[Bug fortran/71902] New: [5/6/7 Regression] Unneeded temporary on reallocatable character assignment

["tkoenig at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71902

            Bug ID: 71902
           Summary: [5/6/7 Regression] Unneeded temporary on reallocatable
                    character assignment
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: fortran
          Assignee: unassigned at gcc dot gnu.org
          Reporter: tkoenig at gcc dot gnu.org
  Target Milestone: ---

After the fix for PR 71783, the original code from Toon's test
case has an unnecessary temporary allocation. Translating

  character(len=ilen), allocatable :: cline(:)
  allocate(cline(2))
  cline(1) = 'a'
  cline(2) = cline(1)

yields


  BLOCK 
    symtree: '__var_1_trim'|| symbol: '__var_1_trim' 
      type spec : (CHARACTER () 1)
      attributes: (VARIABLE  ALLOCATABLE)
    symtree: 'block@3'     || symbol: 'block@3'      
      type spec : (UNKNOWN 0)
      attributes: (LABEL )
    ASSIGN block@3:__var_1_trim prtdata:cline(1)
    ASSIGN prtdata:cline(2) block@3:__var_1_trim
  END BLOCK 

This was not done in 4.9.  So, dependency handling can
be improved here.