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llvm: fix lowering pointer to final zero-width field of a comptime value

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* Handle a `null` return from `llvmFieldIndex`.
 * Add a behavior test to test this code path.
 * Reword this test name, which incorrectly described how pointers to
   zero-bit fields behave, and instead describe the actual test.
This commit is contained in:
Jacob Young 2022-12-18 01:25:19 -05:00
parent 0ccdc511ce
commit e0bc5f65b9
2 changed files with 38 additions and 20 deletions
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14
src/codegen/llvm.zig
View File

@ -4033,16 +4033,24 @@ pub const DeclGen = struct {
const final_llvm_ty = (try dg.lowerType(ptr_child_ty)).pointerType(0); const final_llvm_ty = (try dg.lowerType(ptr_child_ty)).pointerType(0);
break :blk field_addr.constIntToPtr(final_llvm_ty); break :blk field_addr.constIntToPtr(final_llvm_ty);
} }
bitcast_needed = !field_ty.eql(ptr_child_ty, dg.module);
var ty_buf: Type.Payload.Pointer = undefined; var ty_buf: Type.Payload.Pointer = undefined;
const llvm_field_index = llvmFieldIndex(parent_ty, field_index, target, &ty_buf).?;
const parent_llvm_ty = try dg.lowerType(parent_ty);
if (llvmFieldIndex(parent_ty, field_index, target, &ty_buf)) |llvm_field_index| {
bitcast_needed = !field_ty.eql(ptr_child_ty, dg.module);
const indices: [2]*llvm.Value = .{ const indices: [2]*llvm.Value = .{
llvm_u32.constInt(0, .False), llvm_u32.constInt(0, .False),
llvm_u32.constInt(llvm_field_index, .False), llvm_u32.constInt(llvm_field_index, .False),
}; };
const parent_llvm_ty = try dg.lowerType(parent_ty);
break :blk parent_llvm_ty.constInBoundsGEP(parent_llvm_ptr, &indices, indices.len); break :blk parent_llvm_ty.constInBoundsGEP(parent_llvm_ptr, &indices, indices.len);
} else {
bitcast_needed = !parent_ty.eql(ptr_child_ty, dg.module);
const indices: [1]*llvm.Value = .{
llvm_u32.constInt(1, .False),
};
break :blk parent_llvm_ty.constInBoundsGEP(parent_llvm_ptr, &indices, indices.len);
}
}, },
.Pointer => { .Pointer => {
assert(parent_ty.isSlice()); assert(parent_ty.isSlice());

22
test/behavior/struct.zig
View File

@ -1359,24 +1359,34 @@ test "under-aligned struct field" {
try expect(result == 1234); try expect(result == 1234);
} }
test "address of zero-bit field is equal to address of only field" { test "fieldParentPtr of a zero-bit field" {
if (builtin.zig_backend == .stage2_x86_64) return error.SkipZigTest; // TODO if (builtin.zig_backend == .stage2_x86_64) return error.SkipZigTest; // TODO
if (builtin.zig_backend == .stage2_aarch64) return error.SkipZigTest; // TODO if (builtin.zig_backend == .stage2_aarch64) return error.SkipZigTest; // TODO
if (builtin.zig_backend == .stage2_arm) return error.SkipZigTest; // TODO if (builtin.zig_backend == .stage2_arm) return error.SkipZigTest; // TODO
const S = struct {
fn testOneType(comptime A: type) !void {
{ {
const A = struct { b: void = {}, u: u8 }; const a = A{ .u = 0 };
var a = A{ .u = 0 }; const b_ptr = &a.b;
const a_ptr = @fieldParentPtr(A, "b", &a.b); const a_ptr = @fieldParentPtr(A, "b", b_ptr);
try std.testing.expectEqual(&a, a_ptr); try std.testing.expectEqual(&a, a_ptr);
} }
{ {
const A = struct { u: u8, b: void = {} };
var a = A{ .u = 0 }; var a = A{ .u = 0 };
const a_ptr = @fieldParentPtr(A, "b", &a.b); const b_ptr = &a.b;
const a_ptr = @fieldParentPtr(A, "b", b_ptr);
try std.testing.expectEqual(&a, a_ptr); try std.testing.expectEqual(&a, a_ptr);
} }
} }
fn doTheTest() !void {
try testOneType(struct { b: void = {}, u: u8 });
try testOneType(struct { u: u8, b: void = {} });
}
};
try S.doTheTest();
comptime try S.doTheTest();
}
test "struct field has a pointer to an aligned version of itself" { test "struct field has a pointer to an aligned version of itself" {
if (builtin.zig_backend == .stage2_aarch64) return error.SkipZigTest; // TODO if (builtin.zig_backend == .stage2_aarch64) return error.SkipZigTest; // TODO