[Bug c/35295] New: 64-bit host cross compile to 32-bit target differs from 32-bit host cross compile to 32-bit target

[Bug c/35295] New: 64-bit host cross compile to 32-bit target differs from 32-bit host cross compile to 32-bit target

[benny at ammitzboell-consult dot dk]

We are cross-compiling to a 32-bit ARM target from both 32-bit and 64-bit PCs.
The  gcc cross-compiler toolchain (3.4.6) generates valid code in both cases,
but the generated code is larger when a 64-bit host is used. We have tracked
this down to the following:

1) The RTL is using 64-bit (on the 64-bit host) to represent constants that is
calculated as part of the code-generation. Perhaps because print-rtl.c is using
HOST_WIDE_INT_xxx in some places. Surely any kind of constant number even in
high level RTL should be using the *target* int size and not the host?
2) The 64-bit constants are treated as such and thus generates more assembler
instructions to deal with the 64-bit number on the 32-bit target.

We have fixed the toolchain with a workaround where "-m32" is used to compile
the entire toolchain as 32-bit, but I think the correct solution would be to
ensure that constants used in the RTL are represented using the target format
in stead of the host.

As far as I can see from the code (print-rtl.c) the problem is still there in
gcc 4.2.3.


-- 
           Summary: 64-bit host cross compile to 32-bit target differs from
                    32-bit host cross compile to 32-bit target
           Product: gcc
           Version: 3.4.6
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: benny at ammitzboell-consult dot dk
 GCC build triplet: i686-pc-linux-gnu / x86_64-unknown-linux-gnu
  GCC host triplet: i686-pc-linux-gnu / x86_64-unknown-linux-gnu
GCC target triplet: arm-uclinux-elf


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35295

[Bug c/35295] 64-bit host cross compile to 32-bit target differs from 32-bit host cross compile to 32-bit target

[rguenth at gcc dot gnu dot org]

------- Comment #1 from rguenth at gcc dot gnu dot org  2008-02-22 14:38 -------
Do you have a testcase?  The constants should be printed according to their
mode, which is target dependent.  The host representation should not matter
apart for the biggest supported mode.


-- 

rguenth at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |WAITING


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35295

[Bug middle-end/35295] 64-bit host cross compile to 32-bit target differs from 32-bit host cross compile to 32-bit target

[pinskia at gcc dot gnu dot org]

------- Comment #2 from pinskia at gcc dot gnu dot org  2008-02-22 17:58 -------
As when you say bigger do you mean the assembly is different sizes?  Or do you
mean the actually text/data sections are bigger in the object file?


-- 

pinskia at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
          Component|c                           |middle-end


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35295

[Bug middle-end/35295] 64-bit host cross compile to 32-bit target differs from 32-bit host cross compile to 32-bit target

[benny at ammitzboell-consult dot dk]

------- Comment #3 from benny at ammitzboell-consult dot dk  2008-02-25 14:09 -------
Created an attachment (id=15224)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=15224&action=view)
Test program


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35295

[Bug middle-end/35295] 64-bit host cross compile to 32-bit target differs from 32-bit host cross compile to 32-bit target

[benny at ammitzboell-consult dot dk]

------- Comment #4 from benny at ammitzboell-consult dot dk  2008-02-25 14:13 -------
Created an attachment (id=15225)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=15225&action=view)
Output from arm-gcc -c -dr main.c (32-bit host)


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35295

[Bug middle-end/35295] 64-bit host cross compile to 32-bit target differs from 32-bit host cross compile to 32-bit target

[benny at ammitzboell-consult dot dk]

------- Comment #5 from benny at ammitzboell-consult dot dk  2008-02-25 14:14 -------
Created an attachment (id=15226)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=15226&action=view)
Output from arm-gcc -c -dM main.c (32-bit host)


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35295

[Bug middle-end/35295] 64-bit host cross compile to 32-bit target differs from 32-bit host cross compile to 32-bit target

[benny at ammitzboell-consult dot dk]

