[Bug gas/9782] Additional switches to disallow processor supplementary instructions

[markhobley at yahoo dot co dot uk]

------- Additional Comments From markhobley at yahoo dot co dot uk  2009-01-27 
00:47 -------
Subject: Re:  Additional switches to disallow processor supplementary 
instructions

> You can't disable an instruction at configure time.
> However,
> you can select an instruction set based on CPUID:

Right. I don't like the cpuid idea at all. This means that code can behave one 
way on one machine, but do something different on the other, due to branches in 
the code. It also means that code is bulky because it carries redundant 
branches, and requires extra testing, because all branches have to be tested.

Also, you may not be building for the machine that you have just cpuid.

For example, I share binaries across the network with different machines, and 
some of the cpus return a different ident. This is bad!

Especially at this time, because some machines crash due to invalid 
instructions.

It would be better to allow the system builder to choose the instruction set 
for the machine at compile time, rather than making such decisions at runtime.





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http://sourceware.org/bugzilla/show_bug.cgi?id=9782

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