[Bug rtl-optimization/59754] New: [ree.c] Incorrect merge while working with vector registers

[kirill.yukhin at intel dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59754

            Bug ID: 59754
           Summary: [ree.c] Incorrect merge while working with vector
                    registers
           Product: gcc
           Version: 4.9.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: rtl-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: kirill.yukhin at intel dot com

Hello,
It seems that this revision:
git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@206418
138bc75d-0d04-0410-961f-82ee72b054a4

made bunch of AVX-512F tests failing (at runtime):

The difference in assembler is as following.

For good (prev. rev., testname: gcc.target/i386/avx512f-vpmovzxwd-2.c):
...
        vmovdqa 160(%esp), %ymm0
        movl    $-22854, %eax
        leal    384(%esp), %ebx
        kmovw   %eax, %k1
        xorl    %edx, %edx
        vpmovzxwd       %ymm0, %zmm1
        vmovdqa64       %zmm1, 192(%esp)
        vmovdqa64       256(%esp), %zmm1
        vpmovzxwd       %ymm0, %zmm1{%k1}
        vpmovzxwd       %ymm0, %zmm0{%k1}{z}
        vmovdqa64       %zmm1, 256(%esp)
        vmovdqa64       %zmm0, 320(%esp)
...

For broken:
...
        vpmovzxwd       160(%esp), %zmm1
        movl    $-22854, %eax
        leal    384(%esp), %ebx
        kmovw   %eax, %k1
        xorl    %edx, %edx
        vmovdqa64       %zmm1, %zmm0
        vmovdqa64       %zmm1, 192(%esp)
        vmovdqa64       256(%esp), %zmm1
        vpmovzxwd       %ymm0, %zmm1{%k1}
        vpmovzxwd       %ymm0, %zmm0{%k1}{z}
        vmovdqa64       %zmm1, 256(%esp)
        vmovdqa64       %zmm0, 320(%esp)
...


So it seems that it is allowed to convert:
  (set r0 [mem])
  (set r1 sign_extend (r0))

to:
  (set r1 sign_extend ([mem]))
  (set r0 r1)

IMHO this should work with scalar, but not with vectors.
I suspect eliminating such extends for vector types were
prohibited initially.