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). ------ Sergey