Mail Archives: djgpp-workers/1998/10/08/10:29:11
Eli Zaretskii <eliz AT is DOT elta DOT co DOT il> wrote:
> If I understand correctly the message by Ian Taylor (below), it would
> be a good idea to define COFF_DEFAULT_SECTION_ALIGNMENT_POWER to make
> executable be aligned on more than 4 bytes (is 8 okay for a Pentium?),
16 is recommended for K6 and 32 is ideal (too much waste). I think that true
for any advanced processor because the caches works retrieving groups of 32
bytes (1 tag entry for 32 bytes). I saw that 16 was ok for a simple Cyrix
5x86 (486 family) because the internal bus is 128 bits wide.
> unless [34]86 will be somehow punished by that.
I think they will be punished because of the small cache.
> Alternatively, we could change lib/specs to make GCC pass alignment
> options to ld when -mpentium or such likes are use, but I don't see
> any options to ld that can be used for that. Did I miss something?
I don't know. Some time ago I solved the aligment problems in the following
way:
1) I created a special section in the ld script aligned 512 bytes.
2) I marked all the critical functions with attribute section, forcing the
routines to be placed in this section.
3) Compiled the modules with big aligments.
In this way only the critical routines are "bloated" by the aligment.
I got the same answer you copied when I faced this problem (COFF limitation).
Another option is provide another copy of the libraries compiled with large
aligments.
Some weeks ago I timed some routines in my K6 using the Pentium instructions
to meassure the clocks, I found the difference between well aligned and 4
bytes aligned routines (for small loops) is huge.
> Btw, is somebody still working on porting Binutils 2.9?
I have this link in my pages:
A beta test release of binutils 2.9.1 by <a
href="mailto:andrewc AT rosemail DOT rose DOT hp DOT com">Andrew Crabtree</a> can be found
<a href="ftp://www.goof.com/pub/pcg/private/andrew/">here</a> or perhaps was
moved <a href="http://www.goof.com/pcg/data/djgpp/">here</a>.
So I think you'll get a better answer from Andrew ;-)
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