The passes
Each pass is a rewrite over the instruction stream that leaves every address where it was.
The passes
| Pass | What it rewrites |
|---|---|
| Branch and call threading | A jump or call to a thunk goes straight to the thunk's target. |
| Identity bypass | Runs of instructions that leave every register as it was are stepped over. |
| Stack load forwarding | A value just stored to the stack is used directly instead of loaded back. |
| Constant branches | A branch whose outcome is fixed becomes a jump or falls through. |
| Strength reduction | An arithmetic instruction becomes a cheaper one with the same result. |
| Unreachable code | Blocks and functions no root can reach are neutralized. |
Roots
The entrypoint, every direct call target and every relocation target are roots. Indirect calls keep every target they could reach.
Counters
optimization.json holds one counter per pass, the program counters that were modified, the count of relocation sites preserved, and the SHA-256 of the program before and after.