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Re: msp430 port


> I'd say it's not as simple as you make it out to be.  You can't blindly 
> combine operations on volatile memory.

I'm not blindly combining them, I'm combining them when I know the
hardware will do the volatile-correct thing.

> ie, the programmer may have written them as separate statements and
> if they're volatile you should leave them alone.

Most of the programmers I know would expect "port |= 0x80;" to do a
hardware-specific "set bits" operation, not a series of
volatile-pedantic operations, especially when the ISA has a set of
insns specifically designed to do bit operations on volatile I/O
registers.

> With this change a series of statements involving 
> volatiles might be combined into a single insn.  That's not good.

If the insn does exactly the same thing as the operations, just
faster, why is it not good?

> I'll note that *NO* ports in the official GCC sources do this and that's 
> because it's wrong.

m32c, rl78, and sh do this (to varying degrees) in the official
sources.


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