Merge pull request rust-lang#454 from tgross35/generic-rint

Add `rintf16` and `rintf128`

Author: tgross35

crates/compiler-builtins-smoke-test/src/lib.rs

@@ -145,6 +145,8 @@ no_mangle! {
     remquof(x: f32, y: f32 | q: &mut c_int) -> f32;
     rint(x: f64) -> f64;
     rintf(x: f32) -> f32;
+    rintf128(x: f128) -> f128;
+    rintf16(x: f16) -> f16;
     round(x: f64) -> f64;
     roundf(x: f32) -> f32;
     scalbn(x: f64, y: c_int) -> f64;

crates/libm-macros/src/shared.rs

@@ -9,7 +9,7 @@ const ALL_OPERATIONS_NESTED: &[(FloatTy, Signature, Option<Signature>, &[&str])]
         FloatTy::F16,
         Signature { args: &[Ty::F16], returns: &[Ty::F16] },
         None,
-        &["ceilf16", "fabsf16", "floorf16", "sqrtf16", "truncf16"],
+        &["ceilf16", "fabsf16", "floorf16", "rintf16", "sqrtf16", "truncf16"],
     ),
     (
         // `fn(f32) -> f32`
@@ -40,7 +40,7 @@ const ALL_OPERATIONS_NESTED: &[(FloatTy, Signature, Option<Signature>, &[&str])]
         FloatTy::F128,
         Signature { args: &[Ty::F128], returns: &[Ty::F128] },
         None,
-        &["ceilf128", "fabsf128", "floorf128", "sqrtf128", "truncf128"],
+        &["ceilf128", "fabsf128", "floorf128", "rintf128", "sqrtf128", "truncf128"],
     ),
     (
         // `(f16, f16) -> f16`

crates/libm-test/benches/icount.rs

@@ -149,6 +149,8 @@ main!(
     icount_bench_remquo_group,
     icount_bench_remquof_group,
     icount_bench_rint_group,
+    icount_bench_rintf128_group,
+    icount_bench_rintf16_group,
     icount_bench_rintf_group,
     icount_bench_round_group,
     icount_bench_roundf_group,

crates/libm-test/benches/random.rs

@@ -127,6 +127,8 @@ libm_macros::for_each_function! {
         | fdimf16
         | floorf128
         | floorf16
+        | rintf128
+        | rintf16
         | sqrtf128
         | sqrtf16
         | truncf128

crates/libm-test/src/mpfloat.rs

@@ -170,6 +170,8 @@ libm_macros::for_each_function! {
         remquof,
         rint,
         rintf,
+        rintf128,
+        rintf16,
         round,
         roundf,
         scalbn,
@@ -240,17 +242,19 @@ impl_no_round! {
 
 #[cfg(f16_enabled)]
 impl_no_round! {
-    fabsf16 => abs_mut;
     ceilf16 => ceil_mut;
+    fabsf16 => abs_mut;
     floorf16 => floor_mut;
+    rintf16 => round_even_mut; // FIXME: respect rounding mode
     truncf16 => trunc_mut;
 }
 
 #[cfg(f128_enabled)]
 impl_no_round! {
-    fabsf128 => abs_mut;
     ceilf128 => ceil_mut;
+    fabsf128 => abs_mut;
     floorf128 => floor_mut;
+    rintf128 => round_even_mut; // FIXME: respect rounding mode
     truncf128 => trunc_mut;
 }
 

crates/libm-test/tests/compare_built_musl.rs

@@ -89,9 +89,11 @@ libm_macros::for_each_function! {
         fdimf16,
         floorf128,
         floorf16,
+        rintf128,
+        rintf16,
+        sqrtf128,
+        sqrtf16,
         truncf128,
         truncf16,
-        sqrtf16,
-        sqrtf128,
     ],
 }

crates/util/src/main.rs

@@ -94,6 +94,8 @@ fn do_eval(basis: &str, op: &str, inputs: &[&str]) {
             | fdimf16
             | floorf128
             | floorf16
+            | rintf128
+            | rintf16
             | sqrtf128
             | sqrtf16
             | truncf128

etc/function-definitions.json

@@ -654,6 +654,7 @@
             "src/libm_helper.rs",
             "src/math/arch/aarch64.rs",
             "src/math/arch/wasm32.rs",
+            "src/math/generic/rint.rs",
             "src/math/rint.rs"
         ],
         "type": "f64"
@@ -662,10 +663,25 @@
         "sources": [
             "src/math/arch/aarch64.rs",
             "src/math/arch/wasm32.rs",
+            "src/math/generic/rint.rs",
             "src/math/rintf.rs"
         ],
         "type": "f32"
     },
+    "rintf128": {
+        "sources": [
+            "src/math/generic/rint.rs",
+            "src/math/rintf128.rs"
+        ],
+        "type": "f128"
+    },
+    "rintf16": {
+        "sources": [
+            "src/math/generic/rint.rs",
+            "src/math/rintf16.rs"
+        ],
+        "type": "f16"
+    },
     "round": {
         "sources": [
             "src/libm_helper.rs",

etc/function-list.txt

@@ -97,6 +97,8 @@ remquo
 remquof
 rint
 rintf
+rintf128
+rintf16
 round
 roundf
 scalbn

src/math/generic/mod.rs

@@ -3,6 +3,7 @@ mod copysign;
 mod fabs;
 mod fdim;
 mod floor;
+mod rint;
 mod sqrt;
 mod trunc;
 
