Auto merge of #27823 - eefriedman:float-dep-core, r=alexcrichton

There wasn't any particular reason the functions needed to be there
anyway, so just get rid of them, and adjust libstd to compensate.

With this change, libcore depends on exactly two floating-point functions:
fmod and fmodf.  They are implicitly referenced because they are used to
implement "%".

Dependencies of libcore on Linux x86-x64 with this patch:
```
0000000000000000         *UND*	0000000000000000 __powidf2
0000000000000000         *UND*	0000000000000000 __powisf2
0000000000000000         *UND*	0000000000000000 fmod
0000000000000000         *UND*	0000000000000000 fmodf
0000000000000000         *UND*	0000000000000000 memcmp
0000000000000000         *UND*	0000000000000000 memcpy
0000000000000000         *UND*	0000000000000000 memset
0000000000000000         *UND*	0000000000000000 rust_begin_unwind
0000000000000000         *UND*	0000000000000000 rust_eh_personality
```

8 files changed, 3 insertions, 280 deletions

diff --git a/src/libcore/num/f32.rs b/src/libcore/num/f32.rs
index 6ce037f17ae..1b7cbb050d1 100644
--- a/src/libcore/num/f32.rs
+++ b/src/libcore/num/f32.rs
@@ -216,63 +216,6 @@ impl Float for f32 {
         (mantissa as u64, exponent, sign)
     }
 
-    /// Rounds towards minus infinity.
-    #[inline]
-    fn floor(self) -> f32 {
-        return floorf(self);
-
-        // On MSVC LLVM will lower many math intrinsics to a call to the
-        // corresponding function. On MSVC, however, many of these functions
-        // aren't actually available as symbols to call, but rather they are all
-        // `static inline` functions in header files. This means that from a C
-        // perspective it's "compatible", but not so much from an ABI
-        // perspective (which we're worried about).
-        //
-        // The inline header functions always just cast to a f64 and do their
-        // operation, so we do that here as well, but only for MSVC targets.
-        //
-        // Note that there are many MSVC-specific float operations which
-        // redirect to this comment, so `floorf` is just one case of a missing
-        // function on MSVC, but there are many others elsewhere.
-        #[cfg(target_env = "msvc")]
-        fn floorf(f: f32) -> f32 { (f as f64).floor() as f32 }
-        #[cfg(not(target_env = "msvc"))]
-        fn floorf(f: f32) -> f32 { unsafe { intrinsics::floorf32(f) } }
-    }
-
-    /// Rounds towards plus infinity.
-    #[inline]
-    fn ceil(self) -> f32 {
-        return ceilf(self);
-
-        // see notes above in `floor`
-        #[cfg(target_env = "msvc")]
-        fn ceilf(f: f32) -> f32 { (f as f64).ceil() as f32 }
-        #[cfg(not(target_env = "msvc"))]
-        fn ceilf(f: f32) -> f32 { unsafe { intrinsics::ceilf32(f) } }
-    }
-
-    /// Rounds to nearest integer. Rounds half-way cases away from zero.
-    #[inline]
-    fn round(self) -> f32 {
-        unsafe { intrinsics::roundf32(self) }
-    }
-
-    /// Returns the integer part of the number (rounds towards zero).
-    #[inline]
-    fn trunc(self) -> f32 {
-        unsafe { intrinsics::truncf32(self) }
-    }
-
-    /// The fractional part of the number, satisfying:
-    ///
-    /// ```
-    /// let x = 1.65f32;
-    /// assert!(x == x.trunc() + x.fract())
-    /// ```
-    #[inline]
-    fn fract(self) -> f32 { self - self.trunc() }
-
     /// Computes the absolute value of `self`. Returns `Float::nan()` if the
     /// number is `Float::nan()`.
     #[inline]
@@ -308,14 +251,6 @@ impl Float for f32 {
         self < 0.0 || (1.0 / self) == Float::neg_infinity()
     }
 
-    /// Fused multiply-add. Computes `(self * a) + b` with only one rounding
-    /// error. This produces a more accurate result with better performance than
-    /// a separate multiplication operation followed by an add.
-    #[inline]
-    fn mul_add(self, a: f32, b: f32) -> f32 {
-        unsafe { intrinsics::fmaf32(self, a, b) }
-    }
-
     /// Returns the reciprocal (multiplicative inverse) of the number.
     #[inline]
     fn recip(self) -> f32 { 1.0 / self }
@@ -325,81 +260,6 @@ impl Float for f32 {
         unsafe { intrinsics::powif32(self, n) }
     }
 
