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Sema: remove redundant comptime-known initializer tracking

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This logic predates certain Sema enhancements whose behavior it
essentially tries to emulate in one specific case in a problematic way.
In particular, this logic handled initializing comptime-known `const`s
through RLS, which was reworked a few years back in 644041b to not rely
on this logic, and catching runtime fields in comptime-only
initializers, which has since been *correctly* fixed with better checks
in `Sema.storePtr2`. That made the highly complex logic in
`validateStructInit`, `validateUnionInit`, and `zirValidatePtrArrayInit`
entirely redundant. Worse, it was also causing some tracked bugs, as
well as a bug which I have identified and fixed in this PR (a
corresponding behavior test is added).

This commit simplifies union initialization by bringing the runtime
logic more in line with the comptime logic: the tag is now always
populated by `Sema.unionFieldPtr` based on `initializing`, where this
previously happened only in the comptime case (with `validateUnionInit`
instead handling it in the runtime case). Notably, this means that
backends are now able to consider getting a pointer to an inactive union
field as Illegal Behavior, because the `set_union_tag` instruction now
appears *before* the `struct_field_ptr` instruction as you would
probably expect it to.

Resolves: #24520
Resolves: #24595
This commit is contained in:
mlugg 2025-07-29 10:04:15 +01:00
parent 3fbdd58a87
commit a8888afcc0
No known key found for this signature in database
GPG key ID: 3F5B7DCCBF4AF02E
3 changed files with 105 additions and 544 deletions
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629
src/Sema.zig
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@ -4829,13 +4829,13 @@ fn zirValidatePtrStructInit(
agg_ty,
init_src,
instrs,
object_ptr,
),
.@"union" => return sema.validateUnionInit(
block,
agg_ty,
init_src,
instrs,
object_ptr,
),
else => unreachable,
}
@ -4847,164 +4847,28 @@ fn validateUnionInit(
union_ty: Type,
init_src: LazySrcLoc,
instrs: []const Zir.Inst.Index,
union_ptr: Air.Inst.Ref,
) CompileError!void {
const pt = sema.pt;
const zcu = pt.zcu;
const gpa = sema.gpa;
if (instrs.len != 1) {
const msg = msg: {
const msg = try sema.errMsg(
init_src,
"cannot initialize multiple union fields at once; unions can only have one active field",
.{},
);
errdefer msg.destroy(gpa);
for (instrs[1..]) |inst| {
const inst_data = sema.code.instructions.items(.data)[@intFromEnum(inst)].pl_node;
const inst_src = block.src(.{ .node_offset_initializer = inst_data.src_node });
try sema.errNote(inst_src, msg, "additional initializer here", .{});
}
try sema.addDeclaredHereNote(msg, union_ty);
break :msg msg;
};
return sema.failWithOwnedErrorMsg(block, msg);
}
if (block.isComptime() and
(try sema.resolveDefinedValue(block, init_src, union_ptr)) != null)
{
// In this case, comptime machinery already did everything. No work to do here.
if (instrs.len == 1) {
// Trvial validation done, and the union tag was already set by machinery in `unionFieldPtr`.
return;
}
const msg = msg: {
const msg = try sema.errMsg(
init_src,
"cannot initialize multiple union fields at once; unions can only have one active field",
.{},
);
errdefer msg.destroy(sema.gpa);
const field_ptr = instrs[0];
const field_ptr_data = sema.code.instructions.items(.data)[@intFromEnum(field_ptr)].pl_node;
const field_src = block.src(.{ .node_offset_initializer = field_ptr_data.src_node });
const field_ptr_extra = sema.code.extraData(Zir.Inst.Field, field_ptr_data.payload_index).data;
const field_name = try zcu.intern_pool.getOrPutString(
gpa,
pt.tid,
sema.code.nullTerminatedString(field_ptr_extra.field_name_start),
.no_embedded_nulls,
);
const field_index = try sema.unionFieldIndex(block, union_ty, field_name, field_src);
const air_tags = sema.air_instructions.items(.tag);
const air_datas = sema.air_instructions.items(.data);
const field_ptr_ref = sema.inst_map.get(field_ptr).?;
// Our task here is to determine if the union is comptime-known. In such case,
// we erase the runtime AIR instructions for initializing the union, and replace
// the mapping with the comptime value. Either way, we will need to populate the tag.
// We expect to see something like this in the current block AIR:
// %a = alloc(*const U)
// %b = bitcast(*U, %a)
// %c = field_ptr(..., %b)
// %e!= store(%c!, %d!)
// If %d is a comptime operand, the union is comptime.
