sharpneli

Disabling optimizations produce faster code

Discussion created by sharpneli on Oct 3, 2011
Latest reply on Oct 4, 2011 by genaganna
Compiler seems to be too clever for it's own good in some cases

As shown by actual tests and the APP KernelAnalyzer in some cases disabling optimizations by -cl-opt-disable can produce much faster code.

As an example we have a kernel which has 181 ALU inst and 83 fetches with 44 writes. This is regardless of the added optimization flags. With -cl-opt-disable there are 48 ALU insts, 7 fetches and 6 writes. Benchmarked throughput and the estimated troughput are both approximately double of the 'optimized version'.

It seems the compiler does no sanity checks for the actual benefit of optimization passes it performs. I presume this will be improved in the future?

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