Give concrete types to fields of sstatus_csr_t

Doing so allows calls to their members to be inlined.

riscv/csrs.cc

@@ -453,7 +453,7 @@ bool mstatush_csr_t::unlogged_write(const reg_t val) noexcept {
 }
 
 // implement class sstatus_csr_t
-sstatus_csr_t::sstatus_csr_t(processor_t* const proc, base_status_csr_t_p orig, base_status_csr_t_p virt):
+sstatus_csr_t::sstatus_csr_t(processor_t* const proc, sstatus_proxy_csr_t_p orig, vsstatus_csr_t_p virt):
   virtualized_csr_t(proc, orig, virt),
   orig_sstatus(orig),
   virt_sstatus(virt) {

riscv/csrs.h

@@ -263,18 +263,19 @@ class sstatus_proxy_csr_t final: public base_status_csr_t {
   csr_t_p mstatus;
 };
 
+typedef std::shared_ptr<sstatus_proxy_csr_t> sstatus_proxy_csr_t_p;
 
 class sstatus_csr_t: public virtualized_csr_t {
  public:
-  sstatus_csr_t(processor_t* const proc, base_status_csr_t_p orig, base_status_csr_t_p virt);
+  sstatus_csr_t(processor_t* const proc, sstatus_proxy_csr_t_p orig, vsstatus_csr_t_p virt);
 
   // Set FS, VS, or XS bits to dirty
   void dirty(const reg_t dirties);
   // Return true if the specified bits are not 00 (Off)
   bool enabled(const reg_t which);
  private:
-  base_status_csr_t_p orig_sstatus;
-  base_status_csr_t_p virt_sstatus;
+  sstatus_proxy_csr_t_p orig_sstatus;
+  vsstatus_csr_t_p virt_sstatus;
 };
 
 typedef std::shared_ptr<sstatus_csr_t> sstatus_csr_t_p;