binutils 2.14a i370 gas literal issue

[Jens Remus]

Hello Paul!

Am 21.08.2024 um 10:11 schrieb Paul Edwards:
> I am aware that 2.14a is out of support, and I am also aware
> that the i370 target of gas is no longer supported at all on the
> modern binutils.
> 
> However, if someone is interested in helping resolve this
> issue "for old time's sake", that would be great.

As a former z/VSE developer with HLASM background I could not resist the 
urge to have a short look.

> Basically the issue is - where did all my C1 disappear to?

I assume it must be a bug in the customized Binutils build you are 
using. If you are lucky it may just be a glitch in the produced listing 
and not in the object code.

> Note that I am using a slightly modified 2.14a - the modifications
> can be found in binutils-stage* in custom.zip from pdos.org and
> the precompiled binaries that are run below are available in
> customb.zip from pdos.org
> 
> I don't know what the situation is with other versions of binutils.

i370 support got removed in Binutils 2.31 with commit 6793974daae8 
("Remove i370 support"). Therefore I have built Binutils 2.30 on Linux 
as follows and gave it a try. The results don't look very promising. 
This may be due to my build being broken, since I could only get it to 
build using the current compilers by suppressing compile warnings 
getting treated as errors (--disable-werror).

$ git checkout binutils-2_30-branch
$ mkdir build-i370
$ cd build-i370
$ ../configure --prefix=$HOME/temp/binutils-2.30-i370 
--target=i370-linux-gnu --enable-obsolete --disable-werror --disable-gdb
$ make -j $(nproc)
$ make install

$ cd $HOME/temp/binutils-2.30-i370

$ cat paul.s
.text
.globl main
.using .,r7
          MVC   92(8,r13),=XL8'C1C1C1C1C1C1C1C1'
          MVC   100(8,r13),=XL8'C2C2C2C2C2C2C2C2'
.ltorg

$ bin/i370-linux-gnu-as -a=list.txt -o paul.o paul.s

$ cat list.txt
GAS LISTING paul.s                      page 1


    1                    .text
    2                    .globl main
    3                    .using .,r7
    4 0000 D207D05C               MVC   92(8,r13),=XL8'C1C1C1C1C1C1C1C1'
    4      7010
    5 0006 D207D064               MVC   100(8,r13),=XL8'C2C2C2C2C2C2C2C2'
    5      7012
    6 000c 00000000      .ltorg
    6      C1C1C1C1
    6      C1C1C1C1
    6      C2C2C2C2
    6      C2C2C2C2

GAS LISTING paul.s                      page 2


NO DEFINED SYMBOLS

UNDEFINED SYMBOLS
main

The offset of the literal pool in the listing looks odd. But it is 
apparently correct in the object (see below; although i370-objdump has 
issues to disassemble). The offsets encoded in the MVC instructions 
relative to r7 seem wrong to me though. They appear to be correct in 
your listing.

> D:\devel\gcc\gcc>type list.txt
> GAS LISTING paul.s                      page 1
> 
> 
>     1                    .text
>     2                    .globl main
>     3                    .using .,r7
>     4 0000 D207D05C               MVC   92(8,r13),=XL8'C1C1C1C1C1C1C1C1'
>     4      7010
>     5 0006 D207D064               MVC   100(8,r13),=XL8'C2C2C2C2C2C2C2C2'
>     5      7018
>     6 000c 00000000      .ltorg
>     6      C2C2C2C2
>     6      C2C2C2C2
>     6      C2C2C2C2
>     6      C2C2C2C2
> ♀GAS LISTING paul.s                     page 2
> 
> 
> NO DEFINED SYMBOLS
> 
> UNDEFINED SYMBOLS
> main

Did you check using objdump as follows whether your assembly listing 
matches with the generated object code? Maybe your C1s are just missing 
in the listing?

$ bin/i370-linux-gnu-objdump -d paul.o

paul.o:     file format elf32-i370


Disassembly of section .text:

00000000 <.text>:
    0:   d2 07 d0 5c     mvc     92(7,r13,16(r7)
    4:   70 10
    6:   d2 07 d0 64     mvc     100(7,r13,18(r7)
    a:   70 12
    c:   00 00           .short 0x0000
    e:   00 00           .short 0x0000
   10:   c1 c1           .short 0xc1c1
   12:   c1 c1           .short 0xc1c1
   14:   c1 c1           .short 0xc1c1
   16:   c1 c1           .short 0xc1c1
   18:   c2 c2           .short 0xc2c2
   1a:   c2 c2           .short 0xc2c2
   1c:   Address 0x000000000000001c is out of bounds.

$ bin/i370-linux-gnu-objdump -s paul.o

paul.o:     file format elf32-i370

Contents of section .text:
  0000 d207d05c 7010d207 d0647012 00000000  ...\p....dp.....
  0010 c1c1c1c1 c1c1c1c1 c2c2c2c2 c2c2c2c2  ................

Good luck with your endeavor!

Regards,
Jens
-- 
Jens Remus
Linux on Z Development (D3303) and z/VSE Support
+49-7031-16-1128 Office
jremus@de.ibm.com

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