What Challenges and Trade-Offs Do Optimising Compilers Face?

Re:What Challenges and Trade-Offs Do Optimising Compilers Face? by greglindahl on Thursday June 22, 2017 @02:51PM (#14614404)

The problem with directives is not on day 1, they're awesome on day 1. The problem is usually that the directives are in the wrong place 10 years later.

Loop unrolling directives went through that process in just a few years, from giving a nice speedup, to compilers being able to mostly match the directive, to the directive causing slowdowns, to compilers ignoring that directive.

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Re:What Challenges and Trade-Offs Do Optimising Compilers Face? by fao_ on Thursday June 22, 2017 @08:04PM (#14616221)

... at which point you can edit a single point in the source code to fix it, either defining hot-path to be equivalent to eval, removing it outright, or altering it to be better. Isn't that the point of abstraction?

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Re:What Challenges and Trade-Offs Do Optimising Compilers Face? by moomin on Friday June 23, 2017 @02:51AM (#14617429)

A misplaced directive is probably preferable to misplaced manual optimisation, though.

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