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<!--#include virtual="header.incl" -->
<div class="www_sectiontitle">Open LLVM Projects</div>
<ul>
<li>Google Summer of Code Ideas & Projects
<ul>
<li>
<a href="#gsoc25">Google Summer of Code 2025</a>
<ul>
<li><b>LLVM Core</b>
<ul>
<li><a href="#llvm-abi-lowering">Introduce an ABI lowering library</a></li>
<li><a href="#byte-type">Byte type</a></li>
</ul>
<li><a href="http://clang.llvm.org/"><b>Clang</b></a>
<ul>
<li><a href="#clang-driver-modules">Simple C++20 modules without a build system</a></li>
<li><a href="#clang-improve-trapping-ubsan-2025">Usability Improvements for trapping Undefined Behavior Sanitizer (UBSan)</a></li>
<li><a href="#improve-documentation-parsing-in-clang">Improve documentation parsing in Clang</a></li>
<li><a href="#improve-symbol-discovery-clang-repl">Advanced symbol resolution and reoptimization for clang-repl</a></li>
</ul>
</li>
<li><a href="http://lldb.llvm.org/"><b>LLDB</b></a>
<ul>
<li><a href="#rich-disassembler-for-lldb-2025">Rich disassembler for LLDB</a></li>
</ul>
</li>
<li><a href="http://libc.llvm.org/"><b>LLVM libc</b></a>
<ul>
<li><a href="#bfloat16-libc">Bfloat16 in LLVM libc</a></li>
<li><a href="#io_uring-libc">Direct I/O from the GPU with io_uring</a></li>
<li><a href="#testing-math-libc">Profiling and testing the LLVM libc GPU math</a></li>
</ul>
</li>
<li><a href="https://clangir.org"><b>ClangIR</b></a>
<ul>
<li><a href="#clangir-codegen-tests">Validate existing Clang CodeGen test coverage with ClangIR</a></li>
<li><a href="#clangir-upstreaming">Participate in ClangIR upstreaming</a></li>
</ul>
</li>
<li><a href="https://clang.llvm.org/docs/ClangStaticAnalyzer.html"><b>Clang Static Analyzer</b></a>
<ul>
<li><a href="#csa-lifetime-annotations">Teach the Clang Static Analyzer to understand lifetime annotations</a></li>
</ul>
</li>
<li><a href="https://enzyme.mit.edu"><b>Enzyme</b></a>
<ul>
<li><a href="#rust-enzyme-improvements">Improve Enzyme reliability and compile times for Rust</a></li>
</ul>
</li>
<li><a href="https://discourse.llvm.org/t/offload-new-subproject-pending-move-of-libomptarget/78185"><b>Offload</b></a> (Former <a href="https://openmp.llvm.org/"><b>OpenMP Offloading</b></a>)
<ul>
<li><a href="#offload-remarks-visualization">LLVM Compiler Remarks Visualization Tool for Offload Proposal</a></li>
</ul>
</li>
</ul>
</li>
<li>
<a href="#gsoc24">Google Summer of Code 2024</a>
<ul>
<li><b>LLVM Core</b>
<ul>
<li><a href="#remove_ub_tests">Remove undefined behavior from tests</a></li>
<li><a href="#spirv_tablegen">Automatically generate TableGen file for SPIR-V instruction set</a></li>
<li><a href="#bitstream_cas">LLVM bitstream integration with CAS (content-addressable storage)</a></li>
<li><a href="#three_way_comparison">Add 3-way comparison intrinsics</a></li>
<li><a href="#llvm_www">Improve the LLVM.org Website Look and Feel</a></li>
<li><a href="#parameter-tuning">The 1001 thresholds in LLVM</a></li>
</ul>
<li><a href="http://clang.llvm.org/"><b>Clang</b></a>
<ul>
<li><a href="#clang-repl-out-of-process">Out-of-process execution for clang-repl</a></li>
<li><a href="#clang-plugins-windows">Support clang plugins on Windows</a></li>
<li><a href="#clang-on-demand-parsing">On Demand Parsing in Clang</a></li>
<li><a href="#clang-doc-improve-usability">Improve Clang-Doc Usability</a></li>
</ul>
<li><a href="http://lldb.llvm.org/"><b>LLDB</b></a>
<ul>
<li><a href="#rich-disassembler-for-lldb">Rich disassembler for LLDB</a></li>
</ul>
<li><a href="http://openmp.llvm.org/"><b>(OpenMP) Offload</b></a>
<ul>
<li><a href="#gpu-delta-debugging">GPU Delta Debugging</a></li>
<li><a href="#offload-libcxx">Offloading libcxx</a></li>
<li><a href="#gpu-libc">Performance tuning the GPU libc</a></li>
<li><a href="#gpu-first">Improve GPU First Framework</a></li>
</ul>
<li><a href="https://clangir.org"><b>ClangIR</b></a>
<ul>
<li><a href="#clangir-gpu">Compile GPU kernels using ClangIR</a></li>
</ul>
<li><a href="http://libc.llvm.org/"><b>LLVM libc</b></a>
<ul>
<li><a href="#half-precision-libc">Half precision in LLVM libc</a>
</ul>
</ul>
</li>
<li>
<a href="#gsoc23">Google Summer of Code 2023</a>
<ul>
<li>
<b>LLVM Core</b>
<ul>
<li><a href="#llvm_new_jitlink_reopt">Re-optimization using JITLink</a></li>
<li><a href="#llvm_new_jitlink_backends">JITLink new backends</a></li>
<li><a href="#llvm_improving_compile_times">Improving compile times</a></li>
<li><a href="#llvm_addressing_rust_optimization_failures">Addressing Rust optimization failures</a></li>
<li><a href="#llvm_mlgo_latency_model">Better performance models for MLGO training</a></li>
<li><a href="#llvm_mlgo_passes_2023">Machine Learning Guided Ordering of Compiler Optimization Passes</a></li>
