This example compiles a simple function using the LLVM C API through the llvm-sys crate.
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Example of using LLVM from Rust
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| target |
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| [root] | |
| name = "low_down" | |
| version = "0.1.0" | |
| dependencies = [ | |
| "llvm-sys 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)", | |
| ] | |
| [[package]] | |
| name = "bitflags" | |
| version = "0.5.0" | |
| source = "registry+https://github.com/rust-lang/crates.io-index" | |
| [[package]] | |
| name = "gcc" | |
| version = "0.3.37" | |
| source = "registry+https://github.com/rust-lang/crates.io-index" | |
| [[package]] | |
| name = "libc" | |
| version = "0.2.17" | |
| source = "registry+https://github.com/rust-lang/crates.io-index" | |
| [[package]] | |
| name = "llvm-sys" | |
| version = "0.4.0" | |
| source = "registry+https://github.com/rust-lang/crates.io-index" | |
| dependencies = [ | |
| "bitflags 0.5.0 (registry+https://github.com/rust-lang/crates.io-index)", | |
| "gcc 0.3.37 (registry+https://github.com/rust-lang/crates.io-index)", | |
| "libc 0.2.17 (registry+https://github.com/rust-lang/crates.io-index)", | |
| "semver 0.1.20 (registry+https://github.com/rust-lang/crates.io-index)", | |
| ] | |
| [[package]] | |
| name = "semver" | |
| version = "0.1.20" | |
| source = "registry+https://github.com/rust-lang/crates.io-index" | |
| [metadata] | |
| "checksum bitflags 0.5.0 (registry+https://github.com/rust-lang/crates.io-index)" = "4f67931368edf3a9a51d29886d245f1c3db2f1ef0dcc9e35ff70341b78c10d23" | |
| "checksum gcc 0.3.37 (registry+https://github.com/rust-lang/crates.io-index)" = "41337e9dc80ebadf36b4f252bf7440f61bcf34f99caa170e50dcd0f9a0cdb5d8" | |
| "checksum libc 0.2.17 (registry+https://github.com/rust-lang/crates.io-index)" = "044d1360593a78f5c8e5e710beccdc24ab71d1f01bc19a29bcacdba22e8475d8" | |
| "checksum llvm-sys 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)" = "53757e4a2a442608cd0c9d50b555695e299a459a94dc25970d60dc5bc5674449" | |
| "checksum semver 0.1.20 (registry+https://github.com/rust-lang/crates.io-index)" = "d4f410fedcf71af0345d7607d246e7ad15faaadd49d240ee3b24e5dc21a820ac" |
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| [package] | |
| name = "low_down" | |
| version = "0.1.0" | |
| authors = ["Will Speak <[email protected]>"] | |
| [[bin]] | |
| name = "low_down" | |
| path = "main.rs" | |
| [dependencies] | |
| llvm-sys = "*" |
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| //! Example of Using LLVM from Rust | |
| extern crate llvm_sys; | |
| use std::ffi::CStr; | |
| use llvm_sys::prelude::*; | |
| use llvm_sys::{core, target}; | |
| /// Initialise LLVM | |
| /// | |
| /// Makes sure that the parts of LLVM we are going to use are | |
| /// initialised before we do anything with them. | |
| fn initialise_llvm() { | |
| unsafe { | |
| if target::LLVM_InitializeNativeTarget() != 0 { | |
| panic!("Could not initialise target"); | |
| } | |
| if target::LLVM_InitializeNativeAsmPrinter() != 0 { | |
| panic!("Could not initialise ASM Printer"); | |
| } | |
| } | |
| } | |
| /// Compile Module | |
| /// | |
| /// Creates a new LLVM module and compiles a simple funciton in it. | |
| fn compile() -> LLVMModuleRef { | |
| // Create a module to compile the expression into | |
| let mod_name = CStr::from_bytes_with_nul(b"hello\0").unwrap(); | |
| let module = unsafe { core::LLVMModuleCreateWithName(mod_name.as_ptr()) }; | |
| // Create a function type and add a function of that type to the module | |
| let function_type = unsafe { | |
| let int64 = core::LLVMInt64Type(); | |
| let mut param_types = [int64, int64]; | |
| core::LLVMFunctionType(int64, param_types.as_mut_ptr(), param_types.len() as u32, 0) | |
| }; | |
| let function_name = CStr::from_bytes_with_nul(b"test\0").unwrap(); | |
| let function = | |
| unsafe { core::LLVMAddFunction(module, function_name.as_ptr(), function_type) }; | |
| // Create a basic block and add it to the function | |
| let block_name = CStr::from_bytes_with_nul(b"entry\0").unwrap(); | |
| let entry_block = unsafe { core::LLVMAppendBasicBlock(function, block_name.as_ptr()) }; | |
| // Create an LLVM instruction builder and position it at our new | |
| // basic block | |
| let builder = unsafe { | |
| let b = core::LLVMCreateBuilder(); | |
| core::LLVMPositionBuilderAtEnd(b, entry_block); | |
| b | |
| }; | |
| // Fill in the body of the function. | |
| unsafe { | |
| let a = core::LLVMGetParam(function, 0); | |
| let b = core::LLVMGetParam(function, 1); | |
| let temp_name = CStr::from_bytes_with_nul(b"temp.1\0").unwrap(); | |
| let res = core::LLVMBuildAdd(builder, a, b, temp_name.as_ptr()); | |
| core::LLVMBuildRet(builder, res); | |
| } | |
| // Clean up the builder now that we are finished using it. | |
| unsafe { core::LLVMDisposeBuilder(builder) } | |
| module | |
| } | |
| fn main() { | |
| initialise_llvm(); | |
| let module = compile(); | |
| // Dump the LLVM IR to stdout so we can see what we've created | |
| unsafe { core::LLVMDumpModule(module) } | |
| // Clean up the module after we're done with it. | |
| unsafe { core::LLVMDisposeModule(module) } | |
| } |
Author
Not sure i'm afraid. I haven't built this code in quite some time. In my more recent code I
reference the llvm-10 package like this:
llvm-10 = { package = "llvm-sys", version = "100", optional = true }And then import it like this:
#[cfg(feature = "llvm-10")] use llvm_10 as llvm_sys;
Hi, I tried to compile your project (
cargo build) withllvm-sys = "100"and I got the following error:error[E0463]: can't find crate for `llvm_sys` --> main.rs:3:1 | 3 | extern crate llvm_sys; | ^^^^^^^^^^^^^^^^^^^^^^ can't find crateDo you know why I got this error and how to fix it?
EDIT:
Apparently, there is only an error with the latest stable release (
1.54) but it works with1.53
Previously llvm-sys was called llvm_sys this error seems ot have happened for that reason.
Author
This is old code. Previously I think rust normalised crate names when converting them to crate identifiers. Characters such as - in names became _ in the identifier.
As I say. Old code.
Not sure i'm afraid. I haven't built this code in quite some time. In my more recent code I reference the
llvm-10package like this:llvm-10 = { package = "llvm-sys", version = "100", optional = true }And then import it like this:
#[cfg(feature = "llvm-10")] use llvm_10 as llvm_sys;
Then when i try cargo build i get this error:
error[E0433]: failed to resolve: use of undeclared crate or module `llvm_sys`
--> src\main.rs:7:5
|
7 | use llvm_sys::prelude::*;
| ^^^^^^^^ use of undeclared crate or module `llvm_sys`
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Hi,
I tried to compile your project (
cargo build) withllvm-sys = "100"and I got the following error:Do you know why I got this error and how to fix it?
EDIT:
Apparently, there is only an error with the latest stable release (
1.54) but it works with1.53