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LLVM: fix lowering byte-aligned packed struct field pointers

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This commit is contained in:
Andrew Kelley 2022-07-27 13:22:33 -07:00
parent dfc7493dcb
commit f880af369d
3 changed files with 43 additions and 0 deletions
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18
src/codegen/llvm.zig
View File

@ -3646,6 +3646,24 @@ pub const DeclGen = struct {
},
.Struct => {
const field_ty = parent_ty.structFieldType(field_index);
if (parent_ty.containerLayout() == .Packed) {
const llvm_usize = dg.context.intType(target.cpu.arch.ptrBitWidth());
const base_addr = parent_llvm_ptr.constPtrToInt(llvm_usize);
// count bits of fields before this one
const prev_bits = b: {
var b: usize = 0;
for (parent_ty.structFields().values()[0..field_index]) |field| {
if (field.is_comptime or !field.ty.hasRuntimeBitsIgnoreComptime()) continue;
b += field.ty.bitSize(target);
}
break :b b;
};
const byte_offset = llvm_usize.constInt((prev_bits + 7) / 8, .False);
const field_addr = base_addr.constAdd(byte_offset);
bitcast_needed = false;
const final_llvm_ty = (try dg.lowerType(ptr_child_ty)).pointerType(0);
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;

3
src/codegen/llvm/bindings.zig
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@ -169,6 +169,9 @@ pub const Value = opaque {
pub const constNot = LLVMConstNot;
extern fn LLVMConstNot(ConstantVal: *const Value) *const Value;
pub const constAdd = LLVMConstAdd;
extern fn LLVMConstAdd(LHSConstant: *const Value, RHSConstant: *const Value) *const Value;
pub const setWeak = LLVMSetWeak;
extern fn LLVMSetWeak(CmpXchgInst: *const Value, IsWeak: Bool) void;

22
test/behavior/packed-struct.zig
View File

@ -436,3 +436,25 @@ test "load pointer from packed struct" {
try expect(i == 123);
}
}
test "@ptrToInt on a packed struct field" {
if (builtin.zig_backend == .stage2_c) return error.SkipZigTest;
if (builtin.zig_backend == .stage2_wasm) return error.SkipZigTest;
if (builtin.zig_backend == .stage2_x86_64) return error.SkipZigTest;
if (builtin.zig_backend == .stage2_aarch64) return error.SkipZigTest;
if (builtin.zig_backend == .stage2_arm) return error.SkipZigTest;
const S = struct {
const P = packed struct {
x: u8,
y: u8,
z: u32,
};
var p0: P = P{
.x = 1,
.y = 2,
.z = 0,
};
};
try expect(@ptrToInt(&S.p0.z) - @ptrToInt(&S.p0.x) == 2);
}