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whisper.cpp

Author: Ludovic HENRY ludovic.henry@qti.qualcomm.com
Date: 2026-09-07
Readiness: yellow
Scope: RISC-V (riscv64/linux) support status for whisper.cpp
Audience: Technical leadership, resource allocation strategy
Verification policy: Every claim is cross-referenced to a primary upstream source. Items that could not be verified against a second source are marked [NEEDS VERIFICATION].

1. Project Overview

whisper.cpp is a C/C++ port of OpenAI’s Whisper automatic speech recognition (ASR) model, created and led by Georgi Gerganov, hosted under the ggml-org GitHub organization (his own venture, ggml.ai; the repository was renamed/transferred from ggerganov/whisper.cpp during the research period). It is MIT-licensed (“Copyright 2023-2026, The ggml authors”).

Governance. No formal foundation exists: no MAINTAINERS/OWNERS/CODEOWNERS file, no GOVERNANCE.md or FOUNDATION.md, and no affiliation with the Linux Foundation, NumFOCUS, or any other foundation. This is a BDFL-style project: Gerganov holds roughly 1,400 of the top commits, far ahead of any other contributor. CONTRIBUTING.md defines a three-tier policy: Contributors (no special privileges), Collaborators/Triage (own specific code areas), and Maintainers (merge PRs after code-owner approval, and “reserve the right to decline review or close pull requests for any reason, without any questions”). A separate AI-generated-PR policy (CONTRIBUTING.md + AGENTS.md) bars fully/predominantly AI-generated PRs.

Corporate sponsors. No corporate entity formally sponsors whisper.cpp. Because most of its compute core (ggml) is shared with and synced from ggml-org/llama.cpp, top-committer corporate affiliations reflect that shared codebase: Jeff Bolz (NVIDIA, Vulkan backend), Neo Zhang Jianyu (Intel, SYCL backend), Max Krasnyansky (Qualcomm, CPU backend), plus a broader AUTHORS-file domain scan showing Intel (9), Codeplay/Intel subsidiary (6), Red Hat (4), Qualcomm (3), Arm (3), AMD (2), and single contributors from Samsung, Google, NVIDIA, and Hugging Face. No RISC-V vendor employees appear among top overall committers, though SpacemiT-authored commits exist specifically in the RISC-V code path (see Section 2).

Community culture on new ports. whisper.cpp’s own README “Supported platforms” list (Mac OS, iOS, Android, Java, Linux/FreeBSD, WebAssembly, Windows, Raspberry Pi, Docker) and its feature-bullet list (Apple Silicon/NEON, AVX/x86, POWER/VSX, Vulkan, NVIDIA, AMD ROCm, OpenVINO, Ascend, Moore Threads) do not mention RISC-V at all, despite substantial RVV/SpacemiT kernel code existing in the tree. New architecture support generally arrives as sync commits from ggml/llama.cpp rather than as whisper.cpp-native PRs, consistent with the maintainers’ stated preference for long-term-committed contributors who “own” the code they add.

