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codegen: fix field offsets in packed structs

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* add nested packed struct/union behavior tests
 * use ptr_info.packed_offset rather than trying to duplicate the logic from Sema.structFieldPtrByIndex()
 * use the container_ptr_info.packed_offset to account for non-aligned nested structs.
 * dedup type.packedStructFieldBitOffset() and module.structPackedFieldBitOffset()
This commit is contained in:
Xavier Bouchoux
2023-07-29 20:08:08 +02:00
parent 412d863ba5
commit 62d178e91a
7 changed files with 362 additions and 65 deletions
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20
src/codegen/c.zig
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@@ -5269,22 +5269,26 @@ fn fieldLocation(
const ip = &mod.intern_pool;
const container_ty = container_ptr_ty.childType(mod);
return switch (container_ty.zigTypeTag(mod)) {
.Struct => switch (container_ty.containerLayout(mod)) {
.Auto, .Extern => for (field_index..container_ty.structFieldCount(mod)) |next_field_index_usize| {
.Struct => blk: {
if (mod.typeToPackedStruct(container_ty)) |struct_type| {
if (field_ptr_ty.ptrInfo(mod).packed_offset.host_size == 0)
break :blk .{ .byte_offset = @divExact(mod.structPackedFieldBitOffset(struct_type, field_index) + container_ptr_ty.ptrInfo(mod).packed_offset.bit_offset, 8) }
else
break :blk .begin;
}
for (field_index..container_ty.structFieldCount(mod)) |next_field_index_usize| {
const next_field_index: u32 = @intCast(next_field_index_usize);
if (container_ty.structFieldIsComptime(next_field_index, mod)) continue;
const field_ty = container_ty.structFieldType(next_field_index, mod);
if (!field_ty.hasRuntimeBitsIgnoreComptime(mod)) continue;
break .{ .field = if (container_ty.isSimpleTuple(mod))
break :blk .{ .field = if (container_ty.isSimpleTuple(mod))
.{ .field = next_field_index }
else
.{ .identifier = ip.stringToSlice(container_ty.legacyStructFieldName(next_field_index, mod)) } };
} else if (container_ty.hasRuntimeBitsIgnoreComptime(mod)) .end else .begin,
.Packed => if (field_ptr_ty.ptrInfo(mod).packed_offset.host_size == 0)
.{ .byte_offset = container_ty.packedStructFieldByteOffset(field_index, mod) + @divExact(container_ptr_ty.ptrInfo(mod).packed_offset.bit_offset, 8) }
else
.begin,
}
break :blk if (container_ty.hasRuntimeBitsIgnoreComptime(mod)) .end else .begin;
},
.Union => {
const union_obj = mod.typeToUnion(container_ty).?;

