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.
Perl · tonycoz · Oct 30, 2019 · Oct 24, 2019 · Oct 28, 2019 · Oct 28, 2019
commit 576dc7fa89345f3ca2c4c5306cdc1744da770848
diff --git a/cop.h b/cop.h
@@ -413,6 +413,12 @@ struct cop {
     /* compile time state of %^H.  See the comment in op.c for how this is
        used to recreate a hash to return from caller.  */
     COPHH *	cop_hints_hash;
+    /* for now just a bitmask stored here.
+       If we get sufficient features this may become a pointer.
+       How these flags are stored is subject to change without
+       notice.  Use the macros to test for features.
+    */
+    U32		cop_features;
 };
 
 #ifdef USE_ITHREADS

diff --git a/feature.h b/feature.h
@@ -12,6 +12,20 @@
 
 #define HINT_FEATURE_SHIFT	26
 
+#define FEATURE_BITWISE_BIT         0x0001
+#define FEATURE___SUB___BIT         0x0002
+#define FEATURE_MYREF_BIT           0x0004
+#define FEATURE_EVALBYTES_BIT       0x0008
+#define FEATURE_FC_BIT              0x0010
+#define FEATURE_POSTDEREF_QQ_BIT    0x0020
+#define FEATURE_REFALIASING_BIT     0x0040
+#define FEATURE_SAY_BIT             0x0080
+#define FEATURE_SIGNATURES_BIT      0x0100
+#define FEATURE_STATE_BIT           0x0200
+#define FEATURE_SWITCH_BIT          0x0400
+#define FEATURE_UNIEVAL_BIT         0x0800
+#define FEATURE_UNICODE_BIT         0x1000
+
 #define FEATURE_BUNDLE_DEFAULT	0
 #define FEATURE_BUNDLE_510	1
 #define FEATURE_BUNDLE_511	2
@@ -31,6 +45,11 @@
 	((CURRENT_HINTS							 \
 	   & HINT_LOCALIZE_HH)						  \
 	    ? Perl_feature_is_enabled(aTHX_ STR_WITH_LEN(name)) : FALSE)
+
+#define FEATURE_IS_ENABLED_MASK(mask)                   \
+  ((CURRENT_HINTS & HINT_LOCALIZE_HH)                \
+    ? (PL_curcop->cop_features & (mask)) : FALSE)
+
 /* The longest string we pass in.  */
 #define MAX_FEATURE_LEN (sizeof("postderef_qq")-1)
 
@@ -39,99 +58,112 @@
 	(CURRENT_FEATURE_BUNDLE >= FEATURE_BUNDLE_515 && \
 	 CURRENT_FEATURE_BUNDLE <= FEATURE_BUNDLE_527) \
      || (CURRENT_FEATURE_BUNDLE == FEATURE_BUNDLE_CUSTOM && \
-	 FEATURE_IS_ENABLED("fc")) \
+	 FEATURE_IS_ENABLED_MASK(FEATURE_FC_BIT)) \
     )
 
 #define FEATURE_SAY_IS_ENABLED \
     ( \
 	(CURRENT_FEATURE_BUNDLE >= FEATURE_BUNDLE_510 && \
 	 CURRENT_FEATURE_BUNDLE <= FEATURE_BUNDLE_527) \
      || (CURRENT_FEATURE_BUNDLE == FEATURE_BUNDLE_CUSTOM && \
-	 FEATURE_IS_ENABLED("say")) \
+	 FEATURE_IS_ENABLED_MASK(FEATURE_SAY_BIT)) \
     )
 
 #define FEATURE_STATE_IS_ENABLED \
     ( \
 	(CURRENT_FEATURE_BUNDLE >= FEATURE_BUNDLE_510 && \
 	 CURRENT_FEATURE_BUNDLE <= FEATURE_BUNDLE_527) \
      || (CURRENT_FEATURE_BUNDLE == FEATURE_BUNDLE_CUSTOM && \
-	 FEATURE_IS_ENABLED("state")) \
+	 FEATURE_IS_ENABLED_MASK(FEATURE_STATE_BIT)) \
     )
 
