testing ghc-6.10-candidate

Serge D. Mechveliani mechvel at botik.ru
Sat Sep 20 08:06:59 EDT 2008

On Sat, Sep 20, 2008 at 11:25:57AM +0100, Simon Marlow wrote:
> Serge D. Mechveliani wrote:
> >5. The same is for -O2. But this does not gain more performance.
> >   -O2 -fvia-C  also does not gain more performance, but leads to 7 times 
> >   longer compilation.
> Just to be sure: are you saying that with -O2 the compile time is ok, 
> but when you add -fvia-C it takes 7 times longer?  If so, it's probably 
> not a bug (we don't have any control over the speed of gcc).  Here's the 
> bug report:
> http://hackage.haskell.org/trac/ghc/ticket/2609
> Sergey, could you clarify please?

With  -O2,  the compile time is ok, but when I add  -fvia-C,  it takes 7 
times longer 
-- this is for  ghc-6.9-earlySeptember  to compile  DoCon-2.12-pre.

You do not control over the speed of  gcc  itself. But a small change in 
the GHC compiler may, in principle, lead to many times faster compilation
by  gcc  of the code produced by GHC. This may occur some problem in GHC
as well as some problem in gcc.

This is only my observation, I do not pretend for a bug report in this 
case. I tried  -fvia-C  for curiosity: 
"by occasion, would it increase the code performance?". 
If this ratio of 7 looks curious to you, you could investigate this.

And personally, I am satisfied with  -O (without via-C).


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