// If the union is comptime, we want `first_block_index`
// to point at %c so that the bitcast becomes the last instruction in the block.
//
// Store instruction may be missing; if field type has only one possible value, this case is handled below.
//
// In the case of a comptime-known pointer to a union, the
// the field_ptr instruction is missing, so we have to pattern-match
// based only on the store instructions.
// `first_block_index` needs to point to the `field_ptr` if it exists;
// the `store` otherwise.
var first_block_index = block.instructions.items.len;
var block_index = block.instructions.items.len - 1;
var init_val: ?Value = null;
var init_ref: ?Air.Inst.Ref = null;
while (block_index > 0) : (block_index -= 1) {
const store_inst = block.instructions.items[block_index];
if (store_inst.toRef() == field_ptr_ref) {
first_block_index = block_index;
break;
for (instrs[1..]) |inst| {
const inst_data = sema.code.instructions.items(.data)[@intFromEnum(inst)].pl_node;
const inst_src = block.src(.{ .node_offset_initializer = inst_data.src_node });
try sema.errNote(inst_src, msg, "additional initializer here", .{});
}
switch (air_tags[@intFromEnum(store_inst)]) {
.store, .store_safe => {},
else => continue,
}
const bin_op = air_datas[@intFromEnum(store_inst)].bin_op;
var ptr_ref = bin_op.lhs;
if (ptr_ref.toIndex()) |ptr_inst| if (air_tags[@intFromEnum(ptr_inst)] == .bitcast) {
ptr_ref = air_datas[@intFromEnum(ptr_inst)].ty_op.operand;
};
if (ptr_ref != field_ptr_ref) continue;
first_block_index = @min(if (field_ptr_ref.toIndex()) |field_ptr_inst|
std.mem.lastIndexOfScalar(
Air.Inst.Index,
block.instructions.items[0..block_index],
field_ptr_inst,
).?
else
block_index, first_block_index);
init_ref = bin_op.rhs;
init_val = try sema.resolveValue(bin_op.rhs);
break;
}
const tag_ty = union_ty.unionTagTypeHypothetical(zcu);
const tag_val = try pt.enumValueFieldIndex(tag_ty, field_index);
const field_type = union_ty.unionFieldType(tag_val, zcu).?;
if (try sema.typeHasOnePossibleValue(field_type)) |field_only_value| {
init_val = field_only_value;
}
if (init_val) |val| {
// Our task is to delete all the `field_ptr` and `store` instructions, and insert
// instead a single `store` to the result ptr with a comptime union value.
block_index = first_block_index;
for (block.instructions.items[first_block_index..]) |cur_inst| {
switch (air_tags[@intFromEnum(cur_inst)]) {
.struct_field_ptr,
.struct_field_ptr_index_0,
.struct_field_ptr_index_1,
.struct_field_ptr_index_2,
.struct_field_ptr_index_3,
=> if (cur_inst.toRef() == field_ptr_ref) continue,
.bitcast => if (air_datas[@intFromEnum(cur_inst)].ty_op.operand == field_ptr_ref) continue,
.store, .store_safe => {
var ptr_ref = air_datas[@intFromEnum(cur_inst)].bin_op.lhs;
if (ptr_ref.toIndex()) |ptr_inst| if (air_tags[@intFromEnum(ptr_inst)] == .bitcast) {
ptr_ref = air_datas[@intFromEnum(ptr_inst)].ty_op.operand;
};
if (ptr_ref == field_ptr_ref) continue;
},
else => {},
}
block.instructions.items[block_index] = cur_inst;
block_index += 1;
}
block.instructions.shrinkRetainingCapacity(block_index);
const union_val = try pt.internUnion(.{
.ty = union_ty.toIntern(),
.tag = tag_val.toIntern(),
.val = val.toIntern(),
});
const union_init = Air.internedToRef(union_val);
try sema.storePtr2(block, init_src, union_ptr, init_src, union_init, init_src, .store);
return;
} else if (try union_ty.comptimeOnlySema(pt)) {
const src = block.nodeOffset(field_ptr_data.src_node);
return sema.failWithNeededComptime(block, src, .{ .comptime_only = .{
.ty = union_ty,
.msg = .union_init,
} });
}
if (init_ref) |v| try sema.validateRuntimeValue(block, block.nodeOffset(field_ptr_data.src_node), v);
if ((try sema.typeHasOnePossibleValue(tag_ty)) == null) {
const new_tag = Air.internedToRef(tag_val.toIntern());
const set_tag_inst = try block.addBinOp(.set_union_tag, union_ptr, new_tag);
try sema.checkComptimeKnownStore(block, set_tag_inst, LazySrcLoc.unneeded); // `unneeded` since this isn't a "proper" store
}
try sema.addDeclaredHereNote(msg, union_ty);
break :msg msg;
};
return sema.failWithOwnedErrorMsg(block, msg);
}
fn validateStructInit(
@ -5013,187 +4877,62 @@ fn validateStructInit(
struct_ty: Type,
init_src: LazySrcLoc,
instrs: []const Zir.Inst.Index,
struct_ptr: Air.Inst.Ref,
) CompileError!void {
const pt = sema.pt;
const zcu = pt.zcu;
const gpa = sema.gpa;
const ip = &zcu.intern_pool;
const field_indices = try gpa.alloc(u32, instrs.len);
defer gpa.free(field_indices);
// Maps field index to field_ptr index of where it was already initialized.
