Doesn’t rustc emit LLVM IR? Are there a lot of systems that LLVM doesn’t support?

There are a number of oddball platforms LLVM doesn't support, yeah.

aw1621107 5 hours ago | parent | prev | next [-]

rustc can use a few different backends. By my understanding, the LLVM backend is fully supported, the Cranelift backend is either fully supported or nearly so, and there's a GCC backend in the works. In addition, there's a separate project to create an independent Rust frontend as part of GCC.

Even then, there are still some systems that will support C but won't support Rust any time soon. Systems with old compilers/compiler forks, systems with unusual data types which violate Rust's assumptions (like 8 bit bytes IIRC)

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einpoklum 3 hours ago | parent | prev [-]

Many organizations and environments will not switch themselves to LLVM to hamfist compiled Rust code. Nor is the fact of LLVM supporting something in principle means that it's installed on the relevant OS distribution.

	▲	simonask an hour ago \| parent \| next [-]
		Using LLVM somewhere in the build doesn't require that you compile everything with LLVM. It generates object files, just like GCC, and you can link together object files compiled with each compiler, as long as they don't use compiler-specific runtime libraries (like the C++ standard library, or a polyfill compiler-rt library). `clang-cl` does this with `cl.exe` on Windows.
	▲	oblio an hour ago \| parent \| prev [-]
		If you're developing, you generally have control over the development environment (+/-) and you can install things. Plus that already reduces the audience: set of people with oddball hardware (as someone here put it) intersected with the set of people with locked down development environments. Let alone the fact that conceptually people with locked down environments are precisely those would really want the extra safety offered by Rust. I know that real life is messy but if we don't keep pressing, nothing improves.