Replace run-time on-demand initialisation of PL_bitcount with a constant table.

(The table is 256 bytes; the run-time initialisation code is larger than this!)
Adapt generate_uudmap.c to generate the initalisation block for PL_bitcount,
writing the code to bitcount.h, using the same approach as uudmap.h.

To preserve binary compatibility:
for MULTIPLICITY:
  keep Ibitcount in the interpreter structure, but remove all the macros that
  access it. PL_bitcount is a new symbol in the object file, which won't clash
  with anything as that name wasn't used before.
otherwise:
  keep PL_bitcount as a char *, but initialise it at compile time to a new
  constant array PL_bitcount array. Remove the code that attempts to Safefree()
  it at interpreter destruction time.

1 files changed, 19 insertions, 0 deletions

diff --git a/perl.h b/perl.h
index 0e52ebca6b..66459b493c 100644
--- a/perl.h
+++ b/perl.h
@@ -4240,10 +4240,29 @@ EXTCONST char PL_uuemap[65]
 EXTCONST char PL_uudmap[256] =
 #include "uudmap.h"
 ;
+#  ifdef MULTIPLICITY
+/* There's no binary compatibility issue with adding a new global PL_bitcount,
+   because before this change, under MULTIPLICITY the pre-processor would have
+   been replacing the token PL_bitcount with an expression to access the
+   interpreter struct.  */
+EXTCONST char PL_bitcount[256] =
+#  else
+/* For binary compatibility, we can't replace the existing pointer PL_bitcount
+   with an array PL_bitcount.  So keep the existing variable, but make it point
+   to our compile-time generated array instead.  */
+EXTCONST char PL_bitcount_array[256] =
+#  endif
+#  include "bitcount.h"
+;
 EXTCONST char* const PL_sig_name[] = { SIG_NAME };
 EXTCONST int         PL_sig_num[]  = { SIG_NUM };
 #else
 EXTCONST char PL_uudmap[256];
+#  ifdef MULTIPLICITY
+EXTCONST char PL_bitcount[256];
+#  else
+EXTCONST char PL_bitcount_array[256];
+#  endif
 EXTCONST char* const PL_sig_name[];
 EXTCONST int         PL_sig_num[];
 #endif