Paul E. McKenney wrote:
> > Does some version of gcc, under the options which we insist upon,
> > make such optimizations on any of the architectures which we support?
>
> Pretty much any production-quality compiler will do double-fetch
> and old-value-reuse optimizations, the former especially on 32-bit
> x86. I don't know of any production-quality compilers that do value
> speculation, which would make the compiler act like DEC Alpha hardware,
> and I would hope that if this does appear, (1) we would have warning
> and (2) it could be turned off. But there has been a lot of work on
> this topic, so we would be foolish to rule it out.
GCC documentation for IA-64:
-msched-ar-data-spec
-mno-sched-ar-data-spec
(En/Dis)able data speculative scheduling after reload. This results
in generation of ld.a instructions and the corresponding check
instructions (ld.c / chk.a). The default is 'enable'.
I don't know if that results in value speculation of the relevant kind.
-- Jamie
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