[Bug ipa/94178] New: [10 Regression] wrong code with -fipa-sra + invalid -Wuninitialized warning

["zsojka at seznam dot cz" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94178

            Bug ID: 94178
           Summary: [10 Regression] wrong code with -fipa-sra + invalid
                    -Wuninitialized warning
           Product: gcc
           Version: 10.0
            Status: UNCONFIRMED
          Keywords: wrong-code
          Severity: normal
          Priority: P3
         Component: ipa
          Assignee: unassigned at gcc dot gnu.org
          Reporter: zsojka at seznam dot cz
                CC: marxin at gcc dot gnu.org
  Target Milestone: ---
              Host: x86_64-pc-linux-gnu

Created attachment 48034
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=48034&action=edit
reduced testcase

Output:
$ x86_64-pc-linux-gnu-gcc -O -fno-dce -fipa-sra -fno-tree-dce testcase.c
-Wuninitialized
testcase.c: In function 'main':
testcase.c:10:5: warning: 'y' is used uninitialized in this function
[-Wuninitialized]
   10 |   y /= (u128) x;
      |     ^~
testcase.c:8:1: note: 'y' was declared here
    8 | foo (u32 x, u8 y)
      | ^~~
testcase.c:10:8: warning: 'x' is used uninitialized in this function
[-Wuninitialized]
   10 |   y /= (u128) x;
      |        ^~~~~~~~
testcase.c:8:1: note: 'x' was declared here
    8 | foo (u32 x, u8 y)
      | ^~~

$ ./a.out 
Floating point exception

The generated assembly code:
        mov     edx, 0
        mov     ecx, 0
        mov     edi, 0
        mov     esi, 0
        call    __udivti3
shows it tries to do a 0/0 operation.

(I failed to search gcc bugs with keyword "wrong-code", I just can't find the
Keywords field at the Search page)

$ 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-r10-7179-20200315012740-g9c3cdb43c2b-checking-yes-rtl-df-extra-nobootstrap-amd64/bin/../libexec/gcc/x86_64-pc-linux-gnu/10.0.1/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
--disable-bootstrap --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-r10-7179-20200315012740-g9c3cdb43c2b-checking-yes-rtl-df-extra-nobootstrap-amd64
Thread model: posix
Supported LTO compression algorithms: zlib zstd
gcc version 10.0.1 20200315 (experimental) (GCC)