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better field access of types which have one possible value 

* When you do field access of a type which only has one possible
   value, the result is comptime-known.
 * StorePtr instructions which operate on pointers to types which
   only have one possible value, the result is a comptime no-op.

closes #1554
master
Andrew Kelley 2019-02-21 16:09:14 -05:00
parent 1066004b79
commit cbce61a209
No known key found for this signature in database
GPG Key ID: 7C5F548F728501A9
2 changed files with 30 additions and 10 deletions
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32
src/ir.cpp
View File

@ -13779,16 +13779,26 @@ static IrInstruction *ir_analyze_store_ptr(IrAnalyze *ira, IrInstruction *source
return ir_const_void(ira, source_instr);
}
ZigType *child_type = ptr->value.type->data.pointer.child_type;
if (ptr->value.type->data.pointer.is_const && !source_instr->is_gen) {
ir_add_error(ira, source_instr, buf_sprintf("cannot assign to constant"));
return ira->codegen->invalid_instruction;
}
ZigType *child_type = ptr->value.type->data.pointer.child_type;
IrInstruction *value = ir_implicit_cast(ira, uncasted_value, child_type);
if (value == ira->codegen->invalid_instruction)
return ira->codegen->invalid_instruction;
switch (type_has_one_possible_value(ira->codegen, child_type)) {
case OnePossibleValueInvalid:
return ira->codegen->invalid_instruction;
case OnePossibleValueYes:
return ir_const_void(ira, source_instr);
case OnePossibleValueNo:
break;
}
if (instr_is_comptime(ptr) && ptr->value.data.x_ptr.special != ConstPtrSpecialHardCodedAddr) {
if (ptr->value.data.x_ptr.mut == ConstPtrMutComptimeConst) {
ir_add_error(ira, source_instr, buf_sprintf("cannot assign to constant"));
@ -13809,15 +13819,7 @@ static IrInstruction *ir_analyze_store_ptr(IrAnalyze *ira, IrInstruction *source
bool same_global_refs = ptr->value.data.x_ptr.mut != ConstPtrMutComptimeVar;
copy_const_val(dest_val, &value->value, same_global_refs);
if (!ira->new_irb.current_basic_block->must_be_comptime_source_instr) {
switch (type_has_one_possible_value(ira->codegen, child_type)) {
case OnePossibleValueInvalid:
return ira->codegen->invalid_instruction;
case OnePossibleValueNo:
ira->new_irb.current_basic_block->must_be_comptime_source_instr = source_instr;
break;
case OnePossibleValueYes:
break;
}
ira->new_irb.current_basic_block->must_be_comptime_source_instr = source_instr;
}
return ir_const_void(ira, source_instr);
}
@ -15346,6 +15348,16 @@ static IrInstruction *ir_analyze_container_field_ptr(IrAnalyze *ira, Buf *field_
if (bare_type->id == ZigTypeIdStruct) {
TypeStructField *field = find_struct_type_field(bare_type, field_name);
if (field) {
switch (type_has_one_possible_value(ira->codegen, field->type_entry)) {
case OnePossibleValueInvalid:
return ira->codegen->invalid_instruction;
case OnePossibleValueYes: {
IrInstruction *elem = ir_const(ira, source_instr, field->type_entry);
return ir_get_ref(ira, source_instr, elem, false, false);
}
case OnePossibleValueNo:
break;
}
bool is_packed = (bare_type->data.structure.layout == ContainerLayoutPacked);
uint32_t align_bytes = is_packed ? 1 : get_abi_alignment(ira->codegen, field->type_entry);
uint32_t ptr_bit_offset = container_ptr->value.type->data.pointer.bit_offset_in_host;

8
test/stage1/behavior/struct.zig
View File

@ -491,3 +491,11 @@ test "non-byte-aligned array inside packed struct" {
S.doTheTest();
comptime S.doTheTest();
}
test "packed struct with u0 field access" {
const S = packed struct {
f0: u0,
};
var s = S{ .f0 = 0 };
comptime expect(s.f0 == 0);
}