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introduce Ownership to list layout
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Folkert
parent
d784f62cd3
commit
22471167d3
5 changed files with 213 additions and 16 deletions
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@ -720,22 +720,187 @@ pub fn build_expr<'a, 'ctx, 'env>(
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}
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RunLowLevel(op, args) => run_low_level(env, layout_ids, scope, parent, *op, args),
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DecAfter(_, expr) => build_expr(env, layout_ids, scope, parent, expr),
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DecAfter(symbol, expr) => {
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match scope.get(symbol) {
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None => panic!("There was no entry for {:?} in scope {:?}", symbol, scope),
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Some((layout, ptr)) => {
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match layout {
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Layout::Builtin(Builtin::List(_, elem_layout)) if false => {
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// first run the body
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let body = build_expr(env, layout_ids, scope, parent, expr);
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let wrapper_struct = env
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.builder
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.build_load(*ptr, symbol.ident_string(&env.interns))
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.into_struct_value();
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decrement_refcount_list(env, parent, wrapper_struct, body)
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}
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_ => {
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// not refcounted, do nothing special
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build_expr(env, layout_ids, scope, parent, expr)
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}
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}
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}
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}
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}
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Reuse(_, expr) => build_expr(env, layout_ids, scope, parent, expr),
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Reset(_, expr) => build_expr(env, layout_ids, scope, parent, expr),
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}
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}
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fn refcount_is_one_comparison<'ctx>(
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builder: &Builder<'ctx>,
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context: &'ctx Context,
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refcount: IntValue<'ctx>,
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) -> IntValue<'ctx> {
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let refcount_one: IntValue<'ctx> = context
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.i64_type()
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.const_int((std::usize::MAX - 1) as _, false);
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// Note: Check for refcount < refcount_1 as the "true" condition,
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// to avoid misprediction. (In practice this should usually pass,
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// and CPUs generally default to predicting that a forward jump
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// shouldn't be taken; that is, they predict "else" won't be taken.)
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builder.build_int_compare(
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IntPredicate::ULT,
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refcount,
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refcount_one,
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"refcount_one_check",
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)
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}
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fn list_get_refcount_ptr<'a, 'ctx, 'env>(
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env: &Env<'a, 'ctx, 'env>,
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list_wrapper: StructValue<'ctx>,
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) -> PointerValue<'ctx> {
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let builder = env.builder;
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let ctx = env.context;
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// basic_type_from_layout(env.arena, ctx, elem_layout, env.ptr_bytes);
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let elem_type = ctx.i64_type().into();
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let ptr_type = get_ptr_type(&elem_type, AddressSpace::Generic);
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// Load the pointer to the array data
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let array_data_ptr = load_list_ptr(builder, list_wrapper, ptr_type);
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// get the refcount
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let zero_index = ctx.i64_type().const_zero();
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unsafe {
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// SAFETY
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// index 0 is always defined for lists.
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builder.build_in_bounds_gep(array_data_ptr, &[zero_index], "refcount_index")
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}
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}
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fn increment_refcount_list<'a, 'ctx, 'env>(
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env: &Env<'a, 'ctx, 'env>,
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original_wrapper: StructValue<'ctx>,
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body: BasicValueEnum<'ctx>,
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) -> BasicValueEnum<'ctx> {
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let builder = env.builder;
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let ctx = env.context;
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let refcount_ptr = list_get_refcount_ptr(env, original_wrapper);
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let refcount = env
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.builder
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.build_load(refcount_ptr, "get_refcount")
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.into_int_value();
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// our refcount 0 is actually usize::MAX, so incrementing the refcount means decrementing this value.
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let decremented = env.builder.build_int_sub(
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refcount,
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ctx.i64_type().const_int(1 as u64, false),
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"new_refcount",
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);
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// Mutate the new array in-place to change the element.
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builder.build_store(refcount_ptr, decremented);
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body
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}
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fn decrement_refcount_list<'a, 'ctx, 'env>(
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env: &Env<'a, 'ctx, 'env>,
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parent: FunctionValue<'ctx>,
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original_wrapper: StructValue<'ctx>,
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body: BasicValueEnum<'ctx>,
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) -> BasicValueEnum<'ctx> {
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let builder = env.builder;
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let ctx = env.context;
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let refcount_ptr = list_get_refcount_ptr(env, original_wrapper);
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let refcount = env
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.builder
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.build_load(refcount_ptr, "get_refcount")
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.into_int_value();
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let comparison = refcount_is_one_comparison(builder, env.context, refcount);
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// the refcount is higher than 1, write the decremented value
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let build_then = || {
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// our refcount 0 is actually usize::MAX, so decrementing the refcount means incrementing this value.
