authorgravatar for jacobly@ziglang.orgJacob Young <jacobly@ziglang.org> 2022-12-18 01:25:19-05:00
committergravatar for jacobly@ziglang.orgJacob Young <jacobly@ziglang.org> 2022-12-18 22:11:26-05:00
loge96f65db7735ef80e19253ec25a1ce31751650f1
tree3356db8e593d43749b7ed2278ea1687428146ff8
parentaca9c74e80e106309b9783ff251ab0cdd3fb9626

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

* 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.

2 files changed, 38 insertions(+), 20 deletions(-)

src/codegen/llvm.zig+15-7
......@@ -4033,16 +4033,24 @@ pub const DeclGen = struct {
40334033 const final_llvm_ty = (try dg.lowerType(ptr_child_ty)).pointerType(0);
40344034 break :blk field_addr.constIntToPtr(final_llvm_ty);
40354035 }
4036 bitcast_needed = !field_ty.eql(ptr_child_ty, dg.module);
40374036
40384037 var ty_buf: Type.Payload.Pointer = undefined;
4039 const llvm_field_index = llvmFieldIndex(parent_ty, field_index, target, &ty_buf).?;
4040 const indices: [2]*llvm.Value = .{
4041 llvm_u32.constInt(0, .False),
4042 llvm_u32.constInt(llvm_field_index, .False),
4043 };
4038
40444039 const parent_llvm_ty = try dg.lowerType(parent_ty);
4045 break :blk parent_llvm_ty.constInBoundsGEP(parent_llvm_ptr, &indices, indices.len);
4040 if (llvmFieldIndex(parent_ty, field_index, target, &ty_buf)) |llvm_field_index| {
4041 bitcast_needed = !field_ty.eql(ptr_child_ty, dg.module);
4042 const indices: [2]*llvm.Value = .{
4043 llvm_u32.constInt(0, .False),
4044 llvm_u32.constInt(llvm_field_index, .False),
4045 };
4046 break :blk parent_llvm_ty.constInBoundsGEP(parent_llvm_ptr, &indices, indices.len);
4047 } else {
4048 bitcast_needed = !parent_ty.eql(ptr_child_ty, dg.module);
4049 const indices: [1]*llvm.Value = .{
4050 llvm_u32.constInt(1, .False),
4051 };
4052 break :blk parent_llvm_ty.constInBoundsGEP(parent_llvm_ptr, &indices, indices.len);
4053 }
40464054 },
40474055 .Pointer => {
40484056 assert(parent_ty.isSlice());
test/behavior/struct.zig+23-13
......@@ -1359,23 +1359,33 @@ test "under-aligned struct field" {
13591359 try expect(result == 1234);
13601360}
13611361
1362test "address of zero-bit field is equal to address of only field" {
1362test "fieldParentPtr of a zero-bit field" {
13631363 if (builtin.zig_backend == .stage2_x86_64) return error.SkipZigTest; // TODO
13641364 if (builtin.zig_backend == .stage2_aarch64) return error.SkipZigTest; // TODO
13651365 if (builtin.zig_backend == .stage2_arm) return error.SkipZigTest; // TODO
13661366
1367 {
1368 const A = struct { b: void = {}, u: u8 };
1369 var a = A{ .u = 0 };
1370 const a_ptr = @fieldParentPtr(A, "b", &a.b);
1371 try std.testing.expectEqual(&a, a_ptr);
1372 }
1373 {
1374 const A = struct { u: u8, b: void = {} };
1375 var a = A{ .u = 0 };
1376 const a_ptr = @fieldParentPtr(A, "b", &a.b);
1377 try std.testing.expectEqual(&a, a_ptr);
1378 }
1367 const S = struct {
1368 fn testOneType(comptime A: type) !void {
1369 {
1370 const a = A{ .u = 0 };
1371 const b_ptr = &a.b;
1372 const a_ptr = @fieldParentPtr(A, "b", b_ptr);
1373 try std.testing.expectEqual(&a, a_ptr);
1374 }
1375 {
1376 var a = A{ .u = 0 };
1377 const b_ptr = &a.b;
1378 const a_ptr = @fieldParentPtr(A, "b", b_ptr);
1379 try std.testing.expectEqual(&a, a_ptr);
1380 }
1381 }
1382 fn doTheTest() !void {
1383 try testOneType(struct { b: void = {}, u: u8 });
1384 try testOneType(struct { u: u8, b: void = {} });
1385 }
1386 };
1387 try S.doTheTest();
1388 comptime try S.doTheTest();
13791389}
13801390
13811391test "struct field has a pointer to an aligned version of itself" {