commit 2b8feabb8f2b3a3c96d2d8e74393e0c8dfa17390 (tree)
parent 6402e119e8d21403cbafc4a6c8ca353b894592ba
Author: Matthew Lugg <mlugg@mlugg.co.uk>
Date: Fri, 13 Feb 2026 11:48:56 +0000
llvm: some more improvements to debug info
Most importantly, adds support for `DW_TAG_typedef` to `llvm.Builder`,
and uses it to define error sets and optional pointers/errors.
Also deletes some random dead code I found.
Diffstat:
2 files changed, 142 insertions(+), 173 deletions(-)
diff --git a/lib/std/zig/llvm/Builder.zig b/lib/std/zig/llvm/Builder.zig
@@ -8021,6 +8021,7 @@ pub const Metadata = packed struct(u32) {
composite_vector_type,
derived_pointer_type,
derived_member_type,
+ derived_typedef_type,
subroutine_type,
enumerator_unsigned,
enumerator_signed_positive,
@@ -8064,6 +8065,7 @@ pub const Metadata = packed struct(u32) {
.composite_vector_type,
.derived_pointer_type,
.derived_member_type,
+ .derived_typedef_type,
.subroutine_type,
.enumerator_unsigned,
.enumerator_signed_positive,
@@ -10463,15 +10465,18 @@ pub fn print(self: *Builder, w: *Writer) (Writer.Error || Allocator.Error)!void
},
.derived_pointer_type,
.derived_member_type,
+ .derived_typedef_type,
=> |kind| {
const extra = self.metadataExtraData(Metadata.DerivedType, metadata_item.data);
try metadata_formatter.specialized(.@"!", .DIDerivedType, .{
.tag = @as(enum {
DW_TAG_pointer_type,
DW_TAG_member,
+ DW_TAG_typedef,
}, switch (kind) {
.derived_pointer_type => .DW_TAG_pointer_type,
.derived_member_type => .DW_TAG_member,
+ .derived_typedef_type => .DW_TAG_typedef,
else => unreachable,
}),
.name = extra.name,
@@ -12360,6 +12365,30 @@ pub fn debugMemberType(
);
}
+pub fn debugTypedefType(
+ self: *Builder,
+ name: ?Metadata.String,
+ file: ?Metadata,
+ scope: ?Metadata,
+ line: u32,
+ underlying_type: ?Metadata,
+ size_in_bits: u64,
+ align_in_bits: u64,
+ offset_in_bits: u64,
+) Allocator.Error!Metadata {
+ try self.ensureUnusedMetadataCapacity(1, Metadata.DerivedType, 0);
+ return self.debugTypedefTypeAssumeCapacity(
+ name,
+ file,
+ scope,
+ line,
+ underlying_type,
+ size_in_bits,
+ align_in_bits,
+ offset_in_bits,
+ );
+}
+
pub fn debugSubroutineType(self: *Builder, types_tuple: ?Metadata) Allocator.Error!Metadata {
try self.ensureUnusedMetadataCapacity(1, Metadata.SubroutineType, 0);
return self.debugSubroutineTypeAssumeCapacity(types_tuple);
@@ -12875,6 +12904,33 @@ fn debugMemberTypeAssumeCapacity(
});
}
+fn debugTypedefTypeAssumeCapacity(
+ self: *Builder,
+ name: ?Metadata.String,
+ file: ?Metadata,
+ scope: ?Metadata,
+ line: u32,
+ underlying_type: ?Metadata,
+ size_in_bits: u64,
+ align_in_bits: u64,
+ offset_in_bits: u64,
+) Metadata {
+ assert(!self.strip);
+ return self.metadataSimpleAssumeCapacity(.derived_typedef_type, Metadata.DerivedType{
+ .name = .wrap(name),
+ .file = .wrap(file),
+ .scope = .wrap(scope),
+ .line = line,
+ .underlying_type = .wrap(underlying_type),
+ .size_in_bits_lo = @truncate(size_in_bits),
+ .size_in_bits_hi = @truncate(size_in_bits >> 32),
+ .align_in_bits_lo = @truncate(align_in_bits),
+ .align_in_bits_hi = @truncate(align_in_bits >> 32),
+ .offset_in_bits_lo = @truncate(offset_in_bits),
+ .offset_in_bits_hi = @truncate(offset_in_bits >> 32),
+ });
+}
+
fn debugSubroutineTypeAssumeCapacity(self: *Builder, types_tuple: ?Metadata) Metadata {
assert(!self.strip);
return self.metadataSimpleAssumeCapacity(.subroutine_type, Metadata.SubroutineType{
@@ -14223,12 +14279,14 @@ pub fn toBitcode(self: *Builder, allocator: Allocator, producer: Producer) bitco
},
.derived_pointer_type,
.derived_member_type,
+ .derived_typedef_type,
=> |kind| {
const extra = self.metadataExtraData(Metadata.DerivedType, data);
try metadata_block.writeAbbrevAdapted(MetadataBlock.DerivedType{
.tag = switch (kind) {
.derived_pointer_type => DW.TAG.pointer_type,
.derived_member_type => DW.TAG.member,
+ .derived_typedef_type => DW.TAG.typedef,
else => unreachable,
},
.name = extra.name,
diff --git a/src/codegen/llvm.zig b/src/codegen/llvm.zig
@@ -1914,6 +1914,15 @@ pub const Object = struct {
const name = try o.builder.metadataStringFmt("{f}", .{ty.fmt(pt)});
+ // lldb cannot handle non-byte-sized types, so in the logic below, bit sizes are padded up.
