[Bug c++/86573] New: Failure to optimise passing simple values to inlined function

[s_gccbugzilla at nedprod dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86573

            Bug ID: 86573
           Summary: Failure to optimise passing simple values to inlined
                    function
           Product: gcc
           Version: tree-ssa
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: s_gccbugzilla at nedprod dot com
  Target Milestone: ---

#include <string>

inline size_t calc(std::string a, std::string b)
{
    return a.size() + b.size();
}

int main()
{
    std::string a = "Hello world", b = "Goodbye world";
    return calc(std::move(a), std::move(b));
}

This should generate:

main:                                   # @main
        mov     eax, 24
        ret

Like clang does. See https://godbolt.org/g/EAggKH.

But it instead generates this spew with gcc trunk:

https://godbolt.org/g/3LmfTc

Also it should generate the above return of 24 if passing by value. clang
currently fails that, I have reported a bug to them about it.