Auto merge of #54864 - ljedrz:cleanup_codegen_llvm_back, r=Mark-Simulacrum

Cleanup codegen_llvm/back

- improve allocations
- use `Cow<'static, str>` where applicable
- use `to_owned` instead of `to_string` with string literals
- remove a redundant `continue`
- possible minor speedup in logic
- use `mem::replace` instead of `swap` where more concise
- remove `'static` from consts
- improve common patterns
- remove explicit `return`s
- whitespace & formatting fixes

1 files changed, 9 insertions, 9 deletions

diff --git a/src/librustc_codegen_llvm/back/bytecode.rs b/src/librustc_codegen_llvm/back/bytecode.rs
index 9a3dd9d2f88..0b264de18c1 100644
--- a/src/librustc_codegen_llvm/back/bytecode.rs
+++ b/src/librustc_codegen_llvm/back/bytecode.rs
@@ -42,7 +42,7 @@ use flate2::write::DeflateEncoder;
 
 // This is the "magic number" expected at the beginning of a LLVM bytecode
 // object in an rlib.
-pub const RLIB_BYTECODE_OBJECT_MAGIC: &'static [u8] = b"RUST_OBJECT";
+pub const RLIB_BYTECODE_OBJECT_MAGIC: &[u8] = b"RUST_OBJECT";
 
 // The version number this compiler will write to bytecode objects in rlibs
 pub const RLIB_BYTECODE_OBJECT_VERSION: u8 = 2;
@@ -106,39 +106,39 @@ pub struct DecodedBytecode<'a> {
 }
 
 impl<'a> DecodedBytecode<'a> {
-    pub fn new(data: &'a [u8]) -> Result<DecodedBytecode<'a>, String> {
+    pub fn new(data: &'a [u8]) -> Result<DecodedBytecode<'a>, &'static str> {
         if !data.starts_with(RLIB_BYTECODE_OBJECT_MAGIC) {
-            return Err("magic bytecode prefix not found".to_string())
+            return Err("magic bytecode prefix not found")
         }
         let data = &data[RLIB_BYTECODE_OBJECT_MAGIC.len()..];
         if !data.starts_with(&[RLIB_BYTECODE_OBJECT_VERSION, 0, 0, 0]) {
-            return Err("wrong version prefix found in bytecode".to_string())
+            return Err("wrong version prefix found in bytecode")
         }
         let data = &data[4..];
         if data.len() < 4 {
-            return Err("bytecode corrupted".to_string())
+            return Err("bytecode corrupted")
         }
         let identifier_len = unsafe {
             u32::from_le(ptr::read_unaligned(data.as_ptr() as *const u32)) as usize
         };
         let data = &data[4..];
         if data.len() < identifier_len {
-            return Err("bytecode corrupted".to_string())
+            return Err("bytecode corrupted")
         }
         let identifier = match str::from_utf8(&data[..identifier_len]) {
             Ok(s) => s,
-            Err(_) => return Err("bytecode corrupted".to_string())
+            Err(_) => return Err("bytecode corrupted")
         };
         let data = &data[identifier_len..];
         if data.len() < 8 {
-            return Err("bytecode corrupted".to_string())
+            return Err("bytecode corrupted")
         }
         let bytecode_len = unsafe {
             u64::from_le(ptr::read_unaligned(data.as_ptr() as *const u64)) as usize
         };
         let data = &data[8..];
         if data.len() < bytecode_len {
-            return Err("bytecode corrupted".to_string())
+            return Err("bytecode corrupted")
         }
         let encoded_bytecode = &data[..bytecode_len];