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Add various attributes to LLVM functions
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Depending on how LLVM decides to optimize things, these attributes may
help improve code generation, though it's difficult to say for certain
how much at this stage.

See #595 for more details.

Changelog: performance
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@yorickpeterse
yorickpeterse committed Nov 29, 2024
1 parent 7a9cad9 commit 9d9f949
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Showing 3 changed files with 110 additions and 13 deletions.
4 changes: 2 additions & 2 deletions compiler/src/llvm/context.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -37,10 +37,10 @@ impl Context {
self.inner.create_type_attribute(id, typ)
}

pub(crate) fn enum_attribute(&self, name: &str, value: u64) -> Attribute {
pub(crate) fn attribute(&self, name: &str) -> Attribute {
let id = Attribute::get_named_enum_kind_id(name);

self.inner.create_enum_attribute(id, value)
self.inner.create_enum_attribute(id, 0)
}

pub(crate) fn pointer_type(&self) -> PointerType<'_> {
Expand Down
89 changes: 85 additions & 4 deletions compiler/src/llvm/module.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -12,7 +12,7 @@ use std::collections::HashMap;
use std::ops::Deref;
use std::path::Path;
use types::module_name::ModuleName;
use types::{CallConvention, MethodId};
use types::{Block, CallConvention, Database, MethodId};

/// A wrapper around an LLVM Module that provides some additional methods.
pub(crate) struct Module<'a, 'ctx> {
Expand Down Expand Up @@ -95,6 +95,7 @@ impl<'a, 'ctx> Module<'a, 'ctx> {

pub(crate) fn add_method(
&self,
db: &Database,
name: &str,
method: MethodId,
) -> FunctionValue<'ctx> {
Expand All @@ -113,6 +114,9 @@ impl<'a, 'ctx> Module<'a, 'ctx> {

fn_val.set_call_conventions(conv);

// The index of the first user-defined argument.
let mut first_arg = if method.is_instance(db) { 1 } else { 0 };

for (idx, &arg) in info.arguments.iter().enumerate() {
match arg {
ArgumentType::StructValue(t) => {
Expand All @@ -122,12 +126,16 @@ impl<'a, 'ctx> Module<'a, 'ctx> {
);
}
ArgumentType::StructReturn(t) => {
// For struct returns we use a hidden first argument, so
// we need to shift the first user-defined argument to
// the right.
first_arg += 1;

let loc = AttributeLoc::Param(0);
let sret =
self.context.type_attribute("sret", t.into());
let noalias = self.context.enum_attribute("noalias", 0);
let nocapt =
self.context.enum_attribute("nocapture", 0);
let noalias = self.context.attribute("noalias");
let nocapt = self.context.attribute("nocapture");

fn_val.add_attribute(loc, sret);
fn_val.add_attribute(loc, noalias);
Expand All @@ -137,6 +145,79 @@ impl<'a, 'ctx> Module<'a, 'ctx> {
}
}

// Add various attributes to the function arguments, in order to
// (hopefully) produce better optimized code.
if method.is_async(db) {
// async methods use the signature `fn(message)` where the
// message is unpacked into the individual arguments.
let loc = AttributeLoc::Param(0);
let ro = self.context.attribute("readonly");
let noal = self.context.attribute("noalias");
let nocap = self.context.attribute("nocapture");

fn_val.add_attribute(loc, ro);
fn_val.add_attribute(loc, noal);
fn_val.add_attribute(loc, nocap);
} else {
let llvm_args = fn_typ.get_param_types();

for (idx, &typ) in method.argument_types(db).enumerate() {
let idx = idx + first_arg;
let loc = AttributeLoc::Param(idx as _);
let ltyp = llvm_args[idx];

if ltyp.is_pointer_type() {
if !typ.allow_mutating(db) {
let attr = self.context.attribute("readonly");

fn_val.add_attribute(loc, attr);
}

if typ.is_uni(db) {
let attr = self.context.attribute("noalias");

fn_val.add_attribute(loc, attr);
} else if typ.is_ref_or_mut(db) {
// We never release memory through borrows.
let attr = self.context.attribute("nofree");

