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codegen: fix access to byte-aligned nested packed struct elems

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When acessing a packed struct member via a byte aligned ptr (from the optimisation in Sema.structFieldPtrByIndex())
the codegen must apply the parent ptr packed_offset in addition to the field offset itself.

resolves https://github.com/ziglang/zig/issues/16609
This commit is contained in:
Xavier Bouchoux
2023-07-29 11:50:25 +02:00
parent 46abf20454
commit 8c367ef99a
5 changed files with 115 additions and 12 deletions
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11
src/codegen/c.zig
View File

@@ -661,7 +661,7 @@ pub const DeclGen = struct {
try dg.renderCType(writer, ptr_cty);
try writer.writeByte(')');
}
switch (fieldLocation(base_ty, ptr_ty, @as(u32, @intCast(field.index)), mod)) {
switch (fieldLocation(ptr_base_ty, ptr_ty, @as(u32, @intCast(field.index)), mod)) {
.begin => try dg.renderParentPtr(writer, field.base, location),
.field => |name| {
try writer.writeAll("&(");
@@ -5187,7 +5187,7 @@ fn airOptionalPayloadPtrSet(f: *Function, inst: Air.Inst.Index) !CValue {
}
fn fieldLocation(
container_ty: Type,
container_ptr_ty: Type,
field_ptr_ty: Type,
field_index: u32,
mod: *Module,
@@ -5198,6 +5198,7 @@ fn fieldLocation(
end: void,
} {
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| {
@@ -5211,7 +5212,7 @@ fn fieldLocation(
.{ .identifier = ip.stringToSlice(container_ty.structFieldName(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) }
.{ .byte_offset = container_ty.packedStructFieldByteOffset(field_index, mod) + @divExact(container_ptr_ty.ptrInfo(mod).packed_offset.bit_offset, 8) }
else
.begin,
},
@@ -5282,7 +5283,7 @@ fn airFieldParentPtr(f: *Function, inst: Air.Inst.Index) !CValue {
try f.renderType(writer, container_ptr_ty);
try writer.writeByte(')');
switch (fieldLocation(container_ty, field_ptr_ty, extra.field_index, mod)) {
switch (fieldLocation(container_ptr_ty, field_ptr_ty, extra.field_index, mod)) {
.begin => try f.writeCValue(writer, field_ptr_val, .Initializer),
.field => |field| {
const u8_ptr_ty = try mod.adjustPtrTypeChild(field_ptr_ty, Type.u8);
@@ -5339,7 +5340,7 @@ fn fieldPtr(
try f.renderType(writer, field_ptr_ty);
try writer.writeByte(')');
switch (fieldLocation(container_ty, field_ptr_ty, field_index, mod)) {
switch (fieldLocation(container_ptr_ty, field_ptr_ty, field_index, mod)) {
.begin => try f.writeCValue(writer, container_ptr_val, .Initializer),
.field => |field| {
try writer.writeByte('&');

3
src/codegen/llvm.zig
View File

@@ -10611,6 +10611,7 @@ pub const FuncGen = struct {
.Packed => {
const result_ty = self.typeOfIndex(inst);
const result_ty_info = result_ty.ptrInfo(mod);
const struct_ptr_ty_info = struct_ptr_ty.ptrInfo(mod);
if (result_ty_info.packed_offset.host_size != 0) {
// From LLVM's perspective, a pointer to a packed struct and a pointer
@@ -10622,7 +10623,7 @@ pub const FuncGen = struct {
// We have a pointer to a packed struct field that happens to be byte-aligned.
// Offset our operand pointer by the correct number of bytes.
const byte_offset = struct_ty.packedStructFieldByteOffset(field_index, mod);
const byte_offset = struct_ty.packedStructFieldByteOffset(field_index, mod) + @divExact(struct_ptr_ty_info.packed_offset.bit_offset, 8);
if (byte_offset == 0) return struct_ptr;
const usize_ty = try o.lowerType(Type.usize);
const llvm_index = try o.builder.intValue(usize_ty, byte_offset);