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, 2 insertions, 0 deletions

diff --git a/scope.c b/scope.c
index c6616440f6..35f510ea06 100644
--- a/scope.c
+++ b/scope.c
@@ -25,6 +25,7 @@
 #include "EXTERN.h"
 #define PERL_IN_SCOPE_C
 #include "perl.h"
+#include "feature.h"
 
 SV**
 Perl_stack_grow(pTHX_ SV **sp, SV **p, SSize_t n)
@@ -688,6 +689,7 @@ Perl_save_hints(pTHX)
 	save_pushptri32ptr(oldhh, PL_hints, save_cophh, SAVEt_HINTS);
 	GvHV(PL_hintgv) = NULL; /* in case copying dies */
 	GvHV(PL_hintgv) = hv_copy_hints_hv(oldhh);
+        SAVEFEATUREBITS();
     } else {
 	save_pushi32ptr(PL_hints, save_cophh, SAVEt_HINTS);
     }