Eliminate PVBM. Store fast Boyer-Moore tables in PVGV.

Add the placeholder for new type, temporarily named BIND, for binding
and aliasing in 6 on 5.

p4raw-id: //depot/perl@29544

9 files changed, 81 insertions, 90 deletions

diff --git a/dump.c b/dump.c
index cfa4a9b473..185369141a 100644
--- a/dump.c
+++ b/dump.c
@@ -32,11 +32,11 @@ static const char* const svtypenames[SVt_LAST] = {
     "IV",
     "NV",
     "RV",
+    "BIND",
     "PV",
     "PVIV",
     "PVNV",
     "PVMG",
-    "PVBM",
     "PVGV",
     "PVLV",
     "PVAV",
@@ -52,11 +52,11 @@ static const char* const svshorttypenames[SVt_LAST] = {
     "IV",
     "NV",
     "RV",
+    "BIND",
     "PV",
     "PVIV",
     "PVNV",
     "PVMG",
-    "BM",
     "GV",
     "PVLV",
     "AV",
@@ -1429,16 +1429,14 @@ Perl_do_sv_dump(pTHX_ I32 level, PerlIO *file, SV *sv, I32 nest, I32 maxnest, bo
 		sv_catpv(d, " ),");
 	    }
 	}
+	if (SvTAIL(sv))		sv_catpv(d, "TAIL,");
+	if (SvVALID(sv))	sv_catpv(d, "VALID,");
 	/* FALL THROUGH */
     default:
     evaled_or_uv:
 	if (SvEVALED(sv))	sv_catpv(d, "EVALED,");
 	if (SvIsUV(sv) && !(flags & SVf_ROK))	sv_catpv(d, "IsUV,");
 	break;
-    case SVt_PVBM:
-	if (SvTAIL(sv))		sv_catpv(d, "TAIL,");
-	if (SvVALID(sv))	sv_catpv(d, "VALID,");
-	break;
     case SVt_PVMG:
 	if (SvPAD_TYPED(sv))	sv_catpv(d, "TYPED,");
 	if (SvPAD_OUR(sv))	sv_catpv(d, "OUR,");
@@ -2341,8 +2339,8 @@ Perl_sv_xmlpeek(pTHX_ SV *sv)
     case SVt_PVGV:
 	sv_catpv(t, " GV=\"");
 	break;
-    case SVt_PVBM:
-	sv_catpv(t, " BM=\"");
+    case SVt_BIND:
+	sv_catpv(t, " BIND=\"");
 	break;
     case SVt_PVFM:
 	sv_catpv(t, " FM=\"");
diff --git a/ext/B/B.xs b/ext/B/B.xs
index 0b021bf517..a75c692461 100644
--- a/ext/B/B.xs
+++ b/ext/B/B.xs
@@ -24,11 +24,16 @@ static const char* const svclassnames[] = {
     "B::IV",
     "B::NV",
     "B::RV",
+#if PERL_VERSION >= 9
+    "B::BIND",
+#endif
     "B::PV",
     "B::PVIV",
     "B::PVNV",
     "B::PVMG",
+#if PERL_VERSION <= 8
     "B::BM",
+#endif
 #if PERL_VERSION >= 9
     "B::GV",
 #endif
diff --git a/ext/Storable/Storable.xs b/ext/Storable/Storable.xs
index 17a7b5c766..aa4b57dac8 100644
--- a/ext/Storable/Storable.xs
+++ b/ext/Storable/Storable.xs
@@ -3457,7 +3457,9 @@ static int sv_type(pTHX_ SV *sv)
 		if (SvRMAGICAL(sv) && (mg_find(sv, 'p')))
 			return svis_TIED_ITEM;
 		/* FALL THROUGH */
+#if PERL_VERSION < 9
 	case SVt_PVBM:
+#endif
 		if (SvRMAGICAL(sv) && (mg_find(sv, 'q')))
 			return svis_TIED;
 		return SvROK(sv) ? svis_REF : svis_SCALAR;
@@ -3471,6 +3473,9 @@ static int sv_type(pTHX_ SV *sv)
 		return svis_HASH;
 	case SVt_PVCV:
 		return svis_CODE;
+#if PERL_VERSION > 8
+	/* case SVt_BIND: */
+#endif
 	default:
 		break;
 	}
diff --git a/op.h b/op.h
index 5c12c77f0d..d2369dfbaf 100644
--- a/op.h
+++ b/op.h
@@ -460,7 +460,8 @@ struct loop {
 
