Stub of a new isel backend for x64

cranelift/codegen/Cargo.toml

@@ -58,10 +58,12 @@ x86 = []
 arm32 = []
 arm64 = []
 riscv = []
+x64 = [] # New work-in-progress codegen backend for x86_64 based on the new isel.
 
 # Option to enable all architectures.
 all-arch = [
     "x86",
+    "x64",
     "arm32",
     "arm64",
     "riscv"

cranelift/codegen/meta/src/isa/x86/settings.rs

@@ -3,6 +3,12 @@ use crate::cdsl::settings::{PredicateNode, SettingGroup, SettingGroupBuilder};
 pub(crate) fn define(shared: &SettingGroup) -> SettingGroup {
     let mut settings = SettingGroupBuilder::new("x86");
 
+    settings.add_bool(
+        "use_new_backend",
+        "Whether to use the new codegen backend using the new isel",
+        false,
+    );
+
     // CPUID.01H:ECX
     let has_sse3 = settings.add_bool("has_sse3", "SSE3: CPUID.01H:ECX.SSE3[bit 0]", false);
     let has_ssse3 = settings.add_bool("has_ssse3", "SSSE3: CPUID.01H:ECX.SSSE3[bit 9]", false);

cranelift/codegen/src/isa/mod.rs

@@ -77,6 +77,9 @@ mod riscv;
 #[cfg(feature = "x86")]
 mod x86;
 
+#[cfg(feature = "x64")]
+mod x64;
+
 #[cfg(feature = "arm32")]
 mod arm32;