2. Port History and Upstreaming Timeline

Date Event Source
2023-07-16 PR #1101 merged: adds linux/riscv64 to a QEMU/docker-buildx multi-arch CI matrix (not prioritized; the matrix has since been superseded, current docker.yml no longer lists riscv64). Also fixes an #if !defined(__riscv) header-inclusion guard in ggml.c, the earliest RISC-V-adjacent portability fix in the repo. PR #1101
2023-09-05 Commit c3f319d7, “ggml: sync latest llama.cpp”, by Georgi Gerganov - earliest RISC-V-related commit (an upstream sync bringing in early RVV intrinsics, not native work). Repository history
2024-07-22 Commit 0bc8bffe, “ggml: fix compile error for RISC-V (llama/8623)”, by Mark Zhuang - implies RISC-V support already existed upstream by this point. Repository history
2024-09-12 Commit 3f8f8a78, “riscv: modify Makefile and add a RISCV_VECT to print log info (llama/9442)”, by Ahmad Tameem - first feature-level RISC-V commit; adds ggml_cpu_has_riscv_v(). Repository history
2025-03-27 Commit 8ca67df2, “ggml: sync/merge cmake,riscv,powerpc, add common.cmake (ggml/0)”, by Georgi Gerganov - the sync that introduced the intrinsic later reported broken in issue #2989. Repository history
2025-04-02 Issue #2989 opened: __riscv_vcreate_v_i8m1_i8m2 intrinsic fails on GCC 13.2. Issue #2989
2025-05-27 Commit 15ae9dc2, “ggml: riscv: add xtheadvector support (llama/13720)”, by xctan - adds T-Head’s older RVV v0.7.1 vector ISA support. llama.cpp PR #13720
2025-09-03 Commit 75f739c7, “ggml-cpu: optimize RVV kernels (llama/15720)”, by xctan - fixes pipeline stalls in q4_K/q6_K/f32 dot products; +183%/+177% throughput on Qwen3-4B pp512/tg128. llama.cpp PR #15720
2025-09-29/30 Commit 35ebdf73, “ggml: riscv: add riscv spacemit backend (llama/15288)”, by alex-spacemit - adds SpacemiT X60 IME matrix-extension backend, the largest RISC-V feature landed to date. llama.cpp PR #15288
2025-11-29 / 2025-12-12 Commit 28dff065, “ggml: replace hwcap with riscv_hwprobe for RVV detection (llama/17567)”, by Wang Yang. Repository history
2026-03-23 Issue #3717 opened: malformed CMake-generated -march= string rejected by GCC 13.3. Issue #3717
2026-04-16 / 2026-04-30 Commit 07c181b5, “ggml: implemented simd_gemm kernel for riscv vector extension (llama/20627)”, by rehan-10xengineers. Repository history
2026-09-06 / 2026-09-07 Issues #2989 and #3717 both auto-closed by the stale bot as not_planned, with no fix merged in either case. Issue #2989, Issue #3717

Key contributors and orgs: xctan (RVV kernel optimization, xtheadvector support - org not identified in AUTHORS), alex-spacemit (SpacemiT IME backend - SpacemiT), Ahmad Tameem / rehan-10xengineers (10xEngineers-pattern usernames, org affiliation [NEEDS VERIFICATION]), Wang Yang, Mark Zhuang.

Is it fully upstream? All RISC-V code lives in ggml/src/ggml-cpu/arch/riscv/ and ggml/src/ggml-cpu/spacemit/, both vendored into whisper.cpp via periodic sync commits from ggml-org/llama.cpp (visible from the (llama/NNNNN) PR references above). Direct lexical searches for rvv, rv64, xtheadvector, spacemit, riscv_hwprobe in whisper.cpp’s own pull requests returned zero results. whisper.cpp itself has produced no native RISC-V feature PRs - only two CI/build-adjacent PRs touch riscv64 at all (#1101, generic CI matrix work; #2914, Vulkan cross-compile work unrelated to RISC-V, closed without merging).

3. Upstream Support Tier

whisper.cpp’s tier policy (CONTRIBUTING.md) is generic to all contributions, not RISC-V-specific: Contributors -> Collaborators (Triage) -> Maintainers, with maintainers holding final, unqualified discretion to decline or close PRs.

Evidence for riscv64 specifically: no riscv64 CI job exists anywhere in the repository (Section 7), and no riscv64 release-blocking gate exists because no riscv64 CI job exists at all to gate on.

  amd64 arm64 riscv64
CI builds yes (ubuntu-22.04 runner, build-cpu.yml) yes (ubuntu-22.04-arm runner) no
CI tests run yes yes no
Release-blocking yes yes N/A (no CI to gate)
Official binary published yes (whisper-bin-x64.tar.gz, whisper-cublas-*) yes (whisper-bin-ubuntu-arm64.tar.gz) no

4. Technical Architecture and RISC-V-Specific Subsystems

RISC-V support is implemented entirely within the vendored ggml tensor library, in two layers.

Portable RVV baseline (ggml/src/ggml-cpu/arch/riscv/):

  • quants.c (6,596 lines): quantize/dequantize + ggml_vec_dot_* SIMD kernels for nearly every ggml quant format (Q4_0/1, Q5_0/1, Q8_0/1, Q2-Q6_K, IQ1_S/M, IQ2_XXS/XS/S, IQ3_XXS/S, IQ4_NL/XS, MXFP4, TQ1/TQ2_0), with _generic/_vl128/_vl256/_vl512/_xtheadvector vector-length-specialized variants for several quant dot products (e.g. ggml_vec_dot_q3_K_q8_K_vl512), containing 1,744 __riscv_v_* intrinsic calls.
  • repack.cpp (1,703 lines): weight/activation repacking for blocked GEMV/GEMM kernels, 726 more RVV intrinsic calls.
  • cpu-feats.cpp (38 lines): runtime feature detection via the modern riscv_hwprobe syscall (RISCV_HWPROBE_KEY_IMA_EXT_0), feeding the GGML_BACKEND_DL_SCORE_IMPL dynamic-dispatch scorer - functionally on par with x86’s CPUID-based detection.

