Performance issue with data frames with non-double columns

[Enchufa2]

Reported here. With the script attached,

$ perf record -F 99 Rscript test.R
$ perf report
Samples: 4K of event 'cycles:uppp', Event count (approx.): 149446301773
Overhead  Command  Shared Object        Symbol
  62,42%  R        libR.so              [.] Rf_coerceVector
   7,66%  R        libR.so              [.] 0x0000000000174cb8
   3,35%  R        libc-2.28.so         [.] __memcmp_avx2_movbe

The call to Rf_coerceVector kills the performance.