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Preserve field alignment in union pointer captures

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This commit is contained in:
John Schmidt 2024-02-04 23:04:43 +01:00
parent 919a3bae1c
commit dbcd53def0
3 changed files with 113 additions and 32 deletions
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62
src/Sema.zig
View File

@ -10992,51 +10992,67 @@ const SwitchProngAnalysis = struct {
// By-reference captures have some further restrictions which make them easier to emit
if (capture_byref) {
const first_field_alignment = union_obj.fieldAlign(ip, first_field_index);
const same_alignment = for (field_indices[1..]) |field_idx| {
const field_alignment = union_obj.fieldAlign(ip, field_idx);
if (field_alignment != first_field_alignment) break false;
} else true;
const operand_ptr_info = operand_ptr_ty.ptrInfo(mod);
const capture_ptr_ty = try sema.ptrType(.{
const capture_ptr_ty = if (same_types and same_alignment) same: {
break :same try sema.ptrType(.{
.child = capture_ty.toIntern(),
.flags = .{
// TODO: alignment!
.is_const = operand_ptr_info.flags.is_const,
.is_volatile = operand_ptr_info.flags.is_volatile,
.address_space = operand_ptr_info.flags.address_space,
.alignment = first_field_alignment,
},
});
// By-ref captures of hetereogeneous types are only allowed if each field
// pointer type is in-memory coercible to the capture pointer type.
if (!same_types) {
for (field_indices, 0..) |field_idx, i| {
} else resolve: {
// By-ref captures of hetereogeneous types are only allowed if all field
// pointer types are peer resolvable to each other.
// We need values to run PTR on, so make a bunch of undef constants.
const dummy_captures = try sema.arena.alloc(Air.Inst.Ref, case_vals.len);
for (field_indices, dummy_captures) |field_idx, *dummy| {
const field_ty = Type.fromInterned(union_obj.field_types.get(ip)[field_idx]);
const field_ptr_ty = try sema.ptrType(.{
.child = field_ty.toIntern(),
.flags = .{
// TODO: alignment!
.is_const = operand_ptr_info.flags.is_const,
.is_volatile = operand_ptr_info.flags.is_volatile,
.address_space = operand_ptr_info.flags.address_space,
.alignment = union_obj.fieldAlign(ip, field_idx),
},
});
if (.ok != try sema.coerceInMemoryAllowed(block, capture_ptr_ty, field_ptr_ty, false, sema.mod.getTarget(), .unneeded, .unneeded)) {
dummy.* = try mod.undefRef(field_ptr_ty);
}
const case_srcs = try sema.arena.alloc(?LazySrcLoc, case_vals.len);
@memset(case_srcs, .unneeded);
break :resolve sema.resolvePeerTypes(block, .unneeded, dummy_captures, .{ .override = case_srcs }) catch |err| switch (err) {
error.NeededSourceLocation => {
// This must be a multi-prong so this must be a `multi_capture` src
const multi_idx = raw_capture_src.multi_capture;
const src_decl_ptr = sema.mod.declPtr(block.src_decl);
const capture_src = raw_capture_src.resolve(mod, src_decl_ptr, switch_node_offset, .none);
for (case_srcs, 0..) |*case_src, i| {
const raw_case_src: Module.SwitchProngSrc = .{ .multi = .{ .prong = multi_idx, .item = @intCast(i) } };
const case_src = raw_case_src.resolve(mod, src_decl_ptr, switch_node_offset, .none);
const msg = msg: {
const msg = try sema.errMsg(block, capture_src, "capture group with incompatible types", .{});
errdefer msg.destroy(sema.gpa);
try sema.errNote(block, case_src, msg, "pointer type child '{}' cannot cast into resolved pointer type child '{}'", .{
field_ty.fmt(sema.mod),
capture_ty.fmt(sema.mod),
});
case_src.* = raw_case_src.resolve(mod, src_decl_ptr, switch_node_offset, .none);
}
const capture_src = raw_capture_src.resolve(mod, src_decl_ptr, switch_node_offset, .none);
_ = sema.resolvePeerTypes(block, capture_src, dummy_captures, .{ .override = case_srcs }) catch |err1| switch (err1) {
error.AnalysisFail => {
const msg = sema.err orelse return error.AnalysisFail;
try sema.errNote(block, capture_src, msg, "this coercion is only possible when capturing by value", .{});
break :msg msg;
try sema.reparentOwnedErrorMsg(block, capture_src, msg, "capture group with incompatible types", .{});
return error.AnalysisFail;
},
else => |e| return e,
};
unreachable;
},
else => |e| return e,
};
};
return sema.failWithOwnedErrorMsg(block, msg);
}
}
}
if (try sema.resolveDefinedValue(block, operand_src, spa.operand_ptr)) |op_ptr_val| {
if (op_ptr_val.isUndef(mod)) return mod.undefRef(capture_ptr_ty);

63
test/behavior/switch.zig
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@ -574,6 +574,69 @@ test "switch prongs with cases with identical payload types" {
try comptime S.doTheTest();
}
test "switch prong pointer capture alignment" {
const U = union(enum) {
a: u8 align(8),
b: u8 align(4),
c: u8,
};
const S = struct {
fn doTheTest() !void {
const u = U{ .a = 1 };
switch (u) {
.a => |*a| try expectEqual(*align(8) const u8, @TypeOf(a)),
.b, .c => |*p| {
_ = p;
@panic("fail");
},
}
switch (u) {
.a, .b => |*p| try expectEqual(*align(4) const u8, @TypeOf(p)),
.c => |*p| {
_ = p;
@panic("fail");
},
}
switch (u) {
.a, .c => |*p| try expectEqual(*const u8, @TypeOf(p)),
.b => |*p| {
_ = p;
@panic("fail");
},
}
}
fn doTheTest2() !void {
const un1 = U{ .b = 1 };
switch (un1) {
.b => |*a| try expectEqual(*align(4) const u8, @TypeOf(a)),
.a, .c => |*p| {
_ = p;
@panic("fail");
},
}
const un2 = U{ .c = 1 };
switch (un2) {
.c => |*a| try expectEqual(*const u8, @TypeOf(a)),
.a, .b => |*p| {
_ = p;
@panic("fail");
},
}
}
};
try S.doTheTest();
try comptime S.doTheTest();
try S.doTheTest2();
try comptime S.doTheTest2();
}
test "switch on pointer type" {
if (builtin.zig_backend == .stage2_aarch64) return error.SkipZigTest; // TODO
if (builtin.zig_backend == .stage2_sparc64) return error.SkipZigTest; // TODO

4
test/cases/compile_errors/switch_capture_incompatible_types.zig
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@ -23,5 +23,7 @@ export fn g() void {
// :5:10: note: type 'u32' here
// :5:14: note: type '*u8' here
// :13:20: error: capture group with incompatible types
// :13:14: note: pointer type child 'u32' cannot cast into resolved pointer type child 'u64'
// :13:20: note: incompatible types: '*u64' and '*u32'
// :13:10: note: type '*u64' here
// :13:14: note: type '*u32' here
// :13:20: note: this coercion is only possible when capturing by value