[Bug middle-end/96175] New: Failure to optimize memory stores of double literals properly

[gabravier at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96175

            Bug ID: 96175
           Summary: Failure to optimize memory stores of double literals
                    properly
           Product: gcc
           Version: 11.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: middle-end
          Assignee: unassigned at gcc dot gnu.org
          Reporter: gabravier at gmail dot com
  Target Milestone: ---

void f(double *x)
{
    *x = 1.0;
}

With -O3, LLVM generates this :

f(double*): # @f(double*)
  movabs rax, 4607182418800017408
  mov qword ptr [rdi], rax
  ret

GCC generates this :

f(double*):
  mov rax, QWORD PTR .LC0[rip]
  mov QWORD PTR [rdi], rax
  ret
.LC0:
  .long 0
  .long 1072693248

This also occurs on every other architecture I tested (arm and powerpc64le,
though only with GCC 9). GCC is weirdly insistent on having a literal stored in
const data instead of just having it in the code, which seems inefficient.