Bit manipulation instructions: Difference between revisions

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* The [[AVX-512#Bitwise ternary logic|AVX-512 ternary]] extension includes a [[Bitwise ternary logic instruction]], {{code|vpternlog}}. Also noteworthy is a conflict detection instruction. [[AVX-512#Conflict detection|<code>VPCONFLICTD</code>]]

* Also present in the AVX/[[AVX-512]] [[GFNI instruction set|GFNI subset]] is bit-matrix affine transformation and its inverse: {{code|GF2P8AFFINEQB}} is effectively an 8x8 bit-matrix multiply in the [[Galois field]] GF(2^8).<ref>{{cite web | title=GF2P8AFFINEQB — Galois Field Affine Transformation | url=https://www.felixcloutier.com/x86/gf2p8affineqb }}</ref>

* AVX-512 BITALG besides AVX-512 version of existing bit manipulation instruction, also added {{code|VPSHUFBITQMB}} which is a bit-level shuffle instruction, that picks bits from one source using indexes in the second source.

* An Intel GNFI technology guide on that AVX/AVX512 GNFI Extension also lists numerous uses including parallel byte-wise set/clear/invert bitmanipulation, 5-bit sign-extension and points out the potential is much greater.<ref name=gfni>{{cite web |title=Galois Field New Instructions (GFNI) Technology Guide |url=https://networkbuilders.intel.com/solutionslibrary/galois-field-new-instructions-gfni-technology-guide |website=networkbuilders.intel.com |language=en}}</ref>

* [[Intel BCD opcodes]]

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=== RISC-V ===

In the standard extensions RISC-V has scalar [[bitwise operations]] including shift and arithmetic shift, but no rotate. The omissions are compensated for with additional extensions.

* [[RISC-V]] Zb* extensions contain a significant number of bit manipulation instructions.<ref>{{cite web | title=Riscv-bitmanip/Bitmanip/Index.adoc at main · riscv/Riscv-bitmanip | website=[[GitHub]] | url=https://github.com/riscv/riscv-bitmanip/blob/main/bitmanip/index.adoc }}</ref> The four groups are broken down into useful categories (the integer subset has min/max, rotate and [[Popcount]] for example), and have very good well-researched justifications for their inclusion and the improvements they bring.<ref>{{cite web | title=Riscv-bitmanip/Bitmanip/Overview.adoc at main · riscv/Riscv-bitmanip | website=[[GitHub]] | url=https://github.com/riscv/riscv-bitmanip/blob/main/bitmanip/overview.adoc }}</ref>

* The RISC-V Vector Extension (RVV) has instructions that qualify as hardware-level bit manipulation, but on Vector masks rather than Scalar registers as is normally the case. For example, a Vector-mask [[Popcount]] is available.<ref>{{cite web | title=Riscv-v-spec/V-spec.adoc at master · riscvarchive/Riscv-v-spec | website=[[GitHub]] | url=https://github.com/riscvarchive/riscv-v-spec/blob/master/v-spec.adoc#15-vector-mask-instructions }}</ref> RVV also has per-element [[bitwise operations]].<ref>{{cite web | title=Riscv-v-spec/V-spec.adoc at master · riscvarchive/Riscv-v-spec | website=[[GitHub]] | url=https://github.com/riscvarchive/riscv-v-spec/blob/master/v-spec.adoc#115-vector-bitwise-logical-instructions }}</ref>