 #ifdef USE_ITHREADS
 #  define	cGVOPx_gv(o)	((GV*)PAD_SVl(cPADOPx(o)->op_padix))
-#  define	IS_PADGV(v)	(v && SvTYPE(v) == SVt_PVGV && GvIN_PAD(v))
+#  define	IS_PADGV(v)	(v && SvTYPE(v) == SVt_PVGV && isGV_with_GP(v) \
+				 && GvIN_PAD(v))
 #  define	IS_PADCONST(v)	(v && SvREADONLY(v))
 #  define	cSVOPx_sv(v)	(cSVOPx(v)->op_sv \
 				 ? cSVOPx(v)->op_sv : PAD_SVl((v)->op_targ))
diff --git a/pod/perltodo.pod b/pod/perltodo.pod
index 8626f2a9b5..be9fd79ddb 100644
--- a/pod/perltodo.pod
+++ b/pod/perltodo.pod
@@ -405,15 +405,6 @@ These tasks would need C knowledge, and roughly the level of knowledge of
 the perl API that comes from writing modules that use XS to interface to
 C.
 
-=head2 shrink C<PVBM>s
-
-By removing unused elements and careful re-ordering, the structures for C<AV>s,
-C<HV>s, C<CV>s and C<GV>s have recently been shrunk considerably. C<PVIO>s
-probably aren't worth it, as typical programs don't use more than 8, and
-(at least) C<Filter::Util::Call> uses C<SvPVX>/C<SvCUR>/C<SvLEN> on a C<PVIO>,
-so it would mean code changes to modules on CPAN. C<PVBM>s might have some
-savings to win.
-
 =head2 autovivification
 
 Make all autovivification consistent w.r.t LVALUE/RVALUE and strict/no strict;
diff --git a/pp_hot.c b/pp_hot.c
index 0b03721090..9fe7c70e73 100644
--- a/pp_hot.c
+++ b/pp_hot.c
@@ -2120,7 +2120,8 @@ PP(pp_subst)
 	!is_cow &&
 #endif
 	(SvREADONLY(TARG)
-	|| ( (SvTYPE(TARG) == SVt_PVGV || SvTYPE(TARG) > SVt_PVLV)
+	 || ( ((SvTYPE(TARG) == SVt_PVGV && isGV_with_GP(TARG))
+	       || SvTYPE(TARG) > SVt_PVLV)
 	     && !(SvTYPE(TARG) == SVt_PVGV && SvFAKE(TARG)))))
 	DIE(aTHX_ PL_no_modify);
     PUTBACK;
diff --git a/sv.c b/sv.c
index b6be97ce8d..e94629dd42 100644
--- a/sv.c
+++ b/sv.c
@@ -904,6 +904,9 @@ static const struct body_details bodies_by_type[] = {
     /* RVs are in the head now.  */
     { 0, 0, 0, SVt_RV, FALSE, NONV, NOARENA, 0 },
 
+    /* The bind placeholder pretends to be an RV for now.  */
+    { 0, 0, 0, SVt_BIND, FALSE, NONV, NOARENA, 0 },
+
     /* 8 bytes on most ILP32 with IEEE doubles */
     { sizeof(xpv_allocated),
       copy_length(XPV, xpv_len)
@@ -926,10 +929,6 @@ static const struct body_details bodies_by_type[] = {
     { sizeof(XPVMG), copy_length(XPVMG, xmg_stash), 0, SVt_PVMG, FALSE, HADNV,
       HASARENA, FIT_ARENA(0, sizeof(XPVMG)) },
     