Vendor-optimized layer (ggml/src/ggml-cpu/spacemit/, ~15,900 lines): a full backend for SpacemiT K1/X60-class SoCs using SpacemiT’s proprietary IME (Integer Matrix Extension) instructions (vmadot, vfwmadot, vpack, vnspack). Files: ime2_kernels.cpp (5,768 lines, IME2 matmul kernels), repack.cpp (1,795 lines), ime.cpp (1,742 lines, dispatch/orchestration), rvv_kernels.cpp (3,178 lines, pure-RVV fallback), ime1_kernels.cpp (1,027 lines), plus memory-pool, topology-detection, and header support files. Gated behind GGML_CPU_RISCV64_SPACEMIT, probed via FindSMTIME.cmake.

ISA extensions used: V (RVV 1.0), Zfh/Zfhmin (scalar half-float), Zvfh/Zvfhmin (vector half-float), Zvfbfwma/Zvfbfmin (vector bf16), Zba, Zicbop, Zihintpause, optional XTheadVector (T-Head vendor ISA), and SpacemiT’s proprietary IME1/IME2 (xsmtvdotii, GCC>=15 only).

Quality: Hand-tuned, not a stub. Only one throwaway code comment (// fixme: use v0p7 mask layout directly) exists anywhere in the RISC-V files; no TODO/stub/unimplemented/placeholder markers were found. Two minor incomplete spots exist in shared (non-riscv-exclusive) files: a // todo: RVV implementation fallback in vec.cpp (~line 9878) and a //TODO: Write SVE code and RVV code scalar-route comment in ggml-cpu.c (~line 11427) - both are single unimplemented sub-cases inside otherwise-complete files, the same partial-coverage pattern every architecture in this codebase has.

Architecture-specific SIMD code, line-count comparison (ggml/src/ggml-cpu/arch/):

Arch quants.c repack.cpp cpu-feats.cpp Total
x86 4,108 6,407 327 10,842
arm 4,319 5,156 41 9,516
riscv 6,596 1,703 38 8,337
powerpc 2,304 - 82 2,386
loongarch 2,309 - - 2,309
s390 1,465 - 50 1,515
wasm 1,292 - - 1,292

RISC-V is the third-largest architecture-specific implementation (ahead of powerpc/loongarch/s390/wasm by 3-5x) and has the largest quants.c of any architecture, including x86 and arm. Combined with the 15,900-line SpacemiT extra backend, total RISC-V-related code is approximately 23,800 lines - a scope of dedicated vendor-extension support that no other non-x86/arm architecture in this codebase receives. No JIT backend exists for any architecture in ggml; all dispatch is compile-time -march flags plus an optional runtime multi-versioning selector (cpu-feats.cpp).

5. Build System, Cross-Compilation, and Toolchain

No BUILDING.md, INSTALL, docs/building.md, or docs/cross-compilation.md exists in the repository, and the README has zero RISC-V content. Everything below was recovered directly from CMake source and code comments.

Cross-compile toolchain file: cmake/riscv64-spacemit-linux-gnu-gcc.cmake requires a RISCV_ROOT_PATH environment variable pointing at a riscv64-unknown-linux-gnu-* toolchain install (unless the build host is itself riscv64). Bakes in -march=rv64gcv_zfh_zba_zicbop -mabi=lp64d and links -latomic.

Exact cross-compile command:

export RISCV_ROOT_PATH=/path/to/riscv64-unknown-linux-gnu-toolchain
cmake -B build -DCMAKE_TOOLCHAIN_FILE=cmake/riscv64-spacemit-linux-gnu-gcc.cmake \
  -DCMAKE_BUILD_TYPE=Release -DGGML_NATIVE=OFF -DWHISPER_SDL2=OFF
cmake --build build -j

Native (on-device) build:

cmake -B build -DCMAKE_BUILD_TYPE=Release
cmake --build build -j$(nproc)

ggml_get_system_arch() auto-detects CMAKE_SYSTEM_PROCESSOR MATCHES "riscv64" and sets GGML_SYSTEM_ARCH=riscv64 with no extra flags required.

