[clippy] Fix a few clippy issues in lib/codegen/;

- don't generate "&& true" when generating instruction eq() fn;
- use more Self;
- use subsec_millis instead of subsec_nanos and divide;
- coalesce two ifs;

lib/codegen/meta/gen_instr.py

@@ -266,7 +266,7 @@ def gen_instruction_data_impl(fmt):
                     n = '&InstructionData::' + f.name
                     members = ['opcode']
                     if f.typevar_operand is None:
-                        args_eq = 'true'
+                        args_eq = None
                     elif f.has_value_list:
                         members.append('args')
                         args_eq = 'args1.as_slice(pool) == ' \
@@ -285,11 +285,12 @@ def gen_instruction_data_impl(fmt):
                                      for x in members)
                     with fmt.indented('({} {{ {} }}, {} {{ {} }}) => {{'
                                       .format(n, pat1, n, pat2), '}'):
-                        fmt.line('opcode1 == opcode2 &&')
+                        fmt.line('opcode1 == opcode2')
                         for field in f.imm_fields:
-                            fmt.line('{}1 == {}2 &&'
+                            fmt.line('&& {}1 == {}2'
                                      .format(field.member, field.member))
-                        fmt.line(args_eq)
+                        if args_eq is not None:
+                            fmt.line('&& {}'.format(args_eq))
                 fmt.line('_ => unsafe { '
                          '::std::hint::unreachable_unchecked() }')
         fmt.line()

lib/codegen/src/fx.rs

@@ -50,8 +50,8 @@ const K: usize = 0x517cc1b727220a95;
 
 impl Default for FxHasher {
     #[inline]
-    fn default() -> FxHasher {
+    fn default() -> Self {
-        FxHasher { hash: 0 }
+        Self { hash: 0 }
     }
 }
 

lib/codegen/src/ir/extname.rs

@@ -111,7 +111,7 @@ impl FromStr for ExternalName {
         // Try to parse as a libcall name, otherwise it's a test case.
         match s.parse() {
             Ok(lc) => Ok(ExternalName::LibCall(lc)),
-            Err(_) => Ok(ExternalName::testcase(s.as_bytes())),
+            Err(_) => Ok(Self::testcase(s.as_bytes())),
         }
     }
 }

lib/codegen/src/timing.rs

@@ -154,8 +154,7 @@ mod details {
                 fn fmtdur(mut dur: Duration, f: &mut fmt::Formatter) -> fmt::Result {
                     // Round to nearest ms by adding 500us.
                     dur += Duration::new(0, 500_000);
-                    let ms = dur.subsec_nanos() / 1_000_000;
+                    write!(f, "{:4}.{:03} ", dur.as_secs(), dur.subsec_millis())
-                    write!(f, "{:4}.{:03} ", dur.as_secs(), ms)
                 }
 
                 fmtdur(time.total, f)?;

lib/codegen/src/verifier/locations.rs

@@ -69,11 +69,9 @@ impl<'a> LocationVerifier<'a> {
                 let opcode = dfg[inst].opcode();
                 if opcode.is_return() {
                     self.check_return_abi(inst, &divert)?;
-                } else if opcode.is_branch() {
+                } else if opcode.is_branch() && !divert.is_empty() {
-                    if !divert.is_empty() {
                     self.check_cfg_edges(inst, &divert)?;
                 }
-                }
 
                 self.update_diversions(inst, &mut divert)?;
             }