Refactor loops in S_hsplit(), Perl_hv_ksplit() and Perl_ptr_table_spl…

…it().

Change from for() to do ... while() loops. Move variable initialisation to
variable declaration. Avoid needing to use the comma operator to allow
multiple statements in for(). Avoid using a continue statement where it
isn't actually needed to change flow control. Avoid relying on the optimiser
to know that the for loop conditional doesn't need testing on the first pass.

A current gcc's optimiser produces identical code despite these changes.
However, for the reasons given I consider the code to be much clearer.

hv.c

@@ -1148,19 +1148,19 @@ S_hsplit(pTHX_ HV *hv)
 	if (!entry)				/* non-existent */
 	    continue;
 	bep = aep+oldsize;
-	for (; entry; entry = *oentry) {
+	do {
 	    if ((HeHASH(entry) & newsize) != (U32)i) {
 		*oentry = HeNEXT(entry);
 		HeNEXT(entry) = *bep;
 		*bep = entry;
 		right_length++;
-		continue;
 	    }
 	    else {
 		oentry = &HeNEXT(entry);
 		left_length++;
 	    }
-	}
+	    entry = *oentry;
+	} while (entry);
 	/* I think we don't actually need to keep track of the longest length,
 	   merely flag if anything is too long. But for the moment while
 	   developing this code I'll track it.  */
@@ -1314,19 +1314,19 @@ Perl_hv_ksplit(pTHX_ HV *hv, IV newmax)
 
 	if (!entry)				/* non-existent */
 	    continue;
-	for (; entry; entry = *oentry) {
+	do {
 	    register I32 j = (HeHASH(entry) & newsize);
 
 	    if (j != i) {
 		j -= i;
 		*oentry = HeNEXT(entry);
 		HeNEXT(entry) = aep[j];
 		aep[j] = entry;
-		continue;
 	    }
 	    else
 		oentry = &HeNEXT(entry);
-	}
+	    entry = *oentry;
+	} while (entry);
     }
 }
 

sv.c

@@ -10875,20 +10875,22 @@ Perl_ptr_table_split(pTHX_ PTR_TBL_t *const tbl)
     tbl->tbl_max = --newsize;
     tbl->tbl_ary = ary;
     for (i=0; i < oldsize; i++, ary++) {
-	PTR_TBL_ENT_t **curentp, **entp, *ent;
-	if (!*ary)
+	PTR_TBL_ENT_t **entp = ary;
+	PTR_TBL_ENT_t *ent = *ary;
+	PTR_TBL_ENT_t **curentp;
+	if (!ent)
 	    continue;
 	curentp = ary + oldsize;
-	for (entp = ary, ent = *ary; ent; ent = *entp) {
+	do {
 	    if ((newsize & PTR_TABLE_HASH(ent->oldval)) != i) {
 		*entp = ent->next;
 		ent->next = *curentp;
 		*curentp = ent;
-		continue;
 	    }
 	    else
 		entp = &ent->next;
-	}
+	    ent = *entp;
+	} while (ent);
     }
 }