Fix many illegal instruction decode cases #33
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The decode had a TODO to handle illegal instructions more precisely. Some instructions in the new CHERI spec were not causing traps, and seemed to wedge the core. Switch to a new style where instructions are assumed illegal unless explicitly declared legal. This definitely at least covers many funct3 etc fields where only some of the encodings are currently used.
gameboo
reviewed
Jan 14, 2025
gameboo
reviewed
Jan 14, 2025
gameboo
reviewed
Jan 14, 2025
gameboo
reviewed
Jan 14, 2025
gameboo
approved these changes
Jan 14, 2025
As well as clarifying the logic in the main decode function (no functionality change), this also fixes some cases that should be illegal but weren't caught in the memory instructions.
gameboo
approved these changes
Jan 15, 2025
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The decode had a TODO to handle illegal instructions more precisely. Some instructions in the new CHERI spec were not causing traps, and seemed to wedge the core.
Switch to a new style where instructions are assumed illegal unless explicitly declared legal.
This definitely at least covers many funct3 etc fields where only some of the encodings are currently used.