Create `defer` syntax and `OP_PUSHDEFER` opcode

Adds syntax `defer { BLOCK }` to create a deferred block; code that is
deferred until the scope exits. This syntax is guarded by

  use feature 'defer';

Adds a new opcode, `OP_PUSHDEFER`, which is a LOGOP whose `op_other` field
gives the start of an optree to be deferred until scope exit. That op
pointer will be stored on the save stack and invoked as part of scope
unwind.

Included is support for `B::Deparse` to deparse the optree back into
syntax.

1 files changed, 8 insertions, 1 deletions

diff --git a/opcode.h b/opcode.h
index a1e7670f15..2fadc692ff 100644
--- a/opcode.h
+++ b/opcode.h
@@ -553,6 +553,7 @@ EXTCONST char* const PL_op_name[] = {
 	"leavetrycatch",
 	"poptry",
 	"catch",
+	"pushdefer",
         "freed",
 };
 #endif
@@ -965,6 +966,7 @@ EXTCONST char* const PL_op_desc[] = {
 	"try {block} exit",
 	"pop try",
 	"catch {} block",
+	"push defer {} block",
         "freed op",
 };
 #endif
@@ -1380,6 +1382,7 @@ EXT Perl_ppaddr_t PL_ppaddr[] /* or perlvars.h */
 	Perl_pp_leavetrycatch,
 	Perl_pp_poptry,
 	Perl_pp_catch,
+	Perl_pp_pushdefer,
 }
 #endif
 ;
@@ -1791,6 +1794,7 @@ EXT Perl_check_t PL_check[] /* or perlvars.h */
 	Perl_ck_null,		/* leavetrycatch */
 	Perl_ck_null,		/* poptry */
 	Perl_ck_null,		/* catch */
+	Perl_ck_null,		/* pushdefer */
 }
 #endif
 ;
@@ -2203,6 +2207,7 @@ EXTCONST U32 PL_opargs[] = {
 	0x00000400,	/* leavetrycatch */
 	0x00000400,	/* poptry */
 	0x00000300,	/* catch */
+	0x00000300,	/* pushdefer */
 };
 #endif
 
@@ -2870,6 +2875,7 @@ EXTCONST I16  PL_op_private_bitdef_ix[] = {
       -1, /* leavetrycatch */
       -1, /* poptry */
        0, /* catch */
+       0, /* pushdefer */
 
 };
 
@@ -2888,7 +2894,7 @@ EXTCONST I16  PL_op_private_bitdef_ix[] = {
  */
 
 EXTCONST U16  PL_op_private_bitdefs[] = {
-    0x0003, /* scalar, prototype, refgen, srefgen, readline, regcmaybe, regcreset, regcomp, substcont, chop, schop, defined, undef, study, preinc, i_preinc, predec, i_predec, postinc, i_postinc, postdec, i_postdec, negate, i_negate, not, complement, ucfirst, lcfirst, uc, lc, quotemeta, aeach, avalues, each, pop, shift, grepstart, mapstart, mapwhile, range, and, or, dor, andassign, orassign, dorassign, argcheck, argdefelem, method, method_named, method_super, method_redir, method_redir_super, entergiven, leavegiven, enterwhen, leavewhen, untie, tied, dbmclose, getsockname, getpeername, lstat, stat, readlink, readdir, telldir, rewinddir, closedir, localtime, alarm, require, dofile, entertry, ghbyname, gnbyname, gpbyname, shostent, snetent, sprotoent, sservent, gpwnam, gpwuid, ggrnam, ggrgid, lock, once, fc, anonconst, cmpchain_and, cmpchain_dup, entertrycatch, catch */
+    0x0003, /* scalar, prototype, refgen, srefgen, readline, regcmaybe, regcreset, regcomp, substcont, chop, schop, defined, undef, study, preinc, i_preinc, predec, i_predec, postinc, i_postinc, postdec, i_postdec, negate, i_negate, not, complement, ucfirst, lcfirst, uc, lc, quotemeta, aeach, avalues, each, pop, shift, grepstart, mapstart, mapwhile, range, and, or, dor, andassign, orassign, dorassign, argcheck, argdefelem, method, method_named, method_super, method_redir, method_redir_super, entergiven, leavegiven, enterwhen, leavewhen, untie, tied, dbmclose, getsockname, getpeername, lstat, stat, readlink, readdir, telldir, rewinddir, closedir, localtime, alarm, require, dofile, entertry, ghbyname, gnbyname, gpbyname, shostent, snetent, sprotoent, sservent, gpwnam, gpwuid, ggrnam, ggrgid, lock, once, fc, anonconst, cmpchain_and, cmpchain_dup, entertrycatch, catch, pushdefer */
     0x2fdc, 0x40d9, /* pushmark */
     0x00bd, /* wantarray, runcv */
     0x0438, 0x1a50, 0x418c, 0x3d28, 0x3505, /* const */
@@ -3370,6 +3376,7 @@ EXTCONST U8 PL_op_private_valid[] = {
     /* LEAVETRYCATCH */ (0),
     /* POPTRY     */ (0),
     /* CATCH      */ (OPpARG1_MASK),
+    /* PUSHDEFER  */ (OPpARG1_MASK),
 
 };