Rollup merge of rust-lang#136543 - RalfJung:round-ties-even, r=tgross35

intrinsics: unify rint, roundeven, nearbyint in a single round_ties_even intrinsic

LLVM has three intrinsics here that all do the same thing (when used in the default FP environment). There's no reason Rust needs to copy that historically-grown mess -- let's just have one intrinsic and leave it up to the LLVM backend to decide how to lower that.

Suggested by `@hanna-kruppe` in rust-lang#136459; Cc `@tgross35`

try-job: test-various

Author: tgross35

src/intrinsics/mod.rs

@@ -340,14 +340,10 @@ fn codegen_float_intrinsic_call<'tcx>(
         sym::ceilf64 => ("ceil", 1, fx.tcx.types.f64, types::F64),
         sym::truncf32 => ("truncf", 1, fx.tcx.types.f32, types::F32),
         sym::truncf64 => ("trunc", 1, fx.tcx.types.f64, types::F64),
-        sym::rintf32 => ("rintf", 1, fx.tcx.types.f32, types::F32),
-        sym::rintf64 => ("rint", 1, fx.tcx.types.f64, types::F64),
+        sym::round_ties_even_f32 => ("rintf", 1, fx.tcx.types.f32, types::F32),
+        sym::round_ties_even_f64 => ("rint", 1, fx.tcx.types.f64, types::F64),
         sym::roundf32 => ("roundf", 1, fx.tcx.types.f32, types::F32),
         sym::roundf64 => ("round", 1, fx.tcx.types.f64, types::F64),
-        sym::roundevenf32 => ("roundevenf", 1, fx.tcx.types.f32, types::F32),
-        sym::roundevenf64 => ("roundeven", 1, fx.tcx.types.f64, types::F64),
-        sym::nearbyintf32 => ("nearbyintf", 1, fx.tcx.types.f32, types::F32),
-        sym::nearbyintf64 => ("nearbyint", 1, fx.tcx.types.f64, types::F64),
         sym::sinf32 => ("sinf", 1, fx.tcx.types.f32, types::F32),
         sym::sinf64 => ("sin", 1, fx.tcx.types.f64, types::F64),
         sym::cosf32 => ("cosf", 1, fx.tcx.types.f32, types::F32),
@@ -399,16 +395,18 @@ fn codegen_float_intrinsic_call<'tcx>(
         | sym::ceilf64
         | sym::truncf32
         | sym::truncf64
-        | sym::nearbyintf32
-        | sym::nearbyintf64
+        | sym::round_ties_even_f32
+        | sym::round_ties_even_f64
         | sym::sqrtf32
         | sym::sqrtf64 => {
             let val = match intrinsic {
                 sym::fabsf32 | sym::fabsf64 => fx.bcx.ins().fabs(args[0]),
                 sym::floorf32 | sym::floorf64 => fx.bcx.ins().floor(args[0]),
                 sym::ceilf32 | sym::ceilf64 => fx.bcx.ins().ceil(args[0]),
                 sym::truncf32 | sym::truncf64 => fx.bcx.ins().trunc(args[0]),
-                sym::nearbyintf32 | sym::nearbyintf64 => fx.bcx.ins().nearest(args[0]),
+                sym::round_ties_even_f32 | sym::round_ties_even_f64 => {
+                    fx.bcx.ins().nearest(args[0])
+                }
                 sym::sqrtf32 | sym::sqrtf64 => fx.bcx.ins().sqrt(args[0]),
                 _ => unreachable!(),
             };