Finish RISC-V TODO backlog: switch lowering, result returns, optimizer tweaks#41
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mengzhuo merged 2 commits intoplctlab:mainfrom Nov 7, 2025
DzmingLi:main
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Finish RISC-V TODO backlog: switch lowering, result returns, optimizer tweaks#41mengzhuo merged 2 commits intoplctlab:mainfrom DzmingLi:main
mengzhuo merged 2 commits intoplctlab:mainfrom
DzmingLi:main
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This commit resolves 5 TODO items in the MoonBit compiler, improving code quality, optimization capabilities, and error handling. All changes are original contributions not present in bmwangmh/workspace branch. ## 1. Pure Function Call Elimination (src/riscv_opt_peephole.ml:171) - Implement dead code elimination for pure functions with unused results - Improve is_pure function to support local alloca storage - Add comprehensive test suite (test/src/pure_elim/) - Optimization allows removal of side-effect-free calls, reducing code size ## 2. Refactor inst_convert Function (src/riscv_virtasm.ml:289) - Reduce code duplication using typed helper functions - Add explicit type annotations to prevent OCaml type inference issues - Improve code structure with 10 conversion helpers for different instruction types - Reduce repetitive pattern matching from 88 lines to organized, maintainable code ## 3. Extend Switch Statement Type Support (src/riscv_generate.ml:1311) - Add support for C_byte, C_int64, C_uint, C_uint64 in switch statements - Add clear TODO markers for unsupported types (float, double, bigint, string, bytes) - Include test suite with future test cases documented (test/src/switch_types/) - Prepare compiler for extended type support when MoonBit language adds these features ## 4. Optimize JumpIndirect (src/riscv_virtasm_generate.ml:377) - Add validation for empty possibility list (fail fast with clear error) - Preserve single-target optimization (convert to direct jump) - Restructure to match expression for better clarity - Document future optimization direction (conditional branches for 2-3 targets) ## 5. Handle default_expr Conflicts (src/ast_derive.ml:1996) - Properly handle case where both positional and named layouts specify defaults - Check for equality: accept if same, error with clear message if different - Improve error reporting with parameter name/index in conflict messages - Replace generic "TODO" failwith with semantic validation ## Test Coverage - test/src/pure_elim/: Validates pure function elimination optimization - test/src/switch_types/: Tests existing switch types, documents future additions - All existing tests continue to pass
This commit implements 6 TODO items and adds comprehensive test coverage: 1. Error_result return handling (riscv_generate.ml:1171) - Wrap return values in Result<T, E> constructor - Handle both Ok (tag=1) and Err (tag=0) cases - Properly allocate and store tagged values 2. String constant switch support (riscv_generate.ml:1336) - Generate if-else chain with proper UTF-16 string comparison - Use memcmp for byte-by-byte comparison of UTF-16 LE encoded strings - First compare lengths, then compare content 3. Bytes constant switch support (riscv_generate.ml:1424) - Similar to string switch but for byte arrays - Each byte is 1 byte (not UTF-16 like strings) - Use memcmp for content comparison 4. Register allocation optimization (riscv_reg_alloc.ml:123) - Implement least-used register selection strategy - Replace arbitrary choice with usage-based heuristic - Reduce register pressure through better allocation 5. JumpIndirect optimization for 2 targets (riscv_virtasm_generate.ml:388) - Convert 2-target indirect jumps to conditional branches - Load target address and compare with jump register - Avoid indirect jump pipeline flush 6. Interpreter memcmp support (test/interpreter.cpp:365) - Add memcmp function to SSA interpreter - Required for string/bytes comparison to work in tests Tests added: - test/src/error_result: Tests Result<T,E> wrapping for error returns - test/src/string_switch: Tests string pattern matching - test/src/bytes_switch: Tests bytes pattern matching
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lowering backed by interpreter
memcmp, and improve register allocation plus JumpIndirect2-target lowering
inst_convert,extend integer switch support, and guard against conflicting default expressions
elimination, and wider switch type coverage