Auto merge of #43367 - alexcrichton:remove-inline-always, r=sfackler

std: Cut down #[inline] annotations where not necessary

This PR cuts down on a large number of `#[inline(always)]` and `#[inline]`
annotations in libcore for various core functions. The `#[inline(always)]`
annotation is almost never needed and is detrimental to debug build times as it
forces LLVM to perform inlining when it otherwise wouldn't need to in debug
builds. Additionally `#[inline]` is an unnecessary annoation on almost all
generic functions because the function will already be monomorphized into other
codegen units and otherwise rarely needs the extra "help" from us to tell LLVM
to inline something.

Overall this PR cut the compile time of a [microbenchmark][1] by 30% from 1s to
0.7s.

[1]: https://gist.github.com/alexcrichton/a7d70319a45aa60cf36a6a7bf540dd3a

src/libcore/clone.rs

@@ -106,7 +106,7 @@ pub trait Clone : Sized {
     /// `a.clone_from(&b)` is equivalent to `a = b.clone()` in functionality,
     /// but can be overridden to reuse the resources of `a` to avoid unnecessary
     /// allocations.
-    #[inline(always)]
+    #[inline]
     #[stable(feature = "rust1", since = "1.0.0")]
     fn clone_from(&mut self, source: &Self) {
         *self = source.clone()

src/libcore/cmp.rs

@@ -168,7 +168,7 @@ pub trait Eq: PartialEq<Self> {
     //
     // This should never be implemented by hand.
     #[doc(hidden)]
-    #[inline(always)]
+    #[inline]
     #[stable(feature = "rust1", since = "1.0.0")]
     fn assert_receiver_is_total_eq(&self) {}
 }

src/libcore/hash/sip.rs

@@ -239,7 +239,7 @@ impl<S: Sip> Hasher<S> {
     // except for composite types (that includes slices and str hashing because of delimiter).
     // Without this extra push the compiler is very reluctant to inline delimiter writes,
     // degrading performance substantially for the most common use cases.
-    #[inline(always)]
+    #[inline]
     fn short_write(&mut self, msg: &[u8]) {
         debug_assert!(msg.len() <= 8);
         let length = msg.len();

src/libcore/nonzero.rs

@@ -42,7 +42,7 @@ pub struct NonZero<T: Zeroable>(T);
 impl<T: Zeroable> NonZero<T> {
     /// Creates an instance of NonZero with the provided value.
     /// You must indeed ensure that the value is actually "non-zero".
-    #[inline(always)]
+    #[inline]
     pub const unsafe fn new(inner: T) -> NonZero<T> {
         NonZero(inner)
     }

