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ir: More changes to sentinel-terminated const arrays

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* Don't add an extra slot for the sentinel. Most of the code keeps using
  the constant value from the type descriptor, let's harmonize all the
  code dealing with sentinels.

* Properly write out sentinel values when reinterpreting pointers at
  comptime.

* Allow the reading of the 0th element in a `[0:S]T` type.
This commit is contained in:
LemonBoy 2020-03-19 11:52:15 +01:00 committed by Andrew Kelley
parent 7a361751e5
commit e3c92d0532
4 changed files with 44 additions and 28 deletions
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7
src/analyze.cpp
View File

@ -5806,18 +5806,13 @@ ZigValue *get_the_one_possible_value(CodeGen *g, ZigType *type_entry) {
// The elements array cannot be left unpopulated
ZigType *array_type = result->type;
ZigType *elem_type = array_type->data.array.child_type;
ZigValue *sentinel_value = array_type->data.array.sentinel;
const size_t elem_count = array_type->data.array.len + (sentinel_value != nullptr);
const size_t elem_count = array_type->data.array.len;
result->data.x_array.data.s_none.elements = g->pass1_arena->allocate<ZigValue>(elem_count);
for (size_t i = 0; i < elem_count; i += 1) {
ZigValue *elem_val = &result->data.x_array.data.s_none.elements[i];
copy_const_val(g, elem_val, get_the_one_possible_value(g, elem_type));
}
if (sentinel_value != nullptr) {
ZigValue *last_elem_val = &result->data.x_array.data.s_none.elements[elem_count - 1];
copy_const_val(g, last_elem_val, sentinel_value);
}
} else if (result->type->id == ZigTypeIdPointer) {
result->data.x_ptr.special = ConstPtrSpecialRef;
result->data.x_ptr.data.ref.pointee = get_the_one_possible_value(g, result->type->data.pointer.child_type);

39
src/codegen.cpp
View File

@ -3584,9 +3584,7 @@ static bool value_is_all_undef(CodeGen *g, ZigValue *const_val) {
}
return true;
} else if (const_val->type->id == ZigTypeIdArray) {
const size_t full_len = const_val->type->data.array.len +
(const_val->type->data.array.sentinel != nullptr);
return value_is_all_undef_array(g, const_val, full_len);
return value_is_all_undef_array(g, const_val, const_val->type->data.array.len);
} else if (const_val->type->id == ZigTypeIdVector) {
return value_is_all_undef_array(g, const_val, const_val->type->data.vector.len);
} else {
@ -6792,6 +6790,22 @@ static LLVMValueRef pack_const_int(CodeGen *g, LLVMTypeRef big_int_type_ref, Zig
used_bits += packed_bits_size;
}
}
if (type_entry->data.array.sentinel != nullptr) {
ZigValue *elem_val = type_entry->data.array.sentinel;
LLVMValueRef child_val = pack_const_int(g, big_int_type_ref, elem_val);
if (is_big_endian) {
LLVMValueRef shift_amt = LLVMConstInt(big_int_type_ref, packed_bits_size, false);
val = LLVMConstShl(val, shift_amt);
val = LLVMConstOr(val, child_val);
} else {
LLVMValueRef shift_amt = LLVMConstInt(big_int_type_ref, used_bits, false);
LLVMValueRef child_val_shifted = LLVMConstShl(child_val, shift_amt);
val = LLVMConstOr(val, child_val_shifted);
used_bits += packed_bits_size;
}
}
return val;
}
case ZigTypeIdVector:
@ -6858,20 +6872,11 @@ static LLVMValueRef gen_const_val_ptr(CodeGen *g, ZigValue *const_val, const cha
ZigValue *array_const_val = const_val->data.x_ptr.data.base_array.array_val;
assert(array_const_val->type->id == ZigTypeIdArray);
if (!type_has_bits(g, array_const_val->type)) {
if (array_const_val->type->data.array.sentinel != nullptr) {
ZigValue *pointee = array_const_val->type->data.array.sentinel;
render_const_val(g, pointee, "");
render_const_val_global(g, pointee, "");
const_val->llvm_value = LLVMConstBitCast(pointee->llvm_global,
get_llvm_type(g, const_val->type));
return const_val->llvm_value;
} else {
// make this a null pointer
ZigType *usize = g->builtin_types.entry_usize;
const_val->llvm_value = LLVMConstIntToPtr(LLVMConstNull(usize->llvm_type),
get_llvm_type(g, const_val->type));
return const_val->llvm_value;
}
// make this a null pointer
ZigType *usize = g->builtin_types.entry_usize;
const_val->llvm_value = LLVMConstIntToPtr(LLVMConstNull(usize->llvm_type),
get_llvm_type(g, const_val->type));
return const_val->llvm_value;
}
size_t elem_index = const_val->data.x_ptr.data.base_array.elem_index;
LLVMValueRef uncasted_ptr_val = gen_const_ptr_array_recursive(g, array_const_val, elem_index);

8
src/ir.cpp
View File

@ -20578,11 +20578,6 @@ static IrInstGen *ir_analyze_instruction_elem_ptr(IrAnalyze *ira, IrInstSrcElemP
}
if (array_type->id == ZigTypeIdArray) {
if (array_type->data.array.len == 0) {
ir_add_error_node(ira, elem_ptr_instruction->base.base.source_node,
buf_sprintf("index 0 outside array of size 0"));
return ira->codegen->invalid_inst_gen;
}
ZigType *child_type = array_type->data.array.child_type;
if (ptr_type->data.pointer.host_int_bytes == 0) {
return_type = get_pointer_to_type_extra(ira->codegen, child_type,
@ -27657,6 +27652,9 @@ static void buf_write_value_bytes_array(CodeGen *codegen, uint8_t *buf, ZigValue
buf_write_value_bytes(codegen, &buf[buf_i], elem);
buf_i += type_size(codegen, elem->type);
}
if (val->type->id == ZigTypeIdArray && val->type->data.array.sentinel != nullptr) {
buf_write_value_bytes(codegen, &buf[buf_i], val->type->data.array.sentinel);
}
}
static void buf_write_value_bytes(CodeGen *codegen, uint8_t *buf, ZigValue *val) {

18
test/stage1/behavior/array.zig
View File

@ -28,6 +28,24 @@ fn getArrayLen(a: []const u32) usize {
return a.len;
}
test "array with sentinels" {
const S = struct {
fn doTheTest(is_ct: bool) void {
var zero_sized: [0:0xde]u8 = [_:0xde]u8{};
expectEqual(@as(u8, 0xde), zero_sized[0]);
// Disabled at runtime because of
// https://github.com/ziglang/zig/issues/4372
if (is_ct) {
var reinterpreted = @ptrCast(*[1]u8, &zero_sized);
expectEqual(@as(u8, 0xde), reinterpreted[0]);
}
}
};
S.doTheTest(false);
comptime S.doTheTest(true);
}
test "void arrays" {
var array: [4]void = undefined;
array[0] = void{};