html/041jump_target.cc.html


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<span class="Comment">//: Support jumps to special labels called 'targets'. Targets must be in the</span>
<span class="Comment">//: same recipe as the jump, and must be unique in that recipe. Targets always</span>
<span class="Comment">//: start with a '+'.</span>
<span class="Comment">//:</span>
<span class="Comment">//: We'll also treat 'break' and 'loop' as jumps. The choice of name is</span>
<span class="Comment">//: just documentation about intent; use 'break' to indicate you're exiting</span>
<span class="Comment">//: one or more loop nests, and 'loop' to indicate you're skipping to the next</span>
<span class="Comment">//: iteration of some containing loop nest.</span>

<span class="Delimiter">:(scenario jump_to_label)</span>
def main [
  jump +target:label
  <span class="Constant">1</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
  +target
]
<span class="traceAbsent">-mem: storing 0 in location 1</span>

<span class="Delimiter">:(before &quot;End Mu Types Initialization&quot;)</span>
put<span class="Delimiter">(</span>Type_ordinal<span class="Delimiter">,</span> <span class="Constant">&quot;label&quot;</span><span class="Delimiter">,</span> <span class="Constant">0</span><span class="Delimiter">);</span>

<span class="Delimiter">:(before &quot;End Instruction Modifying Transforms&quot;)</span>
Transform<span class="Delimiter">.</span>push_back<span class="Delimiter">(</span>transform_labels<span class="Delimiter">);</span>  <span class="Comment">// idempotent</span>

