From 756002eef89d260672208d49386d2cb424581b86 Mon Sep 17 00:00:00 2001
From: Billy Laws <blaws05@gmail.com>
Date: Tue, 9 Sep 2025 19:09:31 +0100
Subject: [PATCH] unittests: Add test for x87 mode switches wrongly flushing
 NZCV

---
 unittests/ASM/FEX_bugs/X87MMXNZCV.asm | 13 +++++++++++++
 1 file changed, 13 insertions(+)
 create mode 100644 unittests/ASM/FEX_bugs/X87MMXNZCV.asm

diff --git a/unittests/ASM/FEX_bugs/X87MMXNZCV.asm b/unittests/ASM/FEX_bugs/X87MMXNZCV.asm
new file mode 100644
index 000000000..ce34ab007
--- /dev/null
+++ b/unittests/ASM/FEX_bugs/X87MMXNZCV.asm
@@ -0,0 +1,13 @@
+%ifdef CONFIG
+{
+  "RegData": {},
+  "Env": { "FEX_X87REDUCEDPRECISION" : "1" }
+}
+%endif
+
+; FEX had a bug where a mmx->x87 switch would flush the saved NZCV value used for ftst, causing a crash in RA
+
+movq mm0, mm1 ; enters mmx state
+ftst ; enters x87 state
+
+hlt