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Force LLVM to generate byte-aligned packed unions 

Sometimes the frontend and LLVM would disagree on the ABI alignment of a
packed union. Solve the problem by telling LLVM we're gonna manage the
struct layout by ourselves.

Closes #3184
master
LemonBoy 2019-09-07 11:17:12 +02:00 committed by Andrew Kelley
parent a06f84fcc6
commit 8fbae77770
No known key found for this signature in database
GPG Key ID: 7C5F548F728501A9
2 changed files with 17 additions and 3 deletions
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8
src/analyze.cpp
View File

@ -7905,6 +7905,8 @@ static void resolve_llvm_types_enum(CodeGen *g, ZigType *enum_type, ResolveStatu
static void resolve_llvm_types_union(CodeGen *g, ZigType *union_type, ResolveStatus wanted_resolve_status) {
if (union_type->data.unionation.resolve_status >= wanted_resolve_status) return;
bool packed = (union_type->data.unionation.layout == ContainerLayoutPacked);
TypeUnionField *most_aligned_union_member = union_type->data.unionation.most_aligned_union_member;
ZigType *tag_type = union_type->data.unionation.tag_type;
uint32_t gen_field_count = union_type->data.unionation.gen_field_count;
@ -7971,9 +7973,9 @@ static void resolve_llvm_types_union(CodeGen *g, ZigType *union_type, ResolveSta
most_aligned_union_member->type_entry->llvm_type,
get_llvm_type(g, padding_array),
};
LLVMStructSetBody(union_type->llvm_type, union_element_types, 2, false);
LLVMStructSetBody(union_type->llvm_type, union_element_types, 2, packed);
} else {
LLVMStructSetBody(union_type->llvm_type, &most_aligned_union_member->type_entry->llvm_type, 1, false);
LLVMStructSetBody(union_type->llvm_type, &most_aligned_union_member->type_entry->llvm_type, 1, packed);
}
union_type->data.unionation.union_llvm_type = union_type->llvm_type;
union_type->data.unionation.gen_tag_index = SIZE_MAX;
@ -8012,7 +8014,7 @@ static void resolve_llvm_types_union(CodeGen *g, ZigType *union_type, ResolveSta
LLVMTypeRef root_struct_element_types[2];
root_struct_element_types[union_type->data.unionation.gen_tag_index] = get_llvm_type(g, tag_type);
root_struct_element_types[union_type->data.unionation.gen_union_index] = union_type_ref;
LLVMStructSetBody(union_type->llvm_type, root_struct_element_types, 2, false);
LLVMStructSetBody(union_type->llvm_type, root_struct_element_types, 2, packed);
// create debug type for union
ZigLLVMDIType *union_di_type = ZigLLVMCreateDebugUnionType(g->dbuilder,

12
test/stage1/behavior/union.zig
View File

@ -482,3 +482,15 @@ test "comparison between union and enum literal" {
testComparison();
comptime testComparison();
}
test "packed union generates correctly aligned LLVM type" {
const U = packed union {
f1: fn () void,
f2: u32,
};
var foo = [_]U{
U{ .f1 = doTest },
U{ .f2 = 0 },
};
foo[0].f1();
}