src/libcore/num/mod.rs

@@ -695,7 +695,7 @@ macro_rules! int_impl {
         /// assert_eq!((-128i8).wrapping_div(-1), -128);
         /// ```
         #[stable(feature = "num_wrapping", since = "1.2.0")]
-        #[inline(always)]
+        #[inline]
         pub fn wrapping_div(self, rhs: Self) -> Self {
             self.overflowing_div(rhs).0
         }
@@ -721,7 +721,7 @@ macro_rules! int_impl {
         /// assert_eq!((-128i8).wrapping_rem(-1), 0);
         /// ```
         #[stable(feature = "num_wrapping", since = "1.2.0")]
-        #[inline(always)]
+        #[inline]
         pub fn wrapping_rem(self, rhs: Self) -> Self {
             self.overflowing_rem(rhs).0
         }
@@ -744,7 +744,7 @@ macro_rules! int_impl {
         /// assert_eq!((-128i8).wrapping_neg(), -128);
         /// ```
         #[stable(feature = "num_wrapping", since = "1.2.0")]
-        #[inline(always)]
+        #[inline]
         pub fn wrapping_neg(self) -> Self {
             self.overflowing_neg().0
         }
@@ -769,7 +769,7 @@ macro_rules! int_impl {
         /// assert_eq!((-1i8).wrapping_shl(8), -1);
         /// ```
         #[stable(feature = "num_wrapping", since = "1.2.0")]
-        #[inline(always)]
+        #[inline]
         pub fn wrapping_shl(self, rhs: u32) -> Self {
             unsafe {
                 intrinsics::unchecked_shl(self, (rhs & ($BITS - 1)) as $SelfT)
@@ -796,7 +796,7 @@ macro_rules! int_impl {
         /// assert_eq!((-128i8).wrapping_shr(8), -128);
         /// ```
         #[stable(feature = "num_wrapping", since = "1.2.0")]
-        #[inline(always)]
+        #[inline]
         pub fn wrapping_shr(self, rhs: u32) -> Self {
             unsafe {
                 intrinsics::unchecked_shr(self, (rhs & ($BITS - 1)) as $SelfT)
@@ -822,7 +822,7 @@ macro_rules! int_impl {
         /// assert_eq!((-128i8).wrapping_abs() as u8, 128);
         /// ```
         #[stable(feature = "no_panic_abs", since = "1.13.0")]
-        #[inline(always)]
+        #[inline]
         pub fn wrapping_abs(self) -> Self {
             if self.is_negative() {
                 self.wrapping_neg()
@@ -1831,7 +1831,7 @@ macro_rules! uint_impl {
         /// assert_eq!(100u8.wrapping_div(10), 10);
         /// ```
         #[stable(feature = "num_wrapping", since = "1.2.0")]
-        #[inline(always)]
+        #[inline]
         pub fn wrapping_div(self, rhs: Self) -> Self {
             self / rhs
         }
@@ -1851,7 +1851,7 @@ macro_rules! uint_impl {
         /// assert_eq!(100u8.wrapping_rem(10), 0);
         /// ```
         #[stable(feature = "num_wrapping", since = "1.2.0")]
-        #[inline(always)]
+        #[inline]
         pub fn wrapping_rem(self, rhs: Self) -> Self {
             self % rhs
         }
@@ -1877,7 +1877,7 @@ macro_rules! uint_impl {
         /// assert_eq!(180u8.wrapping_neg(), (127 + 1) - (180u8 - (127 + 1)));
         /// ```
         #[stable(feature = "num_wrapping", since = "1.2.0")]
-        #[inline(always)]
+        #[inline]
         pub fn wrapping_neg(self) -> Self {
             self.overflowing_neg().0
         }
@@ -1902,7 +1902,7 @@ macro_rules! uint_impl {
         /// assert_eq!(1u8.wrapping_shl(8), 1);
         /// ```
         #[stable(feature = "num_wrapping", since = "1.2.0")]
-        #[inline(always)]
+        #[inline]
         pub fn wrapping_shl(self, rhs: u32) -> Self {
             unsafe {
                 intrinsics::unchecked_shl(self, (rhs & ($BITS - 1)) as $SelfT)
@@ -1929,7 +1929,7 @@ macro_rules! uint_impl {
         /// assert_eq!(128u8.wrapping_shr(8), 128);
         /// ```
         #[stable(feature = "num_wrapping", since = "1.2.0")]
-        #[inline(always)]
+        #[inline]
         pub fn wrapping_shr(self, rhs: u32) -> Self {
             unsafe {
                 intrinsics::unchecked_shr(self, (rhs & ($BITS - 1)) as $SelfT)

src/libcore/num/wrapping.rs

@@ -19,7 +19,7 @@ macro_rules! sh_impl_signed {
         impl Shl<$f> for Wrapping<$t> {
             type Output = Wrapping<$t>;
 
-            #[inline(always)]
+            #[inline]
             fn shl(self, other: $f) -> Wrapping<$t> {
                 if other < 0 {
                     Wrapping(self.0.wrapping_shr((-other & self::shift_max::$t as $f) as u32))
@@ -31,7 +31,7 @@ macro_rules! sh_impl_signed {
 
         #[stable(feature = "op_assign_traits", since = "1.8.0")]
         impl ShlAssign<$f> for Wrapping<$t> {
-            #[inline(always)]
+            #[inline]
             fn shl_assign(&mut self, other: $f) {
                 *self = *self << other;
             }
@@ -41,7 +41,7 @@ macro_rules! sh_impl_signed {
         impl Shr<$f> for Wrapping<$t> {
             type Output = Wrapping<$t>;
 
-            #[inline(always)]
+            #[inline]
             fn shr(self, other: $f) -> Wrapping<$t> {
                 if other < 0 {
                     Wrapping(self.0.wrapping_shl((-other & self::shift_max::$t as $f) as u32))
@@ -53,7 +53,7 @@ macro_rules! sh_impl_signed {
 
         #[stable(feature = "op_assign_traits", since = "1.8.0")]
         impl ShrAssign<$f> for Wrapping<$t> {
-            #[inline(always)]
+            #[inline]
             fn shr_assign(&mut self, other: $f) {
                 *self = *self >> other;
             }
@@ -67,15 +67,15 @@ macro_rules! sh_impl_unsigned {
         impl Shl<$f> for Wrapping<$t> {
             type Output = Wrapping<$t>;
 
