Re: How to defeat the optimizer in GDC

[Iain Buclaw via D.gnu]

On Monday, 20 May 2019 at 08:11:19 UTC, Mike Franklin wrote:
I'm trying to benchmark some code, but the optimizer is 
basically removing all of it, so I'm benchmarking nothing.

I'd like to do something like what Chandler Carruth does here 
to defeat the optimizer:  
https://www.youtube.com/watch?v=nXaxk27zwlk&feature=youtu.be&t=2446

Here presents the following inline asm function to tell the 
optimizer that `p` is being used (at least that's how I 
understand it):
```
void escape(void* p)
{
    asm volatile("" : : "g"(p) : memory);
}
```

I tried to do the same thing in D with this function:
```
void use(void* p)
{
    version(LDC)
    {
        import ldc.llvmasm;
         __asm("", "r,~{memory}", p);
    }
    version(GDC)
    {
        asm { "" : : "g"(p), "memory"; }
    }
}
```

The LDC version seems to work fine:  
https://d.godbolt.org/z/qbg54J

But I can't get GDC to do the same:  
https://explore.dgnu.org/z/quCjhU

Is this currently possible in GDC?


Looks like you've done a typo to me. Memory should be a clobber, 
not an input operand.

--
Iain