-    #[inline]
-    fn powf(self, n: f32) -> f32 {
-        return powf(self, n);
-
-        // see notes above in `floor`
-        #[cfg(target_env = "msvc")]
-        fn powf(f: f32, n: f32) -> f32 { (f as f64).powf(n as f64) as f32 }
-        #[cfg(not(target_env = "msvc"))]
-        fn powf(f: f32, n: f32) -> f32 { unsafe { intrinsics::powf32(f, n) } }
-    }
-
-    #[inline]
-    fn sqrt(self) -> f32 {
-        if self < 0.0 {
-            NAN
-        } else {
-            unsafe { intrinsics::sqrtf32(self) }
-        }
-    }
-
-    #[inline]
-    fn rsqrt(self) -> f32 { self.sqrt().recip() }
-
-    /// Returns the exponential of the number.
-    #[inline]
-    fn exp(self) -> f32 {
-        return expf(self);
-
-        // see notes above in `floor`
-        #[cfg(target_env = "msvc")]
-        fn expf(f: f32) -> f32 { (f as f64).exp() as f32 }
-        #[cfg(not(target_env = "msvc"))]
-        fn expf(f: f32) -> f32 { unsafe { intrinsics::expf32(f) } }
-    }
-
-    /// Returns 2 raised to the power of the number.
-    #[inline]
-    fn exp2(self) -> f32 {
-        unsafe { intrinsics::exp2f32(self) }
-    }
-
-    /// Returns the natural logarithm of the number.
-    #[inline]
-    fn ln(self) -> f32 {
-        return logf(self);
-
-        // see notes above in `floor`
-        #[cfg(target_env = "msvc")]
-        fn logf(f: f32) -> f32 { (f as f64).ln() as f32 }
-        #[cfg(not(target_env = "msvc"))]
-        fn logf(f: f32) -> f32 { unsafe { intrinsics::logf32(f) } }
-    }
-
-    /// Returns the logarithm of the number with respect to an arbitrary base.
-    #[inline]
-    fn log(self, base: f32) -> f32 { self.ln() / base.ln() }
-
-    /// Returns the base 2 logarithm of the number.
-    #[inline]
-    fn log2(self) -> f32 {
-        unsafe { intrinsics::log2f32(self) }
-    }
-
-    /// Returns the base 10 logarithm of the number.
-    #[inline]
-    fn log10(self) -> f32 {
-        return log10f(self);
-
-        // see notes above in `floor`
-        #[cfg(target_env = "msvc")]
-        fn log10f(f: f32) -> f32 { (f as f64).log10() as f32 }
-        #[cfg(not(target_env = "msvc"))]
-        fn log10f(f: f32) -> f32 { unsafe { intrinsics::log10f32(f) } }
-    }
-
     /// Converts to degrees, assuming the number is in radians.
     #[inline]
     fn to_degrees(self) -> f32 { self * (180.0f32 / consts::PI) }
diff --git a/src/libcore/num/f64.rs b/src/libcore/num/f64.rs
index b9dbc046799..a057e5fe51a 100644
--- a/src/libcore/num/f64.rs
+++ b/src/libcore/num/f64.rs
@@ -216,39 +216,6 @@ impl Float for f64 {
         (mantissa, exponent, sign)
     }
 
-    /// Rounds towards minus infinity.
-    #[inline]
-    fn floor(self) -> f64 {
-        unsafe { intrinsics::floorf64(self) }
-    }
-
-    /// Rounds towards plus infinity.
-    #[inline]
-    fn ceil(self) -> f64 {
-        unsafe { intrinsics::ceilf64(self) }
-    }
-
-    /// Rounds to nearest integer. Rounds half-way cases away from zero.
-    #[inline]
-    fn round(self) -> f64 {
-        unsafe { intrinsics::roundf64(self) }
-    }
-
-    /// Returns the integer part of the number (rounds towards zero).
-    #[inline]
-    fn trunc(self) -> f64 {
-        unsafe { intrinsics::truncf64(self) }
-    }
-
-    /// The fractional part of the number, satisfying:
-    ///
-    /// ```
-    /// let x = 1.65f64;
-    /// assert!(x == x.trunc() + x.fract())
-    /// ```
-    #[inline]
-    fn fract(self) -> f64 { self - self.trunc() }
-
     /// Computes the absolute value of `self`. Returns `Float::nan()` if the
     /// number is `Float::nan()`.
     #[inline]
@@ -284,74 +251,15 @@ impl Float for f64 {
         self < 0.0 || (1.0 / self) == Float::neg_infinity()
     }
 
