Updates:
Status: Accepted
Owner: robhamerling
Comment #2 on issue 190 by robhamerling: The use of "pragma inline"s in the
LCD_HD44780 libraries.
http://code.google.com/p/jallib/issues/detail?id=190
The 'pragma inline' directive in a procedure eliminates call/return
instructions and thus the number of used stack levels. Generally it will
also improve execution speed.
However an inline expanded procedure will generally use more code memory.
When shortage on stack levels is an issue (with deeply nested procedures or
PIC with few stack levels) the use of pragma inline can become a must, even
though the compiler will reduce the use of stack levels when possible.
With small procedures the use of pragma inline will be more attractive to
reduce code memory and improve speed than for large procedures, but when
these procedures are called frequently the effect may be adverse.
For a specific program one could experiment to find an optimum, but to find
a balance for libraries used by different programs and different types of
PICS is not so obvious.
Analysis of some sample programs shows that the lcd_hd44780 libraries use
relatively much code because some seemingly small procedures have a large
expansion, among others because the use of port shadowing by the device
files of the midrange PICs.
One possibility is to use 'pragma inline' more selectively. For example use
it only for PICs with much code memory and many stack levels, like 18F and
enhanced midrange. Need some experiments....
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