#2609: Compiling with -O2 is 7x slower than -O
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Reporter: simonpj | Owner:
Type: compile-time performance bug | Status: new
Priority: normal | Milestone:
Component: Compiler | Version: 6.8.3
Severity: normal | Resolution:
Keywords: | Difficulty: Unknown
Testcase: | Architecture: Unknown
Os: Unknown |
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Comment (by simonpj):
Ah, this seems to be to do with `-fviaC` ''not'' to do with `-O2`. Serge
writes:
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).
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/2609#comment:1>
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