Relevant build flags (ggml/CMakeLists.txt): GGML_RVV (ON), GGML_RV_ZFH (ON), GGML_RV_ZVFH (ON), GGML_RV_ZICBOP (ON), GGML_RV_ZIHINTPAUSE (ON), GGML_RV_ZVFBFWMA (OFF), GGML_XTHEADVECTOR (OFF), GGML_CPU_RISCV64_SPACEMIT (opt-in, no default), GGML_CPU_ALL_VARIANTS (OFF; when combined with GGML_BACKEND_DL=ON, builds riscv64_0/riscv64_v runtime-dispatched variants). Only Linux is a supported CMAKE_SYSTEM_NAME for riscv64 - any other OS triggers FATAL_ERROR "Unsupported RISC-V target OS".

Toolchain version requirement: the only version floor explicitly documented in source is GCC >= 15, required for the xsmtvdotii march extension used by the SpacemiT IME2 path (code comment, ggml/src/ggml-cpu/CMakeLists.txt:500). No other minimum is documented anywhere in the repo. Based on the RVV 1.0 intrinsic names actually used (e.g. __riscv_vsetvl_e32m8), a practical floor of GCC>=14 or Clang/LLVM>=17 can be inferred but is not upstream-documented [NEEDS VERIFICATION - inference, not a stated requirement]. This inference is corroborated by two confirmed build failures on GCC 13.x (below).

QEMU usage: none for riscv64 anywhere in the repository. setup-qemu-action exists only in build-gcc.yml/build-clang.yml, and only emulates linux/ppc64le and linux/arm/v7.

Known build failures:

  • Issue #3717: CMake auto-generates -march=rv64gc_zfh_v_zvfh_zicbop_zihintpause, which GCC 13.3 rejects as an “unexpected ISA string at end”. Reporter speculated GCC 14 would fix it; unconfirmed by any maintainer, unresolved.
  • Issue #2989: __riscv_vcreate_v_i8m1_i8m2 intrinsic (introduced by commit 8ca67df2) is not recognized by GCC 13.2 in ggml_vec_dot_q5_0_q8_0/q5_1_q8_1. A community commenter (not a maintainer) confirmed the same failure in llama.cpp and identified the fix: “GCC 14 and above support the vcreate function, but GCC 13 and below do not.”

Both issues were auto-closed not_planned by the stale bot (2026-09-06 and 2026-09-07 respectively) with no code fix ever merged in whisper.cpp.

Unrelated riscv64 machinery in the tree: ggml/src/ggml-et/et-kernels/ configures a separate bare-metal riscv64 toolchain (-march=rv64imf, -nostdlib) for Esperanto Technologies’ ET-SoC device, requiring an external non-public SDK (ET_PLATFORM_PATH). This is unrelated to general Linux riscv64 CPU support and should not be conflated with it.

6. Feature Coverage and Gap Analysis vs arm64 and amd64

Feature amd64 arm64 riscv64
CPU inference (generic C fallback) yes yes yes
RVV-accelerated quantized dot products n/a (AVX/AVX2/AVX512) n/a (NEON) yes
Vendor matrix-extension acceleration n/a n/a yes, SpacemiT IME (opt-in)
Official prebuilt binary yes yes no
CI test execution yes yes no

Functional gaps: no official upstream riscv64 binary exists at all (source build or a distro package is the only path); a plain cmake -B build fails outright on GCC<14 environments per the two confirmed compiler-compatibility issues above.

Performance gaps: none identified from missing SIMD coverage - the RVV implementation is described in the underlying research as “not a stub,” hand-tuned, and the third-largest architecture-specific backend in the codebase. Data not available: no quantitative riscv64 whisper.cpp inference throughput or real-time-factor (RTF) benchmark could be located from any accessible source. DeepComputing’s “Whisper on RISC-V” page (qualitative claim that Whisper runs locally on their ESWIN EIC7702-based DC-ROMA AI PC) returned HTTP 202 with an empty body on every fetch attempt (bot-gated); OpenBenchmarking.org’s whisper-cpp test page returned HTTP 403; two related YouTube videos exist per search results but are not retrievable via automated tooling.

Security hardening gaps: Data not available - no riscv64-specific hardening/sanitizer research was surfaced (whisper.cpp’s build-sanitize.yml was not confirmed to include riscv64, and by Section 7 no riscv64 CI job of any kind exists).

