From 162bd4be978a7862a7cf5d8c8c4b69bec77b2c6f Mon Sep 17 00:00:00 2001
From: Ryan Houdek <Sonicadvance1@gmail.com>
Date: Mon, 4 May 2026 12:39:34 -0700
Subject: [PATCH] win32: Query DCZID_EL0 so clzero works

EL0 registers are readable without going through the registry, but we
were failing to populate this register, which was causing clzero to not
be supported.
---
 Source/Windows/Common/CPUFeatures.cpp | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/Source/Windows/Common/CPUFeatures.cpp b/Source/Windows/Common/CPUFeatures.cpp
index 0b9696dce..9860eb6e2 100644
--- a/Source/Windows/Common/CPUFeatures.cpp
+++ b/Source/Windows/Common/CPUFeatures.cpp
@@ -31,6 +31,14 @@ uint64_t ReadRegU64(HKEY Key, const char* Name) {
 } // namespace
 
 namespace FEX::Windows {
+#define GetSysReg(name, reg)                         \
+  static uint64_t Get_##name() {                     \
+    uint64_t Result {};                              \
+    __asm("mrs %[Res], " #reg : [Res] "=r"(Result)); \
+    return Result;                                   \
+  }
+GetSysReg(DCZID_EL0, DCZID_EL0);
+
 class CPUFeaturesFromRegistry final : public FEX::CPUFeatures {
 public:
   explicit CPUFeaturesFromRegistry(HKEY Key) {
@@ -43,6 +51,7 @@ public:
     ZFR0.SetReg(ReadRegU64(Key, "CP 4024"));
     MMFR1.SetReg(ReadRegU64(Key, "CP 4039"));
     ISAR2.SetReg(ReadRegU64(Key, "CP 4032"));
+    DCZID.SetReg(Get_DCZID_EL0());
     FillFeatureFlags();
   }
 };