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let decremented = env.builder.build_int_add(
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ctx.i64_type().const_int(1 as u64, false),
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refcount,
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"new_refcount",
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);
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// Mutate the new array in-place to change the element.
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builder.build_store(refcount_ptr, decremented);
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body
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};
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// refcount is one, and will be decremented. This list can be freed
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let build_else = || {
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let array_data_ptr = load_list_ptr(
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builder,
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original_wrapper,
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ctx.i64_type().ptr_type(AddressSpace::Generic),
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);
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let free = builder.build_free(array_data_ptr);
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builder.insert_instruction(&free, None);
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body
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};
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let ret_type = body.get_type();
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build_basic_phi2(
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env,
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parent,
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comparison,
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build_then,
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build_else,
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ret_type.into(),
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)
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}
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fn load_symbol<'a, 'ctx, 'env>(
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env: &Env<'a, 'ctx, 'env>,
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scope: &Scope<'a, 'ctx>,
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symbol: &Symbol,
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) -> BasicValueEnum<'ctx> {
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match scope.get(symbol) {
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Some((_, ptr)) => env
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.builder
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.build_load(*ptr, symbol.ident_string(&env.interns)),
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Some((layout, ptr)) => match layout {
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Layout::Builtin(Builtin::List(_, _)) if false => {
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let load = env
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.builder
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.build_load(*ptr, symbol.ident_string(&env.interns));
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let wrapper_struct = env
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.builder
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.build_load(*ptr, symbol.ident_string(&env.interns))
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.into_struct_value();
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increment_refcount_list(env, wrapper_struct, load)
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}
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_ => env
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.builder
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.build_load(*ptr, symbol.ident_string(&env.interns)),
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},
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None => panic!("There was no entry for {:?} in scope {:?}", symbol, scope),
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}
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}
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@ -1670,7 +1835,7 @@ fn run_low_level<'a, 'ctx, 'env>(
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let (list, list_layout) = &args[0];
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match list_layout {
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Layout::Builtin(Builtin::List(elem_layout)) => {
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Layout::Builtin(Builtin::List(_, elem_layout)) => {
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let wrapper_struct =
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build_expr(env, layout_ids, scope, parent, list).into_struct_value();
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@ -1979,7 +2144,7 @@ fn run_low_level<'a, 'ctx, 'env>(
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build_expr(env, layout_ids, scope, parent, &args[1].0).into_int_value();
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match list_layout {
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Layout::Builtin(Builtin::List(elem_layout)) => {
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Layout::Builtin(Builtin::List(_, elem_layout)) => {
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let ctx = env.context;
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let elem_type =
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basic_type_from_layout(env.arena, ctx, elem_layout, env.ptr_bytes);
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@ -2129,7 +2294,7 @@ fn list_append<'a, 'ctx, 'env>(
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Layout::Builtin(Builtin::EmptyList) => {
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match second_list_layout {
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Layout::Builtin(Builtin::EmptyList) => empty_list(env),
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Layout::Builtin(Builtin::List(elem_layout)) => {
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Layout::Builtin(Builtin::List(_, elem_layout)) => {
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// THIS IS A COPY AND PASTE
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// All the code under the Layout::Builtin(Builtin::List()) match branch
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// is the same as what is under `if_first_list_is_empty`. Re-using
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@ -2175,7 +2340,7 @@ fn list_append<'a, 'ctx, 'env>(
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}
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}
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}
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Layout::Builtin(Builtin::List(elem_layout)) => {
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Layout::Builtin(Builtin::List(_, elem_layout)) => {
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let first_list_wrapper =
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build_expr(env, layout_ids, scope, parent, first_list).into_struct_value();
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@ -2214,7 +2379,7 @@ fn list_append<'a, 'ctx, 'env>(
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BasicValueEnum::StructValue(new_wrapper)
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}
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Layout::Builtin(Builtin::List(_)) => {
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Layout::Builtin(Builtin::List(_, _)) => {
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// second_list_len > 0
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// We do this check to avoid allocating memory. If the second input
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// list is empty, then we can just return the first list cloned
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@ -2453,7 +2618,7 @@ fn list_append<'a, 'ctx, 'env>(
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let if_first_list_is_empty = || {
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match second_list_layout {
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Layout::Builtin(Builtin::EmptyList) => empty_list(env),
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Layout::Builtin(Builtin::List(elem_layout)) => {
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Layout::Builtin(Builtin::List(_, elem_layout)) => {
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// second_list_len > 0
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// We do this check to avoid allocating memory. If the second input
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// list is empty, then we can just return the first list cloned
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