47b41b7788
LLVM codegen: Don't emit zero-sized padding for fields Currently padding is emitted before fields of a struct and at the end of the struct regardless of the ABI. Even if no padding is required zero-sized padding fields are emitted. This is not useful and - more importantly - it make it impossible to generate the exact vector types that LLVM expects for certain ARM SIMD intrinsics. This change should unblock the implementation of many ARM intrinsics using the `unadjusted` ABI, see https://github.com/rust-lang/stdarch/issues/1143#issuecomment-827404092. This is a proof of concept only because the field lookup now takes O(number of fields) time compared to O(1) before since it recalculates the mapping at every lookup. I would like to find out how big the performance impact actually is before implementing caching or restricting this behavior to the `unadjusted` ABI. cc `@SparrowLii` `@bjorn3` ([Discussion on internals](https://internals.rust-lang.org/t/feature-request-add-a-way-in-rustc-for-generating-struct-type-llvm-ir-without-paddings/15007)) |
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| Cargo.toml | ||
| README.md | ||
The codegen crate contains the code to convert from MIR into LLVM IR,
and then from LLVM IR into machine code. In general it contains code
that runs towards the end of the compilation process.
For more information about how codegen works, see the rustc dev guide.