sort compare subs: don't do unnecessary scope work

The 3 functions S_sortcv(), S_sortcv_stacked(), S_sortcv_xsub(),
which call a comparison function to compare $a and $b, do unnecessary work
with the scope and save stacks.

First, they pop any excess scope stack entries; but there shouldn't
be, since exiting the sort sub should have already pooped any inner
scopes. Indeed, running with an assert that PL_scopestack_ix == oldscopeix
didn't trigger any failures.

Secondly replace the unconditional leave_scope(oldsaveix) with
LEAVE_SCOPE(), which only calls the function if PL_savestack_ix >
oldsaveix.

1 files changed, 3 insertions, 15 deletions

diff --git a/pp_sort.c b/pp_sort.c
index 8e875122f0..02c5dd8fce 100644
--- a/pp_sort.c
+++ b/pp_sort.c
@@ -1773,7 +1773,6 @@ static I32
 S_sortcv(pTHX_ SV *const a, SV *const b)
 {
     const I32 oldsaveix = PL_savestack_ix;
-    const I32 oldscopeix = PL_scopestack_ix;
     I32 result;
     PMOP * const pm = PL_curpm;
     COP * const cop = PL_curcop;
@@ -1791,10 +1790,7 @@ S_sortcv(pTHX_ SV *const a, SV *const b)
     assert(PL_stack_sp > PL_stack_base || *PL_stack_base == &PL_sv_undef);
     result = SvIV(*PL_stack_sp);
 
-    while (PL_scopestack_ix > oldscopeix) {
-	LEAVE;
-    }
-    leave_scope(oldsaveix);
+    LEAVE_SCOPE(oldsaveix);
     PL_curpm = pm;
     return result;
 }
@@ -1803,7 +1799,6 @@ static I32
 S_sortcv_stacked(pTHX_ SV *const a, SV *const b)
 {
     const I32 oldsaveix = PL_savestack_ix;
-    const I32 oldscopeix = PL_scopestack_ix;
     I32 result;
     AV * const av = GvAV(PL_defgv);
     PMOP * const pm = PL_curpm;
@@ -1842,10 +1837,7 @@ S_sortcv_stacked(pTHX_ SV *const a, SV *const b)
     assert(PL_stack_sp > PL_stack_base || *PL_stack_base == &PL_sv_undef);
     result = SvIV(*PL_stack_sp);
 
-    while (PL_scopestack_ix > oldscopeix) {
-	LEAVE;
-    }
-    leave_scope(oldsaveix);
+    LEAVE_SCOPE(oldsaveix);
     PL_curpm = pm;
     return result;
 }
@@ -1855,7 +1847,6 @@ S_sortcv_xsub(pTHX_ SV *const a, SV *const b)
 {
     dSP;
     const I32 oldsaveix = PL_savestack_ix;
-    const I32 oldscopeix = PL_scopestack_ix;
     CV * const cv=MUTABLE_CV(PL_sortcop);
     I32 result;
     PMOP * const pm = PL_curpm;
@@ -1874,10 +1865,7 @@ S_sortcv_xsub(pTHX_ SV *const a, SV *const b)
     assert(PL_stack_sp > PL_stack_base || *PL_stack_base == &PL_sv_undef);
     result = SvIV(*PL_stack_sp);
 
-    while (PL_scopestack_ix > oldscopeix) {
-	LEAVE;
-    }
-    leave_scope(oldsaveix);
+    LEAVE_SCOPE(oldsaveix);
     PL_curpm = pm;
     return result;
 }