Improve cfg names for fast arithmetic

Author: dtolnay

build.rs

@@ -3,8 +3,7 @@ use std::env;
 fn main() {
     println!("cargo:rerun-if-changed=build.rs");
 
-    println!("cargo:rustc-check-cfg=cfg(arithmetic32)");
-    println!("cargo:rustc-check-cfg=cfg(arithmetic64)");
+    println!("cargo:rustc-check-cfg=cfg(fast_arithmetic, values(\"32\", \"64\"))");
 
     // Decide ideal limb width for arithmetic in the float parser and string
     // parser.
@@ -23,8 +22,8 @@ fn main() {
         // pointer width. Examples include aarch64-unknown-linux-gnu_ilp32 and
         // x86_64-unknown-linux-gnux32. So our choice of limb width is not
         // equivalent to using usize everywhere.
-        println!("cargo:rustc-cfg=arithmetic64");
+        println!("cargo:rustc-cfg=fast_arithmetic=\"64\"");
     } else {
-        println!("cargo:rustc-cfg=arithmetic32");
+        println!("cargo:rustc-cfg=fast_arithmetic=\"32\"");
     }
 }

src/lexical/large_powers.rs

@@ -2,8 +2,8 @@
 
 //! Precalculated large powers for limbs.
 
-#[cfg(arithmetic32)]
+#[cfg(fast_arithmetic = "32")]
 pub(crate) use super::large_powers32::*;
 
-#[cfg(arithmetic64)]
+#[cfg(fast_arithmetic = "64")]
 pub(crate) use super::large_powers64::*;

src/lexical/math.rs

@@ -37,29 +37,29 @@ use core::{cmp, iter, mem};
 //      sparc64 (`UMUL` only supported double-word arguments).
 
 // 32-BIT LIMB
-#[cfg(arithmetic32)]
+#[cfg(fast_arithmetic = "32")]
 pub type Limb = u32;
 
-#[cfg(arithmetic32)]
+#[cfg(fast_arithmetic = "32")]
 pub const POW5_LIMB: &[Limb] = &POW5_32;
 
-#[cfg(arithmetic32)]
+#[cfg(fast_arithmetic = "32")]
 pub const POW10_LIMB: &[Limb] = &POW10_32;
 
-#[cfg(arithmetic32)]
+#[cfg(fast_arithmetic = "32")]
 type Wide = u64;
 
 // 64-BIT LIMB
-#[cfg(arithmetic64)]
+#[cfg(fast_arithmetic = "64")]
 pub type Limb = u64;
 
-#[cfg(arithmetic64)]
+#[cfg(fast_arithmetic = "64")]
 pub const POW5_LIMB: &[Limb] = &POW5_64;
 
-#[cfg(arithmetic64)]
+#[cfg(fast_arithmetic = "64")]
 pub const POW10_LIMB: &[Limb] = &POW10_64;
 
-#[cfg(arithmetic64)]
+#[cfg(fast_arithmetic = "64")]
 type Wide = u128;
 
 /// Cast to limb type.
@@ -79,14 +79,14 @@ fn as_wide<T: Integer>(t: T) -> Wide {
 
 /// Split u64 into limbs, in little-endian order.
 #[inline]
-#[cfg(arithmetic32)]
+#[cfg(fast_arithmetic = "32")]
 fn split_u64(x: u64) -> [Limb; 2] {
     [as_limb(x), as_limb(x >> 32)]
 }
 
 /// Split u64 into limbs, in little-endian order.
 #[inline]
-#[cfg(arithmetic64)]
+#[cfg(fast_arithmetic = "64")]
 fn split_u64(x: u64) -> [Limb; 1] {
     [as_limb(x)]
 }

src/lexical/mod.rs

@@ -28,10 +28,10 @@ pub(crate) mod rounding;
 mod shift;
 mod small_powers;
 
-#[cfg(arithmetic32)]
+#[cfg(fast_arithmetic = "32")]
 mod large_powers32;
 
-#[cfg(arithmetic64)]
+#[cfg(fast_arithmetic = "64")]
 mod large_powers64;
 
 // API

src/lexical/small_powers.rs

@@ -3,19 +3,19 @@
 //! Pre-computed small powers.
 
 // 32 BIT
-#[cfg(arithmetic32)]
+#[cfg(fast_arithmetic = "32")]
 pub(crate) const POW5_32: [u32; 14] = [
     1, 5, 25, 125, 625, 3125, 15625, 78125, 390625, 1953125, 9765625, 48828125, 244140625,
     1220703125,
 ];
 
-#[cfg(arithmetic32)]
+#[cfg(fast_arithmetic = "32")]
 pub(crate) const POW10_32: [u32; 10] = [
     1, 10, 100, 1000, 10000, 100000, 1000000, 10000000, 100000000, 1000000000,
 ];
 
 // 64 BIT
-#[cfg(arithmetic64)]
+#[cfg(fast_arithmetic = "64")]
 pub(crate) const POW5_64: [u64; 28] = [
     1,
     5,

src/read.rs

@@ -446,9 +446,9 @@ impl<'a> SliceRead<'a> {
         // benchmarks and it's cross-platform, so probably the right fit.
         // [1]: https://groups.google.com/forum/#!original/comp.lang.c/2HtQXvg7iKc/xOJeipH6KLMJ
 
-        #[cfg(arithmetic64)]
+        #[cfg(fast_arithmetic = "64")]
         type Chunk = u64;
-        #[cfg(arithmetic32)]
+        #[cfg(fast_arithmetic = "32")]
         type Chunk = u32;
 
         const STEP: usize = mem::size_of::<Chunk>();

tests/lexical/math.rs

@@ -18,12 +18,12 @@ impl Math for Bigint {
     }
 }
 
-#[cfg(arithmetic32)]
+#[cfg(fast_arithmetic = "32")]
 pub(crate) fn from_u32(x: &[u32]) -> Vec<Limb> {
     x.iter().cloned().collect()
 }
 
-#[cfg(arithmetic64)]
+#[cfg(fast_arithmetic = "64")]
 pub(crate) fn from_u32(x: &[u32]) -> Vec<Limb> {
     let mut v = Vec::<Limb>::default();
     for xi in x.chunks(2) {