Re: panic during make depend
At 11:01 PM 3/15/00 -0500, Donn Miller wrote: >Sounds like one of those nasty gcc optimization bugs. I generally >build my kernel and world with -mpentium -O3 -pipe, and I haven't seen >any bugs at all. I build everything with these flags without >problems. The only problems I've see, as mentioned previously, was in >building Qt. I've gotten an "Internal compiler error" with those >flags, but reverting to what Troll put in qt/configs solved the >problems. Apparently, there's both compile-time and run-time bugs >with gcc's opt. code. It might be, but I'm backing off from -02 to -O for a dozen builds or so and see. Less if panics keep coming, then the -march will be dropped. All good then back to -02 and try -mcpu. >I think there are some bugs with the pentium-specific flags in gcc, >excluding the generic-pentium flag of -mpentium. I would try using >-mpentium -O3 -pipe --- I'm pretty confident that will solve your >problems, and you can still get generic pentium optimization levels. Why use -O3, which adds -finline-functions. AFAICR, that one isn't very liked by those more with more knowledge and experience. >Of course, I don't really know if there's anything to be gained by >using these flags over the stock -O -pipe -- but I do it anyways for >the psychological reassurance (placebo effect). I definitely think >building XFree86 with pentium opt. is a great idea. But with >buildworld and buildkernel, my advice would be to just use -mpentium, >as it's probably the "happiest medium" between pentium opt. and >stability. From what I've heard, compiling mission critical stuff >with -mpentiumpro is a bad idea. Hmmm... didn't -mpentiumpro come >from pgcc? I think the best place to use -mpentiumpro is in compiling >multimedia type stuff, where stability isn't important but speed is. Don't think your reasoning is all that sound as a "reassurance," but ensuring that code is optimized for the CPU, and in my case architecture, is good. Originally thought that using -march would speed up compiling for one and another to have more specific code for the system running it. Been a while since I had a running 486, 8+ years since even seeing a 386, and only have 2 pentiums in operation, so why should the code have instructions for running on any of these platforms? As an example I've seen many posts with -mno-486 used. The man page is clear as mud on what that does. From the wording it should optimize the code for a 386 then: -mno-486 Control whether or not code is optimized for a 486 instead of an 386. Code generated for a 486 will run on a 386 and vice versa. Perhaps the man pages need updating. >Basically, gcc is a very good compiler. But, it isn't exactly the >best compiler to use for optimization. Someone told me that Sun's and >DEC's compilers, for example, blow away gcc in terms of speed. But, >they aren't portable. The DEC compiler might be good for some FBSD users. Jeff Mountin - [EMAIL PROTECTED] Systems/Network Administrator FreeBSD - the power to serve To Unsubscribe: send mail to [EMAIL PROTECTED] with "unsubscribe freebsd-current" in the body of the message
Re: panic during make depend
On 2000-Mar-16 15:04:00 +1100, Donn Miller <[EMAIL PROTECTED]> wrote: >Basically, gcc is a very good compiler. But, it isn't exactly the >best compiler to use for optimization. Someone told me that Sun's and >DEC's compilers, for example, blow away gcc in terms of speed. But, >they aren't portable. I think it's very dependent on the target architecture and how popular that architecture is. Traditionally, the M68K and SPARC families were the most popular, and gcc generated the best (or equal best) code on them. The i386 is now a more popular family but, at the high end, optimisation is restricted by the difficulty of obtaining accurate documentation. The Alpha is a very difficult processor to generate good code for (and I suspect the IA64 will be worse). DEC (and now Compaq) have put a lot of effort into tweaking their compiler - I don't believe anything like the same amount of effort has been expended on the gcc backend (and I wouldn't expect it). Peter To Unsubscribe: send mail to [EMAIL PROTECTED] with "unsubscribe freebsd-current" in the body of the message
Re: panic during make depend
"Jeffrey J. Mountin" wrote: > Successfully did a buildworld with -O -pipe -march=pentiumpro, installworld > was good, remade /dev and built a generic kernel. Config'd my local kernel > and within the first few lines of 'make depend' it bombed: Sounds like one of those nasty gcc optimization bugs. I generally build my kernel and world with -mpentium -O3 -pipe, and I haven't seen any bugs at all. I build everything with these flags without problems. The only problems I've see, as mentioned previously, was in building Qt. I've gotten an "Internal compiler error" with those flags, but reverting to what Troll put in qt/configs solved the problems. Apparently, there's both compile-time and run-time bugs with gcc's opt. code. I think there are some bugs with the pentium-specific flags in gcc, excluding the generic-pentium flag of -mpentium. I would try using -mpentium -O3 -pipe --- I'm pretty confident that will solve your problems, and you can still get generic pentium optimization levels. Of course, I don't really know if there's anything to be gained by using these flags over the stock -O -pipe -- but I do it anyways for the psychological reassurance (placebo effect). I definitely think building XFree86 with pentium opt. is a great idea. But with buildworld and buildkernel, my advice would be to just use -mpentium, as it's probably the "happiest medium" between pentium opt. and stability. From what I've heard, compiling mission critical stuff with -mpentiumpro is a bad idea. Hmmm... didn't -mpentiumpro come from pgcc? I think the best place to use -mpentiumpro is in compiling multimedia type stuff, where stability isn't important but speed is. Basically, gcc is a very good compiler. But, it isn't exactly the best compiler to use for optimization. Someone told me that Sun's and DEC's compilers, for example, blow away gcc in terms of speed. But, they aren't portable. - Donn To Unsubscribe: send mail to [EMAIL PROTECTED] with "unsubscribe freebsd-current" in the body of the message