------- Comment #6 from benny at ammitzboell-consult dot dk  2008-02-25 14:21 -------
Created an attachment (id=15227)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=15227&action=view)
Output from arm-gcc -c -dr main.c (64-bit host)


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35295

[Bug middle-end/35295] 64-bit host cross compile to 32-bit target differs from 32-bit host cross compile to 32-bit target

[benny at ammitzboell-consult dot dk]

------- Comment #7 from benny at ammitzboell-consult dot dk  2008-02-25 14:22 -------
Created an attachment (id=15228)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=15228&action=view)
Output from arm-gcc -c -dM main.c (64-bit host)


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35295

[Bug middle-end/35295] 64-bit host cross compile to 32-bit target differs from 32-bit host cross compile to 32-bit target

[benny at ammitzboell-consult dot dk]

------- Comment #8 from benny at ammitzboell-consult dot dk  2008-02-25 14:27 -------
Added test program and RTL output from 32-bit host and 64-bit host. Note the
difference in the const_int lines:

bla@bla-desktop:~/src/kuss$ diff /home/bla/Desktop/main.c.01.rtl
/home/bla/Desktop/main.c.01.rtl_64
7c7
<                 (const_int -4 [0xfffffffc])) [0 a+0 S4 A32])
---
>                 (const_int -4 [0xfffffffffffffffc])) [0 a+0 S4 A32])
15c15
< (note 6 5 7 0xf7eeb190 NOTE_INSN_BLOCK_BEG)
---
> (note 6 5 7 0x2ac25dcd19b0 NOTE_INSN_BLOCK_BEG)
29c29
<                 (const_int -4 [0xfffffffc])) [0 a+0 S4 A32])) -1 (nil)
---
>                 (const_int -4 [0xfffffffffffffffc])) [0 a+0 S4 A32])) -1 (nil)
39c39
<     (expr_list:REG_EH_REGION (const_int -1 [0xffffffff])
---
>     (expr_list:REG_EH_REGION (const_int -1 [0xffffffffffffffff])
49c49
<                         (const_int -4 [0xfffffffc])) [0 a+0 S4 A32]))
---
>                         (const_int -4 [0xfffffffffffffffc])) [0 a+0 S4 A32]))
54c54
<                 (const_int -4 [0xfffffffc])) [0 a+0 S4 A32])) -1 (nil)
---
>                 (const_int -4 [0xfffffffffffffffc])) [0 a+0 S4 A32])) -1 (nil)
107c107
< (note 32 31 33 0xf7eeb190 NOTE_INSN_BLOCK_END)
---
> (note 32 31 33 0x2ac25dcd19b0 NOTE_INSN_BLOCK_END)
125d124
<


Output from 64-bit host arm-gcc -v:

Reading specs from /arm-gcc-3/bin/../lib/gcc/arm-uclinux-elf/3.4.6/specs
Configured with: /arm-gcc3-source/build_arm-uclinux/gcc-3.4.6/configure 
--enable-languages=c --disable-libmudflap --disable-nls 
--enable-long-long --target=arm-uclinux-elf --prefix=/arm-gcc-3/ : 
(reconfigured) /arm-gcc3-source/build_arm-uclinux/gcc-3.4.6/configure 
--target=arm-uclinux-elf --prefix=/arm-gcc-3/ --enable-languages=c,c++ 
--enable-multilib --enable-target-optspace --with-gnu-ld --disable-nls 
--disable-__cxa_atexit --enable-threads=posix --disable-clocale 
--enable-long-long --disable-libstdcxx-pch --disable-checking
Thread model: posix
gcc version 3.4.6


Output from 32-bit host arm-gcc -v:

