[PATCH] D21698: [OpenCL] Allow disabling types and declarations associated with extensions

[Anastasia Stulova via cfe-commits]

Anastasia added a comment.

In https://reviews.llvm.org/D21698#546733, @yaxunl wrote:

> In https://reviews.llvm.org/D21698#540237, @Anastasia wrote:
>
> > I have made an experiment with a simple kernel:
> >
> >   void foo1(void);
> >   void foo2(void);
> >   void foo3(void);
> >   void foo4(void);
> >   void foo5(void);
> >   void foo6(void);
> >   void foo7(void);
> >   void foo8(void);
> >   void foo9(void);
> >   void foo10(void);
> >  
> >   void test(){
> >     foo1();
> >     foo2();
> >     foo3();
> >     foo4();
> >     foo5();
> >     foo6();
> >     foo7();
> >     foo8();
> >     foo9();
> >     foo10();
> >   }
> >   
> >
> > I am using time utility of linux to measure the compile time running Clang in CL2.0 mode and average over 100 samples. It shows me around 7% overhead with your approach.
>
>
> Since the program is very small, it is difficult to measure the compilation time accurately. I compile the program 1000 times and measure its time in a script:
>
>    $ cat run.sh
>    run() {
>    i=1
>    while [[ $i -le 1000 ]]; do
>      ./$1 -cc1 -emit-llvm tmp.cl
>      i=$((i+1))
>    done
>    }
>   
>   time -p run $1
>    
>
>
> Even so, I found large variations in the measured compilation time. I ran the script 10 times for clang before my change and I got the real time
>
>   real 8.96
>   real 9.01
>   real 8.99
>   real 9.07
>   real 9.03
>   real 8.99
>   real 9.03
>   real 9.01
>   real 8.99
>   real 9.01
>  
>
>
> and the average time is 9.009s.
>
> For clang after my change, I got
>
>   real 9.06
>   real 9.09
>   real 9.10
>   real 9.03
>   real 9.05
>   real 9.17
>   real 9.08
>   real 9.08
>   real 9.07
>   real 9.08
>  
>
>
> And the average time is 9.081s.
>
> The increase of compilation time is 0.8%. Considering this program consists mostly of function declarations, which emphasized the cost of evaluating disabled function declarations unrealistically. In real programs this increment in compilation time should be even smaller.
>
> Since the increment of compilation time is less than 1% even for exaggerated cases, I think it is reasonable to accept the cost for the improved diagnostics for extensions.
>
> If there are concerns that the newly added diagnostics may break applications which use builtin functions associated with an extension without enabling it, we can make the diagnostic msg a warning which can be turned off.


Ok. Sure. I will profile a few more benchmarks and let you know.


https://reviews.llvm.org/D21698