Remove the need for #[cfg] in #[use_c_shim_if]

ci/run.sh

@@ -1,5 +1,6 @@
 set -ex
 
+export CARGO_INCREMENTAL=0
 cargo=cargo
 
 # Test our implementation

src/float/conv.rs

@@ -87,11 +87,7 @@ intrinsics! {
         int_to_float!(i, i32, f64)
     }
 
-    #[use_c_shim_if(any(
-        all(target_arch = "x86", not(target_env = "msvc")),
-        all(target_arch = "x86_64", not(windows)),
-        all(target_arch = "x86_64", target_env = "msvc"),
-    ))]
+    #[maybe_use_optimized_c_shim]
     #[arm_aeabi_alias = __aeabi_l2f]
     pub extern "C" fn __floatdisf(i: i64) -> f32 {
         // On x86_64 LLVM will use native instructions for this conversion, we
@@ -103,7 +99,7 @@ intrinsics! {
         }
     }
 
-    #[use_c_shim_if(all(target_arch = "x86", not(target_env = "msvc")))]
+    #[maybe_use_optimized_c_shim]
     #[arm_aeabi_alias = __aeabi_l2d]
     pub extern "C" fn __floatdidf(i: i64) -> f64 {
         // On x86_64 LLVM will use native instructions for this conversion, we
@@ -135,19 +131,13 @@ intrinsics! {
         int_to_float!(i, u32, f64)
     }
 
-    #[use_c_shim_if(any(
-        all(target_arch = "x86", not(target_env = "msvc")),
-        all(target_arch = "x86_64", not(windows)),
-    ))]
+    #[maybe_use_optimized_c_shim]
     #[arm_aeabi_alias = __aeabi_ul2f]
     pub extern "C" fn __floatundisf(i: u64) -> f32 {
         int_to_float!(i, u64, f32)
     }
 
-    #[use_c_shim_if(any(
-        all(target_arch = "x86", not(target_env = "msvc")),
-        all(target_arch = "x86_64", not(windows)),
-    ))]
+    #[maybe_use_optimized_c_shim]
     #[arm_aeabi_alias = __aeabi_ul2d]
     pub extern "C" fn __floatundidf(i: u64) -> f64 {
         int_to_float!(i, u64, f64)

src/int/mod.rs

@@ -302,7 +302,7 @@ impl_wide_int!(u32, u64, 32);
 impl_wide_int!(u64, u128, 64);
 
 intrinsics! {
-    #[use_c_shim_if(/* always if C compilation is enabled */)]
+    #[maybe_use_optimized_c_shim]
     #[cfg(any(
         target_pointer_width = "16",
         target_pointer_width = "32",

src/int/mul.rs

@@ -84,7 +84,7 @@ trait UMulo: Int {
 impl UMulo for u128 {}
 
 intrinsics! {
-    #[use_c_shim_if(all(target_arch = "x86", not(target_env = "msvc")))]
+    #[maybe_use_optimized_c_shim]
     #[arm_aeabi_alias = __aeabi_lmul]
     pub extern "C" fn __muldi3(a: u64, b: u64) -> u64 {
         a.mul(b)

src/int/sdiv.rs

@@ -58,13 +58,13 @@ impl Divmod for i32 {}
 impl Divmod for i64 {}
 
 intrinsics! {
-    #[use_c_shim_if(all(target_arch = "arm", not(target_os = "ios"), not(thumb_1)))]
+    #[maybe_use_optimized_c_shim]
     #[arm_aeabi_alias = __aeabi_idiv]
     pub extern "C" fn __divsi3(a: i32, b: i32) -> i32 {
         a.div(b)
     }
 
-    #[use_c_shim_if(all(target_arch = "x86", not(target_env = "msvc")))]
+    #[maybe_use_optimized_c_shim]
     pub extern "C" fn __divdi3(a: i64, b: i64) -> i64 {
         a.div(b)
     }
@@ -74,15 +74,12 @@ intrinsics! {
         a.div(b)
     }
 
-    #[use_c_shim_if(all(target_arch = "arm",
-                    not(target_os = "ios"),
-                    not(target_env = "msvc"),
-                    not(thumb_1)))]
+    #[maybe_use_optimized_c_shim]
     pub extern "C" fn __modsi3(a: i32, b: i32) -> i32 {
         a.mod_(b)
     }
 
-    #[use_c_shim_if(all(target_arch = "x86", not(target_env = "msvc")))]
+    #[maybe_use_optimized_c_shim]
     pub extern "C" fn __moddi3(a: i64, b: i64) -> i64 {
         a.mod_(b)
     }
@@ -92,8 +89,7 @@ intrinsics! {
         a.mod_(b)
     }
 
-    #[use_c_shim_if(all(target_arch = "arm", not(target_env = "msvc"),
-                    not(target_os = "ios"), not(thumb_1)))]
+    #[maybe_use_optimized_c_shim]
     pub extern "C" fn __divmodsi4(a: i32, b: i32, rem: &mut i32) -> i32 {
         a.divmod(b, rem, |a, b| __divsi3(a, b))
     }

src/int/shift.rs

@@ -74,7 +74,7 @@ impl Lshr for u64 {}
 impl Lshr for u128 {}
 
 intrinsics! {
-    #[use_c_shim_if(all(target_arch = "x86", not(target_env = "msvc")))]
+    #[maybe_use_optimized_c_shim]
     #[arm_aeabi_alias = __aeabi_llsl]
     pub extern "C" fn __ashldi3(a: u64, b: u32) -> u64 {
         a.ashl(b)
@@ -84,7 +84,7 @@ intrinsics! {
         a.ashl(b)
     }
 
