Re: Optimisation possibilities: current, future and enhancements

[Cecil Ward via Digitalmars-d]

On Thursday, 25 August 2016 at 17:22:27 UTC, kinke wrote:
I found it hard to believe LDC generates such crappy code when 
optimizing. These are my results using LDC master on Win64 
(`ldc2 -O -release -output-s`):

struct Foo
{
    immutable _u = 8;
    int foo() const
    {
        return 8 * _u;
    }
}
int use(ref const(Foo) foo)
{
    return foo.foo() + foo.foo();
}

int main()
{
    Foo f;
    return use(f);
}


_D7current3Foo3fooMxFZi:
        movl    (%rcx), %eax
        shll    $3, %eax
        retq

_D7current3useFKxS7current3FooZi:
        movl    (%rcx), %eax
        shll    $4, %eax
        retq

_Dmain:
        movl    $128, %eax
        retq

Sure, Foo.foo() and use() could return a constant, but 
otherwise it can't get much better than this.

I think that here the optimisation is only because LDC can “see” 
the text of the method. When expansion is not possible, that 
would be the real test.