const found_fields = try gpa.alloc(Zir.Inst.OptionalIndex, struct_ty.structFieldCount(zcu));
// Tracks whether each field was explicitly initialized.
const found_fields = try gpa.alloc(bool, struct_ty.structFieldCount(zcu));
defer gpa.free(found_fields);
@memset(found_fields, .none);
@memset(found_fields, false);
var struct_ptr_zir_ref: Zir.Inst.Ref = undefined;
for (instrs, field_indices) |field_ptr, *field_index| {
for (instrs) |field_ptr| {
const field_ptr_data = sema.code.instructions.items(.data)[@intFromEnum(field_ptr)].pl_node;
const field_src = block.src(.{ .node_offset_initializer = field_ptr_data.src_node });
const field_ptr_extra = sema.code.extraData(Zir.Inst.Field, field_ptr_data.payload_index).data;
struct_ptr_zir_ref = field_ptr_extra.lhs;
const field_name = try ip.getOrPutString(
gpa,
pt.tid,
sema.code.nullTerminatedString(field_ptr_extra.field_name_start),
.no_embedded_nulls,
);
field_index.* = if (struct_ty.isTuple(zcu))
const field_index = if (struct_ty.isTuple(zcu))
try sema.tupleFieldIndex(block, struct_ty, field_name, field_src)
else
try sema.structFieldIndex(block, struct_ty, field_name, field_src);
assert(found_fields[field_index.*] == .none);
found_fields[field_index.*] = field_ptr.toOptional();
assert(found_fields[field_index] == false);
found_fields[field_index] = true;
}
// Our job is simply to deal with default field values. Specifically, any field which was not
// explicitly initialized must have its default value stored to the field pointer, or, if the
// field has no default value, a compile error must be emitted instead.
// In the past, this code had other responsibilities, which involved some nasty AIR rewrites. However,
// that work was actually all redundant:
//
// * If the struct value is comptime-known, field stores remain a perfectly valid way of initializing
// the struct through RLS; there is no need to turn the field stores into one store. Comptime-known
// consts are handled correctly either way thanks to `maybe_comptime_allocs` and friends.
//
// * If the struct type is comptime-only, we need to make sure all of the fields were comptime-known.
// But the comptime-only type means that `struct_ptr` must be a comptime-mutable pointer, so the
// field stores were to comptime-mutable pointers, so have already errored if not comptime-known.
//
// * If the value is runtime-known, then comptime-known fields must be validated as runtime values.
// But this was already handled for every field store by the machinery in `checkComptimeKnownStore`.
var root_msg: ?*Zcu.ErrorMsg = null;
errdefer if (root_msg) |msg| msg.destroy(sema.gpa);
const struct_ptr = try sema.resolveInst(struct_ptr_zir_ref);
if (block.isComptime() and
(try sema.resolveDefinedValue(block, init_src, struct_ptr)) != null)
{
try struct_ty.resolveLayout(pt);
// In this case the only thing we need to do is evaluate the implicit
// store instructions for default field values, and report any missing fields.
// Avoid the cost of the extra machinery for detecting a comptime struct init value.
