Check the pattern before anything else, since it doesn't require metadata

This should partially address #432 by decreasing the number of stat() calls:

    $ strace -c -f ./fd-before '.h$' -j1 /usr -S +1k >/dev/null
    % time     seconds  usecs/call     calls    errors syscall
    ------ ----------- ----------- --------- --------- ----------------
    100.00    3.700169           3    983938     38022 stat
    $ strace -c -f ./fd-after '.h$' -j1 /usr -S +1k >/dev/null
    % time     seconds  usecs/call     calls    errors syscall
    ------ ----------- ----------- --------- --------- ----------------
    100.00    0.671723           4    162052     38021 stat

Though it's not as good as possible:

    $ strace -c -f find /usr -name '*.h' -size +1k >/dev/null
    % time     seconds  usecs/call     calls    errors syscall
    ------ ----------- ----------- --------- --------- ----------------
    18.75    0.449866           3    136199           newfstatat
    $ strace -c -f bfs /usr -name '*.h' -size +1k >/dev/null
    % time     seconds  usecs/call     calls    errors syscall
    ------ ----------- ----------- --------- --------- ----------------
    15.01    0.216024           3     60211         1 statx

Performance is much better when metadata is required:

    $ hyperfine ./fd-{before,after}" '.h$' -j1 /usr -S +1k"
    Benchmark #1: ./fd-before '.h$' -j1 /usr -S +1k
      Time (mean ± σ):      2.707 s ±  0.042 s    [User: 890.8 ms, System: 1939.7 ms]
      Range (min … max):    2.659 s …  2.786 s    10 runs

    Benchmark #2: ./fd-after '.h$' -j1 /usr -S +1k
      Time (mean ± σ):      1.562 s ±  0.034 s    [User: 726.2 ms, System: 957.9 ms]
      Range (min … max):    1.536 s …  1.648 s    10 runs

    Summary
      './fd-after '.h$' -j1 /usr -S +1k' ran
        1.73 ± 0.05 times faster than './fd-before '.h$' -j1 /usr -S +1k'

While remaining the same when it's not:

    tavianator@graviton $ hyperfine ./fd-{before,after}" '.h$' -j1 /usr"
    Benchmark #1: ./fd-before '.h$' -j1 /usr
      Time (mean ± σ):      1.341 s ±  0.016 s    [User: 664.3 ms, System: 761.2 ms]
      Range (min … max):    1.309 s …  1.361 s    10 runs

    Benchmark #2: ./fd-after '.h$' -j1 /usr
      Time (mean ± σ):      1.338 s ±  0.012 s    [User: 684.1 ms, System: 741.1 ms]
      Range (min … max):    1.310 s …  1.350 s    10 runs

    Summary
      './fd-after '.h$' -j1 /usr' ran
        1.00 ± 0.02 times faster than './fd-before '.h$' -j1 /usr'

Author: tavianator

src/walk.rs

@@ -267,6 +267,27 @@ fn spawn_senders(
                 return ignore::WalkState::Continue;
             }
 
+            // Check the name first, since it doesn't require metadata
+
+            let entry_path = entry.path();
+
+            let search_str_o = if config.search_full_path {
+                match fshelper::path_absolute_form(entry_path) {
+                    Ok(path_abs_buf) => Some(path_abs_buf.to_string_lossy().into_owned().into()),
+                    Err(_) => {
+                        print_error_and_exit!("Unable to retrieve absolute path.");
+                    }
+                }
+            } else {
+                entry_path.file_name().map(|f| f.to_string_lossy())
+            };
+
+            if let Some(search_str) = search_str_o {
+                if !pattern.is_match(&*search_str) {
+                    return ignore::WalkState::Continue;
+                }
+            }
+
             // Filter out unwanted file types.
 
             if let Some(ref file_types) = config.file_types {
@@ -294,8 +315,6 @@ fn spawn_senders(
                 }
             }
 
-            let entry_path = entry.path();
-
             // Filter out unwanted extensions.
             if let Some(ref exts_regex) = config.extensions {
                 if let Some(path_str) = entry_path.file_name().and_then(|s| s.to_str()) {
@@ -345,25 +364,10 @@ fn spawn_senders(
                 }
             }
 
-            let search_str_o = if config.search_full_path {
-                match fshelper::path_absolute_form(entry_path) {
-                    Ok(path_abs_buf) => Some(path_abs_buf.to_string_lossy().into_owned().into()),
-                    Err(_) => {
-                        print_error_and_exit!("Unable to retrieve absolute path.");
-                    }
-                }
-            } else {
-                entry_path.file_name().map(|f| f.to_string_lossy())
-            };
-
-            if let Some(search_str) = search_str_o {
-                if pattern.is_match(&*search_str) {
-                    // TODO: take care of the unwrap call
-                    tx_thread
-                        .send(WorkerResult::Entry(entry_path.to_owned()))
-                        .unwrap()
-                }
-            }
+            // TODO: take care of the unwrap call
+            tx_thread
+                .send(WorkerResult::Entry(entry_path.to_owned()))
+                .unwrap();
 
             ignore::WalkState::Continue
         })