Eliminate PL_sawalias, GPf_ALIASED_SV

These two commits:

    v5.21.3-759-gff2a62e "Skip no-common-vars optimisation for aliases"
    v5.21.4-210-gc997e36 "Make list assignment respect foreach aliasing"

added a run-time mechanism to detect aliased package variables,
by either "*pkg = ...," or "for $pkg (...)", and used that information
to enable the OPpASSIGN_COMMON mechanism at runtime for detecting common
elements in a list assign, e.g.

    for $alias ($a, ...) {
        ($a,$b) = (1,$alias);
    }

The previous commit but one changed the OPpASSIGN_COMMON mechanism such
that it no longer uses PL_sawalias. So this var and the mechanism for
setting it can now be removed.

This commit removes:

    * the PL_sawalias variable
    * the GPf_ALIASED_SV GP flag
    * the SAVEt_GP_ALIASED_SV and save_aliased_sv() save type.

13 files changed, 3 insertions, 78 deletions

diff --git a/dump.c b/dump.c
index 7369a9a5ca..778e34507c 100644
--- a/dump.c
+++ b/dump.c
@@ -2032,7 +2032,7 @@ Perl_do_sv_dump(pTHX_ I32 level, PerlIO *file, SV *sv, I32 nest, I32 maxnest, bo
 	Perl_dump_indent(aTHX_ level, file, "    GPFLAGS = 0x%"UVxf
 					    " (%s)\n",
 			       (UV)GvGPFLAGS(sv),
-			       GvALIASED_SV(sv) ? "ALIASED_SV" : "");
+			       "");
 	Perl_dump_indent(aTHX_ level, file, "    LINE = %"IVdf"\n", (IV)GvLINE(sv));
 	Perl_dump_indent(aTHX_ level, file, "    FILE = \"%s\"\n", GvFILE(sv));
 	do_gv_dump (level, file, "    EGV", GvEGV(sv));
diff --git a/embed.fnc b/embed.fnc
index 74011e0442..12c0551963 100644
--- a/embed.fnc
+++ b/embed.fnc
@@ -1257,7 +1257,6 @@ Ap	|void	|savestack_grow_cnt	|I32 need
 Amp	|void	|save_aelem	|NN AV* av|SSize_t idx|NN SV **sptr
 Ap	|void	|save_aelem_flags|NN AV* av|SSize_t idx|NN SV **sptr \
 				 |const U32 flags
-p	|void	|save_aliased_sv|NN GV* gv
 Ap	|I32	|save_alloc	|I32 size|I32 pad
 Ap	|void	|save_aptr	|NN AV** aptr
 Ap	|AV*	|save_ary	|NN GV* gv
diff --git a/embed.h b/embed.h
index c03c0f5fc6..0611ea9327 100644
--- a/embed.h
+++ b/embed.h
@@ -1304,7 +1304,6 @@
 #define rsignal_restore(a,b)	Perl_rsignal_restore(aTHX_ a,b)
 #define rsignal_save(a,b,c)	Perl_rsignal_save(aTHX_ a,b,c)
 #define rxres_save(a,b)		Perl_rxres_save(aTHX_ a,b)
-#define save_aliased_sv(a)	Perl_save_aliased_sv(aTHX_ a)
 #define save_strlen(a)		Perl_save_strlen(aTHX_ a)
 #define sawparens(a)		Perl_sawparens(aTHX_ a)
 #define scalar(a)		Perl_scalar(aTHX_ a)
diff --git a/embedvar.h b/embedvar.h
index 9ed30e02df..c6213c090f 100644
--- a/embedvar.h
+++ b/embedvar.h
@@ -270,7 +270,6 @@
 #define PL_savestack		(vTHX->Isavestack)
 #define PL_savestack_ix		(vTHX->Isavestack_ix)
 #define PL_savestack_max	(vTHX->Isavestack_max)
-#define PL_sawalias		(vTHX->Isawalias)
 #ifndef PL_sawampersand
 #define PL_sawampersand		(vTHX->Isawampersand)
 #endif
diff --git a/ext/B/t/b.t b/ext/B/t/b.t
index 1420f91fcf..4638c3e577 100644
--- a/ext/B/t/b.t
+++ b/ext/B/t/b.t
@@ -209,12 +209,6 @@ is($gv_ref->SAFENAME(), "gv", "Test SAFENAME()");
 like($gv_ref->FILE(), qr/b\.t$/, "Testing FILE()");
 is($gv_ref->SvTYPE(), B::SVt_PVGV, "Test SvTYPE()");
 is($gv_ref->FLAGS() & B::SVTYPEMASK, B::SVt_PVGV, "Test SVTYPEMASK");
-is($gv_ref->GPFLAGS & B::GPf_ALIASED_SV, 0, 'GPFLAGS are unset');
-{
-    local *gv = \my $x;
-    is($gv_ref->GPFLAGS & B::GPf_ALIASED_SV, B::GPf_ALIASED_SV,
-        'GPFLAGS gets GPf_ALIASED_SV set');
-}    
 
