Use platform intrinsics, not LLVM, for floor & ceil

This PR removes the direct linkage to LLVM for trunc and round intrinsics, while replacing that link with rustc's platform intrinsics for floor and ceil functions, namely simd_floor and simd_ceil. Tests that are no longer testable are removed. In doing so it resolves the riscv64gc compilation problems.

4 files changed, 17 insertions, 113 deletions

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 8d331257692..2104c74a4d9 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -121,8 +121,7 @@ jobs:
           # for NaNs which makes it worth testing on despite that.
           - mips-unknown-linux-gnu
           - mips64-unknown-linux-gnuabi64
-          # TODO: reenable pending https://github.com/rust-lang/rust/issues/77866
-          # - riscv64gc-unknown-linux-gnu
+          - riscv64gc-unknown-linux-gnu
 
     steps:
       - uses: actions/checkout@v2
diff --git a/crates/core_simd/src/intrinsics.rs b/crates/core_simd/src/intrinsics.rs
index acf85983a98..b2edc3747ef 100644
--- a/crates/core_simd/src/intrinsics.rs
+++ b/crates/core_simd/src/intrinsics.rs
@@ -39,4 +39,10 @@ extern "platform-intrinsic" {
 
     /// fptoui/fptosi/uitofp/sitofp
     pub(crate) fn simd_cast<T, U>(x: T) -> U;
+
+    // floor
+    pub(crate) fn simd_floor<T>(x: T) -> T;
+
+    // ceil
+    pub(crate) fn simd_ceil<T>(x: T) -> T;
 }
diff --git a/crates/core_simd/src/round.rs b/crates/core_simd/src/round.rs
index 021e5af8873..0529bbe0080 100644
--- a/crates/core_simd/src/round.rs
+++ b/crates/core_simd/src/round.rs
@@ -1,60 +1,23 @@
 macro_rules! implement {
     {
         impl $type:ident {
-            int_type = $int_type:ident,
-            floor = $floor_intrinsic:literal,
-            ceil = $ceil_intrinsic:literal,
-            round = $round_intrinsic:literal,
-            trunc = $trunc_intrinsic:literal,
+            int_type = $int_type:ident
         }
     } => {
         mod $type {
-            #[allow(improper_ctypes)]
-            extern "C" {
-                #[link_name = $floor_intrinsic]
-                fn floor_intrinsic(x: crate::$type) -> crate::$type;
-                #[link_name = $ceil_intrinsic]
-                fn ceil_intrinsic(x: crate::$type) -> crate::$type;
-                #[link_name = $round_intrinsic]
-                fn round_intrinsic(x: crate::$type) -> crate::$type;
-                #[link_name = $trunc_intrinsic]
-                fn trunc_intrinsic(x: crate::$type) -> crate::$type;
-            }
-
             impl crate::$type {
                 /// Returns the largest integer less than or equal to each lane.
                 #[must_use = "method returns a new vector and does not mutate the original value"]
                 #[inline]
                 pub fn floor(self) -> Self {
-                    unsafe { floor_intrinsic(self) }
+                    unsafe { crate::intrinsics::simd_floor(self) }
                 }
 
                 /// Returns the smallest integer greater than or equal to each lane.
                 #[must_use = "method returns a new vector and does not mutate the original value"]
                 #[inline]
                 pub fn ceil(self) -> Self {
-                    unsafe { ceil_intrinsic(self) }
-                }
-
-                /// Returns the nearest integer to each lane. Round half-way cases away from 0.0.
-                #[must_use = "method returns a new vector and does not mutate the original value"]
-                #[inline]
-                pub fn round(self) -> Self {
-                    unsafe { round_intrinsic(self) }
-                }
-
-                /// Returns the integer part of each lane.
-                #[must_use = "method returns a new vector and does not mutate the original value"]
-                #[inline]
-                pub fn trunc(self) -> Self {
-                    unsafe { trunc_intrinsic(self) }
-                }
-
-                /// Returns the fractional part of each lane.
-                #[must_use = "method returns a new vector and does not mutate the original value"]
-                #[inline]
-                pub fn fract(self) -> Self {
-                    self - self.trunc()
+                    unsafe { crate::intrinsics::simd_ceil(self) }
                 }
 
