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Add llvm generic_compare implementation for integers
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This implements the following calculation posted by Richard on Zulip:
https://roc.zulipchat.com/#narrow/stream/304641-ideas/topic/ordering.2Fsorting.20ability/near/403858126

I'm using the compare.rs module that implements equality as a guide,
some the code has some similarities with that, but also I'm starting
with a blank page to not overwhelm myself, which might result in some
differences (at least at first).

The compare.rs module we might want to rename to eq.rs in a future
commit. That would free up the name compare.rs to implement generic_eq.
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@jwoudenberg
jwoudenberg committed May 4, 2024
1 parent 5a7b74c commit 98a33f9
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Showing 3 changed files with 213 additions and 1 deletion.
14 changes: 13 additions & 1 deletion crates/compiler/gen_llvm/src/llvm/lowlevel.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -55,6 +55,7 @@ use crate::llvm::{
LLVM_SUB_WITH_OVERFLOW,
},
refcounting::PointerToRefcount,
sort::generic_compare,
};

use super::{build::Env, convert::zig_dec_type};
Expand Down Expand Up @@ -1270,7 +1271,18 @@ pub(crate) fn run_low_level<'a, 'ctx>(
BasicValueEnum::IntValue(bool_val)
}
Compare => {
panic!("TODO: implement this")
// Sort.compare : elem, elem -> [LessThan, Equal, GreaterThan]
arguments_with_layouts!((lhs_arg, lhs_layout), (rhs_arg, rhs_layout));

generic_compare(
env,
layout_interner,
layout_ids,
lhs_arg,
rhs_arg,
lhs_layout,
rhs_layout,
)
}
Hash => {
unimplemented!()
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1 change: 1 addition & 0 deletions crates/compiler/gen_llvm/src/llvm/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -9,6 +9,7 @@ pub mod externs;
mod intrinsics;
mod lowlevel;
pub mod refcounting;
pub mod sort;

mod align;
mod erased;
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199 changes: 199 additions & 0 deletions crates/compiler/gen_llvm/src/llvm/sort.rs
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Original file line number Diff line number Diff line change
@@ -0,0 +1,199 @@
use super::build::BuilderExt;
use crate::llvm::build::Env;
use inkwell::values::{BasicValueEnum, IntValue};
use inkwell::IntPredicate;
use roc_builtins::bitcode::IntWidth;
use roc_mono::layout::{
Builtin, InLayout, LayoutIds, LayoutInterner, LayoutRepr, STLayoutInterner,
};

pub fn generic_compare<'a, 'ctx>(
env: &Env<'a, 'ctx, '_>,
layout_interner: &STLayoutInterner<'a>,
_layout_ids: &mut LayoutIds<'a>,
lhs_val: BasicValueEnum<'ctx>,
rhs_val: BasicValueEnum<'ctx>,
lhs_layout: InLayout<'a>,
_rhs_layout: InLayout<'a>,
) -> BasicValueEnum<'ctx> {
let lhs_repr = layout_interner.get_repr(lhs_layout);
let result = match lhs_repr {
LayoutRepr::Builtin(Builtin::Int(int_width)) => {
int_compare(env, lhs_val, rhs_val, int_width)
}
LayoutRepr::Builtin(Builtin::Float(_)) => todo!(),
LayoutRepr::Builtin(Builtin::Bool) => todo!(),
LayoutRepr::Builtin(Builtin::Decimal) => todo!(),
LayoutRepr::Builtin(Builtin::Str) => todo!(),
LayoutRepr::Builtin(Builtin::List(_)) => todo!(),
LayoutRepr::Struct(_) => todo!(),
LayoutRepr::LambdaSet(_) => unreachable!("cannot compare closures"),
LayoutRepr::FunctionPointer(_) => unreachable!("cannot compare function pointers"),
LayoutRepr::Erased(_) => unreachable!("cannot compare erased types"),
LayoutRepr::Union(_) => todo!(),
LayoutRepr::Ptr(_) => todo!(),
LayoutRepr::RecursivePointer(_) => todo!(),
};
BasicValueEnum::IntValue(result)
}

fn int_compare<'ctx>(
env: &Env<'_, 'ctx, '_>,
lhs_val: BasicValueEnum<'ctx>,
rhs_val: BasicValueEnum<'ctx>,
builtin: IntWidth,
) -> IntValue<'ctx> {
// The following calculation will return 0 for equals, 1 for greater than,
// and 2 for less than.
// (a > b) + 2 * (a < b);
let lhs_gt_rhs = int_gt(env, lhs_val, rhs_val, builtin);
let lhs_lt_rhs = int_lt(env, lhs_val, rhs_val, builtin);
let two = env.ptr_int().const_int(2, false);
let lhs_lt_rhs_times_two =
env.builder
.new_build_int_mul(lhs_lt_rhs, two, "lhs_lt_rhs_times_two");
env.builder
.new_build_int_sub(lhs_gt_rhs, lhs_lt_rhs_times_two, "int_compare")
}

