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Add union support to the C backend.

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There are some differences vs. the union encoding in the LLVM backend:
   - Tagged unions with a 0-bit payload do not become their tag type. Instead,
     they are a struct with an empty `union` as their payload field.
   - We do not order the `payload`/`tag` storage based on their alignment
This commit is contained in:
Cody Tapscott 2022-01-24 11:22:38 -07:00
parent 983dfcd3fb
commit 587a4437db
2 changed files with 141 additions and 16 deletions
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155
src/codegen/c.zig
View File

@ -589,6 +589,40 @@ pub const DeclGen = struct {
try writer.writeAll("}");
},
.Union => {
const union_obj = val.castTag(.@"union").?.data;
const target = dg.module.getTarget();
const layout = ty.unionGetLayout(target);
try writer.writeAll("(");
try dg.renderType(writer, ty);
try writer.writeAll("){");
if (ty.unionTagType()) |tag_ty| {
if (layout.tag_size != 0) {
try writer.writeAll(".tag = ");
try dg.renderValue(writer, tag_ty, union_obj.tag);
try writer.writeAll(", ");
}
try writer.writeAll(".payload = {");
}
const index = switch (ty.tag()) {
.union_tagged => ty.castTag(.union_tagged).?.data.tag_ty.enumTagFieldIndex(union_obj.tag).?,
.@"union" => ty.castTag(.@"union").?.data.tag_ty.enumTagFieldIndex(union_obj.tag).?,
else => unreachable,
};
const field_ty = ty.unionFields().values()[index].ty;
const field_name = ty.unionFields().keys()[index];
if (field_ty.hasCodeGenBits()) {
try writer.print(".{} = ", .{fmtIdent(field_name)});
try dg.renderValue(writer, field_ty, union_obj.val);
}
if (ty.unionTagType()) |_| {
try writer.writeAll("}");
}
try writer.writeAll("}");
},
.ComptimeInt => unreachable,
.ComptimeFloat => unreachable,
@ -601,7 +635,6 @@ pub const DeclGen = struct {
.BoundFn => unreachable,
.Opaque => unreachable,
.Union,
.Frame,
.AnyFrame,
.Vector,
@ -781,6 +814,65 @@ pub const DeclGen = struct {
return name;
}
fn renderUnionTypedef(dg: *DeclGen, t: Type) error{ OutOfMemory, AnalysisFail }![]const u8 {
const fqn = switch (t.tag()) {
.@"union" => try t.castTag(.@"union").?.data.getFullyQualifiedName(dg.typedefs.allocator),
.union_tagged => try t.castTag(.union_tagged).?.data.getFullyQualifiedName(dg.typedefs.allocator),
else => unreachable,
};
defer dg.typedefs.allocator.free(fqn);
const target = dg.module.getTarget();
const layout = t.unionGetLayout(target);
var buffer = std.ArrayList(u8).init(dg.typedefs.allocator);
defer buffer.deinit();
try buffer.appendSlice("typedef ");
if (t.unionTagType()) |tag_ty| {
const name: CValue = .{ .bytes = "tag" };
try buffer.appendSlice("struct {\n ");
if (layout.tag_size != 0) {
try dg.renderTypeAndName(buffer.writer(), tag_ty, name, .Mut, Value.initTag(.abi_align_default));
try buffer.appendSlice(";\n");
}
}
try buffer.appendSlice("union {\n");
{
var it = t.unionFields().iterator();
while (it.next()) |entry| {
const field_ty = entry.value_ptr.ty;
if (!field_ty.hasCodeGenBits()) continue;
const alignment = entry.value_ptr.abi_align;
const name: CValue = .{ .identifier = entry.key_ptr.* };
try buffer.append(' ');
try dg.renderTypeAndName(buffer.writer(), field_ty, name, .Mut, alignment);
try buffer.appendSlice(";\n");
}
}
try buffer.appendSlice("} ");
if (t.unionTagType()) |_| {
try buffer.appendSlice("payload;\n} ");
}
const name_start = buffer.items.len;
try buffer.writer().print("zig_U_{s};\n", .{fmtIdent(fqn)});
const rendered = buffer.toOwnedSlice();
errdefer dg.typedefs.allocator.free(rendered);
const name = rendered[name_start .. rendered.len - 2];
try dg.typedefs.ensureUnusedCapacity(1);
dg.typedefs.putAssumeCapacityNoClobber(
try t.copy(dg.typedefs_arena),
.{ .name = name, .rendered = rendered },
);
return name;
}
fn renderErrorUnionTypedef(dg: *DeclGen, t: Type) error{ OutOfMemory, AnalysisFail }![]const u8 {
const child_type = t.errorUnionPayload();
const err_set_type = t.errorUnionSet();
@ -959,6 +1051,12 @@ pub const DeclGen = struct {
return w.writeAll(name);
},
.Union => {
const name = dg.getTypedefName(t) orelse
try dg.renderUnionTypedef(t);
return w.writeAll(name);
},
.Enum => {
// For enums, we simply use the integer tag type.
var int_tag_ty_buffer: Type.Payload.Bits = undefined;