-    /* 36 */
-    { sizeof(XPVBM), sizeof(XPVBM), 0, SVt_PVBM, TRUE, HADNV,
-      HASARENA, FIT_ARENA(0, sizeof(XPVBM)) },
-
     /* 48 */
     { sizeof(XPVGV), sizeof(XPVGV), 0, SVt_PVGV, TRUE, HADNV,
       HASARENA, FIT_ARENA(0, sizeof(XPVGV)) },
@@ -1293,7 +1292,6 @@ Perl_sv_upgrade(pTHX_ register SV *sv, svtype new_type)
 	assert(!SvNOK(sv));
     case SVt_PVIO:
     case SVt_PVFM:
-    case SVt_PVBM:
     case SVt_PVGV:
     case SVt_PVCV:
     case SVt_PVLV:
@@ -2159,8 +2157,8 @@ Perl_sv_2iv_flags(pTHX_ register SV *sv, I32 flags)
     dVAR;
     if (!sv)
 	return 0;
-    if (SvGMAGICAL(sv) || SvTYPE(sv) == SVt_PVBM) {
-	/* PVBMs use the same flag bit as SVf_IVisUV, so must let them
+    if (SvGMAGICAL(sv) || (SvTYPE(sv) == SVt_PVGV && SvVALID(sv))) {
+	/* FBMs use the same flag bit as SVf_IVisUV, so must let them
 	   cache IVs just in case. In practice it seems that they never
 	   actually anywhere accessible by user Perl code, let alone get used
 	   in anything other than a string context.  */
@@ -2243,8 +2241,8 @@ Perl_sv_2uv_flags(pTHX_ register SV *sv, I32 flags)
     dVAR;
     if (!sv)
 	return 0;
-    if (SvGMAGICAL(sv) || SvTYPE(sv) == SVt_PVBM) {
-	/* PVBMs use the same flag bit as SVf_IVisUV, so must let them
+    if (SvGMAGICAL(sv) || (SvTYPE(sv) == SVt_PVGV && SvVALID(sv))) {
+	/* FBMs use the same flag bit as SVf_IVisUV, so must let them
 	   cache IVs just in case.  */
 	if (flags & SV_GMAGIC)
 	    mg_get(sv);
@@ -2320,8 +2318,8 @@ Perl_sv_2nv(pTHX_ register SV *sv)
     dVAR;
     if (!sv)
 	return 0.0;
-    if (SvGMAGICAL(sv) || SvTYPE(sv) == SVt_PVBM) {
-	/* PVBMs use the same flag bit as SVf_IVisUV, so must let them
+    if (SvGMAGICAL(sv) || (SvTYPE(sv) == SVt_PVGV && SvVALID(sv))) {
+	/* FBMs use the same flag bit as SVf_IVisUV, so must let them
 	   cache IVs just in case.  */
 	mg_get(sv);
 	if (SvNOKp(sv))
@@ -3453,21 +3451,22 @@ Perl_sv_setsv_flags(pTHX_ SV *dstr, register SV *sstr, I32 flags)
 	}
 	break;
 
+	/* case SVt_BIND: */
     case SVt_PVGV:
-	if (dtype <= SVt_PVGV) {
+	if (isGV_with_GP(sstr) && dtype <= SVt_PVGV) {
 	    glob_assign_glob(dstr, sstr, dtype);
 	    return;
 	}
+	/* SvVALID means that this PVGV is playing at being an FBM.  */
 	/*FALLTHROUGH*/
 