 # The following return B::SPECIALs.
 is(ref B::sv_yes(), "B::SPECIAL", "B::sv_yes()");
diff --git a/gv.h b/gv.h
index a6bb749443..69414ec2c8 100644
--- a/gv.h
+++ b/gv.h
@@ -198,12 +198,6 @@ Return the CV from the GV.
 #define GvIMPORTED_CV_on(gv)	(GvFLAGS(gv) |= GVf_IMPORTED_CV)
 #define GvIMPORTED_CV_off(gv)	(GvFLAGS(gv) &= ~GVf_IMPORTED_CV)
 
-#define GPf_ALIASED_SV	1
-
-#define GvALIASED_SV(gv)	(GvGPFLAGS(gv) & GPf_ALIASED_SV)
-#define GvALIASED_SV_on(gv)	(GvGPFLAGS(gv) |= GPf_ALIASED_SV)
-#define GvALIASED_SV_off(gv)	(GvGPFLAGS(gv) &= ~GPf_ALIASED_SV)
-
 #ifndef PERL_CORE
 #  define GvIN_PAD(gv)		0
 #  define GvIN_PAD_on(gv)	NOOP
diff --git a/intrpvar.h b/intrpvar.h
index 6ee88b31d2..142542a030 100644
--- a/intrpvar.h
+++ b/intrpvar.h
@@ -60,9 +60,6 @@ PERLVAR(I, markstack,	I32 *)		/* stack_sp locations we're
 PERLVAR(I, markstack_ptr, I32 *)
 PERLVAR(I, markstack_max, I32 *)
 
-PERLVARI(I, sawalias,	bool,	FALSE)	/* must enable common-vars
-					   pessimisation */
-
 #ifdef PERL_HASH_RANDOMIZE_KEYS
 #ifdef USE_PERL_PERTURB_KEYS
 PERLVARI(I, hash_rand_bits_enabled, U8, 1) /* used to randomize hash stuff 0 == no-random, 1 == random, 2 == determinsitic */
diff --git a/pp_ctl.c b/pp_ctl.c
index cc6a55f76e..5b58f47684 100644
--- a/pp_ctl.c
+++ b/pp_ctl.c
@@ -2145,7 +2145,6 @@ PP(pp_enteriter)
 	save_pushptrptr(gv, SvREFCNT_inc(*svp), SAVEt_GVSV);
 	*svp = newSV(0);
 	itervar = (void *)gv;
-	save_aliased_sv(gv);
     }
     else {
 	SV * const sv = POPs;
diff --git a/pp_hot.c b/pp_hot.c
index b32a7063d6..a6c65c24f3 100644
--- a/pp_hot.c
+++ b/pp_hot.c
@@ -47,7 +47,6 @@ PP(pp_const)
 PP(pp_nextstate)
 {
     PL_curcop = (COP*)PL_op;
-    PL_sawalias = 0;
     TAINT_NOT;		/* Each statement is presumed innocent */
     PL_stack_sp = PL_stack_base + cxstack[cxstack_ix].blk_oldsp;
     FREETMPS;
@@ -63,8 +62,6 @@ PP(pp_gvsv)
 	PUSHs(save_scalar(cGVOP_gv));
     else
 	PUSHs(GvSVn(cGVOP_gv));
-    if (GvREFCNT(cGVOP_gv) > 1 || GvALIASED_SV(cGVOP_gv))
-	PL_sawalias = TRUE;
     RETURN;
 }
 
@@ -99,9 +96,6 @@ PP(pp_gv)
 {
     dSP;
     XPUSHs(MUTABLE_SV(cGVOP_gv));
-    if (isGV(cGVOP_gv)
-     && (GvREFCNT(cGVOP_gv) > 1 || GvALIASED_SV(cGVOP_gv)))
-	PL_sawalias = TRUE;
     RETURN;
 }
 
diff --git a/proto.h b/proto.h
index 5b960a239c..a3bd488b44 100644
--- a/proto.h
+++ b/proto.h
@@ -2659,9 +2659,6 @@ PERL_CALLCONV void	Perl_save_adelete(pTHX_ AV *av, SSize_t key);
 PERL_CALLCONV void	Perl_save_aelem_flags(pTHX_ AV* av, SSize_t idx, SV **sptr, const U32 flags);
 #define PERL_ARGS_ASSERT_SAVE_AELEM_FLAGS	\
 	assert(av); assert(sptr)
-PERL_CALLCONV void	Perl_save_aliased_sv(pTHX_ GV* gv);
-#define PERL_ARGS_ASSERT_SAVE_ALIASED_SV	\
-	assert(gv)
 PERL_CALLCONV I32	Perl_save_alloc(pTHX_ I32 size, I32 pad);
 PERL_CALLCONV void	Perl_save_aptr(pTHX_ AV** aptr);
 #define PERL_ARGS_ASSERT_SAVE_APTR	\
diff --git a/scope.c b/scope.c
index 5699d7cbd7..9768c30734 100644
--- a/scope.c
+++ b/scope.c
@@ -720,16 +720,6 @@ Perl_save_alloc(pTHX_ I32 size, I32 pad)
     return start;
 }
 
