[Bug c++/91840] New: Support for #pragma unroll (N)

[david.bolvansky at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91840

            Bug ID: 91840
           Summary: Support for #pragma unroll (N)
           Product: gcc
           Version: 10.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: david.bolvansky at gmail dot com
  Target Milestone: ---

Clang/ICC supports #pragma unroll (N) and it would be good if GCC too, so we
don't have to write macros to workaround it and to keep the code buildable by
all tree compilers.

This should not be so hard, since GCC already has #pragma GCC unroll (N).

void unroll(int a[], int b[], int c[], int d[]) {
  #pragma unroll(4)
  for (int i = 1; i < 100; i++) {
    b[i] = a[i] + 1;
    d[i] = c[i] + 1;
  }
}