gcc 2.7.2.3 on SCO os5.0.5 - Experiences, Suggestions

[Helmut Schellong]

gcc 2.7.2.3 on SCO os5.0.5, installed from Skunkware98-CD
intel-pentium
---------------------------------------------------------
Experiences, Suggestions:
-------------------------

Hello,
I have worked with your 'gcc' for the first time
and have compared it with 'icc' and 'cc'.

Current start script see below.


Experiences:
==============================================================
step (separate)                     code size     speed
--------------------------------------------------------------
-O1                                  ---           +++
-O2                                  ++            --
-O3                                  +++           --
BEGIN                                131000        .82s
-funsigned-char                      -             +
-fwritable-strings (.text->.data)    .             ++
jump_tables .text --> .data          .             ++
-malign-loops=0 -malign-jumps=0      ---           +
            -malign-functions=2
-fomit-frame-pointer                 --            +
-fforce-mem                          -             .
-fcaller-saves                       -             +
-m386                                -             +
((regparm(1)))  #few                 -             +
((regparm(2)))  #few                 +             -
((regparm(1)))  #more                -             Bugs!
-mrtd                                ---           (++?)
-fcall-saved-ebx -fcall-saved-esi    ---           (++?)
                 -fcall-saved-edi
 with frame ptr  -fcall-saved-ecx!
-fcall-saved-ebx -fcall-saved-esi    --            (+?)
                 -fcall-saved-edi
 without fr_ptr  -fcall-saved-ecx!
END                                  116100        .65s

icc  (optimized)                     156000        .72s
cc   (optimized)                     123000        .79s
==============================================================


Suggestions:
------------
sometimes:  movzbl --> xorl eax,eax ; movb bl,al
            movzbl 4(ebx), esi    is okay (mem)

Add option:
-fjumptables-data
(see above)

Add options:
-fcall-saved-static
-fcall-saved-public
-fcall-saved-extern
(-fcaller-saves is the little brother)
-fcall-used-static
-fcall-used-public
-fcall-used-extern
-mrtd-static
-mrtd-public
-mrtd-extern
-mregparm-static
-mregparm-public
-mregparm-extern
Reason: the affected options normally are not applicable
because of the global effect (libraries)!

(Add option:
 -S -fasm-merge-c-source)


Nota:
-----
icc and cc put string literals and jump tables
into .data-sector per default or without choice.
Putting into .text is bad on pentium.
(into .rodata would be perfect, but...)


Failed:
-------
((stdcall,cdecl))   do not work and additionally
                    cancel all other attributes.
((regparm(n)))      works with small functions
                    they not contain any call.
                    Otherwise --> SIGSEGV,...


======================================================
:
set -f
RW=-fwritable-strings
gcc -m386 -funsigned-char -s -mcoff -O1 $RW  \
    -Wall -fverbose-asm \
    -Wno-uninitialized -Wno-parentheses -Wno-char-subscripts \
    -Wpointer-arith -Wcast-align \
    -Wwrite-strings \
    -Wstrict-prototypes \
    -Wmissing-prototypes \
    -Wmissing-declarations \
    -malign-loops=0 -malign-jumps=0 -malign-functions=2 \
    -fomit-frame-pointer \
    -fforce-mem \
    -fcaller-saves \
    -I/u/l/h  $*  -lx
   #-malign-double \
   #-fexpensive-optimizations \
   #-mreg-alloc=acdbSDB \
   #-fno-defer-pop \
   #-fcall-saved-ebx \
   #-fcall-saved-esi \
   #-fcall-saved-edi \
   #-fcall-saved-ecx \
   #-fcall-used-ecx \
   #-fforce-addr \
   #-Wconversion \
   #-Wnested-externs \
   #-ffast-math \
   #-Wcast-qual \
   #-Wshadow -Wredundant-decls \
======================================================

-- 
Mit freundlichen Grüßen
Helmut Schellong
post@schellong.de
http://www.schellong.de