for (found_fields, 0..) |field_ptr, i_usize| {
const i: u32 = @intCast(i_usize);
if (field_ptr != .none) continue;
try struct_ty.resolveStructFieldInits(pt);
const default_val = struct_ty.structFieldDefaultValue(i, zcu);
if (default_val.toIntern() == .unreachable_value) {
const field_name = struct_ty.structFieldName(i, zcu).unwrap() orelse {
const template = "missing tuple field with index {d}";
if (root_msg) |msg| {
try sema.errNote(init_src, msg, template, .{i});
} else {
root_msg = try sema.errMsg(init_src, template, .{i});
}
continue;
};
const template = "missing struct field: {f}";
const args = .{field_name.fmt(ip)};
if (root_msg) |msg| {
try sema.errNote(init_src, msg, template, args);
} else {
root_msg = try sema.errMsg(init_src, template, args);
}
continue;
}
const field_src = init_src; // TODO better source location
const default_field_ptr = if (struct_ty.isTuple(zcu))
try sema.tupleFieldPtr(block, init_src, struct_ptr, field_src, @intCast(i), true)
else
try sema.structFieldPtrByIndex(block, init_src, struct_ptr, @intCast(i), struct_ty);
const init = Air.internedToRef(default_val.toIntern());
try sema.storePtr2(block, init_src, default_field_ptr, init_src, init, field_src, .store);
}
if (root_msg) |msg| {
try sema.addDeclaredHereNote(msg, struct_ty);
root_msg = null;
return sema.failWithOwnedErrorMsg(block, msg);
}
return;
}
var fields_allow_runtime = true;
var struct_is_comptime = true;
var first_block_index = block.instructions.items.len;
const require_comptime = try struct_ty.comptimeOnlySema(pt);
const air_tags = sema.air_instructions.items(.tag);
const air_datas = sema.air_instructions.items(.data);
try struct_ty.resolveStructFieldInits(pt);
// We collect the comptime field values in case the struct initialization
// ends up being comptime-known.
const field_values = try sema.arena.alloc(InternPool.Index, struct_ty.structFieldCount(zcu));
field: for (found_fields, 0..) |opt_field_ptr, i_usize| {
for (found_fields, 0..) |explicit, i_usize| {
if (explicit) continue;
const i: u32 = @intCast(i_usize);
if (opt_field_ptr.unwrap()) |field_ptr| {
// Determine whether the value stored to this pointer is comptime-known.
const field_ty = struct_ty.fieldType(i, zcu);
if (try sema.typeHasOnePossibleValue(field_ty)) |opv| {
field_values[i] = opv.toIntern();
continue;
}
const field_ptr_ref = sema.inst_map.get(field_ptr).?;
//std.debug.print("validateStructInit (field_ptr_ref=%{d}):\n", .{field_ptr_ref});
//for (block.instructions.items) |item| {
// std.debug.print(" %{d} = {s}\n", .{item, @tagName(air_tags[@intFromEnum(item)])});
//}
// We expect to see something like this in the current block AIR:
// %a = field_ptr(...)
// store(%a, %b)
// With an optional bitcast between the store and the field_ptr.
// If %b is a comptime operand, this field is comptime.
//
// However, in the case of a comptime-known pointer to a struct, the
// the field_ptr instruction is missing, so we have to pattern-match
// based only on the store instructions.
// `first_block_index` needs to point to the `field_ptr` if it exists;
// the `store` otherwise.
// Possible performance enhancement: save the `block_index` between iterations
// of the for loop.
var block_index = block.instructions.items.len;
while (block_index > 0) {
block_index -= 1;
const store_inst = block.instructions.items[block_index];
if (store_inst.toRef() == field_ptr_ref) {
struct_is_comptime = false;
continue :field;
}
switch (air_tags[@intFromEnum(store_inst)]) {
.store, .store_safe => {},
else => continue,
}
const bin_op = air_datas[@intFromEnum(store_inst)].bin_op;
var ptr_ref = bin_op.lhs;
if (ptr_ref.toIndex()) |ptr_inst| if (air_tags[@intFromEnum(ptr_inst)] == .bitcast) {
ptr_ref = air_datas[@intFromEnum(ptr_inst)].ty_op.operand;
};
if (ptr_ref != field_ptr_ref) continue;
first_block_index = @min(if (field_ptr_ref.toIndex()) |field_ptr_inst|
std.mem.lastIndexOfScalar(
Air.Inst.Index,
block.instructions.items[0..block_index],
field_ptr_inst,
).?
