From aa06e90e982a0b2c69ec0345104d78d6cf823d48 Mon Sep 17 00:00:00 2001
From: Trevor Gross <tmgross@umich.edu>
Date: Sat, 1 Mar 2025 19:32:06 +0000
Subject: [PATCH] Disable `f16` on AArch64 without the `neon` feature

There is an LLVM regression that breaks some `f16`-related code when
`fp-armv8` is disabled [1]. Since Rust ties that feature to `neon`,
disable `f16` if `neon` is not available.

[1]: https://github.com/llvm/llvm-project/issues/129394
---
 configure.rs | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/configure.rs b/configure.rs
index ff52e88da..2bb0f8383 100644
--- a/configure.rs
+++ b/configure.rs
@@ -71,6 +71,8 @@ pub fn configure_f16_f128(target: &Target) {
     let f16_enabled = match target.arch.as_str() {
         // Unsupported <https://github.com/llvm/llvm-project/issues/94434>
         "arm64ec" => false,
+        // Crash in LLVM20 <https://github.com/llvm/llvm-project/issues/129394>
+        "aarch64" if !target.features.iter().any(|f| f == "neon") => false,
         // Selection failure <https://github.com/llvm/llvm-project/issues/50374>
         "s390x" => false,
         // Infinite recursion <https://github.com/llvm/llvm-project/issues/97981>