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sema: rework the comptime representation of comptime unions

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When the tag is not known, it's set to `.none`. In this case, the value is either an
array of bytes (for extern unions) or an integer (for packed unions).
This commit is contained in:
kcbanner
2023-09-23 13:03:03 -04:00
parent 2fddd767ba
commit f2a24b48e1
12 changed files with 148 additions and 139 deletions
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6
src/InternPool.zig
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@@ -1105,7 +1105,10 @@ pub const Key = union(enum) {
pub const Union = extern struct {
/// This is the union type; not the field type.
ty: Index,
/// Indicates the active field.
/// Indicates the active field. This could be `none`, which indicates the tag is not known. `none` is only a valid value for extern and packed unions.
/// In those cases, the type of `val` is:
/// extern: a u8 array of the same byte length as the union
/// packed: an unsigned integer with the same bit size as the union
tag: Index,
/// The value of the active field.
val: Index,
@@ -5130,7 +5133,6 @@ pub fn get(ip: *InternPool, gpa: Allocator, key: Key) Allocator.Error!Index {
.un => |un| {
assert(un.ty != .none);
assert(un.tag != .none);
assert(un.val != .none);
ip.items.appendAssumeCapacity(.{
.tag = .union_value,

31
src/Module.zig
View File

@@ -5823,7 +5823,7 @@ pub fn markReferencedDeclsAlive(mod: *Module, val: Value) Allocator.Error!void {
.aggregate => |aggregate| for (aggregate.storage.values()) |elem|
try mod.markReferencedDeclsAlive(elem.toValue()),
.un => |un| {
try mod.markReferencedDeclsAlive(un.tag.toValue());
if (un.tag != .none) try mod.markReferencedDeclsAlive(un.tag.toValue());
try mod.markReferencedDeclsAlive(un.val.toValue());
},
else => {},
@@ -6607,7 +6607,7 @@ pub fn unionFieldNormalAlignment(mod: *Module, u: InternPool.UnionType, field_in
pub fn unionTagFieldIndex(mod: *Module, u: InternPool.UnionType, enum_tag: Value) ?u32 {
const ip = &mod.intern_pool;
if (enum_tag.toIntern() == .undef) return null;
if (enum_tag.toIntern() == .none) return null;
assert(ip.typeOf(enum_tag.toIntern()) == u.enum_tag_ty);
const enum_type = ip.indexToKey(u.enum_tag_ty).enum_type;
return enum_type.tagValueIndex(ip, enum_tag.toIntern());
@@ -6673,30 +6673,3 @@ pub fn structPackedFieldBitOffset(
}
unreachable; // index out of bounds
}
pub fn unionLargestField(mod: *Module, u: InternPool.UnionType) struct {
ty: Type,
index: u32,
size: u64,
} {
const fields = u.field_types.get(&mod.intern_pool);
assert(fields.len != 0);
var largest_field_ty: Type = undefined;
var largest_field_size: u64 = 0;
var largest_field_index: u32 = 0;
for (fields, 0..) |union_field, i| {
const field_ty = union_field.toType();
const size: u32 = @intCast(field_ty.abiSize(mod));
if (size > largest_field_size) {
largest_field_ty = field_ty;
largest_field_size = size;
largest_field_index = @intCast(i);
}
}
return .{
.ty = largest_field_ty,
.index = largest_field_index,
.size = largest_field_size,
};
}