<span class="Delimiter">:(code)</span>
<span class="Normal">void</span> transform_labels<span class="Delimiter">(</span><span class="Normal">const</span> recipe_ordinal r<span class="Delimiter">)</span> <span class="Delimiter">{</span>
  map&lt;string<span class="Delimiter">,</span> <span class="Normal">int</span>&gt; offset<span class="Delimiter">;</span>
  <span class="Normal">for</span> <span class="Delimiter">(</span><span class="Normal">int</span> i = <span class="Constant">0</span><span class="Delimiter">;</span> i &lt; SIZE<span class="Delimiter">(</span>get<span class="Delimiter">(</span>Recipe<span class="Delimiter">,</span> r<span class="Delimiter">).</span>steps<span class="Delimiter">);</span> ++i<span class="Delimiter">)</span> <span class="Delimiter">{</span>
    <span class="Normal">const</span> instruction&amp; inst = get<span class="Delimiter">(</span>Recipe<span class="Delimiter">,</span> r<span class="Delimiter">).</span>steps<span class="Delimiter">.</span>at<span class="Delimiter">(</span>i<span class="Delimiter">);</span>
    <span class="Normal">if</span> <span class="Delimiter">(</span>!inst<span class="Delimiter">.</span>label<span class="Delimiter">.</span>empty<span class="Delimiter">()</span> &amp;&amp; inst<span class="Delimiter">.</span>label<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">)</span> == <span class="Constant">'+'</span><span class="Delimiter">)</span> <span class="Delimiter">{</span>
      <span class="Normal">if</span> <span class="Delimiter">(</span>!contains_key<span class="Delimiter">(</span>offset<span class="Delimiter">,</span> inst<span class="Delimiter">.</span>label<span class="Delimiter">))</span> <span class="Delimiter">{</span>
        put<span class="Delimiter">(</span>offset<span class="Delimiter">,</span> inst<span class="Delimiter">.</span>label<span class="Delimiter">,</span> i<span class="Delimiter">);</span>
      <span class="Delimiter">}</span>
      <span class="Normal">else</span> <span class="Delimiter">{</span>
        raise &lt;&lt; maybe<span class="Delimiter">(</span>get<span class="Delimiter">(</span>Recipe<span class="Delimiter">,</span> r<span class="Delimiter">).</span>name<span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;duplicate label '&quot;</span> &lt;&lt; inst<span class="Delimiter">.</span>label &lt;&lt; <span class="Constant">&quot;'&quot;</span> &lt;&lt; end<span class="Delimiter">();</span>
        <span class="Comment">// have all jumps skip some random but noticeable and deterministic amount of code</span>
        put<span class="Delimiter">(</span>offset<span class="Delimiter">,</span> inst<span class="Delimiter">.</span>label<span class="Delimiter">,</span> <span class="Constant">9999</span><span class="Delimiter">);</span>
      <span class="Delimiter">}</span>
    <span class="Delimiter">}</span>
  <span class="Delimiter">}</span>
  <span class="Normal">for</span> <span class="Delimiter">(</span><span class="Normal">int</span> i = <span class="Constant">0</span><span class="Delimiter">;</span> i &lt; SIZE<span class="Delimiter">(</span>get<span class="Delimiter">(</span>Recipe<span class="Delimiter">,</span> r<span class="Delimiter">).</span>steps<span class="Delimiter">);</span> ++i<span class="Delimiter">)</span> <span class="Delimiter">{</span>
    instruction&amp; inst = get<span class="Delimiter">(</span>Recipe<span class="Delimiter">,</span> r<span class="Delimiter">).</span>steps<span class="Delimiter">.</span>at<span class="Delimiter">(</span>i<span class="Delimiter">);</span>
    <span class="Normal">if</span> <span class="Delimiter">(</span>inst<span class="Delimiter">.</span>name == <span class="Constant">&quot;jump&quot;</span><span class="Delimiter">)</span> <span class="Delimiter">{</span>
      <span class="Normal">if</span> <span class="Delimiter">(</span>inst<span class="Delimiter">.</span>ingredients<span class="Delimiter">.</span>empty<span class="Delimiter">())</span> <span class="Delimiter">{</span>
        raise &lt;&lt; maybe<span class="Delimiter">(</span>get<span class="Delimiter">(</span>Recipe<span class="Delimiter">,</span> r<span class="Delimiter">).</span>name<span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;'jump' expects an ingredient but got none</span><span class="cSpecial">\n</span><span class="Constant">&quot;</span> &lt;&lt; end<span class="Delimiter">();</span>
        <span class="Identifier">return</span><span class="Delimiter">;</span>
      <span class="Delimiter">}</span>
      replace_offset<span class="Delimiter">(</span>inst<span class="Delimiter">.</span>ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">),</span> offset<span class="Delimiter">,</span> i<span class="Delimiter">,</span> r<span class="Delimiter">);</span>
    <span class="Delimiter">}</span>
    <span class="Normal">if</span> <span class="Delimiter">(</span>inst<span class="Delimiter">.</span>name == <span class="Constant">&quot;jump-if&quot;</span> || inst<span class="Delimiter">.</span>name == <span class="Constant">&quot;jump-unless&quot;</span><span class="Delimiter">)</span> <span class="Delimiter">{</span>
      <span class="Normal">if</span> <span class="Delimiter">(</span>SIZE<span class="Delimiter">(</span>inst<span class="Delimiter">.</span>ingredients<span class="Delimiter">)</span> &lt; <span class="Constant">2</span><span class="Delimiter">)</span> <span class="Delimiter">{</span>
        raise &lt;&lt; maybe<span class="Delimiter">(</span>get<span class="Delimiter">(</span>Recipe<span class="Delimiter">,</span> r<span class="Delimiter">).</span>name<span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;'&quot;</span> &lt;&lt; inst<span class="Delimiter">.</span>name &lt;&lt; <span class="Constant">&quot;' expects 2 ingredients but got &quot;</span> &lt;&lt; SIZE<span class="Delimiter">(</span>inst<span class="Delimiter">.</span>ingredients<span class="Delimiter">)</span> &lt;&lt; <span class="cSpecial">'\n'</span> &lt;&lt; end<span class="Delimiter">();</span>
        <span class="Identifier">return</span><span class="Delimiter">;</span>
      <span class="Delimiter">}</span>
      replace_offset<span class="Delimiter">(</span>inst<span class="Delimiter">.</span>ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">1</span><span class="Delimiter">),</span> offset<span class="Delimiter">,</span> i<span class="Delimiter">,</span> r<span class="Delimiter">);</span>
    <span class="Delimiter">}</span>
    <span class="Normal">if</span> <span class="Delimiter">((</span>inst<span class="Delimiter">.</span>name == <span class="Constant">&quot;loop&quot;</span> || inst<span class="Delimiter">.</span>name == <span class="Constant">&quot;break&quot;</span><span class="Delimiter">)</span>
        &amp;&amp; SIZE<span class="Delimiter">(</span>inst<span class="Delimiter">.</span>ingredients<span class="Delimiter">)</span> &gt;= <span class="Constant">1</span><span class="Delimiter">)</span> <span class="Delimiter">{</span>
      replace_offset<span class="Delimiter">(</span>inst<span class="Delimiter">.</span>ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">),</span> offset<span class="Delimiter">,</span> i<span class="Delimiter">,</span> r<span class="Delimiter">);</span>
    <span class="Delimiter">}</span>
    <span class="Normal">if</span> <span class="Delimiter">((</span>inst<span class="Delimiter">.</span>name == <span class="Constant">&quot;loop-if&quot;</span> || inst<span class="Delimiter">.</span>name == <span class="Constant">&quot;loop-unless&quot;</span>
            || inst<span class="Delimiter">.</span>name == <span class="Constant">&quot;break-if&quot;</span> || inst<span class="Delimiter">.</span>name == <span class="Constant">&quot;break-unless&quot;</span><span class="Delimiter">)</span>
        &amp;&amp; SIZE<span class="Delimiter">(</span>inst<span class="Delimiter">.</span>ingredients<span class="Delimiter">)</span> &gt;= <span class="Constant">2</span><span class="Delimiter">)</span> <span class="Delimiter">{</span>
      replace_offset<span class="Delimiter">(</span>inst<span class="Delimiter">.</span>ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">1</span><span class="Delimiter">),</span> offset<span class="Delimiter">,</span> i<span class="Delimiter">,</span> r<span class="Delimiter">);</span>
    <span class="Delimiter">}</span>
  <span class="Delimiter">}</span>
<span class="Delimiter">}</span>

