[Bug c++/90784] New: A loop inside a constexpr function in a constexpr context is not evaluated at compile time

[wandersys at aim dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90784

            Bug ID: 90784
           Summary: A loop inside a constexpr function in a constexpr
                    context is not evaluated at compile time
           Product: gcc
           Version: 9.1.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: wandersys at aim dot com
  Target Milestone: ---

Created attachment 46461
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=46461&action=edit
constexpr context evaluated in runtime

If constexpr function contains a loop and even if it is used in the constexpr
context, the loop inside it still evaluated in runtime.

Observed on GCC 9.1. GCC 8.x - OK. CLang - OK.

ASM code on godbolt: https://godbolt.org/z/2dxEV7

Example code in attachment.