NaN / floating-point semantics issues: none found. A targeted search for RISC-V-specific NaN/floating-point correctness bugs was performed and returned only the two compiler/build-toolchain issues (#3717, #2989) plus one unrelated PPC64 big-endian byte-order issue (#376); no numerical-correctness issue specific to RVV output exists in the tracker.

7. CI/CD Infrastructure

No riscv64 CI exists, confirmed by directly reading all 22 files in .github/workflows/ (bindings-go.yml, bindings-ruby.yml, build-android.yml, build-clang.yml, build-coreml.yml, build-cpu.yml, build-freebsd.yml, build-gcc.yml, build-macos.yml, build-quantize.yml, build-sanitize.yml, build-self-hosted.yml, build-sycl.yml, build-vad.yml, build-wasm.yml, build-windows.yml, close-issue.yml, deploy-examples-wasm.yml, docker.yml, examples.yml, make-release.yml, release.yml) plus the composite action ccache-clear. A case-insensitive grep for riscv|rvv|rv64|xtheadvector|spacemit across every workflow, every Dockerfile (.devops/*.Dockerfile), and the repository at large returned zero matches. No .gitlab-ci.yml, Jenkinsfile, or .cirrus.yml exists.

Specifics checked directly:

  • docker.yml: matrix has exactly 7 entries, platforms limited to linux/amd64 and linux/arm64, runners ubuntu-24.04/ubuntu-24.04-arm, triggered by workflow_dispatch and a daily schedule cron.
  • build-cpu.yml: 5 jobs, all on ubuntu-22.04 or ubuntu-22.04-arm, triggered by workflow_dispatch, push to master, and pull_request.
  • build-self-hosted.yml: runner labels are [self-hosted, Linux, NVIDIA], [self-hosted, macOS, ARM64], [self-hosted, Windows, X64, stx, rai300-400], [self-hosted, Linux, X64, stx, rai300-400] - no riscv64 self-hosted runner.

RISE runners: not used by whisper.cpp. The sibling project ggml-org/llama.cpp (which shares the ggml codebase whisper.cpp vendors) has its own RISE self-hosted riscv64 CI runner (ubuntu-24.04-riscv label) that is PR-path-triggered on changes inside the riscv arch directory, per RISE’s “RISC-V Runners: six weeks in” post, which names llama.cpp as an adopter. This CI does not run for, or cover, whisper.cpp’s own repository.

  amd64 arm64 riscv64
CI: build yes yes no
CI: test yes yes no
CI: release-gating yes yes N/A

8. Distribution and Release Status

Official upstream GitHub Releases: no riscv64 assets. The five most recent releases checked (v1.9.3, b4938, v1.9.2, v1.9.1, v1.9.0) via the raw GitHub Releases API show asset filenames limited to whisper-bin-ubuntu-{arm64,x64}.tar.gz, whisper-bin-Win32.zip, whisper-bin-x64.zip, whisper-blas-bin-*.zip, whisper-cublas-*.zip, and whisper-*-xcframework.zip - no riscv64 string anywhere.

PyPI: no whisper-cpp package exists (confirmed 404 at both pypi.org/pypi/whisper-cpp/json and pypi.org/simple/whisper-cpp/). The separately-named whispercpp PyPI project ships only manylinux2014_x86_64 and macosx_10_9_x86_64 wheels - no riscv64.

RISE Python wheel builder: no entry; the RISE index redirects to upstream PyPI, which lacks the package.

Debian sid/testing: riscv64 binaries confirmed live via four independent sources - buildd.debian.org (status “Installed”, riscv64, version 1.9.3+dfsg-1, built on buildd rv-manda-04), packages.debian.org/sid/riscv64/libwhisper1, the raw ftp.debian.org pool listing (libwhisper-dev_1.9.3+dfsg-1_riscv64.deb, libwhisper1_1.9.3+dfsg-1_riscv64.deb, whisper.cpp-tools_1.9.3+dfsg-1_riscv64.deb), and the ftp-master madison API, verbatim: libwhisper1 | 1.9.3+dfsg-1 | testing | amd64, arm64, loong64, ppc64el, riscv64, s390x (same line for unstable). The whisper.cpp source package itself is Architecture: all (a metapackage); the compiled riscv64 binaries live in libwhisper1 and whisper.cpp-tools. No riscv64-specific patches were identified in the packaging diff - this is a clean build from unpatched upstream source with GGML_RVV=ON at its CMake default.

