Add an xfail for recent ynf failures

This failed a couple of times recently in CI, once on i686 and once on
aarch64-apple:

    thread 'main' panicked at crates/libm-test/benches/random.rs:76:65:
    called `Result::unwrap()` on an `Err` value: ynf

    Caused by:
        0:
               input:    (681, 509.90924) (0x000002a9, 0x43fef462)
               expected: -3.2161271e38          0xff71f45b
               actual:   -inf                   0xff800000
        1: mismatched infinities

    thread 'main' panicked at crates/libm-test/benches/random.rs:76:65:
    called `Result::unwrap()` on an `Err` value: ynf

    Caused by:
        0:
               input:    (132, 50.46604) (0x00000084, 0x4249dd3a)
               expected: -3.3364996e38          0xff7b02a5
               actual:   -inf                   0xff800000
        1: mismatched infinities

Add a new override to account for this.

Author: tgross35

libm/crates/libm-test/src/precision.rs

@@ -4,6 +4,7 @@
 use core::f32;
 
 use CheckBasis::{Mpfr, Musl};
+use libm::support::CastFrom;
 use {BaseName as Bn, Identifier as Id};
 
 use crate::{BaseName, CheckBasis, CheckCtx, Float, Identifier, Int, TestResult};
@@ -524,7 +525,7 @@ impl MaybeOverride<(i32, f32)> for SpecialCase {
         ctx: &CheckCtx,
     ) -> Option<TestResult> {
         match (&ctx.basis, ctx.base_name) {
-            (Musl, _) => bessel_prec_dropoff(input, ulp, ctx),
+            (Musl, _) => bessel_prec_dropoff(input, actual, expected, ulp, ctx),
 
             // We return +0.0, MPFR returns -0.0
             (Mpfr, BaseName::Jn | BaseName::Yn)
@@ -554,7 +555,7 @@ impl MaybeOverride<(i32, f64)> for SpecialCase {
         ctx: &CheckCtx,
     ) -> Option<TestResult> {
         match (&ctx.basis, ctx.base_name) {
-            (Musl, _) => bessel_prec_dropoff(input, ulp, ctx),
+            (Musl, _) => bessel_prec_dropoff(input, actual, expected, ulp, ctx),
 
             // We return +0.0, MPFR returns -0.0
             (Mpfr, BaseName::Jn | BaseName::Yn)
@@ -569,8 +570,10 @@ impl MaybeOverride<(i32, f64)> for SpecialCase {
 }
 
 /// Our bessel functions blow up with large N values
-fn bessel_prec_dropoff<F: Float>(
-    input: (i32, F),
+fn bessel_prec_dropoff<F1: Float, F2: Float>(
+    input: (i32, F1),
+    actual: F2,
+    expected: F2,
     ulp: &mut u32,
     ctx: &CheckCtx,
 ) -> Option<TestResult> {
@@ -585,6 +588,17 @@ fn bessel_prec_dropoff<F: Float>(
         }
     }
 
+    // Values near infinity sometimes get cut off for us. `ynf(681, 509.90924) = -inf` but should
+    // be -3.2161271e38.
+    if ctx.fn_ident == Identifier::Ynf
+        && !expected.is_infinite()
+        && actual.is_infinite()
+        && (expected.abs().to_bits().abs_diff(actual.abs().to_bits())
+            < F2::Int::cast_from(1_000_000u32))
+    {
+        return XFAIL;
+    }
+
     None
 }