<span class="Delimiter">:(code)</span>
<span class="Normal">void</span> replace_offset<span class="Delimiter">(</span>reagent&amp; x<span class="Delimiter">,</span> <span class="Comment">/*</span><span class="Comment">const</span><span class="Comment">*/</span> map&lt;string<span class="Delimiter">,</span> <span class="Normal">int</span>&gt;&amp; offset<span class="Delimiter">,</span> <span class="Normal">const</span> <span class="Normal">int</span> current_offset<span class="Delimiter">,</span> <span class="Normal">const</span> recipe_ordinal r<span class="Delimiter">)</span> <span class="Delimiter">{</span>
  <span class="Normal">if</span> <span class="Delimiter">(</span>!is_literal<span class="Delimiter">(</span>x<span class="Delimiter">))</span> <span class="Delimiter">{</span>
    raise &lt;&lt; maybe<span class="Delimiter">(</span>get<span class="Delimiter">(</span>Recipe<span class="Delimiter">,</span> r<span class="Delimiter">).</span>name<span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;jump target must be offset or label but is &quot;</span> &lt;&lt; x<span class="Delimiter">.</span>original_string &lt;&lt; <span class="cSpecial">'\n'</span> &lt;&lt; end<span class="Delimiter">();</span>
    x<span class="Delimiter">.</span>set_value<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">);</span>  <span class="Comment">// no jump by default</span>
    <span class="Identifier">return</span><span class="Delimiter">;</span>
  <span class="Delimiter">}</span>
  <span class="Normal">if</span> <span class="Delimiter">(</span>x<span class="Delimiter">.</span>initialized<span class="Delimiter">)</span> <span class="Identifier">return</span><span class="Delimiter">;</span>
  <span class="Normal">if</span> <span class="Delimiter">(</span>is_integer<span class="Delimiter">(</span>x<span class="Delimiter">.</span>name<span class="Delimiter">))</span> <span class="Identifier">return</span><span class="Delimiter">;</span>  <span class="Comment">// non-labels will be handled like other number operands</span>
  <span class="Normal">if</span> <span class="Delimiter">(</span>!is_jump_target<span class="Delimiter">(</span>x<span class="Delimiter">.</span>name<span class="Delimiter">))</span> <span class="Delimiter">{</span>
    raise &lt;&lt; maybe<span class="Delimiter">(</span>get<span class="Delimiter">(</span>Recipe<span class="Delimiter">,</span> r<span class="Delimiter">).</span>name<span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;can't jump to label &quot;</span> &lt;&lt; x<span class="Delimiter">.</span>name &lt;&lt; <span class="cSpecial">'\n'</span> &lt;&lt; end<span class="Delimiter">();</span>
    x<span class="Delimiter">.</span>set_value<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">);</span>  <span class="Comment">// no jump by default</span>
    <span class="Identifier">return</span><span class="Delimiter">;</span>
  <span class="Delimiter">}</span>
  <span class="Normal">if</span> <span class="Delimiter">(</span>!contains_key<span class="Delimiter">(</span>offset<span class="Delimiter">,</span> x<span class="Delimiter">.</span>name<span class="Delimiter">))</span> <span class="Delimiter">{</span>
    raise &lt;&lt; maybe<span class="Delimiter">(</span>get<span class="Delimiter">(</span>Recipe<span class="Delimiter">,</span> r<span class="Delimiter">).</span>name<span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;can't find label &quot;</span> &lt;&lt; x<span class="Delimiter">.</span>name &lt;&lt; <span class="cSpecial">'\n'</span> &lt;&lt; end<span class="Delimiter">();</span>
    x<span class="Delimiter">.</span>set_value<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">);</span>  <span class="Comment">// no jump by default</span>
    <span class="Identifier">return</span><span class="Delimiter">;</span>
  <span class="Delimiter">}</span>
  x<span class="Delimiter">.</span>set_value<span class="Delimiter">(</span>get<span class="Delimiter">(</span>offset<span class="Delimiter">,</span> x<span class="Delimiter">.</span>name<span class="Delimiter">)</span> - current_offset<span class="Delimiter">);</span>
<span class="Delimiter">}</span>

