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@@ -1,5 +1,32 @@ ## yaxpeax-arm +`yaxpeax-arm` provides implementations of decoders for the armv7, v7/thumb, v7/thumb2, and aarch64/a64 instruction sets. + +the entrypoint to begin decoding is either `armv7::InstDecoder` (`ARMv7::Decoder::default()`) or `armv8::InstDecoder` (`ARMv8::Decoder::default()`). `default` for both decoders is to decode in ARM mode. `default` will try to decode as permissively as possible, even attempting to produce some kind of instruction for `UNPREDICTABLE` patterns, where possible. for armv7 and below, `default_thumb` produces a similarly permissive set of rules, but for decoding thumb/thumb2 instructions. + +ARMv7 and thumb mode instructions decode to the same structure: `armv7::Instruction`. this is not known to introduce ambiguities, and if you must discern thumb vs non-thumb origins, `armv7::Instruction::thumb` will reflect the decoder state when decoding the instruction of interest. additionally, `armv7::Instruction::w` reports if the instruction was a wide (32-bit) thum instruction. + +for all ARMv7 instructions, `armv7::Instruction::s()` reports if the instruction will update status flags. if `s` is in error, that is a decoder bug, please report it. + + +## stability +0.1 and 1.0 versions are considered significant indicators of feature-completeness and stability. the specific guidelines by which `yaxpeax-arm` will be considered stable are listed below. + +### 0.1 checklist +[ ] support `NEON` +[ ] adjust `yaxpeax-arch` so `min_length` can be contingent on the mode of `InstDecoder` + - currently `min_length` is always 4, which is incorrect for `Thumb` modes. + conversely, selecting "2" would be flagrantly wrong for `ARM` modes. +[ ] address all in-tree TODO + +### 1.0 checklist +[ ] support per-version decode flags, so decoding an armv4, armv5, or armv7 instruction +[ ] fully support `should_is_must` to control how pedantic decoding should be +[ ] fully support reporting `unpredictable` encodings as `DecodeError::Unpredictable` if required +[ ] exhaustively test armv7 and armv8 instructions against other decoders + - existing thumb test suite is derived from enumerating thumb instructions, + but is missing some + ### ! user beware ! * armv7 NEON support is still nonexistent |