fn_val.add_attribute(loc, attr);
}

// Inko values passed as a pointer (e.g. a borrow) are
// never NULL.
if !typ.is_pointer(db) {
let attr = self.context.attribute("nonnull");

fn_val.add_attribute(loc, attr);
}
}

// Inko's own types are always initialized.
if !typ.is_foreign_type(db) {
let attr = self.context.attribute("noundef");

fn_val.add_attribute(loc, attr);
}
}
}

// Inko doesn't use unwinding, doesn't support it, nor do we support
// binding/dealing with C++.
let nounwind = self.context.attribute("nounwind");

fn_val.add_attribute(AttributeLoc::Function, nounwind);

if method.return_type(db).is_never(db) {
let cold = self.context.attribute("cold");
let noin = self.context.attribute("noinline");
let noret = self.context.attribute("noreturn");

fn_val.add_attribute(AttributeLoc::Function, cold);
fn_val.add_attribute(AttributeLoc::Function, noin);
fn_val.add_attribute(AttributeLoc::Function, noret);
}

fn_val
})
}
Expand Down
30 changes: 23 additions & 7 deletions compiler/src/llvm/passes.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -941,8 +941,8 @@ impl<'shared, 'module, 'ctx> LowerMethod<'shared, 'module, 'ctx> {
module: &'module mut Module<'shared, 'ctx>,
method: &'shared Method,
) -> Self {
let function =
module.add_method(&shared.names.methods[&method.id], method.id);
let name = &shared.names.methods[&method.id];
let function = module.add_method(&shared.state.db, name, method.id);
let builder = Builder::new(module.context, function);
let entry_block = builder.add_block();

Expand Down Expand Up @@ -1820,7 +1820,11 @@ impl<'shared, 'module, 'ctx> LowerMethod<'shared, 'module, 'ctx> {
self.set_debug_location(ins.location);

let name = ins.method.name(&self.shared.state.db);
let fn_val = self.module.add_method(name, ins.method);
let fn_val = self.module.add_method(
&self.shared.state.db,
name,
ins.method,
);
let kind = CallKind::Direct(fn_val);
let layout = &self.layouts.methods[ins.method.0 as usize];

Expand All @@ -1830,7 +1834,11 @@ impl<'shared, 'module, 'ctx> LowerMethod<'shared, 'module, 'ctx> {
self.set_debug_location(ins.location);

let func_name = &self.shared.names.methods[&ins.method];
let func = self.module.add_method(func_name, ins.method);
let func = self.module.add_method(
&self.shared.state.db,
func_name,
ins.method,
);
let kind = CallKind::Direct(func);
let layout = &self.layouts.methods[ins.method.0 as usize];

Expand All @@ -1840,7 +1848,11 @@ impl<'shared, 'module, 'ctx> LowerMethod<'shared, 'module, 'ctx> {
self.set_debug_location(ins.location);

let name = &self.shared.names.methods[&ins.method];
let func = self.module.add_method(name, ins.method);
let func = self.module.add_method(
&self.shared.state.db,
name,
ins.method,
);
let kind = CallKind::Direct(func);
let layout = &self.layouts.methods[ins.method.0 as usize];

Expand Down Expand Up @@ -2093,7 +2105,7 @@ impl<'shared, 'module, 'ctx> LowerMethod<'shared, 'module, 'ctx> {
let method_name = &self.shared.names.methods[&ins.method];
let method = self
.module
.add_method(method_name, ins.method)
.add_method(&self.shared.state.db, method_name, ins.method)
.as_global_value()
.as_pointer_value()
.into();
Expand Down Expand Up @@ -2282,7 +2294,11 @@ impl<'shared, 'module, 'ctx> LowerMethod<'shared, 'module, 'ctx> {
Instruction::MethodPointer(ins) => {
let reg_var = self.variables[&ins.register];
let func_name = &self.shared.names.methods[&ins.method];
let func = self.module.add_method(func_name, ins.method);
let func = self.module.add_method(
&self.shared.state.db,
func_name,
ins.method,
);
let ptr = func.as_global_value().as_pointer_value();

self.builder.store(reg_var, ptr);
Expand Down

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