                 /// Rounds toward zero and converts to the same-width integer type, assuming that
@@ -84,70 +47,42 @@ macro_rules! implement {
 
 implement! {
     impl f32x2 {
-        int_type = i32x2,
-        floor = "llvm.floor.v2f32",
-        ceil = "llvm.ceil.v2f32",
-        round = "llvm.round.v2f32",
-        trunc = "llvm.trunc.v2f32",
+        int_type = i32x2
     }
 }
 
 implement! {
     impl f32x4 {
-        int_type = i32x4,
-        floor = "llvm.floor.v4f32",
-        ceil = "llvm.ceil.v4f32",
-        round = "llvm.round.v4f32",
-        trunc = "llvm.trunc.v4f32",
+        int_type = i32x4
     }
 }
 
 implement! {
     impl f32x8 {
-        int_type = i32x8,
-        floor = "llvm.floor.v8f32",
-        ceil = "llvm.ceil.v8f32",
-        round = "llvm.round.v8f32",
-        trunc = "llvm.trunc.v8f32",
+        int_type = i32x8
     }
 }
 
 implement! {
     impl f32x16 {
-        int_type = i32x16,
-        floor = "llvm.floor.v16f32",
-        ceil = "llvm.ceil.v16f32",
-        round = "llvm.round.v16f32",
-        trunc = "llvm.trunc.v16f32",
+        int_type = i32x16
     }
 }
 
 implement! {
     impl f64x2 {
-        int_type = i64x2,
-        floor = "llvm.floor.v2f64",
-        ceil = "llvm.ceil.v2f64",
-        round = "llvm.round.v2f64",
-        trunc = "llvm.trunc.v2f64",
+        int_type = i64x2
     }
 }
 
 implement! {
     impl f64x4 {
-        int_type = i64x4,
-        floor = "llvm.floor.v4f64",
-        ceil = "llvm.ceil.v4f64",
-        round = "llvm.round.v4f64",
-        trunc = "llvm.trunc.v4f64",
+        int_type = i64x4
     }
 }
 
 implement! {
     impl f64x8 {
-        int_type = i64x8,
-        floor = "llvm.floor.v8f64",
-        ceil = "llvm.ceil.v8f64",
-        round = "llvm.round.v8f64",
-        trunc = "llvm.trunc.v8f64",
+        int_type = i64x8
     }
 }
diff --git a/crates/core_simd/tests/ops_impl/float_macros.rs b/crates/core_simd/tests/ops_impl/float_macros.rs
index 1f49aef9f12..fe347a5362d 100644
--- a/crates/core_simd/tests/ops_impl/float_macros.rs
+++ b/crates/core_simd/tests/ops_impl/float_macros.rs
@@ -355,42 +355,6 @@ macro_rules! float_tests {
 
             #[test]
             #[cfg_attr(target_arch = "wasm32", wasm_bindgen_test)]
-            fn round_odd_floats() {
-                for v in slice_chunks(&C) {
-                    let expected = apply_unary_lanewise(v, <$scalar>::round);
-                    assert_biteq!(v.round(), expected);
-                }
-            }
-
-            #[test]
-            #[cfg_attr(target_arch = "wasm32", wasm_bindgen_test)]
-            fn round_mode() {
-                assert_biteq!(core_simd::$vector::splat(1.5).round(), core_simd::$vector::splat(2.0));
-                assert_biteq!(core_simd::$vector::splat(2.5).round(), core_simd::$vector::splat(3.0));
-                assert_biteq!(core_simd::$vector::splat(-1.5).round(), core_simd::$vector::splat(-2.0));
-                assert_biteq!(core_simd::$vector::splat(-2.5).round(), core_simd::$vector::splat(-3.0));
-            }
-
-            #[test]
-            #[cfg_attr(target_arch = "wasm32", wasm_bindgen_test)]
-            fn trunc_odd_floats() {
-                for v in slice_chunks(&C) {
-                    let expected = apply_unary_lanewise(v, <$scalar>::trunc);
-                    assert_biteq!(v.trunc(), expected);
-                }
-            }
-
-            #[test]
-            #[cfg_attr(target_arch = "wasm32", wasm_bindgen_test)]
-            fn fract_odd_floats() {
-                for v in slice_chunks(&C) {
-                    let expected = apply_unary_lanewise(v, <$scalar>::fract);
-                    assert_biteq!(v.fract(), expected);
-                }
-            }
-
-            #[test]
-            #[cfg_attr(target_arch = "wasm32", wasm_bindgen_test)]
             fn to_int_unchecked() {
                 // The maximum integer that can be represented by the equivalently sized float has
                 // all of the mantissa digits set to 1, pushed up to the MSB.