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Re: [v3] conditional tweak
Martin Sebor <sebor@roguewave.com> writes:
| Gabriel Dos Reis wrote:
|
| ...
| > | While I haven't measured Jerry's particular patch, on machines with deep
| > | pipelines, an incorrectly-predicted branch can be a significant stall
| > | (most/all of the pipeline has to be cleared).
| > In theory, yes. In this particular case, we're speaking of an I/O
| > formatting flag setting which is nowhere a bottleneck (expect probably
| > in a testsuite).
|
| This conditional actually does happen to have a significant impact
| on performance -- fill() is called every time a number is inserted
| into a stream, for example.
compared to the actual work for formatting?
| Incidentally, I recently profiled the effect of the HP aCC $pragma
| ESTIMATED_FREQUENCY (the rough equivalent of gcc's __builtin_expect)
| on IPF (i.e., IA64). IIRC, the improvement was between 5 and 10% for
| a small block of code.
I have no idea of how HP aCC $pragma works. Can you display the actual
work or is it covered by proprietary rules?
-- Gaby