[build] Move settings generation from Python to Rust code;

lib/codegen/meta/src/gen_registers.rs

@@ -78,7 +78,7 @@ fn gen_regbank_units(reg_bank: &RegBank, fmt: &mut Formatter) {
     }
 }
 
-fn gen_isa(isa: &TargetIsa, fmt: &mut Formatter) -> Result<(), error::Error> {
+fn gen_isa(isa: &TargetIsa, fmt: &mut Formatter) {
     // Emit RegInfo.
     fmt.line("pub static INFO: RegInfo = RegInfo {");
 
@@ -128,13 +128,11 @@ fn gen_isa(isa: &TargetIsa, fmt: &mut Formatter) -> Result<(), error::Error> {
         fmt.line("}")
     });
     fmt.line("}");
-
-    Ok(())
 }
 
-pub fn generate(isa: TargetIsa, base_filename: &str, out_dir: &str) -> Result<(), error::Error> {
+pub fn generate(isa: &TargetIsa, base_filename: &str, out_dir: &str) -> Result<(), error::Error> {
     let mut fmt = Formatter::new();
-    gen_isa(&isa, &mut fmt)?;
+    gen_isa(&isa, &mut fmt);
     fmt.update_file(&format!("{}-{}.rs", base_filename, isa.name), out_dir)?;
     Ok(())
 }