Implement simd_round_ties_even for miri, cg_clif and cg_gcc

Author: sayantn

compiler/rustc_codegen_cranelift/src/intrinsics/simd.rs

@@ -495,7 +495,8 @@ pub(super) fn codegen_simd_intrinsic_call<'tcx>(
         | sym::simd_flog
         | sym::simd_flog10
         | sym::simd_flog2
-        | sym::simd_round => {
+        | sym::simd_round
+        | sym::simd_round_ties_even => {
             intrinsic_args!(fx, args => (a); intrinsic);
 
             if !a.layout().ty.is_simd() {
@@ -526,6 +527,8 @@ pub(super) fn codegen_simd_intrinsic_call<'tcx>(
                     (sym::simd_flog2, types::F64) => "log2",
                     (sym::simd_round, types::F32) => "roundf",
                     (sym::simd_round, types::F64) => "round",
+                    (sym::simd_round_ties_even, types::F32) => "rintf",
+                    (sym::simd_round_ties_even, types::F64) => "rint",
                     _ => unreachable!("{:?}", intrinsic),
                 };
                 fx.lib_call(

compiler/rustc_codegen_gcc/src/intrinsic/simd.rs

@@ -779,6 +779,7 @@ pub fn generic_simd_intrinsic<'a, 'gcc, 'tcx>(
             sym::simd_fsin => "sin",
             sym::simd_fsqrt => "sqrt",
             sym::simd_round => "round",
+            sym::simd_round_ties_even => "rint",
             sym::simd_trunc => "trunc",
             _ => return_error!(InvalidMonomorphization::UnrecognizedIntrinsic { span, name }),
         };
@@ -826,6 +827,7 @@ pub fn generic_simd_intrinsic<'a, 'gcc, 'tcx>(
             | sym::simd_fsin
             | sym::simd_fsqrt
             | sym::simd_round
+            | sym::simd_round_ties_even
             | sym::simd_trunc
     ) {
         return simd_simple_float_intrinsic(name, in_elem, in_ty, in_len, bx, span, args);

src/tools/miri/src/intrinsics/simd.rs

@@ -37,6 +37,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
             | "ceil"
             | "floor"
             | "round"
+            | "round_ties_to_even"
             | "trunc"
             | "fsqrt"
             | "fsin"
@@ -72,6 +73,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                     "ceil" => Op::Round(rustc_apfloat::Round::TowardPositive),
                     "floor" => Op::Round(rustc_apfloat::Round::TowardNegative),
                     "round" => Op::Round(rustc_apfloat::Round::NearestTiesToAway),
+                    "round_ties_to_even" => Op::Round(rustc_apfloat::Round::NearestTiesToEven),
                     "trunc" => Op::Round(rustc_apfloat::Round::TowardZero),
                     "ctlz" => Op::Numeric(sym::ctlz),
                     "ctpop" => Op::Numeric(sym::ctpop),