Use stable Rust on CI to test the x64 backend (#2766)

* Use stable Rust on CI to test the x64 backend

This commit leverages the newly-released 1.51.0 compiler to test the
new backend on Windows and Linux with a stable compiler instead of a
nightly compiler. This isolates the nightly build to just the nightly
documentation generation and fuzzing, both of which rely on nightly for
the best results right now.

* Use updated stable in book build job

* Run rustfmt for new stable

* Silence new warnings for wasi-nn

* Allow some dead code in the x64 backend

Looks like new rustc is better about emitting some dead-code warnings

* Update rust in peepmatic job

* Fix a test in the pooling allocator

* Remove `package.metdata.docs.rs` temporarily

Needs resolution of https://github.com/rust-lang/cargo/pull/9300 first

* Fix a warning in a wasi-nn example

cranelift/codegen/meta/Cargo.toml

@@ -8,8 +8,9 @@ repository = "https://github.com/bytecodealliance/wasmtime"
 readme = "README.md"
 edition = "2018"
 
-[package.metadata.docs.rs]
-rustdoc-args = [ "--document-private-items" ]
+# FIXME(rust-lang/cargo#9300): uncomment once that lands
+# [package.metadata.docs.rs]
+# rustdoc-args = [ "--document-private-items" ]
 
 [dependencies]
 cranelift-codegen-shared = { path = "../shared", version = "0.72.0" }

cranelift/codegen/src/isa/x64/inst/args.rs

@@ -462,6 +462,7 @@ pub(crate) enum InstructionSet {
 
 /// Some SSE operations requiring 2 operands r/m and r.
 #[derive(Clone, Copy, PartialEq)]
+#[allow(dead_code)] // some variants here aren't used just yet
 pub enum SseOpcode {
     Addps,
     Addpd,

cranelift/codegen/src/isa/x64/lower.rs

@@ -204,6 +204,7 @@ enum ExtSpec {
     ZeroExtendTo32,
     ZeroExtendTo64,
     SignExtendTo32,
+    #[allow(dead_code)] // not used just yet but may be used in the future!
     SignExtendTo64,
 }
 

cranelift/peepmatic/crates/automata/Cargo.toml

@@ -6,8 +6,9 @@ edition = "2018"
 license = "Apache-2.0 WITH LLVM-exception"
 description = "Finite-state transducer automata"
 
-[package.metadata.docs.rs]
-all-features = true
+# FIXME(rust-lang/cargo#9300): uncomment once that lands
+# [package.metadata.docs.rs]
+# all-features = true
 
 [dependencies]
 serde = { version = "1.0.106", optional = true }