Faster feature checks

Perform only a bit check instead of a much more expensive hash
lookup to test features.

For now I've just added a U32 to the cop structure to store the bits,
if we need more we could either add more bits directly, or make it a
pointer.

We don't have the immediate need for a pointer that warning do since
we don't dynamically add new features during compilation/runtime.

The changes to %^H are retained so that caller() can be used from perl
code to check the features enabled at a given caller's scope.

1 files changed, 4 insertions, 0 deletions

diff --git a/gv.c b/gv.c
index 05d80af0e8..3cb182eb01 100644
--- a/gv.c
+++ b/gv.c
@@ -2047,6 +2047,10 @@ S_gv_magicalize(pTHX_ GV *gv, HV *stash, const char *name, STRLEN len,
                 if (memEQs(name, len, "\005NCODING"))
 		    goto magicalize;
 		break;
+            case '\006':
+                if (memEQs(name, len, "\006EATURE_BITS"))
+		    goto magicalize;
+                break;
 	    case '\007':	/* $^GLOBAL_PHASE */
                 if (memEQs(name, len, "\007LOBAL_PHASE"))
 		    goto ro_magicalize;