+ // For instance, `bool` is considered to be 8 bits, and `u60` is considered to be 64 bits.
+
+ // I tried using variants (DW_TAG_variant_part + DW_TAG_variant) to encode error unions,
+ // tagged unions, etc; this would have told debuggers which field was active, which could
+ // improve UX significantly. GDB handles this perfectly fine, but unfortunately, LLDB has no
+ // handling for variants at all, and will never print fields in them, so I opted not to use
+ // them for now.
+
switch (ty.zigTypeTag(zcu)) {
.void,
.noreturn,
@@ -1925,23 +1934,19 @@ pub const Object = struct {
.enum_literal,
=> return o.builder.debugSignedType(name, 0),
+ .float => return o.builder.debugFloatType(name, ty.floatBits(target)),
+
+ .bool => return o.builder.debugBoolType(name, 8),
+
.int => {
const info = ty.intInfo(zcu);
- const bits = ty.abiSize(zcu) * 8; // lldb cannot handle non-byte sized types
+ const bits = ty.abiSize(zcu) * 8;
return switch (info.signedness) {
.signed => try o.builder.debugSignedType(name, bits),
.unsigned => try o.builder.debugUnsignedType(name, bits),
};
},
- .float => {
- return o.builder.debugFloatType(name, ty.floatBits(target));
- },
- .bool => {
- return o.builder.debugBoolType(
- name,
- 8, // lldb cannot handle non-byte sized types
- );
- },
+
.pointer => {
const ptr_size = Type.ptrAbiSize(zcu.getTarget());
const ptr_align = Type.ptrAbiAlignment(zcu.getTarget());
@@ -1949,20 +1954,20 @@ pub const Object = struct {
if (ty.isSlice(zcu)) {
const debug_ptr_type = try o.builder.debugMemberType(
try o.builder.metadataString("ptr"),
- null, // File
+ null, // file
ty_fwd_ref,
- 0, // Line
+ 0, // line
try o.getDebugType(pt, ty.slicePtrFieldType(zcu)),
ptr_size * 8,
ptr_align.toByteUnits().? * 8,
- 0, // Offset
+ 0, // offset
);
const debug_len_type = try o.builder.debugMemberType(
try o.builder.metadataString("len"),
- null, // File
+ null, // file
ty_fwd_ref,
- 0, // Line
+ 0, // line
try o.getDebugType(pt, .usize),
ptr_size * 8,
ptr_align.toByteUnits().? * 8,
@@ -1971,10 +1976,10 @@ pub const Object = struct {
return o.builder.debugStructType(
name,
- null, // File
- o.debug_compile_unit.unwrap().?, // Scope
- 0, // Line
- null, // Underlying type
+ null, // file
+ o.debug_compile_unit.unwrap().?, // scope
+ 0, // line
+ null, // underlying type
ptr_size * 2 * 8,
ptr_align.toByteUnits().? * 8,
try o.builder.metadataTuple(&.{
@@ -1986,36 +1991,34 @@ pub const Object = struct {
return o.builder.debugPointerType(
name,
- null, // File
