Commit 244362fed7ed9280a0612c7c57ed67f6fa33b40d | zig

author	Andrew Kelley <andrew@ziglang.org> 2017-02-16 18:42:52-05:00
committer	Andrew Kelley <andrew@ziglang.org> 2017-02-16 18:42:52-05:00
log	244362fed7ed9280a0612c7c57ed67f6fa33b40d
tree	5d204f4e7aea69e2d5986015edb236c69a6dc582
parent	b6e7a0dadd86ce401e82ec53d6874e9934826c2d

ability to write to bit fields

See #261

2 files changed, 47 insertions(+), 10 deletions(-)

src
- codegen.cpp
test
- cases
  - struct.zig

src/codegen.cpp+33-5

...	@@ -1410,17 +1410,45 @@ static LLVMValueRef ir_render_store_ptr(CodeGen g, IrExecutable executable, Ir	...	@@ -1410,17 +1410,45 @@ static LLVMValueRef ir_render_store_ptr(CodeGen g, IrExecutable executable, Ir
1410	TypeTableEntry *ptr_type = get_underlying_type(instruction->ptr->value.type);	1410	TypeTableEntry *ptr_type = get_underlying_type(instruction->ptr->value.type);
1411	TypeTableEntry *child_type = get_underlying_type(ptr_type->data.pointer.child_type);	1411	TypeTableEntry *child_type = get_underlying_type(ptr_type->data.pointer.child_type);
1412		1412
1413	if (!type_has_bits(child_type)) {	1413	if (!type_has_bits(child_type))
1414	return nullptr;	1414	return nullptr;
1415	}	1415
1416	if (handle_is_ptr(child_type)) {	1416	if (handle_is_ptr(child_type))
1417	return gen_struct_memcpy(g, value, ptr, child_type);	1417	return gen_struct_memcpy(g, value, ptr, child_type);
		1418
		1419	uint32_t bit_offset = ptr_type->data.pointer.bit_offset;
		1420	if (bit_offset == 0) {
		1421	LLVMTypeRef ptr_child_ref = LLVMGetElementType(LLVMTypeOf(ptr));
		1422	bool need_to_do_some_bit_stuff =
		1423	LLVMGetTypeKind(ptr_child_ref) == LLVMIntegerTypeKind &&
		1424	LLVMGetTypeKind(child_type->type_ref) == LLVMIntegerTypeKind &&
		1425	LLVMGetIntTypeWidth(child_type->type_ref) < LLVMGetIntTypeWidth(ptr_child_ref);
		1426	if (!need_to_do_some_bit_stuff) {
		1427	LLVMValueRef llvm_instruction = LLVMBuildStore(g->builder, value, ptr);
		1428	LLVMSetVolatile(llvm_instruction, ptr_type->data.pointer.is_volatile);
		1429	return nullptr;
		1430	}
1418	}	1431	}
1419		1432
1420	LLVMValueRef llvm_instruction = LLVMBuildStore(g->builder, value, ptr);	1433	LLVMValueRef containing_int = LLVMBuildLoad(g->builder, ptr, "");
1421		1434
1422	LLVMSetVolatile(llvm_instruction, ptr_type->data.pointer.is_volatile);	1435	uint32_t child_bit_count = type_size_bits(g, child_type);
		1436	uint32_t host_bit_count = LLVMGetIntTypeWidth(LLVMTypeOf(containing_int));
		1437	uint32_t shift_amt = host_bit_count - bit_offset - child_bit_count;
		1438	LLVMValueRef shift_amt_val = LLVMConstInt(LLVMTypeOf(containing_int), shift_amt, false);
		1439
		1440	LLVMValueRef mask_val = LLVMConstAllOnes(child_type->type_ref);
		1441	mask_val = LLVMConstZExt(mask_val, LLVMTypeOf(containing_int));
		1442	mask_val = LLVMConstShl(mask_val, shift_amt_val);
		1443	mask_val = LLVMConstNot(mask_val);
1423		1444
		1445	LLVMValueRef anded_containing_int = LLVMBuildAnd(g->builder, containing_int, mask_val, "");
		1446	LLVMValueRef extended_value = LLVMBuildZExt(g->builder, value, LLVMTypeOf(containing_int), "");
		1447	LLVMValueRef shifted_value = LLVMBuildShl(g->builder, extended_value, shift_amt_val, "");
		1448	LLVMValueRef ored_value = LLVMBuildOr(g->builder, shifted_value, anded_containing_int, "");
		1449
		1450	LLVMValueRef llvm_instruction = LLVMBuildStore(g->builder, ored_value, ptr);
		1451	LLVMSetVolatile(llvm_instruction, ptr_type->data.pointer.is_volatile);
1424	return nullptr;	1452	return nullptr;
1425	}	1453	}
1426		1454

test/cases/struct.zig+14-5

 @@ -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 {
+    var data = bit_field_1;
-        .a = 1,
-        .b = 2,
-        .c = 3,
-    };
     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 {