Support for computed goto

[clbr]

Depends on #873, and includes those commits so that the autobuilder will succeed.
Closes #864.

[oliverschmidt]

This looks like a rather complex change to me - and I don't understand it's importance.

@greg-king5: I'd appreciate your opinion!

[clbr]

Will fix the missing spaces, thanks.

As mentioned in #864, it allows efficient jump tables from C. A switch-case or a cascade of ifs can take 30x or more cpu vs what a jump table jump takes, and it also changes the timing from variable to constant. As a plus, it's also smaller than the alternatives.

[clbr]

That test shouldn't be done if the previous test says that the variable isn't an array.

Isn't that what the Error does? Stops execution since we can't compile this.

[greg-king5]

That test shouldn't be done if the previous test says that the variable isn't an array.

Isn't that what Error() does: stops execution since we can't compile this?

Warning() and Error() show diagnostics on stderr, and count them. Compilation continues, so that other problems can be found. At the end, the output file is written only if no errors were counted.

[clbr]

I checked the source; it's only fatal after a few errors, my mistake, I remembered it was fatal instantly.

[clbr]

About the "only for jumps" message, expanding it slightly:
"Do the test only for jumps, because the lib code has manual asm statements like asm("bne L1"). These L1-named labels don't match the IsLocalLabel function, and not emitting that label would break the function".

[polluks]

Maybe a hint in cc65.html#s5?

[oliverschmidt]

[...] and I don't understand it's importance.

Now with the docs addition I get it...

@greg-king5: Thanks for your review! As far as I can see this pr is ready to be merged from your pov, right? In that case please either acknowledge or merge right away.

@polluks: Thanks for the hint on the docs.

[greg-king5]

As mentioned in #864, it allows efficient jump tables from C. A switch-case or a cascade of ifs can take 30x or more CPU time vs what a jump-table jump takes. And, it also changes the timing from variable to constant. As a plus, it's also smaller than the alternatives.

Those advantages are useful especially when making game animations.

Merging ...