(UN)LIKELY branch prediction hints in a few strategic places

This adds branch prediction hints to a few strategic places such as
growing stack or strings, some exception handling, and a few hot
functions such as sv_upgrade.

This is not exhaustive by any means.

4 files changed, 17 insertions, 17 deletions

diff --git a/inline.h b/inline.h
index 6b5f93c777..6cdfe9f178 100644
--- a/inline.h
+++ b/inline.h
@@ -46,7 +46,7 @@ S_ReANY(const REGEXP * const re)
 PERL_STATIC_INLINE SV *
 S_SvREFCNT_inc(SV *sv)
 {
-    if (sv)
+    if (LIKELY(sv != NULL))
 	SvREFCNT(sv)++;
     return sv;
 }
@@ -59,13 +59,13 @@ S_SvREFCNT_inc_NN(SV *sv)
 PERL_STATIC_INLINE void
 S_SvREFCNT_inc_void(SV *sv)
 {
-    if (sv)
+    if (LIKELY(sv != NULL))
 	SvREFCNT(sv)++;
 }
 PERL_STATIC_INLINE void
 S_SvREFCNT_dec(pTHX_ SV *sv)
 {
-    if (sv) {
+    if (LIKELY(sv != NULL)) {
 	U32 rc = SvREFCNT(sv);
 	if (rc > 1)
 	    SvREFCNT(sv) = rc - 1;
diff --git a/perl.h b/perl.h
index 4b020c7a7b..5639f1cb74 100644
--- a/perl.h
+++ b/perl.h
@@ -568,9 +568,9 @@ struct op *Perl_op asm(stringify(OP_IN_REGISTER));
 #else
 #   define TAINT		(PL_tainted = TRUE)
 #   define TAINT_NOT	(PL_tainted = FALSE)
-#   define TAINT_IF(c)	if (c) { PL_tainted = TRUE; }
-#   define TAINT_ENV()	if (PL_tainting) { taint_env(); }
-#   define TAINT_PROPER(s)	if (PL_tainting) { taint_proper(NULL, s); }
+#   define TAINT_IF(c)	if (UNLIKELY(c)) { PL_tainted = TRUE; }
+#   define TAINT_ENV()	if (UNLIKELY(PL_tainting)) { taint_env(); }
+#   define TAINT_PROPER(s)	if (UNLIKELY(PL_tainting)) { taint_proper(NULL, s); }
 #   define TAINT_set(s)		(PL_tainted = (s))
 #   define TAINT_get		(PL_tainted)
 #   define TAINTING_get		(PL_tainting)
diff --git a/pp.h b/pp.h
index 377d489f26..cb6a0668f9 100644
--- a/pp.h
+++ b/pp.h
@@ -278,15 +278,15 @@ Does not use C<TARG>.  See also C<XPUSHu>, C<mPUSHu> and C<PUSHu>.
 =cut
 */
 
-#define EXTEND(p,n)	(void)(PL_stack_max - p < (int)(n) &&		\
+#define EXTEND(p,n)    (void)(UNLIKELY(PL_stack_max - p < (int)(n)) &&         \
 			    (sp = stack_grow(sp,p, (int) (n))))
 
 /* Same thing, but update mark register too. */
-#define MEXTEND(p,n)	STMT_START {if (PL_stack_max - p < (int)(n)) {	\
-			    const int markoff = mark - PL_stack_base;	\
-			    sp = stack_grow(sp,p,(int) (n));		\
-			    mark = PL_stack_base + markoff;		\
-			} } STMT_END
+#define MEXTEND(p,n)   STMT_START {if (UNLIKELY(PL_stack_max - p < (int)(n))) {\
+                           const int markoff = mark - PL_stack_base;           \
+                           sp = stack_grow(sp,p,(int) (n));                    \
+                           mark = PL_stack_base + markoff;                     \
+                       } } STMT_END
 
 #define PUSHs(s)	(*++sp = (s))
 #define PUSHTARG	STMT_START { SvSETMAGIC(TARG); PUSHs(TARG); } STMT_END
@@ -388,7 +388,7 @@ Does not use C<TARG>.  See also C<XPUSHu>, C<mPUSHu> and C<PUSHu>.
 
 #define EXTEND_MORTAL(n) \
     STMT_START {							\
-	if (PL_tmps_ix + (n) >= PL_tmps_max)				\
+	if (UNLIKELY(PL_tmps_ix + (n) >= PL_tmps_max))			\
 	    tmps_grow(n);						\
     } STMT_END
 
diff --git a/sv.c b/sv.c
index f58389bb4c..3f68d9c1fa 100644
--- a/sv.c
+++ b/sv.c
@@ -1246,12 +1246,12 @@ Perl_sv_upgrade(pTHX_ SV *const sv, svtype new_type)
 	assert(!SvPAD_TYPED(sv));
 	break;
     default:
-	if (old_type_details->cant_upgrade)
+	if (UNLIKELY(old_type_details->cant_upgrade))
 	    Perl_croak(aTHX_ "Can't upgrade %s (%" UVuf ") to %" UVuf,
 		       sv_reftype(sv, 0), (UV) old_type, (UV) new_type);
     }
 
-    if (old_type > new_type)
+    if (UNLIKELY(old_type > new_type))
 	Perl_croak(aTHX_ "sv_upgrade from type %d down to type %d",
 		(int)old_type, (int)new_type);
 
@@ -1386,7 +1386,7 @@ Perl_sv_upgrade(pTHX_ SV *const sv, svtype new_type)
 	    SvNV_set(sv, 0);
 #endif
 
-	if (new_type == SVt_PVIO) {
+	if (UNLIKELY(new_type == SVt_PVIO)) {
 	    IO * const io = MUTABLE_IO(sv);
 	    GV *iogv = gv_fetchpvs("IO::File::", GV_ADD, SVt_PVHV);
 
@@ -1399,7 +1399,7 @@ Perl_sv_upgrade(pTHX_ SV *const sv, svtype new_type)
 	    SvSTASH_set(io, MUTABLE_HV(SvREFCNT_inc(GvHV(iogv))));
 	    IoPAGE_LEN(sv) = 60;
 	}
-	if (new_type == SVt_REGEXP)
+	if (UNLIKELY(new_type == SVt_REGEXP))
 	    sv->sv_u.svu_rx = (regexp *)new_body;
 	else if (old_type < SVt_PV) {
 	    /* referant will be NULL unless the old type was SVt_IV emulating