-    /// Fused multiply-add. Computes `(self * a) + b` with only one rounding
-    /// error. This produces a more accurate result with better performance than
-    /// a separate multiplication operation followed by an add.
-    #[inline]
-    fn mul_add(self, a: f64, b: f64) -> f64 {
-        unsafe { intrinsics::fmaf64(self, a, b) }
-    }
-
     /// Returns the reciprocal (multiplicative inverse) of the number.
     #[inline]
     fn recip(self) -> f64 { 1.0 / self }
 
     #[inline]
-    fn powf(self, n: f64) -> f64 {
-        unsafe { intrinsics::powf64(self, n) }
-    }
-
-    #[inline]
     fn powi(self, n: i32) -> f64 {
         unsafe { intrinsics::powif64(self, n) }
     }
 
-    #[inline]
-    fn sqrt(self) -> f64 {
-        if self < 0.0 {
-            NAN
-        } else {
-            unsafe { intrinsics::sqrtf64(self) }
-        }
-    }
-
-    #[inline]
-    fn rsqrt(self) -> f64 { self.sqrt().recip() }
-
-    /// Returns the exponential of the number.
-    #[inline]
-    fn exp(self) -> f64 {
-        unsafe { intrinsics::expf64(self) }
-    }
-
-    /// Returns 2 raised to the power of the number.
-    #[inline]
-    fn exp2(self) -> f64 {
-        unsafe { intrinsics::exp2f64(self) }
-    }
-
-    /// Returns the natural logarithm of the number.
-    #[inline]
-    fn ln(self) -> f64 {
-        unsafe { intrinsics::logf64(self) }
-    }
-
-    /// Returns the logarithm of the number with respect to an arbitrary base.
-    #[inline]
-    fn log(self, base: f64) -> f64 { self.ln() / base.ln() }
-
-    /// Returns the base 2 logarithm of the number.
-    #[inline]
-    fn log2(self) -> f64 {
-        unsafe { intrinsics::log2f64(self) }
-    }
-
-    /// Returns the base 10 logarithm of the number.
-    #[inline]
-    fn log10(self) -> f64 {
-        unsafe { intrinsics::log10f64(self) }
-    }
-
     /// Converts to degrees, assuming the number is in radians.
     #[inline]
     fn to_degrees(self) -> f64 { self * (180.0f64 / consts::PI) }
diff --git a/src/libcore/num/flt2dec/decoder.rs b/src/libcore/num/flt2dec/decoder.rs
index a292ffa2e9d..6265691bde9 100644
--- a/src/libcore/num/flt2dec/decoder.rs
+++ b/src/libcore/num/flt2dec/decoder.rs
@@ -53,20 +53,15 @@ pub enum FullDecoded {
 
 /// A floating point type which can be `decode`d.
 pub trait DecodableFloat: Float + Copy {
-    /// Returns `x * 2^exp`. Almost same to `std::{f32,f64}::ldexp`.
-    /// This is used for testing.
-    fn ldexpi(f: i64, exp: isize) -> Self;
     /// The minimum positive normalized value.
     fn min_pos_norm_value() -> Self;
 }
 
 impl DecodableFloat for f32 {
-    fn ldexpi(f: i64, exp: isize) -> Self { f as Self * (exp as Self).exp2() }
     fn min_pos_norm_value() -> Self { f32::MIN_POSITIVE }
 }
 
 impl DecodableFloat for f64 {
-    fn ldexpi(f: i64, exp: isize) -> Self { f as Self * (exp as Self).exp2() }
     fn min_pos_norm_value() -> Self { f64::MIN_POSITIVE }
 }
 
diff --git a/src/libcore/num/flt2dec/mod.rs b/src/libcore/num/flt2dec/mod.rs
index 91e1d6e4e51..700523e49a2 100644
--- a/src/libcore/num/flt2dec/mod.rs
+++ b/src/libcore/num/flt2dec/mod.rs
@@ -132,7 +132,6 @@ functions.
 
 use prelude::v1::*;
 use i16;
-use num::Float;
 use slice::bytes;
 pub use self::decoder::{decode, DecodableFloat, FullDecoded, Decoded};
 
diff --git a/src/libcore/num/flt2dec/strategy/dragon.rs b/src/libcore/num/flt2dec/strategy/dragon.rs
index cdc23c45fa0..ab610f28e9e 100644
--- a/src/libcore/num/flt2dec/strategy/dragon.rs
+++ b/src/libcore/num/flt2dec/strategy/dragon.rs
@@ -17,7 +17,6 @@ Almost direct (but slightly optimized) Rust translation of Figure 3 of [1].
 
