[m-rev.] for review: put almost all layout structures in arrays

[Paul Bone]

On Wed, Oct 28, 2009 at 07:26:13PM +1100, Zoltan Somogyi wrote:
> For review by anyone. Note that the diffs for layout_out.m and stack_layout.m
> are about the same size as the files themselves, so reviewing the files
> would probably be easier.
> 
> Zoltan.
> 
> Move all the frequently occurring layout structures and components of layout
> structures into arrays where possible. By replacing N global variables holding
> individual layout structures or layout structure components with one global
> variable holding an array of them, we reduce the sizes of the symbol tables
> stored in object files, which should speed up both the C compiler and the
> linker.
> 
> Measured on the modules of the library, mdbcomp and compiler directories
> compiled in grade asm_fast.gc.debug, this diff reduces the size of the
> generated C source files by 7.8%, the size of the generated object files
> by 10.4%, and the number of symbols in the symbol tables of those object files
> by a whopping 42.8%. (These improvements include, and are not on top of,
> the improvements in my previous similar diff.)

Do we know if this effects execution speed?  It may change locality of
reference.  I can't say if I expect to see an improvement, a loss or no change,
caching effects are hard to predict :-).

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