-    #[use_c_shim_if(all(target_arch = "x86", not(target_env = "msvc")))]
+    #[maybe_use_optimized_c_shim]
     #[arm_aeabi_alias = __aeabi_lasr]
     pub extern "C" fn __ashrdi3(a: i64, b: u32) -> i64 {
         a.ashr(b)
@@ -94,7 +94,7 @@ intrinsics! {
         a.ashr(b)
     }
 
-    #[use_c_shim_if(all(target_arch = "x86", not(target_env = "msvc")))]
+    #[maybe_use_optimized_c_shim]
     #[arm_aeabi_alias = __aeabi_llsr]
     pub extern "C" fn __lshrdi3(a: u64, b: u32) -> u64 {
         a.lshr(b)

src/int/udiv.rs

@@ -152,9 +152,7 @@ macro_rules! udivmod_inner {
 }
 
 intrinsics! {
-    #[use_c_shim_if(all(target_arch = "arm",
-                        not(target_os = "ios"),
-                        not(thumb_1)))]
+    #[maybe_use_optimized_c_shim]
     #[arm_aeabi_alias = __aeabi_uidiv]
     /// Returns `n / d`
     pub extern "C" fn __udivsi3(n: u32, d: u32) -> u32 {
@@ -212,20 +210,14 @@ intrinsics! {
         (q << 1) | carry
     }
 
-    #[use_c_shim_if(all(target_arch = "arm",
-                        not(target_os = "ios"),
-                        not(target_env = "msvc"),
-                        not(thumb_1)))]
+    #[maybe_use_optimized_c_shim]
     /// Returns `n % d`
     pub extern "C" fn __umodsi3(n: u32, d: u32) -> u32 {
         let q = __udivsi3(n, d);
         n - q * d
     }
 
-    #[use_c_shim_if(all(target_arch = "arm",
-                        not(target_os = "ios"),
-                        not(target_env = "msvc"),
-                        not(thumb_1)))]
+    #[maybe_use_optimized_c_shim]
     /// Returns `n / d` and sets `*rem = n % d`
     pub extern "C" fn __udivmodsi4(n: u32, d: u32, rem: Option<&mut u32>) -> u32 {
         let q = __udivsi3(n, d);
@@ -235,13 +227,13 @@ intrinsics! {
         q
     }
 
-    #[use_c_shim_if(all(target_arch = "x86", not(target_env = "msvc")))]
+    #[maybe_use_optimized_c_shim]
     /// Returns `n / d`
     pub extern "C" fn __udivdi3(n: u64, d: u64) -> u64 {
         __udivmoddi4(n, d, None)
     }
 
-    #[use_c_shim_if(all(target_arch = "x86", not(target_env = "msvc")))]
+    #[maybe_use_optimized_c_shim]
     /// Returns `n % d`
     pub extern "C" fn __umoddi3(n: u64, d: u64) -> u64 {
         let mut rem = 0;

src/macros.rs

@@ -30,8 +30,8 @@
 ///
 /// A quick overview of attributes supported right now are:
 ///
-/// * `use_c_shim_if` - takes a #[cfg] directive and falls back to the
-///   C-compiled version if `use_c` is specified.
+/// * `maybe_use_optimized_c_shim` - indicates that the Rust implementation is
+///   ignored if an optimized C version was compiled.
 /// * `aapcs_on_arm` - forces the ABI of the function to be `"aapcs"` on ARM and
 ///   the specified ABI everywhere else.
 /// * `unadjusted_on_win64` - like `aapcs_on_arm` this switches to the
@@ -51,15 +51,14 @@ macro_rules! intrinsics {
     // to the architecture-specific versions which should be more optimized. The
     // purpose of this macro is to easily allow specifying this.
     //
-    // The argument to `use_c_shim_if` is a `#[cfg]` directive which, when true,
-    // will cause this crate's exported version of `$name` to just redirect to
-    // the C implementation. No symbol named `$name` will be in the object file
-    // for this crate itself.
-    //
-    // When the `#[cfg]` directive is false, or when the `c` feature is
-    // disabled, the provided implementation is used instead.
+    // The `#[maybe_use_optimized_c_shim]` attribute indicates that this
+    // intrinsic may have an optimized C version. In these situations the build
+    // script, if the C code is enabled and compiled, will emit a cfg directive
+    // to get passed to rustc for our compilation. If that cfg is set we skip
+    // the Rust implementation, but if the attribute is not enabled then we
+    // compile in the Rust implementation.
     (
-        #[use_c_shim_if($($cfg_clause:tt)*)]
+        #[maybe_use_optimized_c_shim]
         $(#[$($attr:tt)*])*
         pub extern $abi:tt fn $name:ident( $($argname:ident:  $ty:ty),* ) -> $ret:ty {
             $($body:tt)*
@@ -68,7 +67,7 @@ macro_rules! intrinsics {
         $($rest:tt)*
     ) => (
 
-        #[cfg(all(use_c, $($cfg_clause)*))]
+        #[cfg($name = "optimized-c")]
         pub extern $abi fn $name( $($argname: $ty),* ) -> $ret {
             extern $abi {
                 fn $name($($argname: $ty),*) -> $ret;
@@ -78,7 +77,7 @@ macro_rules! intrinsics {
             }
         }
 
-        #[cfg(not(all(use_c, $($cfg_clause)*)))]
+        #[cfg(not($name = "optimized-c"))]
         intrinsics! {
             $(#[$($attr)*])*
             pub extern $abi fn $name( $($argname: $ty),* ) -> $ret {