From dc0ba7836528b7d8720b868e331a378ceaf8fa95 Mon Sep 17 00:00:00 2001
From: Caleb Zulawski <caleb.zulawski@gmail.com>
Date: Fri, 21 Jul 2023 15:44:15 -0400
Subject: [PATCH] Don't require strict equality when subnormals are flushed

---
 crates/test_helpers/Cargo.toml   |  7 +++----
 crates/test_helpers/src/biteq.rs |  2 ++
 crates/test_helpers/src/lib.rs   | 13 +++++++++++++
 3 files changed, 18 insertions(+), 4 deletions(-)

diff --git a/crates/test_helpers/Cargo.toml b/crates/test_helpers/Cargo.toml
index 1d2bc8b519a..bd481db6bac 100644
--- a/crates/test_helpers/Cargo.toml
+++ b/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 = []
diff --git a/crates/test_helpers/src/biteq.rs b/crates/test_helpers/src/biteq.rs
index 7d91260d838..515eaf1c048 100644
--- a/crates/test_helpers/src/biteq.rs
+++ b/crates/test_helpers/src/biteq.rs
@@ -40,6 +40,8 @@ impl BitEq for $type {
             fn biteq(&self, other: &Self) -> bool {
                 if self.is_nan() && other.is_nan() {
                     true // exact nan bits don't matter
+                } else if crate::flush_subnormals::<Self>() {
+                    self.to_bits() == other.to_bits() || float_eq::float_eq!(self, other, abs <= 2. * <$type>::EPSILON)
                 } else {
                     self.to_bits() == other.to_bits()
                 }
diff --git a/crates/test_helpers/src/lib.rs b/crates/test_helpers/src/lib.rs
index b26cdc311a2..1b98bccf706 100644
--- a/crates/test_helpers/src/lib.rs
+++ b/crates/test_helpers/src/lib.rs
@@ -6,6 +6,19 @@
 #[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.