Don't go through the formatting infrastructure just to get the name of a phase

compiler/rustc_middle/src/mir/mod.rs

@@ -184,30 +184,7 @@ impl RuntimePhase {
 
 impl Display for MirPhase {
     fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
-        match self {
+        f.write_str(self.name())
-            MirPhase::Built => write!(f, "built"),
-            MirPhase::Analysis(p) => write!(f, "analysis-{}", p),
-            MirPhase::Runtime(p) => write!(f, "runtime-{}", p),
-        }
-    }
-}
-
-impl Display for AnalysisPhase {
-    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
-        match self {
-            AnalysisPhase::Initial => write!(f, "initial"),
-            AnalysisPhase::PostCleanup => write!(f, "post_cleanup"),
-        }
-    }
-}
-
-impl Display for RuntimePhase {
-    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
-        match self {
-            RuntimePhase::Initial => write!(f, "initial"),
-            RuntimePhase::PostCleanup => write!(f, "post_cleanup"),
-            RuntimePhase::Optimized => write!(f, "optimized"),
-        }
     }
 }
 

compiler/rustc_middle/src/mir/syntax.rs

@@ -89,6 +89,19 @@ pub enum MirPhase {
     Runtime(RuntimePhase),
 }
 
+impl MirPhase {
+    pub fn name(&self) -> &'static str {
+        match *self {
+            MirPhase::Built => "built",
+            MirPhase::Analysis(AnalysisPhase::Initial) => "analysis",
+            MirPhase::Analysis(AnalysisPhase::PostCleanup) => "analysis-post-cleanup",
+            MirPhase::Runtime(RuntimePhase::Initial) => "runtime",
+            MirPhase::Runtime(RuntimePhase::PostCleanup) => "runtime-post-cleanup",
+            MirPhase::Runtime(RuntimePhase::Optimized) => "runtime-optimized",
+        }
+    }
+}
+
 /// See [`MirPhase::Analysis`].
 #[derive(Copy, Clone, TyEncodable, TyDecodable, Debug, PartialEq, Eq, PartialOrd, Ord)]
 #[derive(HashStable)]

compiler/rustc_mir_transform/src/pass_manager.rs

@@ -184,7 +184,7 @@ pub fn dump_mir_for_phase_change<'tcx>(tcx: TyCtxt<'tcx>, body: &Body<'tcx>) {
     mir::dump_mir(
         tcx,
         Some(&format_args!("{:03}-000", phase_index)),
-        &format!("{}", body.phase),
+        body.phase.name(),
         &"after",
         body,
         |_, _| Ok(()),