Rewrite sstatus_csr_t::enabled() for higher performance

Eliminate calls to base_status_csr_t::enabled() so that the various
read() calls can be inlined.  Doing so also removes a redundant check of
sstatus_write_mask.

Schedule the most common exit path first.

1 files changed, 5 insertions, 2 deletions

diff --git a/riscv/csrs.h b/riscv/csrs.h
index c0f5771..946d06c 100644
--- a/riscv/csrs.h
+++ b/riscv/csrs.h
@@ -185,8 +185,11 @@ class cause_csr_t: public basic_csr_t {
 class base_status_csr_t: public csr_t {
  public:
   base_status_csr_t(processor_t* const proc, const reg_t addr);
-  // Return true if the specified bits are not 00 (Off)
-  bool enabled(const reg_t which);
+
+  bool field_exists(const reg_t which) {
+    return (sstatus_write_mask & which) != 0;
+  }
+
  protected:
   reg_t adjust_sd(const reg_t val) const noexcept;
   void maybe_flush_tlb(const reg_t newval) noexcept;