@@ -11,5 +12,6 @@ pub use copysign::copysign;
 pub use fabs::fabs;
 pub use fdim::fdim;
 pub use floor::floor;
+pub use rint::rint;
 pub use sqrt::sqrt;
 pub use trunc::trunc;

src/math/generic/rint.rs

@@ -0,0 +1,72 @@
+/* SPDX-License-Identifier: MIT */
+/* origin: musl src/math/rint.c */
+
+use super::super::Float;
+
+pub fn rint<F: Float>(x: F) -> F {
+    let toint = F::ONE / F::EPSILON;
+    let e = x.exp();
+    let positive = x.is_sign_positive();
+
+    // On i386 `force_eval!` must be used to force rounding via storage to memory. Otherwise,
+    // the excess precission from x87 would cause an incorrect final result.
+    let use_force = cfg!(x86_no_sse) && F::BITS == 32 || F::BITS == 64;
+
+    if e >= F::EXP_BIAS + F::SIG_BITS {
+        // No fractional part; exact result can be returned.
+        x
+    } else {
+        // Apply a net-zero adjustment that nudges `y` in the direction of the rounding mode.
+        let y = if positive {
+            let tmp = if use_force { force_eval!(x) } else { x } + toint;
+            (if use_force { force_eval!(tmp) } else { tmp } - toint)
+        } else {
+            let tmp = if use_force { force_eval!(x) } else { x } - toint;
+            (if use_force { force_eval!(tmp) } else { tmp } + toint)
+        };
+
+        if y == F::ZERO {
+            // A zero result takes the sign of the input.
+            if positive { F::ZERO } else { F::NEG_ZERO }
+        } else {
+            y
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn zeroes_f32() {
+        assert_biteq!(rint(0.0_f32), 0.0_f32);
+        assert_biteq!(rint(-0.0_f32), -0.0_f32);
+    }
+
+    #[test]
+    fn sanity_check_f32() {
+        assert_biteq!(rint(-1.0_f32), -1.0);
+        assert_biteq!(rint(2.8_f32), 3.0);
+        assert_biteq!(rint(-0.5_f32), -0.0);
+        assert_biteq!(rint(0.5_f32), 0.0);
+        assert_biteq!(rint(-1.5_f32), -2.0);
+        assert_biteq!(rint(1.5_f32), 2.0);
+    }
+
+    #[test]
+    fn zeroes_f64() {
+        assert_biteq!(rint(0.0_f64), 0.0_f64);
+        assert_biteq!(rint(-0.0_f64), -0.0_f64);
+    }
+
+    #[test]
+    fn sanity_check_f64() {
+        assert_biteq!(rint(-1.0_f64), -1.0);
+        assert_biteq!(rint(2.8_f64), 3.0);
+        assert_biteq!(rint(-0.5_f64), -0.0);
+        assert_biteq!(rint(0.5_f64), 0.0);
+        assert_biteq!(rint(-1.5_f64), -2.0);
+        assert_biteq!(rint(1.5_f64), 2.0);
+    }
+}

src/math/mod.rs

@@ -346,6 +346,7 @@ cfg_if! {
         mod fabsf16;
         mod fdimf16;
         mod floorf16;
+        mod rintf16;
         mod sqrtf16;
         mod truncf16;
 
@@ -354,6 +355,7 @@ cfg_if! {
         pub use self::fabsf16::fabsf16;
         pub use self::fdimf16::fdimf16;
         pub use self::floorf16::floorf16;
+        pub use self::rintf16::rintf16;
         pub use self::sqrtf16::sqrtf16;
         pub use self::truncf16::truncf16;
     }
@@ -366,6 +368,7 @@ cfg_if! {
         mod fabsf128;
         mod fdimf128;
         mod floorf128;
+        mod rintf128;
         mod sqrtf128;
         mod truncf128;
 
@@ -374,6 +377,7 @@ cfg_if! {
         pub use self::fabsf128::fabsf128;
         pub use self::fdimf128::fdimf128;
         pub use self::floorf128::floorf128;
+        pub use self::rintf128::rintf128;
         pub use self::sqrtf128::sqrtf128;
         pub use self::truncf128::truncf128;
     }

src/math/rint.rs

@@ -1,3 +1,4 @@
+/// Round `x` to the nearest integer, breaking ties toward even.
 #[cfg_attr(all(test, assert_no_panic), no_panic::no_panic)]
 pub fn rint(x: f64) -> f64 {
     select_implementation! {
@@ -9,51 +10,5 @@ pub fn rint(x: f64) -> f64 {
         args: x,
     }
 
