Coalesce adjacent physical mappings.

This reduces the overhead when we have many small mappings, e.g. on some
EFI systems. This is to help use this code on arm64 where we may have a
large number of entries from the EFI firmware.

Obtained from:	ABT Systems Ltd
Sponsored by:	Turing Robotic Industries
Differential Revision:	https://reviews.freebsd.org/D15477

sys/arm/arm/physmem.c

@@ -216,8 +216,13 @@ regions_to_avail(vm_paddr_t *avail, uint32_t exflags, long *pavail)
 			 * could affect the remainder of this hw region.
 			 */
 			if ((xstart > start) && (xend < end)) {
-				avail[acnt++] = (vm_paddr_t)start;
-				avail[acnt++] = (vm_paddr_t)xstart;
+				if (acnt > 0 &&
+				    avail[acnt - 1] == (vm_paddr_t)start) {
+					avail[acnt - 1] = (vm_paddr_t)xstart;
+				} else {
+					avail[acnt++] = (vm_paddr_t)start;
+					avail[acnt++] = (vm_paddr_t)xstart;
+				}
 				availmem += 
 				    arm32_btop((vm_offset_t)(xstart - start));
 				start = xend;
@@ -238,8 +243,12 @@ regions_to_avail(vm_paddr_t *avail, uint32_t exflags, long *pavail)
 		 * available entry for it.
 		 */
 		if (end > start) {
-			avail[acnt++] = (vm_paddr_t)start;
-			avail[acnt++] = (vm_paddr_t)end;
+			if (acnt > 0 && avail[acnt - 1] == (vm_paddr_t)start) {
+				avail[acnt - 1] = (vm_paddr_t)end;
+			} else {
+				avail[acnt++] = (vm_paddr_t)start;
+				avail[acnt++] = (vm_paddr_t)end;
+			}
 			availmem += arm32_btop((vm_offset_t)(end - start));
 		}
 		if (acnt >= MAX_AVAIL_ENTRIES)
@@ -254,7 +263,7 @@ regions_to_avail(vm_paddr_t *avail, uint32_t exflags, long *pavail)
 /*
  * Insertion-sort a new entry into a regions list; sorted by start address.
  */
-static void
+static size_t
 insert_region(struct region *regions, size_t rcnt, vm_paddr_t addr,
     vm_size_t size, uint32_t flags)
 {
@@ -263,6 +272,16 @@ insert_region(struct region *regions, size_t rcnt, vm_paddr_t addr,
 
 	ep = regions + rcnt;
 	for (i = 0, rp = regions; i < rcnt; ++i, ++rp) {
+		if (flags == rp->flags) {
+			if (addr + size == rp->addr) {
+				rp->addr = addr;
+				rp->size += size;
+				return (rcnt);
+			} else if (rp->addr + rp->size == addr) {
+				rp->size += size;
+				return (rcnt);
+			}
+		}
 		if (addr < rp->addr) {
 			bcopy(rp, rp + 1, (ep - rp) * sizeof(*rp));
 			break;
@@ -271,6 +290,9 @@ insert_region(struct region *regions, size_t rcnt, vm_paddr_t addr,
 	rp->addr  = addr;
 	rp->size  = size;
 	rp->flags = flags;
+	rcnt++;
+
+	return (rcnt);
 }
 
 /*
@@ -322,7 +344,7 @@ arm_physmem_hardware_region(uint64_t pa, uint64_t sz)
 	sz  = trunc_page(sz - adj);
 
 	if (sz > 0 && hwcnt < nitems(hwregions))
-		insert_region(hwregions, hwcnt++, pa, sz, 0);
+		hwcnt = insert_region(hwregions, hwcnt, pa, sz, 0);
 }
 
 /*
@@ -341,7 +363,7 @@ void arm_physmem_exclude_region(vm_paddr_t pa, vm_size_t sz, uint32_t exflags)
 	sz  = round_page(sz + adj);
 
 	if (excnt < nitems(exregions))
-		insert_region(exregions, excnt++, pa, sz, exflags);
+		excnt = insert_region(exregions, excnt, pa, sz, exflags);
 }
 
 /*