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48d8100543
Ensure strings created with `const_str` get the `unnamed_addr` attribute This function (`const_str`) is only used when we need to invent a string during codegen -- for example, for a panic message to pass when codegening some of the assert/panic/etc terminators (for stuff like divide by zero). AFAICT all other consts, such as the user-defined ones from const eval, should already be getting this attribute (things that come from a ConstAllocation do, for example). Which means that the "unnamed" part is even more true than usual here, these aren't strings that even exist as far as the user can tell. ~~Setting this attribute allows LLVM to merge these constants, leading to significant binary size savings (much more than I would expect). On x86_64-unknown-linux-gnu, t takes a build of ripgrep (release without debug info) from 9.7MiB to 6.0MiB (a savings of over 30%!?), and a build of rustc_driver's shared object from 123MiB to 112MiB (less drastic, but still over 10% reduced).~~ ~~The effect on ripgrep is substantially reduced on macOS for reasons beyond me (I may have fucked up the test), only saving around 0.2MiB, although rustc_driver is still around 10MB or smaller than it had been previously.~~ ~~This raises some questions, such as "does that mean 1/3 of ripgrep was made of division by zero complaints?" I'm not sure, that may be the case. The output of `strings path/to/rg` is \~2MB smaller, so it seems like a lot of it was. Allowing these to be merged presumably also allow functions that contain them to be merged (if the addresses had semantic meaning, then it stands).~~ ~~I intend to do some more analysis here, but I got this up as soon as I realized that this attribute was only missing for internal const strings, and all other ones already get it.~~ Edit: The wins are much more marginal, but there's some argument to do this for the sake of consistency. |
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| .. | ||
| back | ||
| coverageinfo | ||
| debuginfo | ||
| llvm | ||
| abi.rs | ||
| allocator.rs | ||
| asm.rs | ||
| attributes.rs | ||
| base.rs | ||
| builder.rs | ||
| callee.rs | ||
| common.rs | ||
| consts.rs | ||
| context.rs | ||
| declare.rs | ||
| errors.rs | ||
| intrinsic.rs | ||
| lib.rs | ||
| llvm_util.rs | ||
| mono_item.rs | ||
| type_.rs | ||
| type_of.rs | ||
| va_arg.rs | ||
| value.rs | ||