else
block_index, first_block_index);
if (!sema.checkRuntimeValue(bin_op.rhs)) fields_allow_runtime = false;
if (try sema.resolveValue(bin_op.rhs)) |val| {
field_values[i] = val.toIntern();
} else if (require_comptime) {
const field_ptr_data = sema.code.instructions.items(.data)[@intFromEnum(field_ptr)].pl_node;
const src = block.nodeOffset(field_ptr_data.src_node);
return sema.failWithNeededComptime(block, src, .{ .comptime_only = .{
.ty = struct_ty,
.msg = .struct_init,
} });
} else {
struct_is_comptime = false;
}
continue :field;
}
struct_is_comptime = false;
continue :field;
}
try struct_ty.resolveStructFieldInits(pt);
const default_val = struct_ty.structFieldDefaultValue(i, zcu);
if (default_val.toIntern() == .unreachable_value) {
const field_name = struct_ty.structFieldName(i, zcu).unwrap() orelse {
@ -5214,70 +4953,6 @@ fn validateStructInit(
}
continue;
}
field_values[i] = default_val.toIntern();
}
if (!struct_is_comptime and !fields_allow_runtime and root_msg == null) {
root_msg = try sema.errMsg(init_src, "runtime value contains reference to comptime var", .{});
try sema.errNote(init_src, root_msg.?, "comptime var pointers are not available at runtime", .{});
}
if (root_msg) |msg| {
try sema.addDeclaredHereNote(msg, struct_ty);
root_msg = null;
return sema.failWithOwnedErrorMsg(block, msg);
}
if (struct_is_comptime) {
// Our task is to delete all the `field_ptr` and `store` instructions, and insert
// instead a single `store` to the struct_ptr with a comptime struct value.
var init_index: usize = 0;
var field_ptr_ref = Air.Inst.Ref.none;
var block_index = first_block_index;
for (block.instructions.items[first_block_index..]) |cur_inst| {
while (field_ptr_ref == .none and init_index < instrs.len) : (init_index += 1) {
const field_ty = struct_ty.fieldType(field_indices[init_index], zcu);
if (try field_ty.onePossibleValue(pt)) |_| continue;
field_ptr_ref = sema.inst_map.get(instrs[init_index]).?;
}
switch (air_tags[@intFromEnum(cur_inst)]) {
.struct_field_ptr,
.struct_field_ptr_index_0,
.struct_field_ptr_index_1,
.struct_field_ptr_index_2,
.struct_field_ptr_index_3,
=> if (cur_inst.toRef() == field_ptr_ref) continue,
.bitcast => if (air_datas[@intFromEnum(cur_inst)].ty_op.operand == field_ptr_ref) continue,
.store, .store_safe => {
var ptr_ref = air_datas[@intFromEnum(cur_inst)].bin_op.lhs;
if (ptr_ref.toIndex()) |ptr_inst| if (air_tags[@intFromEnum(ptr_inst)] == .bitcast) {
ptr_ref = air_datas[@intFromEnum(ptr_inst)].ty_op.operand;
};
if (ptr_ref == field_ptr_ref) {
field_ptr_ref = .none;
continue;
}
},
else => {},
}
block.instructions.items[block_index] = cur_inst;
block_index += 1;
}
block.instructions.shrinkRetainingCapacity(block_index);
const struct_val = try pt.intern(.{ .aggregate = .{
.ty = struct_ty.toIntern(),
.storage = .{ .elems = field_values },
} });
const struct_init = Air.internedToRef(struct_val);
try sema.storePtr2(block, init_src, struct_ptr, init_src, struct_init, init_src, .store);
return;
}
try struct_ty.resolveLayout(pt);
// Our task is to insert `store` instructions for all the default field values.
for (found_fields, 0..) |field_ptr, i| {
if (field_ptr != .none) continue;
const field_src = init_src; // TODO better source location
const default_field_ptr = if (struct_ty.isTuple(zcu))
@ -5285,8 +4960,13 @@ fn validateStructInit(
else
try sema.structFieldPtrByIndex(block, init_src, struct_ptr, @intCast(i), struct_ty);
try sema.checkKnownAllocPtr(block, struct_ptr, default_field_ptr);
const init = Air.internedToRef(field_values[i]);
try sema.storePtr2(block, init_src, default_field_ptr, init_src, init, field_src, .store);
try sema.storePtr2(block, init_src, default_field_ptr, init_src, .fromValue(default_val), field_src, .store);
}
if (root_msg) |msg| {
try sema.addDeclaredHereNote(msg, struct_ty);
root_msg = null;
return sema.failWithOwnedErrorMsg(block, msg);
}
}
@ -5307,15 +4987,14 @@ fn zirValidatePtrArrayInit(
const array_ty = sema.typeOf(array_ptr).childType(zcu).optEuBaseType(zcu);
const array_len = array_ty.arrayLen(zcu);
// Collect the comptime element values in case the array literal ends up
// being comptime-known.
const element_vals = try sema.arena.alloc(
InternPool.Index,
try sema.usizeCast(block, init_src, array_len),
);
// Analagously to `validateStructInit`, our job is to handle default fields; either emitting AIR
// to initialize them, or emitting a compile error if an unspecified field has no default. For
// tuples, there are literally default field values, although they're guaranteed to be comptime
// fields so we don't need to initialize them. For arrays, we may have a sentinel, which is never
// specified so we always need to initialize here. For vectors, there's no such thing.