-            #[inline(always)]
+            #[inline]
             fn shl(self, other: $f) -> Wrapping<$t> {
                 Wrapping(self.0.wrapping_shl((other & self::shift_max::$t as $f) as u32))
             }
         }
 
         #[stable(feature = "op_assign_traits", since = "1.8.0")]
         impl ShlAssign<$f> for Wrapping<$t> {
-            #[inline(always)]
+            #[inline]
             fn shl_assign(&mut self, other: $f) {
                 *self = *self << other;
             }
@@ -85,15 +85,15 @@ macro_rules! sh_impl_unsigned {
         impl Shr<$f> for Wrapping<$t> {
             type Output = Wrapping<$t>;
 
-            #[inline(always)]
+            #[inline]
             fn shr(self, other: $f) -> Wrapping<$t> {
                 Wrapping(self.0.wrapping_shr((other & self::shift_max::$t as $f) as u32))
             }
         }
 
         #[stable(feature = "op_assign_traits", since = "1.8.0")]
         impl ShrAssign<$f> for Wrapping<$t> {
-            #[inline(always)]
+            #[inline]
             fn shr_assign(&mut self, other: $f) {
                 *self = *self >> other;
             }
@@ -127,7 +127,7 @@ macro_rules! wrapping_impl {
         impl Add for Wrapping<$t> {
             type Output = Wrapping<$t>;
 
-            #[inline(always)]
+            #[inline]
             fn add(self, other: Wrapping<$t>) -> Wrapping<$t> {
                 Wrapping(self.0.wrapping_add(other.0))
             }
@@ -137,7 +137,7 @@ macro_rules! wrapping_impl {
 
         #[stable(feature = "op_assign_traits", since = "1.8.0")]
         impl AddAssign for Wrapping<$t> {
-            #[inline(always)]
+            #[inline]
             fn add_assign(&mut self, other: Wrapping<$t>) {
                 *self = *self + other;
             }
@@ -147,7 +147,7 @@ macro_rules! wrapping_impl {
         impl Sub for Wrapping<$t> {
             type Output = Wrapping<$t>;
 
-            #[inline(always)]
+            #[inline]
             fn sub(self, other: Wrapping<$t>) -> Wrapping<$t> {
                 Wrapping(self.0.wrapping_sub(other.0))
             }
@@ -157,7 +157,7 @@ macro_rules! wrapping_impl {
 
         #[stable(feature = "op_assign_traits", since = "1.8.0")]
         impl SubAssign for Wrapping<$t> {
-            #[inline(always)]
+            #[inline]
             fn sub_assign(&mut self, other: Wrapping<$t>) {
                 *self = *self - other;
             }
@@ -167,7 +167,7 @@ macro_rules! wrapping_impl {
         impl Mul for Wrapping<$t> {
             type Output = Wrapping<$t>;
 
-            #[inline(always)]
+            #[inline]
             fn mul(self, other: Wrapping<$t>) -> Wrapping<$t> {
                 Wrapping(self.0.wrapping_mul(other.0))
             }
@@ -177,7 +177,7 @@ macro_rules! wrapping_impl {
 
         #[stable(feature = "op_assign_traits", since = "1.8.0")]
         impl MulAssign for Wrapping<$t> {
-            #[inline(always)]
+            #[inline]
             fn mul_assign(&mut self, other: Wrapping<$t>) {
                 *self = *self * other;
             }
@@ -187,7 +187,7 @@ macro_rules! wrapping_impl {
         impl Div for Wrapping<$t> {
             type Output = Wrapping<$t>;
 
-            #[inline(always)]
+            #[inline]
             fn div(self, other: Wrapping<$t>) -> Wrapping<$t> {
                 Wrapping(self.0.wrapping_div(other.0))
             }
@@ -197,7 +197,7 @@ macro_rules! wrapping_impl {
 
         #[stable(feature = "op_assign_traits", since = "1.8.0")]
         impl DivAssign for Wrapping<$t> {
-            #[inline(always)]
+            #[inline]
             fn div_assign(&mut self, other: Wrapping<$t>) {
                 *self = *self / other;
             }
@@ -207,7 +207,7 @@ macro_rules! wrapping_impl {
         impl Rem for Wrapping<$t> {
             type Output = Wrapping<$t>;
 
-            #[inline(always)]
+            #[inline]
             fn rem(self, other: Wrapping<$t>) -> Wrapping<$t> {
                 Wrapping(self.0.wrapping_rem(other.0))
             }
@@ -217,7 +217,7 @@ macro_rules! wrapping_impl {
 
