https://d.puremagic.com/issues/show_bug.cgi?id=11506
[email protected] changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |[email protected] --- Comment #2 from [email protected] 2013-11-12 15:26:47 PST --- (In reply to comment #0) > Also: > > pure int fun(); > > int main(string[] args) > { > return fun() + fun(); > } > > This program doesn't link, but the generated code reveals that fun() is called > twice. It should only called once. If I compile this code with: dmd -O -release -noboundscheeck temp.d int fun() pure nothrow { return 0; } int main() { return fun + fun; } It contains only one call to fun (and add EAX,EAX doubles its result): _D4temp3funFNaNbZi: xor EAX,EAX ret __Dmain: L0: push EAX call near ptr _D4temp3funFNaNbZi add EAX,EAX pop ECX ret ------------------------ But if I remove the nothrow: int fun() pure { return 0; } int main() { return fun + fun; } It shows both calls to fun: _D4temp3funFNaZi: xor EAX,EAX ret __Dmain: L0: push EAX call near ptr _D4temp3funFNaZi push EAX sub ESP,4 call near ptr _D4temp3funFNaZi add ESP,4 mov ECX,EAX pop EAX add EAX,ECX pop ECX ret The ability to throw is an effect (a side effect) and it can't be ignored. On the other hand fun takes no arguments, so I think the two calls to fun fun can't decide to throw or not throw independently. So I think calling fun only once is OK even if it doesn't have a nothrow annotation. On the other hand two calls to a a function foo like this: int foo(in size_t x) pure { if (x & 1) throw new Exception(""); return 10; } int main(in string[] args) { return fun(args.length) + fun(args.length); } Can't be replaced with a single call. -- Configure issuemail: https://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
