Don't require strict equality when subnormals are flushed

Author: calebzulawski

crates/test_helpers/Cargo.toml

@@ -4,10 +4,9 @@ version = "0.1.0"
 edition = "2021"
 publish = false
 
-[dependencies.proptest]
-version = "0.10"
-default-features = false
-features = ["alloc"]
+[dependencies]
+float_eq = "1.0"
+proptest = { version = "0.10", default-features = false, features = ["alloc"] }
 
 [features]
 all_lane_counts = []

crates/test_helpers/src/biteq.rs

@@ -40,6 +40,8 @@ macro_rules! impl_float_biteq {
             fn biteq(&self, other: &Self) -> bool {
                 if self.is_nan() && other.is_nan() {
                     true // exact nan bits don't matter
+                } else if crate::flush_subnormals::<Self>() {
+                    self.to_bits() == other.to_bits() || float_eq::float_eq!(self, other, abs <= 2. * <$type>::EPSILON)
                 } else {
                     self.to_bits() == other.to_bits()
                 }

crates/test_helpers/src/lib.rs

@@ -6,6 +6,19 @@ pub mod wasm;
 #[macro_use]
 pub mod biteq;
 
+/// Indicates if subnormal floats are flushed to zero.
+pub fn flush_subnormals<T>() -> bool {
+    let is_f32 = core::mem::size_of::<T>() == 4;
+    let ppc_flush = is_f32
+        && cfg!(all(
+            target_arch = "powerpc64",
+            target_endian = "big",
+            not(target_feature = "vsx")
+        ));
+    let arm_flush = is_f32 && cfg!(all(target_arch = "arm", target_feature = "neon"));
+    ppc_flush || arm_flush
+}
+
 /// Specifies the default strategy for testing a type.
 ///
 /// This strategy should be what "makes sense" to test.