c-b: Clean up the mem feature

`mem` only enables the unmangled names; the functions are always
available via mangled names, so this doesn't have any purpose in our
tests. Thus, remove it from `builtins-test`.

The remaining `feature = "mem"` configuration in tests is for the
`aeabi_mem*` files, which call the compiler-builtins functions via
extern definitions. Move these to builtins-test-intrinsics, which is the
home of other tests that require unmangled symbols. Unfortunately these
tests have apparently not worked for a long time; this situation is
unchanged.

library/compiler-builtins/Cargo.lock

@@ -155,9 +155,6 @@ dependencies = [
  "paste",
  "rand_xoshiro",
  "rustc_apfloat",
- "test",
- "utest-cortex-m-qemu",
- "utest-macros",
 ]
 
 [[package]]
@@ -1084,12 +1081,6 @@ dependencies = [
  "winapi-util",
 ]
 
-[[package]]
-name = "sc"
-version = "0.2.7"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "010e18bd3bfd1d45a7e666b236c78720df0d9a7698ebaa9c1c559961eb60a38b"
-
 [[package]]
 name = "semver"
 version = "1.0.27"
@@ -1206,11 +1197,6 @@ version = "0.5.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "8f50febec83f5ee1df3015341d8bd429f2d1cc62bcba7ea2076759d315084683"
 
-[[package]]
-name = "test"
-version = "0.1.0"
-source = "git+https://github.com/japaric/utest#e32073e2b078e3bee46001c13ae4c1acf368d762"
-
 [[package]]
 name = "tinytemplate"
 version = "1.2.1"
@@ -1251,19 +1237,6 @@ version = "0.5.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "81e544489bf3d8ef66c953931f56617f423cd4b5494be343d9b9d3dda037b9a3"
 
-[[package]]
-name = "utest-cortex-m-qemu"
-version = "0.1.0"
-source = "git+https://github.com/japaric/utest#e32073e2b078e3bee46001c13ae4c1acf368d762"
-dependencies = [
- "sc",
-]
-
-[[package]]
-name = "utest-macros"
-version = "0.1.0"
-source = "git+https://github.com/japaric/utest#e32073e2b078e3bee46001c13ae4c1acf368d762"
-
 [[package]]
 name = "utf8parse"
 version = "0.2.2"

library/compiler-builtins/builtins-shim/Cargo.toml

@@ -54,7 +54,8 @@ no-asm = []
 # when using as `std`'s dependency.'
 compiler-builtins = ["unmangled-names"]
 
-# Generate memory-related intrinsics like memcpy
+# Enable `no_mangle` symbols for memory-related intrinsics like memcpy. The
+# mangled versions are always available.
 mem = []
 
 # Enable `no_mangle` symbols so this crate gets used as the runtime intrinsic

library/compiler-builtins/builtins-test-intrinsics/Cargo.toml

@@ -6,9 +6,15 @@ publish = false
 license = "MIT OR Apache-2.0"
 
 [dependencies]
+# FIXME: `aeabi_mem*` tests will require the "mem" feature to be enabled here.
 compiler_builtins = { path = "../builtins-shim", features = ["compiler-builtins", "unmangled-names"] }
 panic-handler = { path = "../crates/panic-handler" }
 
+[target.'cfg(all(target_arch = "arm", not(any(target_env = "gnu", target_env = "musl")), target_os = "linux"))'.dev-dependencies]
+test = { git = "https://github.com/japaric/utest" }
+utest-cortex-m-qemu = { default-features = false, git = "https://github.com/japaric/utest" }
+utest-macros = { git = "https://github.com/japaric/utest" }
+
 [features]
 c = ["compiler_builtins/c"]
 

library/compiler-builtins/builtins-test-intrinsics/src/main.rs

@@ -1,7 +1,9 @@
-// By compiling this file we check that all the intrinsics we care about continue to be provided by
-// the `compiler_builtins` crate regardless of the changes we make to it. If we, by mistake, stop
-// compiling a C implementation and forget to implement that intrinsic in Rust, this file will fail
-// to link due to the missing intrinsic (symbol).
+//! Tests that require unmangled symbols from `compiler-builtins`.
+//!
+//! By compiling this file we check that all the intrinsics we care about continue to be provided by
+//! the `compiler_builtins` crate regardless of the changes we make to it. If we, by mistake, stop
+//! compiling a C implementation and forget to implement that intrinsic in Rust, this file will fail
+//! to link due to the missing intrinsic (symbol).
 
 #![allow(internal_features, unused_features)]
 #![deny(dead_code)]

library/compiler-builtins/builtins-test-intrinsics/tests/aeabi_memclr.rs

@@ -2,7 +2,6 @@
     target_arch = "arm",
     not(any(target_env = "gnu", target_env = "musl")),
     target_os = "linux",
-    feature = "mem"
 ))]
 #![feature(compiler_builtins_lib)]
 #![no_std]

library/compiler-builtins/builtins-test-intrinsics/tests/aeabi_memcpy.rs

@@ -2,7 +2,6 @@
     target_arch = "arm",
     not(any(target_env = "gnu", target_env = "musl")),
     target_os = "linux",
-    feature = "mem"
 ))]
 #![feature(compiler_builtins_lib)]
 #![no_std]

library/compiler-builtins/builtins-test-intrinsics/tests/aeabi_memset.rs

@@ -2,7 +2,6 @@
     target_arch = "arm",
     not(any(target_env = "gnu", target_env = "musl")),
     target_os = "linux",
-    feature = "mem"
 ))]
 #![feature(compiler_builtins_lib)]
 #![no_std]

library/compiler-builtins/builtins-test/Cargo.toml

@@ -23,16 +23,10 @@ gungraun = { workspace = true, optional = true }
 [dev-dependencies]
 paste.workspace = true
 
-[target.'cfg(all(target_arch = "arm", not(any(target_env = "gnu", target_env = "musl")), target_os = "linux"))'.dev-dependencies]
-test = { git = "https://github.com/japaric/utest" }
-utest-cortex-m-qemu = { default-features = false, git = "https://github.com/japaric/utest" }
-utest-macros = { git = "https://github.com/japaric/utest" }
-
 [features]
 default = []
 c = ["compiler_builtins/c"]
 no-asm = ["compiler_builtins/no-asm"]
-mem = ["compiler_builtins/mem"]
 # Skip tests that rely on f128 symbols being available on the system
 no-sys-f128 = ["no-sys-f128-int-convert", "no-sys-f16-f128-convert"]
 # Some platforms have some f128 functions but everything except integer conversions

library/compiler-builtins/compiler-builtins/Cargo.toml

@@ -49,8 +49,8 @@ no-asm = []
 # when using as `std`'s dependency.'
 compiler-builtins = ["dep:core", "unmangled-names"]
 
-# Generate memory-related intrinsics like memcpy
-mem = []
+# Enable `no_mangle` symbols for memory-related intrinsics like memcpy. The
+# mangled versions are always available.
 
 # Enable `no_mangle` symbols so this crate gets used as the runtime intrinsic
 # implementation. Leave this disabled for testing to avoid conflicting with

library/compiler-builtins/compiler-builtins/src/macros.rs

@@ -392,7 +392,7 @@ extern "aapcs" fn $alias( $($argname: $ty),* ) $(-> $ret)? {
         intrinsics!($($rest)*);
     );
 
-    // C mem* functions are only generated when the "mem" feature is enabled.
+    // C mem* functions are only exposed via `no_mangle` when the "mem" feature is enabled.
     (
         #[mem_builtin]
         $(#[$($attr:tt)*])*