 #define FEATURE_SWITCH_IS_ENABLED \
     ( \
 	(CURRENT_FEATURE_BUNDLE >= FEATURE_BUNDLE_510 && \
 	 CURRENT_FEATURE_BUNDLE <= FEATURE_BUNDLE_527) \
      || (CURRENT_FEATURE_BUNDLE == FEATURE_BUNDLE_CUSTOM && \
-	 FEATURE_IS_ENABLED("switch")) \
+	 FEATURE_IS_ENABLED_MASK(FEATURE_SWITCH_BIT)) \
     )
 
 #define FEATURE_BITWISE_IS_ENABLED \
     ( \
 	CURRENT_FEATURE_BUNDLE == FEATURE_BUNDLE_527 \
      || (CURRENT_FEATURE_BUNDLE == FEATURE_BUNDLE_CUSTOM && \
-	 FEATURE_IS_ENABLED("bitwise")) \
+	 FEATURE_IS_ENABLED_MASK(FEATURE_BITWISE_BIT)) \
     )
 
 #define FEATURE_EVALBYTES_IS_ENABLED \
     ( \
 	(CURRENT_FEATURE_BUNDLE >= FEATURE_BUNDLE_515 && \
 	 CURRENT_FEATURE_BUNDLE <= FEATURE_BUNDLE_527) \
      || (CURRENT_FEATURE_BUNDLE == FEATURE_BUNDLE_CUSTOM && \
-	 FEATURE_IS_ENABLED("evalbytes")) \
+	 FEATURE_IS_ENABLED_MASK(FEATURE_EVALBYTES_BIT)) \
     )
 
 #define FEATURE_SIGNATURES_IS_ENABLED \
     ( \
 	CURRENT_FEATURE_BUNDLE == FEATURE_BUNDLE_CUSTOM && \
-	 FEATURE_IS_ENABLED("signatures") \
+	 FEATURE_IS_ENABLED_MASK(FEATURE_SIGNATURES_BIT) \
     )
 
 #define FEATURE___SUB___IS_ENABLED \
     ( \
 	(CURRENT_FEATURE_BUNDLE >= FEATURE_BUNDLE_515 && \
 	 CURRENT_FEATURE_BUNDLE <= FEATURE_BUNDLE_527) \
      || (CURRENT_FEATURE_BUNDLE == FEATURE_BUNDLE_CUSTOM && \
-	 FEATURE_IS_ENABLED("__SUB__")) \
+	 FEATURE_IS_ENABLED_MASK(FEATURE___SUB___BIT)) \
     )
 
 #define FEATURE_REFALIASING_IS_ENABLED \
     ( \
 	CURRENT_FEATURE_BUNDLE == FEATURE_BUNDLE_CUSTOM && \
-	 FEATURE_IS_ENABLED("refaliasing") \
+	 FEATURE_IS_ENABLED_MASK(FEATURE_REFALIASING_BIT) \
     )
 
 #define FEATURE_POSTDEREF_QQ_IS_ENABLED \
     ( \
 	(CURRENT_FEATURE_BUNDLE >= FEATURE_BUNDLE_523 && \
 	 CURRENT_FEATURE_BUNDLE <= FEATURE_BUNDLE_527) \
      || (CURRENT_FEATURE_BUNDLE == FEATURE_BUNDLE_CUSTOM && \
-	 FEATURE_IS_ENABLED("postderef_qq")) \
+	 FEATURE_IS_ENABLED_MASK(FEATURE_POSTDEREF_QQ_BIT)) \
     )
 
 #define FEATURE_UNIEVAL_IS_ENABLED \
     ( \
 	(CURRENT_FEATURE_BUNDLE >= FEATURE_BUNDLE_515 && \
 	 CURRENT_FEATURE_BUNDLE <= FEATURE_BUNDLE_527) \
      || (CURRENT_FEATURE_BUNDLE == FEATURE_BUNDLE_CUSTOM && \
-	 FEATURE_IS_ENABLED("unieval")) \
+	 FEATURE_IS_ENABLED_MASK(FEATURE_UNIEVAL_BIT)) \
     )
 