<li><a href="#llvm_map_value_to_src_expr">Map LLVM values to corresponding source-level expressions</a></li>
</ul>
</li>
<li><a href="http://clang.llvm.org/"><b>Clang</b></a>
<ul>
<li><a href="#clang-repl-out-of-process">Out-of-process execution for clang-repl</a>
<li><a href="#clang_analyzer_taint_analysis">Improve and Stabilize the Clang Static Analyzer's "Taint Analysis" Checks</a></li>
<li><a href="#clang-repl-autocompletion">Implement autocompletion in clang-repl</a>
<li><a href="#clang-modules-build-daemon">Modules build daemon: build system agnostic support for explicitly built modules</a></li>
<li><a href="#clang-extract-api-categories">ExtractAPI Objective-C categories</a></li>
<li><a href="#clang-extract-api-cpp-support">ExtractAPI C++ Support</a></li>
<li><a href="#clang-extract-api-while-building">ExtractAPI while building</a></li>
<li><a href="#clang-improve-diagnostics2">Improve Clang diagnostics</a></li>
<li><a href="#clang-tutorials-clang-repl">Tutorial development with clang-repl</a></li>
<li><a href="#clang-repl-wasm">Add WebAssembly Support in clang-repl</a></li>
</li>
</ul>
</li>
<li>
<b>LLD</b>
<ul>
<li><a href="#llvm_lld_embedded">LLD Linker Improvements for Embedded Targets</a></li>
</ul>
</li>
<li>
<b>MLIR</b>
<ul>
<li><a href="#llvm_mlir_presburger_opt">Optimizing MLIR’s Presburger library</a></li>
<li><a href="#llvm_mlir_query">Interactively query MLIR IR</a></li>
</ul>
</li>
<li>
<b>Code Coverage</b>
<ul>
<li><a href="#llvm_code_coverage">Support a hierarchical directory structure in generated coverage html reports</a></li>
<li><a href="#llvm_patch_coverage">Patch based test coverage for quick test feedback</a></li>
</ul>
</li>
<li>
<b>ClangIR</b>
<ul>
<li><a href="#clangir">Build and run SingleSource benchmarks using ClangIR</a></li>
</ul>
</li>
<li>
<b><a href="https://enzyme.mit.edu">Enzyme</a></b>
<ul>
<li><a href="#enzyme_tblgen_extension">Move additional Enzyme Rules to Tablegen</a></li>
</ul>
</li>
</ul>
</li>
<li>
<a href="#gsoc22">Google Summer of Code 2022</a>
<ul>
<li>
<b>LLVM Core</b>
<ul>
<li><a href="#llvm_shared_jitlink">Implement a shared-memory based JITLinkMemoryManager for out-of-process JITting</a></li>
<li><a href="#llvm_build_jit_tutorial">Modernize the LLVM "Building A JIT" tutorial series</a></li>
<li><a href="#llvm_jit_new_format">Write JITLink support for a new format/architecture</a></li>
<li><a href="#llvm_instrumentaion_for_compile_time">Instrumentation of Clang/LLVM for Compile Time</a></li>
<li><a href="#llvm_lto_dependency_info">Richer symbol dependency information for LTO</a></li>
<li><a href="#llvm_mlgo_passes">Machine Learning Guided Ordering of Compiler Optimization Passes</a></li>
<li><a href="#llvm_mlgo_loop">Learning Loop Transformation Heuristics</a></li>
<li><a href="#llvm_module_inliner">Evaluate and Expand the Module-Level Inliner</a></li>
<li><a href="#llvm_undef_load">Remove undef: move uninitialized memory to poison</a></li>
<li><a href="#llvm_abi_export">Add ABI/API export annotations to the LLVM build</a></li>
</ul>
</li>
<li><a href="http://clang.llvm.org/"><b>Clang</b></a>
<ul>
<li><a href="#clang-template-instantiation-sugar">Extend clang AST to
provide information for the type as written in template
instantiations</a>
</li>
<li><a href="#clang-sa-structured-bindings">Implement support for
C++17 structured bindings in the Clang Static Analyzer</a>
</li>
<li><a href="#clang-improve-diagnostics">Improve Clang Diagnostics</a>
</li>
</ul>
</li>
<li>
<a href="https://polly.llvm.org"><b>Polly</b></a>
<ul>
<li><a href="#polly_npm">Completely switch to new pass manager</a></li>
</ul>
</li>
<li>
<b><a href="https://enzyme.mit.edu">Enzyme</a></b>
<ul>
<li><a href="#enzyme_tblgen">Move Enzyme Instruction Transformation Rules to Tablegen</a></li>
<li><a href="#enzyme_vector">Vector Reverse-Mode Automatic Differentiation</a></li>
<li><a href="#enzyme_pm">Enable The New Pass Manager</a></li>
</ul>
</li>
</ul>
</li>
<li>
<a href="#gsoc21">Google Summer of Code 2021</a>
<ul>
<li>
<b>LLVM Core</b>
<ul>
<li><a href="#llvm_distributing_lit">Distributed lit testing</a></li>
<li><a href="#llvm_loop_heuristics">Learning Loop Transformation Heuristics</a></li>
<li><a href="#llvm_ir_fuzzing">Fuzzing LLVM-IR Passes</a></li>
<li><a href="#llvm_ir_assume"><tt>llvm.assume</tt> the missing pieces</a></li>
<li><a href="#llvm_shared_jitlink">Implement a shared-memory based JITLinkMemoryManager for out-of-process JITting</a></li>
<li><a href="#llvm_build_jit_tutorial">Modernize the LLVM "Building A JIT" tutorial series</a></li>
<li><a href="#llvm_jit_new_format">Write JITLink support for a new format/architecture</a></li>
<li><a href="#llvm_ir_issues">Fix fundamental issues in LLVM's IR</a></li>
<li><a href="#llvm_utilize_loopnest">Utilize LoopNest Pass</a></li>
</ul>
</li>