Ubuntu 26.04 (Resolute): whisper.cpp (version 1.8.3+dfsg-2, universe/libs) listed with riscv64 among supported architectures (amd64, arm64, ppc64el, riscv64, s390x) per an original packages.ubuntu.com search; a later re-verification attempt returned HTTP 503 from the site and could not re-confirm this live [NEEDS VERIFICATION - re-check was inconclusive due to site unavailability, not a contradiction].

Arch Linux: no official riscv64 package found (archlinux.org search returned zero matches; archriscv.felixc.at/riscv64/extra/ returned 404).

What a user must do to get a working binary: either (a) install Debian sid/testing’s libwhisper1 + whisper.cpp-tools packages (or Ubuntu 26.04’s whisper.cpp package, pending re-verification), or (b) build from source with GCC>=14 (GCC 13.x is confirmed to fail per #3717/#2989), using either the default native CMake configuration (RVV enabled by default) or the provided cmake/riscv64-spacemit-linux-gnu-gcc.cmake cross-toolchain file. No upstream-published prebuilt binary exists via any channel checked.

9. Dependencies

Dependency Role riscv64 build riscv64 test riscv64 release Community/notes
ggml (vendored, upstream ggml-org/ggml) Tensor/SIMD compute core Yes, RVV/zfh/zvfh/zicbop/zihintpause on by default in-tree No dedicated upstream ggml-org/ggml riscv64 CI found in this sweep Found in Ubuntu 26.04 riscv64 (libggml-dev, packaged with llama.cpp) Blocking issues: whisper.cpp #3717, #2989; upstream ggml #1475 (gate cpu-riscv64 backend on Zv* sub-extensions, open), #1535 (ggml-0.14.0 build fails on OpenBSD/riscv64, open)
llama.cpp (vendored under examples/talk-llama; optional system package) LLM inference sharing the ggml core, used by the talk-llama example Yes, RVV kernels + SpacemiT backend, CODEOWNERS entry for ggml/src/ggml-cpu/arch/riscv/ Native (non-QEMU) CI via RISE self-hosted runner ubuntu-24.04-riscv, non-blocking, path-triggered only Found in Ubuntu 26.04 riscv64 (llama.cpp + libggml-dev); also Debian sid None release-blocking as of this report; historical VLEN>256 correctness bug (PR #3453) fixed by #8748
OpenBLAS Optional BLAS backend (GGML_BLAS, off by default off-Apple) Yes, dedicated RVV kernels (C910V, x280 RVV1.0/VLEN512, generic ZVL128B/256B, SiFive U74 4x4 GEMM) QEMU-emulated only, no native riscv64 hardware in upstream CI Found in Ubuntu 26.04 riscv64 (libopenblas-dev, libopenblas0-pthread, 0.3.32+ds-5) Draft PR #5928 (VLEN-agnostic TRSM kernels); closed DGEMM regression #5811 (SpacemiT K1 correctness, 0.3.31 to 0.3.33) shows QEMU-only-CI risk
libcurl Optional model download (WHISPER_CURL, off by default) Yes, riscv64 listed among 28 supported archs in INSTALL.md Tier-2: CI cross-compiles a musl static binary for riscv64, but the test suite never executes on riscv64 Found in Ubuntu 26.04 riscv64 (libcurl4-openssl-dev, libcurl4t64 8.18.0-1ubuntu2.4) None merge-blocking; riscv64 explicitly not release-blocking
FFmpeg Optional audio decode on Linux (WHISPER_COMMON_FFMPEG, off by default) Yes, first-class target, dedicated libavcodec/riscv/ etc. Yes, real test execution: 3 FATE configs at Remlab.net, 5531-5532/5532 tests passing Found in Ubuntu 26.04 riscv64 (ffmpeg 7:8.0.1-3ubuntu2) Open unreviewed patch (since 2025-11-09) adding Zve32x/Zve32f/Zve64x/Zve64d subset detection; not merge-blocking
SDL2 Audio capture for stream/command/talk-llama examples (WHISPER_SDL2, off by default) Portable C, no riscv64-specific code path needed No riscv64-tagged issues/PRs found Found in Ubuntu 26.04 riscv64 (libsdl2-dev 2.32.10+dfsg-6) None identified
OpenMP (libgomp) Default-on (GGML_OPENMP) CPU-backend threading Ships with the riscv64 GCC toolchain N/A (toolchain runtime) Found in Ubuntu 26.04 riscv64 (libgomp1 16-20260322-1ubuntu1) None identified

GPU/JIT accelerator backends (CUDA, HIP, MUSA, Vulkan, Metal, SYCL, OpenCL, WebGPU, OpenVINO, Hexagon, zDNN, ZenDNN) are all OFF by default and have no riscv64 relevance - excluded from the table above.