 use prelude::v1::*;
 
-use num::Float;
 use cmp::Ordering;
 
 use num::flt2dec::{Decoded, MAX_SIG_DIGITS, round_up};
diff --git a/src/libcore/num/flt2dec/strategy/grisu.rs b/src/libcore/num/flt2dec/strategy/grisu.rs
index 52eafcec184..b0822ca76c7 100644
--- a/src/libcore/num/flt2dec/strategy/grisu.rs
+++ b/src/libcore/num/flt2dec/strategy/grisu.rs
@@ -18,8 +18,6 @@ Rust adaptation of Grisu3 algorithm described in [1]. It uses about
 
 use prelude::v1::*;
 
-use num::Float;
-
 use num::flt2dec::{Decoded, MAX_SIG_DIGITS, round_up};
 
 /// A custom 64-bit floating point type, representing `f * 2^e`.
diff --git a/src/libcore/num/mod.rs b/src/libcore/num/mod.rs
index 086437445de..23432a2044c 100644
--- a/src/libcore/num/mod.rs
+++ b/src/libcore/num/mod.rs
@@ -1297,18 +1297,6 @@ pub trait Float: Sized {
     /// Returns the mantissa, exponent and sign as integers, respectively.
     fn integer_decode(self) -> (u64, i16, i8);
 
-    /// Return the largest integer less than or equal to a number.
-    fn floor(self) -> Self;
-    /// Return the smallest integer greater than or equal to a number.
-    fn ceil(self) -> Self;
-    /// Return the nearest integer to a number. Round half-way cases away from
-    /// `0.0`.
-    fn round(self) -> Self;
-    /// Return the integer part of a number.
-    fn trunc(self) -> Self;
-    /// Return the fractional part of a number.
-    fn fract(self) -> Self;
-
     /// Computes the absolute value of `self`. Returns `Float::nan()` if the
     /// number is `Float::nan()`.
     fn abs(self) -> Self;
@@ -1325,10 +1313,6 @@ pub trait Float: Sized {
     /// `Float::neg_infinity()`.
     fn is_negative(self) -> bool;
 
-    /// Fused multiply-add. Computes `(self * a) + b` with only one rounding
-    /// error. This produces a more accurate result with better performance than
-    /// a separate multiplication operation followed by an add.
-    fn mul_add(self, a: Self, b: Self) -> Self;
     /// Take the reciprocal (inverse) of a number, `1/x`.
     fn recip(self) -> Self;
 
@@ -1336,28 +1320,6 @@ pub trait Float: Sized {
     ///
     /// Using this function is generally faster than using `powf`
     fn powi(self, n: i32) -> Self;
-    /// Raise a number to a floating point power.
-    fn powf(self, n: Self) -> Self;
-
-    /// Take the square root of a number.
-    ///
-    /// Returns NaN if `self` is a negative number.
-    fn sqrt(self) -> Self;
-    /// Take the reciprocal (inverse) square root of a number, `1/sqrt(x)`.
-    fn rsqrt(self) -> Self;
-
-    /// Returns `e^(self)`, (the exponential function).
-    fn exp(self) -> Self;
-    /// Returns 2 raised to the power of the number, `2^(self)`.
-    fn exp2(self) -> Self;
-    /// Returns the natural logarithm of the number.
-    fn ln(self) -> Self;
-    /// Returns the logarithm of the number with respect to an arbitrary base.
-    fn log(self, base: Self) -> Self;
-    /// Returns the base 2 logarithm of the number.
-    fn log2(self) -> Self;
-    /// Returns the base 10 logarithm of the number.
-    fn log10(self) -> Self;
 
     /// Convert radians to degrees.
     fn to_degrees(self) -> Self;
diff --git a/src/libcore/ops.rs b/src/libcore/ops.rs
index 6d522ad1fab..7c386c6c33e 100644
--- a/src/libcore/ops.rs
+++ b/src/libcore/ops.rs
@@ -445,7 +445,9 @@ rem_impl! { usize u8 u16 u32 u64 isize i8 i16 i32 i64 }
 impl Rem for f32 {
     type Output = f32;
 
-    // see notes in `core::f32::Float::floor`
+    // The builtin f32 rem operator is broken when targeting
+    // MSVC; see comment in std::f32::floor.
+    // FIXME: See also #27859.
     #[inline]
     #[cfg(target_env = "msvc")]
     fn rem(self, other: f32) -> f32 {