<li><a href="http://clang.llvm.org/"><b>Clang</b></a>
<ul>
<li><a href="#clang-template-instantiation-sugar">Extend clang AST to
provide information for the type as written in template
instantiations</a>
</li>
</ul>
</li>
<li>
<b>OpenMP</b>
<ul>
<li><a href="#openmp_gpu_jit">JIT-ing OpenMP GPU kernels transparently</a></li>
</ul>
</li>
<li>
<b>OpenACC</b>
<ul>
<li><a href="#openacc_rt_diagnostics">OpenACC Diagnostics from the OpenMP Runtime</a></li>
</ul>
</li>
<li>
<b><a href="https://polly.llvm.org">Polly</a></b>
<ul>
<li><a href="#polly_isl_bindings">Use official isl C++ bindings</a></li>
</ul>
</li>
<li>
<b><a href="https://enzyme.mit.edu">Enzyme</a></b>
<ul>
<li><a href="#enzyme_blas">Integrate custom derivatives of BLAS, Eigen, and similar routines into Enzyme</a></li>
<li><a href="#enzyme_swift">Integrate Enzyme into Swift to provide high-performance differentiation in Swift</a></li>
<li><a href="#enzyme_fixed">Differentiation of Fixed-Point Arithmetic</a></li>
<li><a href="#enzyme_rust">Integrate Enzyme into Rust to provide high-performance differentiation in Rust</a></li>
</ul>
</li>
<li>
<b>Clang Static Analyzer</b>
<ul>
<li><a href="#static_analyzer_profling">Clang Static Analyzer performance profiling</a></li>
<li><a href="#static_analyzer_constraint_solver">Clang Static Analyzer constraint solver improvements</a></li>
</ul>
</li>
<li>
<b>LLDB</b>
<ul>
<li><a href="#lldb_diagnostics">A structured approach to diagnostics in LLDB</a></li>
</ul>
</li>
</ul>
</li>
<li>
<a href="#gsoc20">Google Summer of Code 2020</a>
<ul>
<li>
<b>LLVM Core</b>
<ul>
<li><a href="#llvm_optimized_debugging">Improve debugging of optimized code</a></li>
<li><a href="#llvm_ipo">Improve inter-procedural analyses and optimizations</a></li>
<li><a href="#llvm_par">Improve parallelism-aware analyses and optimizations</a></li>
<li><a href="#llvm_dbg_invariant">Make LLVM passes debug info invariant</a></li>
<li><a href="#llvm_mergesim">Improve MergeFunctions to incorporate MergeSimilarFunction patches and ThinLTO Support</a></li>
<li><a href="#llvm_dwarf_yaml2obj">Add DWARF support to yaml2obj</a></li>
<li><a href="#llvm_hotcold">Improve hot cold splitting to aggressively outline small blocks</a></li>
<li><a href="#llvm_pass_order">Advanced Heuristics for Ordering Compiler Optimization Passes</a></li>
<li><a href="#llvm_ml_scc">Machine learning and compiler optimizations: using inter-procedural analysis to select optimizations</a></li>
<li><a href="#llvm_postdominators">Add PostDominatorTree in LoopStandardAnalysisResults</a></li>
<li><a href="#llvm_loopnest">Create loop nest pass</a></li>
<li><a href="#llvm_instdump">Instruction properties dumper and checker</a></li>
<li><a href="#llvm_movecode">Unify ways to move code or check if code is safe to be moved</a></li>
</ul>
<li><a href="http://clang.llvm.org/"><b>Clang</b></a>
<ul>
<li><a href="#clang-template-instantiation-sugar">Extend clang AST to
provide information for the type as written in template
instantiations</a>
</li>
<li><a href="#clang-sa-cplusplus-checkers">Find null smart pointer dereferences
with the Static Analyzer</a>
</li>
</ul>
</li>
<li><a href="http://lldb.llvm.org/"><b>LLDB</b></a></li>
<ul>
<li><a href="#lldb-autosuggestions">Support autosuggestions in LLDB's command line</a></li>
<li><a href="#lldb-more-completions">Implement the missing tab completions for LLDB's command line</a></li>
<li><a href="#lldb-reimplement-lldb-cmdline">Reimplement LLDB's command-line commands using the public SB API.</a></li>
<li><a href="#lldb-batch-testing">Add support for batch-testing to the LLDB testsuite.</a></li>
</ul>
<li>
<b>MLIR</b>
<ul>
<li>See the <a href="https://mlir.llvm.org/getting_started/openprojects/">MLIR open project list</a></li>
</ul>
</li>
</ul>
</li>
<li>
<a href="#gsoc19">Google Summer of Code 2019</a>
<ul>
<li>
<b>LLVM Core</b>
<ul>
<li><a href="#debuginfo_codegen_mismatch">Debug Info should have no
effect on codegen</a></li>
<li><a href="#llvm_function_attributes">Improve (function) attribute
inference</a></li>
<li><a href="#improve_binary_utilities">Improve LLVM binary utilities
</a></li>
</ul>
</li>
<li><a href="http://clang.llvm.org/"><b>Clang</b></a>
<ul>
<li><a href="#clang-astimporter-fuzzer">Implement an ASTImporter
fuzzer</a>
</li>
<li><a href="#improve-autocompletion">Improve shell autocompletion
for Clang</a>
</li>
<li><a href="#analyze-llvm">Apply the Clang Static Analyzer to LLVM-based
Projects</a>
</li>
<li><a href="#header-generation">Generate annotated sources based on
LLVM-IR analyses</a>
</li>
</ul>
</li>
</ul>
</li>
<li><a href="#gsoc18">Google Summer of Code 2018</a></li>
<li><a href="#gsoc17">Google Summer of Code 2017</a></li>
</ul>
</li>
<li><a href="#what">What is this?</a></li>
<li><a href="#subprojects">LLVM Subprojects: Clang and more</a></li>