16
src/Sema.zig
View File

@@ -12124,7 +12124,7 @@ fn zirSwitchBlock(sema: *Sema, block: *Block, inst: Zir.Inst.Index, operand_is_r
const analyze_body = if (union_originally) blk: {
const item_val = sema.resolveConstLazyValue(block, .unneeded, item, undefined) catch unreachable;
const field_ty = maybe_union_ty.unionFieldType(item_val, mod);
const field_ty = maybe_union_ty.unionFieldType(item_val, mod).?;
break :blk field_ty.zigTypeTag(mod) != .NoReturn;
} else true;
@@ -12250,7 +12250,7 @@ fn zirSwitchBlock(sema: *Sema, block: *Block, inst: Zir.Inst.Index, operand_is_r
const analyze_body = if (union_originally) blk: {
const item_val = sema.resolveConstValue(block, .unneeded, item, undefined) catch unreachable;
const field_ty = maybe_union_ty.unionFieldType(item_val, mod);
const field_ty = maybe_union_ty.unionFieldType(item_val, mod).?;
break :blk field_ty.zigTypeTag(mod) != .NoReturn;
} else true;
@@ -12304,7 +12304,7 @@ fn zirSwitchBlock(sema: *Sema, block: *Block, inst: Zir.Inst.Index, operand_is_r
const analyze_body = if (union_originally)
for (items) |item| {
const item_val = sema.resolveConstValue(block, .unneeded, item, undefined) catch unreachable;
const field_ty = maybe_union_ty.unionFieldType(item_val, mod);
const field_ty = maybe_union_ty.unionFieldType(item_val, mod).?;
if (field_ty.zigTypeTag(mod) != .NoReturn) break true;
} else false
else
@@ -12456,7 +12456,7 @@ fn zirSwitchBlock(sema: *Sema, block: *Block, inst: Zir.Inst.Index, operand_is_r
case_block.wip_capture_scope = child_block.wip_capture_scope;
const analyze_body = if (union_originally) blk: {
const field_ty = maybe_union_ty.unionFieldType(item_val, mod);
const field_ty = maybe_union_ty.unionFieldType(item_val, mod).?;
break :blk field_ty.zigTypeTag(mod) != .NoReturn;
} else true;
@@ -16496,7 +16496,7 @@ fn analyzeCmpUnionTag(
if (try sema.resolveMaybeUndefVal(coerced_tag)) |enum_val| {
if (enum_val.isUndef(mod)) return mod.undefRef(Type.bool);
const field_ty = union_ty.unionFieldType(enum_val, mod);
const field_ty = union_ty.unionFieldType(enum_val, mod).?;
if (field_ty.zigTypeTag(mod) == .NoReturn) {
return .bool_false;
}
@@ -27208,7 +27208,11 @@ fn unionFieldVal(
if (tag_matches) {
return Air.internedToRef(un.val);
} else {
const old_ty = union_ty.unionFieldType(un.tag.toValue(), mod);
const old_ty = if (un.tag == .none)
ip.typeOf(un.val).toType()
else
union_ty.unionFieldType(un.tag.toValue(), mod).?;
if (try sema.bitCastVal(block, src, un.val.toValue(), old_ty, field_ty, 0)) |new_val| {
return Air.internedToRef(new_val.toIntern());
}

24
src/TypedValue.zig
View File

@@ -92,10 +92,14 @@ pub fn print(
.val = union_val.tag,
}, writer, level - 1, mod);
try writer.writeAll(" = ");
try print(.{
.ty = ty.unionFieldType(union_val.tag, mod),
.val = union_val.val,
}, writer, level - 1, mod);
if (ty.unionFieldType(union_val.tag, mod)) |field_ty| {
try print(.{
.ty = field_ty,
.val = union_val.val,
}, writer, level - 1, mod);
} else {
return writer.writeAll("(no tag)");
}
return writer.writeAll(" }");
},
@@ -409,10 +413,14 @@ pub fn print(
.val = un.tag.toValue(),
}, writer, level - 1, mod);
try writer.writeAll(" = ");
try print(.{
.ty = ty.unionFieldType(un.tag.toValue(), mod),
.val = un.val.toValue(),
}, writer, level - 1, mod);
if (ty.unionFieldType(un.tag.toValue(), mod)) |field_ty| {
try print(.{
.ty = field_ty,
.val = un.val.toValue(),
}, writer, level - 1, mod);
} else {
try writer.writeAll("(no tag)");
}
} else try writer.writeAll("...");
return writer.writeAll(" }");
},

5
src/arch/wasm/CodeGen.zig
View File

@@ -3259,10 +3259,7 @@ fn lowerConstant(func: *CodeGen, arg_val: Value, ty: Type) InnerError!WValue {
.un => |un| {
// in this case we have a packed union which will not be passed by reference.
const union_obj = mod.typeToUnion(ty).?;
const field_index = mod.unionTagFieldIndex(union_obj, un.tag.toValue()) orelse f: {
assert(union_obj.getLayout(ip) == .Extern);
break :f mod.unionLargestField(union_obj).index;
};
const field_index = mod.unionTagFieldIndex(union_obj, un.tag.toValue()).?;
const field_ty = union_obj.field_types.get(ip)[field_index].toType();
return func.lowerConstant(un.val.toValue(), field_ty);
},

5
src/codegen.zig
View File

@@ -583,10 +583,7 @@ pub fn generateSymbol(
}
const union_obj = mod.typeToUnion(typed_value.ty).?;
const field_index = typed_value.ty.unionTagFieldIndex(un.tag.toValue(), mod) orelse f: {
assert(union_obj.getLayout(ip) == .Extern);
break :f mod.unionLargestField(union_obj).index;
};
const field_index = typed_value.ty.unionTagFieldIndex(un.tag.toValue(), mod).?;
const field_ty = union_obj.field_types.get(ip)[field_index].toType();
if (!field_ty.hasRuntimeBits(mod)) {

