exir: serialize non-finite floats in a form flatc accepts - #22152
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Python's json module emits `Infinity`, `-Infinity`, and `NaN` for non-finite floats. Those literals are a Python extension rather than JSON, and flatc's parser rejects them, so any delegate graph holding a non-finite constant failed to serialize with an opaque `flatc returned non-zero exit status 1`. This blocked Vulkan/WebGPU export for every causal-decoder LLM: the attention mask is built with a -inf fill, the partitioner claims the `aten.full` that carries it, and the value reaches the graph as a Double. It is independent of quantization mode, since the mask stays fp32 regardless of weight width. flatc does accept the quoted forms "inf", "-inf", and "nan" for float fields, so the value was representable all along. Rewrite non-finite values into those before invoking flatc. `_replace_infinity_in_json_file` already does this on the decompile side for program.fbs; the compile side had no equivalent, and needs a different token because it sees Python's spelling rather than flatc's. Fixing this in the shared `_flatc_compile` rather than in Vulkan's serializer covers the six backends that build flatbuffers by piping json.dumps output through flatc. Only Vulkan is confirmed to hit it today; the rest partition different op sets, so treat them as latent. Content with no non-finite values is returned unchanged and its file is left untouched, so the common path is unaffected. The rewrite parses the JSON instead of pattern-matching its text, which avoids corrupting string fields that happen to contain "Infinity". Authored with assistance from Claude Code.
🔗 Helpful Links🧪 See artifacts and rendered test results at hud.pytorch.org/pr/pytorch/executorch/22152
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Python's json module emits
Infinity,-Infinity, andNaNfor non-finite floats. Those literals are a Python extension rather than JSON, and flatc's parser rejects them, so any delegate graph holding a non-finite constant failed to serialize with an opaqueflatc returned non-zero exit status 1.This blocked Vulkan/WebGPU export for every causal-decoder LLM: the attention mask is built with a -inf fill, the partitioner claims the
aten.fullthat carries it, and the value reaches the graph as a Double. It is independent of quantization mode, since the mask stays fp32 regardless of weight width.flatc does accept the quoted forms "inf", "-inf", and "nan" for float fields, so the value was representable all along. Rewrite non-finite values into those before invoking flatc.
_replace_infinity_in_json_filealready does this on the decompile side for program.fbs; the compile side had no equivalent, and needs a different token because it sees Python's spelling rather than flatc's.Fixing this in the shared
_flatc_compilerather than in Vulkan's serializer covers the six backends that build flatbuffers by piping json.dumps output through flatc. Only Vulkan is confirmed to hit it today; the rest partition different op sets, so treat them as latent. Content with no non-finite values is returned unchanged and its file is left untouched, so the common path is unaffected. The rewrite parses the JSON instead of pattern-matching its text, which avoids corrupting string fields that happen to contain "Infinity".Authored with assistance from Claude Code.