Re: Optimizing empty functions in C

> When processing (the machine code resulting from) this code, our
> optimizer inlined the call to GC_noop(), then eliminated the
> dereference operation "*result" that evaluated the argument after
> inferring that it was unnecessary since it was not used.


This was once a common defect in many optimizers. About six years
ago, I analyzed twenty C compilers using many different types of loop
constructs with a volatile reference. Twelve of the compilers
incorrectly hoisted a volatile reference out of the loop for one or
more of the loop constructs. Some of the compilers were sensitive to
a particalur loop construct and data type. A collection of volatile
tests were added to the NULLSTONE suite to catch these defects using a
mechanism to update the value independent of the loop. This defect
appears to be less common today.


Best,
Christopher
http://www.nullstone.com/

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