Address review comments:

- Undo temporary changes to default features (`all-arch`) and a
  signal-handler test.
- Remove `SIGTRAP` handler: no longer needed now that we've found an
  "undefined opcode" option on ARM64.
- Rename pp.rs to pretty_print.rs in machinst/.
- Only use empty stack-probe on non-x86. As per a comment in
  rust-lang/compiler-builtins [1], LLVM only supports stack probes on
  x86 and x86-64. Thus, on any other CPU architecture, we cannot refer
  to `__rust_probestack`, because it does not exist.
- Rename arm64 to aarch64.
- Use `target` directive in vcode filetests.
- Run the flags verifier, but without encinfo, when using new backends.
- Clean up warning overrides.
- Fix up use of casts: use u32::from(x) and siblings when possible,
  u32::try_from(x).unwrap() when not, to avoid silent truncation.
- Take immutable `Function` borrows as input; we don't actually
  mutate the input IR.
- Lots of other miscellaneous cleanups.

[1] cae3e6ea23/src/probestack.rs (L39)

cranelift/codegen/src/machinst/sections.rs

@@ -3,7 +3,7 @@
 //! simultaneously, so we buffer the result in memory and hand off to the
 //! caller at the end of compilation.
 
-use crate::binemit::{Addend, CodeOffset, CodeSink, Reloc, RelocSink, StackmapSink, TrapSink};
+use crate::binemit::{Addend, CodeOffset, CodeSink, Reloc};
 use crate::ir::{ExternalName, Opcode, SourceLoc, TrapCode};
 
 use alloc::vec::Vec;
@@ -104,28 +104,31 @@ pub trait MachSectionOutput {
 
     /// Add 2 bytes to the section.
     fn put2(&mut self, value: u16) {
-        self.put1((value & 0xff) as u8);
-        self.put1(((value >> 8) & 0xff) as u8);
+        let [b0, b1] = value.to_le_bytes();
+        self.put1(b0);
+        self.put1(b1);
     }
 
     /// Add 4 bytes to the section.
     fn put4(&mut self, value: u32) {
-        self.put1((value & 0xff) as u8);
-        self.put1(((value >> 8) & 0xff) as u8);
-        self.put1(((value >> 16) & 0xff) as u8);
-        self.put1(((value >> 24) & 0xff) as u8);
+        let [b0, b1, b2, b3] = value.to_le_bytes();
+        self.put1(b0);
+        self.put1(b1);
+        self.put1(b2);
+        self.put1(b3);
     }
 
     /// Add 8 bytes to the section.
     fn put8(&mut self, value: u64) {
-        self.put1((value & 0xff) as u8);
-        self.put1(((value >> 8) & 0xff) as u8);
-        self.put1(((value >> 16) & 0xff) as u8);
-        self.put1(((value >> 24) & 0xff) as u8);
-        self.put1(((value >> 32) & 0xff) as u8);
-        self.put1(((value >> 40) & 0xff) as u8);
-        self.put1(((value >> 48) & 0xff) as u8);
-        self.put1(((value >> 56) & 0xff) as u8);
+        let [b0, b1, b2, b3, b4, b5, b6, b7] = value.to_le_bytes();
+        self.put1(b0);
+        self.put1(b1);
+        self.put1(b2);
+        self.put1(b3);
+        self.put1(b4);
+        self.put1(b5);
+        self.put1(b6);
+        self.put1(b7);
     }
 
     /// Add a slice of bytes to the section.