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74ef47e90c
rust/compiler/rustc_codegen_llvm
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Erik Desjardins 74ef47e90c make CastTarget::size and CastTarget::llvm_type consistent, remove 
special case that's not present in Clang

Making the methods consistent doesn't require much justification. It's
required for us to generate correct code.

The special case was present near the end of `CastTarget::llvm_type`, and
resulted in the final integer component of the ABI type being shrunk to
the smallest integer that fits.

You can see this in action here (https://godbolt.org/z/Pe73cr91d),
where, for a struct with 5 u16 elements, rustc generates
`{ i64, i16 }`, while Clang generates `[2 x i64]`.

This special case was added a long time ago, when the function was
originally written [1]. That commit consolidated logic from many
backends, and in some of the code it deleted, sparc64 [2] and
powerpc64 [3] had similar special cases.

However, looking at Clang today, it doesn't have this special case for
sparc64 (https://godbolt.org/z/YaafvYWdf) or powerpc64
(https://godbolt.org/z/5c3YePTje), so this change just removes it.

[1]: f0636b61c7 (diff-183c4dadf10704bd1f521b71f71d89bf755c9603a93f894d66c03bb1effc6021R231)
[2]: f0636b61c7 (diff-2d8f87ea6db6d7f0a6fbeb1d5549adc07e93331278d951a1e051a40f92914436L163-L166)
[3]: f0636b61c7 (diff-88af4a9df9ead503a5c7774a0455d270dea3ba60e9b0ec1ce550b4c53d3bce3bL172-L175)
2024-03-17 00:38:19 -04:00
..
src make CastTarget::size and CastTarget::llvm_type consistent, remove 2024-03-17 00:38:19 -04:00
Cargo.toml bump itertools to 0.12 2024-03-08 12:34:05 +03:00
messages.ftl Emit a diagnostic for invalid target options 2024-02-03 22:03:25 -05:00
README.md mv compiler to compiler/ 2020-08-30 18:45:07 +03:00

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.