Reading specs from /arm-gcc-3/bin/../lib/gcc/arm-uclinux-elf/3.4.6/specs
Configured with: /arm-gcc3-source/build_arm-uclinux/gcc-3.4.6/configure 
--enable-languages=c --disable-libmudflap --disable-nls 
--enable-long-long --target=arm-uclinux-elf --host=i686-pc-linux-gnu 
--prefix=/arm-gcc-3/ : (reconfigured) 
/arm-gcc3-source/build_arm-uclinux/gcc-3.4.6/configure 
--target=arm-uclinux-elf --prefix=/arm-gcc-3/ --enable-languages=c,c++ 
--enable-multilib --enable-target-optspace --with-gnu-ld --disable-nls 
--disable-__cxa_atexit --enable-threads=posix --disable-clocale 
--enable-long-long --disable-libstdcxx-pch --disable-checking 
--host=i686-pc-linux-gnu
Thread model: posix
gcc version 3.4.6


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35295

[Bug middle-end/35295] 64-bit host cross compile to 32-bit target differs from 32-bit host cross compile to 32-bit target

[benny at ammitzboell-consult dot dk]

------- Comment #9 from benny at ammitzboell-consult dot dk  2008-02-25 14:31 -------
(In reply to comment #2)
> As when you say bigger do you mean the assembly is different sizes?  Or do you
> mean the actually text/data sections are bigger in the object file?
> 

The assembly is bigger on the 64-bit host. Because the 64-bit constants get
treated as such and generates more assembler.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35295

[Bug target/35295] 64-bit host cross compile to 32-bit target differs from 32-bit host cross compile to 32-bit target

[rguenth at gcc dot gnu dot org]

------- Comment #10 from rguenth at gcc dot gnu dot org  2008-02-25 15:43 -------
At first this looks like a target issue.  Can you check if a still maintained
GCC version is still affected?  That would be 4.2.3 for example.


-- 

rguenth at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
          Component|middle-end                  |target


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35295

[Bug target/35295] 64-bit host cross compile to 32-bit target differs from 32-bit host cross compile to 32-bit target

[benny at ammitzboell-consult dot dk]

------- Comment #11 from benny at ammitzboell-consult dot dk  2008-02-25 16:02 -------
(In reply to comment #10)
> At first this looks like a target issue.  Can you check if a still maintained
> GCC version is still affected?  That would be 4.2.3 for example.
> 

Since print-rtl.c in 4.2.3 still contains code like this:

        fprintf (outfile, HOST_WIDE_INT_PRINT_DEC, XWINT (in_rtx, i));
        if (! flag_simple)
          fprintf (outfile, " [" HOST_WIDE_INT_PRINT_HEX "]",
                   XWINT (in_rtx, i));

- I am assuming that the (RTL) behavior is the same as in my examples. But are
you saying that a later (target) stage should be able to see that this is just
a 32-bit const?


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35295

[Bug target/35295] 64-bit host cross compile to 32-bit target differs from 32-bit host cross compile to 32-bit target

[benny at ammitzboell-consult dot dk]

------- Comment #12 from benny at ammitzboell-consult dot dk  2008-02-28 08:18 -------
We have now tried the 4.2.3 version of gcc and it generates the same assembler
code (objdump -d) for the example here on both the 32-bit and the 64-bit host.
The RTL is still different though, so it seems you're right about it being a
target issue. We're trying to build a full toolchain with gcc 4.2.1 to verify
that result in a full-blown test on all of our code.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35295

[Bug target/35295] 64-bit host cross compile to 32-bit target differs from 32-bit host cross compile to 32-bit target

[benny at ammitzboell-consult dot dk]

------- Comment #13 from benny at ammitzboell-consult dot dk  2008-05-20 07:32 -------
Ok, we have verified that this bug is not present when using a 4.2.3 arm
toolchain.


-- 

benny at ammitzboell-consult dot dk changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|WAITING                     |RESOLVED
         Resolution|                            |FIXED


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35295

[Bug target/35295] 64-bit host cross compile to 32-bit target differs from 32-bit host cross compile to 32-bit target

[benny at ammitzboell-consult dot dk]

------- Comment #14 from benny at ammitzboell-consult dot dk  2008-05-20 07:33 -------
Verified on gcc 4.2.3


-- 

benny at ammitzboell-consult dot dk changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |VERIFIED


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35295