[Bug target/103773] New: wrong code at -Oz due to sign extension

[Bug target/103773] New: wrong code at -Oz due to sign extension

[zsojka at seznam dot cz]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103773

            Bug ID: 103773
           Summary: wrong code at -Oz due to sign extension
           Product: gcc
           Version: 12.0
            Status: UNCONFIRMED
          Keywords: wrong-code
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: zsojka at seznam dot cz
                CC: roger at nextmovesoftware dot com
  Target Milestone: ---
              Host: x86_64-pc-linux-gnu
            Target: x86_64-pc-linux-gnu

Created attachment 52034
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=52034&action=edit
reduced testcase

Output:
$ x86_64-pc-linux-gnu-gcc -Oz testcase.c
$ ./a.out 
Aborted

$ x86_64-pc-linux-gnu-gcc -v
Using built-in specs.
COLLECT_GCC=/repo/gcc-trunk/binary-latest-amd64/bin/x86_64-pc-linux-gnu-gcc
COLLECT_LTO_WRAPPER=/repo/gcc-trunk/binary-trunk-r12-6072-20211220084313-g8d1e342b4af-checking-yes-rtl-df-extra-amd64/bin/../libexec/gcc/x86_64-pc-linux-gnu/12.0.0/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: /repo/gcc-trunk//configure --enable-languages=c,c++
--enable-valgrind-annotations --disable-nls --enable-checking=yes,rtl,df,extra
--with-cloog --with-ppl --with-isl --build=x86_64-pc-linux-gnu
--host=x86_64-pc-linux-gnu --target=x86_64-pc-linux-gnu
--with-ld=/usr/bin/x86_64-pc-linux-gnu-ld
--with-as=/usr/bin/x86_64-pc-linux-gnu-as --disable-libstdcxx-pch
--prefix=/repo/gcc-trunk//binary-trunk-r12-6072-20211220084313-g8d1e342b4af-checking-yes-rtl-df-extra-amd64
Thread model: posix
Supported LTO compression algorithms: zlib zstd
gcc version 12.0.0 20211220 (experimental) (GCC)

[Bug target/103773] wrong code at -Oz due to sign extension

[roger at nextmovesoftware dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103773

Roger Sayle <roger at nextmovesoftware dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Assignee|unassigned at gcc dot gnu.org      |roger at nextmovesoftware dot com
   Last reconfirmed|                            |2021-12-20
     Ever confirmed|0                           |1
             Status|UNCONFIRMED                 |ASSIGNED

--- Comment #1 from Roger Sayle <roger at nextmovesoftware dot com> ---
Sorry. Mine. Bootstrapping and regression testing a fix now.

[Bug target/103773] wrong code at -Oz due to sign extension

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103773

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jakub at gcc dot gnu.org

--- Comment #2 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Also:
int a;

void
foo (void)
{
  a = -42;
}
which corrupts some random unrelated memory.
For the TARGET_64BIT movsi case, it needs to be done only if the destination is
a register rather than MEM.

Mostly unrelated, I wonder if we shouldn't have a separate TYPE_PUSHPOP, decide
in the (set (attr "type") and then just emit it and get e.g. the "length"
attribute right for it.

[Bug target/103773] wrong code at -Oz due to sign extension

[roger at nextmovesoftware dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103773

--- Comment #3 from Roger Sayle <roger at nextmovesoftware dot com> ---
Patch proposed
https://gcc.gnu.org/pipermail/gcc-patches/2021-December/587258.html

[Bug target/103773] wrong code at -Oz due to sign extension

[zsojka at seznam dot cz]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103773

--- Comment #4 from Zdenek Sojka <zsojka at seznam dot cz> ---
(In reply to Roger Sayle from comment #3)
> Patch proposed
> https://gcc.gnu.org/pipermail/gcc-patches/2021-December/587258.html

Thank you for the patch. Does it work correctly with the red zone? I am asking
since the "mov" instruction normally doesn't affect stack, and I don't see any
indication that the "push" alternative does. But I definitely do not have
enough knowledge about the GCC internals.

[Bug target/103773] wrong code at -Oz due to sign extension

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103773

--- Comment #5 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Roger Sayle <sayle@gcc.gnu.org>:

https://gcc.gnu.org/g:ef26c151c14a87177d46fd3d725e7f82e040e89f

commit r12-6106-gef26c151c14a87177d46fd3d725e7f82e040e89f
Author: Roger Sayle <roger@nextmovesoftware.com>
Date:   Thu Dec 23 12:33:07 2021 +0000

    x86: PR target/103773: Fix wrong-code with -Oz from pop to memory.

    This is a fix to PR target/103773 where -Oz shouldn't use push/pop
    on x86 to shrink writing small integer constants to memory.
    Instead clang uses "andl $0, mem" for writing zero, and "orl $-1, mem"
    when writing -1 to memory when using -Oz.  This patch implements this
    via peephole2 where we can confirm that its ok to clobber the flags.

    2021-12-23  Roger Sayle  <roger@nextmovesoftware.com>
                Uroš Bizjak  <ubizjak@gmail.com>

    gcc/ChangeLog
            PR target/103773
            * config/i386/i386.md (*mov<mode>_and): New define_insn for
            writing a zero to memory using AND.
            (*mov<mode>_or): Extend to allow memory destination and HImode.
            (*movdi_internal): Remove -Oz push/pop optimization from here.
            (*movsi_internal): Likewise.
            (peephole2): Perform -Oz push/pop optimization here, only for
            register destinations, values other than zero, and in functions
            that don't used the red zone.
            (peephole2): With -Oz, convert writes of 0 or -1 to memory into
            their clobber forms, i.e. *mov<mode>_and and *mov<mode>_or resp.

    gcc/testsuite/ChangeLog
            PR target/103773
            * gcc.target/i386/pr103773-2.c: New test case.
            * gcc.target/i386/pr103773.c: New test case.

[Bug target/103773] wrong code at -Oz due to sign extension

[roger at nextmovesoftware dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103773

Roger Sayle <roger at nextmovesoftware dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
   Target Milestone|---                         |12.0
         Resolution|---                         |FIXED

--- Comment #6 from Roger Sayle <roger at nextmovesoftware dot com> ---
This shoud now be fixed on mainline.