5
src/codegen/c.zig
View File

@@ -1439,10 +1439,7 @@ pub const DeclGen = struct {
}
const union_obj = mod.typeToUnion(ty).?;
const field_i = mod.unionTagFieldIndex(union_obj, un.tag.toValue()) orelse f: {
assert(union_obj.getLayout(ip) == .Extern);
break :f mod.unionLargestField(union_obj).index;
};
const field_i = mod.unionTagFieldIndex(union_obj, un.tag.toValue()).?;
const field_ty = union_obj.field_types.get(ip)[field_i].toType();
const field_name = union_obj.field_names.get(ip)[field_i];
if (union_obj.getLayout(ip) == .Packed) {

58
src/codegen/llvm.zig
View File

@@ -4108,28 +4108,28 @@ pub const Object = struct {
if (layout.payload_size == 0) return o.lowerValue(un.tag);
const union_obj = mod.typeToUnion(ty).?;
const field_index = mod.unionTagFieldIndex(union_obj, un.tag.toValue()) orelse f: {
assert(union_obj.getLayout(ip) == .Extern);
break :f mod.unionLargestField(union_obj).index;
};
const container_layout = union_obj.getLayout(ip);
const field_ty = union_obj.field_types.get(ip)[field_index].toType();
if (union_obj.getLayout(ip) == .Packed) {
if (!field_ty.hasRuntimeBits(mod)) return o.builder.intConst(union_ty, 0);
const small_int_val = try o.builder.castConst(
if (field_ty.isPtrAtRuntime(mod)) .ptrtoint else .bitcast,
try o.lowerValue(un.val),
try o.builder.intType(@intCast(field_ty.bitSize(mod))),
);
return o.builder.convConst(.unsigned, small_int_val, union_ty);
}
var need_unnamed = false;
const payload = if (un.tag != .none) p: {
const field_index = mod.unionTagFieldIndex(union_obj, un.tag.toValue()).?;
const field_ty = union_obj.field_types.get(ip)[field_index].toType();
if (container_layout == .Packed) {
if (!field_ty.hasRuntimeBits(mod)) return o.builder.intConst(union_ty, 0);
const small_int_val = try o.builder.castConst(
if (field_ty.isPtrAtRuntime(mod)) .ptrtoint else .bitcast,
try o.lowerValue(un.val),
try o.builder.intType(@intCast(field_ty.bitSize(mod))),
);
return o.builder.convConst(.unsigned, small_int_val, union_ty);
}
// Sometimes we must make an unnamed struct because LLVM does
// not support bitcasting our payload struct to the true union payload type.
// Instead we use an unnamed struct and every reference to the global
// must pointer cast to the expected type before accessing the union.
need_unnamed = layout.most_aligned_field != field_index;
// Sometimes we must make an unnamed struct because LLVM does
// not support bitcasting our payload struct to the true union payload type.
// Instead we use an unnamed struct and every reference to the global
// must pointer cast to the expected type before accessing the union.
var need_unnamed = layout.most_aligned_field != field_index;
const payload = p: {
if (!field_ty.hasRuntimeBitsIgnoreComptime(mod)) {
const padding_len = layout.payload_size;
break :p try o.builder.undefConst(try o.builder.arrayType(padding_len, .i8));
@@ -4147,9 +4147,23 @@ pub const Object = struct {
try o.builder.structType(.@"packed", &.{ payload_ty, padding_ty }),
&.{ payload, try o.builder.undefConst(padding_ty) },
);
};
const payload_ty = payload.typeOf(&o.builder);
} else p: {
assert(layout.tag_size == 0);
const union_val = try o.lowerValue(un.val);
if (container_layout == .Packed) {
const bitcast_val = try o.builder.castConst(
.bitcast,
union_val,
try o.builder.intType(@intCast(ty.bitSize(mod))),
);
return o.builder.convConst(.unsigned, bitcast_val, union_ty);
}
need_unnamed = true;
break :p union_val;
};
const payload_ty = payload.typeOf(&o.builder);
if (layout.tag_size == 0) return o.builder.structConst(if (need_unnamed)
try o.builder.structType(union_ty.structKind(&o.builder), &.{payload_ty})
else

