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wasm: recompute mir_uavs after Mir.Optimize to prune dead constants - #140
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November 4, 2026 15:16
Rebuild cg.mir_uavs from surviving .uav_ref and .uav_ref_off instructions after Mir.Optimize.optimize runs in CodeGen.generateInner, preserving each surviving UAV's computed alignment so dead UAVs do not get lowered or allocated in the Wasm data section. Extend Mir.Optimize to recognize pointer/reference constants (.uav_ref, .uav_ref_off, .nav_ref, .nav_ref_off, .func_ref, .tls_nav_ref, .error_name_table_ref, .enum_tag_name_table_ref) and .errors_len across drop, constant select, and dead local_set elimination, and sink numeric constants across empty block headers and local_tee branch conditions so folded runtime conditions prune dead branches end-to-end. Closes #110 Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
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Summary
cg.mir_uavsinsrc/codegen/wasm/CodeGen.zig(generateInner) afterMir.Optimize.optimizeby scanning surviving.uav_ref(data.ip_index) and.uav_ref_off(@fromBackingInt(cg.mir_extra.items[data.payload])) instructions while preserving each surviving UAV's computedAlignment.src/codegen/wasm/Optimize.zigto recognize pointer/reference constants (.uav_ref,.uav_ref_off,.nav_ref,.nav_ref_off,.func_ref,.tls_nav_ref,.error_name_table_ref,.enum_tag_name_table_ref) and.errors_lenacross.drop, constant.select, and dead.local_setelimination, and sink numeric constants across empty.blockheaders andlocal_teebranch conditions so folded runtime conditions prune dead branches end-to-end.src/codegen/wasm/Optimize.zigand a Wasm behavior test intest/behavior/wasm.zig.Closes #110