Allow inline relocations in dehydrated data #78545
Conversation
This is a follow up to dotnet#77884. In the original pull request, all relocation targets went into a lookup table. This is not a very efficient to represent rarely used relocs. In this update, I'm extending the dehydration format to allow representing relocations inline - instead of indirecting through the lookup table, the target immediately follows the instruction. I'm changing the emitter to emit this if there's less than 2 references to the reloc. This produces a ~0.5% size saving. It likely also speeds up the decoding at runtime since there's less cache thrashing. On a hello world, the lookup table originally had about 11k entries. With this change, the lookup table only has 1700 entries.
ghost
assigned 
|
Tagging subscribers to this area: @agocke, @MichalStrehovsky, @jkotas Issue DetailsThis is a follow up to #77884. In the original pull request, all relocation targets went into a lookup table. This is not very efficient to represent rarely used relocs. In this update, I'm extending the dehydration format to allow representing relocations inline - instead of indirecting through the lookup table, the target immediately follows the instruction. I'm changing the emitter to emit this if there's less than 3 references to the reloc. This produces a ~0.5% size saving. It likely also speeds up the decoding at runtime since there's less cache thrashing. On a hello world, the lookup table originally had about 11k entries. With this change, the lookup table only has 1700 entries. Cc @dotnet/ilc-contrib
|
If multiple relocations follow after each other, generate a single command with the payload specifying the number of subsequent relocations. This saves additional 0.1%.
|
A pushed out one more commit to generate runs of inline relocations. This allows us to skip emitting the command byte if multiple inline relocations follow each other. Saves additional 0.1%. The total diff is still pretty small but I'd recommend reviewing commit by commit so that there's less to review. |
This is a follow up to #77884. In the original pull request, all relocation targets went into a lookup table. This is not very efficient to represent rarely used relocs. In this update, I'm extending the dehydration format to allow representing relocations inline - instead of indirecting through the lookup table, the target immediately follows the instruction. I'm changing the emitter to emit this if there's less than 3 references to the reloc.
This produces a ~0.5% size saving. It likely also speeds up the decoding at runtime since there's less cache thrashing. On a hello world, the lookup table originally had about 11k entries. With this change, the lookup table only has 1700 entries.
Cc @dotnet/ilc-contrib