LLVM,Fail to create call instruction by LLVM IRBuilder class - llvm

Question

I want to write a simple frontend for language PL/0,the lexer and parser seems work well,but there has a bug when generating call statement LLVM IR.
Here is my code for generating IR for the PL/0 call statement: CALL ident. It fails to execute the Builder.CreateCall(F,None,"calltmp");
The console says:
pl0: /root/llvm-6.0/lib/IR/Value.cpp:247:
void llvm::Value::setNameImpl(const llvm::Twine&):
Assertion `!getType()->isVoidTy() && "Cannot assign a name to void values!"' failed.
Aborted (core dumped)
The TheModule->getFunction() gets the correct function. All functions in my implementation has function type void ..(), no return value and no argument.
I tried to debug it with gdb; it seems the instruction created by Builder.CreateCall(...) is "optimized out".
What's wrong with this?
Code for generating call statement:
bool CallStatAST::codegen()
{
auto F = TheModule->getFunction(Callee);
if(!F)
logErrorL("Failing to get function from module at CallStatAST::codegen()!\n");
//std::vector<Value*> Args;
Builder.CreateCall(F,None,"calltmp");
return true;
}
gdb debug information:
1. (gdb) break 391
Breakpoint 1 at 0x4713a5: file pl0.cpp, line 391.
2. (gdb) run < test1.pl0
Starting program: /root/my_llvm/PL0/pl0 < test1.pl0
3. Breakpoint 1, get (this=optimized out) at /usr/lib/gcc/x86_64-redhat-linux/4.8.5/../../../../include/c++/4.8.5/bits/unique_ptr.h:234
234 { return std::get<0>(_M_t); }
4. (gdb) n
CallStatAST::codegen (this=0xa165d0) at pl0.cpp:392
392 auto F = TheModule->getFunction(Callee);
5. (gdb) p F->dump()
define internal void #myfun()
{
entry:
%i = alloca double
%a = load double, double* #a
%b = load double, double* #b
%addtmp = fadd double %a, %b
store double %addtmp, double* %i
ret void
}
$1 = void
6. (gdb) p F->getName()
$2 = {static npos = 18446744073709551615, Data = 0xa17310 "myfun", Length = 5}
(gdb) n
397 Builder.CreateCall(F,None,"calltmp");
7. (gdb) s
Twine (Str=0xa17278 "\300P\241", this=optimized out) at /usr/local/include/llvm/ADT/Twine.h:270
270 LHS.cString = Str;
8. (gdb) n
CallStatAST::codegen (this=optimized out) at pl0.cpp:397
397 Builder.CreateCall(F,None,"calltmp");

Answer 1

How fool I am!
I unbelievable want to assign a name to a void return value,there does not have a value and how can set a name for it?
convert:
Builder.CreateCall(F,None,"calltmp");
to:
Builder.CreateCall(F,None);
all things work again!