Net assessment of dependencies: every non-GPU dependency whisper.cpp can pull in already has a riscv64 binary published in Ubuntu 26.04 (resolute). The gaps are in CI rigor (OpenBLAS is QEMU-only with a real regression history; libcurl’s own test suite does not run on riscv64) and in whisper.cpp’s own build glue (#3717’s malformed -march= string), not in upstream dependency availability.

11. Known Bugs and Active Issues

ID Title Status Severity Notes
#3717 Compilation problems on RISC-V Closed, not_planned (stale bot) Blocking - build fails entirely Malformed -march=rv64gc_zfh_v_zvfh_zicbop_zihintpause string rejected by GCC 13.3; unresolved, no fix merged, no maintainer engagement beyond the reporter’s own comment
#2989 The instrinsic function fail of __riscv_vcreate_v_i8m1_i8m2 on RISC-V Closed, not_planned (stale bot) Blocking - build fails in dot-product kernels GCC 13.2 does not support the intrinsic; a community member (not a maintainer) confirmed the same failure in llama.cpp and identified GCC 14+ as the fix; no code fix merged in whisper.cpp

Correctness bugs: none found. A targeted search for RISC-V-specific NaN/floating-point correctness issues returned no results beyond the two compile-failure issues above.

12. Objections and Upstream Blockers

Stated objections: none found specifically against RISC-V support. On the llama.cpp side (where the actual RISC-V engineering happens), Georgi Gerganov - sole reviewer/gatekeeper across the relevant PRs - set three concrete gating requirements before merging the SpacemiT backend (PR #15288): adopt the project’s coding/naming style, provide CI workflows for the new backend, and add a CODEOWNERS entry. All three were satisfied and the PR merged - but only on the llama.cpp side; whisper.cpp itself never added an equivalent riscv64 CI job.

Technical blockers: GCC<14 fails to compile whisper.cpp on riscv64 (two confirmed, unresolved issues); no upstream riscv64 CI exists to catch regressions before they reach users.

Organizational blockers: all substantive RISC-V engineering happens in ggml-org/llama.cpp/ggml, not natively in whisper.cpp. Neither whisper.cpp compile-failure issue received a maintainer reply - #3717 has 2 comments (both from the reporter), #2989 has 3 comments (fix identified by a community member, not a maintainer) - and both were closed by the stale bot for inactivity rather than resolved.

Acceptance probability: whisper.cpp’s CONTRIBUTING.md explicitly favors contributors who “own” the code they add long-term. Given that RISC-V investment already succeeds upstream in ggml/llama.cpp - three merged feature PRs (#15288 SpacemiT backend, #15720 RVV kernel optimization with +183%/+177% throughput gains, #13720 xtheadvector support) and syncs automatically into whisper.cpp - the most likely path to closing the CI/release gap is adding a whisper.cpp-side CI workflow mirroring llama.cpp’s RISE-runner-based approach, rather than new kernel engineering. This is a comparatively low-effort, high-confidence contribution given the precedent already set upstream.

13. Readiness Assessment

  • Color: yellow (clean-distro-build)
  • Release provider: Debian (distro-provided; upstream publishes no riscv64 artifact)
  • Justification: whisper.cpp has zero riscv64 CI - confirmed by directly reading all 22 GitHub Actions workflow files, none of which reference riscv/rvv/rv64 in any form - and ships no riscv64 upstream release artifact (the GitHub Releases API shows no riscv64 asset in the last five releases; no PyPI package exists at all). This alone would place the project at orange under Step 1 of the color model. However, Debian’s own build infrastructure (buildd.debian.org, packages.debian.org, and the ftp-master madison API) confirms a live riscv64 build of libwhisper1/whisper.cpp-tools (version 1.9.3+dfsg-1) compiled directly from unmodified upstream source, with GGML_RVV enabled at its default. Per the distribution floor rule, a clean (unpatched) distro build raises the grade from orange to yellow.
  • Optimization note (not a color-determining factor here, since whisper.cpp is an application rather than a pure optimization library, but material to interpreting the “yellow” grade): the underlying RVV/SpacemiT implementation itself is not the limiting factor - it is described in Section 4 as hand-tuned, third-largest of any architecture-specific backend in the codebase, and “not a stub.” The color is capped at yellow purely by the absence of upstream CI and upstream release artifacts, not by any deficiency in RISC-V code coverage.
  • Pending work that could change the grade: none identified as in-flight specifically for whisper.cpp’s own CI. The precedent exists in the sibling llama.cpp repository, which already runs a RISE self-hosted riscv64 CI runner (ubuntu-24.04-riscv) - extending an equivalent job to whisper.cpp’s own .github/workflows/ would close this gap directly, per the analysis in Section 12. No open PR toward that end was found in this research.

