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revert "compiler: packed structs cache bit offsets"

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This is mostly a revert of a7088fd9a3edb037f0f51bb402a3c557334634f3.
Measurement revealed the commit actually regressed performance.
This commit is contained in:
Andrew Kelley 2023-09-24 14:37:36 -07:00
parent a7088fd9a3
commit c08c0fc6ed
9 changed files with 52 additions and 67 deletions
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52
src/InternPool.zig
View File

@ -105,25 +105,6 @@ pub const MapIndex = enum(u32) {
}
};
pub const OptionalInt = enum(u32) {
none = std.math.maxInt(u32),
_,
pub fn init(x: u32) @This() {
const result: @This() = @enumFromInt(x);
assert(result != .none);
return result;
}
pub fn initOptional(opt_x: ?u32) @This() {
return @This().init(opt_x orelse return .none);
}
pub fn unwrap(this: @This()) ?u32 {
return if (this == .none) null else @intFromEnum(this);
}
};
pub const RuntimeIndex = enum(u32) {
zero = 0,
comptime_field_ptr = std.math.maxInt(u32),
@ -396,8 +377,6 @@ pub const Key = union(enum) {
field_aligns: Alignment.Slice,
runtime_order: RuntimeOrder.Slice,
comptime_bits: ComptimeBits,
/// In the case of packed structs these are bit offsets; in the case of
/// non-packed structs these are byte offsets.
offsets: Offsets,
names_map: OptionalMapIndex,
@ -496,15 +475,6 @@ pub const Key = union(enum) {
return s.field_names.get(ip)[i].toOptional();
}
/// Asserts it is a packed struct.
/// Asserts the layout is resolved.
pub fn fieldBitOffset(s: @This(), ip: *InternPool, i: usize) u32 {
assert(s.layout == .Packed);
assert(s.haveLayout(ip));
const result: OptionalInt = @enumFromInt(s.offsets.get(ip)[i]);
return result.unwrap().?;
}
pub fn fieldIsComptime(s: @This(), ip: *const InternPool, i: usize) bool {
return s.comptime_bits.getBit(ip, i);
}
@ -623,11 +593,7 @@ pub const Key = union(enum) {
pub fn haveLayout(s: @This(), ip: *InternPool) bool {
return switch (s.layout) {
.Packed => {
if (s.offsets.len == 0) return true;
const first_offset: OptionalInt = @enumFromInt(ip.extra.items[s.offsets.start]);
return first_offset != .none;
},
.Packed => s.backingIntType(ip).* != .none,
.Auto, .Extern => s.flagsPtr(ip).layout_resolved,
};
}
@ -2970,8 +2936,7 @@ pub const Tag = enum(u8) {
/// Trailing:
/// 0. type: Index for each fields_len
/// 1. name: NullTerminatedString for each fields_len
/// 2. bit_offset: OptionalInt for each fields_len // none until layout resolved
/// 3. init: Index for each fields_len // if tag is type_struct_packed_inits
/// 2. init: Index for each fields_len // if tag is type_struct_packed_inits
pub const TypeStructPacked = struct {
decl: Module.Decl.Index,
zir_index: Zir.Inst.Index,
@ -4229,12 +4194,8 @@ fn extraPackedStructType(ip: *const InternPool, extra_index: u32, inits: bool) K
.start = type_struct_packed.end + fields_len,
.len = fields_len,
},
.offsets = .{
.start = type_struct_packed.end + fields_len * 2,
.len = fields_len,
},
.field_inits = if (inits) .{
.start = type_struct_packed.end + fields_len * 3,
.start = type_struct_packed.end + fields_len * 2,
.len = fields_len,
} else .{
.start = 0,
@ -4243,6 +4204,7 @@ fn extraPackedStructType(ip: *const InternPool, extra_index: u32, inits: bool) K
.field_aligns = .{ .start = 0, .len = 0 },
.runtime_order = .{ .start = 0, .len = 0 },
.comptime_bits = .{ .start = 0, .len = 0 },
.offsets = .{ .start = 0, .len = 0 },
.names_map = type_struct_packed.data.names_map.toOptional(),
};
}
@ -5317,7 +5279,6 @@ pub fn getStructType(
try ip.extra.ensureUnusedCapacity(gpa, @typeInfo(Tag.TypeStructPacked).Struct.fields.len +
ini.fields_len + // types
ini.fields_len + // names
ini.fields_len + // offsets
ini.fields_len); // inits
try ip.items.append(gpa, .{
.tag = if (ini.any_default_inits) .type_struct_packed_inits else .type_struct_packed,
@ -5332,7 +5293,6 @@ pub fn getStructType(
});
ip.extra.appendNTimesAssumeCapacity(@intFromEnum(Index.none), ini.fields_len);
ip.extra.appendNTimesAssumeCapacity(@intFromEnum(OptionalNullTerminatedString.none), ini.fields_len);
ip.extra.appendNTimesAssumeCapacity(@intFromEnum(OptionalInt.none), ini.fields_len);
if (ini.any_default_inits) {
ip.extra.appendNTimesAssumeCapacity(@intFromEnum(Index.none), ini.fields_len);
}
@ -7153,12 +7113,12 @@ fn dumpStatsFallible(ip: *const InternPool, arena: Allocator) anyerror!void {
.type_struct_packed => b: {
const info = ip.extraData(Tag.TypeStructPacked, data);
break :b @sizeOf(u32) * (@typeInfo(Tag.TypeStructPacked).Struct.fields.len +
info.fields_len + info.fields_len + info.fields_len);
info.fields_len + info.fields_len);
},
.type_struct_packed_inits => b: {
const info = ip.extraData(Tag.TypeStructPacked, data);
break :b @sizeOf(u32) * (@typeInfo(Tag.TypeStructPacked).Struct.fields.len +
info.fields_len + info.fields_len + info.fields_len + info.fields_len);
info.fields_len + info.fields_len + info.fields_len);
},
.type_tuple_anon => b: {
const info = ip.extraData(TypeStructAnon, data);

