Messages in this thread | | | From | Denys Vlasenko <> | Subject | Re: [PATCH v2 0/4] Add support for compiling with -ffunction-sections -fdata-sections | Date | Tue, 21 Apr 2009 03:05:03 +0200 |
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On Tuesday 21 April 2009 01:40, Linus Torvalds wrote: > Quite frankly, every time I see something like this, I shudder. > > Why? > > The bugs in the toolchains tend to be infinite and _really_ annoying.
Most bugs are annoying. :)
> We'll end up with everything from "gcc-xyz cannot handle it" to > "binutils-abc which was pre-released by RH/Ubuntu/SUSE will SIGSEGV". > > And those are the _good_ cases. The bad cases are just silently > miscompiled/linked stuff under certain circumstances. > > In other words, I'm not going to merge it without a _lot_ of people > pushing me on it with nice numbers etc. Because I absolutely hate the > tools issues that I'm convinced will happen the moment I merge it.
In some cases, section garbage collection discards nearly 10% of dead code/data from kernel image. Actually, every time I add it to a software project, I see quite an amount of dead code/data eliminated. Even sadistic manual splitting of every function and data object into its own .o file doesn't match it.
I can put it another way: let machine do what it does better, and faster, than humans ever can:
I was pushing a patch for aic7xxx driver which eliminated ~150k of dead code. It took a lot of time to eventually make it reach mainline kernel. On and off, it took years.
With section garbage collection, that patch would not be even needed, as gcc+ld would automagically detect that that code is dead. -- vda
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