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fix: allow build on arm64 #4502

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fix: allow build on arm64 #4502

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876dbe7
Update config.toml
hypdeb Nov 20, 2025
cfa88cf
Merge branch 'ai-dynamo:main' into main
hypdeb Nov 22, 2025
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3 changes: 3 additions & 0 deletions .cargo/config.toml
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Original file line number Diff line number Diff line change
Expand Up @@ -4,3 +4,6 @@
[build]
# tokio-console needs this
rustflags = ["--cfg", "tokio_unstable"]

[target.aarch64-unknown-linux-gnu]
rustflags = ["-C", "target-feature=+fp16"]
Comment on lines +8 to +9
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@coderabbitai coderabbitai bot Nov 20, 2025

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⚠️ Potential issue | 🔴 Critical

🧩 Analysis chain

Verify the correct rustflag for FP16 support on ARM64.

The PR description mentions the error requires "fullfp16", but the config uses target-feature=+fp16. Confirm that this flag is correct and sufficient to resolve the compilation error in gemm-common.

Additionally, consider whether other ARM64 target triples (e.g., aarch64-apple-darwin, aarch64-pc-windows-msvc) require the same configuration, or if this is specific to aarch64-unknown-linux-gnu.

🌐 Web query:

What is the correct Rust/Cargo rustflag to enable fullfp16 or fp16 CPU feature on aarch64?

💡 Result:

Use rustc's target-feature flag with the AArch64 feature name "fullfp16". Example:

  • Environment / Cargo: RUSTFLAGS="-C target-feature=+fullfp16"
  • .cargo/config.toml: [target.] rustflags = ["-C", "target-feature=+fullfp16"]

References: LLVM/Clang show the AArch64 feature name is fullfp16, and rustc accepts target-feature via -C. [1][2]

Sources:
[1] Clang/LLVM aarch64 tests showing "+fullfp16" feature name.
[2] rustc docs: use -C target-feature to enable/disable CPU features.

Correct the rustflag: use +fullfp16 instead of +fp16.

The correct Rust/Cargo rustflag to enable fullfp16 support on aarch64 is target-feature=+fullfp16. The PR currently uses target-feature=+fp16, which is incorrect and will not resolve the gemm-common compilation error.

Lines 8-9 should be:

[target.aarch64-unknown-linux-gnu]
    rustflags = ["-C", "target-feature=+fullfp16"]
🤖 Prompt for AI Agents 
In .cargo/config.toml around lines 8 to 9, the rustflags entry incorrectly uses
"target-feature=+fp16"; replace it with the correct feature
"target-feature=+fullfp16" so the aarch64 build enables fullfp16 support (i.e.,
update the rustflags array value to use +fullfp16).

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