Open Source

I like to contribute to open source, here are links to some of my contributions 🙏

LLVM

Repository: llvm/llvm-project
GitHub: @chaitanyav
Period: March 2023 – May 2026

1️⃣ C23/C2y Standard Library Builtins

🟢 Typed Variants for C2y stdbit.h Rotate Builtins (May 2026)

PR #195299 | Merged May 12, 2026 | C2y Language Feature

Extended the rotate builtin work from PR #160259 by adding typed variants for __builtin_stdc_rotate_left and __builtin_stdc_rotate_right following the C2y stdbit.h specification:

  • stdc_rotate_left_{uc,us,ui,ul,ull} — typed left rotate for each unsigned integer type
  • stdc_rotate_right_{uc,us,ui,ul,ull} — typed right rotate for each unsigned integer type

Technical Approach:

  • ✅ Complements the type-generic rotate builtins from PR #160259
  • ✅ Follows the same pattern as the C23 typed stdbit.h variants (PR #192718)
  • ✅ Maps to efficient rotate instructions on target architectures

Impact: Advances C2y <stdbit.h> support, providing both type-generic and type-specific rotate interfaces.

🟢 Remove non-builtin generic stdbit.h bit functions (May 2026)

PR #197069 | Merged May 11, 2026 | NFC / Cleanup

Removed the non-builtin generic <stdbit.h> bit functions, consolidating the implementation to use only the builtin variants introduced in earlier PRs.

Impact: Simplifies the <stdbit.h> implementation by eliminating redundant non-builtin paths, reducing maintenance surface.

🟢 Typed Variants for C23 stdbit.h Builtins (April 2026)

PR #192718 | Merged April 21, 2026 | C23 Language Feature

Added typed variants of the C23 bit manipulation builtins following the stdbit.h specification. Typed functions for specific unsigned integer types:

  • stdc_leading_zeros_{uc,us,ui,ul,ull} – Leading zeros for unsigned char, unsigned short, unsigned int, unsigned long, unsigned long long
  • stdc_leading_ones_{uc,us,ui,ul,ull} – Leading ones
  • stdc_trailing_zeros_{uc,us,ui,ul,ull} – Trailing zeros
  • stdc_trailing_ones_{uc,us,ui,ul,ull} – Trailing ones
  • stdc_first_leading_zero_{uc,us,ui,ul,ull} – First leading zero position
  • stdc_first_leading_one_{uc,us,ui,ul,ull} – First leading one position
  • stdc_first_trailing_zero_{uc,us,ui,ul,ull} – First trailing zero position
  • stdc_first_trailing_one_{uc,us,ui,ul,ull} – First trailing one position
  • stdc_count_zeros_{uc,us,ui,ul,ull} – Count of zero bits
  • stdc_count_ones_{uc,us,ui,ul,ull} – Count of one bits
  • stdc_has_single_bit_{uc,us,ui,ul,ull} – Check if power of two
  • stdc_bit_width_{uc,us,ui,ul,ull} – Bit width
  • stdc_bit_floor_{uc,us,ui,ul,ull} – Largest power of 2 ≤ value
  • stdc_bit_ceil_{uc,us,ui,ul,ull} – Smallest power of 2 ≥ value

Technical Approach:

  • ✅ Complements the type-generic _builtin_stdc* implementations from PR #185978
  • ✅ Provides C23-compliant typed interface matching the standard library specification
  • ✅ Maps to the same underlying intrinsics (ctlz, cttz, ctpop) with type-specific wrappers

Impact: Completes C23 <stdbit.h> implementation, allowing both type-generic and type-specific bit manipulation functions.

🟢 _builtin_stdc* Bit Manipulation Builtins (April 2026)

PR #185978 | Merged April 16, 2026 | C23 Language Feature

Implemented the C23 bit manipulation builtins following the ISO C23 standard specification:

  • __builtin_stdc_leading_zeros() / __builtin_stdc_leading_ones()
  • __builtin_stdc_trailing_zeros() / __builtin_stdc_trailing_ones()
  • __builtin_stdc_first_leading_zero() / __builtin_stdc_first_leading_one()
  • __builtin_stdc_first_trailing_zero() / __builtin_stdc_first_trailing_one()
  • __builtin_stdc_count_zeros() / __builtin_stdc_count_ones()
  • __builtin_stdc_has_single_bit()
  • __builtin_stdc_bit_width() / __builtin_stdc_bit_floor() / __builtin_stdc_bit_ceil()

Technical Approach:

  • ✅ Designed for GCC compatibility while leveraging LLVM’s existing intrinsics (ctlz, cttz, ctpop)
  • ✅ Type-generic implementation supporting all unsigned integer types
  • ✅ Integration with Clang’s constant expression evaluator

Impact: Enables C23-compliant portable bit manipulation without vendor-specific intrinsics.

