From f7d8844b17b3028b3c2083c6fff2f5e3cdc5f4cb Mon Sep 17 00:00:00 2001
From: Daniel Dragan <bulk88@hotmail.com>
Date: Fri, 25 Sep 2015 16:38:11 -0400
Subject: [PATCH 1/2] remove repeated PL_stack_sp derefs in
 Perl_eval_sv/Perl_call_sv

Reduce scope of local SP and remove excessive reads and writes to
PL_stack_sp in Perl_eval_sv/Perl_call_sv. EXTEND macro refetches the
possibly realloced SP on its own, Perl_stack_grow returns the new SP as a
retval and therefore in a register. By using PL_stack_sp instead of
Perl_stack_grow, an extra redundant mem read is done. Also dont keep
SP around for long periods unused, it wastes a C stack slot or non-vol
reg and makes the callframe bigger. The EXTEND could be placed
in the !(flags & G_METHOD_NAMED) branch, but that will be done in another
patch for bisectability.

VC 2003 -O1 machine code sizes of the functions
Perl_eval_sv before 0x28a after 0x286
Perl_call_sv before 0x3cd after 0x3cb

The savings look small since in x86 "*var+=4" and "var+=4" are the same
number of bytes to encode the instruction, only the mod R/M bitfield vals
are different. RISC CPUs benefit more from this patch.

commit c106c2be8b "G_METHOD_NAMED flag for call_method and call_sv"
added skipping the push SV onto stack

The EXTEND and PL_stack_sp direct manipulation code is from
commit a0d0e21ea6 "perl 5.000". The reason is unknown why it did
"SV** sp = stack_sp;" and later "EXTEND(stack_sp, 1);" instead of using
SP, since EXTEND at that time, and to this day requires C auto sp be in
scope.
---
 perl.c |   25 +++++++++++++++++--------
 1 files changed, 17 insertions(+), 8 deletions(-)

diff --git a/perl.c b/perl.c
index 1bd2cbb..52a5ace 100644
--- a/perl.c
+++ b/perl.c
@@ -2696,7 +2696,7 @@ I32
 Perl_call_sv(pTHX_ SV *sv, VOL I32 flags)
           		/* See G_* flags in cop.h */
 {
-    dVAR; dSP;
+    dVAR;
     LOGOP myop;		/* fake syntax tree node */
     METHOP method_op;
     I32 oldmark;
@@ -2726,9 +2726,14 @@ Perl_call_sv(pTHX_ SV *sv, VOL I32 flags)
     SAVEOP();
     PL_op = (OP*)&myop;
 
-    EXTEND(PL_stack_sp, 1);
-    if (!(flags & G_METHOD_NAMED))
-        *++PL_stack_sp = sv;
+    {
+	dSP;
+	EXTEND(SP, 1);
+	if (!(flags & G_METHOD_NAMED)) {
+	    PUSHs(sv);
+	    PUTBACK;
+	}
+    }
     oldmark = TOPMARK;
     oldscope = PL_scopestack_ix;
 
@@ -2839,9 +2844,8 @@ Perl_eval_sv(pTHX_ SV *sv, I32 flags)
           		/* See G_* flags in cop.h */
 {
     dVAR;
-    dSP;
     UNOP myop;		/* fake syntax tree node */
-    VOL I32 oldmark = SP - PL_stack_base;
+    VOL I32 oldmark;
     VOL I32 retval = 0;
     int ret;
     OP* const oldop = PL_op;
@@ -2857,8 +2861,13 @@ Perl_eval_sv(pTHX_ SV *sv, I32 flags)
     SAVEOP();
     PL_op = (OP*)&myop;
     Zero(&myop, 1, UNOP);
-    EXTEND(PL_stack_sp, 1);
-    *++PL_stack_sp = sv;
+    {
+	dSP;
+	oldmark = SP - PL_stack_base;
+	EXTEND(SP, 1);
+	PUSHs(sv);
+	PUTBACK;
+    }
 
     if (!(flags & G_NOARGS))
 	myop.op_flags = OPf_STACKED;
-- 
1.7.9.msysgit.0

From fc41c78e1d6528daf39d9cfeae1b053f2705a10a Mon Sep 17 00:00:00 2001
From: Daniel Dragan <bulk88@hotmail.com>
Date: Fri, 25 Sep 2015 16:52:56 -0400
Subject: [PATCH 2/2] Perl_call_sv move EXTEND into branch that needs it

If we aren't manipulating the stack, dont fetch it, check and possibly
extend it. There is a slight chance this EXTEND was covering up missing
EXTENDs somewhere else in Perl core or CPAN C code, if future bisects or
valgrind reports show that this EXTEND by 1 must always be done, this
patch can be reverted. pp_method_named contains a EXTEND/XPUSH* call,
pp_entersub requires 1 arg on stack so, both sides of the
"if (!(flags & G_METHOD_NAMED))" test will in theory make sure there is
1 free slot on the stack on entry to a SUB or XSUB.

See also
http://www.nntp.perl.org/group/perl.perl5.porters/2015/09/msg231329.html
---
 perl.c |    8 +++-----
 1 files changed, 3 insertions(+), 5 deletions(-)

diff --git a/perl.c b/perl.c
index 52a5ace..8552bab 100644
--- a/perl.c
+++ b/perl.c
@@ -2726,13 +2726,11 @@ Perl_call_sv(pTHX_ SV *sv, VOL I32 flags)
     SAVEOP();
     PL_op = (OP*)&myop;
 
-    {
+    if (!(flags & G_METHOD_NAMED)) {
 	dSP;
 	EXTEND(SP, 1);
-	if (!(flags & G_METHOD_NAMED)) {
-	    PUSHs(sv);
-	    PUTBACK;
-	}
+	PUSHs(sv);
+	PUTBACK;
     }
     oldmark = TOPMARK;
     oldscope = PL_scopestack_ix;
-- 
1.7.9.msysgit.0