if (instrs.len != array_len) switch (array_ty.zigTypeTag(zcu)) {
.@"struct" => {
switch (array_ty.zigTypeTag(zcu)) {
.@"struct" => if (instrs.len != array_len) {
var root_msg: ?*Zcu.ErrorMsg = null;
errdefer if (root_msg) |msg| msg.destroy(sema.gpa);
@ -5332,8 +5011,6 @@ fn zirValidatePtrArrayInit(
}
continue;
}
element_vals[i] = default_val;
}
if (root_msg) |msg| {
@ -5341,162 +5018,25 @@ fn zirValidatePtrArrayInit(
return sema.failWithOwnedErrorMsg(block, msg);
}
},
.array => {
.array => if (instrs.len != array_len) {
return sema.fail(block, init_src, "expected {d} array elements; found {d}", .{
array_len, instrs.len,
});
} else if (array_ty.sentinel(zcu)) |sentinel| {
const array_len_ref = try pt.intRef(.usize, array_len);
const sentinel_ptr = try sema.elemPtrArray(block, init_src, init_src, array_ptr, init_src, array_len_ref, true, true);
try sema.checkKnownAllocPtr(block, array_ptr, sentinel_ptr);
try sema.storePtr2(block, init_src, sentinel_ptr, init_src, .fromValue(sentinel), init_src, .store);
},
.vector => {
.vector => if (instrs.len != array_len) {
return sema.fail(block, init_src, "expected {d} vector elements; found {d}", .{
array_len, instrs.len,
});
},
else => unreachable,
};
if (block.isComptime() and
(try sema.resolveDefinedValue(block, init_src, array_ptr)) != null)
{
// In this case the comptime machinery will have evaluated the store instructions
// at comptime so we have almost nothing to do here. However, in case of a
// sentinel-terminated array, the sentinel will not have been populated by
// any ZIR instructions at comptime; we need to do that here.
if (array_ty.sentinel(zcu)) |sentinel_val| {
const array_len_ref = try pt.intRef(.usize, array_len);
const sentinel_ptr = try sema.elemPtrArray(block, init_src, init_src, array_ptr, init_src, array_len_ref, true, true);
const sentinel = Air.internedToRef(sentinel_val.toIntern());
try sema.storePtr2(block, init_src, sentinel_ptr, init_src, sentinel, init_src, .store);
}
return;
}
// If the array has one possible value, the value is always comptime-known.
if (try sema.typeHasOnePossibleValue(array_ty)) |array_opv| {
const array_init = Air.internedToRef(array_opv.toIntern());
try sema.storePtr2(block, init_src, array_ptr, init_src, array_init, init_src, .store);
return;
}
var array_is_comptime = true;
var first_block_index = block.instructions.items.len;
const air_tags = sema.air_instructions.items(.tag);
const air_datas = sema.air_instructions.items(.data);
outer: for (instrs, 0..) |elem_ptr, i| {
// Determine whether the value stored to this pointer is comptime-known.
if (array_ty.isTuple(zcu)) {
if (array_ty.structFieldIsComptime(i, zcu))
try array_ty.resolveStructFieldInits(pt);
if (try array_ty.structFieldValueComptime(pt, i)) |opv| {
element_vals[i] = opv.toIntern();
continue;
}
}
const elem_ptr_ref = sema.inst_map.get(elem_ptr).?;
// We expect to see something like this in the current block AIR:
// %a = elem_ptr(...)
// store(%a, %b)
// With an optional bitcast between the store and the elem_ptr.
// If %b is a comptime operand, this element is comptime.
//
// However, in the case of a comptime-known pointer to an array, the
// the elem_ptr instruction is missing, so we have to pattern-match
// based only on the store instructions.
// `first_block_index` needs to point to the `elem_ptr` if it exists;
// the `store` otherwise.
//
// This is nearly identical to similar logic in `validateStructInit`.