23
src/Module.zig
View File

@ -6649,3 +6649,26 @@ pub fn structFieldAlignmentExtern(mod: *Module, field_ty: Type) Alignment {
return ty_abi_align;
}
/// https://github.com/ziglang/zig/issues/17178 explored storing these bit offsets
/// into the packed struct InternPool data rather than computing this on the
/// fly, however it was found to perform worse when measured on real world
/// projects.
pub fn structPackedFieldBitOffset(
mod: *Module,
struct_type: InternPool.Key.StructType,
field_index: u32,
) u16 {
const ip = &mod.intern_pool;
assert(struct_type.layout == .Packed);
assert(struct_type.haveLayout(ip));
var bit_sum: u64 = 0;
for (0..struct_type.field_types.len) |i| {
if (i == field_index) {
return @intCast(bit_sum);
}
const field_ty = struct_type.field_types.get(ip)[i].toType();
bit_sum += field_ty.bitSize(mod);
}
unreachable; // index out of bounds
}

2
src/Sema.zig
View File

@ -21343,7 +21343,6 @@ fn reifyStruct(
var fields_bit_sum: u64 = 0;
for (0..struct_type.field_types.len) |i| {
struct_type.offsets.get(ip)[i] = @intCast(fields_bit_sum);
const field_ty = struct_type.field_types.get(ip)[i].toType();
fields_bit_sum += field_ty.bitSize(mod);
}
@ -34774,7 +34773,6 @@ fn semaBackingIntType(mod: *Module, struct_type: InternPool.Key.StructType) Comp
var accumulator: u64 = 0;
for (0..struct_type.field_types.len) |i| {
const field_ty = struct_type.field_types.get(ip)[i].toType();
struct_type.offsets.get(ip)[i] = @intCast(accumulator);
accumulator += try field_ty.bitSizeAdvanced(mod, &sema);
}
break :blk accumulator;

