When saving ints, if the value is small enough save it with the type.

This uses a new type, SAVEt_INT_SMALL.

scope.c

@@ -392,10 +392,16 @@ void
 Perl_save_int(pTHX_ int *intp)
 {
     dVAR;
+    const UV shifted = (UV)*intp << SAVE_TIGHT_SHIFT;
 
     PERL_ARGS_ASSERT_SAVE_INT;
 
-    save_pushi32ptr(*intp, intp, SAVEt_INT);
+    if ((int)(shifted >> SAVE_TIGHT_SHIFT) == *intp) {
+	SSCHECK(2);
+	SSPUSHPTR(intp);
+	SSPUSHUV(SAVEt_INT_SMALL | shifted);
+    } else
+	save_pushi32ptr(*intp, intp, SAVEt_INT);
 }
 
 void
@@ -802,6 +808,10 @@ Perl_leave_scope(pTHX_ I32 base)
 		PL_localizing = 0;
 	    }
 	    break;
+	case SAVEt_INT_SMALL:
+	    ptr = SSPOPPTR;
+	    *(int*)ptr = (int)(uv >> SAVE_TIGHT_SHIFT);
+	    break;
 	case SAVEt_INT:				/* int reference */
 	    ptr = SSPOPPTR;
 	    *(int*)ptr = (int)SSPOPINT;

scope.h

@@ -56,6 +56,7 @@
 #define SAVEt_PARSER		45
 #define SAVEt_ADELETE		46
 #define SAVEt_I32_SMALL		47
+#define SAVEt_INT_SMALL		48
 
 #define SAVEf_SETMAGIC		1
 #define SAVEf_KEEPOLDELEM	2

sv.c

@@ -11583,6 +11583,7 @@ Perl_ss_dup(pTHX_ PerlInterpreter *proto_perl, CLONE_PARAMS* param)
 	    ptr = POPPTR(ss,ix);
 	    TOPPTR(nss,ix) = any_dup(ptr, proto_perl);
 	    /* Fall through */
+	case SAVEt_INT_SMALL:
 	case SAVEt_I32_SMALL:
 	case SAVEt_I16:				/* I16 reference */
 	case SAVEt_I8:				/* I8 reference */