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reading from a bit field partially works

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See #261

Still need to do:
 * reading a field that has bit offset 0 but still needs to
   shift and truncate
 * writing a field
This commit is contained in:
Andrew Kelley
2017-02-16 15:45:41 -05:00
parent 4b5cc80f66
commit fc5d47b9b9
6 changed files with 66 additions and 9 deletions
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23
src/codegen.cpp
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@@ -1379,14 +1379,31 @@ static LLVMValueRef ir_render_decl_var(CodeGen *g, IrExecutable *executable,
static LLVMValueRef ir_render_load_ptr(CodeGen *g, IrExecutable *executable, IrInstructionLoadPtr *instruction) {
TypeTableEntry *child_type = instruction->base.value.type;
if (!type_has_bits(child_type)) {
if (!type_has_bits(child_type))
return nullptr;
}
LLVMValueRef ptr = ir_llvm_value(g, instruction->ptr);
TypeTableEntry *ptr_type = instruction->ptr->value.type;
assert(ptr_type->id == TypeTableEntryIdPointer);
bool is_volatile = ptr_type->data.pointer.is_volatile;
return get_handle_value(g, ptr, child_type, is_volatile);
uint32_t bit_offset = ptr_type->data.pointer.bit_offset;
if (bit_offset == 0)
return get_handle_value(g, ptr, child_type, is_volatile);
assert(!handle_is_ptr(child_type));
LLVMValueRef containing_int = LLVMBuildLoad(g->builder, ptr, "");
LLVMSetVolatile(containing_int, is_volatile);
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 shifted_value = LLVMBuildLShr(g->builder, containing_int, shift_amt_val, "");
return LLVMBuildTrunc(g->builder, shifted_value, child_type->type_ref, "");
}
static LLVMValueRef ir_render_store_ptr(CodeGen *g, IrExecutable *executable, IrInstructionStorePtr *instruction) {