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use llvm_sys::{
core::{
LLVMCreateFunctionPassManagerForModule, LLVMDisposePassManager,
LLVMInitializeFunctionPassManager, LLVMRunFunctionPassManager,
},
prelude::LLVMPassManagerRef,
transforms::{
instcombine::LLVMAddInstructionCombiningPass,
scalar::{LLVMAddCFGSimplificationPass, LLVMAddNewGVNPass, LLVMAddReassociatePass},
},
};
use std::marker::PhantomData;
use super::{FnValue, Module};
/// Wrapper for a LLVM Function PassManager (legacy).
pub struct FunctionPassManager<'llvm> {
fpm: LLVMPassManagerRef,
_ctx: PhantomData<&'llvm ()>,
}
impl<'llvm> FunctionPassManager<'llvm> {
/// Create a new Function PassManager with the following optimization passes
/// - InstructionCombiningPass
/// - ReassociatePass
/// - NewGVNPass
/// - CFGSimplificationPass
///
/// The list of selected optimization passes is taken from the tutorial chapter [LLVM
/// Optimization Passes](https://llvm.org/docs/tutorial/MyFirstLanguageFrontend/LangImpl04.html#id3).
pub fn with_ctx(module: &'llvm Module) -> FunctionPassManager<'llvm> {
let fpm = unsafe {
// Borrows module reference.
LLVMCreateFunctionPassManagerForModule(module.module())
};
assert!(!fpm.is_null());
unsafe {
// Do simple "peephole" optimizations and bit-twiddling optzns.
LLVMAddInstructionCombiningPass(fpm);
// Reassociate expressions.
LLVMAddReassociatePass(fpm);
// Eliminate Common SubExpressions.
LLVMAddNewGVNPass(fpm);
// Simplify the control flow graph (deleting unreachable blocks, etc).
LLVMAddCFGSimplificationPass(fpm);
let fail = LLVMInitializeFunctionPassManager(fpm);
assert_eq!(fail, 0);
}
FunctionPassManager {
fpm,
_ctx: PhantomData,
}
}
/// Run the optimization passes registered with the Function PassManager on the function
/// referenced by `fn_value`.
pub fn run(&'llvm self, fn_value: FnValue<'llvm>) {
unsafe {
// Returns 1 if any of the passes modified the function, false otherwise.
LLVMRunFunctionPassManager(self.fpm, fn_value.value_ref());
}
}
}
impl Drop for FunctionPassManager<'_> {
fn drop(&mut self) {
unsafe {
LLVMDisposePassManager(self.fpm);
}
}
}
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