- null, // Scope
- 0, // Line
+ null, // file
+ o.debug_compile_unit.unwrap().?, // scope
+ 0, // line
try o.getDebugType(pt, ty.childType(zcu)),
ptr_size * 8,
ptr_align.toByteUnits().? * 8,
- 0, // Offset
- );
- },
- .array => {
- return o.builder.debugArrayType(
- null, // Name
- null, // File
- null, // Scope
- 0, // Line
- try o.getDebugType(pt, ty.childType(zcu)),
- ty.abiSize(zcu) * 8,
- (ty.abiAlignment(zcu).toByteUnits() orelse 0) * 8,
- try o.builder.metadataTuple(&.{
- try o.builder.debugSubrange(
- try o.builder.metadataConstant(try o.builder.intConst(.i64, 0)),
- try o.builder.metadataConstant(try o.builder.intConst(.i64, ty.arrayLen(zcu))),
- ),
- }),
+ 0, // offset
);
},
+ .array => return o.builder.debugArrayType(
+ name,
+ null, // file
+ o.debug_compile_unit.unwrap().?, // scope
+ 0, // line
+ try o.getDebugType(pt, ty.childType(zcu)),
+ ty.abiSize(zcu) * 8,
+ ty.abiAlignment(zcu).toByteUnits().? * 8,
+ try o.builder.metadataTuple(&.{
+ try o.builder.debugSubrange(
+ try o.builder.metadataConstant(try o.builder.intConst(.i64, 0)),
+ try o.builder.metadataConstant(try o.builder.intConst(.i64, ty.arrayLen(zcu))),
+ ),
+ }),
+ ),
.vector => {
const elem_ty = ty.childType(zcu);
// Vector elements cannot be padded since that would make
- // @bitSizOf(elem) * len > @bitSizOf(vec).
+ // @bitSizeOf(elem) * len > @bitSizOf(vec).
// Neither gdb nor lldb seem to be able to display non-byte sized
// vectors properly.
const debug_elem_type = switch (elem_ty.zigTypeTag(zcu)) {
@@ -2027,18 +2030,19 @@ pub const Object = struct {
};
},
.bool => try o.builder.debugBoolType(try o.builder.metadataString("bool"), 1),
+ // We don't pad pointers or floats, so we can lower those normally.
.pointer, .optional, .float => try o.getDebugType(pt, elem_ty),
else => unreachable,
};
return o.builder.debugVectorType(
- null, // Name
- null, // File
- null, // Scope
- 0, // Line
+ name,
+ null, // file
+ o.debug_compile_unit.unwrap().?, // scope
+ 0, // line
debug_elem_type,
ty.abiSize(zcu) * 8,
- (ty.abiAlignment(zcu).toByteUnits() orelse 0) * 8,
+ ty.abiAlignment(zcu).toByteUnits().? * 8,
try o.builder.metadataTuple(&.{
try o.builder.debugSubrange(
try o.builder.metadataConstant(try o.builder.intConst(.i64, 0)),
@@ -2050,26 +2054,15 @@ pub const Object = struct {
.optional => {
const payload_ty = ty.optionalChild(zcu);
if (ty.optionalReprIsPayload(zcu)) {
- // MLUGG TODO: these should use DW_TAG_typedef instead, but std.zig.llvm.Builder currently lacks support for those.
