the box here, unless
	you use features like build-std, which are not covered by this guide. Look at the codegen test to get a feeling for how to write a working example.
	In the last step you can run your binary, if all went well you will see a data transfer being reported:</p>
	<pre><code>omptarget device 0 info: Entering OpenMP data region with being_mapper at unknown:0:0 with 1 arguments:
	omptarget device 0 info: tofrom(unknown)[1024]
	omptarget device 0 info: Creating new map entry with HstPtrBase=0x00007fffffff9540, HstPtrBegin=0x00007fffffff9540, TgtAllocBegin=0x0000155547200000, TgtPtrBegin=0x0000155547200000, Size=1024, DynRefCount=1, HoldRefCount=0, Name=unknown
	omptarget device 0 info: Copying data from host to device, HstPtr=0x00007fffffff9540, TgtPtr=0x0000155547200000, Size=1024, Name=unknown
	omptarget device 0 info: OpenMP Host-Device pointer mappings after block at unknown:0:0:
	omptarget device 0 info: Host Ptr Target Ptr Size (B) DynRefCount HoldRefCount Declaration
	omptarget device 0 info: 0x00007fffffff9540 0x0000155547200000 1024 1 0 unknown at unknown:0:0
	// some other output
	omptarget device 0 info: Exiting OpenMP data region with end_mapper at unknown:0:0 with 1 arguments:
	omptarget device 0 info: tofrom(unknown)[1024]
	omptarget device 0 info: Mapping exists with HstPtrBegin=0x00007fffffff9540, TgtPtrBegin=0x0000155547200000, Size=1024, DynRefCount=0 (decremented, delayed deletion), HoldRefCount=0
	omptarget device 0 info: Copying data from device to host, TgtPtr=0x0000155547200000, HstPtr=0x00007fffffff9540, Size=1024, Name=unknown
	omptarget device 0 info: Removing map entry with HstPtrBegin=0x00007fffffff9540, TgtPtrBegin=0x0000155547200000, Size=1024, Name=unknown
	</code></pre>

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