2
src/arch/wasm/CodeGen.zig
View File

@ -3779,7 +3779,7 @@ fn airStructFieldVal(func: *CodeGen, inst: Air.Inst.Index) InnerError!void {
.Packed => switch (struct_ty.zigTypeTag(mod)) {
.Struct => result: {
const packed_struct = mod.typeToPackedStruct(struct_ty).?;
const offset = packed_struct.fieldBitOffset(ip, field_index);
const offset = mod.structPackedFieldBitOffset(packed_struct, field_index);
const backing_ty = packed_struct.backingIntType(ip).toType();
const wasm_bits = toWasmBits(backing_ty.intInfo(mod).bits) orelse {
return func.fail("TODO: airStructFieldVal for packed structs larger than 128 bits", .{});

6
src/arch/x86_64/CodeGen.zig
View File

@ -5593,7 +5593,6 @@ fn fieldPtr(self: *Self, inst: Air.Inst.Index, operand: Air.Inst.Ref, index: u32
fn airStructFieldVal(self: *Self, inst: Air.Inst.Index) !void {
const mod = self.bin_file.options.module.?;
const ip = &mod.intern_pool;
const ty_pl = self.air.instructions.items(.data)[inst].ty_pl;
const extra = self.air.extraData(Air.StructField, ty_pl.payload).data;
const result: MCValue = result: {
@ -5611,7 +5610,7 @@ fn airStructFieldVal(self: *Self, inst: Air.Inst.Index) !void {
const field_off: u32 = switch (container_ty.containerLayout(mod)) {
.Auto, .Extern => @intCast(container_ty.structFieldOffset(index, mod) * 8),
.Packed => if (mod.typeToStruct(container_ty)) |struct_type|
struct_type.fieldBitOffset(ip, index)
mod.structPackedFieldBitOffset(struct_type, index)
else
0,
};
@ -11411,7 +11410,6 @@ fn airReduce(self: *Self, inst: Air.Inst.Index) !void {
fn airAggregateInit(self: *Self, inst: Air.Inst.Index) !void {
const mod = self.bin_file.options.module.?;
const ip = &mod.intern_pool;
const result_ty = self.typeOfIndex(inst);
const len: usize = @intCast(result_ty.arrayLen(mod));
const ty_pl = self.air.instructions.items(.data)[inst].ty_pl;
@ -11442,7 +11440,7 @@ fn airAggregateInit(self: *Self, inst: Air.Inst.Index) !void {
}
const elem_abi_size: u32 = @intCast(elem_ty.abiSize(mod));
const elem_abi_bits = elem_abi_size * 8;
const elem_off = struct_type.fieldBitOffset(ip, elem_i);
const elem_off = mod.structPackedFieldBitOffset(struct_type, elem_i);
const elem_byte_off: i32 = @intCast(elem_off / elem_abi_bits * elem_abi_size);
const elem_bit_off = elem_off % elem_abi_bits;
const elem_mcv = try self.resolveInst(elem);

