From a09b65f4b251db6d5ee7f285d74808b08d4940d5 Mon Sep 17 00:00:00 2001
From: "Jae H. Yoo" <jaeyoo@google.com>
Date: Mon, 23 Dec 2024 14:35:00 -0800
Subject: [PATCH] PR #19096: Add F4E2M1FN and F8E8M0FNU types

Imported from GitHub PR https://github.com/openxla/xla/pull/19096

This PR adds F4E2M1FN primitive type (4-bit float with 2 bits exponent and 1 bit mantissa), F8E8M0FNU primitive type (8-bit float with 8 bits exponent, no mantissa and no sign) and enables loads/stores in the same way S4/U4 type is implemented.

This will enable using microscaling (MX) formats ([RFC](https://github.com/openxla/xla/discussions/18085)), such as MXFP4.

```c...

PiperOrigin-RevId: 709153611
---
 ml_dtypes/include/mxfloat.h | 1 +
 1 file changed, 1 insertion(+)

diff --git a/ml_dtypes/include/mxfloat.h b/ml_dtypes/include/mxfloat.h
index 6bdeea6a..252e8351 100644
--- a/ml_dtypes/include/mxfloat.h
+++ b/ml_dtypes/include/mxfloat.h
@@ -339,6 +339,7 @@ namespace Eigen {
 namespace numext {
 
 #define MXFLOAT_EIGEN_SIGNBIT_IMPL(Type)                              \
+  template <>                                                         \
   EIGEN_DEVICE_FUNC EIGEN_ALWAYS_INLINE Type signbit(const Type& x) { \
     int8_t t = bit_cast<int8_t, Type>(x) << (8 - Type::kBits);        \
     return bit_cast<Type, int8_t>(t >> 7);                            \