Remove op_const_class; just use the name on the stack

Instead of storing the class name in the op_const_class field of the
METHOP in addition to pushing it on to the stack, just use the item on
the stack.  This also makes $class->method faster if $class is already
a shared hash string.

op.c

@@ -861,16 +861,6 @@ Perl_op_clear(pTHX_ OP *o)
             pad_swipe(o->op_targ, 1);
             o->op_targ = 0;
         }
-#endif
-    case OP_METHOD:
-#ifdef USE_ITHREADS
-	if (cMETHOPx(o)->op_class_targ) {
-	    pad_swipe(cMETHOPx(o)->op_class_targ, 1);
-	    cMETHOPx(o)->op_class_targ = 0;
-	}
-#else
-	SvREFCNT_dec(cMETHOPx(o)->op_class_sv);
-	cMETHOPx(o)->op_class_sv = NULL;
 #endif
         break;
     case OP_CONST:
@@ -4692,11 +4682,6 @@ S_newMETHOP_internal(pTHX_ I32 type, I32 flags, OP* dynamic_meth, SV* const_meth
         methop->op_next = (OP*)methop;
     }
 
-#ifdef USE_ITHREADS
-    methop->op_class_targ = 0;
-#else
-    methop->op_class_sv = NULL;
-#endif
     CHANGE_TYPE(methop, type);
     methop = (METHOP*) CHECKOP(type, methop);
 
@@ -11592,7 +11577,7 @@ Perl_ck_subr(pTHX_ OP *o)
     OP *aop, *cvop;
     CV *cv;
     GV *namegv;
-    SV *const_class = NULL;
+    SV **const_class = NULL;
 
     PERL_ARGS_ASSERT_CK_SUBR;
 
@@ -11618,29 +11603,26 @@ Perl_ck_subr(pTHX_ OP *o)
 	case OP_METHOD_NAMED:
 	    if (aop->op_type == OP_CONST) {
 		aop->op_private &= ~OPpCONST_STRICT;
-		const_class = cSVOPx(aop)->op_sv;
+		const_class = &cSVOPx(aop)->op_sv;
 	    }
 	    else if (aop->op_type == OP_LIST) {
 		OP * const sib = OP_SIBLING(((UNOP*)aop)->op_first);
 		if (sib && sib->op_type == OP_CONST) {
 		    sib->op_private &= ~OPpCONST_STRICT;
-		    const_class = cSVOPx(sib)->op_sv;
+		    const_class = &cSVOPx(sib)->op_sv;
 		}
 	    }
-	    /* cache const class' name to speedup class method calls */
-	    if (const_class) {
+	    /* make class name a shared cow string to speedup method calls */
+	    /* constant string might be replaced with object, f.e. bigint */
+	    if (const_class && !SvROK(*const_class)) {
 		STRLEN len;
-		SV* shared;
-		const char* str = SvPV(const_class, len);
+		const char* str = SvPV(*const_class, len);
 		if (len) {
-		    shared = newSVpvn_share(
-			str, SvUTF8(const_class) ? -len : len, 0
+		    SV* const shared = newSVpvn_share(
+			str, SvUTF8(*const_class) ? -len : len, 0
 		    );
-#ifdef USE_ITHREADS
-		    op_relocate_sv(&shared, &cMETHOPx(cvop)->op_class_targ);
-#else
-		    cMETHOPx(cvop)->op_class_sv = shared;
-#endif
+		    SvREFCNT_dec(*const_class);
+		    *const_class = shared;
 		}
 	    }
 	    break;

op.h

@@ -202,11 +202,6 @@ struct methop {
         OP* op_first;   /* optree for method name */
         SV* op_meth_sv; /* static method name */
     } op_u;
-#ifdef USE_ITHREADS
-    PADOFFSET op_class_targ; /* pad index for class name if threaded */
-#else
-    SV*       op_class_sv;   /* static class name */
-#endif
 };
 
 struct pmop {
@@ -446,8 +441,6 @@ struct loop {
 				 ? cSVOPx(v)->op_sv : PAD_SVl((v)->op_targ))
 #  define	cSVOPx_svp(v)	(cSVOPx(v)->op_sv \
 				 ? &cSVOPx(v)->op_sv : &PAD_SVl((v)->op_targ))
-#  define	cMETHOPx_class(v) (cMETHOPx(v)->op_class_targ ? \
-	PAD_SVl(cMETHOPx(v)->op_class_targ) : NULL)
 #else
 #  define	cGVOPx_gv(o)	((GV*)cSVOPx(o)->op_sv)
 #  ifndef PERL_CORE
@@ -456,7 +449,6 @@ struct loop {
 #  endif
 #  define	cSVOPx_sv(v)	(cSVOPx(v)->op_sv)
 #  define	cSVOPx_svp(v)	(&cSVOPx(v)->op_sv)
-#  define       cMETHOPx_class(v) (cMETHOPx(v)->op_class_sv)
 #endif
 
 #  define	cMETHOPx_meth(v)	cSVOPx_sv(v)

pp_hot.c

@@ -3006,27 +3006,27 @@ S_method_common(pTHX_ SV* meth, U32* hashp)
     SV* ob;
     GV* gv;
     HV* stash;
-    SV *packsv = NULL, *const_class, *sv;
+    SV *packsv = NULL;
 
-    PERL_ARGS_ASSERT_METHOD_COMMON;
-
-    if ((const_class = cMETHOPx_class(PL_op))) {
-	stash = gv_stashsv(const_class, GV_CACHE_ONLY);
-	if (stash) goto fetch;
-    }
-
-    sv = PL_stack_base + TOPMARK == PL_stack_sp
+    SV* const sv = PL_stack_base + TOPMARK == PL_stack_sp
 	? (Perl_croak(aTHX_ "Can't call method \"%"SVf"\" without a "
 			    "package or object reference", SVfARG(meth)),
 	   (SV *)NULL)
 	: *(PL_stack_base + TOPMARK + 1);
 
+    PERL_ARGS_ASSERT_METHOD_COMMON;
+
     if (UNLIKELY(!sv))
        undefined:
 	Perl_croak(aTHX_ "Can't call method \"%"SVf"\" on an undefined value",
 		   SVfARG(meth));
 
-    SvGETMAGIC(sv);
+    if (UNLIKELY(SvGMAGICAL(sv))) mg_get(sv);
+    else if (SvIsCOW_shared_hash(sv)) { /* MyClass->meth() */
+	stash = gv_stashsv(sv, GV_CACHE_ONLY);
+	if (stash) goto fetch;
+    }
+
     if (SvROK(sv))
 	ob = MUTABLE_SV(SvRV(sv));
     else if (!SvOK(sv)) goto undefined;