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Re-implement loop on second input list to List.append, except use an offset pointer instead of doing second_index + first_list_len arithemtic, which is more performant

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This commit is contained in:
Chad Stearns 2020-07-18 14:43:06 -04:00
parent 74bd85afaa
commit a37f6d670b
2 changed files with 81 additions and 13 deletions
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90
compiler/gen/src/llvm/build.rs
View File

@ -1826,13 +1826,7 @@ fn run_low_level<'a, 'ctx, 'env>(
let (first_list, first_list_layout) = &args[0];
match first_list_layout {
Layout::Builtin(Builtin::EmptyList) => {
// In practice, this code cannot be reached, because if a list
// did have the layout of `EmptyList`, then it would not make
// it here. But this code is still run, in the sense that this
// LLVM is still built this case.
empty_list(env)
}
Layout::Builtin(Builtin::EmptyList) => empty_list(env),
Layout::Builtin(Builtin::List(elem_layout)) => {
let first_list_wrapper =
build_expr(env, layout_ids, scope, parent, first_list).into_struct_value();
@ -1947,8 +1941,7 @@ fn run_low_level<'a, 'ctx, 'env>(
)
};
// The pointer to the element from the first list
// in the combined list
// The pointer to the element in the combined list
let combined_list_elem_ptr = unsafe {
builder.build_in_bounds_gep(
combined_list_ptr,
@ -1965,8 +1958,8 @@ fn run_low_level<'a, 'ctx, 'env>(
// #index < first_list_len
let loop_end_cond = builder.build_int_compare(
IntPredicate::ULT,
first_list_len,
curr_index,
first_list_len,
"loopcond",
);
@ -1980,8 +1973,83 @@ fn run_low_level<'a, 'ctx, 'env>(
);
builder.position_at_end(after_loop_bb);
// END
// SECOND LOOP
let index = ctx.i64_type().const_int(0, false);
builder.build_store(start_alloca, index);
let second_loop_bb =
ctx.append_basic_block(parent, "first_list_append_loop");
builder.build_unconditional_branch(second_loop_bb);
builder.position_at_end(second_loop_bb);
// #index = #index + 1
let curr_second_index = builder
.build_load(start_alloca, index_name)
.into_int_value();
let next_second_index = builder.build_int_add(
curr_second_index,
ctx.i64_type().const_int(1, false),
"nextindex",
);
builder.build_store(start_alloca, next_second_index);
let second_list_ptr =
load_list_ptr(builder, second_list_wrapper, ptr_type);
// The pointer to the element in the first list
let second_list_elem_ptr = unsafe {
builder.build_in_bounds_gep(
second_list_ptr,
&[curr_second_index],
"load_index",
)
};
let offset_combined_list_elem_ptr = unsafe {
builder.build_in_bounds_gep(
combined_list_ptr,
&[first_list_len],
"elem",
)
};
// The pointer to the element from the second list
// in the combined list
let combined_list_elem_ptr = unsafe {
builder.build_in_bounds_gep(
offset_combined_list_elem_ptr,
&[curr_second_index],
"load_index_reversed_list",
)
};
let elem = builder.build_load(second_list_elem_ptr, "get_elem");
// Mutate the new array in-place to change the element.
builder.build_store(combined_list_elem_ptr, elem);
// #index < first_list_len
let second_loop_end_cond = builder.build_int_compare(
IntPredicate::ULT,
curr_second_index,
second_list_len,
"loopcond",
);
let second_after_loop_bb =
ctx.append_basic_block(parent, "after_first_loop");
builder.build_conditional_branch(
second_loop_end_cond,
second_loop_bb,
second_after_loop_bb,
);
builder.position_at_end(second_after_loop_bb);
// END
let ptr_bytes = env.ptr_bytes;
let int_type = ptr_int(ctx, ptr_bytes);
let ptr_as_int = builder.build_ptr_to_int(

4
compiler/gen/tests/gen_list.rs
View File

@ -130,8 +130,8 @@ mod gen_list {
assert_evals_to!("List.append [] []", &[], &'static [i64]);
assert_evals_to!("List.append [ 12, 13 ] []", &[12, 13], &'static [i64]);
assert_evals_to!(
"List.append [ 34 ] [ 44, 55 ]",
&[34, 44, 55],
"List.append [ 34, 43 ] [ 64, 55, 66 ]",
&[34, 43, 64, 55, 66],
&'static [i64]
);