- const payload_member = try o.builder.debugMemberType(
- try o.builder.metadataString("payload"),
- null, // file
- ty_fwd_ref,
- 0, // line
- try o.getDebugType(pt, .anyerror),
- ty.abiSize(zcu) * 8,
- ty.abiAlignment(zcu).toByteUnits().? * 8,
- 0, // offset
- );
- return o.builder.debugStructType(
+ return o.builder.debugTypedefType(
name,
null, // file
o.debug_compile_unit.unwrap().?, // scope
0, // line
- null, // underlying type
+ try o.getDebugType(pt, payload_ty),
ty.abiSize(zcu) * 8,
ty.abiAlignment(zcu).toByteUnits().? * 8,
- try o.builder.metadataTuple(&.{payload_member}),
+ 0, // offset
);
}
@@ -2083,7 +2076,7 @@ pub const Object = struct {
const debug_payload_type = try o.builder.debugMemberType(
try o.builder.metadataString("payload"),
null, // file
- ty_fwd_ref,
+ ty_fwd_ref, // scope
0, // line
try o.getDebugType(pt, payload_ty),
payload_size * 8,
@@ -2104,12 +2097,12 @@ pub const Object = struct {
return o.builder.debugStructType(
name,
- null, // File
- o.debug_compile_unit.unwrap().?, // Scope
- 0, // Line
- null, // Underlying type
+ null, // file
+ o.debug_compile_unit.unwrap().?, // scope
+ 0, // line
+ null, // underlying type
ty.abiSize(zcu) * 8,
- (ty.abiAlignment(zcu).toByteUnits() orelse 0) * 8,
+ ty.abiAlignment(zcu).toByteUnits().? * 8,
try o.builder.metadataTuple(&.{
debug_payload_type,
debug_some_type,
@@ -2125,30 +2118,29 @@ pub const Object = struct {
const payload_size = payload_ty.abiSize(zcu);
const payload_align = payload_ty.abiAlignment(zcu);
- const error_index: u1, const payload_index: u1, const error_offset: u64, const payload_offset: u64 = fields: {
+ const error_offset: u64, const payload_offset: u64 = offsets: {
if (error_align.compare(.gt, payload_align)) {
- break :fields .{ 0, 1, 0, payload_align.forward(error_size) };
+ break :offsets .{ 0, payload_align.forward(error_size) };
} else {
- break :fields .{ 1, 0, error_align.forward(payload_size), 0 };
+ break :offsets .{ error_align.forward(payload_size), 0 };
}
};
- var fields: [2]Builder.Metadata = undefined;
- fields[error_index] = try o.builder.debugMemberType(
+ const error_field = try o.builder.debugMemberType(
try o.builder.metadataString("error"),
- null, // File
+ null, // file
ty_fwd_ref,
- 0, // Line
+ 0, // line
try o.getDebugType(pt, error_ty),
error_size * 8,
error_align.toByteUnits().? * 8,
error_offset * 8,
);
- fields[payload_index] = try o.builder.debugMemberType(
+ const payload_field = try o.builder.debugMemberType(
try o.builder.metadataString("payload"),
- null, // File
- ty_fwd_ref,
- 0, // Line
+ null, // file
+ ty_fwd_ref, // scope
+ 0, // line
try o.getDebugType(pt, payload_ty),
payload_size * 8,
payload_align.toByteUnits().? * 8,
@@ -2163,32 +2155,21 @@ pub const Object = struct {
null, // Underlying type
ty.abiSize(zcu) * 8,
ty.abiAlignment(zcu).toByteUnits().? * 8,
- try o.builder.metadataTuple(&fields),
+ try o.builder.metadataTuple(&.{ error_field, payload_field }),
);
},
.error_set => {
assert(ty.toIntern() != .anyerror_type); // handled specially in `updateConst`; will be populated by `emit` instead
// Error sets are just named wrappers around `anyerror`.
- // MLUGG TODO: these should use DW_TAG_typedef instead, but std.zig.llvm.Builder currently lacks support for those.
- const anyerror_member = try o.builder.debugMemberType(
- try o.builder.metadataString("error"),
- null, // file
- ty_fwd_ref,
- 0, // line
- try o.getDebugType(pt, .anyerror),
- ty.abiSize(zcu) * 8,
- ty.abiAlignment(zcu).toByteUnits().? * 8,
- 0, // offset
- );
- return o.builder.debugStructType(
+ return o.builder.debugTypedefType(
name,
null, // file
o.debug_compile_unit.unwrap().?, // scope
0, // line
- null, // underlying type
+ try o.getDebugType(pt, .anyerror),
ty.abiSize(zcu) * 8,
ty.abiAlignment(zcu).toByteUnits().? * 8,
- try o.builder.metadataTuple(&.{anyerror_member}),
+ 0, // offset
);
},
.@"fn" => {
@@ -2570,14 +2551,22 @@ pub const Object = struct {
const error_set_bits = zcu.errorSetBits();
const error_names = ip.global_error_set.getNamesFromMainThread();
- const enumerators = try gpa.alloc(Builder.Metadata, error_names.len);
+ const enumerators = try gpa.alloc(Builder.Metadata, error_names.len + 1);
defer gpa.free(enumerators);
- for (enumerators, error_names, 1..) |*out, error_name, error_value| {
+ // The value 0 means "no error" in optionals and error unions.
