Commits on Feb 5, 2024

1. target: default to the medium code model on LoongArch targets …

   The Rust LoongArch targets have been using the default LLVM code model
   so far, which is "small" in LLVM-speak and "normal" in LoongArch-speak.
   As described in the "Code Model" section of LoongArch ELF psABI spec
   v20231219 [1], one can only make function calls as far as ±128MiB with
   the "normal" code model; this is insufficient for very large software
   containing Rust components that needs to be linked into the big text
   section, such as Chromium.
   
   Because:
   
   * we do not want to ask users to recompile std if they are to build
     such software,
   * objects compiled with larger code models can be linked with those
     with smaller code models without problems, and
   * the "medium" code model is comparable to the "small"/"normal" one
     performance-wise (same data access pattern; each function call
     becomes 2-insn long and indirect, but this may be relaxed back into
     the direct 1-insn form in a future LLVM version), but is able to
     perform function calls within ±128GiB,
   
   it is better to just switch the targets to the "medium" code model,
   which is also "medium" in LLVM-speak.
   
   [1]: https://github.com/loongson/la-abi-specs/blob/v2.30/laelf.adoc#code-models

   

   xen0n committed Feb 5, 2024
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