[fpc-devel] Found compiler bug while working on Deep Optimiser

Sven Barth pascaldragon at googlemail.com
Sun May 27 09:31:22 CEST 2018

Am 27.05.2018 um 02:48 schrieb J. Gareth Moreton:
> Hi guys,
> So I'm still experimenting and researching with the deep optimiser, 
> and I'm starting to have some successes... until I found a compiler bug!
> https://bugs.freepascal.org/view.php?id=33794
> What I'm trying to do, and something which I'd like to try out with 
> the regular peephole optimiser at some point, is using a sorted list 
> that maps an assembler command to a handler procedure and using a 
> binary search to find the correct routine.  This will speed up the 
> optimiser from O(n) (i.e. the speed of "case X of") to O(log n) per 
> line of code, where n is the different number of assembler commands it 
> has to deal with, but the compiler produces incorrect code with the 
> algorithm I'm using, and triggers an internal error if -O3 is 
> specified.  A trimmed down sample project is attached with the ticket.
> Even if the deep optimiser is an unstable, unusable failure, I found a 
> bug anyway!

Yes, you found a bug... in your own code. See my note at the bug report.

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