[Bug target/106060] Inefficient constant broadcast on x86_64

[hjl.tools at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106060

--- Comment #2 from H.J. Lu <hjl.tools at gmail dot com> ---
Created attachment 53196
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=53196&action=edit
A patch

This generates:

0000000000000000 <shouldnt_have_movabs>:
   0:   b8 7b 00 00 00          mov    $0x7b,%eax
   5:   c5 f9 6e c0             vmovd  %eax,%xmm0
   9:   c4 e2 7d 78 c0          vpbroadcastb %xmm0,%ymm0
   e:   c3                      ret
   f:   90                      nop

0000000000000010 <should_be_cmpeq_abs>:
  10:   b8 01 00 00 00          mov    $0x1,%eax
  15:   c5 f9 6e c0             vmovd  %eax,%xmm0
  19:   c4 e2 7d 78 c0          vpbroadcastb %xmm0,%ymm0
  1e:   c3                      ret
  1f:   90                      nop

0000000000000020 <should_be_cmpeq_add>:
  20:   b8 fe ff ff ff          mov    $0xfffffffe,%eax
  25:   c5 f9 6e c0             vmovd  %eax,%xmm0
  29:   c4 e2 7d 78 c0          vpbroadcastb %xmm0,%ymm0
  2e:   c3                      ret