     case SVt_PVMG:
     case SVt_PVLV:
-    case SVt_PVBM:
 	if (SvGMAGICAL(sstr) && (flags & SV_GMAGIC)) {
 	    mg_get(sstr);
 	    if (SvTYPE(sstr) != stype) {
 		stype = SvTYPE(sstr);
-		if (stype == SVt_PVGV && dtype <= SVt_PVGV) {
+		if (isGV_with_GP(sstr) && stype == SVt_PVGV && dtype <= SVt_PVGV) {
 		    glob_assign_glob(dstr, sstr, dtype);
 		    return;
 		}
@@ -3498,7 +3497,8 @@ Perl_sv_setsv_flags(pTHX_ SV *dstr, register SV *sstr, I32 flags)
 	    SvOK_off(dstr);
 	}
     } else if (sflags & SVf_ROK) {
-	if (dtype == SVt_PVGV && SvTYPE(SvRV(sstr)) == SVt_PVGV) {
+	if (isGV_with_GP(dstr) && dtype == SVt_PVGV
+	    && SvTYPE(SvRV(sstr)) == SVt_PVGV) {
 	    sstr = SvRV(sstr);
 	    if (sstr == dstr) {
 		if (GvIMPORTED(dstr) != GVf_IMPORTED
@@ -3532,7 +3532,7 @@ Perl_sv_setsv_flags(pTHX_ SV *dstr, register SV *sstr, I32 flags)
 	assert(!(sflags & SVf_NOK));
 	assert(!(sflags & SVf_IOK));
     }
-    else if (dtype == SVt_PVGV) {
+    else if (dtype == SVt_PVGV && isGV_with_GP(dstr)) {
 	if (!(sflags & SVf_OK)) {
 	    if (ckWARN(WARN_MISC))
 		Perl_warner(aTHX_ packWARN(WARN_MISC),
@@ -5106,8 +5106,7 @@ Perl_sv_clear(pTHX_ register SV *sv)
 	}
     }
     if (type >= SVt_PVMG) {
-	if ((type == SVt_PVMG || type == SVt_PVGV) && SvPAD_OUR(sv)) {
-	    assert(type != SVt_PVGV);
+	if (type == SVt_PVMG && SvPAD_OUR(sv)) {
 	    SvREFCNT_dec(OURSTASH(sv));
 	} else if (SvMAGIC(sv))
 	    mg_free(sv);
@@ -5115,6 +5114,7 @@ Perl_sv_clear(pTHX_ register SV *sv)
 	    SvREFCNT_dec(SvSTASH(sv));
     }
     switch (type) {
+	/* case SVt_BIND: */
     case SVt_PVIO:
 	if (IoIFP(sv) &&
 	    IoIFP(sv) != PerlIO_stdin() &&
@@ -5130,8 +5130,6 @@ Perl_sv_clear(pTHX_ register SV *sv)
 	Safefree(IoFMT_NAME(sv));
 	Safefree(IoBOTTOM_NAME(sv));
 	goto freescalar;
-    case SVt_PVBM:
-	goto freescalar;
     case SVt_PVCV:
     case SVt_PVFM:
 	cv_undef((CV*)sv);
@@ -5153,14 +5151,15 @@ Perl_sv_clear(pTHX_ register SV *sv)
 	    SvREFCNT_dec(LvTARG(sv));
 	goto freescalar;
     case SVt_PVGV:
-	gp_free((GV*)sv);
-	if (GvNAME_HEK(sv)) {
-	    unshare_hek(GvNAME_HEK(sv));
-	}
+	if (isGV_with_GP(sv)) {
+	    gp_free((GV*)sv);
+	    if (GvNAME_HEK(sv))
+		unshare_hek(GvNAME_HEK(sv));
 	/* If we're in a stash, we don't own a reference to it. However it does
 	   have a back reference to us, which needs to be cleared.  */
-	if (GvSTASH(sv))
-	    sv_del_backref((SV*)GvSTASH(sv), sv);
+	if (!SvVALID(sv) && GvSTASH(sv))
+		sv_del_backref((SV*)GvSTASH(sv), sv);
+	}
     case SVt_PVMG:
     case SVt_PVNV:
     case SVt_PVIV:
@@ -7637,7 +7636,6 @@ Perl_sv_reftype(pTHX_ const SV *sv, int ob)
 	case SVt_PVIV:
 	case SVt_PVNV:
 	case SVt_PVMG:
-	case SVt_PVBM:
 				if (SvVOK(sv))
 				    return "VSTRING";
 				if (SvROK(sv))
@@ -7656,6 +7654,7 @@ Perl_sv_reftype(pTHX_ const SV *sv, int ob)
 	case SVt_PVGV:		return "GLOB";
 	case SVt_PVFM:		return "FORMAT";
 	case SVt_PVIO:		return "IO";
+	case SVt_BIND:		return "BIND";
 	default:		return "UNKNOWN";
 	}
     }
@@ -9877,6 +9876,7 @@ Perl_sv_dup(pTHX_ const SV *sstr, CLONE_PARAMS* param)
 	SvANY(dstr)	= &(dstr->sv_u.svu_rv);
 	Perl_rvpv_dup(aTHX_ dstr, sstr, param);
 	break;
+	/* case SVt_BIND: */
     default:
 	{
 	    /* These are all the types that need complex bodies allocating.  */
@@ -9898,7 +9898,6 @@ Perl_sv_dup(pTHX_ const SV *sstr, CLONE_PARAMS* param)
 	    case SVt_PVFM:
 	    case SVt_PVHV:
 	    case SVt_PVAV:
-	    case SVt_PVBM:
 	    case SVt_PVCV:
 	    case SVt_PVLV:
 	    case SVt_PVMG:
@@ -9955,8 +9954,6 @@ Perl_sv_dup(pTHX_ const SV *sstr, CLONE_PARAMS* param)
 		break;
 	    case SVt_PVMG:
 		break;
-	    case SVt_PVBM:
-		break;
 	    case SVt_PVLV:
 		/* XXX LvTARGOFF sometimes holds PMOP* when DEBUGGING */
 		if (LvTYPE(dstr) == 't') /* for tie: unrefcnted fake (SV**) */
@@ -9967,12 +9964,15 @@ Perl_sv_dup(pTHX_ const SV *sstr, CLONE_PARAMS* param)
 		    LvTARG(dstr) = sv_dup_inc(LvTARG(dstr), param);
 		break;
 	    case SVt_PVGV:
-		if (GvNAME_HEK(dstr))
-		    GvNAME_HEK(dstr) = hek_dup(GvNAME_HEK(dstr), param);
+		if(isGV_with_GP(sstr)) {
+		    if (GvNAME_HEK(dstr))
+			GvNAME_HEK(dstr) = hek_dup(GvNAME_HEK(dstr), param);
+		}
 
