Use liveness info to speed up allocation #965
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vbgl
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Nov 28, 2024
compiler/src/liveness.ml
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| let s_o' = if weak then Sv.add (L.unloc x) s_o else s_o in | ||
| let s_i, c = live_c weak c s_o' in |
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This looks wrong. s_o' should be s_o and x should be removed from s_i.
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Indeed, this was certainly wrong. Is this better?
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libjade fails, so I guess it's wrong.
vbgl
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Nov 28, 2024
I added an item. |
vbgl
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Nov 28, 2024
compiler/src/liveness.ml
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| if Sv.subset s_i s_o then s_i, c | ||
| else loop (Sv.union s_i s_o) in | ||
| let s_i, c = loop s_o in | ||
| s_i, (if weak then Sv.add (L.unloc x) s_o else s_o), Cfor (x, r, c) |
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Why do you look at weak?
The variables occurring in the range are live before the for instruction.
The tables used in allocation can be huge. We remove the dead variables from the tables, to reduce their sizes and speed up the pass.
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vbgl
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The tables used in allocation can be huge. We remove the dead variables from the tables, to reduce their sizes and speed up the pass. Inspired by CompCert that does something similar to reduce the cost of the value analysis.
Please review carefully the changes to Liveness, because I don't know what I did.
On this implementation of Keccak, the time taken by the analysis after inlining goes down from 20s to 1.5s. It still feels too much for 4 inlined functions (size 1700, 3800 variables). (More functions are inlined, but these are the ones where the time is spent).