refactor Perl_leave_scope

This is a large and hot function. The main problem with it is that
there is code to pop a few args repeated in just about every branch.
Also, there are a whole bunch of local vars (sv, av, hv, gv etc)
that are never all used simultaneously, but are really just there for
casting convenience. Together, they defeat the compiler's register
allocation algorithms (well, they did for gcc anyway).

We fix this by just declaring three general vars, arg0,1,2 of type ANY, and
move the popping code to above the switch(). We sort the SAVEt_*
indices in order of number of args, so it's quick to determine how many
args we need to pop for a particular type.

Together with the previous commits which added the SS_ADD_* macros, this
reduces the size of scope.o (-O2, gcc x86_64) by about 9% (threaded)
or 17% (unthreaded), and seems to speed up simple loops / function calls
by around 5%.

1 files changed, 71 insertions, 52 deletions

diff --git a/scope.h b/scope.h
index 5854850e4c..22c728d1be 100644
--- a/scope.h
+++ b/scope.h
@@ -8,58 +8,77 @@
  *
  */
 
-#define SAVEt_ITEM		0
-#define SAVEt_SV		1
-#define SAVEt_AV		2
-#define SAVEt_HV		3
-#define SAVEt_INT		4
-#define SAVEt_LONG		5
-#define SAVEt_I32		6
-#define SAVEt_IV		7
-#define SAVEt_SPTR		8
-#define SAVEt_APTR		9
-#define SAVEt_HPTR		10
-#define SAVEt_PPTR		11
-#define SAVEt_NSTAB		12
-#define SAVEt_SVREF		13
-#define SAVEt_GP		14
-#define SAVEt_FREESV		15
-#define SAVEt_FREEOP		16
-#define SAVEt_FREEPV		17
-#define SAVEt_CLEARSV		18
-#define SAVEt_DELETE		19
-#define SAVEt_DESTRUCTOR	20
-#define SAVEt_REGCONTEXT	21
-#define SAVEt_STACK_POS		22
-#define SAVEt_I16		23
-#define SAVEt_AELEM		24
-#define SAVEt_HELEM		25
-#define SAVEt_OP		26
-#define SAVEt_HINTS		27
-#define SAVEt_ALLOC		28
-#define SAVEt_GENERIC_SVREF	29
-#define SAVEt_DESTRUCTOR_X	30
-#define SAVEt_VPTR		31
-#define SAVEt_I8		32
-#define SAVEt_COMPPAD		33
-#define SAVEt_GENERIC_PVREF	34
-#define SAVEt_PADSV_AND_MORTALIZE	35
-#define SAVEt_MORTALIZESV	36
-#define SAVEt_SHARED_PVREF	37
-#define SAVEt_BOOL		38
-#define SAVEt_SET_SVFLAGS	39
-#define SAVEt_SAVESWITCHSTACK	40
-#define SAVEt_RE_STATE		42
-#define SAVEt_COMPILE_WARNINGS	43
-#define SAVEt_STACK_CXPOS	44
-#define SAVEt_PARSER		45
-#define SAVEt_ADELETE		46
-#define SAVEt_I32_SMALL		47
-#define SAVEt_INT_SMALL		48
-#define SAVEt_GVSV		49
-#define SAVEt_FREECOPHH		50
-#define SAVEt_CLEARPADRANGE	51
-#define SAVEt_GVSLOT		52
+/* *** these are ordered by number of of auto-popped args */
+
+/* zero args */
+
+#define SAVEt_ALLOC		0
+#define SAVEt_CLEARPADRANGE	1
+#define SAVEt_CLEARSV		2
+#define SAVEt_REGCONTEXT	3
+#define SAVEt_RE_STATE		4
+
+#define SAVEt_ARG0_MAX		4
+
+/* one arg */
+
+#define SAVEt_BOOL		5
+#define SAVEt_COMPILE_WARNINGS	6
+#define SAVEt_COMPPAD		7
+#define SAVEt_FREECOPHH		8
+#define SAVEt_FREEOP		9
+#define SAVEt_FREEPV		10
+#define SAVEt_FREESV		11
+#define SAVEt_I16		12
+#define SAVEt_I32_SMALL		13
+#define SAVEt_I8		14
+#define SAVEt_INT_SMALL		15
+#define SAVEt_MORTALIZESV	16
+#define SAVEt_NSTAB		17
+#define SAVEt_OP		18
+#define SAVEt_PARSER		19
+#define SAVEt_STACK_POS		20
+
+#define SAVEt_ARG1_MAX		20
+
+/* two args */
+
+#define SAVEt_ADELETE		21
+#define SAVEt_APTR		22
+#define SAVEt_AV		23
+#define SAVEt_DESTRUCTOR	24
+#define SAVEt_DESTRUCTOR_X	25
+#define SAVEt_GENERIC_PVREF	26
+#define SAVEt_GENERIC_SVREF	27
+#define SAVEt_GP		28
+#define SAVEt_GVSV		29
+#define SAVEt_HINTS		30
+#define SAVEt_HPTR		31
+#define SAVEt_HV		32
+#define SAVEt_I32		33
+#define SAVEt_INT		34
+#define SAVEt_ITEM		35
+#define SAVEt_IV		36
+#define SAVEt_LONG		37
+#define SAVEt_PPTR		38
+#define SAVEt_SAVESWITCHSTACK	39
+#define SAVEt_SHARED_PVREF	40
+#define SAVEt_SPTR		41
+#define SAVEt_STACK_CXPOS	42
+#define SAVEt_SV		43
+#define SAVEt_SVREF		44
+#define SAVEt_VPTR		45
+
+#define SAVEt_ARG2_MAX		45
+
+/* three args */
+
+#define SAVEt_AELEM		46
+#define SAVEt_DELETE		47
+#define SAVEt_HELEM		48
+#define SAVEt_PADSV_AND_MORTALIZE 49
+#define SAVEt_SET_SVFLAGS	50
+#define SAVEt_GVSLOT		51
 
 #define SAVEf_SETMAGIC		1
 #define SAVEf_KEEPOLDELEM	2