-    let one_over_e = 1.0 / f64::EPSILON;
-    let as_u64: u64 = x.to_bits();
-    let exponent: u64 = (as_u64 >> 52) & 0x7ff;
-    let is_positive = (as_u64 >> 63) == 0;
-    if exponent >= 0x3ff + 52 {
-        x
-    } else {
-        let ans = if is_positive {
-            #[cfg(all(target_arch = "x86", not(target_feature = "sse2")))]
-            let x = force_eval!(x);
-            let xplusoneovere = x + one_over_e;
-            #[cfg(all(target_arch = "x86", not(target_feature = "sse2")))]
-            let xplusoneovere = force_eval!(xplusoneovere);
-            xplusoneovere - one_over_e
-        } else {
-            #[cfg(all(target_arch = "x86", not(target_feature = "sse2")))]
-            let x = force_eval!(x);
-            let xminusoneovere = x - one_over_e;
-            #[cfg(all(target_arch = "x86", not(target_feature = "sse2")))]
-            let xminusoneovere = force_eval!(xminusoneovere);
-            xminusoneovere + one_over_e
-        };
-
-        if ans == 0.0 { if is_positive { 0.0 } else { -0.0 } } else { ans }
-    }
-}
-
-// PowerPC tests are failing on LLVM 13: https://github.com/rust-lang/rust/issues/88520
-#[cfg(not(target_arch = "powerpc64"))]
-#[cfg(test)]
-mod tests {
-    use super::rint;
-
-    #[test]
-    fn negative_zero() {
-        assert_eq!(rint(-0.0_f64).to_bits(), (-0.0_f64).to_bits());
-    }
-
-    #[test]
-    fn sanity_check() {
-        assert_eq!(rint(-1.0), -1.0);
-        assert_eq!(rint(2.8), 3.0);
-        assert_eq!(rint(-0.5), -0.0);
-        assert_eq!(rint(0.5), 0.0);
-        assert_eq!(rint(-1.5), -2.0);
-        assert_eq!(rint(1.5), 2.0);
-    }
+    super::generic::rint(x)
 }

src/math/rintf.rs

@@ -1,3 +1,4 @@
+/// Round `x` to the nearest integer, breaking ties toward even.
 #[cfg_attr(all(test, assert_no_panic), no_panic::no_panic)]
 pub fn rintf(x: f32) -> f32 {
     select_implementation! {
@@ -9,51 +10,5 @@ pub fn rintf(x: f32) -> f32 {
         args: x,
     }
 
-    let one_over_e = 1.0 / f32::EPSILON;
-    let as_u32: u32 = x.to_bits();
-    let exponent: u32 = (as_u32 >> 23) & 0xff;
-    let is_positive = (as_u32 >> 31) == 0;
-    if exponent >= 0x7f + 23 {
-        x
-    } else {
-        let ans = if is_positive {
-            #[cfg(all(target_arch = "x86", not(target_feature = "sse2")))]
-            let x = force_eval!(x);
-            let xplusoneovere = x + one_over_e;
-            #[cfg(all(target_arch = "x86", not(target_feature = "sse2")))]
-            let xplusoneovere = force_eval!(xplusoneovere);
-            xplusoneovere - one_over_e
-        } else {
-            #[cfg(all(target_arch = "x86", not(target_feature = "sse2")))]
-            let x = force_eval!(x);
-            let xminusoneovere = x - one_over_e;
-            #[cfg(all(target_arch = "x86", not(target_feature = "sse2")))]
-            let xminusoneovere = force_eval!(xminusoneovere);
-            xminusoneovere + one_over_e
-        };
-
-        if ans == 0.0 { if is_positive { 0.0 } else { -0.0 } } else { ans }
-    }
-}
-
-// PowerPC tests are failing on LLVM 13: https://github.com/rust-lang/rust/issues/88520
-#[cfg(not(target_arch = "powerpc64"))]
-#[cfg(test)]
-mod tests {
-    use super::rintf;
-
-    #[test]
-    fn negative_zero() {
-        assert_eq!(rintf(-0.0_f32).to_bits(), (-0.0_f32).to_bits());
-    }
-
-    #[test]
-    fn sanity_check() {
-        assert_eq!(rintf(-1.0), -1.0);
-        assert_eq!(rintf(2.8), 3.0);
-        assert_eq!(rintf(-0.5), -0.0);
-        assert_eq!(rintf(0.5), 0.0);
-        assert_eq!(rintf(-1.5), -2.0);
-        assert_eq!(rintf(1.5), 2.0);
-    }
+    super::generic::rint(x)
 }

src/math/rintf128.rs

@@ -0,0 +1,5 @@
+/// Round `x` to the nearest integer, breaking ties toward even.
+#[cfg_attr(all(test, assert_no_panic), no_panic::no_panic)]
+pub fn rintf128(x: f128) -> f128 {
+    super::generic::rint(x)
+}

src/math/rintf16.rs

@@ -0,0 +1,5 @@
+/// Round `x` to the nearest integer, breaking ties toward even.
+#[cfg_attr(all(test, assert_no_panic), no_panic::no_panic)]
+pub fn rintf16(x: f16) -> f16 {
+    super::generic::rint(x)
+}