Change S_ckwarn_common() to looping over the packed warning value.

The core never uses WARN3() or WARN4(), and rarely uses WARN2(), so the
previous code, effectively an unwrapped loop, wasn't a speed up. Functionally
equivalent smaller code fits better into CPU caches.

3 files changed, 22 insertions, 7 deletions

diff --git a/util.c b/util.c
index 13b56a0802..b72f263dc5 100644
--- a/util.c
+++ b/util.c
@@ -1627,15 +1627,26 @@ S_ckwarn_common(pTHX_ U32 w)
     if (PL_curcop->cop_warnings == pWARN_NONE)
 	return FALSE;
 
+    /* Check the assumption that at least the first slot is non-zero.  */
+    assert(unpackWARN1(w));
+
+    /* Check the assumption that it is valid to stop as soon as a zero slot is
+       seen.  */
+    if (!unpackWARN2(w)) {
+	assert(!unpackWARN3(w));
+	assert(!unpackWARN4(w));
+    } else if (!unpackWARN3(w)) {
+	assert(!unpackWARN4(w));
+    }
+	
     /* Right, dealt with all the special cases, which are implemented as non-
        pointers, so there is a pointer to a real warnings mask.  */
-    return isWARN_on(PL_curcop->cop_warnings, unpackWARN1(w))
-	|| (unpackWARN2(w) &&
-	    isWARN_on(PL_curcop->cop_warnings, unpackWARN2(w)))
-	|| (unpackWARN3(w) &&
-	    isWARN_on(PL_curcop->cop_warnings, unpackWARN3(w)))
-	|| (unpackWARN4(w) &&
-	    isWARN_on(PL_curcop->cop_warnings, unpackWARN4(w)));
+    do {
+	if (isWARN_on(PL_curcop->cop_warnings, unpackWARN1(w)))
+	    return TRUE;
+    } while (w >>= WARNshift);
+
+    return FALSE;
 }
 
 /* Set buffer=NULL to get a new one.  */
diff --git a/warnings.h b/warnings.h
index 8f891a7511..56b307912d 100644
--- a/warnings.h
+++ b/warnings.h
@@ -105,6 +105,8 @@
 #define ckWARN3_d(w1,w2,w3)	Perl_ckwarn_d(aTHX_ packWARN3(w1,w2,w3))
 #define ckWARN4_d(w1,w2,w3,w4)	Perl_ckwarn_d(aTHX_ packWARN4(w1,w2,w3,w4))
 
+#define WARNshift		8
+
 #define packWARN(a)		(a                                      )
 #define packWARN2(a,b)		((a) | ((b)<<8)                         )
 #define packWARN3(a,b,c)	((a) | ((b)<<8) | ((c)<<16)             )
diff --git a/warnings.pl b/warnings.pl
index 6bd611b604..dabc97d63a 100644
--- a/warnings.pl
+++ b/warnings.pl
@@ -353,6 +353,8 @@ print $warn <<'EOM';
 #define ckWARN3_d(w1,w2,w3)	Perl_ckwarn_d(aTHX_ packWARN3(w1,w2,w3))
 #define ckWARN4_d(w1,w2,w3,w4)	Perl_ckwarn_d(aTHX_ packWARN4(w1,w2,w3,w4))
 
+#define WARNshift		8
+
 #define packWARN(a)		(a                                      )
 #define packWARN2(a,b)		((a) | ((b)<<8)                         )
 #define packWARN3(a,b,c)	((a) | ((b)<<8) | ((c)<<16)             )