🟢 Rotate Builtins (January 2026)

PR #160259 | Merged January 21, 2026 | C23 Language Feature

Implemented __builtin_stdc_rotate_left() and __builtin_stdc_rotate_right():

  • Type-generic support for all unsigned integer types including _BitInt(N)
  • Compile-time evaluation in constexpr contexts
  • Maps to efficient rotate instructions on target architectures

Handling ARM32 compatibility issues with __int128 types required careful test design and fallback to _BitInt(128) (PR #177290, PR #177732).

2️⃣ Constexpr SIMD Intrinsics

Between October 2025 and February 2026, I systematically enabled compile-time evaluation for X86 SIMD intrinsics across multiple instruction set extensions. This work allows these intrinsics to be used in constexpr contexts, enabling better compile-time optimization and static analysis.

🔵 AVX-512 Advanced Intrinsics

AVX-512 VPMULTISHIFTQB (November 2025)
PR #168995 | Resolves #167477 | AVX-512 Constexpr

Multi-byte shift operations with compile-time evaluation support.

  • _mm512_multishift_epi64_epi8, _mm512_mask_multishift_epi64_epi8, _mm512_maskz_multishift_epi64_epi8
  • _mm256_multishift_epi64_epi8, _mm256_mask_multishift_epi64_epi8, _mm256_maskz_multishift_epi64_epi8
  • _mm_multishift_epi64_epi8, _mm_mask_multishift_epi64_epi8, _mm_maskz_multishift_epi64_epi8

AVX-512 VPSHUFBITQMB (November 2025)
PR #168100 | Resolves #161337 | AVX-512 Constexpr

Bit shuffle operations for cryptographic and data manipulation workloads.

  • _mm512_bitshuffle_epi64_mask, _mm512_mask_bitshuffle_epi64_mask
  • _mm256_bitshuffle_epi64_mask, _mm256_mask_bitshuffle_epi64_mask
  • _mm_bitshuffle_epi64_mask, _mm_mask_bitshuffle_epi64_mask

AVX-512 Conflict Detection (October 2025)
PR #163293 | Resolves #160524 | AVX-512 Constexpr

Enables conflict detection intrinsics in constexpr contexts for identifying duplicate elements.

  • _mm512_conflict_epi32, _mm512_mask_conflict_epi32, _mm512_maskz_conflict_epi32
  • _mm512_conflict_epi64, _mm512_mask_conflict_epi64, _mm512_maskz_conflict_epi64

AVX-512 IFMA (October 2025)
PR #161056 | Resolves #160498 | AVX-512 AVX-IFMA Constexpr

Integer fused multiply-add (madd52) support for large integer arithmetic.

  • AVX-512: _mm512_madd52hi_epu64, _mm512_madd52lo_epu64 (and mask/maskz variants)
  • AVX-IFMA: _mm256_madd52hi_epu64, _mm256_madd52lo_epu64, _mm_madd52hi_epu64, _mm_madd52lo_epu64 (and mask/maskz variants)

🟣 AVX-512 Permutation & Shuffle Operations

Permutexvar Intrinsics (November 2025)
PR #167802 | Resolves #167476 | AVX-512 Permutation Constexpr

Variable permutation operations across vector lanes.

  • _mm512_permutexvar_epi8/epi16/epi32/epi64/ps/pd (and mask/maskz variants)
  • _mm256_permutexvar_epi8/epi16/epi32/epi64/ps/pd (and mask/maskz variants)

Permutex2var Intrinsics (November 2025)
PR #165085 | AVX-512 Permutation Constexpr

Two-source permutation with extended shuffle generic support.

  • _mm512_permutex2var_epi8/epi16/epi32/epi64/ps/pd (and mask/maskz variants)
  • _mm256_permutex2var_epi8/epi16/epi32/epi64/ps/pd (and mask/maskz variants)
  • _mm_permutex2var_epi8/epi16/epi32/epi64/ps/pd (and mask/maskz variants)

🟢 SSE/AVX Fundamental Operations

Shuffle Operations (October 2025)
PR #164078 | Resolves #161208 | SSE AVX AVX-512 Constexpr

Fundamental shuffle operations used in nearly all vectorized code.

  • SSE: _mm_shuffle_ps
  • SSE2: _mm_shuffle_pd
  • AVX: _mm256_shuffle_ps, _mm256_shuffle_pd
  • AVX-512: All corresponding mask/maskz variants for 512-bit vectors

GFNI Intrinsics (December 2025)
PR #169619 | Resolves #169295 | GFNI Cryptographic Constexpr

Galois Field New Instructions for cryptographic applications.

  • _mm512_gf2p8affineinv_epi64_epi8, _mm512_gf2p8affine_epi64_epi8, _mm512_gf2p8mul_epi8 (and mask/maskz variants)
  • _mm256_gf2p8affineinv_epi64_epi8, _mm256_gf2p8affine_epi64_epi8, _mm256_gf2p8mul_epi8 (and mask/maskz variants)
  • _mm_gf2p8affineinv_epi64_epi8, _mm_gf2p8affine_epi64_epi8, _mm_gf2p8mul_epi8 (and mask/maskz variants)

Variable Shift Operations (November 2025)
PR #169276 | Resolves #169176 | SSE AVX AVX-512 Constexpr

Variable shift intrinsics (shift amount per element).