42
src/codegen/llvm.zig
View File

@@ -4,7 +4,6 @@ const assert = std.debug.assert;
const Allocator = std.mem.Allocator;
const log = std.log.scoped(.codegen);
const math = std.math;
const native_endian = builtin.cpu.arch.endian();
const DW = std.dwarf;
const Builder = @import("llvm/Builder.zig");
@@ -3770,7 +3769,7 @@ pub const Object = struct {
.opt_payload,
.elem,
.field,
=> try o.lowerParentPtr(val, ty.ptrInfo(mod).packed_offset.bit_offset % 8 == 0),
=> try o.lowerParentPtr(val),
.comptime_field => unreachable,
};
switch (ptr.len) {
@@ -4230,15 +4229,16 @@ pub const Object = struct {
return o.lowerDeclRefValue(ptr_ty, decl_index);
}
fn lowerParentPtr(o: *Object, ptr_val: Value, byte_aligned: bool) Allocator.Error!Builder.Constant {
fn lowerParentPtr(o: *Object, ptr_val: Value) Allocator.Error!Builder.Constant {
const mod = o.module;
const ip = &mod.intern_pool;
return switch (ip.indexToKey(ptr_val.toIntern()).ptr.addr) {
const ptr = ip.indexToKey(ptr_val.toIntern()).ptr;
return switch (ptr.addr) {
.decl => |decl| o.lowerParentPtrDecl(decl),
.mut_decl => |mut_decl| o.lowerParentPtrDecl(mut_decl.decl),
.int => |int| try o.lowerIntAsPtr(int),
.eu_payload => |eu_ptr| {
const parent_ptr = try o.lowerParentPtr(eu_ptr.toValue(), true);
const parent_ptr = try o.lowerParentPtr(eu_ptr.toValue());
const eu_ty = ip.typeOf(eu_ptr).toType().childType(mod);
const payload_ty = eu_ty.errorUnionPayload(mod);
@@ -4256,7 +4256,7 @@ pub const Object = struct {
});
},
.opt_payload => |opt_ptr| {
const parent_ptr = try o.lowerParentPtr(opt_ptr.toValue(), true);
const parent_ptr = try o.lowerParentPtr(opt_ptr.toValue());
const opt_ty = ip.typeOf(opt_ptr).toType().childType(mod);
const payload_ty = opt_ty.optionalChild(mod);
@@ -4274,7 +4274,7 @@ pub const Object = struct {
},
.comptime_field => unreachable,
.elem => |elem_ptr| {
const parent_ptr = try o.lowerParentPtr(elem_ptr.base.toValue(), true);
const parent_ptr = try o.lowerParentPtr(elem_ptr.base.toValue());
const elem_ty = ip.typeOf(elem_ptr.base).toType().elemType2(mod);
return o.builder.gepConst(.inbounds, try o.lowerType(elem_ty), parent_ptr, null, &.{
@@ -4282,9 +4282,9 @@ pub const Object = struct {
});
},
.field => |field_ptr| {
const parent_ptr = try o.lowerParentPtr(field_ptr.base.toValue(), byte_aligned);
const parent_ty = ip.typeOf(field_ptr.base).toType().childType(mod);
const parent_ptr = try o.lowerParentPtr(field_ptr.base.toValue());
const parent_ptr_ty = ip.typeOf(field_ptr.base).toType();
const parent_ty = parent_ptr_ty.childType(mod);
const field_index: u32 = @intCast(field_ptr.index);
switch (parent_ty.zigTypeTag(mod)) {
.Union => {
@@ -4309,22 +4309,14 @@ pub const Object = struct {
},
.Struct => {
if (mod.typeToPackedStruct(parent_ty)) |struct_type| {
if (!byte_aligned) return parent_ptr;
const ptr_info = ptr.ty.toType().ptrInfo(mod);
if (ptr_info.packed_offset.host_size != 0) return parent_ptr;
const parent_ptr_info = parent_ptr_ty.ptrInfo(mod);
const bit_offset = mod.structPackedFieldBitOffset(struct_type, field_index) + parent_ptr_info.packed_offset.bit_offset;
const llvm_usize = try o.lowerType(Type.usize);
const base_addr =
try o.builder.castConst(.ptrtoint, parent_ptr, llvm_usize);
// count bits of fields before this one
// TODO https://github.com/ziglang/zig/issues/17178
const prev_bits = b: {
var b: usize = 0;
for (0..field_index) |i| {
const field_ty = struct_type.field_types.get(ip)[i].toType();
if (!field_ty.hasRuntimeBitsIgnoreComptime(mod)) continue;
b += @intCast(field_ty.bitSize(mod));
}
break :b b;
};
const byte_offset = try o.builder.intConst(llvm_usize, prev_bits / 8);
const base_addr = try o.builder.castConst(.ptrtoint, parent_ptr, llvm_usize);
const byte_offset = try o.builder.intConst(llvm_usize, @divExact(bit_offset, 8));
const field_addr = try o.builder.binConst(.add, base_addr, byte_offset);
return o.builder.castConst(.inttoptr, field_addr, .ptr);
}