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Re: [Patch] 1/3 Add new builtin __builtin_flush_icache().
Mark Mitchell wrote:
Paolo Bonzini wrote:I agree and had arrived at the same conclusion for your first two points.
1) Rename the new builtin to __builtin_clear_cache (char *beg , char(And use libgcc's prototype). This would be the cleanest.
*end), and have it call the function in libgcc if there is not an
inline expansion for it?
This, plus, try to see how __clear_cache could use the definition of the
Paolo, I didn't quite follow your suggestion. So, I'm not sure if I'm
agreeing or disagreeing. :-)
Anyhow, here's my suggestion.
1. The builtin should be:
__builtin___clear_cache (char *beg, char *end)
following the standard convention that the builtin for X is __builtin_X.
2. The default implementation of the builtin should be to call
__clear_cache. That means that users can call __builtin_clear_cache
from their code, on all platforms.
My current idea for this can, I think,,be best expressed by looking at
the proposed code for libgcc:
3. Targets which can do something clever can implement the builtin as
they please and can define CLEAR_INSN_CACHE(BEG, END) to expand to
__builtin_clear_cache(BEG, END). On such targets, then, __clear_cache
in libgcc will call the builtin, which we can be assured will not
recursively expand to __clear_cache.
__clear_cache (char *beg, char *end)
__builtin___clear_cache (beg, end);
CLEAR_INSN_CACHE (beg, end);
#endif /* CLEAR_INSN_CACHE */
No changes to any existing CLEAR_INSN_CACHE definitions are needed.
There is a new target hook that determines the value of
__builtin_clear_cache_inline_p(). I chose to do it this way because I
think it would be impossible to reliably determine if the
__builtin___clear_cache would expand in-line without such a predicate.
A revised patch is in the works.