 		/* Don't call sv_add_backref here as it's going to be created
 		   as part of the magic cloning of the symbol table.  */
-		GvSTASH(dstr)	= hv_dup(GvSTASH(dstr), param);
+		if(!SvVALID(dstr))
+		    GvSTASH(dstr) = hv_dup(GvSTASH(dstr), param);
 		if(isGV_with_GP(sstr)) {
 		    /* Danger Will Robinson - GvGP(dstr) isn't initialised
 		       at the point of this comment.  */
diff --git a/sv.h b/sv.h
index 0519db59f6..78e8d1b12c 100644
--- a/sv.h
+++ b/sv.h
@@ -48,11 +48,12 @@ typedef enum {
 	SVt_IV,		/* 1 */
 	SVt_NV,		/* 2 */
 	SVt_RV,		/* 3 */
-	SVt_PV,		/* 4 */
-	SVt_PVIV,	/* 5 */
-	SVt_PVNV,	/* 6 */
-	SVt_PVMG,	/* 7 */
-	SVt_PVBM,	/* 8 */
+	SVt_BIND,	/* 4 */
+	SVt_PV,		/* 5 */
+	SVt_PVIV,	/* 6 */
+	SVt_PVNV,	/* 7 */
+	SVt_PVMG,	/* 8 */
+	/* PVBM was here, before BIND replaced it.  */
 	SVt_PVGV,	/* 9 */
 	SVt_PVLV,	/* 10 */
 	SVt_PVAV,	/* 11 */
@@ -63,6 +64,13 @@ typedef enum {
 	SVt_LAST	/* keep last in enum. used to size arrays */
 } svtype;
 
