feat[venom]: mark loads as non-volatile #4388
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this commit marks load instructions (`mload`, `sload`, etc) as non-volatile, allowing them to be removed in the `remove_unused_variables` pass.
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Additional details and impacted files@@ Coverage Diff @@
## master #4388 +/- ##
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- Coverage 91.76% 48.99% -42.78%
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Files 119 120 +1
Lines 16615 16662 +47
Branches 2796 2801 +5
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- Hits 15247 8163 -7084
- Misses 936 7848 +6912
- Partials 432 651 +219 ☔ View full report in Codecov by Sentry. |
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@HodanPlodky pointed out offline -- there could be an |
| for idx, inst in enumerate(bb.instructions): | ||
| self.instruction_index[inst] = idx | ||
| if inst.opcode == "msize" and bb not in self.reads_msize: | ||
| self.reads_msize[bb] = idx |
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Should not this store last msize in basic block instead of first msize. This could be the problem in case which is showed in PR charles-cooper#53
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Co-authored-by: HodanPlodky <[email protected]>
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Volatile instructions were something temporary until proper effects handling was implemented. Now that the dft pass is doing proper effects analysis and makes use of that information, this elimination should be part of it? |
I think we can generalize the analysis done here but it increases the PR scope |
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i investigated refactoring (or at least trimming down) VOLATILE_INSTRUCTIONS and replacing it with essentially checking if the instruction is a terminator instruction or has write effects. however, it was not that clean since we still need to special-case MSIZE. another approach which simplifies the code here would be to have a special volatile instruction like |
simplify some code. remove a dead comment
this commit marks load instructions (
mload,sload, etc) as non-volatile, allowing them to be removed in theremove_unused_variablespass.What I did
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