WIP: Optimization pass - #380
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can't merge this. optimization is not that simple, on top of that this works on arm only.
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The code have some arm64-specific logic (but works on others archs), also it have too many regexps postprocessing the text. I tried to make it fit into a separate file to not mess with the rest. But I agree that the code quality is far from ideal. I’ll do some iterations to add optimization steps in a clean and generic way. So yeah better not to merge it like this, hopefully it will serve as a base of inspiration for what r2dec output can be |
Removed (ARM64-specific code) 1. simplifyStackCanaryChecks() - Entirely ARM64-specific; hardcoded w8, x8, x9, x29-8 register patterns and reloc.__stack_chk_fail patterns 2. simplifyStackCanaryScopes() - Same ARM64-specific issues; was also matching regular non-canary comparisons as false positives 3. buildGuardValueExprFromWindow() - Helper hardcoded for ARM64 x8 register chains 4. matchStackSaveSlot() - Hardcoded x29 - 8 ARM64 stack save pattern 5. isStackChkFailStatement() - Only used by removed stack canary passes 6. findInstructionIndexAtOrAfterAddress() - Only used by removed stack canary scope pass 7. hasSubsequentReturn() - Unused function Fixed (portability) 8. getBasePointerRegisters() - Removed hardcoded x29, rbp, ebp fallback; empty list if r2 query fails (conservative) 9. isReturnRegisterName() - Replaced hardcoded [w0, x0, r0, eax, rax, v0] list with r2 query arp~R0[1] (works across all architectures) 10. isRegisterIdentifier() - Replaced hardcoded [xw]\d+, r\d+, (e|r)?ax patterns with r2 query arp~gpr[1] 11. All Set uses - Replaced with Object.create(null) for QuickJS compatibility Fixed (correctness bugs) 12. parseWriteStatement() - Fixed regex = to =(?!=) to prevent x == y being parsed as assignment x = "= y" 13. simplifyTrivialConstants() - Removed unsafe (0)→0 and (1)→1 paren removal that broke function call parens (e.g., isatty (1) → isatty 1) 14. propagateConstants() - Added readOnly mode after first branch to prevent facts from inside conditional blocks leaking past merge points 15. inlineSingleUseAssignments() - Added eventPastBranch pre-computation to prevent inlining definitions from inside conditional blocks to code outside 16. removeDeadAssignments() - Added pastBranch tracking to prevent removing assignments where the killing write is behind a conditional branch Test results - ARM64 (/bin/ls main): 782 → 749 lines (4% reduction) - x86-64 (bash main): 1469 → 1303 lines (11% reduction) - MIPS (boa-mips main): 417 → 332 lines (20% reduction) - ARM32 (arm-init main): works correctly - optimize=0 produces identical output to no optimization (no regression)
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i have vibecoded with gpt-5.2 an optional optimization pass at the end of the decompilation pipeline. this can be configured with 'r2dec.optimize=6' . as you can see the current output is pretty close to r2ghidra, the main problem here is that r2 var analysis is not correct and its still inlining some stack arithmetics that can be optimized properly with manual var definitions. Hopefully addressed after the next release in the r2 side.