The zlib-rs team added AVX-512 SIMD intrinsic support to Miri, Rust's interpreter for detecting undefined behavior, enabling CI testing of AVX-512 code without requiring AVX-512 hardware. Since QEMU doesn't support AVX-512 and Intel's own emulator is slow, the team contributed four new intrinsic implementations to Miri: `_mm512_sad_epu8`, `_mm512_ternarylogic_epi32`, `_mm512_maddubs_epi16`, and `_mm512_permutexvar_epi32`. These are wider variants of already-supported instructions, so implementations share code with narrower AVX2 versions. The post walks through the implementation process using `psadbw` as a detailed example, showing how Miri shims map LLVM intrinsic names to Rust interpreter logic. The AVX-512 optimizations (for compare256, crc32, and adler32) are available in zlib-rs 0.5.3, requiring Rust 1.89+ and appropriate target feature flags.