 #define FEATURE_MYREF_IS_ENABLED \
     ( \
 	CURRENT_FEATURE_BUNDLE == FEATURE_BUNDLE_CUSTOM && \
-	 FEATURE_IS_ENABLED("myref") \
+	 FEATURE_IS_ENABLED_MASK(FEATURE_MYREF_BIT) \
     )
 
 #define FEATURE_UNICODE_IS_ENABLED \
     ( \
 	(CURRENT_FEATURE_BUNDLE >= FEATURE_BUNDLE_511 && \
 	 CURRENT_FEATURE_BUNDLE <= FEATURE_BUNDLE_527) \
      || (CURRENT_FEATURE_BUNDLE == FEATURE_BUNDLE_CUSTOM && \
-	 FEATURE_IS_ENABLED("unicode")) \
+	 FEATURE_IS_ENABLED_MASK(FEATURE_UNICODE_BIT)) \
     )
 
 
+#define SAVEFEATUREBITS() SAVEI32(PL_compiling.cop_features)
+
+#define CLEARFEATUREBITS() (PL_compiling.cop_features = 0)
+
+#define STOREFEATUREBITSHH(hh) \
+  (hv_stores((hh), "feature/bits", newSVuv(PL_compiling.cop_features)))
+
+#define FETCHFEATUREBITSHH(hh)                              \
+  STMT_START {                                              \
+      SV **fbsv = hv_fetchs((hh), "feature/bits", FALSE);   \
+      PL_compiling.cop_features = fbsv ? SvUV(*fbsv) : 0;   \
+  } STMT_END
+
 #endif /* PERL_CORE or PERL_EXT */
 
 #ifdef PERL_IN_OP_C

diff --git 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;

diff --git a/lib/feature.pm b/lib/feature.pm
@@ -5,7 +5,7 @@
 
 package feature;
 
-our $VERSION = '1.55';
+our $VERSION = '1.56';
 
 our %feature = (
     fc              => 'feature_fc',
@@ -23,6 +23,23 @@ our %feature = (
     unicode_strings => 'feature_unicode',
 );
 
+
+my %feature_bits = (
+    bitwise         => 0x0001,
+    current_sub     => 0x0002,
+    declared_refs   => 0x0004,
+    evalbytes       => 0x0008,
+    fc              => 0x0010,
+    postderef_qq    => 0x0020,
+    refaliasing     => 0x0040,
+    say             => 0x0080,
+    signatures      => 0x0100,
+    state           => 0x0200,
+    switch          => 0x0400,
+    unicode_eval    => 0x0800,
+    unicode_strings => 0x1000,
+);
+
 our %feature_bundle = (
     "5.10"    => [qw(say state switch)],
     "5.11"    => [qw(say state switch unicode_strings)],
@@ -485,14 +502,17 @@ sub __common {
     my $import = shift;
     my $bundle_number = $^H & $hint_mask;
     my $features = $bundle_number != $hint_mask
-	&& $feature_bundle{$hint_bundles[$bundle_number >> $hint_shift]};
+      && $feature_bundle{$hint_bundles[$bundle_number >> $hint_shift]};
+    my $bits = ${^FEATURE_BITS};
     if ($features) {
 	# Features are enabled implicitly via bundle hints.
 	# Delete any keys that may be left over from last time.
 	delete @^H{ values(%feature) };
+        $bits = 0;
 	$^H |= $hint_mask;
 	for (@$features) {
 	    $^H{$feature{$_}} = 1;
+            $bits |= $feature_bits{$_};
 	    $^H |= $hint_uni8bit if $_ eq 'unicode_strings';
 	}
     }
@@ -520,12 +540,15 @@ sub __common {
         }
 	if ($import) {
 	    $^H{$feature{$name}} = 1;
+            $bits |= $feature_bits{$name};
 	    $^H |= $hint_uni8bit if $name eq 'unicode_strings';
 	} else {
             delete $^H{$feature{$name}};
+            $bits &= ~$feature_bits{$name};
             $^H &= ~ $hint_uni8bit if $name eq 'unicode_strings';
         }
     }
+    ${^FEATURE_BITS} = $bits;
 }
 
