• register at file scope

    From Philipp Klaus Krause@21:1/5 to All on Mon Nov 25 12:19:29 2019
    Am 29.10.19 um 10:00 schrieb Philipp Klaus Krause:
    Introducing this as a compiler extension first and also evaluate the
    impact of placing register in appropriate places in some real-world code
    or a benchmark would indeed make sense.


    I did a first experiment; there, the improvements in benchmarks are far
    less than what one sees in synthetic examples.


    * SDCC version based on current SDCC with support for register at file
    scope added. For now, the information is used in two places in
    redundancy elimination only.
    * Annotated file scope variables in 4 benchmarks (Coremark, Dhrystone, stdcbench, Whetstone) with register storage class where appropriate.
    * Compiled the benchmarks for STM8 with strong optimization (--max-allocs-per-node 100000), using default balanced optimization goal.


    * stdcbench, Coremark: No difference at all. No surprise, since they
    both use very few file scope variables, and typically not in the inner
    * Whetstone: 0.8 % increase in score, 0.3 % reduction in code size.
    Whtstone uses some file scope variables, but doesn't do much with
    pointers, so no surprise here, either.
    * Dhrystone: 1.4 % increase in score, 0.1 % increase in code size. IMO,
    1.4 % is a surprisingly large increase, considering that Dhrystone tends
    to spent most of its time in string functions from the standard library,
    which are not affected by the change at all.


    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)