From 3e3d4c3499bad490f0de4ecf4d6c89ed34fa3f8a Mon Sep 17 00:00:00 2001
From: edgchen1 <18449977+edgchen1@users.noreply.github.com>
Date: Fri, 21 Nov 2025 10:07:24 -0800
Subject: [PATCH] Add fallback for ARM Windows fp16 detection.

---
 src/arm/windows/init.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/src/arm/windows/init.c b/src/arm/windows/init.c
index 5c0a5f39..a07fbe46 100644
--- a/src/arm/windows/init.c
+++ b/src/arm/windows/init.c
@@ -249,6 +249,14 @@ static void set_cpuinfo_isa_fields(void) {
 	// guarantee that, but it holds in practice.
 	cpuinfo_isa.rdm = dotprod;
 
+	// PF_ARM_V82_FP16_INSTRUCTIONS_AVAILABLE may not be available in older
+	// Windows versions. If fp16arith was not detected with
+	// IsProcessorFeaturePresent(PF_ARM_V82_FP16_INSTRUCTIONS_AVAILABLE), fall
+	// back to using the value of dotprod.
+	if (!cpuinfo_isa.fp16arith) {
+		cpuinfo_isa.fp16arith = dotprod;
+	}
+
 	/* Windows API reports all or nothing for cryptographic instructions. */
 	const bool crypto = IsProcessorFeaturePresent(PF_ARM_V8_CRYPTO_INSTRUCTIONS_AVAILABLE) != 0;
 	cpuinfo_isa.aes = crypto;