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On 9/1/00, 11:45:23 AM, "Christopher C. Chimelis" <[EMAIL PROTECTED]> wrote regarding Aha!: > Found out something interesting. I was trying to figure out why > gcc/fold-const.c wouldn't assemble properly and found a set of > command-line options where it would. > Some background, I decided to add '-save-temps -v' to gcc's options while > compiling. What it showed command-wise was exactly what I expected, so > I'll omit that stuff. I then tried hand-running gas with the options that > gcc was passing it on fold-const.s. Here's the errors I got: > # as -EB -v -KPIC -o fold-const.o fold-const.s > fold-const.s: Assembler messages: > fold-const.s:27290: Error: Branch out of range > fold-const.s:27329: Error: Branch out of range > fold-const.s:27334: Error: Branch out of range > fold-const.s:28748: Error: Branch out of range > fold-const.s:28861: Error: Branch out of range > Ok, I tried a few things including looking directly at the assembly > generated by cc1 (despite not having any MIPS asm references around, it > looked ok...looks like it was supposed to be using jumps to the branches > that gas was saying was out of range). > I then hit the gas docs and tried various MIPS-specific options with > eventual success. Turns out that adding any of the -mips? options other > than -mips1 allows it to assemble correctly. For the uninformed, here's a > breakdown on those options: > -mips1 = generates code for the R2000 and R3000 processors > -mips2 = generates code for the R6000 processor > -mips3 = generates code for the R4000 processor > -mips4 = generates code for the R8000 and R10000 processors > It seems that, when binutils is configured for the mips-unknown-linux-gnu > target, it assumes that -mips1 is the default, apparently. This is > probably for maximum compatibility. Since I don't have any reference > manuals on the generations of MIPS processors, I don't really know the > differences yet between all of these families, but it appears that, either > the R2000/R3000 processors cannot handle these specific jumps for some > reason OR (most likely) there is a bug in binutils wrt -mips1 support. > Can someone educate me on the differences between the families of > MIPS processors or point me towards some technical docs? I can probably > isolate this problem in binutils if I had more to work with. Also, this > may turn up a bug in gcc as well (who knows at this point...I'm too new to > this arch to really know what may be involved). In the meantime, I'm > going to see if I can target binutils and gcc towards the R4x00 that's in > this indy and go from there. The mips1/2/3/4 are different mips instruction set architectures. Processors that are mips4 compliant, for example, also have instruction compatibility with the previous architectures -- mips1/2/3. Thus, mips3 doesn't mean R4000, but the R4000 might be a mips3 cpu (the 5000 is mips4). It would be nice to get gcc/binutils fixed for all ISAs, but if you have to target a certain ISA, start with mips3. Most newer processor are either mips3 or mips4 cpus, so that would be of the most benefit to mips-linux, imho. If you're interested in mips in general, the best book out there, in my opinion, is 'See Mips Run' by Dominic Sweetman. Pete
