[JakeStevens]

Summary

The Cadence HiFi and Fusion G3 operators are forks of the portable kernels and carry the int64 precision bug from #24169, which #24170 fixes in portable.

HiFi and G3 div_out_mode (and G3 div_scalar_mode_out) called std::trunc on the integer quotient, rounding int64 values above 2^53 through double. Integer division already truncates, so trunc now only runs for floating-point types.

HiFi fmod.Tensor_out and fmod.Scalar_out forced every integer compute type to Double. Integers are now computed with %, returning 0 for a divisor of -1 like ATen. fmod.Scalar_out checks for a zero divisor after casting the scalar to the compute dtype, so 256 for an int8 tensor fails instead of reaching a % 0; empty inputs skip the check like ATen. The local fmod_value helper can switch to utils::fmod_override once #24170 lands.

HiFi fmod.Tensor_out also had an inverted NNLib fast-path condition: Float inputs always took the std::fmod fallback, and every other dtype with rank > 0 was sent to xa_nn_elm_fmod_f32xf32_f32, which read integer data as float. The fast path is removed rather than fixed: the NNLib kernel computes a - trunc(a / b) * b in float32, which is not exact fmod (1.0f and 0.1f give 0 instead of ~0.1), so enabling it would change today's Float results. Float behavior is unchanged by this PR.

Test plan

I could not build or run the Xtensa targets locally. All three changed files pass a host clang++ -std=c++17 -fsyntax-only -Wall check against stub NNLib headers, which instantiates every dtype in the switches. The integer fmod and divisor logic matches the portable kernels tested in #24170 and the portable remainder fix. There is no existing HiFi fmod test target to extend; relying on Cadence CI for the build.

This PR was authored with AI assistance (Claude Code), with an additional review pass by Codex.

[pytorch-bot]

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❌ 1 New Failure

As of commit 1ea7b32 with merge base cb3f24e ():

NEW FAILURE - The following job has failed:

• pull / nxp-mcuxpresso-test / linux-job (gh)
  RuntimeError: Command bash /__w/_temp/exec_script failed with exit code 1

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[rascani]

Probably worth importing internally for verification.

[meta-codesync]

@mcremon-meta has imported this pull request. If you are a Meta employee, you can view this in D129098757.