<li><a href="#improving">Improving the current system</a>
<ol>
<li><a href="#target-desc">Factor out target descriptions</a></li>
<li><a href="#code-cleanups">Implementing Code Cleanup bugs</a></li>
<li><a href="#programs">Compile programs with the LLVM Compiler</a></li>
<li><a href="#llvmtest">Add programs to the llvm-test suite</a></li>
<li><a href="#benchmark">Benchmark the LLVM compiler</a></li>
<li><a href="#statistics">Benchmark Statistics and Warning System</a></li>
<li><a href="#coverage">Improving Coverage Reports</a></li>
<li><a href="#misc_imp">Miscellaneous Improvements</a></li>
</ol></li>
<li><a href="#new">Adding new capabilities to LLVM</a>
<ol>
<li><a href="#llvm_ir">Extend the LLVM intermediate representation</a></li>
<li><a href="#pointeranalysis">Pointer and Alias Analysis</a></li>
<li><a href="#profileguided">Profile-Guided Optimization</a></li>
<li><a href="#compaction">Code Compaction</a></li>
<li><a href="#xforms">New Transformations and Analyses</a></li>
<li><a href="#codegen">Code Generator Improvements</a></li>
<li><a href="#misc_new">Miscellaneous Additions</a></li>
</ol></li>
<li><a href="#using">Project using LLVM</a>
<ol>
<li><a href="#machinemodulepass">Add a MachineModulePass</a></li>
<li><a href="#encodeanalysis">Encode Analysis Results in MachineInstr IR</a></li>
<li><a href="#codelayoutjit">Code Layout in the LLVM JIT</a></li>
<li><a href="#fieldlayout">Improved Structure Splitting and Field Reordering</a></li>
<li><a href="#slimmer">Finish the Slimmer Project</a></li>
</ol></li>
</ul>
<div class="doc_author">
<p>Written by the <a href="/">LLVM Team</a></p>
</div>
<!-- *********************************************************************** -->
<div class="www_sectiontitle">
<a name="gsoc25">Google Summer of Code 2025</a>
</div>
<!-- *********************************************************************** -->
<div class="www_text">
<p>
Welcome prospective Google Summer of Code 2025 Students! This document is
your starting point to finding interesting and important projects for LLVM,
Clang, and other related sub-projects. This list of projects is not only
developed for Google Summer of Code, but open projects that really need
developers to work on and are very beneficial for the LLVM community.
</p>
<p>We encourage you to look through this list and see which projects excite
you and match well with your skill set. We also invite proposals not on this
list. More information and discussion about GSoC can be found in
<a href="https://discourse.llvm.org/c/community/gsoc" target="_blank">
discourse
</a>. If you have questions about a particular project please find the
relevant entry in discourse, check previous discussion and ask. If there is
no such entry or you would like to propose an idea please create a new
entry. Feedback from the community is a requirement for your proposal to be
considered and hopefully accepted.
</p>
<p>The LLVM project has participated in Google Summer of Code for many years
and has had some very successful projects. We hope that this year is no
different and look forward to hearing your proposals. For information on how
to submit a proposal, please visit the Google Summer of Code main
<a href="https://summerofcode.withgoogle.com/">website.</a>
</p>
</div>
<!-- *********************************************************************** -->
<div class="www_subsubsection">
<a name="rich-disassembler-for-lldb-2025">Rich Disassembler for LLDB</a>
</div>
<!-- *********************************************************************** -->
<div class="www_text">
<p><b>Description</b></p>
<p>Use the variable location information from the debug info to annotate LLDB’s disassembler (and `register read`) output with the location and lifetime of source variables. The rich disassembler output should be exposed as structured data and made available through LLDB’s scripting API so more tooling could be built on top of this. In a terminal, LLDB should render the annotations as text.</p>
<p><b>Expected outcomes</b></p>
For example, we could augment the disassembly for the following function
<pre>
frame #0: 0x0000000100000f80 a.out`main(argc=1, argv=0x00007ff7bfeff1d8) at demo.c:4:10 [opt]
1 void puts(const char*);
2 int main(int argc, char **argv) {
3 for (int i = 0; i < argc; ++i)
→ 4 puts(argv[i]);
5 return 0;
6 }
(lldb) disassemble
a.out`main:
...
0x100000f71 <+17>: movl %edi, %r14d
0x100000f74 <+20>: xorl %r15d, %r15d
0x100000f77 <+23>: nopw (%rax,%rax)
→ 0x100000f80 <+32>: movq (%rbx,%r15,8), %rdi
0x100000f84 <+36>: callq 0x100000f9e ; symbol stub for: puts
0x100000f89 <+41>: incq %r15
0x100000f8c <+44>: cmpq %r15, %r14
0x100000f8f <+47>: jne 0x100000f80 ; <+32> at demo.c:4:10
0x100000f91 <+49>: addq $0x8, %rsp
0x100000f95 <+53>: popq %rbx
...
