[Bug target/94650] Missed x86-64 peephole optimization: x >= large power of two

[ubizjak at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94650

Uroš Bizjak <ubizjak at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Assignee|unassigned at gcc dot gnu.org      |ubizjak at gmail dot com
             Status|NEW                         |ASSIGNED

--- Comment #2 from Uroš Bizjak <ubizjak at gmail dot com> ---
Created attachment 48315
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=48315&action=edit
Prototype patch

Using this patch, the following asm is created (-O2):

--cut here--
check:
        xorl    %eax, %eax
        shrq    $40, %rdi
        setne   %al
        ret

test0:
        shrq    $40, %rdi
        jne     .L5
        ret
.L5:
        xorl    %edi, %edi
        jmp     g

test1:
        movq    %rdi, %rax
        shrq    $40, %rax
        jne     .L8
        ret
.L8:
        jmp     g
--cut here--