5
src/codegen/spirv.zig
View File

@@ -838,10 +838,7 @@ pub const DeclGen = struct {
return dg.todo("packed union constants", .{});
}
const active_field = ty.unionTagFieldIndex(un.tag.toValue(), dg.module) orelse f: {
assert(union_obj.getLayout(ip) == .Extern);
break :f mod.unionLargestField(union_obj).index;
};
const active_field = ty.unionTagFieldIndex(un.tag.toValue(), dg.module).?;
const active_field_ty = union_obj.field_types.get(ip)[active_field].toType();
const has_tag = layout.tag_size != 0;

10
src/type.zig
View File

@@ -1658,6 +1658,7 @@ pub const Type = struct {
const field_ty = union_obj.field_types.get(ip)[field_index];
size = @max(size, try bitSizeAdvanced(field_ty.toType(), mod, opt_sema));
}
return size;
},
.opaque_type => unreachable,
@@ -1926,15 +1927,12 @@ pub const Type = struct {
return union_obj.enum_tag_ty.toType();
}
pub fn unionFieldType(ty: Type, enum_tag: Value, mod: *Module) Type {
pub fn unionFieldType(ty: Type, enum_tag: Value, mod: *Module) ?Type {
const ip = &mod.intern_pool;
const union_obj = mod.typeToUnion(ty).?;
const union_fields = union_obj.field_types.get(ip);
if (mod.unionTagFieldIndex(union_obj, enum_tag)) |index| {
return union_fields[index].toType();
} else {
return mod.unionLargestField(union_obj).ty;
}
const index = mod.unionTagFieldIndex(union_obj, enum_tag) orelse return null;
return union_fields[index].toType();
}
pub fn unionTagFieldIndex(ty: Type, enum_tag: Value, mod: *Module) ?u32 {

65
src/value.zig
View File

@@ -330,7 +330,7 @@ pub const Value = struct {
return mod.intern(.{ .un = .{
.ty = ty.toIntern(),
.tag = try pl.tag.intern(ty.unionTagTypeHypothetical(mod), mod),
.val = try pl.val.intern(ty.unionFieldType(pl.tag, mod), mod),
.val = try pl.val.intern(ty.unionFieldType(pl.tag, mod).?, mod),
} });
},
}
@@ -703,22 +703,20 @@ pub const Value = struct {
std.mem.writeInt(Int, buffer[0..@sizeOf(Int)], @as(Int, @intCast(int)), endian);
},
.Union => switch (ty.containerLayout(mod)) {
.Auto => return error.IllDefinedMemoryLayout,
.Auto => return error.IllDefinedMemoryLayout, // Sema is supposed to have emitted a compile error already
.Extern => {
const union_obj = mod.typeToUnion(ty).?;
const union_tag = val.unionTag(mod);
const field_type, const field_index = if (mod.unionTagFieldIndex(union_obj, union_tag)) |field_index| .{
union_obj.field_types.get(&mod.intern_pool)[field_index].toType(),
field_index,
} else f: {
const largest_field = mod.unionLargestField(union_obj);
break :f .{ largest_field.ty, largest_field.index };
};
const field_val = try val.fieldValue(mod, field_index);
const byte_count = @as(usize, @intCast(field_type.abiSize(mod)));
return writeToMemory(field_val, field_type, mod, buffer[0..byte_count]);
if (mod.unionTagFieldIndex(union_obj, union_tag)) |field_index| {
const field_type = union_obj.field_types.get(&mod.intern_pool)[field_index].toType();
const field_val = try val.fieldValue(mod, field_index);
const byte_count = @as(usize, @intCast(field_type.abiSize(mod)));
return writeToMemory(field_val, field_type, mod, buffer[0..byte_count]);
} else {
const union_size = ty.abiSize(mod);
const array_type = try mod.arrayType(.{ .len = union_size, .child = .u8_type });
return writeToMemory(val.unionValue(mod), array_type, mod, buffer[0..union_size]);
}
},
.Packed => {
const byte_count = (@as(usize, @intCast(ty.bitSize(mod))) + 7) / 8;
@@ -832,13 +830,11 @@ pub const Value = struct {
.Union => {
const union_obj = mod.typeToUnion(ty).?;
switch (union_obj.getLayout(ip)) {
.Auto => unreachable, // Sema is supposed to have emitted a compile error already
.Extern => unreachable, // Handled in non-packed writeToMemory
.Auto, .Extern => unreachable, // Handled in non-packed writeToMemory
.Packed => {
const field_index = mod.unionTagFieldIndex(union_obj, val.unionTag(mod)).?;
const field_type = union_obj.field_types.get(ip)[field_index].toType();
const field_val = try val.fieldValue(mod, field_index);
return field_val.writeToPackedMemory(field_type, mod, buffer, bit_offset);
},
}
@@ -988,17 +984,14 @@ pub const Value = struct {
.Union => switch (ty.containerLayout(mod)) {
.Auto => return error.IllDefinedMemoryLayout,
.Extern => {
const union_obj = mod.typeToUnion(ty).?;
const largest_field = mod.unionLargestField(union_obj);
const field_size: usize = @intCast(largest_field.size);
const val = try (try readFromMemory(largest_field.ty, mod, buffer[0..field_size], arena)).intern(largest_field.ty, mod);
return (try mod.intern(.{
.un = .{
.ty = ty.toIntern(),
.tag = .undef,
.val = val,
},
})).toValue();
const union_size = ty.abiSize(mod);
const array_ty = try mod.arrayType(.{ .len = union_size, .child = .u8_type });
const val = try (try readFromMemory(array_ty, mod, buffer, arena)).intern(array_ty, mod);
return (try mod.intern(.{ .un = .{
.ty = ty.toIntern(),
.tag = .none,
.val = val,
} })).toValue();
},
.Packed => {
const byte_count = (@as(usize, @intCast(ty.bitSize(mod))) + 7) / 8;
@@ -1141,17 +1134,17 @@ pub const Value = struct {
} })).toValue();
},
.Union => switch (ty.containerLayout(mod)) {
.Auto => return error.IllDefinedMemoryLayout,
.Extern => unreachable, // Handled by non-packed readFromMemory
.Auto, .Extern => unreachable, // Handled by non-packed readFromMemory
.Packed => {
const union_obj = mod.typeToUnion(ty).?;
const largest_field = mod.unionLargestField(union_obj);
const un_tag_val = try mod.enumValueFieldIndex(union_obj.enum_tag_ty.toType(), largest_field.index);
const un_val = try (try readFromPackedMemory(largest_field.ty, mod, buffer, bit_offset, arena)).intern(largest_field.ty, mod);
const union_bits: u16 = @intCast(ty.bitSize(mod));
// TODO: Remove after tests pass
assert(union_bits != 0);
const int_ty = try mod.intType(.unsigned, union_bits);
const val = (try readFromPackedMemory(int_ty, mod, buffer, bit_offset, arena)).toIntern();
return (try mod.intern(.{ .un = .{
.ty = ty.toIntern(),
.tag = un_tag_val.ip_index,
.val = un_val,
.tag = .none,
.val = val,
} })).toValue();
},
},