14. Investment Analysis

RISE has not funded or directly touched whisper.cpp (Section on RISE involvement in the research findings: no RISE blog post, no RISE member/project entry, no dedicated repo under riseproject-dev, and the only trace anywhere in the RISE org is an unfulfilled backlog line in this repository’s own .queue.yml). RISE-member SpacemiT is, however, the author of whisper.cpp’s most actively maintained RISC-V code path (the IME backend), and RISE does fund riscv64 CI runner infrastructure that the sibling llama.cpp project already uses.

14.1 Functional Enablement

Already substantially complete upstream via the ggml sync pipeline - the RVV baseline and SpacemiT backend are full, in-tree implementations. The remaining functional gap is narrow: fix (or at minimum document) the CMake -march= string generation and the GCC>=14 requirement that trips #3717/#2989. This is a build-robustness fix, not new kernel engineering, since Debian’s own riscv64 build already succeeds against unpatched upstream source.

14.2 Performance Optimization

Already substantially complete upstream - the RVV kernel optimization work (llama.cpp PR #15720) delivered +183% prompt-processing and +177% token-generation throughput on a representative model in the shared ggml codebase, and the SpacemiT IME backend adds further vendor-specific matrix-extension acceleration. No whisper.cpp-specific performance investment is indicated beyond what ggml already provides via sync. Data not available: no whisper.cpp-specific (as opposed to generic ggml/llama.cpp) riscv64 throughput or RTF numbers could be located in this research.

14.3 CI/CD Infrastructure

Not yet done for whisper.cpp itself, despite being done for llama.cpp. The concrete work item is adding a riscv64 job to whisper.cpp’s own .github/workflows/ (extending build-cpu.yml or adding a new build-riscv.yml), reusing RISE’s existing runner infrastructure and the GCC>=14 toolchain already proven to work by Debian’s package build. This is the single highest-leverage item identified in this report: it would catch regressions like #3717/#2989 before they reach users, and is a small, well-precedented piece of engineering given llama.cpp’s existing workflow to copy from.

14.4 Ecosystem Enablement

whisper.cpp has no significant dependent package ecosystem of its own (Section 10 omitted per report criteria). The relevant “ecosystem” work is at the distribution level: re-verify Ubuntu 26.04’s riscv64 whisper.cpp package (last confirmed at the older 1.8.3+dfsg-2, versus Debian’s more current 1.9.3+dfsg-1) and, if desired, publish an official upstream GitHub Release riscv64 binary (e.g. whisper-bin-ubuntu-riscv64.tar.gz) analogous to the existing arm64/x64 assets.

14.5 Summary Table

Area Work Item Effort (person-weeks) Owner Priority
Functional Fix CMake -march= string generation for GCC 13.x compatibility, or document GCC>=14 as the minimum and gate the build accordingly 1-2 whisper.cpp maintainer/contributor High
CI/CD Add a riscv64 CI job to whisper.cpp’s own workflows, reusing RISE’s ubuntu-24.04-riscv runner (precedent: llama.cpp’s build-riscv.yml) 2-3 whisper.cpp maintainer + RISE runner infra High
Distribution Publish an official upstream GitHub Release riscv64 binary asset, once CI exists to validate it 1 whisper.cpp maintainer Medium
Distribution Re-verify and, if lapsed, refresh Ubuntu 26.04’s whisper.cpp riscv64 package to track current upstream (1.9.3+dfsg-1 per Debian) 0.5 Ubuntu/Debian packaging Low
Performance No whisper.cpp-specific work indicated; monitor upstream ggml/llama.cpp RVV/SpacemiT kernel progress for sync-in gains N/A (tracked upstream) ggml-org/llama.cpp Low

15. Updates

(No updates yet - initial report dated 2026-09-07.)

16. References