</pre>
<p>using the debug information that LLDB also has access to (observe how the source variable i is in r15 from [0x100000f77+slide))</p>
<pre>
$ dwarfdump demo.dSYM --name i
demo.dSYM/Contents/Resources/DWARF/demo: file format Mach-O 64-bit x86-64
0x00000076: DW_TAG_variable
DW_AT_location (0x00000098:
[0x0000000100000f60, 0x0000000100000f77): DW_OP_consts +0, DW_OP_stack_value
[0x0000000100000f77, 0x0000000100000f91): DW_OP_reg15 R15)
DW_AT_name ("i")
DW_AT_decl_file ("/tmp/t.c")
DW_AT_decl_line (3)
DW_AT_type (0x000000b2 "int")
</pre>
to produce output like this, where we annotate when a variable is live and what its location is:
<pre>
(lldb) disassemble
a.out`main:
... ; i=0
0x100000f74 <+20>: xorl %r15d, %r15d ; i=r15
0x100000f77 <+23>: nopw (%rax,%rax) ; |
→ 0x100000f80 <+32>: movq (%rbx,%r15,8), %rdi ; |
0x100000f84 <+36>: callq 0x100000f9e ; symbol stub for: puts ; |
0x100000f89 <+41>: incq %r15 ; |
0x100000f8c <+44>: cmpq %r15, %r14 ; |
0x100000f8f <+47>: jne 0x100000f80 ; <+32> at t.c:4:10 ; |
0x100000f91 <+49>: addq $0x8, %rsp ; i=undef
0x100000f95 <+53>: popq %rbx
</pre>
<p>The goal would be to produce output like this for a subset of unambiguous cases, for example, variables that are constant or fully in registers.</p>
<p><b>Confirmed mentors and their contacts</p></b>
<ul>
<li>Adrian Prantl [email protected] (primary contact)
<li>Jonas Devlieghere [email protected]
</ul>
<p><b>Required / desired skills</b></p>
<p>Required:</p>
<ul>
<li>Good understanding of C++
<li>Familiarity with using a debugger on the terminal
<li>Need to be familiar with all the concepts mentioned in the example above
<li>Need to have a good understanding of at least one assembler dialect for machine code (x86_64 or AArch64).
</ul>
<p>Desired:</p>
<ul>
<li>Compiler knowledge including data flow and control flow analysis is a plus.
<li>Being able to navigate debug information (DWARF) is a plus.
</ul>
<p><b>Size of the project:</b></p>
<p>medium (~175h)</p>
<p><b>Project difficulty:</b></p>
<p>hard</p>
<p><b>Discourse:</b> <a href="https://discourse.llvm.org/t/rich-disassembler-for-lldb/76952">URL</a></p>
</div>
<!-- *********************************************************************** -->
<div class="www_subsubsection">
<a name="bfloat16-libc">Bfloat16 in LLVM libc</a>
</div>
<!-- *********************************************************************** -->
<div class="www_text">
<p><b>Description:</b></p>
<p>
<a href="https://en.wikipedia.org/wiki/Bfloat16_floating-point_format">Bfloat16</a>
is a recently developed floating point format tailored to machine
learning and AI, and in the latest <a href="https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2023/n4950.pdf">C++23 standard</a>,
it is officially standardized as std::bfloat16_t. Its support could be found
in many modern hardware, ranging from CPUs of all the major vendors
including Intel, AMD, Apple, and Amazon, to GPUs (nVidia and AMD GPUs) and
Google TPUs. On the software side, it is supported in all major accelerator
libraries, such as CUDA, ROCm, oneAPI, PyTorch, and Tensorflow. The goal for
this project is to implement bfloat16 math functions in the LLVM libc
library.
</p>
<p><b>Expected result:</b></p>
<ul>
<li> Setup the generated headers properly so that the type and the functions
can be used with various compilers (+versions) and architectures. </li>
<li> Implement generic basic math operations supporting bfloat16 data types
that work on supported architectures: x86_64, arm (32 + 64), risc-v
(32 + 64), and GPUs. </li>
<li> Implement specializations using compiler builtins or special hardware
instructions to improve their performance whenever possible. </li>
<li> If time permits, we can start investigating higher math functions for
bfloat16. </li>
</ul>
<p><b>Skills:</b></p>
<p>
Basic C & C++ skills + Interest in knowing / learning more about the
delicacy of floating point formats.
</p>
<p><b>Project size:</b> Large </p>
<p><b>Difficulty:</b> Easy/Medium </p>
<p><b>Confirmed Mentors:</b>
<a href="mailto:[email protected]">Tue Ly</a>,
<a href="mailto:[email protected]">Nicolas Celik</a>,
</p>
<p><b>Discourse:</b>
<a href="https://discourse.llvm.org/t/libc-gsoc-2025-bfloat16-in-llvm-libc/84469">URL</a>
</p>
</div>
<!-- *********************************************************************** -->
<div class="www_subsubsection">
<a name="io_uring-libc">Direct I/O from the GPU with io_uring</a>
</div>
<!-- *********************************************************************** -->
<div class="www_text">
<p><b>Description:</b></p>
<p>
Modern GPUs are capable of unified addressing with the host. We currently use
this to provide I/O support using the <a href="https://libc.llvm.org/gpu/rpc.html">RPC interface</a>. However, this
requires a dedicated user thread on the CPU to handle the server code. We want
to explore alternatives to providing I/O from the GPU using the Linux
<a href="https://en.wikipedia.org/wiki/Io_uring">io_uring</a> interface.
