Support setting ISA/subsets with --isa flag

Default is RV64IMAFDC.  Can do things like

  --isa=RV32 (which implies IMAFDC)
  --isa=IM (which implies RV64)
  --isa=RV64IMAFDXhwacha

1 files changed, 35 insertions, 0 deletions

diff --git a/riscv/extensions.cc b/riscv/extensions.cc
new file mode 100644
index 0000000..315621f
--- /dev/null
+++ b/riscv/extensions.cc
@@ -0,0 +1,35 @@
+#include "extension.h"
+#include <string>
+#include <map>
+#include <dlfcn.h>
+
+static std::map<std::string, std::function<extension_t*()>>& extensions()
+{
+  static std::map<std::string, std::function<extension_t*()>> v;
+  return v;
+}
+
+void register_extension(const char* name, std::function<extension_t*()> f)
+{
+  extensions()[name] = f;
+}
+
+std::function<extension_t*()> find_extension(const char* name)
+{
+  if (!extensions().count(name)) {
+    // try to find extension xyz by loading libxyz.so
+    std::string libname = std::string("lib") + name + ".so";
+    if (!dlopen(libname.c_str(), RTLD_LAZY)) {
+      fprintf(stderr, "couldn't find extension '%s' (or library '%s')\n",
+              name, libname.c_str());
+      exit(-1);
+    }
+    if (!extensions().count(name)) {
+      fprintf(stderr, "couldn't find extension '%s' in shared library '%s'\n",
+              name, libname.c_str());
+      exit(-1);
+    }
+  }
+
+  return extensions()[name];
+}