potential for controlling memory alignment?

[Carter Schonwald]

Reid Barton was just noticing some  alignment perf issues  and talking
about it on #ghc / #haskell-llvm

probably worth documenting it in a ticket!



On Thu, Sep 12, 2013 at 3:28 PM, Nicolas Frisby <nicolas.frisby at gmail.com>wrote:

> On my laptop, a program showed a consistent slowdown with -fdicts-strict
>
> I didn't find any obvious causes in the Core differences, so I turned to
> Intel's Performance Counter Monitor for measurements. After trying a few
> counters, I eventuall saw that there are about an order of magnitude more
> misaligned memory loads with -fdicts-strict than without, so I think that
> may be a significant part of the slowdown. I'm not sure if these are code
> or data reads.
>
> Can anyone suggest how to validate this hypothesis about misaligned reads?
>
> A subsequent commit has changed the behavior I was seeing, so I'm not
> interested in alternatives means to determine if -fdicts-strict is somehow
> at fault — I'm just asking specifically about data/code memory alignment in
> GHC and how to diagnose/experiment with it.
>
> Thanks.
>
>
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