// Possible performance enhancement: save the `block_index` between iterations
// of the for loop.
var block_index = block.instructions.items.len;
while (block_index > 0) {
block_index -= 1;
const store_inst = block.instructions.items[block_index];
if (store_inst.toRef() == elem_ptr_ref) {
array_is_comptime = false;
continue :outer;
}
switch (air_tags[@intFromEnum(store_inst)]) {
.store, .store_safe => {},
else => continue,
}
const bin_op = air_datas[@intFromEnum(store_inst)].bin_op;
var ptr_ref = bin_op.lhs;
if (ptr_ref.toIndex()) |ptr_inst| if (air_tags[@intFromEnum(ptr_inst)] == .bitcast) {
ptr_ref = air_datas[@intFromEnum(ptr_inst)].ty_op.operand;
};
if (ptr_ref != elem_ptr_ref) continue;
first_block_index = @min(if (elem_ptr_ref.toIndex()) |elem_ptr_inst|
std.mem.lastIndexOfScalar(
Air.Inst.Index,
block.instructions.items[0..block_index],
elem_ptr_inst,
).?
else
block_index, first_block_index);
if (try sema.resolveValue(bin_op.rhs)) |val| {
element_vals[i] = val.toIntern();
} else {
array_is_comptime = false;
}
continue :outer;
}
array_is_comptime = false;
continue :outer;
}
if (array_is_comptime) {
if (try sema.resolveDefinedValue(block, init_src, array_ptr)) |ptr_val| {
switch (zcu.intern_pool.indexToKey(ptr_val.toIntern())) {
.ptr => |ptr| switch (ptr.base_addr) {
.comptime_field => return, // This store was validated by the individual elem ptrs.
else => {},
},
else => {},
}
}
// Our task is to delete all the `elem_ptr` and `store` instructions, and insert
// instead a single `store` to the array_ptr with a comptime struct value.
var elem_index: usize = 0;
var elem_ptr_ref = Air.Inst.Ref.none;
var block_index = first_block_index;
for (block.instructions.items[first_block_index..]) |cur_inst| {
while (elem_ptr_ref == .none and elem_index < instrs.len) : (elem_index += 1) {
if (array_ty.isTuple(zcu) and array_ty.structFieldIsComptime(elem_index, zcu)) continue;
elem_ptr_ref = sema.inst_map.get(instrs[elem_index]).?;
}
switch (air_tags[@intFromEnum(cur_inst)]) {
.ptr_elem_ptr => if (cur_inst.toRef() == elem_ptr_ref) continue,
.bitcast => if (air_datas[@intFromEnum(cur_inst)].ty_op.operand == elem_ptr_ref) continue,
.store, .store_safe => {
var ptr_ref = air_datas[@intFromEnum(cur_inst)].bin_op.lhs;
if (ptr_ref.toIndex()) |ptr_inst| if (air_tags[@intFromEnum(ptr_inst)] == .bitcast) {
ptr_ref = air_datas[@intFromEnum(ptr_inst)].ty_op.operand;
};
if (ptr_ref == elem_ptr_ref) {
elem_ptr_ref = .none;
continue;
}
},
else => {},
}
block.instructions.items[block_index] = cur_inst;
block_index += 1;
}
block.instructions.shrinkRetainingCapacity(block_index);
const array_val = try pt.intern(.{ .aggregate = .{
.ty = array_ty.toIntern(),
.storage = .{ .elems = element_vals },
} });
const array_init = Air.internedToRef(array_val);
try sema.storePtr2(block, init_src, array_ptr, init_src, array_init, init_src, .store);
}
}
@ -28015,15 +27555,24 @@ fn unionFieldPtr(
return Air.internedToRef(field_ptr_val.toIntern());
}
if (!initializing and union_obj.flagsUnordered(ip).layout == .auto and block.wantSafety() and
union_ty.unionTagTypeSafety(zcu) != null and union_obj.field_types.len > 1)
{
const wanted_tag_val = try pt.enumValueFieldIndex(.fromInterned(union_obj.enum_tag_ty), enum_field_index);
const wanted_tag = Air.internedToRef(wanted_tag_val.toIntern());
// TODO would it be better if get_union_tag supported pointers to unions?
const union_val = try block.addTyOp(.load, union_ty, union_ptr);
const active_tag = try block.addTyOp(.get_union_tag, .fromInterned(union_obj.enum_tag_ty), union_val);
try sema.addSafetyCheckInactiveUnionField(block, src, active_tag, wanted_tag);
// If the union has a tag, we must either set or or safety check it depending on `initializing`.
tag: {
if (union_ty.containerLayout(zcu) != .auto) break :tag;
const tag_ty: Type = .fromInterned(union_obj.enum_tag_ty);
if (try sema.typeHasOnePossibleValue(tag_ty) != null) break :tag;
// There is a hypothetical non-trivial tag. We must set it even if not there at runtime, but
// only emit a safety check if it's available at runtime (i.e. it's safety-tagged).
const want_tag = try pt.enumValueFieldIndex(tag_ty, enum_field_index);
if (initializing) {
const set_tag_inst = try block.addBinOp(.set_union_tag, union_ptr, .fromValue(want_tag));
try sema.checkComptimeKnownStore(block, set_tag_inst, .unneeded); // `unneeded` since this isn't a "proper" store
} else if (block.wantSafety() and union_obj.hasTag(ip)) {
// The tag exists at runtime (safety tag), so emit a safety check.
