Re: Switch statement code generation

On 2009-11-03, Joshua Cranmer <Pidgeot18@verizon.invalid> wrote:
> I'm trying to put together a list of various methods to do code generate
> for switch statements.
>
> This is what I have so far:
> * Successive if/else branches
> * Jump tables
> * branch tables with linear and binary scans
> * Clustering tables (e.g., if you have cases 0-100 and 300-400).
>
> Are there any other methods worth mentioning?


if/else arranged in a binary search tree, rather than linear succession.
Analogous to your branch table with binary scan, but using code
rather than a table to reduce the comparions for N labels to log N.


E.g. cases are:


10 50 90 1000 1200 3000 4000 7500 12345


    if (x < 3000) {
          if (x < 90) {
              if (x == 10) {
                    ...
              } else if (x == 50) {
                    ...
              }
          } else {
              if (x == 90) {
                  ...
              } else if (x == 1000) {
                  ...
              } else if (x == 1200) {
                  ...
              }
          }
    } else {
        /* similarly for 3000-12345 range */
    }


This can combine with clustering. Binary search to classify an input
value into cluster ranges, then check the range and use the table for that
range, or default out.

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