</p>
<p>
This interface is a ring buffer designed to accelerate syscalls. However, it
provides a <a href="https://unixism.net/loti/tutorial/sq_poll.html#sq-poll">polling mode</a>
that allows the kernel to flush the ring buffer without the user initiating a
system call. We should be able to register <code>mmap()</code> memory with the
GPU using <a href="https://github.com/ROCm/ROCR-Runtime/blob/amd-staging/runtime/hsa-runtime/inc/hsa_ext_amd.h#L3022">AMD</a>
and <a href="https://docs.nvidia.com/cuda/cuda-driver-api/group__CUDA__UNIFIED.html">NVIDIA</a>
API calls. This interface should allow us to implement a rudimentary
read/write interface which can be thought of as the same as the syscall on the
CPU. That can then be used to implement a whole file interface.
</p>
<p><b>Expected result:</b></p>
<ul>
<li>An implementation of <code>pwrite</code> and <code>pread</code> that runs on the GPU.</li>
<li>Support for <code>printf</code> by forwarding <code>snprintf</code> into <code>pwrite</code>.</li>
<li>If time permits, exploring GPU file APIs.</li>
</ul>
<p><b>Skills:</b></p>
<p>
Basic C & C++ skills + access to a GPU, Linux kernel knowledge, GPU knowledge.
</p>
<p><b>Project size:</b> Small </p>
<p><b>Difficulty:</b> Hard </p>
<p><b>Confirmed Mentors:</b>
<a href="mailto:[email protected]">Joseph Huber</a>,
<a href="mailto:[email protected]">Tian Shilei</a>
</p>
<p><b>Discourse:</b>
<a href=https://discourse.llvm.org/t/libc-gsoc-2025-direct-i-o-from-the-gpu-with-io-uring/84569>URL</a>
</p>
</div>
<!-- *********************************************************************** -->
<div class="www_subsubsection">
<a name="testing-math-libc">Profiling and testing the LLVM libc GPU math</a>
</div>
<!-- *********************************************************************** -->
<div class="www_text">
<p><b>Description:</b></p>
<p>
The LLVM C library provides implementations of math functions. We want to profile these against existing implementations,
such as CUDA's <code>libdevice</code>, ROCm's <code>device libs</code>, and OpenCL's <code>libclc</code>.
Last year we worked on some interfaces to support these tests, now they need to be refined and filled out for the interesting functions.
</p>
<p>
Additionally, we want to verify the accuracy of these functions when run on the GPU via brute force testing.
The goal is to verify that the implementations are correct and at least conformant to the error ranges in the
<a href="https://registry.khronos.org/OpenCL/specs/3.0-unified/html/OpenCL_C.html#relative-error-as-ulps">OpenCL standard</a>.
This will require a set of unit tests written in the <code>offload/</code> project, ideally using the new API that @callumfare is working on.
</p>
<p><b>Expected result:</b></p>
<ul>
<li>Final performance results similar to <a href="https://dl.acm.org/doi/fullHtml/10.1145/3624062.3624166">Old results</a>
but with the more optimized functions and higher accuracy.</li>
<li>A test suite that can do brute force testing to confirm that the implementations are conformant.</li>
</ul>
<p><b>Skills:</b></p>
<p>
Basic C & C++ skills + access to a GPU, some math knowledge
</p>
<p><b>Project size:</b> Small </p>
<p><b>Difficulty:</b> Easy / Medium </p>
<p><b>Confirmed Mentors:</b>
<a href="mailto:[email protected]">Joseph Huber</a>,
<a href="mailto:[email protected]">Tue Ly</a>
</p>
<p><b>Discourse:</b>
<a href=https://discourse.llvm.org/t/libc-gsoc-2025-profiling-and-testing-of-the-llvm-libc-gpu-math/84570>URL</a>
</p>
</div>
<!-- *********************************************************************** -->
<div class="www_subsubsection">
<a name="clangir-codegen-tests">Validate existing Clang CodeGen test coverage with ClangIR</a>
</div>
<!-- *********************************************************************** -->
<div class="www_text">
<p><b>Description:</b>
The <a href="https://clangir.org">ClangIR</a> (CIR) project aims to
establish a new intermediate representation (IR) for Clang. Built on top of
MLIR, it provides a dialect for C/C++ based languages in Clang, and the
necessary infrastructure to emit it from the Clang AST, as well as a
lowering path to the LLVM-IR dialect. ClangIR <a href="https://discourse.llvm.org/t/rfc-upstreaming-clangir/76587">upstreaming</a>
is currently in progress.
</p><p>
In order to give community more frequent updates it'd be great if we can
report ClangIR progress by measuring the coverage of existing Clang's
CodeGen tests in face of a ClangIR enabled pipeline. By collecting
information on crashing, passing or failing tests we can come up with a
metric that is easier to report and understand, provide entry points for
newcomers looking for tasks and help the project by classifying existing issues.
Existing Clang CodeGen tests live in clang/test/CodeGen* and can be found
in different states regarding ClangIR support:
<ul>
<li><b>FileCheck fails</b>. LLVM IR builds but FileCheck fails to match output
<ul>
<li> LLVM IR differs because ClangIR pipeline is emitting different IR
(e.g. different instructions are used, missing attributes). Issues
need to be created and ClangIR needs to be fixed. </li>
<li> LLVM IR differs because CHECK lines need be made more flexible (LLVM-IR
dialect output is different, SSA value names, order of attributes, etc).