+#ifndef PERL_CORE
+/* Although Fast Boyer Moore tables are now being stored in PVGVs, for most
+   purposes eternal code wanting to consider PVBM probably needs to think of
+   PVMG instead.  */
+#  define SVt_PVBM	SVt_PVMG
+#endif
+
 /* There is collusion here with sv_clear - sv_clear exits early for SVt_NULL
    and SVt_IV, so never reaches the clause at the end that uses
    sv_type_details->body_size to determine whether to call safefree(). Hence
@@ -349,7 +357,7 @@ perform the upgrade if necessary.  See C<svtype>.
 #define SVpav_REAL	0x40000000	/* free old entries */
 /* PVHV */
 #define SVphv_LAZYDEL	0x40000000	/* entry in xhv_eiter must be deleted */
-/* Not just PVBM - basically anything that can be a regular scalar */
+/* Not just "PVBM" (PVGV) - basically anything that can be a regular scalar */
 #define SVpbm_VALID	0x40000000
 /* ??? */
 #define SVrepl_EVAL	0x40000000	/* Replacement part of s///e */
@@ -363,7 +371,7 @@ perform the upgrade if necessary.  See C<svtype>.
 #define SVphv_HASKFLAGS	0x80000000	/* keys have flag byte after hash */
 /* PVFM */
 #define SVpfm_COMPILED	0x80000000	/* FORMLINE is compiled */
-/* PVBM */
+/* PVGV when SVpbm_VALID is true */
 #define SVpbm_TAIL	0x80000000
 /* RV upwards. However, SVf_ROK and SVp_IOK are exclusive  */
 #define SVprv_WEAKREF   0x80000000      /* Weak reference */
@@ -503,6 +511,8 @@ struct xpvlv {
 				 * y=alem/helem/iter t=tie T=tied HE */
 };
 
+/* This structure works in 3 ways - regular scalar, GV with GP, or fast
+   Boyer-Moore.  */
 struct xpvgv {
     union {
 	NV	xnv_nv;
@@ -514,7 +524,7 @@ struct xpvgv {
 	IV	xivu_iv;
 	UV	xivu_uv;
 	void *	xivu_p1;
-	I32	xivu_i32;
+	I32	xivu_i32;	/* is this constant pattern being useful? */
 	HEK *	xivu_namehek;	/* GvNAME */
     }		xiv_u;
     union {
@@ -525,27 +535,6 @@ struct xpvgv {
 
 };
 
-struct xpvbm {
-    union {
-	NV	xnv_nv;		/* numeric value, if any */
-	HV *	xgv_stash;
-    }		xnv_u;
-    STRLEN	xpv_cur;	/* length of svu_pv as a C string */
-    STRLEN	xpv_len;	/* allocated size */
-    union {
-	IV	xivu_iv;	/* integer value or pv offset */
-	UV	xivu_uv;
-	void *	xivu_p1;
-	I32	xivu_i32;	/* is this constant pattern being useful? */
-	HEK *	xivu_namehek;
-    }		xiv_u;
-    union {
-	MAGIC*	xmg_magic;	/* linked list of magicalness */
-	HV*	xmg_ourstash;	/* Stash for our (when SvPAD_OUR is true) */
-    } xmg_u;
-    HV*		xmg_stash;	/* class package */
-};
-
 /* This structure must match XPVCV in cv.h */
 