-void
-Perl_save_aliased_sv(pTHX_ GV *gv)
-{
-    dSS_ADD;
-    PERL_ARGS_ASSERT_SAVE_ALIASED_SV;
-    SS_ADD_PTR(gp_ref(GvGP(gv)));
-    SS_ADD_UV(SAVEt_GP_ALIASED_SV | cBOOL(GvALIASED_SV(gv)) << 8);
-    SS_ADD_END(2);
-}
-
 
 
 #define ARG0_SV  MUTABLE_SV(arg0.any_ptr)
@@ -1252,24 +1242,6 @@ Perl_leave_scope(pTHX_ I32 base)
 	case SAVEt_READONLY_OFF:
 	    SvREADONLY_off(ARG0_SV);
 	    break;
-	case SAVEt_GP_ALIASED_SV: {
-	    /* The GP may have been abandoned, leaving the savestack with
-	       the only remaining reference to it.  */
-	    GP * const gp = (GP *)ARG0_PTR;
-	    if (gp->gp_refcnt == 1) {
-		GV * const gv = (GV *)sv_2mortal(newSV_type(SVt_PVGV));
-		isGV_with_GP_on(gv);
-		GvGP_set(gv,gp);
-		gp_free(gv);
-		isGV_with_GP_off(gv);
-	    }
-	    else {
-		gp->gp_refcnt--;
-		if (uv >> 8) gp->gp_flags |=  GPf_ALIASED_SV;
-		else	     gp->gp_flags &= ~GPf_ALIASED_SV;
-	    }
-	    break;
-	}
 	default:
 	    Perl_croak(aTHX_ "panic: leave_scope inconsistency %u", type);
 	}
diff --git a/scope.h b/scope.h
index 97ef3faa91..0de5b7777a 100644
--- a/scope.h
+++ b/scope.h
@@ -21,7 +21,7 @@
 
 /* one arg */
 
-#define SAVEt_GP_ALIASED_SV	4
+/*** SPARE      	        4 ***/
 #define SAVEt_BOOL		5
 #define SAVEt_COMPILE_WARNINGS	6
 #define SAVEt_COMPPAD		7
diff --git a/sv.c b/sv.c
index 79d2719da8..cd1bbf528e 100644
--- a/sv.c
+++ b/sv.c
@@ -4119,18 +4119,7 @@ Perl_gv_setref(pTHX_ SV *const dstr, SV *const sstr)
 	    && CopSTASH_ne(PL_curcop, GvSTASH(dstr))) {
 	    GvFLAGS(dstr) |= import_flag;
 	}
-	if (import_flag == GVf_IMPORTED_SV) {
-	    if (intro) {
-		save_aliased_sv((GV *)dstr);
-	    }
-	    /* Turn off the flag if sref is not referenced elsewhere,
-	       even by weak refs.  (SvRMAGICAL is a pessimistic check for
-	       back refs.)  */
-	    if (SvREFCNT(sref) <= 2 && !SvRMAGICAL(sref))
-		GvALIASED_SV_off(dstr);
-	    else
-		GvALIASED_SV_on(dstr);
-	}
+
 	if (stype == SVt_PVHV) {
 	    const char * const name = GvNAME((GV*)dstr);
 	    const STRLEN len = GvNAMELEN(dstr);
@@ -14163,13 +14152,6 @@ Perl_ss_dup(pTHX_ PerlInterpreter *proto_perl, CLONE_PARAMS* param)
 	    ptr = POPPTR(ss,ix);
 	    TOPPTR(nss,ix) = parser_dup((const yy_parser*)ptr, param);
 	    break;
-	case SAVEt_GP_ALIASED_SV: {
-	    GP * gp_ptr = (GP *)POPPTR(ss,ix);
-	    GP * new_gp_ptr = gp_dup(gp_ptr, param);
-	    TOPPTR(nss,ix) = new_gp_ptr;
-	    new_gp_ptr->gp_refcnt++;
-	    break;
-	}
 	default:
 	    Perl_croak(aTHX_
 		       "panic: ss_dup inconsistency (%"IVdf")", (IV) type);
@@ -14404,7 +14386,6 @@ perl_clone_using(PerlInterpreter *proto_perl, UV flags,
     PL_minus_F		= proto_perl->Iminus_F;
     PL_doswitches	= proto_perl->Idoswitches;
     PL_dowarn		= proto_perl->Idowarn;
-    PL_sawalias		= proto_perl->Isawalias;
 #ifdef PERL_SAWAMPERSAND
     PL_sawampersand	= proto_perl->Isawampersand;
 #endif