🍒 [WebAssembly] Emit clangast in custom section aligned by 4 bytes #3451
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Emit __clangast in custom section instead of named data segment to find it while iterating sections. This could be avoided if all data segements (the wasm sense) were represented as their own sections (in the llvm sense). This can be resolved by WebAssembly/tool-conventions#138 And the on-disk hashtable in clangast needs to be aligned by 4 bytes, so add paddings in name length field in custom section header. The length of clangast section name can be represented in 1 byte by leb128, and possible maximum pads are 3 bytes, so the section name length won't be invalid in theory. Fixes https://bugs.llvm.org/show_bug.cgi?id=35928 Differential Revision: https://reviews.llvm.org/D74531
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@swift-ci Please test |
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@shahmishal would you be available for review and merge? Thanks! |
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cc: @hyp |
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Do we need to wait for @hyp 's approval? Or is it ok to merge this for now and revert if it breaks something? After this patch, swiftwasm can use |
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Isn't part of this path upstreamed? I don't think that this should be going here if it is. I think that waiting for @hyp is probably a good idea here. |
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@compnerd This patch has been already landed in the upstream LLVM https://reviews.llvm.org/rG1813fde9cc0b56cee42d9b82e6f22fa00a59cdf9 OK, let's wait @hyp 👍 |
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Ah, I failed to read the truncated link as a cherry-pick. Thanks! This is a clean cherry-pick from upstream. The changes are isolated. I think that this change is fine to merge, but I'd still prefer to have a cross-repository test first. Have you run that yet? |
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OK, cross-repos test has been passed now |
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LGTM, I think that this should be safe to merge. |
As previously announced by @kateinoigakukun: >The last required commit for swiftwasm has been cherry-picked to the swift's llvm branch! swiftlang/llvm-project#3451 >We no longer need to maintain our llvm downstream fork
Emit __clangast in custom section instead of named data segment
to find it while iterating sections.
This could be avoided if all data segements (the wasm sense) were
represented as their own sections (in the llvm sense).
This can be resolved by WebAssembly/tool-conventions#138
And the on-disk hashtable in clangast needs to be aligned by 4 bytes,
so add paddings in name length field in custom section header.
The length of clangast section name can be represented in 1 byte
by leb128, and possible maximum pads are 3 bytes, so the section
name length won't be invalid in theory.
Fixes https://bugs.llvm.org/show_bug.cgi?id=35928
Differential Revision: https://reviews.llvm.org/D74531
Cherry-pick from llvm@1813fde to build Swift stdlib for WebAssembly importing SwiftShims module.
CC: @MaxDesiatov, @compnerd