fn int_lt<'ctx>(
env: &Env<'_, 'ctx, '_>,
lhs_val: BasicValueEnum<'ctx>,
rhs_val: BasicValueEnum<'ctx>,
builtin: IntWidth,
) -> IntValue<'ctx> {
use IntWidth::*;
match builtin {
I128 => env.builder.new_build_int_compare(
IntPredicate::SLT,
lhs_val.into_int_value(),
rhs_val.into_int_value(),
"lhs_gt_rhs_i28",
),
I64 => env.builder.new_build_int_compare(
IntPredicate::SLT,
lhs_val.into_int_value(),
rhs_val.into_int_value(),
"lhs_gt_rhs_i64",
),
I32 => env.builder.new_build_int_compare(
IntPredicate::SLT,
lhs_val.into_int_value(),
rhs_val.into_int_value(),
"lhs_gt_rhs_i32",
),
I16 => env.builder.new_build_int_compare(
IntPredicate::SLT,
lhs_val.into_int_value(),
rhs_val.into_int_value(),
"lhs_gt_rhs_i16",
),
I8 => env.builder.new_build_int_compare(
IntPredicate::SLT,
lhs_val.into_int_value(),
rhs_val.into_int_value(),
"lhs_gt_rhs_i8",
),
U128 => env.builder.new_build_int_compare(
IntPredicate::ULT,
lhs_val.into_int_value(),
rhs_val.into_int_value(),
"lhs_gt_rhs_u128",
),
U64 => env.builder.new_build_int_compare(
IntPredicate::ULT,
lhs_val.into_int_value(),
rhs_val.into_int_value(),
"lhs_gt_rhs_u64",
),
U32 => env.builder.new_build_int_compare(
IntPredicate::ULT,
lhs_val.into_int_value(),
rhs_val.into_int_value(),
"lhs_gt_rhs_u32",
),
U16 => env.builder.new_build_int_compare(
IntPredicate::ULT,
lhs_val.into_int_value(),
rhs_val.into_int_value(),
"lhs_gt_rhs_u16",
),
U8 => env.builder.new_build_int_compare(
IntPredicate::ULT,
lhs_val.into_int_value(),
rhs_val.into_int_value(),
"lhs_gt_rhs_u8",
),
}
}

fn int_gt<'ctx>(
env: &Env<'_, 'ctx, '_>,
lhs_val: BasicValueEnum<'ctx>,
rhs_val: BasicValueEnum<'ctx>,
builtin: IntWidth,
) -> IntValue<'ctx> {
use IntWidth::*;
match builtin {
I128 => env.builder.new_build_int_compare(
IntPredicate::SGT,
lhs_val.into_int_value(),
rhs_val.into_int_value(),
"lhs_lt_rhs_i28",
),
I64 => env.builder.new_build_int_compare(
IntPredicate::SGT,
lhs_val.into_int_value(),
rhs_val.into_int_value(),
"lhs_lt_rhs_i64",
),
I32 => env.builder.new_build_int_compare(
IntPredicate::SGT,
lhs_val.into_int_value(),
rhs_val.into_int_value(),
"lhs_lt_rhs_i32",
),
I16 => env.builder.new_build_int_compare(
IntPredicate::SGT,
lhs_val.into_int_value(),
rhs_val.into_int_value(),
"lhs_lt_rhs_i16",
),
I8 => env.builder.new_build_int_compare(
IntPredicate::SGT,
lhs_val.into_int_value(),
rhs_val.into_int_value(),
"lhs_lt_rhs_i8",
),
U128 => env.builder.new_build_int_compare(
IntPredicate::UGT,
lhs_val.into_int_value(),
rhs_val.into_int_value(),
"lhs_lt_rhs_u128",
),
U64 => env.builder.new_build_int_compare(
IntPredicate::UGT,
lhs_val.into_int_value(),
rhs_val.into_int_value(),
"lhs_lt_rhs_u64",
),
U32 => env.builder.new_build_int_compare(
IntPredicate::UGT,
lhs_val.into_int_value(),
rhs_val.into_int_value(),
"lhs_lt_rhs_u32",
),
U16 => env.builder.new_build_int_compare(
IntPredicate::UGT,
lhs_val.into_int_value(),
rhs_val.into_int_value(),
"lhs_lt_rhs_u16",
),
U8 => env.builder.new_build_int_compare(
IntPredicate::UGT,
lhs_val.into_int_value(),
rhs_val.into_int_value(),
"lhs_lt_rhs_u8",
),
}
}

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