57
test/behavior/comptime_memory.zig
View File

@@ -455,23 +455,52 @@ test "type pun null pointer-like optional" {
}
test "reinterpret extern union" {
const U = extern union {
a: u32,
b: u64,
};
{
const U = extern union {
a: u32,
b: u8 align(8),
};
comptime var u: U = undefined;
comptime @memset(std.mem.asBytes(&u), 42);
try testing.expectEqual(@as(u64, 0x2a2a2a2a_2a2a2a2a), u.b);
comptime var u: U = undefined;
comptime @memset(std.mem.asBytes(&u), 42);
try comptime testing.expect(0x2a2a2a2a == u.a);
try comptime testing.expect(42 == u.b);
try testing.expectEqual(@as(u32, 0x2a2a2a2a), u.a);
try testing.expectEqual(42, u.b);
}
}
test "reinterpret packed union" {
const U = packed union {
a: u32,
b: u64,
};
{
const U = packed union {
a: u32,
b: u8 align(8),
};
comptime var u: U = undefined;
comptime @memset(std.mem.asBytes(&u), 42);
try testing.expectEqual(@as(u64, 0x2a2a2a2a_2a2a2a2a), u.b);
comptime var u: U = undefined;
comptime @memset(std.mem.asBytes(&u), 42);
try comptime testing.expect(0x2a2a2a2a == u.a);
try comptime testing.expect(0x2a == u.b);
try testing.expectEqual(@as(u32, 0x2a2a2a2a), u.a);
try testing.expectEqual(0x2a, u.b);
}
{
const U = packed union {
a: u7,
b: u1,
};
const S = packed struct {
lsb: U,
msb: U,
};
comptime var s: S = undefined;
comptime @memset(std.mem.asBytes(&s), 0xaa);
try comptime testing.expectEqual(@as(u7, 0x2a), s.lsb.a);
try comptime testing.expectEqual(@as(u1, 0), s.lsb.b);
try comptime testing.expectEqual(@as(u7, 0x55), s.msb.a);
try comptime testing.expectEqual(@as(u1, 1), s.msb.b);
}
}