[Bug rtl-optimization/40772] generating rendundant moves from second byte of 32b/64b register

[roger at nextmovesoftware dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=40772

Roger Sayle <roger at nextmovesoftware dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |FIXED
                 CC|                            |roger at nextmovesoftware dot com
   Target Milestone|---                         |7.0
             Status|UNCONFIRMED                 |RESOLVED

--- Comment #5 from Roger Sayle <roger at nextmovesoftware dot com> ---
This issue has been fixed since gcc 7; the compiler now stores the high-byte
register ah/bh/dh etc directly to memory.  The original tst2b.c testcase when
compiled with -O3 -march=k8 -fno-tree-vectorize looks like:
test:
.LFB0:
        .cfi_startproc
        leal    1(%rdi), %edx
        movl    %edi, %eax
        movb    %ah, data(%rip)
        addl    $15, %eax
        movb    %dh, data+1(%rip)
        leal    2(%rdi), %edx
        movb    %ah, data+15(%rip)
        movb    %dh, data+2(%rip)
        leal    3(%rdi), %edx
        movb    %dh, data+3(%rip)
        leal    4(%rdi), %edx
        movb    %dh, data+4(%rip)
        leal    5(%rdi), %edx
        movb    %dh, data+5(%rip)
        leal    6(%rdi), %edx
        movb    %dh, data+6(%rip)
        leal    7(%rdi), %edx
        movb    %dh, data+7(%rip)
        leal    8(%rdi), %edx
        movb    %dh, data+8(%rip)
        leal    9(%rdi), %edx
        movb    %dh, data+9(%rip)
        leal    10(%rdi), %edx
        movb    %dh, data+10(%rip)
        leal    11(%rdi), %edx
        movb    %dh, data+11(%rip)
        leal    12(%rdi), %edx
        movb    %dh, data+12(%rip)
        leal    13(%rdi), %edx
        movb    %dh, data+13(%rip)
        leal    14(%rdi), %edx
        movb    %dh, data+14(%rip)
        ret