Revert "perf: disable TSC snapshot compression (#18333)" (#18336)

This reverts commit 0d27de943a60f5ca60e2116648719c235163361a.

1 files changed, 25 insertions, 3 deletions

diff --git a/cli/tsc/mod.rs b/cli/tsc/mod.rs
index 60ef1c5d6..43fccb37e 100644
--- a/cli/tsc/mod.rs
+++ b/cli/tsc/mod.rs
@@ -52,8 +52,30 @@ pub use self::diagnostics::DiagnosticMessageChain;
 pub use self::diagnostics::Diagnostics;
 pub use self::diagnostics::Position;
 
-pub static COMPILER_SNAPSHOT: &[u8] =
-  include_bytes!(concat!(env!("OUT_DIR"), "/COMPILER_SNAPSHOT.bin"));
+pub static COMPILER_SNAPSHOT: Lazy<Box<[u8]>> = Lazy::new(
+  #[cold]
+  #[inline(never)]
+  || {
+    static COMPRESSED_COMPILER_SNAPSHOT: &[u8] =
+      include_bytes!(concat!(env!("OUT_DIR"), "/COMPILER_SNAPSHOT.bin"));
+
+    // NOTE(bartlomieju): Compressing the TSC snapshot in debug build took
+    // ~45s on M1 MacBook Pro; without compression it took ~1s.
+    // Thus we're not not using compressed snapshot, trading off
+    // a lot of build time for some startup time in debug build.
+    #[cfg(debug_assertions)]
+    return COMPRESSED_COMPILER_SNAPSHOT.to_vec().into_boxed_slice();
+
+    #[cfg(not(debug_assertions))]
+    zstd::bulk::decompress(
+      &COMPRESSED_COMPILER_SNAPSHOT[4..],
+      u32::from_le_bytes(COMPRESSED_COMPILER_SNAPSHOT[0..4].try_into().unwrap())
+        as usize,
+    )
+    .unwrap()
+    .into_boxed_slice()
+  },
+);
 
 pub fn get_types_declaration_file_text(unstable: bool) -> String {
   let mut assets = get_asset_texts_from_new_runtime()
@@ -115,7 +137,7 @@ fn get_asset_texts_from_new_runtime() -> Result<Vec<AssetText>, AnyError> {
 }
 
 pub fn compiler_snapshot() -> Snapshot {
-  Snapshot::Static(COMPILER_SNAPSHOT)
+  Snapshot::Static(&COMPILER_SNAPSHOT)
 }
 
 macro_rules! inc {