<div dir="ltr">Reid Barton was just noticing some alignment perf issues and talking about it on #ghc / #haskell-llvm<div><br></div><div style>probably worth documenting it in a ticket! </div><div style><br></div></div><div class="gmail_extra">
<br><br><div class="gmail_quote">On Thu, Sep 12, 2013 at 3:28 PM, Nicolas Frisby <span dir="ltr"><<a href="mailto:nicolas.frisby@gmail.com" target="_blank">nicolas.frisby@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div dir="ltr"><div>On my laptop, a program showed a consistent slowdown with -fdicts-strict</div><div><br></div><div>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.</div>
<div><br></div><div>Can anyone suggest how to validate this hypothesis about misaligned reads?</div><div><br></div><div>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.<br>
</div><div><br></div><div><div>Thanks.<br></div><div><br></div><div></div></div>
</div>
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