Alternative cluster size computation

I believe that this computes the correct size for a cluster that
contains overlapping registers (such as the ATSAMD21G that I've
added to the tests in this commit).

It comes at the cost of not recognizing the overlapping registers
at that stage.

Author: wez

src/generate/peripheral.rs

@@ -197,40 +197,27 @@ fn expand(
     Ok(ercs_expanded)
 }
 
-/// Recursively calculate the size of a cluster. A cluster's size is the sum of
-/// all of its children clusters and registers
+/// Recursively calculate the size of a cluster. A cluster's size is the maximum
+/// end position of its recursive children.
 fn cluster_size_in_bits(info: &ClusterInfo, defs: &Defaults) -> Result<u32> {
-    // Cluster size is the summation of the size of each of the cluster's children.
-    let mut offset = 0;
     let mut size = 0;
 
     for c in &info.children {
-        size += match *c {
+        let end = match *c {
             Either::Left(ref reg) => {
-                let pad = reg.address_offset.checked_sub(offset)
-                .ok_or_else(||
-                    format!("Warning! overlap while calculating Register Size within a Cluster! Cluster contents may be incorrectly aligned!"))?
-                * BITS_PER_BYTE;
-
-
                 let reg_size: u32 = expand_register(reg, defs, None)?
                     .iter()
                     .map(|rbf| rbf.size)
                     .sum();
 
-                pad + reg_size
+                (reg.address_offset * BITS_PER_BYTE) + reg_size
             }
             Either::Right(ref clust) => {
-                let pad = clust.address_offset.checked_sub(offset)
-                    .ok_or_else(||
-                        format!("Warning! overlap while calculating Cluster Size within a Cluster! Cluster contents may be incorrectly aligned!"))?
-                    * BITS_PER_BYTE;
-
-                pad + cluster_size_in_bits(clust, defs)?
+                (clust.address_offset * BITS_PER_BYTE) + cluster_size_in_bits(clust, defs)?
             }
         };
 
-        offset = size / BITS_PER_BYTE;
+        size = size.max(end);
     }
     Ok(size)
 }