[sdcc-devel] [ sdcc-Bugs-1057478 ] genjumptab's code fails

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Bugs item #1057478, was opened at 2004-10-30 15:31
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Category: pic16 target
Group: None
Status: Open
Resolution: None
Priority: 5
Submitted By: Nobody/Anonymous (nobody)
Assigned to: Nobody/Anonymous (nobody)
Summary: genjumptab's code fails

Initial Comment:
The code generated by PIC16's genJumpTab (used for
resolving switch-case-statements) has two problems:

(1) the jump table is indexed with the value N of
     the case-statement but should be indexed by
     N*4 (as 4 is the number of bytes spent on the
     GOTO case_N_label instruction)

(2) if the jump table (i.e. the list of GOTOs) crosses a
     256 byte boundary in program memory, not only PCL
     but also PCLATH and possibly PCLATU have to be
     adjusted

We attached a patch fixing both issues but also introducing
quite an overhead on the jump table code (multiplying N by
four and preparing the 256 bank crossing). Maybe switch-
statements with less than (say) 5 CASEs should not use
jump tables?

Greetings
Raphael Neider and Daniel Winkler

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