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ability to write to bit fields

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See #261
This commit is contained in:
Andrew Kelley 2017-02-16 18:42:52 -05:00
parent b6e7a0dadd
commit 244362fed7
2 changed files with 47 additions and 10 deletions
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38
src/codegen.cpp
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@ -1410,17 +1410,45 @@ static LLVMValueRef ir_render_store_ptr(CodeGen *g, IrExecutable *executable, Ir
TypeTableEntry *ptr_type = get_underlying_type(instruction->ptr->value.type);
TypeTableEntry *child_type = get_underlying_type(ptr_type->data.pointer.child_type);
if (!type_has_bits(child_type)) {
if (!type_has_bits(child_type))
return nullptr;
}
if (handle_is_ptr(child_type)) {
if (handle_is_ptr(child_type))
return gen_struct_memcpy(g, value, ptr, child_type);
uint32_t bit_offset = ptr_type->data.pointer.bit_offset;
if (bit_offset == 0) {
LLVMTypeRef ptr_child_ref = LLVMGetElementType(LLVMTypeOf(ptr));
bool need_to_do_some_bit_stuff =
LLVMGetTypeKind(ptr_child_ref) == LLVMIntegerTypeKind &&
LLVMGetTypeKind(child_type->type_ref) == LLVMIntegerTypeKind &&
LLVMGetIntTypeWidth(child_type->type_ref) < LLVMGetIntTypeWidth(ptr_child_ref);
if (!need_to_do_some_bit_stuff) {
LLVMValueRef llvm_instruction = LLVMBuildStore(g->builder, value, ptr);
LLVMSetVolatile(llvm_instruction, ptr_type->data.pointer.is_volatile);
return nullptr;
}
}
LLVMValueRef llvm_instruction = LLVMBuildStore(g->builder, value, ptr);
LLVMValueRef containing_int = LLVMBuildLoad(g->builder, ptr, "");
uint32_t child_bit_count = type_size_bits(g, child_type);
uint32_t host_bit_count = LLVMGetIntTypeWidth(LLVMTypeOf(containing_int));
uint32_t shift_amt = host_bit_count - bit_offset - child_bit_count;
LLVMValueRef shift_amt_val = LLVMConstInt(LLVMTypeOf(containing_int), shift_amt, false);
LLVMValueRef mask_val = LLVMConstAllOnes(child_type->type_ref);
mask_val = LLVMConstZExt(mask_val, LLVMTypeOf(containing_int));
mask_val = LLVMConstShl(mask_val, shift_amt_val);
mask_val = LLVMConstNot(mask_val);
LLVMValueRef anded_containing_int = LLVMBuildAnd(g->builder, containing_int, mask_val, "");
LLVMValueRef extended_value = LLVMBuildZExt(g->builder, value, LLVMTypeOf(containing_int), "");
LLVMValueRef shifted_value = LLVMBuildShl(g->builder, extended_value, shift_amt_val, "");
LLVMValueRef ored_value = LLVMBuildOr(g->builder, shifted_value, anded_containing_int, "");
LLVMValueRef llvm_instruction = LLVMBuildStore(g->builder, ored_value, ptr);
LLVMSetVolatile(llvm_instruction, ptr_type->data.pointer.is_volatile);
return nullptr;
}

19
test/cases/struct.zig
View File

@ -236,18 +236,27 @@ const BitField1 = packed struct {
c: u2,
};
const bit_field_1 = BitField1 {
.a = 1,
.b = 2,
.c = 3,
};
fn bitFieldAccess() {
@setFnTest(this);
const data = BitField1 {
.a = 1,
.b = 2,
.c = 3,
};
var data = bit_field_1;
assert(getA(&data) == 1);
assert(getB(&data) == 2);
assert(getC(&data) == 3);
comptime assert(@sizeOf(BitField1) == 1);
data.b += 1;
assert(data.b == 3);
data.a += 1;
assert(data.a == 2);
assert(data.b == 3);
}
fn getA(data: &const BitField1) -> u3 {