// endBody finalizes the generation of the function body.
func (f *Function) endBody() error {
if block := f.curBlock; block != nil && block.Term() == nil {
switch {
case f.Function.Name() == "main":
// From C11 spec $5.1.2.2.3.
//
// "If the return type of the main function is a type compatible with
// int, a return from the initial call to the main function is
// equivalent to calling the exit function with the value returned by
// the main function as its argument; reaching the } that terminates
// the main function returns a value of 0."
result := f.Sig().Result()
zero := constZero(result)
term, err := instruction.NewRet(zero)
if err != nil {
panic(fmt.Sprintf("unable to create ret terminator; %v", err))
}
block.SetTerm(term)
default:
// Add void return terminator to the current basic block, if a
// terminator is missing.
switch result := f.Sig().Result(); {
case irtypes.IsVoid(result):
term, err := instruction.NewRet(nil)
if err != nil {
panic(fmt.Sprintf("unable to create ret instruction; %v", err))
}
block.SetTerm(term)
default:
// The semantic analysis checker guarantees that all branches of
// non-void functions end with return statements. Therefore, if we
// reach the current basic block doesn't have a terminator at the
// end of the function body, it must be unreachable.
term, err := instruction.NewUnreachable()
if err != nil {
panic(fmt.Sprintf("unable to create unreachable instruction; %v", err))
}
block.SetTerm(term)
}
}
}
f.curBlock = nil
if err := f.AssignIDs(); err != nil {
return errutil.Err(err)
}
return nil
}
// assignIDs assigns unique IDs to unnamed basic blocks and local variable
// definitions.
func (block *BasicBlock) assignIDs() error {
f := block.Parent()
// Named represents a named basic block or local variable definition.
type Named interface {
Name() string
SetName(name string)
}
// setName assigns unique local IDs to unnamed basic blocks and local
// variable definitions.
setName := func(n Named) error {
// TODO: Ensure that global variables cannot be mixed up with local
// variables. This should be easy, as global variables may not be unnamed.
// Check that global variables are always given a name during creation.
if name := n.Name(); len(name) == 0 {
n.SetName(f.nextID())
} else if isLocalID(name) {
// Validate that explicitly named local IDs conform to the localID
// counter and update the localID counter to keep explicitly and
// implicitly named local IDs in sync.
if want := f.nextID(); name != want {
return errutil.Newf("invalid local ID; expected %s, got %s", enc.Local(want), enc.Local(name))
}
}
return nil
}
// Assign unique local IDs to unnamed basic blocks.
if err := setName(block); err != nil {
return errutil.Err(err)
}
// Assign unique local IDs to unnamed local variable definitions.
for _, inst := range block.Insts() {
if def, ok := inst.(*instruction.LocalVarDef); ok {
if !types.IsVoid(def.ValInst().RetType()) {
if err := setName(def); err != nil {
return errutil.Err(err)
}
}
}
}
return nil
}
// NewRet returns a new ret instruction based on the given return value. A nil
// return value indicates a "void" return instruction.
func NewRet(val value.Value) (*Ret, error) {
if val != nil && types.IsVoid(val.Type()) {
return nil, errutil.Newf(`expected no return value for return type "void"; got %q`, val)
}
return &Ret{val: val}, nil
}
// String returns the string representation of the local variable definition;
// e.g.
//
// %foo = add i32 13, 42
func (def *LocalVarDef) String() string {
if types.IsVoid(def.Type()) || len(def.Name()) == 0 {
return def.valInst.String()
}
return fmt.Sprintf("%s = %s", def.ValueString(), def.valInst)
}