Fix dylib metadata writing

Rustc switched from flate2 to snappy

Cargo.lock

@@ -1,11 +1,5 @@
 # This file is automatically @generated by Cargo.
 # It is not intended for manual editing.
-[[package]]
-name = "adler"
-version = "0.2.3"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "ee2a4ec343196209d6594e19543ae87a39f96d5534d7174822a3ad825dd6ed7e"
-
 [[package]]
 name = "ahash"
 version = "0.4.4"
@@ -188,18 +182,6 @@ dependencies = [
  "libc",
 ]
 
-[[package]]
-name = "flate2"
-version = "1.0.17"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "766d0e77a2c1502169d4a93ff3b8c15a71fd946cd0126309752104e5f3c46d94"
-dependencies = [
- "cfg-if",
- "crc32fast",
- "libc",
- "miniz_oxide",
-]
-
 [[package]]
 name = "gcc"
 version = "0.3.55"
@@ -276,15 +258,6 @@ dependencies = [
  "libc",
 ]
 
-[[package]]
-name = "miniz_oxide"
-version = "0.4.1"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "4d7559a8a40d0f97e1edea3220f698f78b1c5ab67532e49f68fde3910323b722"
-dependencies = [
- "adler",
-]
-
 [[package]]
 name = "object"
 version = "0.21.1"
@@ -366,7 +339,6 @@ dependencies = [
  "cranelift-module",
  "cranelift-object",
  "cranelift-simplejit",
- "flate2",
  "gimli",
  "hashbrown 0.9.0",
  "indexmap",

Cargo.toml

@@ -24,7 +24,6 @@ indexmap = "1.0.2"
 cfg-if = "0.1.10"
 libloading = { version = "0.6.0", optional = true }
 hashbrown = "0.9.0"
-flate2 = "1.0.17"
 
 # Uncomment to use local checkout of cranelift
 #[patch."https://github.com/bytecodealliance/wasmtime/"]

src/lib.rs

@@ -11,6 +11,7 @@
 
 #[cfg(feature = "jit")]
 extern crate libc;
+extern crate snap;
 #[macro_use]
 extern crate rustc_middle;
 extern crate rustc_ast;

src/metadata.rs

@@ -63,8 +63,7 @@ pub(crate) fn write_metadata<P: WriteMetadata>(
     tcx: TyCtxt<'_>,
     product: &mut P,
 ) -> EncodedMetadata {
-    use flate2::write::DeflateEncoder;
-    use flate2::Compression;
+    use snap::write::FrameEncoder;
     use std::io::Write;
 
     #[derive(PartialEq, Eq, PartialOrd, Ord)]
@@ -101,7 +100,7 @@ pub(crate) fn write_metadata<P: WriteMetadata>(
 
     assert!(kind == MetadataKind::Compressed);
     let mut compressed = tcx.metadata_encoding_version();
-    DeflateEncoder::new(&mut compressed, Compression::fast())
+    FrameEncoder::new(&mut compressed)
         .write_all(&metadata.raw_data)
         .unwrap();