Fix Cachegrind diff output file names.

collector/src/bin/collector.rs

@@ -196,9 +196,10 @@ fn generate_diffs(
                 };
                 let id_diff = format!("{id1}-{id2}");
                 let prefix = profiler.prefix();
+                let prefix2 = profiler.prefix2();
                 let left = out_dir.join(filename(prefix, id1));
                 let right = out_dir.join(filename(prefix, id2));
-                let output = out_dir.join(filename(&format!("{prefix}-diff"), &id_diff));
+                let output = out_dir.join(filename(&format!("{prefix2}-diff"), &id_diff));
 
                 if let Err(e) = profiler.diff(&left, &right, &output) {
                     errors.incr();
@@ -1142,7 +1143,7 @@ fn main_result() -> anyhow::Result<i32> {
                     &profiler,
                 );
                 if let [diff] = &diffs[..] {
-                    let short = out_dir.join(format!("{}-diff-latest", profiler.prefix()));
+                    let short = out_dir.join(format!("{}-diff-latest", profiler.prefix2()));
                     std::fs::copy(diff, &short).expect("copy to short path");
                     eprintln!("Original diff at: {}", diff.to_string_lossy());
                     eprintln!("Short path: {}", short.to_string_lossy());

collector/src/compile/execute/profiler.rs

@@ -65,6 +65,18 @@ impl Profiler {
         }
     }
 
+    /// A file prefix added to all (second-stage) files of this profiler.
+    pub fn prefix2(&self) -> &'static str {
+        use Profiler::*;
+        match self {
+            Cachegrind => "cgann",
+            DepGraph => "dep-graph",
+
+            SelfProfile | PerfRecord | Oprofile | Samply | Callgrind | Dhat | DhatCopy | Massif
+            | Bytehound | Eprintln | LlvmLines | MonoItems | LlvmIr => "",
+        }
+    }
+
     /// A postfix added to the file that gets diffed.
     pub fn postfix(&self) -> &'static str {
         use Profiler::*;