 sub unknown_feature {

diff --git a/mg.c b/mg.c
@@ -1032,7 +1032,12 @@ Perl_magic_get(pTHX_ SV *sv, MAGIC *mg)
 	break;
 
     case '\006':		/* ^F */
-	sv_setiv(sv, (IV)PL_maxsysfd);
+        if (nextchar == '\0') {
+            sv_setiv(sv, (IV)PL_maxsysfd);
+        }
+        else if (strEQ(remaining, "EATURE_BITS")) {
+            sv_setuv(sv, PL_compiling.cop_features);
+        }
 	break;
     case '\007':		/* ^GLOBAL_PHASE */
 	if (strEQ(remaining, "LOBAL_PHASE")) {
@@ -2840,7 +2845,12 @@ Perl_magic_set(pTHX_ SV *sv, MAGIC *mg)
             Perl_croak(aTHX_ "${^ENCODING} is no longer supported");
 	break;
     case '\006':	/* ^F */
-	PL_maxsysfd = SvIV(sv);
+        if (mg->mg_ptr[1] == '\0') {
+            PL_maxsysfd = SvIV(sv);
+        }
+        else if (strEQ(mg->mg_ptr + 1, "EATURE_BITS")) {
+            PL_compiling.cop_features = SvUV(sv);
+        }
 	break;
     case '\010':	/* ^H */
         {

diff --git a/op.c b/op.c
@@ -11851,8 +11851,10 @@ Perl_ck_eval(pTHX_ OP *o)
     if ((PL_hints & HINT_LOCALIZE_HH) != 0
      && !(o->op_private & OPpEVAL_COPHH) && GvHV(PL_hintgv)) {
 	/* Store a copy of %^H that pp_entereval can pick up. */
-	OP *hhop = newSVOP(OP_HINTSEVAL, 0,
-			   MUTABLE_SV(hv_copy_hints_hv(GvHV(PL_hintgv))));
+        HV *hh = hv_copy_hints_hv(GvHV(PL_hintgv));
+	OP *hhop;
+        STOREFEATUREBITSHH(hh);
+        hhop = newSVOP(OP_HINTSEVAL, 0, MUTABLE_SV(hh));
         /* append hhop to only child  */
         op_sibling_splice(o, cUNOPo->op_first, 0, hhop);
 

diff --git a/pp_ctl.c b/pp_ctl.c
@@ -33,6 +33,7 @@
 #include "EXTERN.h"
 #define PERL_IN_PP_CTL_C
 #include "perl.h"
+#include "feature.h"
 
 #define RUN_PP_CATCHABLY(thispp) \
     STMT_START { if (CATCH_GET) return docatch(thispp); } STMT_END
@@ -3485,6 +3486,7 @@ S_doeval_compile(pTHX_ U8 gimme, CV* outside, U32 seq, HV *hh)
     if (clear_hints) {
 	PL_hints = 0;
 	hv_clear(GvHV(PL_hintgv));
+        CLEARFEATUREBITS();
     }
     else {
 	PL_hints = saveop->op_private & OPpEVAL_COPHH
@@ -3502,6 +3504,7 @@ S_doeval_compile(pTHX_ U8 gimme, CV* outside, U32 seq, HV *hh)
 	    /* SAVEHINTS created a new HV in PL_hintgv, which we need to GC */
 	    SvREFCNT_dec(GvHV(PL_hintgv));
 	    GvHV(PL_hintgv) = hh;
+            FETCHFEATUREBITSHH(hh);
 	}
     }
     SAVECOMPILEWARNINGS();