+ enumerators[0] = try o.builder.debugEnumerator(
+ try o.builder.metadataString("null"),
+ true, // unsigned,
+ error_set_bits,
+ .{ .limbs = &.{0}, .positive = true }, // zero
+ );
+
+ for (enumerators[1..], error_names, 1..) |*out, error_name, error_value| {
var space: Value.BigIntSpace = undefined;
var bigint: std.math.big.int.Mutable = .init(&space.limbs, error_value);
out.* = try o.builder.debugEnumerator(
- try o.builder.metadataString(error_name.toSlice(ip)),
+ try o.builder.metadataStringFmt("error.{f}", .{error_name.fmtId(ip)}),
true, // unsigned
error_set_bits,
bigint.toConst(),
@@ -3452,84 +3441,6 @@ pub const Object = struct {
);
}
- fn lowerValueToInt(o: *Object, pt: Zcu.PerThread, llvm_int_ty: Builder.Type, arg_val: InternPool.Index) Error!Builder.Constant {
- const zcu = pt.zcu;
- const ip = &zcu.intern_pool;
- const target = zcu.getTarget();
-
- const val = Value.fromInterned(arg_val);
- const val_key = ip.indexToKey(val.toIntern());
-
- if (val.isUndef(zcu)) return o.builder.undefConst(llvm_int_ty);
-
- const ty = Type.fromInterned(val_key.typeOf());
- switch (val_key) {
- .@"extern" => |@"extern"| {
- const function_index = try o.resolveLlvmFunction(pt, @"extern".owner_nav);
- const ptr = function_index.ptrConst(&o.builder).global.toConst();
- return o.builder.convConst(ptr, llvm_int_ty);
- },
- .func => |func| {
- const function_index = try o.resolveLlvmFunction(pt, func.owner_nav);
- const ptr = function_index.ptrConst(&o.builder).global.toConst();
- return o.builder.convConst(ptr, llvm_int_ty);
- },
- .ptr => return o.builder.convConst(try o.lowerPtr(pt, arg_val, 0), llvm_int_ty),
- .aggregate => switch (ip.indexToKey(ty.toIntern())) {
- .struct_type, .vector_type => {},
- else => unreachable,
- },
- .un => |un| {
- const layout = ty.unionGetLayout(zcu);
- if (layout.payload_size == 0) return o.lowerValue(pt, un.tag);
-
- const union_obj = zcu.typeToUnion(ty).?;
- const container_layout = union_obj.layout;
-
- assert(container_layout == .@"packed");
-
- var need_unnamed = false;
- if (un.tag == .none) {
- assert(layout.tag_size == 0);
- const union_val = try o.lowerValueToInt(pt, llvm_int_ty, un.val);
-
- need_unnamed = true;
- return union_val;
- }
- const field_index = zcu.unionTagFieldIndex(union_obj, Value.fromInterned(un.tag)).?;
- const field_ty = Type.fromInterned(union_obj.field_types.get(ip)[field_index]);
- if (!field_ty.hasRuntimeBits(zcu)) return o.builder.intConst(llvm_int_ty, 0);
- return o.lowerValueToInt(pt, llvm_int_ty, un.val);
- },
- .simple_value => |simple_value| switch (simple_value) {
- .false, .true => {},
- else => unreachable,
- },
- .int,
- .float,
- .enum_tag,
- => {},
- .opt => {}, // pointer like optional expected
- else => unreachable,
- }
- var stack = std.heap.stackFallback(32, o.gpa);
- const allocator = stack.get();
-
- const bits: usize = @intCast(ty.bitSize(zcu));
-
- const buffer = try allocator.alloc(u8, (bits + 7) / 8);
- defer allocator.free(buffer);
- const limbs = try allocator.alloc(std.math.big.Limb, std.math.big.int.calcTwosCompLimbCount(bits));
- defer allocator.free(limbs);
-
- val.writeToPackedMemory(pt, buffer, 0) catch unreachable;
-
- var big: std.math.big.int.Mutable = .init(limbs, 0);
- big.readTwosComplement(buffer, bits, target.cpu.arch.endian(), .unsigned);
-
- return o.builder.bigIntConst(llvm_int_ty, big.toConst());
- }
-
fn lowerValue(o: *Object, pt: Zcu.PerThread, arg_val: InternPool.Index) Error!Builder.Constant {
const zcu = pt.zcu;
const ip = &zcu.intern_pool;
