[Bug target/103731] New: 390: inefficient 64-bit constant generation

[jens.seifert at de dot ibm.com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103731

            Bug ID: 103731
           Summary: 390: inefficient 64-bit constant generation
           Product: gcc
           Version: 8.3.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: jens.seifert at de dot ibm.com
  Target Milestone: ---

unsigned long long M8()
{
   return 0x8888888888888888;
}

Generates:

.LC0:
        .quad   0x8888888888888888
.text
        .align  8
.globl _Z2M8v
        .type   _Z2M8v, @function
_Z2M8v:
.LFB0:
        .cfi_startproc
        lgrl    %r2,.LC0
        br      %r14
        .cfi_endproc

Expected 2 instructions:
load immediate + insert immedate(IIHF) instead of LOAD