On 02/11/2011 07:53 AM, so wrote:
While in isolation that's a good idea, how far should it be taken? Should the
compiler emit information on which variables wound up in which registers, and
why? What about other of the myriad of compiler optimizations?
Isn't Inlining by far the most important (most practical) optimization among
those that actually we can control?
A few times i have seen comparisons here to similar languages and in most of
them the inlining was the reason (only) for the inferior performance.
I agree it would be awesome if the compilers had the ability to chose the best
method, but comparisons show sometimes the opposite, i don't know maybe they
are hand-picked for some reason.
I recently read a study using a dozen test cases to compare optimisations
performed by 3 C compiler (IIRC: gcc, a win product, and an LLVM one). Very
instructive, and even more surprising for me.
In every case, some optimsation was done by a compiler that others did not, or
conversely. This let me think for a while... how come? Don't compiler authors
know, more or less, what kinds or optimisation "tactics" *exist* in given
situations? and thus are performed by others. Strange. If this is the case,
then the world of programming definitely needs a public knowledge base
dedicated to compiler technique, esp. on optimisation. A wiki, indeed.
denis
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