Generated by SassMeister.com.

SassMeister-input-HTML.html

<div class="test">test</div>
<div class="test1">test 1</div>
<div class="test2">test 2</div>
<div class="test3">test 3</div>
<div class="test4">test 4</div>

SassMeister-input.scss

// ----
// Sass (v3.3.14)
// Compass (v1.0.1)
// ----

// THE SELF-AWARE MIXIN

// define global map to store info about this mixin
$my-mixin-info: ();

// define mixin with any format of arguments
@mixin my-mixin($pos1, $pos2, $map: (), $rest...) {

  // capture some or all of the arguments,
  // according to whatever repetitions you want to avoid
  $my-args: ($pos1, $pos2, $map);

  // look up these arguments as a key in the global map
  $id: map-get($my-mixin-info, $my-args);

  // if they return an 'ID'...
  @if $id { 

    // extend that ID
    @extend %#{$id}; 

    // output any specific stuff
    specific: inspect($rest);
  }

  // otherwise...
  @else {

    // create the ID
    $id: unique-id();

    // merge the ID in to the mixin's map against the ARGS
    $my-mixin-info: map-merge($my-mixin-info, ($my-args: $id)) !global;

    // create a placeholder named after the ID at root
    @at-root {
      %#{$id} {

        // output the stuff you want to not repeat
        common: inspect($my-args);
      }    
    }

    // extend that placeholder
    @extend %#{$id};

    // output any specific stuff
    specific: inspect($rest);
  }
}

.test {
  @include my-mixin(1, 2, (), 4, 5);
}

.test2 {
  @include my-mixin(1, 2);
}

.test3 {
  @include my-mixin(1, 2, (), 6, 7);
}

SassMeister-output.css

.test {
  specific: 4, 5;
}
.test, .test2, .test3 {
  common: 1, 2, ();
}

.test2 {
  specific: ();
}

.test3 {
  specific: 6, 7;
}

SassMeister-rendered.html

<div class="test">test</div>
<div class="test1">test 1</div>
<div class="test2">test 2</div>
<div class="test3">test 3</div>
<div class="test4">test 4</div>