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sema: when guessing union alignment, save the result and check if the guess was correct

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This commit is contained in:
kcbanner 2023-10-24 01:44:44 -04:00 committed by Matthew Lugg
parent 4d044ee7e0
commit fb523c6283
3 changed files with 37 additions and 6 deletions
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11
src/InternPool.zig
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@ -690,13 +690,13 @@ pub const Key = union(enum) {
/// The returned pointer expires with any addition to the `InternPool`.
pub fn size(self: @This(), ip: *InternPool) *u32 {
const size_field_index = std.meta.fieldIndex(Tag.TypeUnion, "size").?;
return @ptrCast(&ip.extra.items[self.extra_index + size_field_index]);
return &ip.extra.items[self.extra_index + size_field_index];
}
/// The returned pointer expires with any addition to the `InternPool`.
pub fn padding(self: @This(), ip: *InternPool) *u32 {
const padding_field_index = std.meta.fieldIndex(Tag.TypeUnion, "padding").?;
return @ptrCast(&ip.extra.items[self.extra_index + padding_field_index]);
return &ip.extra.items[self.extra_index + padding_field_index];
}
pub fn haveFieldTypes(self: @This(), ip: *const InternPool) bool {
@ -2965,9 +2965,9 @@ pub const Tag = enum(u8) {
/// 1. field align: Alignment for each field; declaration order
pub const TypeUnion = struct {
flags: Flags,
// Only valid after .have_layout
/// Only valid after .have_layout
size: u32,
// Only valid after .have_layout
/// Only valid after .have_layout
padding: u32,
decl: Module.Decl.Index,
namespace: Module.Namespace.Index,
@ -2983,8 +2983,9 @@ pub const Tag = enum(u8) {
status: UnionType.Status,
requires_comptime: RequiresComptime,
assumed_runtime_bits: bool,
assumed_pointer_aligned: bool,
alignment: Alignment,
_: u15 = 0,
_: u14 = 0,
};
};

19
src/Sema.zig
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@ -3200,6 +3200,7 @@ fn zirUnionDecl(
.any_aligned_fields = small.any_aligned_fields,
.requires_comptime = .unknown,
.assumed_runtime_bits = false,
.assumed_pointer_aligned = false,
.alignment = .none,
},
.decl = new_decl_index,
@ -20989,6 +20990,7 @@ fn zirReify(
.any_aligned_fields = any_aligned_fields,
.requires_comptime = .unknown,
.assumed_runtime_bits = false,
.assumed_pointer_aligned = false,
.alignment = .none,
},
.field_types = union_fields.items(.type),
@ -34940,7 +34942,10 @@ pub fn resolveUnionAlignment(
// We'll guess "pointer-aligned", if the union has an
// underaligned pointer field then some allocations
// might require explicit alignment.
return Alignment.fromByteUnits(@divExact(target.ptrBitWidth(), 8));
union_type.flagsPtr(ip).assumed_pointer_aligned = true;
const result = Alignment.fromByteUnits(@divExact(target.ptrBitWidth(), 8));
union_type.flagsPtr(ip).alignment = result;
return result;
}
try sema.resolveTypeFieldsUnion(ty, union_type);
@ -35064,6 +35069,18 @@ fn resolveUnionLayout(sema: *Sema, ty: Type) CompileError!void {
);
return sema.failWithOwnedErrorMsg(null, msg);
}
if (union_obj.flagsPtr(ip).assumed_pointer_aligned and
alignment.compareStrict(.neq, Alignment.fromByteUnits(@divExact(mod.getTarget().ptrBitWidth(), 8))))
{
const msg = try Module.ErrorMsg.create(
sema.gpa,
mod.declPtr(union_obj.decl).srcLoc(mod),
"union layout depends on being pointer aligned",
.{},
);
return sema.failWithOwnedErrorMsg(null, msg);
}
}
/// Returns `error.AnalysisFail` if any of the types (recursively) failed to

13
test/behavior/union.zig
View File

@ -1868,3 +1868,16 @@ test "reinterpret packed union inside packed struct" {
if (builtin.zig_backend == .stage2_c) return error.SkipZigTest; // TODO
try S.doTheTest();
}
test "union field is a pointer to an aligned version of itself" {
if (builtin.zig_backend == .stage2_aarch64) return error.SkipZigTest; // TODO
if (builtin.zig_backend == .stage2_spirv64) return error.SkipZigTest;
const E = union {
next: *align(1) @This(),
};
var e: E = undefined;
e = .{ .next = &e };
try expect(&e == e.next);
}