// TODO would it be better if get_union_tag supported pointers to unions?
const union_val = try block.addTyOp(.load, union_ty, union_ptr);
const active_tag = try block.addTyOp(.get_union_tag, tag_ty, union_val);
try sema.addSafetyCheckInactiveUnionField(block, src, active_tag, .fromValue(want_tag));
}
}
if (field_ty.zigTypeTag(zcu) == .noreturn) {
_ = try block.addNoOp(.unreach);

14
test/behavior/array.zig
View file

@ -540,7 +540,6 @@ test "sentinel element count towards the ABI size calculation" {
}
test "zero-sized array with recursive type definition" {
if (builtin.zig_backend == .stage2_aarch64) return error.SkipZigTest;
if (builtin.zig_backend == .stage2_sparc64) return error.SkipZigTest; // TODO
if (builtin.zig_backend == .stage2_spirv) return error.SkipZigTest;
@ -1098,3 +1097,16 @@ test "initialize pointer to anyopaque with reference to empty array initializer"
// We can't check the value, but it's zero-bit, so the type matching is good enough.
comptime assert(@TypeOf(loaded) == @TypeOf(.{}));
}
test "sentinel of runtime-known array initialization is populated" {
if (builtin.zig_backend == .stage2_spirv) return error.SkipZigTest;
var rt: u32 = undefined;
rt = 42;
const arr: [1:123]u32 = .{rt};
const elems: [*]const u32 = &arr;
try expect(elems[0] == 42);
try expect(elems[1] == 123);
}

6
test/behavior/field_parent_ptr.zig
View file

@ -2,7 +2,6 @@ const expect = @import("std").testing.expect;
const builtin = @import("builtin");
test "@fieldParentPtr struct" {
if (builtin.zig_backend == .stage2_aarch64) return error.SkipZigTest;
if (builtin.zig_backend == .stage2_spirv) return error.SkipZigTest;
if (builtin.zig_backend == .stage2_riscv64) return error.SkipZigTest;
@ -591,6 +590,7 @@ test "@fieldParentPtr unaligned packed struct" {
if (builtin.zig_backend == .stage2_llvm) return error.SkipZigTest;
if (builtin.zig_backend == .stage2_spirv) return error.SkipZigTest;
if (builtin.zig_backend == .stage2_riscv64) return error.SkipZigTest;
if (builtin.zig_backend == .stage2_aarch64) return error.SkipZigTest;
const C = packed struct {
a: bool = true,
@ -729,6 +729,7 @@ test "@fieldParentPtr aligned packed struct" {
if (builtin.zig_backend == .stage2_llvm) return error.SkipZigTest;
if (builtin.zig_backend == .stage2_spirv) return error.SkipZigTest;
if (builtin.zig_backend == .stage2_riscv64) return error.SkipZigTest;
if (builtin.zig_backend == .stage2_aarch64) return error.SkipZigTest;
const C = packed struct {
a: f32 = 3.14,
@ -866,6 +867,7 @@ test "@fieldParentPtr nested packed struct" {
if (builtin.zig_backend == .stage2_llvm) return error.SkipZigTest;
if (builtin.zig_backend == .stage2_spirv) return error.SkipZigTest;
if (builtin.zig_backend == .stage2_riscv64) return error.SkipZigTest;
if (builtin.zig_backend == .stage2_aarch64) return error.SkipZigTest;
{
const C = packed struct {
@ -1340,7 +1342,6 @@ test "@fieldParentPtr packed struct last zero-bit field" {
}
test "@fieldParentPtr tagged union" {
if (builtin.zig_backend == .stage2_aarch64) return error.SkipZigTest;
if (builtin.zig_backend == .stage2_riscv64) return error.SkipZigTest;
if (builtin.zig_backend == .stage2_spirv) return error.SkipZigTest;
@ -1477,7 +1478,6 @@ test "@fieldParentPtr tagged union" {
}
test "@fieldParentPtr untagged union" {
if (builtin.zig_backend == .stage2_aarch64) return error.SkipZigTest;
if (builtin.zig_backend == .stage2_spirv) return error.SkipZigTest;
if (builtin.zig_backend == .stage2_riscv64) return error.SkipZigTest;