It's possible a tool like llvm-canon might be of good use here. </li>
</ul></li>
<li><b>Test crash / error</b>. ClangIR doesn't support some C/C++ construct or LLVM lowering
hasn't been implemented.</li>
<li><b>Test pass</b>. Yay!</li>
</ul>
<p>
In order to retrieve the information above, the student needs to make
changes to Clang's testing infra (LIT configs, scripts, tests, ???)
such that it's easier to replay the same invocations with ClangIR enabled,
compare against traditional pipeline result or retrieve special directives
from tests.
</p>
<p>
It's not clear what is the best methodology just yet, but it's
expected that submitted proposals that want to be taken seriously should
present few possible ideas on how to achieve this, prior discussion with
other members of the community is encouraged. The student is also expected
to interact with the ClangIR community, file github issues, investigate
and/or make changes to failing codegen tests.
</p>
<p><b>Expected result:</b>
<ol>
<li>Build the infrastructure to run tests and collect results.</li>
<li>Present the results in a way that can be placed on a webpage.</li>
<li>File issues or change check lines for 50% of the "FileCheck fails" category
above. The only subdirectories that need consideration for the moment are:
<pre>
clang/test/CodeGen
clang/test/CodeGenCXX
clang/test/CodeGenOpenCL
clang/test/CodeGenCUDA
</pre>
</li>
</ol>
<ul>
<li> Bonus point: find ways to automate/facilitate changes to tests, put PRs to
fix problems in ClangIR.</li>
</ul>
</p>
<p><b>Skills:</b>
Python, intermediate C++ programming skills and familiarity with basic compiler
design concepts are required. Prior experience with LLVM IR, MLIR, Clang or
ClangIR programming is a big plus, but willingness to learn is also a
possibility.
</p>
<p><b>Project size:</b> Large</p>
<p><b>Difficulty:</b>Medium</p>
<p><b>Potential Mentors:</b>
<a href="https://github.com/bcardosolopes">Bruno Cardoso Lopes</a>
<a href="https://github.com/andykaylor">Andy Kaylor</a>
</p>
<p><b>Discourse:</b>
<a href="https://discourse.llvm.org/t/clangir-gsoc2025-validate-existing-clang-codegen-test-coverage-with-clangir/84481">URL</a>
</p>
</div>
<!-- *********************************************************************** -->
<div class="www_subsubsection">
<a name="clangir-upstreaming">Participate in ClangIR Upstreaming</a>
</div>
<!-- *********************************************************************** -->
<div class="www_text">
<p><b>Description:</b>
<a href="https://clangir.org">ClangIR</a> is a new, MLIR_based intermediate
representation of C and C++ code. It has been developed in an LLVM incubator
project, but work is now underway to migrate the code from the incubator to
the main LLVM repository. As the code is moved, it must be updated to align
with LLVM coding standards and quality expectations. The goal for this
project is to participate in the ClangIR upstreaming process and help
improve both the code and the upstreaming process.
</p><p>
The ClangIR project intends to unlock the possibility of better
optimization, analysis, and diagnostics for C and C++ code by adding new
abstractions that more closely model the source constructs, preserving
more details than are available in standard LLVM IR. The ClangIR dialect
is already being used to solve real-world problems using the implementation
available in the ClangIR incubator, but we need to move this into the
main LLVM repository in order to make this functionality available to a
larger audience.
</p><p>
This project will be an opportunity to gain hands-on experience with MLIR
development with a focus on day-to-day software engineering discipline.
Participants will work side-by-side with other LLVM contributors to achieve
a common goal, and in the process will gain a deep understanding of the
ClangIR dialect.
</p>
<p><b>Expected result:</b>
<ol>
<li>Migrate ClangIR support for C and C++ language features into the main
LLVM repository</li>
<li>Improve the quality of code as it is being migrated</li>
<li>Suggest ways to improve the migration process</li>
</ol>
</p>
<p><b>Skills:</b>
Proficiency with modern C++ programming and familiarity with basic compiler
design concepts are required. Prior experience with LLVM IR, MLIR, Clang or
ClangIR programming is a big plus, but since the goal of this project is to
gain such experience, it is not a prerequisite.
</p>
<p><b>Project size:</b> Medium to Large</p>
<p><b>Difficulty:</b>Medium</p>
<p><b>Potential Mentors:</b>
<a href="https://github.com/andykaylor">Andy Kaylor</a>
<a href="https://github.com/bcardosolopes">Bruno Cardoso Lopes</a>
</p>
<p><b>Discourse:</b>
<a href="https://discourse.llvm.org/t/clangir-gsoc-2025-clangir-upstreaming/84766">URL</a>
</p>
</div>
<!-- *********************************************************************** -->
<div class="www_subsubsection">
<a name="csa-lifetime-annotations">Teach the Clang Static Analyzer to understand lifetime annotations</a>
</div>
<!-- *********************************************************************** -->
<div class="www_text">
<p><b>Description:</b>
The <a href="https://clang.llvm.org/docs/ClangStaticAnalyzer.html">Clang Static Analyzer</a> (CSA)
can already find a wide range of temporal memory errors. These checks often have hardcoded
knowledge about the behavior of some APIs. For example, the <code>cplusplus.InnerPointer</code> checker knows
the semantics of <code>std::string::data</code>. The Clang community introduced some lifetime
annotations including <code>[[clang::lifetimebound]]</code> and <code>[[clang::lifetime_capture_by(X)]]</code>
and made <a href="https://discourse.llvm.org/t/lifetime-analysis-improvements-in-clang/81374">many improvements</a>
to Clang's default warnings. Unfortunately, the compiler's warnings only do statement local analysis.
The CSA is capable of advanced inter-procedural analysis. Generalizing the existing checks like
<code>cplusplus.InnerPointer</code> could enable the analyzer to find even more errors in annotated code.