 typedef U16 cv_flags_t;
@@ -1353,7 +1342,7 @@ the scalar's value cannot change unless written to.
 #if defined (DEBUGGING) && defined(__GNUC__) && !defined(PERL_GCC_BRACE_GROUPS_FORBIDDEN)
 #  define BmRARE(sv)							\
 	(*({ SV *const uggh = (SV *) (sv);				\
-		assert(SvTYPE(uggh) == SVt_PVBM);			\
+		assert(SvTYPE(uggh) == SVt_PVGV);			\
 		assert(SvVALID(uggh));					\
 		assert(SvCUR(uggh) + PERL_FBM_TABLE_OFFSET		\
 		       + PERL_FBM_RARE_OFFSET_FROM_TABLE <= SvLEN(uggh)); \
@@ -1363,14 +1352,14 @@ the scalar's value cannot change unless written to.
 	 }))
 #  define BmUSEFUL(sv)							\
 	(*({ SV *const uggh = (SV *) (sv);				\
-	    assert(SvTYPE(uggh) == SVt_PVBM);				\
+	    assert(SvTYPE(uggh) == SVt_PVGV);				\
 	    assert(SvVALID(uggh));					\
 	    assert(!SvIOK(uggh));					\
-	    &(((XPVBM*) SvANY(uggh))->xiv_u.xivu_i32);			\
+	    &(((XPVGV*) SvANY(uggh))->xiv_u.xivu_i32);			\
 	 }))
 #  define BmPREVIOUS(sv)						\
 	({ SV *const uggh = (SV *) (sv);				\
-	   assert(SvTYPE(uggh) == SVt_PVBM);				\
+	   assert(SvTYPE(uggh) == SVt_PVGV);				\
 	   assert(SvVALID(uggh));					\
 	   assert(SvPOKp(uggh));					\
 	   assert(SvCUR(uggh) + PERL_FBM_TABLE_OFFSET <= SvLEN(uggh));	\
@@ -1384,7 +1373,7 @@ the scalar's value cannot change unless written to.
     (*(U8*)(SvEND(sv)							\
 	    + PERL_FBM_TABLE_OFFSET + PERL_FBM_RARE_OFFSET_FROM_TABLE))
 
-#  define BmUSEFUL(sv)	((XPVBM*)  SvANY(sv))->xiv_u.xivu_i32
+#  define BmUSEFUL(sv)	((XPVGV*)  SvANY(sv))->xiv_u.xivu_i32
 #  define BmPREVIOUS(sv)						\
     ((*(U8*)(SvEND(sv) + PERL_FBM_TABLE_OFFSET				\
 	   + PERL_FBM_PREVIOUS_H_OFFSET_FROM_TABLE) << 8)		\
@@ -1393,7 +1382,7 @@ the scalar's value cannot change unless written to.
 
 #endif
 #define BmPREVIOUS_set(sv, val)						\
-    STMT_START { assert(SvTYPE(sv) == SVt_PVBM);			\
+    STMT_START { assert(SvTYPE(sv) == SVt_PVGV);			\
 	assert(SvVALID(sv));						\
 	assert(SvPOKp(sv));						\
 	assert(SvCUR(sv) + PERL_FBM_TABLE_OFFSET <= SvLEN(sv));		\
diff --git a/util.c b/util.c
index 3cd98c01bf..8dfe417f5e 100644
--- a/util.c
+++ b/util.c
@@ -490,7 +490,7 @@ Perl_fbm_compile(pTHX_ SV *sv, U32 flags)
     s = (U8*)SvPV_force_mutable(sv, len);
     if (len == 0)		/* TAIL might be on a zero-length string. */
 	return;
-    SvUPGRADE(sv, SVt_PVBM);
+    SvUPGRADE(sv, SVt_PVGV);
     SvIOK_off(sv);
     if (len > 2) {
 	const unsigned char *sb;
@@ -665,7 +665,7 @@ Perl_fbm_instr(pTHX_ unsigned char *big, register unsigned char *bigend, SV *lit
 	}
 	return NULL;
     }
-    if (SvTYPE(littlestr) != SVt_PVBM || !SvVALID(littlestr)) {
+    if (!SvVALID(littlestr)) {
 	char * const b = ninstr((char*)big,(char*)bigend,
 			 (char*)little, (char*)little + littlelen);
 
@@ -760,7 +760,8 @@ Perl_screaminstr(pTHX_ SV *bigstr, SV *littlestr, I32 start_shift, I32 end_shift
     register const unsigned char *littleend;
     I32 found = 0;
 
-    assert(SvTYPE(littlestr) == SVt_PVBM);
+    assert(SvTYPE(littlestr) == SVt_PVGV);
+    assert(SvVALID(littlestr));
 
     if (*old_posp == -1
 	? (pos = PL_screamfirst[BmRARE(littlestr)]) < 0