<span class="Normal">bool</span> is_jump_target<span class="Delimiter">(</span>string label<span class="Delimiter">)</span> <span class="Delimiter">{</span>
  <span class="Identifier">return</span> label<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">)</span> == <span class="Constant">'+'</span><span class="Delimiter">;</span>
<span class="Delimiter">}</span>

<span class="Delimiter">:(scenario break_to_label)</span>
def main [
  <span class="Delimiter">{</span>
    <span class="Delimiter">{</span>
      <span class="Identifier">break</span> +target:label
      <span class="Constant">1</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
    <span class="Delimiter">}</span>
  <span class="Delimiter">}</span>
  +target
]
<span class="traceAbsent">-mem: storing 0 in location 1</span>

<span class="Delimiter">:(scenario jump_if_to_label)</span>
def main [
  <span class="Delimiter">{</span>
    <span class="Delimiter">{</span>
      jump-<span class="Normal">if</span> <span class="Constant">1</span><span class="Delimiter">,</span> +target:label
      <span class="Constant">1</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
    <span class="Delimiter">}</span>
  <span class="Delimiter">}</span>
  +target
]
<span class="traceAbsent">-mem: storing 0 in location 1</span>

<span class="Delimiter">:(scenario loop_unless_to_label)</span>
def main [
  <span class="Delimiter">{</span>
    <span class="Delimiter">{</span>
      loop-unless <span class="Constant">0</span><span class="Delimiter">,</span> +target:label  <span class="Comment"># loop/break with a label don't care about braces</span>
      <span class="Constant">1</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
    <span class="Delimiter">}</span>
  <span class="Delimiter">}</span>
  +target
]
<span class="traceAbsent">-mem: storing 0 in location 1</span>

<span class="Delimiter">:(scenario jump_runs_code_after_label)</span>
def main [
  <span class="Comment"># first a few lines of padding to exercise the offset computation</span>
  <span class="Constant">1</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
  <span class="Constant">2</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
  <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
  jump +target:label
  <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
  +target
  <span class="Constant">5</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
]
<span class="traceContains">+mem: storing 0 in location 5</span>
<span class="traceAbsent">-mem: storing 0 in location 4</span>

<span class="Delimiter">:(scenario jump_fails_without_target)</span>
<span class="Special">% Hide_errors = true;</span>
def main [
  jump
]
<span class="traceContains">+error: main: 'jump' expects an ingredient but got none</span>

<span class="Delimiter">:(scenario jump_fails_without_target_2)</span>
<span class="Special">% Hide_errors = true;</span>
def main [
  jump-<span class="Normal">if</span> <span class="Constant">1</span>/<span class="Constant">true</span>
]
<span class="traceContains">+error: main: 'jump-if' expects 2 ingredients but got 1</span>

<span class="Delimiter">:(scenario recipe_fails_on_duplicate_jump_target)</span>
<span class="Special">% Hide_errors = true;</span>
def main [
  +label
  <span class="Constant">1</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
  +label
  <span class="Constant">2</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
]
<span class="traceContains">+error: main: duplicate label '+label'</span>

<span class="Delimiter">:(scenario jump_ignores_nontarget_label)</span>
<span class="Special">% Hide_errors = true;</span>
def main [
  <span class="Comment"># first a few lines of padding to exercise the offset computation</span>
  <span class="Constant">1</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
  <span class="Constant">2</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
  <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
  jump $target:label
  <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
  $target
  <span class="Constant">5</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
]
<span class="traceContains">+error: main: can't jump to label $target</span>
</pre>
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