@ -967,7 +1065,6 @@ pub const DeclGen = struct {
try dg.renderType(w, int_tag_ty);
},
.Union,
.Frame,
.AnyFrame,
.Vector,
@ -2671,21 +2768,36 @@ fn airStructFieldPtrIndex(f: *Function, inst: Air.Inst.Index, index: u8) !CValue
fn structFieldPtr(f: *Function, inst: Air.Inst.Index, struct_ptr_ty: Type, struct_ptr: CValue, index: u32) !CValue {
const writer = f.object.writer();
const struct_obj = struct_ptr_ty.elemType().castTag(.@"struct").?.data;
const field_name = struct_obj.fields.keys()[index];
const field_val = struct_obj.fields.values()[index];
const addrof = if (field_val.ty.zigTypeTag() == .Array) "" else "&";
const struct_ty = struct_ptr_ty.elemType();
var field_name: []const u8 = undefined;
var field_val_ty: Type = undefined;
switch (struct_ty.tag()) {
.@"struct" => {
const fields = struct_ty.structFields();
field_name = fields.keys()[index];
field_val_ty = fields.values()[index].ty;
},
.@"union", .union_tagged => {
const fields = struct_ty.unionFields();
field_name = fields.keys()[index];
field_val_ty = fields.values()[index].ty;
},
else => unreachable,
}
const addrof = if (field_val_ty.zigTypeTag() == .Array) "" else "&";
const payload = if (struct_ty.tag() == .union_tagged) "payload." else "";
const inst_ty = f.air.typeOfIndex(inst);
const local = try f.allocLocal(inst_ty, .Const);
switch (struct_ptr) {
.local_ref => |i| {
try writer.print(" = {s}t{d}.{};\n", .{ addrof, i, fmtIdent(field_name) });
try writer.print(" = {s}t{d}.{s}{};\n", .{ addrof, i, payload, fmtIdent(field_name) });
},
else => {
try writer.print(" = {s}", .{addrof});
try f.writeCValue(writer, struct_ptr);
try writer.print("->{};\n", .{fmtIdent(field_name)});
try writer.print("->{s}{};\n", .{ payload, fmtIdent(field_name) });
},
}
return local;
@ -2700,14 +2812,18 @@ fn airStructFieldVal(f: *Function, inst: Air.Inst.Index) !CValue {
const writer = f.object.writer();
const struct_byval = try f.resolveInst(extra.struct_operand);
const struct_ty = f.air.typeOf(extra.struct_operand);
const struct_obj = struct_ty.castTag(.@"struct").?.data;
const field_name = struct_obj.fields.keys()[extra.field_index];
const field_name = switch (struct_ty.tag()) {
.@"struct" => struct_ty.structFields().keys()[extra.field_index],
.@"union", .union_tagged => struct_ty.unionFields().keys()[extra.field_index],
else => unreachable,
};
const payload = if (struct_ty.tag() == .union_tagged) "payload." else "";
const inst_ty = f.air.typeOfIndex(inst);
const local = try f.allocLocal(inst_ty, .Const);
try writer.writeAll(" = ");
try f.writeCValue(writer, struct_byval);
try writer.print(".{};\n", .{fmtIdent(field_name)});
try writer.print(".{s}{};\n", .{ payload, fmtIdent(field_name) });
return local;
}
@ -3048,9 +3164,13 @@ fn airSetUnionTag(f: *Function, inst: Air.Inst.Index) !CValue {
const new_tag = try f.resolveInst(bin_op.rhs);
const writer = f.object.writer();
try writer.writeAll("*");
const union_ty = f.air.typeOf(bin_op.lhs).childType();
const target = f.object.dg.module.getTarget();
const layout = union_ty.unionGetLayout(target);
if (layout.tag_size == 0) return CValue.none;
try f.writeCValue(writer, union_ptr);
try writer.writeAll(" = ");
try writer.writeAll("->tag = ");
try f.writeCValue(writer, new_tag);
try writer.writeAll(";\n");
@ -3064,12 +3184,17 @@ fn airGetUnionTag(f: *Function, inst: Air.Inst.Index) !CValue {
const inst_ty = f.air.typeOfIndex(inst);
const local = try f.allocLocal(inst_ty, .Const);
const ty_op = f.air.instructions.items(.data)[inst].ty_op;
const un_ty = f.air.typeOf(ty_op.operand);
const writer = f.object.writer();
const operand = try f.resolveInst(ty_op.operand);
try writer.writeAll("get_union_tag(");
const target = f.object.dg.module.getTarget();
const layout = un_ty.unionGetLayout(target);
if (layout.tag_size == 0) return CValue.none;
try writer.writeAll(" = ");
try f.writeCValue(writer, operand);
try writer.writeAll(");\n");
try writer.writeAll(".tag;\n");
return local;
}

2
test/behavior.zig
View File

@ -68,7 +68,7 @@ test {
_ = @import("behavior/cast_int.zig");
_ = @import("behavior/int128.zig");
_ = @import("behavior/union.zig");
// _ = @import("behavior/translate_c_macros.zig");
_ = @import("behavior/translate_c_macros.zig");
if (builtin.zig_backend != .stage2_c) {
// Tests that pass for stage1 and the llvm backend.