         #[stable(feature = "op_assign_traits", since = "1.8.0")]
         impl RemAssign for Wrapping<$t> {
-            #[inline(always)]
+            #[inline]
             fn rem_assign(&mut self, other: Wrapping<$t>) {
                 *self = *self % other;
             }
@@ -227,7 +227,7 @@ macro_rules! wrapping_impl {
         impl Not for Wrapping<$t> {
             type Output = Wrapping<$t>;
 
-            #[inline(always)]
+            #[inline]
             fn not(self) -> Wrapping<$t> {
                 Wrapping(!self.0)
             }
@@ -239,7 +239,7 @@ macro_rules! wrapping_impl {
         impl BitXor for Wrapping<$t> {
             type Output = Wrapping<$t>;
 
-            #[inline(always)]
+            #[inline]
             fn bitxor(self, other: Wrapping<$t>) -> Wrapping<$t> {
                 Wrapping(self.0 ^ other.0)
             }
@@ -249,7 +249,7 @@ macro_rules! wrapping_impl {
 
         #[stable(feature = "op_assign_traits", since = "1.8.0")]
         impl BitXorAssign for Wrapping<$t> {
-            #[inline(always)]
+            #[inline]
             fn bitxor_assign(&mut self, other: Wrapping<$t>) {
                 *self = *self ^ other;
             }
@@ -259,7 +259,7 @@ macro_rules! wrapping_impl {
         impl BitOr for Wrapping<$t> {
             type Output = Wrapping<$t>;
 
-            #[inline(always)]
+            #[inline]
             fn bitor(self, other: Wrapping<$t>) -> Wrapping<$t> {
                 Wrapping(self.0 | other.0)
             }
@@ -269,7 +269,7 @@ macro_rules! wrapping_impl {
 
         #[stable(feature = "op_assign_traits", since = "1.8.0")]
         impl BitOrAssign for Wrapping<$t> {
-            #[inline(always)]
+            #[inline]
             fn bitor_assign(&mut self, other: Wrapping<$t>) {
                 *self = *self | other;
             }
@@ -279,7 +279,7 @@ macro_rules! wrapping_impl {
         impl BitAnd for Wrapping<$t> {
             type Output = Wrapping<$t>;
 
-            #[inline(always)]
+            #[inline]
             fn bitand(self, other: Wrapping<$t>) -> Wrapping<$t> {
                 Wrapping(self.0 & other.0)
             }
@@ -289,7 +289,7 @@ macro_rules! wrapping_impl {
 
         #[stable(feature = "op_assign_traits", since = "1.8.0")]
         impl BitAndAssign for Wrapping<$t> {
-            #[inline(always)]
+            #[inline]
             fn bitand_assign(&mut self, other: Wrapping<$t>) {
                 *self = *self & other;
             }
@@ -298,7 +298,7 @@ macro_rules! wrapping_impl {
         #[stable(feature = "wrapping_neg", since = "1.10.0")]
         impl Neg for Wrapping<$t> {
             type Output = Self;
-            #[inline(always)]
+            #[inline]
             fn neg(self) -> Self {
                 Wrapping(0) - self
             }

src/libcore/ptr.rs

@@ -244,7 +244,7 @@ pub unsafe fn replace<T>(dest: *mut T, mut src: T) -> T {
 ///     assert_eq!(std::ptr::read(y), 12);
 /// }
 /// ```
-#[inline(always)]
+#[inline]
 #[stable(feature = "rust1", since = "1.0.0")]
 pub unsafe fn read<T>(src: *const T) -> T {
     let mut tmp: T = mem::uninitialized();
@@ -278,7 +278,7 @@ pub unsafe fn read<T>(src: *const T) -> T {
 ///     assert_eq!(std::ptr::read_unaligned(y), 12);
 /// }
 /// ```
-#[inline(always)]
+#[inline]
 #[stable(feature = "ptr_unaligned", since = "1.17.0")]
 pub unsafe fn read_unaligned<T>(src: *const T) -> T {
     let mut tmp: T = mem::uninitialized();

src/libcore/slice/mod.rs

@@ -1105,7 +1105,7 @@ impl<'a, T> IntoIterator for &'a mut [T] {
     }
 }
 
-#[inline(always)]
+#[inline]
 fn size_from_ptr<T>(_: *const T) -> usize {
     mem::size_of::<T>()
 }