Move globals out of the MVP #344
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lgtm. |
| linear memory. This would allow more aggressive compiler optimizations (due to | ||
| better alias information). If globals are additionally allowed array types, | ||
| significant portions of memory could be moved out of linear memory which could | ||
| reduce fragmentation issues. Langauges like FORTRAN which limit aliasing would be |
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Nowadays it's Fortran. No more yelling.
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lgtm, but it would be good to leave this open until early next week, so @titzer and others who are supposed to be on vacation can take a look :-) |
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If we do this we should consider adding a way to explicitly set a symbol's numeric value. That will let us assign the heap locations of global state names in our test cases (and make it possible to round-trip them in a decompile/compile loop). |
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At first I was confused by your use of "symbol" (interpreting "symbol" in the context of the hunk added to DynamicLinking.md by this PR) since immutable global pointers are post-MVP. But I think you're talking about "debugging symbols", as in the separate, optional module section which is purely added to assist projection of binary to text. In that case, I totally agree; I just added a section to TextFormat.md describing this interaction. |
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We (@ncbray, @flagxor, @lukewagner, @kripken, @sunfishcode) had a chat about this offline, and agree that this patch can indeed land as-is. We had concerns that for MVP we may want a more restricted form of globals to address specific performance concerns, and Mozilla folks expressed their willingness to revisit new-MVP-globals if/when data shows that we need to revisit. |
Based on a lot of discussion in #154, I'm proposing we remove globals from the MVP. This PR also discusses the different things we want post-MVP: immutable global pointers for dynamic linking, mutable thread-local variables for threads, and a new future feature for real mutable global variables that captures the use cases.