This can become even more impactful once the standard library
<a href="https://github.com/llvm/llvm-project/pull/112751">gets annotated</a>.
</p>
<p><b>Expected result:</b>
<ol>
<li>Identify the checks that can benefit from the <code>[[clang::lifetimebound]]</code> and <code>[[clang::lifetime_capture_by(X)]]</code> annotations.</li>
<li>Extend those checks to support these annotations.</li>
<li>Make sure the generated bug reports are high quality, the diagnostics properly explain how the analyzer took these annotations into account.</li>
<li>Validate the results on real world projects.</li>
<li>Potentially warn about faulty annotations (stretch goal).</li>
</ol>
</p>
<p><b>Skills:</b>
Intermediate C++ programming skills and familiarity with basic compiler
design concepts are required. Prior experience with Clang or
CSA programming is a big plus, but willingness to learn is also a
possibility.
</p>
<p><b>Project size:</b> Large</p>
<p><b>Difficulty:</b>Hard</p>
<p><b>Potential Mentors:</b>
<a href="https://github.com/Xazax-hun">Gabor Horvath</a>
<a href="https://github.com/steakhal">Balazs Benics</a>
<a href="https://github.com/isuckatcs">Daniel Domjan</a>
</p>
<p><b>Discourse:</b>
<a href="https://discourse.llvm.org/t/clang-static-analyzer-gsoc-2025-teach-the-clang-static-analyzer-to-understand-lifetime-annotations/84487">URL</a>
</p>
</div>
<!-- *********************************************************************** -->
<div class="www_subsubsection">
<a name="clang-driver-modules">Simple C++20 modules without a build system</a>
</div>
<!-- *********************************************************************** -->
<div class="www_text">
<p><b>Description</b></p>
<p>Currently there is no easy way to take a collection of source files using C++20 modules and build an executable from them. This makes it hard to create simple tests or tiny programs using C++20 modules without first setting up a build system. This project's goal is to extend the extremely simple build system in Clang's driver to handle these cases.</p>
<p>This can be done by using Clang's existing support for scanning for C++20 modules to discover the dependencies between the source files that have been passed in, and then build them in that order, passing in the right PCM files where needed. This may also be extended to support explicitly building Clang modules discovered via module map files too.</p>
<p><b>Expected outcomes</b></p>
<p>Invoking clang similarly to <pre>clang -o program -std=c++20 main.cpp A.cppm B.cppm</pre> should compile successfully where each translation-unit only imports modules defined in other source files on the command line, or the standard library. This should add no overhead to cases where modules are not used.</p>
<p><b>Confirmed mentors and their contacts</p></b>
<ul>
<li><a href="https://github.com/Bigcheese">Michael Spencer</a></li>
</ul>
<p><b>Required skills</b></p>
<p>Intermediate knowledge of C++; familiarity with how C++ code is built. Familiarity with C++20 modules is an asset, but not required.</p>
<p><b>Size of the project:</b></p>
<p>medium (~175h)</p>
<p><b>Project difficulty:</b></p>
<p>medium</p>
<p><b>Discourse:</b> <a href="https://discourse.llvm.org/t/clang-gsoc-2025-support-simple-c-20-modules-use-from-the-clang-driver-without-a-build-system/84511">URL</a></p>
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<a name="clang-improve-trapping-ubsan-2025">Usability Improvements for trapping Undefined Behavior Sanitizer (UBSan)</a>
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<p><b>Description</b></p>
<p>Undefined Behavior Sanitizer (UBSan) is a useful compilation mode in Clang for finding uses of undefined behavior (e.g. signed integer overflow) and problematic C/C++ code (e.g. unsigned integer overflow). The default version of UBSan uses a compiler runtime that only works in userspace (e.g. it won’t work in the kernel or for embedded applications) and is not considered secure enough for use in production environments. To handle these other environments UBSan provides a trapping mode that emits trap instructions that immediately halts the application rather than calling into the UBSan runtime which normally diagnoses the problem and then carries on execution.</p>
<p>Unfortunately trapping UBSan has some deficiencies which make it hard to use. In particular:</p>
<ul>
<li>Clang silently ignores the <tt>-fsanitize-trap=undefined</tt> flag when it's passed without <tt>-fsanitize=undefined</tt>. This project would fix this as a “warm up task” to get familiar with the Clang codebase.</li>
<li>When a UBSan trap is hit with the debugger attached it is not convenient to figure out the reason UBSan trapped. For x86_64 and arm64 some information is encoded in the instruction but decoding this is very inconvenient. While LLDB could be taught to look at the instruction and decode the meaning this is brittle because it depends on undocumented compiler ABI. Instead we can build upon the <tt>__builtin_verbose_trap</tt> work to encode the reason for trapping ("trap reasons") inside the debug information. If time permits we can also investigate emitting more precise trap reasons</li>
</ul>
<p><b>Expected outcomes</b></p>
<ul>
<li>When the <tt>-fsanitize-trap=undefined</tt> flag is passed on its own the compiler silently ignores it. Currently Clang requires that the <tt>-fsanitize-trap=</tt> flag is also passed. Clang should be taught to warn about this.</li>
<li>Teach Clang to emit the UBSan trap reasons in debug information on UBSan trap instructions similar to how <tt>__builtin_verbose_trap</tt> works.</li>
<li>Confirm LLDB is able to recognize the UBSan trap reasons and add tests for this.</li>
<li>If time permits we should investigate emitting more precise trap reasons by using information available in the compiler. We may want to implement a "Sema Diagnostic" like approach where trap reason strings can easily be constructed inside the compiler. This task is more open-ended and has potentially uses outside of UBSan (e.g. <tt>-fbounds-safety</tt>).</li>
</ul>