Messages in this thread | | | Date | Wed, 21 Nov 2001 15:15:55 +0300 | From | Ivan Kokshaysky <> | Subject | Re: [alpha] cleanup opDEC workaround |
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On Tue, Nov 20, 2001 at 10:47:48AM -0800, Richard Henderson wrote: > In the working case, we'll enter entIF with pc==cmpteq. Add 8 gives > stt, subtract 4 gives addt, which is engineered to be a noop.
Argh. I was thinking too much about dummy_emul case and missed the fact that instruction at pc-4 is actually executed in alpha_fp_emul()...
> Hmm. If fp emulation isn't compiled in, we shouldn't bother > testing this, I think. Means you can't debug fp emulation via > modules on Multia, but I'm pretty sure I don't care.
Yes, making opDEC_check stuff `#ifdef CONFIG_MATHEMU' would be reasonable.
> I suppose the other alternative to get the testing code out of > the normal entIF is to create a custom entIF that is installed > only during opDEC testing. Seems too much work...
Agreed. Alternatively, it's possible to hack dummy_emul(), which doesn't affect the normal case.
static long dummy_emul(unsigned long pc) { if (opDEC_fix != 8) return 0; /* Trap in opDEC_check() */ if (*(u32 *)pc == 0x5bff141f) /* addt $f31, $f31, $f31 */ return 1; /* SRM updates PC correctly */ /* Broken SRM. "Emulate" cmpteq in opDEC_check() */ __asm__ __volatile__("cmpteq $f31, $f31, $f0\n"); return 1; }
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