Introduce Virtual Register abstraction to improve register allocation #269
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| int calculate_spill_cost(var_t *var, basic_block_t *bb, int current_idx) |
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Although the commit message has explained "cost", how about also adding some comments here?
This commit introduces a Virtual Register (VReg) abstraction layer to improve register allocation efficiency: - Add phys_reg field to var_t for direct physical register mapping - Optimize prepare_operand() and prepare_dest() with O(1) lookups - Eliminate redundant linear register searches
Building on the VReg abstraction, this commit adds intelligent spill decisions based on variable usage patterns and context. - Track variable lifetime with first_use, last_use, and use_count - Add loop_depth field for identifying loop-resident variables - Transform spill cost from simple distance to multi-factor heuristic: * Loop variables: +200 cost per nesting level * Usage frequency: +5 cost per use * Live range length: +20 for long ranges * Constants: -50 (prefer spilling for rematerialization)
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Virtual Register (VReg) abstraction layer is added to improve register allocation efficiency.