17
src/codegen.zig
View File

@ -630,8 +630,7 @@ fn lowerParentPtr(
reloc_info: RelocInfo,
) CodeGenError!Result {
const mod = bin_file.options.module.?;
const ip = &mod.intern_pool;
const ptr = ip.indexToKey(parent_ptr).ptr;
const ptr = mod.intern_pool.indexToKey(parent_ptr).ptr;
assert(ptr.len == .none);
return switch (ptr.addr) {
.decl, .mut_decl => try lowerDeclRef(
@ -657,7 +656,7 @@ fn lowerParentPtr(
code,
debug_output,
reloc_info.offset(@as(u32, @intCast(errUnionPayloadOffset(
ip.typeOf(eu_payload).toType(),
mod.intern_pool.typeOf(eu_payload).toType(),
mod,
)))),
),
@ -676,17 +675,17 @@ fn lowerParentPtr(
code,
debug_output,
reloc_info.offset(@as(u32, @intCast(elem.index *
ip.typeOf(elem.base).toType().elemType2(mod).abiSize(mod)))),
mod.intern_pool.typeOf(elem.base).toType().elemType2(mod).abiSize(mod)))),
),
.field => |field| {
const base_type = ip.indexToKey(ip.typeOf(field.base)).ptr_type.child;
const base_type = mod.intern_pool.indexToKey(mod.intern_pool.typeOf(field.base)).ptr_type.child;
return lowerParentPtr(
bin_file,
src_loc,
field.base,
code,
debug_output,
reloc_info.offset(switch (ip.indexToKey(base_type)) {
reloc_info.offset(switch (mod.intern_pool.indexToKey(base_type)) {
.ptr_type => |ptr_type| switch (ptr_type.flags.size) {
.One, .Many, .C => unreachable,
.Slice => switch (field.index) {
@ -704,9 +703,9 @@ fn lowerParentPtr(
mod,
)),
.Packed => if (mod.typeToStruct(base_type.toType())) |struct_type|
math.divExact(u32, struct_type.fieldBitOffset(
ip,
field.index,
math.divExact(u16, mod.structPackedFieldBitOffset(
struct_type,
@intCast(field.index),
), 8) catch |err| switch (err) {
error.UnexpectedRemainder => 0,
error.DivisionByZero => unreachable,

2
src/codegen/c.zig
View File

@ -5429,7 +5429,7 @@ fn airStructFieldVal(f: *Function, inst: Air.Inst.Index) !CValue {
const bit_offset_ty = try mod.intType(.unsigned, Type.smallestUnsignedBits(int_info.bits - 1));
const bit_offset = struct_type.fieldBitOffset(ip, extra.field_index);
const bit_offset = mod.structPackedFieldBitOffset(struct_type, extra.field_index);
const bit_offset_val = try mod.intValue(bit_offset_ty, bit_offset);
const field_int_signedness = if (inst_ty.isAbiInt(mod))

3
src/codegen/llvm.zig
View File

@ -6192,7 +6192,6 @@ pub const FuncGen = struct {
fn airStructFieldVal(self: *FuncGen, body_tail: []const Air.Inst.Index) !Builder.Value {
const o = self.dg.object;
const mod = o.module;
const ip = &mod.intern_pool;
const inst = body_tail[0];
const ty_pl = self.air.instructions.items(.data)[inst].ty_pl;
const struct_field = self.air.extraData(Air.StructField, ty_pl.payload).data;
@ -6208,7 +6207,7 @@ pub const FuncGen = struct {
.Struct => switch (struct_ty.containerLayout(mod)) {
.Packed => {
const struct_type = mod.typeToStruct(struct_ty).?;
const bit_offset = struct_type.fieldBitOffset(ip, field_index);
const bit_offset = mod.structPackedFieldBitOffset(struct_type, field_index);
const containing_int = struct_llvm_val;
const shift_amt =
try o.builder.intValue(containing_int.typeOfWip(&self.wip), bit_offset);

12
src/type.zig
View File

@ -3025,8 +3025,16 @@ pub const Type = struct {
const ip = &mod.intern_pool;
const struct_type = ip.indexToKey(ty.toIntern()).struct_type;
assert(struct_type.layout == .Packed);
assert(struct_type.haveLayout(ip));
return struct_type.offsets.get(ip)[field_index];
comptime assert(Type.packed_struct_layout_version == 2);
var running_bits: u32 = 0;
for (struct_type.field_types.get(ip), 0..) |field_ty, i| {
if (i == field_index) break;
if (!field_ty.toType().hasRuntimeBits(mod)) continue;
const field_bits: u32 = @intCast(field_ty.toType().bitSize(mod));
running_bits += field_bits;
}
return running_bits;
}
pub fn packedStructFieldByteOffset(ty: Type, field_index: usize, mod: *Module) u32 {