[Bug target/85090] New: wrong code with -O2 -fno-tree-dominator-opts -mavx512f -fira-algorithm=priority

[zsojka at seznam dot cz]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85090

            Bug ID: 85090
           Summary: wrong code with -O2 -fno-tree-dominator-opts -mavx512f
                    -fira-algorithm=priority
           Product: gcc
           Version: 8.0
            Status: UNCONFIRMED
          Keywords: wrong-code
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: zsojka at seznam dot cz
  Target Milestone: ---
              Host: x86_64-pc-linux-gnu
            Target: x86_64-pc-linux-gnu

Created attachment 43766
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=43766&action=edit
reduced testcase

Compiler output:
$ x86_64-pc-linux-gnu-gcc -O2 -fno-tree-dominator-opts -mavx512f
-fira-algorithm=priority testcase.c
$ sde64 -- ./a.out
Aborted

The value of x[] is "0000 0001 0002 0003 0000 0000 0000 0000 ...." instead of
"0000 0001 0002 0003 0004 0005 0006 0007 ...."

In the assembly output:
...
# testcase.c:13:   i[0] <<= 1;
        mov     QWORD PTR [rsp+264], rax        # %sfp, tmp4040
        vmovq   xmm20, QWORD PTR [rsp+264]      # i, %sfp
# testcase.c:14:   e = (7 & -d) << (7 & -(g & 7));
...

vmovq zeroes the high-order bits of zmm20 - and that's where the zeroes come
from.


$ 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-258852-checking-yes-rtl-df-extra-amd64/bin/../libexec/gcc/x86_64-pc-linux-gnu/8.0.1/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
--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-258852-checking-yes-rtl-df-extra-amd64
Thread model: posix
gcc version 8.0.1 20180326 (experimental) (GCC) 

Tested revisions:
r258852 - FAIL
7-branch r258647 - OK