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Push Ifs Up And Fors Down (matklad.github.io)

submitted 1 year ago by lysdexic@programming.dev to c/programming@programming.dev

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[–] ShaunaTheDead@kbin.social 3 points 1 year ago (11 children)

I'm curious, is there a difference in doing it like this?:

var condition = var1 &amp;&amp; var2

for walrus in walruses {
  if (condition) {
    walrus.frobnicate()
  } else {
    walrus.transmogrify()
  }
}

Doesn't assigning the condition to a variable make it so that it's only really evaluated once?

[–] pipe01@lemmy.pipe01.net 1 points 1 year ago (1 children)

You still need to read the variable in each iteration, but the cost of that is probably negligible

[–] declination@programming.dev 4 points 1 year ago* (last edited 1 year ago)

Modern optimizing compilers are magical. I would need to check assembly but I would actually expect the if to be hoisted out of the loop entirely to relieve pressure on the branch predictor.

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