Move the builtins for in-tree use to a separate crate

Author: tgross35

Cargo.toml

@@ -10,7 +10,7 @@ members = [
     "crates/symbol-check",
     "crates/util",
     "libm",
-    "libm-test",
+    "libm-test"
 ]
 
 default-members = [
@@ -26,6 +26,7 @@ exclude = [
     # and `mangled-names` disabled, which is the opposite of what is needed for
     # other tests, so it makes sense to keep it out of the workspace.
     "builtins-test-intrinsics",
+    "rustc-std-workspace-compiler-builtins",
 ]
 
 [profile.release]

compiler-builtins/Cargo.toml

@@ -16,9 +16,6 @@ bench = false
 doctest = false
 test = false
 
-[dependencies]
-core = { path = "../../core", optional = true }
-
 [build-dependencies]
 cc = { optional = true, version = "1.2" }
 
@@ -48,7 +45,7 @@ mem = []
 mangled-names = []
 
 # Only used in the compiler's build system
-rustc-dep-of-std = ["compiler-builtins", "dep:core"]
+rustc-dep-of-std = ["compiler-builtins"]
 
 # This makes certain traits and function specializations public that
 # are not normally public but are required by the `builtins-test`

rustc-std-workspace-compiler-builtins/Cargo.toml

@@ -0,0 +1,56 @@
+[package]
+name = "compiler_builtins"
+version = "0.1.160"
+license = "MIT AND Apache-2.0 WITH LLVM-exception AND (MIT OR Apache-2.0)"
+edition = "2024"
+publish = false
+links = "compiler-rt"
+include = ["../compiler-builtins/src"]
+build = "../compiler-builtins/build.rs"
+
+[lib]
+bench = false
+doctest = false
+test = false
+
+[dependencies]
+core = { path = "../../core", optional = true }
+
+[build-dependencies]
+cc = { optional = true, version = "1.2" }
+
+[features]
+default = ["compiler-builtins"]
+
+# Enable compilation of C code in compiler-rt, filling in some more optimized
+# implementations and also filling in unimplemented intrinsics
+c = ["dep:cc"]
+
+# Workaround for the Cranelift codegen backend. Disables any implementations
+# which use inline assembly and fall back to pure Rust versions (if available).
+no-asm = []
+
+# Workaround for codegen backends which haven't yet implemented `f16` and
+# `f128` support. Disabled any intrinsics which use those types.
+no-f16-f128 = []
+
+# Flag this library as the unstable compiler-builtins lib
+compiler-builtins = []
+
+# Generate memory-related intrinsics like memcpy
+mem = []
+
+# Mangle all names so this can be linked in with other versions or other
+# compiler-rt implementations. Also used for testing
+mangled-names = []
+
+# Only used in the compiler's build system
+rustc-dep-of-std = ["compiler-builtins"]
+
+# This makes certain traits and function specializations public that
+# are not normally public but are required by the `builtins-test`
+unstable-public-internals = []
+
+[lints.rust]
+# The cygwin config can be dropped after our benchmark toolchain is bumped
+unexpected_cfgs = { level = "warn", check-cfg = ['cfg(bootstrap)', 'cfg(target_os, values("cygwin"))'] }

rustc-std-workspace-compiler-builtins/src/lib.rs

@@ -0,0 +1,14 @@
+pub fn add(left: u64, right: u64) -> u64 {
+    left + right
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn it_works() {
+        let result = add(2, 2);
+        assert_eq!(result, 4);
+    }
+}