  • Logical left: _mm512_sllv_epi16/epi32/epi64, _mm256_sllv_epi16/epi32/epi64, _mm_sllv_epi16/epi32/epi64 (and mask/maskz variants)
  • Arithmetic right: _mm512_srav_epi16/epi32/epi64, _mm256_srav_epi16/epi32/epi64, _mm_srav_epi16/epi32/epi64 (and mask/maskz variants)
  • Logical right: _mm512_srlv_epi16/epi32/epi64, _mm256_srlv_epi16/epi32/epi64, _mm_srlv_epi16/epi32/epi64 (and mask/maskz variants)

Floating-Point Min/Max (January 2026)
PR #171966 | SSE AVX AVX-512 FP16 Constexpr

Vector FP maximum/minimum operations across SSE/AVX families.

  • SSE: _mm_min_ps, _mm_max_ps, _mm_min_pd, _mm_max_pd
  • AVX: _mm256_min_ps, _mm256_max_ps, _mm256_min_pd, _mm256_max_pd
  • AVX-512: _mm512_min_ps, _mm512_max_ps, _mm512_min_pd, _mm512_max_pd (and mask/maskz variants)
  • AVX-512 FP16: _mm512_min_ph, _mm512_max_ph, _mm256_min_ph, _mm256_max_ph, _mm_min_ph, _mm_max_ph (and mask/maskz variants)

Scalar Min/Max with AVX-512 FP16 (February 2026)
PR #178029 | SSE SSE2 AVX-512 FP16 Constexpr

Extended scalar operations including new FP16 intrinsics:

  • SSE scalar single-precision: _mm_min_ss, _mm_max_ss
  • SSE2 scalar double-precision: _mm_min_sd, _mm_max_sd
  • AVX-512 FP16 scalar: _mm_min_sh, _mm_max_sh (and mask/maskz variants)

Implementation Approach:

  • ✅ Extended VectorExprEvaluator::VisitCallExpr and InterpretBuiltin evaluation paths
  • ✅ Added comprehensive test coverage for NaN, denormal, infinity, and rounding mode edge cases (PR #180013)
  • ✅ Handled special cases: saturation boundaries, broadcast patterns, cross-lane operations

3️⃣ SelectionDAG Optimizations

🟢 computeKnownFPClass SELECT/VSELECT Handling (April 2026)

PR #194009 | Fixes #193500 | Merged April 30, 2026 | SelectionDAG Optimization

Extended SelectionDAG::computeKnownFPClass to handle ISD::SELECT and ISD::VSELECT nodes, propagating floating-point class information (e.g. nofpclass(nan), nofpclass(inf), nofpclass(zero)) through select operations.

Technical Approach:

  • ✅ Computes KnownFPClass for both true and false arms of a select, then intersects the results
  • ✅ Bails out early if the false arm is fully unknown, avoiding unnecessary work
  • ✅ Covers scalar SELECT, fixed-vector VSELECT, and scalable-vector VSELECT
  • ✅ Comprehensive RISC-V test coverage for symmetric, asymmetric, and unknown-arm cases

Impact: Enables the backend to eliminate redundant is.fpclass checks on select results when both arms share a known FP class constraint, reducing generated code size and improving optimization quality.

4️⃣ Early Work: Tooling & API Improvements (2023)

Clang ExtractAPI Enhancements

A series of fixes to Clang’s API documentation extraction:

Objective-C Lightweight Generics (March–May 2023)
PRs: Declaration fragments, pointer indirection, instancetype handling
Fixed ExtractAPI’s handling of Objective-C generics for accurate API documentation generation.

Declaration Fragment Completeness (March 2023)
Added missing semicolons to function, enum, typedef, and struct declaration fragments for syntactically complete generated documentation.

Clang-Tidy Improvements (May 2023)

Extended error code checking to all functions with error-like return types:

  • std::error_code, std::expected
  • boost::system::error_code
  • absl::Status

Helps catch ignored error conditions across multiple libraries.

libc++ Enhancements (October 2025)

PR #162030

Added compile-time assertion to std::string::resize_and_overwrite() verifying the operation returns an integer-like type, improving template error messages and preventing misuse.

🔗 Resources

All Commits on GitHub

Rust

Commits

FreeBSD

Scala tools, compiler (2.13.x)

FFmpeg

RubyGems

RubyOnRails Contribution

📬 Connect

I’m actively contributing to LLVM and exploring compiler engineering opportunities. If you’re working on interesting compiler problems — especially in optimization, code generation, or language implementation — I’d love to connect.

Contact: ✉️ moc.liamnotorp@otaganp ✉️

GitHub: @chaitanyav